Presented by: Md Tauquir Alam & Abida Department of Pharmaceutical Chemistry Faculty of Pharmacy Northern Border University

1. POLARIMETER: AN INTRODUCTION AND DEMONSTRATION
Presented by
Md Tauquir Alam
Department of Pharmaceutical Chemistry
Faculty of Pharmacy
Northern Border University

2. CONTENTS
 Introduction
 Principle
 Instrumentation
 Applications

3. INTRODUCTION
 Polarimetry → It may be referred as the study of the
rotation of plane polarized light by optically active
substance.
 This is a type of qualitative and quantitative analytical
technique as both identification and estimation of the
compound can be done.

4. INTRODUCTION
It has been found that magnitude of rotation depend
upon the following factors:
1. Nature of Substance
2. Length of liquid column
3. Concentration of the solution
4. Nature of the solvent
5. Temperature of the solution
6. Wavelength of the light used

5. INTRODUCTION
Types of molecules analysed by Polarimetry:
1. Molecule must be Optically active.
2. Optically Active molecule contain asymmetric carbon
atom.
Dextro= right designated by ‘d’, (+), clockwise
Levo= left designated by ‘l’, (-), counterclockwise

6. PRINCIPLE
 Instrument measures the rotation of polarized light as it
passes through an optically active substance and the
tendency of the molecule to rotate the plane polarized
light towards clock-wise or anti-clock wise direction
whose extent of the rotation can be measured.

7.  Polarimetry is a sensitive, non-destructive technique for
measuring the optical activity exhibited by inorganic and
organic compounds.
 A compound is considered to be optically active if the
plane of linear polarized light is rotated when passing
through it. This change of polarization angle is known as
optical rotation and measured with the MCP. Many
concentration scales derive from the optical rotation

8. INSTRUMENTATION
 Polarimeter → It is a scientific instruments used to
measure the angle of rotation caused by passing
polarized light through an optically active substance.
Optical activity may be detected & measured by
Polarimeter

9. INSTRUMENTATION
The benefits of Anton Paar’s polarimeters are:
 Multi-wavelength option meets the requirements of
pharmacopoeia.
 Automatic detection of the sample cell ensures complete
traceability.
 Automatic transfer of calibration and adjustment data from
the quartz control plate ensures error-free calibration and
adjustment use of certified calibration standards.

10. INSTRUMENTATION
 Automated checks and adjustment procedures.
 Measurement of light and strongly colored samples with
the same quality via self-adjusting light intensity.
 Built-in Peltier temperature control Wide range of
sample cells Numerous communication ports.
 Compliance with national/international standards
Wireless Toolmaster TM function.

11. INSTRUMENTATION

12. Polarimeter tube

16. Working principle
 To measure the optical rotation, a light beam from a
lamp inside the polarimeter first passes through a fixed
polarizer in order to obtain a defined orientation of the
plane of polarization.The polarized light then passes
through the sample. Its plane polarization becomes
rotated if the sample is optically active.The light with
the rotated plane of polarization passes through an
analyzer, which is a second polarization flter.

17. Working principle
 The transmitted light behind the analyzer is detected with a photodiode. The
analyzer is rotated automatically until the transmission minimum is reached.
This is at 90° to the plane of polarization after the sample and is therefore a
direct measure of the optical rotation.
 The right wavelength for the measurement is precisely selected
by an interference flter or by a flter wheel with flters for several wavelengths
positioned in the beam in front of the detector.
To further enhance the angular resolution, the polarized light passes through
electromagnetic coils, which superimpose an
oscillation onto the plane of polarization by means of the Faraday effect.

22. APPLICATIONS
 Determination of optical rotation is the method of choice
to ensure use of the correct and optically pure
pharmaceutical substances in all areas of pharmaceutical
production, quality control and R&D.
 This is important for chiral drugs, for example, as some
enantiomers can be inactive or even toxic. The optical
rotation is a measure of the concentration of optically
active substances and therefore directly proportional to
the sample concentration and path length of the used
sample tube.

23. APPLICATIONS
 Food, beverage and pharmaceutical industries
Concentration and purity measurements are especially
important to determine product or ingredient quality in the
food & beverage and pharmaceutical industries. Samples that
display specific rotations that can be calculated for purity with
a polarimeter include: Steroids, Diuretics, Antibiotics,
Narcotics, Vitamins, Analgesics, Amino acids, Essential oils,
Polymers.

24. APPLICATIONS
 Sugar industry: Polarimeters are used in the sugar
industry for determining the quality of both juice from
sugar cane and the refined sucrose. Often, the sugar
refineries use a modified polarimeter with a flow cell
called a saccharimeter.
 Chemical industry:
Many chemicals exhibit a specific rotation as a unique
property (an intensive property like refractive index or
Specific gravity) which can be used to distinguish it.

25. Quantitative application
If the specific rotation of sample is known its concentration in
the solution can be estimated.
Qualitative application.
Optical activity is the only parameter available for
distinguishing between D and L isomeric forms.
Saccharimetry
Important practical application of polarimetr is determination
of high conc. of sugars by visual saccharimeters called
POLAROSCOPES.
APPLICATIONS

26. Precautions
 Polarimeter tube should be filled in such a way so as to avoid
air bubbles.
 Before taking the reading clean the Polarimeter tube with
tissue paper.
 Set the field telescope for better observation.
 The optical elements must be cleaned and at exact
alignment.
 Tighten the end plate with caps and seal so as to make it
leak proof.
 Operate the touchscreen with clean and dry finger only
 Never use any sharp objects.
 Operate the touchscreen with gentle fingertip pressure only.

27. To describe the standard Operating procedure (SOP) of Polarimeter
PROCEDURE:
 Switch ‘ON’ the mains.
Wait till initializing of the instrument to complete
 The progress bar at the bottom of the content area currently measuring (Red) measurement is finished (Green).
 Important function and message by using quick access bar
Rinse the polarimeter tube with distilled water.
 Fill the sample solution in the polarimeter tube at the temperature specified in the monograph / specification.
 Clean the sides of the tube with tissue paper.
 If any air bubble comes then it must be trapped in center of polarimeter tube.
 Keep the polarimeter tube in its place in the polarimeter.
 Adjust the according to specified in monogrpah (Optical rotation, specifc rotation)
 Observe and wait the light of the screen red to Green
 Adjust the weight taken during solution.
 Automatically result will display on the screen .
 Repeat the operation two times for accurate result.
 Consider the average reading.
 Note down the reading Mark it as + (plus) reading ,and – (minus) reading .
 Remove the polarimeter tube from the polarimeter.
 Discard the solution from the polarimeter tube.
 Clean the tube and the sides of glass with tissue paper
 Switch ‘Off’ the mains.
 Clean the polarimeter tube with distilled water if solutions are prepared in polar solution or clean the polarimeter tube with
methanol or ether if solvent is non-polar.
 Keep the tube in tube box.
 Enter the details in the logbook.

28. Thank you