polarimeter experiment graph

updated Friday, April 01, 2016

Polarimeter

Most physical properties of enantiomers i.e., melting point, boiling point, refractive index, etc. are identical. However, they differ in a property called optical activity, in which a sample rotates the plane of polarization of a polarized light beam passing through. This effect was first discovered in 1808 by E.L. Malus (1775-1812), who passed light through reflective glass surfaces. Four years later, J.B. Biot (1774-1862) found that the extent of rotation of the light depends on the thickness of the quartz plates that he used. He also discovered that other compounds i.e., turpentine and sucrose solutions were capable of rotating the light. He attributed this "optical activity" to certain features in their molecular structure (asymmetry). Based on his research, he designed one of the first polariscopes , and formulated the basic quantitative laws of polarimetry. In 1850, Wilhelmy used polarimetry to study the reaction rate of the hydrolysis of sucrose. In 1874, van't Hoff proposed that a tetrahedral environment of the carbon atom could explain the phenomenon of optical activity. Today, polarimetry is used routinely in quality and process control in the pharmaceutical industry, the flavor, fragrance and essential oil industry, the food industry, and the chemical industry. The optical purity of the product can be determined by measuring the specific rotation of compounds like amino acids, antibiotics, steroids, vitamins, lemon oil, various sugars, and polymers and comparing them with the reference value (if the specific rotation of the pure enantiomer is known).

How does it work? Normal monochromatic light contains light that possesses oscillations of the electrical field in all possible planes perpendicular to the direction of propagation. When light is passed through a polarizer (i.e., Nicol prism, Polaroid film) only light oscillating in one plane will leave the polarizer ("picket fence model"). This linear polarized light can be described as a superposition of two counter-rotating components, which propagate with different velocities in an optical active medium. If one component interacts stronger than the other with a chiral molecule, it will slow down and therefore arrive later at the observer. The result is that the plane of the light appears to be rotated because the two vectors are not canceling each other anymore due to the phase shift.

In a polarimeter (figure 2), plane-polarized light is introduced to a tube (typically 10 cm in length, figure 3) containing a solution with the substance to be measured. If the substance is optical inactive, the plane of the polarized light will not change in orientation and the observer will read an angle of [ α ] = 0 o . If the compound in the polarimetry cell was optical active, the plane of the light would be rotated on its way through the tube. The observed rotation is a result of the different components of the plane polarized light interacting differently with the chiral center. In order to observe the maximum brightness, the observer (person or instrument) will have to rotate the axis of the analyzer back, either clockwise or counterclockwise direction depending on the nature of the compound. For clockwise direction, the rotation (in degrees) is defined as positive ("+") and called dextrorotatory (from the Latin: dexter=right). In contrast, the counterclockwise direction is defined as negative ("-") and called levorotatory (from the Latin laevus=left). Unfortunately, there is no direct correlation between the configuration [( D/L ) in Rosanoff, ( R/S ) in Cahn-Ingold-Prelog nomenclature] of an enantiomer and the direction [(+) or (-)] in which they rotate plane-polarized light. This means that the R-enantiomer can exhibit a positive or negative value for the optical rotation depending on the compound. In some cases, the solvent has an impact on the magnitude and the sign as well i.e.,( S )-lactic acid exhibits an optical rotation of [α]= +3.9 o in water and [α]= +13.7 o using 2 M sodium hydroxide solution as solvent because the observer looks at a different species (lactate). The observed specific rotation [ α ] obs depends on the length of the tube, the wavelength that it is used for the acquisition, the concentration of the optical active compound (enantiomer), and to a certain degree on the temperature as well. However, the temperature effect is very difficult to specify since it differs for each compound. For instance, the [ α ] -value for α-pinene only slightly increases in the range from 0 o C to 100 o C (at λ=589.3 nm), while it is almost cut in half for ß-pinene. These two compounds only differ by the position of the alkene function. Generally the following equation is used to calculate the specific optical rotation from experimental data:

α obs = observed optical rotation c = the concentration of the solution in grams per milliliter l = the length of the tube in decimeters (1 dm=10 cm)

Example 1 : A student obtained the following specific optical rotation from his measurement.

This notation means that the measurement was conducted at 25 o C using the D-line of the sodium lamp (λ=589.3 nm). A sample containing 1.00 g/mL of the compound in a 1 dm tube exhibits an optical rotation of 3.5 o in clockwise direction. Note that the instrument used in Chem 30BL and Chem 30CL can provide the specific optical rotation, which already corrects the optical rotation for the cell dimensions and the concentration. The optical rotation is raw data, which does not include these corrections. It is very important to pay attention which mode was used to acquire the data! As mentioned earlier, polarimetry can be used to determine optical purity of enantiomers.

Example 2: The observed specific optical rotation of a compound is [α] = +7.00 o . The specific optical rotation for the pure enantiomer is .

The sample consists of 75 % of the racemic form (=equimolar mixture of both enantiomers, α=0 o ) and an excess of 25 % of the enantiomer in question (62.5 % and 37.5 %). The instrument used below allows you to calculate the specific rotation, if you know the concentration of the solution. The cell used for the measurement has a pathlength of 10.0 cm.

Actual polarimeter used in the lab (Autopol IV) located in YH 6104

Polarimetry cell (5 cm stainless steel cell shown here)

Practical Aspects The cell has to be handled carefully since it costs more than $1000 to manufacture. It has to be cleaned thoroughly after the measurement was performed and is returned to the teaching assistant or instructor. Special attention should be given to the inlets that have been broken off several times already due to negligence on the student’s part! 1. The instrument has to warm up for at least 10-15 minutes, if it is not already turned on. The switch is located in the back of the instrument. The proper wavelength is chosen. 2. A solution with a known concentration (~0.5-3 %) of the compound in the proper solvent is prepared. 3. The polarimetry cell is filled with the solvent. After filling the cell, the path through the cell should be clear (If the path is not clear, the air bubbles in the path have to be removed prior to the measurement). The cell is placed on the rails inside the instrument, all the way on either the right or the left side. 4. The " Zero button " is pressed to zero the instrument. The screen should show 0.000 and not fluctuate too much. If this is not the case, make sure that the light can pass through. If this does not solve the problem, inform the teaching assistant or instructor about this problem immediately. 5. Then, the solvent is removed and the cell is dried. The solution of the compound is filled into the dry polarimeter cell making sure that the entire inner part is filled without any air bubbles or particulate matter. 6. The "I" button on the keypad is pressed and specific rotation is selected. 7. The proper cell dimension is selected: 100 mm (the cell provided is 100.0 mm=1 dm long) 8. Next, the proper concentration in % is entered (=the actual concentration of your solution and not the one recommended since they will most likely differ slightly!) 9. The reading on the display (=specific optical rotation) is recorded including the sign. (The experimenter has to research the literature data before performing the measurement in order to see if he is in the correct ballpark!). 10. The cell is taken out, cleaned thoroughly with the solvent used for the measurement and returned it to your teaching assistant or instructor. If the student is the last one to perform a measurement for the day, the instrument has to be turned off as well. 11. The sample from the optical rotation measurement can be recovered after the measurement if needed by removing the solvent i.e., Jacobsen ligand. 12. It is entirely unacceptable that the student locks up the cells somewhere, where they are not available to others because all the students in the course use the polarimetry cells. Doing so will result is a significant penalty for the student at fault.

Links: http://rudolphresearch.com/products/polarimeters

Polarimetry Experiments

Which soda do you prefer.

Students build and use a home-made polarimeter to perform a variety of experiments including identifying and measuring the concentration of sweeteners in soda. The intended audience grade level is 10th- 12th grade Chemistry classes.

This activity was developed by Kevin Amundson through the MRSEC Research Experience for Teachers (RET) program in collaboration with Nicholas Kearns (RET Mentor) and Dr. Martin Zanni (RET Host Lab, University of Wisconsin-Madison), with additional help from David Gagnon and Dr. Anne Lynn Gillian-Daniel (MRSEC), Dr. Nelson Cardona Martinez (SusWEF Director, University of Puerto Rico-Mayaguez), Christopher Gillette, Dale Vajko and Alycia Riehl (RETs at UW-Madison), Kathia Rodriguez and Samirah Mercado Feliciano (RETs at UPRM), and Dr. Tom McDonough (Zanni lab).

Light & Polarization Activities

• Creating Art with Polarized Light More
• Polarization of Light Activity More
• Polarimetry Experiments More

Activity Time:

• Building the polarimeter (30 minutes)
• 2 hour prep time to gather materials and equipment
• 7 Experiments (2, 90 minutes blocks or 4,  45 minute class periods)

Learning Objectives:

• Students will understand that light interacts with matter.
• Students will understand that light can be polarized and that plane polarized light is rotated by chiral molecules.
• Students will use polarimetry to determine the identity and/or concentration of an unknown solution.

Engineering Principles Addressed:

• Practice 1: Asking Questions and Defining Problems
• Practice 2: Developing and Using Models
• Practice 4: Analyzing and Interpreting Data
• Practice 5: Using Mathematics and Computational Thinking

Activity Materials

• PVC pipe (3/4″ diameter, 30″ length holds approximately 200 mL of solution)

• Cloth to cover source

• Polarizing film sheets (cut two squares about 1”X1”) $9.90
• Ring clamps
• Printable dial
• Distilled water
• Meter stick
• Epoxy glue (for use on PVC pipe)
• Vernier light sensor (optional) $55
• Vernier polarimeter (optional) $499
• Cane sugar (grocery store)
• Other sugars such as galactose, mannose, etc.
• D(-) and L(+) Tartaric Acid

Activity Instructions

This is an accordion element with a series of buttons that open and close related content panels.

Building the Polarimeter

• Cut the PVC pipe to desired length (30″ PVC holds about 200 mL of solution).

• Each line represents 22.5° when wrapped around the tube. Label each line successively starting at 0°, 22.5°, 45°, 67.5°…..etc. until 360°. You should laminate the template to prevent it from getting wet.

Light is an electromagnetic wave. Light from the sun or from a light bulb is said to be unpolarized because the electric and magnetic fields in the wave oscillate at right angles to each other and randomly in any direction in space. If the light passes through a polarized film, say through the lens of polarized sunglasses, only light with a specific orientation is allowed to pass. This is because conductive polymer chains in polarized lenses are all aligned in one direction.

Chiral substances are carbon based compounds which contain four different substituents (a substituent is something bonded to the carbon). A molecule of such a substance will have another version of itself with the same chemical formula but that is nonsuperimposable. Such molecules are called enantiomers of each other. For example, a pair of gloves are nonsuperimposable…in other words there is no way to rotate the right and left hand gloves such that they can be laid on top of each other and look the same.

A pair of socks, on the other hand, are superimposable because you can rotate the socks such that they can be paired together. We say that gloves have a “right or left-handedness,” whereas a pair of socks do not.

Chiral molecules likewise have a “right or left-handedness.” A molecule such as bromo-chloro-fluoromethane has two nonsuperimposable versions of each other and is chiral as shown below.

Chiral molecules have two enantiomers of each other which rotate plane polarized light at the same angle but in the opposite direction. We can therefore learn something about the structure and chirality of a molecule by observing how it interacts with plane polarized light. For example, dextrose was observed to rotate polarized light to the right or clockwise known as “dextrorotatory” thus the name dextrose. Levulose rotated the light to the left or counterclockwise known as “levorotatory” thus the name levulose. The molecules rotate light differently because as photons of light contact the molecule there are time delays between absorption and emission which causes the refraction of the light. The amount of refraction or bending also depends on light wavelength.

In fact most sugar molecules are chiral. If you look at the structure of a glucose molecule, you will notice the number 1 carbon (anomeric carbon) has four different substituents bonded to it and is therefore chiral. Such a carbon is known as a stereogenic center. Are there any other stereogenic centers in glucose?

The angle at which a molecule rotates polarized light is called its specific rotation or optical rotation, ? , and is an intrinsic property of the substance just like density or melting point. In sugars, each stereogenic center rotates light differently so the specific rotation of the molecule is the sum total. In fact, it is possible for the optical rotations of stereogenic centers to “undo” each other and have a chiral molecule which is optically inactive.

Specific rotation does depend on temperature and the wavelength of polarized light used and is usually reported at 20℃ and the bright line of sodium at wavelength 589 nm. The actual angle of rotation of polarized light also depends on the path length through which the light passes, the concentration of the substance, and the specific rotation of the substance. This is mathematically written as Biot’s Law:

In other words, the more concentrated the substance the more the light will rotate and the greater the observed optical rotation. Similarly, the longer path the light travels through the substance the more the light will rotate and the greater the observed optical rotation. Lastly, some molecules just rotate light more than others based on their structures.

The technique which is used to measure the optical rotation of substances is called polarimetry and the instrument used is called a polarimeter. A polarimeter basically consists of a light source, two polarizing filters, a chamber to put a sample, and a detector to measure the specific rotation.

Polarimetry is an important technique which can be used to identify substances (since the specific rotation is unique to the substance, like density), determine the concentration or purity of a sample using Biot’s law, or to measure the progress of a chemical reaction where the optical rotation changes over time. In the food industry, polarimetry can be used to determine the concentration and purity of sugars. In the drug industry, polarimetry can be used to determine the purity of amino acids, antibiotics, steroids, and vitamins because many of the molecules contained in these drugs are chiral.

A sort of worst case scenario happened with the morning sickness drug thalidomide in the 1960’s. One enantiomer of the drug was responsible for causing birth defects while the other enantiomer was inert until metabolized in the body. The usefulness of many drugs is dependent on using the correct enantiomer.

Using the polarimeter you built, you can now conduct many experiments in polarimetry.

Experiment #1: Optical Rotation and Light Intensity

Record the following in your lab notebook.

In this experiment, students will observe how light intensity changes as the polarized film on the polarimeter is rotated.

• Prepare 200 mL of a 30% sucrose solution and pour into the polarimeter tube.
• Clamp a Vernier Light sensor* so it is above the dial assembly.
• Record the light intensity and color of solution at even angle increments through 360°. I chose to record data every 10°.
• Prepare a graph of light intensity vs. angle.
• Describe any relationships observed between light intensity and angle as well as color of solution.

Experiment #2: Optical Rotation of Enantiomers

Each enantiomer of a chiral substance will rotate plane polarized light the same amount but in opposite directions. In this experiment, students will observe how two different enantiomers rotate polarized light.

• Choose two different optical enantiomers of a substance. For my experiment, I chose D(-) Tartaric Acid and L(+) Tartaric Acid, however the specific rotation is small so there is not a large change in angle. A substance with a higher specific rotation may work better.
• Prepare solutions of increasing concentrations for one of the enantiomers and pour into the polarimeter tube. Be sure to rinse the polarimeter tube with distilled water between solutions. Test each of these solutions in the polarimeter and measure the angles of minimum light intensity. For the remainder of the experiments, we will call this angle the observed optical rotation. This light intensity change can also be accompanied by color change from red to blue or vice versa especially for concentrated sugar solutions (Fig. 18). There will actually be two of these angles of minimum light intensity 180° apart. This is because the polarizing filters only allow light with the right orientation to pass through and block out light at angles to the film (see Fig. 10). You should get in the habit of recording both angles for each observation.
• Repeat procedure for step 2 for the other enantiomer.
• Prepare a graph of angle of optical rotation vs. concentration for each enantiomer.
• Explain any similarities and differences between the two graphs.

Experiment #3: Path Length and Biot’s Law

According to Biot’s Law, the observed optical rotation ⍺ depends on the path length through which light must pass through the sample. In this experiment, students will observe how observed optical rotation and path length are related.

• Prepare 200 mL of a 30% sucrose solution.
• Fill the polarimeter tube with the sucrose solution such that the path length increases by 0.5 dm in length for each observation. Record the angles of minimum light intensity. These will be the angles of optical rotation.
• Prepare a graph of angle of optical rotation vs. length. Since there will be two angles for each path length observation, choose one set to graph.
• Perform a line of best fit.
• Paste the graph in your lab notebook and describe the relationship between observed optical rotation and length. How well does the data follow Biot’s Law? What does the slope of the graph represent? Give units for the slope.

Experiment #4: Determining the Concentration of an Unknown Sugar Solution

In this experiment, students will determine the concentration of an unknown sugar solution prepared by the teacher. Students will prepare a calibration curve using observed optical rotation vs. concentration for a series of standard solutions. By measuring the observed optical rotation of the unknown and the line of best fit on the calibration curves, students can calculate the concentration of the unknown solution. This is similar to the Beer’s Law experiment often done in introductory chemistry.

• Prepare five 200 mL of standard sugar solutions ranging from 0.10 g/mL up to about 0.30 g/mL (10-30% solutions).
• The teacher will prepare an unknown sugar solution.
• Test each of these solutions in the polarimeter and measure the angles of minimum light intensity.
• Prepare a plot of observed angle of rotation vs. concentration in g/mL.
• Perform a linear fit and determine the equation of best fit.
• Obtain a sugar solution of unknown concentration from your instructor. Measure the angles of minimum light intensity and use the calibration plot to calculate the concentration of the unknown.
• Obtain the value of the unknown concentration from the instructor and calculate a percent error.
• Comment on sources of error and how they affect results.

Example: Angle of rotation for the unknown was found to be 315°. Calculate the concentration of the unknown.

Equation of best fit: y = 204x + 268

Note: the equation should have units of mL (milliliters)

Experiment #5: Identifying Sugars Using Polarimetry

In this experiment, students will prepare standard solutions of various sugar solutions. Using Biot’s Law, the specific rotation of the sugar can be calculated. The teacher will then give the students an unknown sugar solution and ask the students to identify it.

• Prepare five 200 mL of standard sugar solutions ranging from 0.10 g/mL up to about 0.30 g/mL (10-30% solutions). I used D(+) galactose, dextrose, D(-) fructose, and D(-) maltose.
• Pour each of these solutions in the polarimeter and measure the angles of minimum light intensity.
• Measure the length of the polarimeter tube. This length represents the distance light must travel through the sample and is called the path length.
• When making a linear plot of observed angle of rotation vs. concentration the slope of the line represents the product of the specific rotation of the sugar and the path length in dm according to Biot’s law. Since the path length is known from step 5, the specific rotation can be calculated and the sugar identified.
• Look up the literature value of the specific rotation and calculate a percent error. Comment on sources of error and how they affect results.

Experiment #6: Which soda do you prefer?

In the 1970’s, US manufacturers began using high fructose corn syrup to sweeten products previously sweetened by sugar (sucrose) due to the cheaper price of using corn instead of sugar. High fructose corn syrup is actually a misnomer given its composition in drinks such as soda is normally 55% fructose, 42% glucose, and 3% other ingredients. Over time there has grown a sort of backlash against the use of high fructose corn syrup (HFCS) with claims that the rise in the use of HFCS coincides with the rise in obesity levels. In response, sodas such as Blue Sky advertise all natural sugar with no added HFCS and can be found in the organic food sections in supermarkets. In addition, some people say they prefer the taste of foods sweetened with sucrose instead of HFCS. For example, some people seek out “Mexican soda” because sodas such as Coke are sweetened with cane sugar instead of HFCS in Mexico. “Kosher” soda sold in the US during the Jewish Passover is also sweetened with sucrose instead of HFCS.

Question . But how about you? Do you prefer the taste of soda sweetened with sugar or high fructose corn syrup or can you tell a difference? How can we test the labels on a soda to verify the sweetener used is the one advertised? In this experiment we will use Sprite flavored with sugar and compare it to Sprite flavored with high fructose corn syrup using an instrument called a polarimeter.

Taste test . The teacher will put out samples of sugar flavored Sprite and HFCS flavored Sprite in two cups. This will be conducted as a blind taste test so the teacher will not reveal which soda each cup contains until the end of the experiment. Record any observations of taste as well as any visual observations (i.e. can you see any difference between the two types of sodas?) below. At this point, keep all observations to yourself as to not bias or influence classmates.

Decide which soda you prefer or if you have no preference record below. Report the decision to your teacher. The teacher will keep a tally of the results to share with the class at the end of the experiment.

• 11.3% sucrose solution (use cane sugar as the source of sucrose)
• HFCS-55 solution (55% fructose, 42% glucose)
• Clamp the polarimeter tube so that it is on top of the light source.
• Pour distilled water into the polarimeter. Since water is not chiral it will serve as the control.
• Students should notice the intensity and/or color of the light chaning as the dial is rotated.
• Red is least intense, yellow is most intense. The optical rotation of light depends on its wavelength with red being rotated the least amount.
• Angles will vary but students should notice the angles are about 180° apart.
• Angles will vary but will also be 180° apart on 90° apart from the most intense angles.
• Empty the distilled water from the polarimeter tube and pour in a sucrose solution.
• Students should notice a different angle of rotation. I got 70° and 245°.
• Empty out the sucrose solution and rinse out the polarimeter tube and pour in the HFCS-55 solution.
• Students should notice another angle of rotation. I got 150° and 330°.
• Empty out the HFCS-55 solution and rinse out the polarimeter tube. Pour in the sample of Sprite you preferred. You will notice the Sprite is “flat” as the teacher degassed it. The CO2 bubbles do not affect the optical rotation but can make it difficult to see into the polarimeter. *Teachers can degas the Sprite by placing it on a magnetic stirrer and gently heating it until the carbonation is mostly gone.
• The Sprite sweetened with HFCS matched the HFCS-55 solution exactly. The Sprite sweetened with sucrose was different than pure sucrose and HFCS-55 at angles 100° and 285°. This is addressed in experiment #7.
• Answers will vary depending on the teacher’s choice.

• Use Biot’s Law to calculate the specific rotation for sucrose. How does this compare to the literature value?
• Biot’s Law is for a pure substance with one specific rotation. HFCS is a mixture of two substances glucose and fructose each with its own optical rotation. The optical rotation of a mixture depends on the specific rotation and mole fraction of each component in the mixture.
• -parallax error reading the dial -light is broad spectrum not just 589 nm of sodium -temperature may not be at 20℃ -polarimeter tube not rinsed out thoroughly -scratches on polarized film -solution not filled up to the same path length in the polarimeter tube each time -orientation of the polarimeter tube in bumped -solution contaminated -sucrose, glucose, or fructose may contain impurities
• Do some research. What are some of the controversies surrounding the use of high fructose corn syrup? What is your opinion? Explain.

It has been claimed HFCS can lead to the following health problems …. • Weight Gain. • Cancer. … • Increased Cholesterol Levels. … • Diabetes. … • High Blood Pressure. … • Heart Disease. … • Leaky Gut Syndrome. … • Increased Mercury Intake.

The general consensus is the health problems caused by HFCS are no different or worse than sucrose.

*According to Wikipedia, a 2011 study further backed up the idea that people enjoy sucrose (table sugar) more than HFCS. The study, conducted by Michigan State University, included a 99-member panel that evaluated yogurt sweetened with sucrose (table sugar), HFCS, and different varieties of honey for likeness. The results showed that, overall, the panel enjoyed the yogurt with sucrose (table sugar) added more than those that contained HFCS or honey. http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0307.2011.00694.x/abstract

Experiment #7: Problems with Mexican Soda

A problem we ran into was the Mexican Sprite with sugar in it did not exactly match the optical rotation of the cane sugar A little investigation on-line revealed even soda sweetened with cane sugar may actually contain HFCS once the consumer drinks it.

http://www.acsh.org/news/2016/04/08/why-cokes-cane-sugar-soda-may-seem-just-like-the-high-fructose-kind

This is because in the acidic conditions found in soda, the sucrose breaks down into glucose and fructose with almost 90% of the sucrose breaking down within 100 days. The decomposition can occur more rapidly if the soda is exposed to higher temperatures.

To determine the fructose content of the Mexican Sprite and how much of the original sucrose had broken down, a series of standard solutions of HFCS were prepared and a plot of angle of rotation vs. percent fructose was prepared.

• Prepare 200 mL of the solutions shown in Fig. 30.
• Prepare a plot of angle of rotation vs. percent fructose.
• Pour the Mexican Sprite into the polarimeter and measure its optical rotation. Use the calibration curve to calculate the percent fructose.
• Estimate the how long it has been since the soda was bottled.
• Do you think it false advertising for sodas to claim they are sweetened with 100% pure sugar? Explain your thinking.

The optical rotation of the Mexican Sprite was observed to be 100°. Using the calibration curve this corresponds to a percent fructose of 28%.

This means the Sprite was actually 28% fructose, 28% glucose, and only 44% sucrose. In other words, 56% of the sucrose had already decomposed meaning the soda was bottled roughly two months prior.

Citations & Links to More Information

High Fructose Corn Syrup What it is and What it Ain’t

Modified version of An Inexpensive Homemade Polarimeter

Build a Homemade Polarimeter

Sugar Identification Using Polarimetry

Understanding Polarimetry with Vernier

Experiments with Polarized Light

The Story of Mexican Coke is a lot More Complex than Hipsters Would Like to Admit

Why Coke’s Cane Sugar May Seem Just Like the High Fructose Kind

To measure the specific rotation of cane sugar using Polarimeter

• Enter the value of concentration of Sugar Solution in g/cc.
• Press the Submit Button.
• Enter the value of input Angle θ in degree.
• Enter the Length of the tube L in centimeter.
• Press “check” button.
• Similarly take 5 observations and enter the value of input angle & length in the table.
• Press “draw graph” button.
• Place the cursor on the graph to note the coordinates of two different points.
• Enter the value of ΔX and ΔY press “submit” button.
• Slope of the graph and specific rotation will be calculated.
• Repeat the experiment by changing the concentration of Sugar Solution.

Remember Me

Shop Experiment Understanding Polarimetry Experiments​

Understanding polarimetry.

Experiment #6 from Organic Chemistry with Vernier

Introduction

A polarimeter is a device that measures the rotation of linearly polarized light by an optically active sample. This is of interest to organic chemists because it enables differentiation between optically active stereoisomers, i.e., enantiomers. Enantiomers, chiral molecules, are molecules which lack an internal plane of symmetry and have a non-superimosable mirror image. One way to tell these molecules apart is to use polarimetry. Polarimetry is also helpful for biological applications because amino acids, nucleic acids, carbohydrates, and lipids are all optically active. Determination of the optical activity of a compound using polarimetry allows the user to determine various characteristics, including the identity, of the specific chemical compound being investigated.

Incident non-polarized light is transmitted through a fixed polarizer that only allows a certain orientation of light into the sample. The sample then rotates the light at a unique angle. As the analyzer is turned, the rotated light is maximally transmitted at that unique angle, allowing the user to determine properties of the sample. A (+) enantiomer rotates the plane of linearly polarized light clockwise, dextro, as seen by the detector. A (–) enantiomer rotates the plane counter-clockwise, levo.

A compound will consistently have the same specific rotation under identical experimental conditions. To determine the specific rotation of the sample, use Biot’s law:

where α is the observed optical rotation in units of degrees, [α] is the specific rotation in units of degrees (the formal unit for specific rotation is degrees dm-1 mL g-1, but scientific literature uses just degrees), ℓ is the length of the cell in units of dm, and c is the sample concentration in units of grams per milliliter.

In this experiment, you will

• Become familiar with the use of the Polarimeter.
• Experience how sample path length and concentration affect observed rotation.
• Calculate the specific rotation for a known sugar sample using Biot’s law.

Sensors and Equipment

This experiment features the following sensors and equipment. Additional equipment may be required.

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This experiment is #6 of Organic Chemistry with Vernier . The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.

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• 00:00 Overview
• 00:49 Principles of Polarimetry
• 03:51 Initialization of the Polarimeter
• 04:24 Calibration and Measurement
• 05:23 Applications
• 06:52 Summary

Polarimeter

Source: Vy M. Dong and Diane Le, Department of Chemistry, University of California, Irvine, CA

This experiment will demonstrate the use of a polarimeter, which is an instrument used to determine the optical rotation of a sample. Optical rotation is the degree to which a sample will rotate polarized light. Optically active samples will rotate the plane of light clockwise (dextrorotatory), designated as d or (+), or counterclockwise (levorotatory), designated as l or (−).

The polarimeter is a quantitative method used to determine the optical rotation of a chiral molecule. A molecule is considered chiral if it is non-superimposable on its mirror image. More specifically, chiral molecules that are mirror images of one another are called enantiomers ( Figure 2 ). Enantiomers have the same physical properties such as melting point, boiling point, and solubility; however, they differ in the degree to which they polarize light. A pure ( R )-enantiomer of a compound will rotate light in an equal but opposite direction as its ( S )-enantiomer. If a mixture of compounds is racemic, meaning it contains an equal mixture of ( R )- and ( S )-enantiomers, then its optical rotation will be zero. Thus, polarimetry is a way to characterize and distinguish the identity between a pair of enantiomers.

A polarimeter works by shining monochromatic light through a polarizer, which generates a beam of linearly polarized light. The polarized light will then rotate after it passes through a polarimetry cell containing the sample. An analyzer will then rotate counterclockwise or clockwise to allow the light to pass through and reach the detector ( Figure 1 ). Using this instrument, the specific rotation of light can be calculated, which relates the observed optical rotation with the concentration of solution and cell pathlength. The specific rotation is defined by the following equation:

where α obs is the observed optical rotation value given by the polarimeter, l is the cell pathlength in dm, and c is the concentration of the solution in g/mL.

Moreover, the enantiomeric excess ( ee ), which is a measurement of how much of one enantiomer exists over the other in a mixture, can be determined by using specific rotation. The calculation of ee is given by the following equation:

where α mixture is the specific rotation of the mixture of enantiomers and α pure is the specific rotation of the pure enantiomer. Generally, if two out of three values in the equation are known ( i.e. , ee and α mixture ) then the third value (α pure ) can be calculated.

Figure 1. Concept behind the polarimeter.

Figure 2. Chiral molecules that are mirror images of one another are enantiomers.

1. Preparing the Polarimeter

• Turn on instrument and let it warm up for 10 min.
• Make sure instrument is set to "optical rotation" mode.
• Prepare a blank sample in the polarimeter cell (1.5 mL total sample volume, 1 dm in length) containing only CHCl 3 . Make sure there are no air bubbles present.
• Place the blank cell in the holder and press "zero."

2. Preparation of Analyte Sample

• Prepare a stock solution of 10-15 mg of the chiral analyte in 1.5 mL CHCl 3 . Note the exact amount of compound used.

3. Measuring Optical Rotation

• Fill the cell with 1.5 mL of the prepared stock solution containing the sample.
• Place the cell in the holder and press "measure." The machine readout will give the optical rotation value. Remember to record the temperature as well.

4. Calculation of Specific Rotation

Polarimeters are widely used in organic and analytical chemistry to assess the purity of a chemical product and investigate its properties.

Polarimeters detect the presence of enantiomers: mirror-image variants of a compound that may have wildly divergent biological activities. Distinguishing between enantiomers is critical in many applications, including pharmaceuticals, since one enantiomer is typically responsible for biological effects while the other is usually inert, less active, or, as in the case of the drug thalidomide, harmful.

This video will illustrate the principles of polarimetry, demonstrate setup and operation of a polarimeter, and discuss some applications.

Polarimetry is useful for studying organic compounds containing stereocenters.

Stereocenters are carbon atoms that are bonded to four different atoms or groups. In this example, the carbon atom is bonded to hydrogen, fluorine, chlorine, and bromine, forming bromo-chloro-fluoro-methane.

Compounds containing stereocenters are called “chiral,” meaning they exist as mirror-image isomers: non-equivalent physical structures that cannot be rotated or oriented to superimpose on each other. The mirror-image isomers are called “enantiomers,” and they have identical physical properties, with one exception related to optics.

In optics, non-laser light sources emit light waves that oscillate in a variety of planes. Such light waves are called “unpolarized.” However, certain materials are capable of filtering light waves based on their plane of oscillation, transmitting only those light waves that oscillate in one specific plane while absorbing those oscillating in other planes. The transmitted light has been “plane polarized.”

Enantiomers have different effects on plane polarized light. If they are struck by plane polarized light, one enantiomer will rotate the plane of oscillation clockwise, while the other will rotate the plane of oscillation by an equal angle counterclockwise. The former is called the “dextrorotatory” enantiomer, and its name prefixed with a plus sign. The latter is called the “levorotatory” enantiomer, and its name is prefixed with a minus sign. The ratio of rotation angle to concentration is unique for each compound, and is called “specific optical rotation.”

A polarimeter detects whether one or both enantiomers are present in a sample. It consists of a light source, a polarizer, a sample cell, a detector, and an analyzer. The light source emits light waves that are unpolarized but monochromatic, meaning they have the same wavelength. The light waves then encounter the polarizer, which transmits only those oscillating in one specific plane, yielding a plane-polarized beam. The plane-polarized light then interacts with the sample in the sample cell.

If the sample contains only one enantiomer of the chiral compound, the polarized light will rotate. The angle is called the “optical rotation,” and it depends on the specific optical rotation of the compound, its concentration, and the length of the sample cell. If, on the other hand, both enantiomers are present in equal concentrations, they form a “racemic mixture” that cannot rotate polarized light. Finally, if one enantiomer is present in greater concentration than the other, an “enantiomeric excess” results, and the plane of oscillation will be rotated in proportion to the excess.

After the polarized light passes through the sample, it is detected. The analyzer measures the optical rotation.

Now that you’ve seen the principles, let’s examine a typical operating procedure.

The first step to using the polarimeter is zeroing the instrument.

First, turn on the polarimeter and let it warm up for 10 min.

Set the instrument to optical rotation mode.

The sample cell is typically a tube 1 dm long with a volume of 1.5 mL. Prepare the cell by cleaning with acetone and lab wipes.

Gently place the empty sample cell into the holder and press “zero.” This establishes the baseline.

Next, calibrate the polarimeter using a pure sample of the chiral compound under investigation.

In this example, the dextrorotatory enantiomer of carvone is used. Pipette 1.5 mL into the sample cell. Insert the cell into the holder, and press “measure.” The optical rotation is displayed. Dividing the measured optical rotation by concentration, or density for pure substances, and cell length yields the specific optical rotation of the compound.

The specific optical rotation of a purified unknown can be found similarly, by dissolving the unknown in an optically inactive solvent and measuring the optical rotation. The specific optical rotation of the compound is then determined by dividing by the concentration. The compound is then identified by comparing its specific optical rotation to literature values.

Now that you know how to perform measurements, we will explore some practical applications.

In the pharmaceutical industry, polarimetry is used for quality control. For instance, it has been used to measure the concentration and enantiomeric purity of ephedrine in commercial cough suppressants. Even in the presence of other ingredients, this technique can be used to determine the ephedrine concentration to within 1%.

In the food and beverage industries, sucrose concentrations and purities are monitored continuously with specially-designed flow polarimeters. Sucrose, one of the most common ingredients in foods, has a specific optical rotation of 66.5 degrees. By dividing the optical rotation of the sucrose stream by the specific optical rotation of sucrose, the concentration can be determined. Fluctuations in the optical rotation would indicate fluctuations in sucrose concentration.

Polarimetry has also been used to study reaction kinetics, including kinetics for enzyme systems such as the penicillin-penicillinase system. In this case, the sample cell contains both enzyme and substrate, and the optical rotation is measured with respect to time. The change in optical rotation is directly proportional to the change in substrate concentration. This not only reveals the reaction kinetics, but also permits simultaneous determination of enzyme and substrate concentrations in future assays.

You’ve just watched JoVE’s introduction to the polarimeter. You should now understand its principles of operation, the steps for setup and measurement, and some of its applications. Thanks for watching!

Representative results for the measurement and calculation of specific rotation for Procedures 1-4.

Table 1. Representative results for procedures 1 – 4.

Applications and Summary

In this experiment, we have demonstrated the principles behind the polarimeter and how to measure and calculate the specific rotation of an optically active compound.

The polarimeter is an important instrument in the fine-chemical and pharmaceutical industries to assess the identity, purity, and quality of a compound. It is specifically used for the measurement of optical rotation of chiral compounds, which can be used to distinguish the identity of two enantiomers by confirming whether it is an ( R ) or ( S ) compound. This is especially important in pharmaceutical drug synthesis because one enantiomer is generally responsible for the biological effects while the other enantiomer is often less active and can have adverse effects. In addition, the polarimeter can be implemented to determine the unknown ee of a sample. If the ee value is unknown, this can be calculated using the polarimeter by determining the specific rotation.

Specific Rotation Equation vs Optical Rotation

Specific rotation equation vs. optical rotation – what’s the difference, by angelo depalma, phd, polarimetry using polarimeters measure the degree of rotation of polarized light as it passes through an optically active material..

If you’re learning about Polarimetry you might come across  the terms specific rotation and optical rotation. What is the specific rotation equation and optical rotation? What are the differences between the two?  We will cover this below.

How Polarimetry Works

Normal monochromatic light emerging from a light bulb consists of an infinite number of oscillating waves in all possible planes perpendicular to the line of propagation. A polarizer is a special type of slit or opening that allows light propagating on one plane to pass through. When this light interacts with a chiral substance it speeds up or slows down, the net effect being an apparent rotation in the plane of polarized light.

In this 3D projection of 2-butanol the structure on the left has the R- configuration, while its mirror image on the right is the S- isomer according to the Cahn-Ingold-Prelog rules. However, the structure on the left rotates plane-polarized light counter-clockwise. It is designated as (-) or l , while the S -isomer is (+) or l . If this were not confusing enough, biochemistry employs a third nomenclature that employs the small capital letters D and L. This system is related to R and S but does not strictly follow Cahn-Ingold-Prelog or directly relate to optical rotation. It is therefore beyond the scope of this article. Here we are concerned only with d and l or (+) and (-), respectively.

Specific Rotation Equation

Specific rotation equation, [α], is a fundamental property of chiral substances that is expressed as the angle to which the material causes polarized light to rotate at a particular temperature, wavelength, and concentration. The term for specific rotation equation is given by

where T is the measurement temperature, λ is the wavelength of light employed (normally the sodium D-line, or 589 nm), α is the observed rotation. l is the path length, and c is the concentration in grams per milliliter (for pure substances the density) or grams per 100 milliliters. The solvent (often ethanol, methanol, DSMO, acetone, water, etc.) is also specified. Specific rotation may also be expressed as degrees per mole of the substance where the conditions of measurement (i.e. solvent, light source, and path length) are also specified. Use of various wavelengths in Polarimetry to control sensitivity Use of wavelengths lower than 589 nm, which are available with the mercury and deuterium lamp lines isolated through filters to provide wavelengths of 578, 546, 436, 405, and 365nm, may sometimes provide advantages in sensitivity. Generally, the observed optical rotation at 436nm is approximately double and at 365nm about three times that at 589nm. Polarimeter Light Sources It is now common practice to use other light sources such as xenon or tungsten halogen. With appropriate filters, these light sources offer advantages of cost, long life, and broad wavelength emission range over traditional light sources. Polarimeters measure the observed rotation designated by the Greek lower case letter α. From this value, and knowledge of the specific rotation, one can easily calculate the concentrations of both isomers of a pure substance. For example it is possible to determine the conversion of an achiral material to a chiral substance, or the relative concentrations of optical isomers, known as enantiomeric excess . Let’s say a chemist was attempting to manufacture pure (-)-2-butanol, which has a specific rotation of -13.5º under standard measurement conditions. But when the liquid product is placed into a polarimeter cell as a neat solution the observed rotation is only -4.5º, or one-third the specific rotation. This tells us that one third of the 2-butanol in the sample consisted of the l or (-) isomer, and the remaining two-thirds consists of racemate (equal quantities of (+) and (-). Therefore two-thirds of the butanol is (-)-2-butanol, and one-third is (+)-2-butanol. Observed Rotations More relevant to industry are observed rotations of mixtures. For example of food ingredients, perfumes, flavorings, chemicals, pure or formulated pharmaceuticals – virtually any industry that produces or uses chiral organic molecules in pure or diluted form. In these situations, polarimetry provides a rapid, reliable, quality check. This eliminates the need of using conventional analysis like liquid chromatography. This can take an hour to do what the polarimeter accomplishes in minutes. Polarimetry provides an additional check on a pure substance before it is added to an expensive batch. This determines the ingredient’s concentration or purity. For example a 25% glucose syrup will have an observed rotation that is five-sixths that of a 30% syrup. Similarly the optical rotation of a mixed-component ingredient, intermediate, or finished product will have a characteristic optical rotation that may arise from the presence of several chiral compounds. Once a standard is determined for the composite observed rotation, one can establish quality criteria based on optical rotation. In these situations the polarimeter measurement becomes a type of screen for further testing. This determines which ingredient is out of specification. Polarimetry Conclusion In conclusion, Optical rotation is an indispensable quality and identity assay for a wide range of critical industries. Research organic chemists use polarimetry to test the effectiveness of catalysts and asymmetric synthetic processes. Food, drug, as well as flavors industries utilize polarimetry as a quality attribute for raw ingredients and finished products. Polarimeters in today’s Labs Although polarimetry is a mature technique, today’s instrumentation provide features and benefits that purely manual-optical systems do not. Busy labs process multiple samples per day. They  now have the option of automated data capture, variable wavelength and temperature. Labs can now get readouts accurate to 0.0001°Arc (optical rotation, α).  This is a high level of precision for process industries and formulators.  Armed only with a polarimeter,  labs can set extremely narrow quality standards based on optical rotation. Density Meters Refractometers Polarimeters Saccharimeters Distributor Locator White Papers Technical Bulletins Service & Maintenance General Information Press Releases Customers/Industries General Inquiries An official website of the United States government The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site. The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely. Publications Account settings Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now . Advanced Search Journal List ACS AuthorChoice Demonstrating Basic Properties and Application of Polarimetry Using a Self-Constructed Polarimeter Lise kvittingen. † Department of Chemistry, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway Birte Johanne Sjursnes ‡ Faculty of Engineering, Østfold University College, 1757 Halden, Norway Associated Data International Commission for Uniform Methods for Sugar Analysis. ICUMSA Methods Book ; 2017; Methods GS1/2/3/9-1, GS1/2/3-2, GS2/3-1, GS3-1, GS4/7-1, GS5/7-1, GS6-1, GS6-3, GS7-7, GS4/7/8/5-2. https://www.icumsa.org/index.php?id=103 (accessed 2020-06-07). An easily constructed and inexpensive polarimeter with an optical rotation angle resolution of about 0.5° is presented. It is made from small pieces of polarizing film, 2 LEDs, a protractor, and a few wires, all held in place with plastic interlocking toy bricks, such as Lego bricks. The instrument was used to demonstrate the optical rotation of plane polarized light as a function of concentration, path length, temperature, and wavelength, and to determine enantiomeric excess in solutions of arabinose, the amount of limonene in citrus ski wax remover, and optical rotations of various types of honeys and essential oils. Results were comparable to values obtained on a commercial scientific instrument, and with literature values. Introduction Students encounter polarimetry in high school in connection with stereochemistry. The classical schematic representation of a polarimeter is illustrative and easy to understand, an asset not shared by the modern polarimeter, where basic features are hidden. Many simple, self-constructed polarimeters have been reported for use in demonstrations and student experiments. 1 − 11 Overheads have earlier been used as a light source. 2 − 5 These have now been replaced by LEDs, 6 , 7 lasers, 8 , 9 and LCD screens. 10 , 11 We have previously published descriptions of simple instruments constructed with plastic interlocking toy bricks, such as Lego, and LEDs for UV–vis absorption and fluorescence measurements intended for student experiments. 12 − 14 We add here polarimetry, extending the range of spectroscopic methods possible with the same basic building blocks. The polarimeter has the same layout as a classical polarimeter, making it easy to explain fundamental principles and instrumental design. It is not a black box system; it is inexpensive, easy to assemble, and flexible; can be used for many different compounds at varying concentrations; and has a precision and resolution sufficient for students’ use. This makes it a convenient device for a range of quantitative measurements. The emphasis in this article is on the design and application of the polarimeter. First, the design is explained. Second, basic properties such as optical rotation as a function of concentration, path length, temperature, and wavelength are demonstrated. Third, applications are presented: finding the enantiomeric excess in arabinose solutions and limonene in a citrus ski wax remover as well as the optical rotation of honeys, syrups, and essential oils. Equipment Setup Figure ​ Figure1 1 illustrates the arrangement of the instrument when the observer faces the detector. Self-constructed polarimeter. (a) From left to right: LED used as a light source (592 nm), polarizing film fixed between two Lego bricks, sample cuvette, and second polarizing film superimposed onto the end of a plastic dial that can rotate around the protractor. (b) LED used as a detector connected to a multimeter with a high internal resistance (>10 MΩ). 14 It is also possible to face the light source. This can be achieved by turning the protractor and arrow toward the detector side. However, independent of which direction observations are made in, the light from the source must hit the polarizing film before the plastic sheet that constitutes the dial, as plastic films depolarize plane polarized light. The flexibility obtained by using Lego bricks makes it simple to increase and reduce the path length and to change wavelengths. Optical rotation is often reported using the D-line of sodium at 589 nm; thus, a yellow LED with a peak λ at 592 nm has been used in most of the experiments here. Optical rotation readings of solutions are made relative to zero readings with solvent (or air). All readings are undertaken at minimum light intensity because readings at maximum light intensity are less accurate. 5 , 8 The resolution is about 0.5°; thus, small rotations have correspondingly larger error margins. See Supporting Information (SI) for detailed instructions. The layout closely resembles the classical schematic representation of optical rotation by chiral compounds. It is easy to demonstrate that the amount of radiation (light) passing through the second polarizing film is dependent on the rotatory power of the solution in the cuvette, and the degree of rotation of the second polarizing film. Experimental Section Polarizing film was purchased from American Polarizer (AP42-007T-12X19). Polarizing films intended for physics experiments in schools (from Amazon.com, without specifications) gave almost the same results and may be used. Cuvettes/cells used were of optical glass (path length; 1.0, 2.0, 4.0, and 10.0 cm) and purchased through Amazon.com. Plastic cuvettes cannot be used as plastic depolarizes plane polarized light. For the measurement of rotation as a function of wavelength, LEDs with wavelengths in the range 405–660 nm were used. For all other experiments, a yellow LED with a peak lambda of 592 nm and a bandwidth of 20 nm was used. See SI for more information and instructions for making the protractor, plastic dial, and pieces of polarizing film; for assembling the instrument; and for peforming measurements. Solutions were made of fructose, sucrose, arabinose, limonene, citrus ski wax remover, and some of the honeys and syrups. The essential oils were used neat. See SI for detailed information. Rotation measurements were made at minimum light transmission (lowest reading of the voltmeter connected to the detector LED) in a dimly lit room. Control measurements were regularly performed on a commercial scientific instrument (Anton Paar MCP 5100, 589 nm) for comparison. Measurements were made at ambient temperature (20–23 °C), unless otherwise stated. This is in the same range as the literature values. With respect to chemicals, the following apply: The carbohydrates are nonhazardous. Limonene, ethanol, citrus ski wax remover, and essential oils are both flammable and irritating. The preparation of solutions of limonene and citrus ski wax remover in ethanol and measurements of these solutions and essential oils require a properly ventilated location, preferably a fume hood. Goggles, gloves, and lab coat should be used. Experiments with sugars in water represent no hazards. Use a lid or something similar like a microscope slide to cover the cuvette if necessary. There are no hazards in constructing the device. None of the LEDs used here are in a wavelength range harmful to the eyes. However, the contrast between the light source and the environment can be strong in dim lighting, especially for high intensity LEDs. We advise to build extra walls of Lego-bricks or to cover with small pieces of material to shield the light. This is not a problem with the 592 nm yellow LED used in most experiments. The LEDs are cold-running and will not get warm. The voltage used is low, and the risk associated with this voltage is minimal. Basic Properties: Optical Rotation vs Concentration, Path Length, Temperature, and Wavelength Optical rotation measurements as a function of concentration were performed with ( R )- and ( S )-limonene ( Figure ​ Figure2 2 ). The linearity between concentration and observed rotation is good for both enantiomers. Optical rotation vs concentration for ( R )-(+)-limonene (diamond) and ( S )-(−)-limonene (circle). Self-constructed polarimeter: filled symbols; wavelength = 592 nm; path length = 4 cm. Anton Paar: open symbols; wavelength = 589 nm. Optical rotation as a function of path length and temperature was determined using d -fructose, increased with path length ( Figure ​ Figure3 3 ), and decreased with temperature ( Figure ​ Figure4 4 ). Optical rotation vs path length for d -(−)-fructose (0.5 g/mL). Wavelength = 592 nm. Optical rotation vs temperature of d -(−)-fructose (0.5 g/mL). Wavelength = 592 nm. Path length = 4 cm. Optical rotatory dispersion (ORD) is often demonstrated simply as a color change when white light is rotated by a solution of a chiral compound. 2 , 3 , 15 With LEDs of different wavelengths, this can easily be done quantitatively. Specific rotation as a function of wavelength (ORD) was determined for both d -fructose and d -sucrose. Specific rotations were calculated from observed optical rotation according to eq 1 where [α] is specific rotation, α is observed optical rotation, l is the length of the cuvette in dm, and c is the concentration in g/mL. Specific rotation increased with decreasing wavelength ( Figure ​ Figure5 5 ) displaying a plain ORD curve. The results are in accordance with literature values. 11 , 16 − 19 Extracted values for d -sucrose from Figure ​ Figure4 4 in Mahurin et al. 16 are included in Figure ​ Figure5 5 for comparison. Specific rotation vs wavelength. d -(−)-Fructose and d -(+)-sucrose both at 0.5 g/mL. Self-constructed polarimeter: filled symbols; wavelength = 405, 428, 470, 500, 525, 592, 626, 635, and 660 nm; path length = 4 cm. Anton Paar: open symbols; wavelength = 436, 546, 579, and 589 nm; path length = 10 cm. Extracted values from Mahurin et al.: 16 star symbol. Some Applications of Polarimetry We present here identification of unknown samples of d -fructose, d -sucrose, and d -glucose; quantification of ( R )-limonene in citrus ski wax remover; and determination of enantiomeric excess in a mixture of d - and l -arabinose, as well as discovery of chirality in natural compounds, such as honeys, syrups, and essential oils. Identification Identification of unknown solutions of carbohydrates such as glucose, fructose, and sucrose by polarimetry is a common laboratory exercise. 20 Unknown solutions of d -fructose, d -sucrose, and d -glucose were measured by students on the self-constructed polarimeter, and by the teacher both on the self-constructed polarimeter and on a commercial polarimeter (Anton Paar). The results are shown in Table 1 together with literature values. The calculated specific rotations for the student measurements agreed well with both the teacher’s results, measurements on a commercial instrument and literature values. Experimental details are given in SI , section 5.3. Solution Student Result [α] Teacher [α] Anton Paar [α] Literature Value [α] (A) d-(−)-Fructose –94.8° ± 3.3 –93.5° –93.7° –92° ± 2 (B) d-(+)-Sucrose +66.5° ± 2.5 +66.8° +65.9° +66.5° ± 1 (C) d-(+)-Glucose +52.9° ± 2.2 +54.5° +53.6° +53° ± 2 Quantification Quantification has been done by determining the content of ( R )-limonene in citrus ski wax remover. Limonene is mostly known as a fragrance and a flavor, but it is also used as a green solvent with a number of different applications including cleaning products, and it is being explored as a starting material and for use in functionalized foods. 21 The amount of limonene was calculated to be 25% using Figure ​ Figure2 2 as the calibrating curve. See SI section 5.4 for experimental details. Enantiomeric Excess Determination of enantiomeric excess is an important application in organic chemistry. Most carbohydrates exist in nature almost exclusively as the d -enantiomer making it expensive to purchase the “unnatural” l -enantiomer. Arabinose, on the other hand, exists as both enantiomers in nature. The l -enantiomer is the most common and is found in hemicelluloses, pectin, and gums and is easily obtainable. 22 − 26 The d -enantiomer is synthesized from d -glucose 22 , 27 − 29 and can also be purchased at a reasonable price. l -Arabinose is sometimes used as “sugar replacement”, as it apparently inhibits uptake of sucrose. 23 , 25 , 30 Arabinose is harmless and water-soluble and has a high specific optical rotation. It is therefore a suitable compound for investigating quantitative aspects such as enantiomeric excess (ee, most commonly given in %) in a mixture of enantiomers. The results from measuring commercial samples of l - and d -arabinose, a mixture of l - and d -arabinose, together with literature values for the enantiomers are presented in Table 2 . Solution (20% in H O) Optical Rotation α (deg) 592 nm (10 cm) Specific Optical Rotation [α]  (deg) Literature Value [α]  (deg) l-(+)-Arabinose +21 +105 +103 to +105 d-(−)-Arabinose –19.5 –97.5 −105 to −103 l-(+)-Arabinose: d-(−)-Arabinose = 3:1 +10.5 +52.5   Enantiomeric excess in percent is calculated according to eq 2 : As seen in Table 2 , the specific optical rotation [α] D of the mixture of l - and d -arabinose is +52.5°, showing an excess of the l -(+)-enantiomer. Using [α] D = +105° for the l -enantiomer gives ee = 50% which is in accordance with the prepared mixture of 25% l - and 75% d -arabinose. It is simple for the teacher to hand out a range of mixtures and let the students determine the enantiomeric excess (ee) using the self-constructed polarimeter. Honeys and Syrups Polarimetry is used frequently in the sugar industry. Having performed measurements with glucose, fructose, and sucrose, it makes sense to continue with an industrial application of polarimetry on sugar-containing compounds such as in analyses of honeys and syrups. 31 − 37 As these viscous liquids can be somewhat nontransparent in the visual (VIS) region of the electromagnetic spectrum but transparent in the near-infrared (NIR) region, NIR polarimetry is preferred for accurate measurements. Nevertheless, it is possible to apply VIS polarimetry semiquantitatively directly. 31 , 38 Honeys and syrups rotate plane polarized light both to the left (levorotatory, −) and right (dextrorotatory, +) mirroring predominantly the amount of d -glucose (+), d -sucrose (+), and d -fructose (−) in them. Honey is a complex mixture. However, fructose dominates in floral honey, 36 , 37 and in general, the net optical rotation will be levorotatory. In honeydew, on the other hand, glucose together with other strongly dextrorotatory carbohydrates make the total optical rotation dextrorotatory. 36 , 37 Honeydew is not produced from flower nectar like floral honey, but from secretions of living plants or excretions from plant-sucking insects on plants. 37 If a honey is dextrorotatory, it could also be adulterated honey. 36 In our case (see Table 3 ), three of the honeys were levorotatory, consistent with floral honeys, while the fourth (Serbian honey) was dextrorotatory and is most likely honeydew. Type of Honey/Syrup Calculated Optical Rotation α (deg) for Neat Kjartan’s honey dew/forest honey –8 Liquid mountain honey European acacia –6 Kjartan’s raspberry honey –4 Serbian forest honey +4 Lyle golden syrup +12.5 Maple syrup Winnitou +22 Syrups are dextrorotatory containing relatively more sucrose and glucose than fructose; however, there are also different types of syrups. Golden syrups are generally made from refiners’ return syrup (leftover liquid with sucrose from production of white sugar from sugar canes) where most of the sucrose is hydrolyzed (inverted) to glucose and fructose. 39 , 40 Maple syrup is concentrated maple sap that has not been hydrolyzed and contains mostly sucrose and only small amounts of fructose and glucose. 41 − 43 These relative amounts of sucrose, fructose, and glucose are reflected in the optical rotations where Lyle golden syrup has a lower rotation than maple syrup due to the higher content of fructose. See SI section 5.9 for experimental details. Enantiomers and Essential Oils Nature is an important pool for chiral compounds. Chiral fragrant compounds are often used in organic chemistry textbooks to explain different activities of enantiomers in biological systems. The significance is of course greater for chiral drugs, but with fragrant compounds the students can themselves experience the difference. Olfactory discrimination of enantiomers is an intriguing field. 44 − 47 Most known are perhaps carvone and limonene. ( R )-(−)-Carvone has a sweet mint smell and is naturally found in spearmint oil. ( S )-(+)-Carvone has a more spicy smell and is the major compound in oil from caraway seeds. 44 , 48 , 49 Limonene is even more common. ( R )-(+)-Limonene is the major component in oil from citrus peel and is in particular associated with oranges. ( S )-(−)-Limonene has a more piney and turpentine smell. 44 Many essential oils contain fragrant chiral compounds, and they rotate plane polarized light both levorotatory and dextrorotatory. Measuring the optical rotation of essential oils shows the diversity of optically active compounds in natural compounds. These oils also lend themselves to investigation, combining a literature study about chiral compounds in oils, their uses, and practical experiments for their extraction. 50 − 53 To facilitate exploration, the measured optical rotations of some essential oils together with their major chiral compounds as found in literature reports are given in Table 4 . The net rotation is, of course, dependent on all chiral compounds present, and their relative amounts. There is no simple direct correlation between the net rotation of the essential oils and the compounds included in Table 4 . The exact amounts of different compounds can vary depending on season, variety, and origin and so may also the optical rotation. Essential Oil, (Supplier) Optical Rotation α (deg), Neat Major Chiral Compounds Literature Value [α] (deg) Preparation Eucalyptus oil, (Karo Pharma) +2 (+)-α-Pinene +50.7 Neat Peppermint oil, (Karo Pharma) –9.5 to −10 (−)-Menthol –49.5 10% in ethanol     l-(−)-Menthone –25 Neat Lavender oil, (Teleurt) –3.5 to −4 ( )-(−)-Linalool –20 Neat     ( )-(−)-Linalyl acetate –9.45* Neat     ( )-(+)-Camphor +44.1 25% in ethanol     ( )-(−)-Camphor –43 10% in ethanol     (+)-Borneol +36 5% in ethanol Caraway oil, (Carl Roth) +29 ( )-(+)-Carvone +55 Neat     ( )-(+)-Limonene +115 10% in ethanol Black spruce oil, (Teleurt) –11 (−)-Bornyl acetate –46 1% in ethanol     (−)-Camphene –106.1 4% in ether     (−)-α-Pinene –50.7 Neat     (+)-δ-3-Carene +17 Neat     ( )-(−)-Limonene –94.4 10% in ethanol Pine needle oil, (Teleurt) –8 (+)-α-Pinene +50.7 Neat     (−)-α-Pinene –50.7 Neat     (−)-β-Pinene –22 Neat     (−)-Camphene –106.1* 4% in ether     (+)-δ-3-Carene +17 Neat     ( )-(−)-Limonene –94.4 10% in ethanol     ( )-(+)-Limonene +115.5 10% in ethanol Orange Douce oil, (Florame) +40 ( )-(+)-Limonene +115.5 10% in ethanol Lemon oil, (Florame) +25 ( )-(+)-Limonene +115.5 10% in ethanol     (−)-β-Pinene –22 neat Mandarin oil, (Pima) +31 ( )-(+)-Limonene +115.5 10% in ethanol A simple, inexpensive, and flexible polarimeter was made from two LEDs, a polarizing film, a few wires, a single resistor, a battery, a few Lego bricks, and one multimeter. This polarimeter is used to demonstrate basic properties of polarimetry such as optical rotation as a function of concentration, path length, temperature, and wavelength, as well as to investigate some applications such as determining the enantiomeric excess in a solution of arabinose, the amount of limonene in citrus ski wax remover, and the optical rotations of syrups, honeys, and essential oils. Acknowledgments The authors are grateful to Mickaël Fontaine for graphical artwork, to Richard Verley for scientific discussions, to a vigilant referee, and to the library service at NTNU. Supporting Information Available The Supporting Information is available at https://pubs.acs.org/doi/10.1021/acs.jchemed.9b00763 . Instructions and patterns for building the polarimeter, and experimental details ( PDF , DOCX ) The authors declare no competing financial interest. Supplementary Material Shavitz R. An Easily Constructed Student Polarimeter . J. Chem. Educ. 1978, 55 ( 10 ), 682. 10.1021/ed055p682. [ CrossRef ] [ Google Scholar ] Kinney J. B.; Skinner J. F. A Device for Easy Demonstration of Optical Activity and Optical Rotatory Dispersion . J. Chem. Educ. 1977, 54 ( 8 ), 494. 10.1021/ed054p494.1. [ CrossRef ] [ Google Scholar ] Dorn H. C.; Bell H.; Birkett T. A Simple Polarimeter and Experiments Utilzing an Overhead Projector . J. Chem. Educ. 1984, 61 ( 12 ), 1106–1107. 10.1021/ed061p1106. [ CrossRef ] [ Google Scholar ] Mehta A.; Greenbowe T. J. A Shoebox Polarimeter: An Inexpensive Analytical Tool for Teachers and Students . J. Chem. Educ. 2011, 88 ( 8 ), 1194–1197. 10.1021/ed1011635. [ CrossRef ] [ Google Scholar ] Breton G. W. An Inexpensive Homemade Polarimeter for Demonstration Use in the Classroom . J. Lab. Chem. Educ. 2015, 3 ( 1 ), 7–11. 10.5923/j.jlce.20150301.02. [ CrossRef ] [ Google Scholar ] Isaacs M. S. Two Readily-Constructed Instruments for Teaching Laboratory . J. Chem. Educ. 1983, 60 ( 7 ), 607–610. 10.1021/ed060p607. [ CrossRef ] [ Google Scholar ] Stary J. E.; Woldow W. Build a Simple Polarimeter . J. Chem. Educ. 2001, 78 ( 5 ), 644. 10.1021/ed078p644. [ CrossRef ] [ Google Scholar ] Darveau S. A.; Mueller J.; Vaverka A.; Barta C.; Fitch A.; Jurzenski J.; Gindt Y. A Modular Laser Apparatus for Polarimetry, Nephelometry, and Fluorimetry in General Chemistry . J. Chem. Educ. 2004, 81 ( 3 ), 401–405. 10.1021/ed081p401. [ CrossRef ] [ Google Scholar ] Lisboa P.; Sotomayor J.; Ribeiro P. A New Cost-Effective Diode Laser Polarimeter Apparatus Constructed by Undergraduate Students . J. Chem. Educ. 2010, 87 ( 12 ), 1408–1410. 10.1021/ed100530f. [ CrossRef ] [ Google Scholar ] Schwartz P. M.; Lepore D. M.; Morneau B. N.; Barratt C. Demonstrating Optical Activity Using an iPad . J. Chem. Educ. 2011, 88 ( 12 ), 1692–1693. 10.1021/ed200014m. [ CrossRef ] [ Google Scholar ] Thomson P. I. T. Is That a Polarimeter in Your pocket? A Zero-cost, Technology-Enabled Demonstration of Optical Rotation . J. Chem. Educ. 2018, 95 ( 5 ), 837–841. 10.1021/acs.jchemed.7b00767. [ CrossRef ] [ Google Scholar ] Asheim J.; Kvittingen E. V.; Kvittingen L.; Verley R. L. P. A Simple, Small-Scale Lego Colorimeter with a Light-Emitting Diode (LED) Used as Detector . J. Chem. Educ. 2014, 91 ( 7 ), 1037–1039. 10.1021/ed400838n. [ CrossRef ] [ Google Scholar ] Kvittingen E. V.; Kvittingen L.; Sjursnes B. J.; Verley R. L. P. Simple and Inexpensive UV-Photometer Using LEDs as Both Light Source and Detector . J. Chem. Educ. 2016, 93 ( 10 ), 1814–1817. 10.1021/acs.jchemed.6b00156. [ CrossRef ] [ Google Scholar ] Kvittingen E. V.; Kvittingen L.; Melø T. B.; Sjursnes B. J.; Verley R. L. P. Demonstrating Basic Properties of Spectroscopy Using a Self-Constructed Combined Fluorimeter and UV-Photometer . J. Chem. Educ. 2017, 94 ( 10 ), 1486–1491. 10.1021/acs.jchemed.7b00121. [ CrossRef ] [ Google Scholar ] Koubek E.; Quinn H. Change in Optical Rotation with Wavelength . J. Chem. Educ. 1989, 66 ( 10 ), 853. 10.1021/ed066p853.1. [ CrossRef ] [ Google Scholar ] Mahurin S. M.; Compton R. N.; Zare R. N. Demonstration of Optical Rotatory Dispersion of Sucrose . J. Chem. Educ. 1999, 76 ( 9 ), 1234–1236. 10.1021/ed076p1234. [ CrossRef ] [ Google Scholar ] Soetedjo H.; Räty J. Use of a modified Drude’s equation to investigate the optical rotation property of sugars . Optik 2014, 125 ( 24 ), 7162–7165. 10.1016/j.ijleo.2014.07.112. [ CrossRef ] [ Google Scholar ] Lei Y.; Jia H.; Xu X.; Jiang S. An Optimized Drude’s Equation For Polarization Measurement in the Visible Region and Concentrations Estimation . IEEE Photonics J. 2017, 10 ( 1 ), 6100209. 10.1109/JPHOT.2017.2787576. [ CrossRef ] [ Google Scholar ] Castiglioni E.; Abbate S.; Longhi G. Experimental Methods for Measuring Optical Rotatory Dispersion: Suvey and Outlook . Chirality 2011, 23 ( 9 ), 711–716. 10.1002/chir.20981. [ PubMed ] [ CrossRef ] [ Google Scholar ] Wrolstad R. E. Food Carbohydrate Chemistry , 1st ed.; John Wiley & Sons Inc.: New York, 2012; pp 183–185. [ Google Scholar ] Ciriminna R.; Lomeli-Rodriguez M.; Demma Cara P.; Lopez-Sanchez J. A.; Pagliaro M. Limonene: A versatile Chemical of the Bioeconomy . Chem. Commun. 2014, 50 ( 97 ), 15288–15296. 10.1039/C4CC06147K. [ PubMed ] [ CrossRef ] [ Google Scholar ] Pigman W. W. Chemistry of the Carbohydrates ; Academic Press Inc.: New York, 1948; pp 102–103. [ Google Scholar ] Fehér C. Novel approaches for biotechnological production and application of L-arabinose . J. Carbohydr. Chem. 2018, 37 ( 5 ), 251–284. 10.1080/07328303.2018.1491049. [ CrossRef ] [ Google Scholar ] Fehér C.; Gazsó Z.; Tatijarern P.; Molnár M.; Barta Z.; Réczey K. Investigation of selective arabinose release from corn fibre by acid hydrolysis under mild conditions . J. Chem. Technol. Biotechnol. 2015, 90 ( 5 ), 896–906. 10.1002/jctb.4395. [ CrossRef ] [ Google Scholar ] Loeza-Corte J. M.; Verde-Calco R. R.; Cruz-Sosa F.; Vernon-Carter E. J.; Huerta-Ochoa S. L-Arabinose production by hydrolysis of mesquite gum by a crude extract with α-L-arabinosefuranosidase activity from Aspergillus niger . Rev. Mex. Ing. Quimica 2007, 6 ( 3 ), 259–265. [ Google Scholar ] Pencz K.; Gál B.; Fehér C.; Barta Z.. Arabinose biopurification by Ogataea zsoltii yeast . In Chemical Engineering Conference ; University of Pannonia: Veszprém, Hungary, 2016; pp 82–86. [ Google Scholar ] Monrad R. N.; Madsen R. Modern methods for shortening and extending the carbon chain in carbohydrates at the anomeric center . Tetrahedron 2011, 67 ( 46 ), 8825–8850. 10.1016/j.tet.2011.08.047. [ CrossRef ] [ Google Scholar ] Hourdin G.; Germain A.; Moreau C.; Fajula F. The Catalysis of the Ruff Oxidative Degradation of Aldonic Acids by Copper(II)-Containing Solids . J. Catal. 2002, 209 ( 1 ), 217–224. 10.1006/jcat.2002.3608. [ CrossRef ] [ Google Scholar ] Jiřičný V.; Staněk V. Preparation of D-Arabinose in a Laboratory Fluidized Bed Electrode . Collect. Czech. Chem. Commun. 1995, 60 ( 5 ), 863–874. 10.1135/cccc19950863. [ CrossRef ] [ Google Scholar ] Krog-Mikkelsen I.; Hels O.; Tetens I.; Holst J. J.; Andersen J. R.; Bukhave K. The effects of L-arabinose on intestinal sucrase activity: dose-response studies in vitro and in humans . Am. J. Clin. Nutr. 2011, 94 ( 2 ), 472–478. 10.3945/ajcn.111.014225. [ PubMed ] [ CrossRef ] [ Google Scholar ] Horwitz W. Sugar and Sugar Products . Official Methods of Analysis of AOAC International , 17th ed.; AOAC International: Gaithersburg, MD, 2000; Chapter 44, pp 4–7, 24. [ Google Scholar ] Bogdanov S.; Martin P.; Lüllmann C. Harmonised methods of the European Honey Commission . Apidologie 1997, ( extra issue ), 1–59. [ Google Scholar ] http://www.ihc-platform.net/ihcmethods2009.pdf . (accessed 2020-06-07). Pigman W. The Carbohydrates: Chemistry, Biochemistry, Physiology ; Academic Press Inc.: New York, 1957; pp 610–612. [ Google Scholar ] Bogdanov S.; Ruoff K.; Persano Oddo L. Physico-chemical methods for the characterisation of unifloral honeys: a review . Apidologie 2004, 35 ( Suppl. 1 ), S4–S17. 10.1051/apido:2004047. [ CrossRef ] [ Google Scholar ] García-Alvarez M.; Ceresuela S.; Huidobro J. F.; Hermida M.; Rodríguez-Otero J. L. Determination of Polarimetric Parameters of Honey by Near-Infrared Transflectance Spectroscopy . J. Agric. Food Chem. 2002, 50 ( 3 ), 419–425. 10.1021/jf0105438. [ PubMed ] [ CrossRef ] [ Google Scholar ] Pita-Calvo C.; Vazquez M. Differences between honeydew and blossom honeys: A review . Trends Food Sci. Technol. 2017, 59 , 79–87. 10.1016/j.tifs.2016.11.015. [ CrossRef ] [ Google Scholar ] Taylor J. What Is Honey Made of? The Optical Rotation of Sugars . In Search of More Solutions ; Royal Society of Chemistry Education Resources, 1995; Vol. 15 , experiment 14, pp 94–95. http://rsc.org/learn-chemistry/resource/res00000579/what-is-honey-made-of-the-optical-rotation-of-sugars (accessed 2020-06-07). Clarke M. A. Encyclopedia of Food Science and Nutrition , 2nd ed.; Academic Press, 2003; Syrups, pp 5711–5717. [ Google Scholar ] Varzakas T.; Labropoulos A.; Anestis S.. Sweeteners: Nutritional Aspects, Applications, and Production Technology ; CRC Press, 2012; Chapter 6, Syrups: pp 160, 168. [ Google Scholar ] Stuckel J. G.; Low N. H. The chemical composition of 80 pure maple syrup samples produced in North America . Food Res. Int. 1996, 29 ( 3–4 ), 373–379. 10.1016/0963-9969(96)00000-2. [ CrossRef ] [ Google Scholar ] Ball D. W. The Chemical Composition of Maple Syrup . J. Chem. Educ. 2007, 84 ( 10 ), 1647–1650. 10.1021/ed084p1647. [ CrossRef ] [ Google Scholar ] Perkins T. D.; van den Berg A. K. Chapter 4 Maple Syrup – Production, Composition, Chemistry, and Sensory Characteristics . Adv. Food Nutr. Res. 2009, 56 , 101–143. 10.1016/S1043-4526(08)00604-9. [ PubMed ] [ CrossRef ] [ Google Scholar ] Laska M.; Teubner P. Olfactory Discrimination Ability of Human Subjects for Ten Pairs of Enantiomers . Chem. Senses 1999, 24 ( 2 ), 161–170. 10.1093/chemse/24.2.161. [ PubMed ] [ CrossRef ] [ Google Scholar ] Bentley R. The Nose as a Stereochemist. Enantiomers and Odor . Chem. Rev. 2006, 106 ( 9 ), 4099–4112. 10.1021/cr050049t. [ PubMed ] [ CrossRef ] [ Google Scholar ] Sell C. S. Chemistry and the Sense of Smell ; John Wiley & Sons: NJ, 2014; pp 188–208. [ Google Scholar ] Pavia D. L.; Lampman G. M.; Kriz G. S; Engel R. G.. Introduction to Organic Laboratory Techniques: A Small Scale Approach , 2nd ed.; Thomson-Brooks/Cole: USA, 2005; pp 108–118. [ Google Scholar ] Leitereg T. J.; Guadagni D. G.; Harris J.; Mon T. R.; Teranishi R. Chemical and sensory data supporting the difference between the odors of the enantiomeric carvones . J. Agric. Food Chem. 1971, 19 ( 4 ), 785–787. 10.1021/jf60176a035. [ CrossRef ] [ Google Scholar ] König W. A.; Krebber R.; Evers P.; Bruhn G. Stereochemical Analysis of Constituents of Essential Oils and Flavor Compounds by Enantioselective Capillary Gas Chromatography . J. High Resolut. Chromatogr. 1990, 13 ( 5 ), 328–332. 10.1002/jhrc.1240130507. [ CrossRef ] [ Google Scholar ] Nimitz J. S. Experiments in Organic Chemistry: From Microscale to Macroscale , 1st ed.; Prentice Hall, 1991; pp 196–208. [ Google Scholar ] Pavia D. L.; Lampman G. M.; Kriz G. S; Engel R. G.. Introduction to Organic Laboratory Techniques: A Small Scale Approach , 2nd ed.; Thomson - Brooks/Cole: USA, 2005; pp 101–119, 523–528, 786–794, 857–866. [ Google Scholar ] Doyle M. P.; Mungall W. S.. Experimental Organic Chemistry ; John Wiley & Sons, 1980; pp 61–80. [ Google Scholar ] Finefield J. M.; Sherman D. H.; Kreitman M.; Williams R. M. Enantiomeric Natural Products: Occurrence and Biogenesis . Angew. Chem., Int. Ed. 2012, 51 ( 20 ), 4802–4806. 10.1002/anie.201107204. [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ] Silvestre A. J. D.; Cavaleiro J. A. S.; Delmond B.; Filliatre C.; Bourgeois G. Analysis of the variation of the essential oil composition of Eucalyptus globulus Labill. from Portugal using multivariate statistical analysis . Ind. Crops Prod. 1997, 6 ( 1 ), 27–3. 10.1016/S0926-6690(96)00200-2. [ CrossRef ] [ Google Scholar ] Sebei K.; Sakouhi F.; Herchi W.; Khouja M. L.; Boukhchina S. Chemical composition and antibacterial activities of seven Eucalyptus species essential oils leaves . Biol. Res. 2015, 48 , 7. 10.1186/0717-6287-48-7. [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ] Kreck M.; Scharrer A.; Bilke S.; Mosandl A. Enantioselective analysis of monoterpene compounds in essential oils by stir bar sorptive extraction (SBSE)–enantio-MDGC–MS . Flavour Fragrance J. 2002, 17 ( 1 ), 32–40. 10.1002/ffj.1033. [ CrossRef ] [ Google Scholar ] Rohloff J. Monoterpene Composition of Essential Oil from Peppermint (Mentha × piperita L.) with Regard to Leaf Position Using Solid-Phase Microextraction and Gas Chromatography/Mass Spectrometry Analysis . J. Agric. Food Chem. 1999, 47 ( 9 ), 3782–3786. 10.1021/jf981310s. [ PubMed ] [ CrossRef ] [ Google Scholar ] Verma R. S.; Rahman L.; Verma R. K.; Chauhan A.; Yadav A. K.; Singh A. Essential Oil Composition of Menthol Mint (Mentha arvensis) and Peppermint (Mentha piperita) Cultivars at Different Stages of Plant Growth from Kumaon Region of Western Himalaya . J. Med. Aromat. Plants 2010, 1 ( 1 ), 13–18. [ Google Scholar ] Bicchi C.; Pisciotta A. Use of two-dimensional gas chromatography in the direct enantiomer separation of chiral essential oil components . J. Chromatogr. A 1990, 508 , 341–348. 10.1016/S0021-9673(00)91276-7. [ CrossRef ] [ Google Scholar ] Shellie R.; Mondello L.; Marriott P.; Dugo G. Characterisation of lavender essential oils by using gas chromatography–mass spectrometry with correlation of linear retention indices and comparison with comprehensive two-dimensional gas chromatography . J. Chromatogr. A 2002, 970 ( 1–2 ), 225–234. 10.1016/S0021-9673(02)00653-2. [ PubMed ] [ CrossRef ] [ Google Scholar ] Marincaş O.; Feher I. A new cost-effective approach for lavender essential oils quality assessment . Ind. Crops Prod. 2018, 125 , 241–247. 10.1016/j.indcrop.2018.09.010. [ CrossRef ] [ Google Scholar ] Casabianca H.; Graff J. B.; Faugier V.; Fleig F.; Grenier C. Enantiomeric Distribution Studies of Linalool and Linalyl Acetate. A Powerful Tool for Authenticity Control of Essential Oils . J. High Resolut. Chromatogr. 1998, 21 ( 2 ), 107–112. 10.1002/(SICI)1521-4168(19980201)21:2<107::AID-JHRC107>3.0.CO;2-A. [ CrossRef ] [ Google Scholar ] Renaud E. N. C.; Charles D. J.; Simon J. E. Essential Oil Quantity and Composition from 10 Cultivars of Organically Grown Lavender and Lavandin . J. Essent. Oil Res. 2001, 13 ( 4 ), 269–273. 10.1080/10412905.2001.9699691. [ CrossRef ] [ Google Scholar ] Baser K. H. C.; Ozek T.; Konakchiev A. Enantiomeric Distribution of Linalool, Linalyl Acetate and Camphor in Bulgarian Lavender Oil . J. Essent. Oil Res. 2005, 17 ( 2 ), 135–136. 10.1080/10412905.2005.9698855. [ CrossRef ] [ Google Scholar ] Ravid U.; Putievsky E.; Katzir I. Stereochemical Analysis of Borneol in Essential Oils Using Permethylated β-Cyclodextrin as a Chiral Stationary Phase . Flavour Fragrance J. 1996, 11 ( 3 ), 191–195. 10.1002/(SICI)1099-1026(199605)11:3<191::AID-FFJ568>3.0.CO;2-M. [ CrossRef ] [ Google Scholar ] Laribi B.; Kouki K.; Mougou A.; Marzouk B. Fatty acid and essential oil composition of three Tunisian caraway (Carum carvi L.) seed ecotypes . J. Sci. Food Agric. 2010, 90 ( 3 ), 391–396. 10.1002/jsfa.3827. [ PubMed ] [ CrossRef ] [ Google Scholar ] Zawirska-Wojtasiak R.; Wasowicz E. Enantiomeric composition of limonene and carvone in seeds of dill and caraway grown in Poland . Polish J. Food Nutr. Sci. 2000, 50 ( 3 ), 9–13. [ Google Scholar ] Bouwmeester H. J.; Davies J. A. R.; Toxopeus H. Enantiomeric composition of carvone, limonene, and carveols in seeds of dill and annual and biennial caraway varieties . J. Agric. Food Chem. 1995, 43 ( 12 ), 3057–3064. 10.1021/jf00060a013. [ CrossRef ] [ Google Scholar ] Garneau F.-X.; Collin G.; Gagnon H.; Pichette A. Chemical Composition of the Hydrosol and the Essential Oil of Three Different Species of the Pinaceae Family: Picea glauca (Moench) Voss., Picea mariana (Mill.) B.S.P., and Abies balsamea (L.) Mill . J. Essent. Oil-Bear. Plants 2012, 15 ( 2 ), 227–236. 10.1080/0972060X.2012.10644040. [ CrossRef ] [ Google Scholar ] Kocak A.; Kilic O. Identification of Essential Oil Composition of Four Picea Mill. (Pinaceae) Species from Canada . Journal of Agricultural Science and Technology B 2014, 4 ( 3 ), 209–214. [ Google Scholar ] Poaty B.; Lahlah J.; Porqueres F.; Bouafif H. Composition, antimicrobial and antioxidant activities of seven essential oils from the North American boreal forest . World J. Microbiol. Biotechnol. 2015, 31 ( 6 ), 907–919. 10.1007/s11274-015-1845-y. [ PubMed ] [ CrossRef ] [ Google Scholar ] Brockerhoff E. G. Host Location and ovipostition in Strobilomvia spp., (Diptera: Anthomniidae), infesting spruce cones . PhD dissertation, University of Toronto: Ontario, 1998; pp 45–47. [ Google Scholar ] Ioannou E.; Koutsaviti A.; Tzakou O.; Roussis V. The genus Pinus: a comparative study on the needle essential oil composition of 46 pine species . Phytochem. Rev. 2014, 13 ( 4 ), 741–768. 10.1007/s11101-014-9338-4. [ CrossRef ] [ Google Scholar ] Sjödin K.; Persson M.; Borg-Karlson A.-K.; Norin T. Enantiomeric Composition of Monoterpene Hydrocarbons in Different Tissues of Four Individuals of Pinus Sylvestris . Phytochemistry 1996, 41 ( 2 ), 439–445. 10.1016/0031-9422(95)00652-4. [ CrossRef ] [ Google Scholar ] Ochocka R. J.; Asztemborska M.; Sybilska D.; Langa W. Determination of Enantiomers of Terpenic Hydrocarbons in Essential Oils Obtained from Species of Pinus and Abies . Pharm. Biol. 2002, 40 ( 5 ), 395–399. 10.1076/phbi.40.5.395.8452. [ CrossRef ] [ Google Scholar ] Bonaccorsi I.; Sciarrone D.; Cotroneo A.; Mondello L.; Dugo P.; Dugo G. Enantiomeric distribution of key volatile components in Citrus essential oils . Rev. Bras. Farmacogn. 2011, 21 ( 5 ), 841–849. 10.1590/S0102-695X2011005000123. [ CrossRef ] [ Google Scholar ] Gok A.ı; Ismail Kirbaslar S.; Gulay Kirbaslar F. Comparison of lemon oil composition after using different extraction methods . J. Essent. Oil Res. 2015, 27 ( 1 ), 17–22. 10.1080/10412905.2014.982872. [ CrossRef ] [ Google Scholar ] Teacher Resource Center Pasco partnerships. 2024 Catalogs & Brochures Sugar concentration through polarimetry. Students use a polarimeter to determine the unknown concentration of a sucrose solution. Grade Level: College Subject: Chemistry Student Files 691.41 KB 477.29 KB Teacher Files Sign In to your PASCO account to access teacher files and sample data. Featured Equipment Wireless Polarimeter PASCO's Wireless Polarimeter measures the optical rotation of chiral compounds and features Bluetooth connectivity. Polarimeter Measure the concentration of optically active compounds by determining the optical rotation of their solution. Many lab activities can be conducted with our Wireless , PASPORT , or even ScienceWorkshop sensors and equipment. For assistance with substituting compatible instruments, contact PASCO Technical Support . We're here to help. Copyright © 2021 PASCO Source Collection: Lab #01 Polarimeter Investigations More experiments. Advanced Placement Distance Learning Lab: Kinetics of Crystal Violet Fading (Colorimeter) Analysis of Food Dyes in Sports Drinks Modeling Absorption of Radiation High School Phase Change Research Enhancement: Galvanic Cells Specific Heat 364 IMAGES Polarimetry Polarimeter Understanding Polarimetry > Experiment 6 from Organic Chemistry with Vernier Polarimeter principle and instrumentation 🌟 ✅ Virtual Labs Specific Rotation Equation Vs Optical Rotation VIDEO धुवण मापी , polarimeter in hindi, knowledge ADDA,BSC final year physical chemistry in hindi bsc3rd Optical activity 02 Polarimeter (جهاز البولاريميتر ) Polarimeter Experiment| What is Least Count? |Main Scale| Vernier Scale Polarimeter Experiment NRT 3000 polarimeter COMMENTS PDF 7. Polarimetry Equation (1) shows that for a given length l, the plot of versus c will be a straight line. This plot is known as the calibration curve of the polarimeter for the active solution. This plot can be used to find the concentration c of an unknown solution of the same solute by measuring the rotation produced by it. Polarimetry Polarimetry is the measurement of the optical activity of a substance, which is its ability to rotate the plane of polarized light. Learn how polarimetry works, how it was discovered and developed, and how it is used to determine the optical purity of enantiomers. Using a Polarimeter to Measure Specific Rotation Using a Polarimeter and a demonstration of the physical phenomenon underpinning the technique. Using the polarimeter 1:45Demonstrating polarimetry with a las... Polarimetry Experiments Learn how to build and use a home-made polarimeter to measure the rotation of polarized light by chiral molecules. Explore the identity and concentration of sugars in soda and other solutions with this hands-on activity. PDF Stereochemistry and Polarimetry The software should automatically recognize the polarimeter and display a graph with illumination along the y-axis and angle along the x-axis. Place the water sample into the polarimeter. ... If they are off by more than 10%, perform the experiment again. B. Determination of the Enantiomeric Excess in impure samples. PDF Experiment No. 3 Object: To find the specific rotation of sugar Learn how to measure the specific rotation of sugar solution using a polarimeter, a device that detects the plane of polarization of light. Follow the procedure, formula, observations, calculation and result of this experiment. To measure the specific rotation of cane sugar using Polarimeter Enter the value of ΔX and ΔY press "submit" button. Slope of the graph and specific rotation will be calculated. Repeat the experiment by changing the concentration of Sugar Solution. Community Links Sakshat Portal Outreach Portal FAQ: Virtual Labs. Contact Us Phone: General Information: 011-26582050 Email: [email protected]. PDF POLARIMETER (BIQUARTZ) Learn how to determine the specific rotation of cane sugar solution using a polarimeter. Follow the procedure, formula, observations, calculations and results of this optics laboratory experiment. Study Chirality with a Homemade Polarimeter Look online for other chiral molecules to experiment with that are commonly available, such as amino acids or over-the-counter drugs. Test various juices and fruit drinks for optical activity. Use the polarimeter to track the consumption of glucose by a yeast culture. Make a "high-throughput" holder that has 10 chambers for different solutions. PDF Optical Activity Laboratory polarimeter; for example, the relationship of the specific rotation, [α], of a molecule to its concentration, c ... • Make a graph in Excel of the corrected values of Θ as a function of concentration (c); you should include ... Experiment 2. The Relationship between Optical Activity and Pathlength. R-(-)-carvone is the primary odor ... Polarimeter Investigations Students use a polarimeter determine reaction order and rate constant of an acid-catalyzed sucrose hydrolysis reaction and an invertase-catalyzed reaction. 04) Sugar Concentration through Polarimetry: Biot's Law ... This experiment includes Teacher Resources that can be downloaded for free after signing into or creating a PASCO account. To determine the specific rotation of a sugar using a polarimeter Functioning of the polarimeter a b . Fig. 1: Schematic representation of the functioning of the polarimeter. a. When the sample tube is empty, the planes of polarization of the polarizing and the analyzing prisms are same and αobs is 0° b. Using Polarimetry to Identify Sugar and Sweeteners in Beverages These are easily measured with a polarimeter. ... A graph is produced that shows clear changes in the light's polarization with respect to angle. Specific rotation is a property that can be used to identify chemical compounds that behave this way. ... This experiment is #13 of Food Chemistry Experiments. The experiment in the book includes ... Polarimeter A polarimeter is a scientific instrument that measures optical rotation, the angle of rotation caused by passing linearly polarized light through an optically active substance. Learn about the history, measuring principle, construction and types of polarimeters, such as Laurent's half-shade polarimeter. Understanding Polarimetry > Experiment 6 from Organic ... Learn how to use a polarimeter to measure the optical activity of optically active compounds, such as enantiomers and sugars. This experiment from Organic Chemistry with Vernier provides instructions, data, and graphs for college students. Polarimeter (video) The polarimeter is a quantitative method used to determine the optical rotation of a chiral molecule. A molecule is considered chiral if it is non-superimposable on its mirror image. More specifically, chiral molecules that are mirror images of one another are called enantiomers (Figure 2). Enantiomers have the same physical properties such as ... Specific Rotation Equation Vs Optical Rotation Learn the difference between specific rotation equation and optical rotation, two terms used in polarimetry to measure the rotation of polarized light by chiral substances. Find out how to calculate specific rotation, use different light sources, and interpret observed rotations of mixtures. Demonstrating Basic Properties and Application of Polarimetry Using a The polarimeter has the same layout as a classical polarimeter, making it easy to explain fundamental principles and instrumental design. It is not a black box system; it is inexpensive, easy to assemble, and flexible; can be used for many different compounds at varying concentrations; and has a precision and resolution sufficient for students ... Sugar Concentration through Polarimetry Support. Many lab activities can be conducted with our Wireless, PASPORT, or even ScienceWorkshop sensors and equipment. For assistance with substituting compatible instruments, contact PASCO Technical Support. We're here to help. Students use a polarimeter to determine the unknown concentration of a sucrose solution. Lab 6 Orgo / Experiment 7: Polarimetric Analysis Of Organic ... From the experiment, it was shown that experimenters had learned how to successfully use a polarimeter and optical rotation as a method of determining the identity of unknown sugars. These techniques made it possible to identify the substance, the enantiomeric purity of the substance and the concentration of a known substance in solution. essay homework paper phd project resume review study thesis