Polarimetry SAP.ppt
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Polarimetry is a technique that measures the rotation of polarized light as it passes through an optically active substance. Plane polarized light is produced when unpolarized light passes through a polarizer such as a Nicol prism. Optically active molecules rotate the plane of polarized light due to the presence of chiral centers. The degree of rotation depends on factors like concentration and temperature. A polarimeter instrument contains a light source, polarizer, sample cell, and analyzer to measure the angle of rotation. Polarimetry has applications in determining concentrations and distinguishing chiral isomers.
![• The Rotatory Power of a given solution is generally
expressed as specific rotation. It is the number of
degress of rotation of plane polarized light produced by
one gram of the substance per 100 ml. The measurement
is carried out at temp using sodium light. The Specific
rotation can be Calculated by the following relation:
 [α] = specific rotation, T = temperature,
 λ = wavelength, θ= optical rotation,
 c = concentration in g/100ml, l = optical path length in
dm.](https://image.slidesharecdn.com/polarimetrysap-230824061247-beac4e8a/85/Polarimetry-SAP-ppt-9-320.jpg)
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Polarimetry SAP.ppt
- 1. POLARIMETRY
- 2. A. Introduction B. Plane Polarised Light C. Optical Activity D. Theory of Optical Activity E. Polarimeter F. Applications
- 3. A. INTRODUCTION • Polarimetry is one of the important instrumental methods employed in analysis. This measures the rotation of the polarized light as it passes through an optically active compound. This technique involves the measurement of change in the direction of vibration of polarized light when interact with an optically active compound. A substance is said to be optically active if it rotates the plane of the polarized light.
- 4. B. PLANE POLARISED LIGHT • According to wave theory of light, an ordinary ray light is considered to be vibrating in all planes at right angle to the direction of propagation. If this ordinary ray of light is passed through a Nicol prism, the emergent ray has its vibration only in one plane. This light having wave motion in only one plane is known as Plane Polarised Light. • NICOL Prism – Iceland Spar Calcite ( CaCO3 form ) (or) Polaroid
- 7. • A plane polarized light which consists of two components of fixed magnitude rotating in opposite directions to one another; • The right circulatory polarized light • The left circulatory polarized light • Plane polarized light is the vector sum of these two components
- 8. C. OPTICALACTIVITY • Definition • It Has find that magnitude of rotation depend upon the following factors: 1. Nature of Substance 2. Length of liquid column ( l ) through which light passes. 3. Concentration of the solution. 4. Nature of the solvent. 5. Temperature of the solution (t) 6. Wavelength of the light used
- 9. • The Rotatory Power of a given solution is generally expressed as specific rotation. It is the number of degress of rotation of plane polarized light produced by one gram of the substance per 100 ml. The measurement is carried out at temp using sodium light. The Specific rotation can be Calculated by the following relation:  [α] = specific rotation, T = temperature,  λ = wavelength, θ= optical rotation,  c = concentration in g/100ml, l = optical path length in dm.
- 10. • Types of molecules analysed by Polarimetry: 1. Molecule must be Optically active. 2. Optically Active molecule contain asymmetric carbon atom.
- 11. D. Theory of Optical Activity • An optically active substance is one that rotates the plane of polarized light Example: (1) Lactic acid Dextro= right designated by ‘d’, (+), clockwise Levo= left designated by ‘l’, (-), counterclockwise • Configuration:
- 12. E. INSTRUMENTATION  Optical activity may be detected & measured by an instrument → Polarimeter
- 14. • Light source – Sodium vapor lamp • Analyzer– another Nicol prism aligned to intercept the linearly polarized ray as it emerges from the sample solution • A polarimeter consists of a polarized Light source – Sodium vapor lamp, Polarizer –quartz prism material and Analyzer – Nicol prism aligned to intercept the linearly polarized ray as it emerges from the sample solution, a graduated circle- to measure the rotation angle, and sample tubes.
- 15. POLARIMETER
- 17. F. APPLICATIONS 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 polarimetry  determination of high conc. of sugars  visual saccharimeters called POLAROSCOPES
- 18. Thank You