Devansh Gobin “The Construction of an Inexpensive Polarimeter with Accuracy and Precision comparable to Commercial Models” Department of Chemistry & Biochemistry, Concordia University, 7141, Sherbrooke St W, Montreal, QC, Canada, H4B 1R6 Vanier College/CEGEP, 821 Sainte Croix Ave, Saint-Laurent, Montreal, QC, Canada, H4L 3X9

Abstract

Polarimeters are used to measure the optical rotation of optically active substances;

substances that rotate the plane of polarized light by an angle. The goal of the project was to

build an inexpensive polarimeter that provides similar, or better accuracy and precision as

commercial polarimeters. The specific optical rotation of a known sucrose solution was

measured on a commercial polarimeter as +66.26 ± 0.0068° (+66.5° expected from the literature)

as a reference sample. Using a prototypic polarimeter, when data was measured manually using a

Vernier scale (precision: 5 minutes), the angle of rotation was 67.12 ± 0.89°. We also mounted

the detection Polaroid on a motor (4.75 RPM) and used a photometer built into a cellular phone

to record the intensity as a function of time. The recorded data was fitted to the expected cos2 (wt

+ Ø) function where Ø represents the optical rotation. The rotation value determined in this

manner was +68.11 ± 1.07. When these values are compared to the literature value, there is a

percentage error of 0.93% (manual) and 2.42% (photometer). The commercial polarimeter

produced an error of 0.3609%. These results showed that the current prototype can achieve

measurements within 0.62° and suggest that some further adjustments are needed to increase the

accuracy and precision of the apparatus. The goal is to achieve an error of less than 0.5%. The

design for the final prototype is nearly completed and concluding data will be collected. Our

estimated price per polarimeter is approximately $100, considerably less than the least expensive

student polarimeters at $475 and the commercial system used above at ≈ $30,000. Once these

conclusive results are obtained, 15 polarimeters will be made for use by undergraduate students

at Concordia University.

 

Introduction

Polarimeters are instruments that are used to measure the optical activity of substances,

mainly chiral molecules. A polarimeter is mainly used in determining the identity of molecules,

because it is a non-destructive method of identification. It does not require any chemical reaction

to be performed during the identification process (Kruss Germany, 2013). Polarimeters have a

number of functions, from the identification of molecules to measuring the rate of chemical

reactions. In the chemical industry, polarimeters are used to measure the purity of substances

based on their optical properties and are also used in the determination of substances in mixtures

(Kruss Germany, 2013). In the food industry, polarimeters are used to distinguish between

different types of nutrients, drugs, steroids, vitamins, and carbohydrates amongst other

substances (Solomons, T. W., 2017). In the sugar industry, quality control is done through the use

of a polarimeter (Kruss Germany, 2013). In the pharmaceutical industry, a polarimeter is used to

monitor the quality and purity (Kruss Germany, 2013). As far as biological applications are

concerned, polarimeters are used in the identification and purity of monomers of carbohydrates,

lipids, nucleic acids, and proteins, based on their optical properties (Solomons, T. W., 2017).

The polarimeter was invented by Étienne-Louis Malus, who also discovered the Malus’

law, also known as Malus law of Polarimetry. Malus’ law states that when plane polarized light

is incident to an analyzer (that is the plane of polarized light is 90o to an analyzer), the intensity

of light transmitted by the analyzer is directly proportional to the square to the cosine of the

angle between polarizer and the plane of light (E. Collett, 2005).

Therefore, according to Malus,

I α cos2 θ

Therefore, I= Io Cos2 θ

According to Malus’ law, the polarizer and the analyser are supposed to be ideal, and

hence, there would be only plane polarized light passing through the analyser.

 

Figure 1: Description of the various parts of a polarimeter, including a light source, the

formation of plane polarized light, the rotation of light through a sample and the analyzer (4). It

also shows the application of Malus’ law in the polarimeter, since there is plane polarized light

passing through an analyser (Bacher, A. D., Dr., April 1, 2016).

The bulb provides a source of light, which travels in all the planes, and the light coming

off the lens is not collimated. Usually Sodium D-line is used, because it produces

monochromatic light, and it is used in literature values (Kruss Germany, 2013). Sodium D-line

emits a wavelength of 598 nm, which is used in a polarimeter to compare experimental values

with literature values. For the explanation, we will assume that the light coming out of the lens is

collimated. Light can be collimated by placing the source of light at the focal point of a

converging lens so that all the rays that pass through the converging lens will be parallel

(Solomons, T. W., 2017).

Figure 2: The formation of collimated light as the scattered beams pass through a converging

lens. It is to be noted that the light source is exactly at the focal point of the converging lens to

obtain fully collimated light (Miller, J., December 30, 2012).

Then, the collimated light is passed through a polarizer to allow it to flow in only one

plane while reflecting the rays that are not parallel to the polarizer. This leads to the formation of

plane-polarized light (Solomons, T. W., 2017).

 

Figure 3: The formation of polarized light as it passes through a polarizer (polarizing

film). It can be noticed that the light moves in different planes before it reaches the polarizer, but

as soon as it passes the polarizer, only light in one plane is allowed to pass through

(AxiomaticNexus., January 26, 2016)

The collimated polarized light passes through the sample cell, which contains a sample

whose optical rotation is to be determined.

Figure 4: Plane polarized light passing through a sample cell. The rotation of light can

be observed for an optically active substance and the rotation depends on the length of the

sample cell (Solomons, T. W., 2017).

A longer sample cell allows the light to rotate more and a wider angle is observed due to

that rotation. As it can be seen from Figure 4, the analyser is a polaroid that is rotatable, and

when the angle rotated by the sample is the same as the angle the analyser rotates, there is

maximum intensity passing through, and a maxima will be observed.

 

Figure 5: The rotation of the polarizer, and the visibility of the plane polarized

ray. Figure 5(a) shows that the polaroid is in the same orientation as the orientation of the

plane polarized light (Solomons, T. W., 2017). Figure 5(b) shows the polaroid that is 90o from

the orientation of the plane polarized light coming at the analyser (Solomons, T. W., 2017).

From Figure 5(a), it is observed that the orientation of the analyser is the same as the

orientation of the plane polarized light. Therefore, a maxima will be observed at that orientation

of the analyser, since there is no reflection of light from the analyser. All the rays can pass

through the analyser. Figure 5(b) shows the analyser at a perpendicular orientation (90o) to the

plane polarized light. No light passes through the analyser, and hence a minima is observed. This

is because all the rays coming to the analyser will be bounced off, and hence nothing will be

observed (Solomons, T. W., 2017).

In order to analyse the optical rotation of substances, the minima is usually observed

since, it is better to analyze a region of minimum intensity rather than the maximum intensity of

light. This is because at low intensity, the photoreceptors in the eyes do not deplete at a high rate,

as it does at high intensity, and hence the difference between different intensities can easily be

noticed (Różanowska, M., & Sarna, T., November 01, 2005). At high intensity, the

photoreceptors in the eyes deplete so fast that small changes in intensity cannot be easily noticed

(Różanowska, M., & Sarna, T., November 01, 2005).

The polarimeter is useful in the way that it allows the precise identification of compounds

that are optically active (meaning that these compounds rotate the plane of polarized light).

Every optically active substance has its own specific rotation (Solomons, T. W., 2017).

Substances can rotate light either in a clockwise manner, or an anticlockwise manner. If the

plane of polarized light is turned clockwise, the substance is known as dextrorotatory, denoted by

(d) or (+). If the substance rotates the plane of polarized light anticlockwise, the substance is

known as levorotatory, denoted by (l) or (-) (Solomons, T. W., 2017).

Optical rotation can be determined by placing an optically active substance sample inside

a sample cell and measuring the angle where there is minimum or no light passing through the

analyzer. Then, from the optical rotation, the specific rotation of the sample can be measured

using the equation:

[�]�� =���

 

Where [�]��  is the specific rotation at temperature T, and wavelength λ, α is the observed

optical rotation, L is the length of the sample cell in decimeters, and C is the concentration of the

sample in g/ml (Solomons, T. W., 2017). The equation is known as the Biot’s law which states

that a compound always has the same specific optical rotation under identical experimental

conditions (same temperature and wavelength).

Hence, using the specific rotation obtained from the rotation of light, the compound can

be identified. The presence of impurities can change the optical rotation of a sample, causing a

large deviation from the specific rotation. Hence deviations of a sample from its specific rotation

allows the identification of impurities in a given sample (Kruss Germany, 2013). Therefore, a

polarimeter is used extensively in different industries for the safety of consumers and the

workers themselves (Kruss Germany, 2013).

D-Glucose has 2 structures in water: Alpha-D-Glucose and Beta-D-Glucose. When L-

Glucose is dissolved in water, Alpha-D-Glucose is mostly formed, and over time, the Alpha-D-

Glucose converts into Beta-D-Glucose until an equilibrium is reached. The conversion between

Alpha-D-Glucose to Beta-D-Glucose occurs because Beta-D-Glucose is more stable and hence

its formation is more favoured (Yamabe, S., & Ishikawa, T., June 01, 1999). This process is

called mutarotation. Mutarotation is defined as the change in the optical rotation because of the

change in the equilibrium between two anomers, when the corresponding stereocenters

interconvert (Yamabe, S., & Ishikawa, T., June 01, 1999). It occurs mainly in cyclic sugars.

Figure 6: The mutarotation of glucose in water, starting from the linear form (middle compound)

to the 2 interchangeable forms of D-Glucose (alpha-D-Glucose and Beta-D-Glucose)

 

The goal of my experiment was to be able to build a polarimeter that is as precise and

accurate as a commercial polarimeter. The final purpose of my experiment was to be able to

observe the mutarotation of D-Glucose over time until it reaches equilibrium. Once accurate and

precise measurements are obtained 15 polarimeters are to be built for the use of undergraduate

students at Concordia in the Organic and Kinetics lab.

 

 

Materials and methods

The experiment was to build a prototypic polarimeter. From the starting prototype,

variations were performed to reduce the cost of production of the apparatus and increase the

accuracy and precision of the apparatus. The prototype design took into account the quality of

data that could be obtained.

In order to understand how a general polarimeter works, a prototype was built using a

25000 mcds LED, a converging lens with a focal length of 2 cm, clamps, stands to hold a sample

cell, polaroids used for the polarizer and analyser, and a goniometer, placed on an optical table.

Data was obtained through manual and computerized measurements. Computerized

measurements were taken using the photometer included in a mobile phone; model: LG G5.

Figure 7: A simplified diagram of the first model of the prototype, showing all the

components that were present for the computerized system.

Figure 8: A simplified diagram of the first model of the prototype, showing all the

components that were present for the manual system.

Different variations were brought to the original prototype in order to increase the

accuracy and precision along the progress of the experiment. The experiments are presented

 

component wise to allow a good understanding of the process employed to work on the original

prototype.

The sample used for the experiments was D-Sucrose, which has an specific optical

rotation of +66.5o (Stevens, E. S., & Duda, C. A., November 01, 1991).

Experiments performed with LEDs

The different hypotheses tested for the effect of varying the intensity on the optical

rotation of a sample, the effect of different distances on the optical rotation of a sample, and the

effect of different wavelengths on the optical rotation of a sample. The effect of a cone angle was

also evaluated on the optical rotation of a sample.

Experiments performed with a converging lens

The hypothesis tested the influence of a converging lens on the optical rotation of a

sample.

Experiments performed with Apertures

The hypotheses tested with apertures were the influence of apertures on optical rotation

of a sample and the effect of lens along with apertures was performed to observe any deviation

from the optical rotation of a sample. The effect of an outlet aperture was also experimented on

to determine if it brought a change to the optical rotation of a sample.

Experiments performed on the sample cells.

The effect of length of sample cell was tested to see if there was any effect on the

optical rotation of a sample. The relative distance of the sample cell from the LED was also

tested to see if there was any effect on the optical rotation of a sample.

Experiments performed on a sample cell holder

The determination of power required to heat up a sample cell to a temperature was to be

determined. The power required to maintain the temperature at a certain temperature was also to

be determined.

These hypotheses were tested through manual and computerized measurements. For

 

manual readings, the analysis was done by reading a vernier scale read in X Y’, where it is read

as X degrees and Y minutes, where 1 minute = ~0.016667o The photometric measurements were

taken on a phone, through an application Physics Toolbox Site™ (Playstore, 2017). The data

collected were sent to an analysis tool, where the data was made to match an expected

cos2(wt+Ø), from Malus’ law, where Ø is the optical rotation of the sample being measured.

Then the specific rotation was measured and compared to literature values.

Procedure:

A concentration of 72 g/L of D - Sucrose (Specific rotation = +66.5o) was filled in a

handmade sample cell. A fresh batch of sucrose solution was prepared before each experiment.

Experiments performed with LEDs

To test the influence of different light intensities, the voltage across a 25000 mcds LED

was varied and none of the components on the optical table were allowed to move.

To test for the influence of different distances, the LED and a converging lens were

placed on a sliding mechanism, in order to allow easy movement. The LED was placed at 5 cm,

10 cm, and 20 cm. All the other mechanisms were not allowed to moved.

In order to test for the different wavelengths affecting the optical rotation, a 598 nm and a

579 nm LED were used. They were placed at a fixed position from the sample cell. There was no

use of converging lens and all the other components were not allowed to move.

The cone angle was measured using different LEDs. A 3190 mcds LED with cone angle

30o was used, a 8900 mcds LED with cone angle 20o was used and a LED of 25000 mcds with a

cone angle of 8o was used.

Experiments performed with a converging lens:

The influence of a lens was tested by mounting and unmounting the converging lens,

where the optical rotation was measured. An LED of 25000 mcds was used for computerized

measurement and an LED of 3190 mcds was used for manual measurements. All the other

components on the optical table were not moved.

 

Experiments performed with Apertures:

The influence of apertures was tested by rotating the aperture 0 and 90o. 0o means that the

aperture was parallel to the direction of light flow and hence light did not flow through the

aperture. When the aperture was at an angle of 90o, it was perpendicular to the flow of light and

the light travelled through it. Hence data was recorded when the aperture was at 0 o and 90o.

The effect of an outlet aperture was tested by placing an aperture at the end of the sample

cell so that only the on-axial ray passed through. All the components were fixed. The aperture

was at 90o and the outlet aperture was also at 90o

Experiments performed on the sample cells

Different lengths of sample cells were used. Sample cells of 10 cm, 13 cm and 20 cm

were used. A mark was placed on a sample cell holder in order to place the sample at the same

position each time measurements were repeated. No components of the prototype were moved.

The distance of the sample position from the LED was also moved along the x-axis of the

sample cell holder to observe any change in optical rotation of a sample. There was no change in

the setup of the prototype.

Experiments performed on a sample cell holder:

A “rough focus” experiment was performed first to determine the power required to heat

the sample cell to 30o C. Another experiment was performed to determine the exact power

required to heat up a 20 cm plastic sample cell up to 30o C in a suitable time. Also, the power

required to maintain the temperature for 90 minutes at 30o C was determined.

Number of trials:

All data collections performed manually was repeated 15 times, and computerized

measurements were collected for 1 minute, to allow accuracy in the measurement. Computerized

measurements were repeated to obtain 2 trials.

Measurement of Mutarotation of glucose:

The measurement of the mutarotation of glucose was performed by measuring the optical

rotation over a period of time. Linear Glucose was dissolved in water and as soon as the glucose

 

was mixed with water, a timer was started. Then the solution was transferred to a sample cell and

the solution was heated up to a fixed temperature. Measurements were taken at an interval of 2

minutes and the temperature was set at 30o C for measurements (Laboratory Experiments,

Determine the Kinetics of Mutarotation of D-Glucose, 2017).

Statistical Significance of results:

Data was found to be significant if the percentage error was below 2% of literature value

of the sample. Comparison was also used to compare data to find the more accurate and precise

measurements, and taking the changes into account. No statistical analysis was performed.

Results:

Commercial Polarimeter measurement: Perkin Elmer 343 Polarimeter

Specific Rotation: +66.26o

Standard Deviation (+/-): 0.0068o

Percentage Error (%) 0.3609 %

Table 1: The specific rotation of sucrose obtained from a commercialized polarimeter. The

standard deviation represents the inaccuracy of the polarimeter. The percentage error

represents the deviation from literature values.

 

 

Starting Prototype Measurements:

Computerized measurements:

Specific Rotation: +68.11o

Standard Deviation (+/-): 1.07o

Percentage Error (%): 2.42 %

Table 2: The specific rotation of sucrose, obtained through computerized measurements,

performed on the starting prototype. The standard deviation represents the inaccuracy of the

measurement. The percentage error represents the precision of the measurement.

Manual Measurements:

Specific Rotation: +67.12o

Standard Deviation (+/-): 0.89o

Percentage Error (%) 0.932 %

Table 3: The specific rotation of sucrose, obtained through manual measurements, performed on

the starting prototype. The standard deviation represents the inaccuracy of the measurement.

The percentage error represents the precision of the measurement.

Testing Different components of the prototype:

Factor: Measurement(s): Percentage Error (%) in measurements #

Intensity* Intensity 1(3100 mcds***): 1.31%

Intensity 2(8930 mcds***): 1.4 %

Intensity 3(25000 mcds***): 1.36 %

Wavelength 1(598 nm****): 0 % **

Wavelength 2(579 nm****): 0.41%

 

Converging lens With: 1.58 %

Without: 1.47 %

Aperture With: 1.37 %

Without: 0.61 %

Sample Cell

(Size)

Small (13 cm): 13.7 %

Long (20.4 cm): 2.41 %

Table 4: The different components of the polarimeter and their accuracy from literature value of

sucrose. #The percentage error represents the percentage error in both Manual measurements and

Computerized measurements.

*The intensity had the same effect as a change in distance.

** Assumed to influence the Optical rotation since wavelength is used in many literature values.

Figure 9: The precise measurement of power required to maintain the power at 30o C. The

power required was 1.653 Watts and it can be seen that the results fluctuate around 35o C.

 

Final Prototype:

Figure 10: A simplified diagram of the final model of the prototype, showing all the components

that were present, adapted for manual measurements.

Figure 11: A simplified diagram of the final model of the prototype, showing all the components

that were present, adapted for computerized measurements.

Final Prototype Measurements:

D - Sucrose:

Computerized Measurements:

Specific Rotation: +67.3o

Standard Deviation (+/-): 0.16o

Percentage Error (%) 1.29%

Table 4: The specific rotation of sucrose, obtained through computerized measurements,

performed on the final prototype. The standard deviation represents the inaccuracy of the

measurement. The percentage error represents the precision of the measurement.

 

Manual Measurements:

Specific Rotation: +65.6o

Standard Deviation (+/-): 0.15o

Percentage Error (%) 1.37 %

Table 5: The specific rotation of sucrose, obtained through manual measurements, performed on

the final prototype. The standard deviation represents the inaccuracy of the measurement. The

percentage error represents the precision of the measurement.

Mutarotation of Glucose:

Commercialized Measurements:

Figure 12(a): Perkin Elmer 343 Polarimeter. The diagram shows the mutarotation of glucose

(O) over time (minutes). The R2-Value = 0.9903

 

Figure 12(b): Rudolph Research Analytical, Autopol III. The diagram shows the mutarotation of

glucose (O) over time (minutes). The R2-Value = 0.9892

Manual Measurement:

Figure 13: Manual readings on the Prototype for measuring the mutarotation of glucose. The

R2-Value= 0.9817

 

Power Required to maintain temperature at 30o C = 1.653 Watts

Computerized Measurements:

No Computerized measurements were taken for the observation of the mutarotation of glucose.

This is because the optical rotation is always shifting. Since computerized measurement requires

more time (>60 seconds) than the manual reading (~5 seconds), no measurements were

performed through computerized measurements.

 

 

Discussion:

The goal of the experiment was to build a polarimeter that is accurate and precise.

According to the results obtained, the accuracy and the precision of the prototype can be

increased.

For the LEDs testing, we found that the intensity had no effect on the optical rotation of

the sample. From Table 4, the accuracy of the measurements was approximately 1.3 - 1.4% off.

Throughout the data collection, it was recommended to use a 25,000 mcds LED at 55 mA and a

voltage of 5.5 V for computerized measurements and a 3190 mcds LED at 22 mA and a voltage

of 2.2 V for manual measurements. The distance had no effect on the optical rotation, but it was

found at 13 cm, there was a minimum of light bouncing off the walls of the sample cell. The

wavelengths tested showed no effect on the optical rotation of the sample, since there was a

difference of 0.41% between the different measurements. Two wavelengths which are relatively

close (598 nm and 579 nm) were used and the results obtained were nearly identical. Therefore,

the effect of wavelength on the optical rotation of a sample was assumed to be null. When the

cone angle effect was tested, it was found that it did not affect the optical rotation. It was,

however, observed that a smaller cone angle allowed for better measurement by allowing less

light bouncing off the walls of the sample cell.

The use of converging lens did not allow better reading because of the bouncing of light

rays off the wall of sample cells. It was found that the use of collimated light was not necessary.

This is because the percentage error in the measurement of the optical rotation obtained through

converging lens (1.58%) is the same as the precision obtained without a converging lens

(1.47%). The use of converging lens after the sample cell allowed better computerized

measurements as the rays were focussed on the photometer. No converging lens was required for

manual measurements.

An aperture was used to reduce the bouncing of light on the walls of the sample cell. The

25000 mcds LED had a small cone angle and a high intensity. Therefore, for low intensity LEDs

an aperture was used to reduce the cone angle of the light flowing through the apparatus. It was

found that the aperture used had no effect on the optical rotation of the sample. Table 4 shows

that measurements taken without aperture are more precise than when an aperture was used. As

the experiment progressed, it was found that the sample which was used when the aperture was

tested was contaminated with bacterial colonies, leading to the increased percentage error. The

 

use of an aperture was not recommended for computerized measurements. This is because it does

not allow enough light to pass through, even with the use of maximum intensity lighting (25000

mcds at 7.77 V, and 7 mA) that could be used for measurements. This is because the aperture

prevented a large beam of light from passing through the sample cell. The aperture allowed only

the on-axial ray and restricted any residual light to pass through the sample cell. Given that the

photometer was a small sensor, no measurements could be obtained. For manual measurements,

the aperture allows for better accuracy measurements to be taken as the absence of residual rays

lowers the rate at which photoreceptors in the eyes were depleted. Therefore, minima were easily

observed without an aperture. An outlet aperture had no effect on the optical rotation of the

sample, nor on the quality of measuring the optical rotation of the sample. It was not used in the

polarimeter for measurements.

The sample cell influenced the optical rotation of the sample. It was found that a sample

cell of 20 cm provided a better accuracy (Standard deviation: 2.41%) and precision than a 13-cm

sample cell (13.7%).The improvement in accuracy was mainly because of Malus’s law, where

when light travels in a longer path in a sample, the angle of rotation also increases. An increase

in the angle of the optical rotation decreased the inaccuracy in the measurements. Therefore,

using a long sample cell provided better accuracy. Unfortunately since there are limits, such as,

the length and limitation of materials allowed for the polarimeter to be build, the sample cell

could not be made longer than 20 cm. It was found, through observation, that the sample cell’s

material had no effect on the optical rotation of the sample, provided that there was a smooth

surface inside the wall. This is because the light that bounced off the walls of the sample cell

would be reflected towards the goniometer. When computerized measurements were being

taken, the reflection off the walls of the sample cell could not be prevented/reduced and, this was

recorded by the photometer, leading to a source of error.

To determine the power required to heat the sample cell holder to 30o C., a rough focus

experiment was initially performed in order to determine approximate power required to heat up

the sample cell from room temperature to 30o C. Thermocouples were then used to determine the

exact power required, and the data was recorded for 130 minutes starting at room temperature, as

described in Figure 9. It was found that a current of 0.57 A was required at a voltage of 2.9 V to

stabilise the temperature at 30o C. Therefore, the power required to maintain the temperature of

the sample cell holder and the sample cell was 1.653 Watts.

 

There were numerous sources of error that were present throughout the measurements.

The moving of the different components during different experiments was one of the sources.

Another source of error is that measurement was taken over several days for manual readings.

This means that at different days, the eyes adapted at different intensities. Also, the computerized

measurements were analysed by performing trial and error, meaning that the values obtained

were obtained by applying limiting factors on excel. Based on the limiting factors, Excel found

random values that fit the parameters. Various ways to limit the deviation of the data was to

further restrict the parameters. In order to do so, the specific rotation of a sample had to be

known in order to be used as comparison. The repetition of the measurements allowed a better

result. Hence the value obtained for the optical rotation was not very accurate, giving an

approximate value. Other sources of error included the inability to ensure the stability of the

different components of the prototype over the duration of data collection. The sample inside the

sample cell might be contaminated by bacteria since the sample cell might have not been

properly washed after the use of the sample cell. The bacteria would be able to survive since

there was enough glucose to allow a culture to grow. A sample left for a week turned cloudy, due

to bacterial replication in the sample cell, hence showing that bacteria replicated over time. Due

to different hypothesis testing, some components were displaced sometimes so that when they

were replaced, they might not be placed at the same position as before. Also, there is a possibility

that the minima was not properly found, which would lead to an increase in uncertainty. There is

also the possibility that a residual ray was observed during the data collections for manual

measurements. Data collected through the photometer might have been subjected to recording

the residual rays, and therefore, it would induce uncertainties during the data analysis.

The various sources of error were reduced by having only one person taking the manual

measurements. This reduces the probability that the minimum intensity might be observed

differently by different individuals. After each set of data collection, the sample cell was emptied

and cleaned with distilled water and allowed to dry overnight to reduce the risk of contamination

overnight. Also, to make sure that the components did not move, the components were mounted

on the optical table to reduce the movement of the different components of the polarimeters.

Next, to reduce the percentage error in computerized measurements, a 25000 mcds LED was

used, since it has a small cone angle. Also, a converging lens was used near the photometer, to

reduce the inaccuracy of the measurements. For manual measurements being recorded, the set of

 

data collection was performed to evaluate the accuracy of the measurements that were being

taken.

The experiment is still ongoing to reduce the inaccuracy and increase the precision of the

measurements. It is expected that the price of the apparatus will not exceed $150, since all the

materials used are easily available and the materials are within the purchasing power of people.

The estimated price takes into consideration the LED, $ 1.50, Polaroid film, $ 3.00, sample cell

windows $ 7.00 each, goniometer, $ 10.00, housing materials, $ 20.00, temperature control, $

10.00, and converging lens, $ 30.00. This is less expensive than the current least expensive

model of student polarimeter at Loyola Concordia, which is estimated to cost around $ 450.00,

and the commercial systems used cost approximately $ 30,000.00.

Acknowledgements

A special thanks to Dr. Cameron Skinner who gave me the opportunity to work in his lab and

take part of the research. I would also like to thank Dr. Cameron Skinner, Dr. Christopher Gregg,

Dr. Louis Cuccia, and Mrs. Ninoosh Amin who have mentored and guided me through every

step of the way.

 

 

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7. Stevens, E. S., & Duda, C. A. (November 01, 1991). Solution conformation of sucrose from optical rotation. Journal of the American Chemical Society, 113, 23, 8622-8627.

8. Vieyra Software. (April 30, 2017). Physics Toolbox Sensor Suite, vers. 1.6.8, Google Play Store.

9. Yamabe, S., & Ishikawa, T. (June 01, 1999). Theoretical Study of Mutarotation of Glucose. The Journal of Organic Chemistry, 64, 12, 4519-4524.

Picture References:

1. Bacher, A. D., Dr. (2016, April 1). Polarimeter. Retrieved May 10, 2017, from http://www.chem.ucla.edu/~bacher/General/30BL/tips/Polarimetry.html

2. Miller, J. (December 30, 2012). The dice are Loaded: Probability Waves, from http://www.thephysicsmill.com/2012/12/30/the-dice-are-loaded-probability-waves/

3. AxiomaticNexus. (January 26, 2016). Physics StackExchange, from https://physics.stackexchange.com/questions/231962/linear-polarized-3d-glasses-and-the-physical-shape-of-light-waves

4. Solomons, T. W. (2017). Organic Chemistry. Chapter 5.8, Properties of Enantiomers, Optical Rotation S.l.: John Wiley & Sons.

Appendix:

1) Refer to Excel file labelled “LED_all_measurements.xlsx”, Available on:

 

https://docs.google.com/spreadsheets/d/1za5FKSD1EhKFNstmIK_maemJSqRPs5

M0WI4-6RktWfU/edit?usp=sharing

2) Refer to Excel file labelled “Temperature_Measurements.xlsx”, Available on:

https://docs.google.com/spreadsheets/d/1p71EB3YP_7uipD3ffCOnZ-

QWQ3iR6aJRHy1SqYPeY8w/edit?usp=sharing

3) Refer to Excel file labelled “Measurements_w/_and_w/o_aperture.xlsx”,

Available on:

https://docs.google.com/spreadsheets/d/1l0xaHIcgUDi1qmcdlF0tx788hsgLfw9W

c7Nf0s2Z3iE/edit?usp=sharing

4) Refer to Excel file labelled “Final_Mutarotation_of_glucose”, Available on:

https://docs.google.com/spreadsheets/d/1gE_1Maf7_4USYU9h3RoAadd7F8HTH

iGKQzjvqnPORRg/edit?usp=sharing

5) Refer to Excel file labelled “Readings_of_Sucrose_S”, Available on:

https://docs.google.com/spreadsheets/d/1eyuyHCgUUjQXcPYbI77ff7XuSlLScyI

w1kjgmuTh0V8/edit?usp=sharing

6) Sample of Graphs obtained from different Computerized measurements:

Figure 14: The sample of computerized measurement obtained from analysis.

7) Refer to Excel file labelled

“Organic_Laboratory_Measurement_of_Mutarotation_of_Glucose.xslx”,

Available on: https://docs.google.com/spreadsheets/d/144TojKb4EDaDPS-

s4ZA0plsB2CeT74EQMpdbWg9gVAk/edit?usp=sharing