Polarimetry

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Polarimetry

  1. 1. POLARIMETRY
  2. 2. POLARIMETRY <ul><li>Presented By - </li></ul><ul><li>Mr. Shaise Jacob </li></ul><ul><li>Faculty </li></ul><ul><li>Nirmala College of Pharmacy </li></ul><ul><li>Muvattupuzha, Kerala </li></ul><ul><li>India </li></ul><ul><li>Email – jacobshaise@gmail.com </li></ul>
  3. 3. <ul><li>The term Polarimetry may be defined as the study of the rotation of polarised light by transparent substance. </li></ul><ul><li>Optical rotatory power is useful for » </li></ul><ul><li>Qualitative analysis </li></ul><ul><li>Quantitative analysis </li></ul><ul><li>Elucidation of chemical structures </li></ul><ul><li>An ordinary light usually vibrates in all the planes -> UNPOLARISED LIGHT </li></ul>
  4. 6. <ul><li>The vibrations may all be restricted to one direction only, in the perpendicular plane -> PLANE POLARIZED LIGHT </li></ul><ul><li>Unpolarised light gets converted into a plane-polarized light by simply passing it through a lens called a NICOL Prism. (after William Nicol – the inventor ) </li></ul><ul><li>NICOL Prism – Iceland Spar </li></ul><ul><li>Calcite ( CaCO 3 form ) </li></ul><ul><li>(or) Polaroid </li></ul>
  5. 7. <ul><li>A plane polarized light which consists of two components of fixed magnitude rotating in opposite directions to one another; </li></ul><ul><li>The right circulatory polarized light </li></ul><ul><li>The left circulatory polarized light </li></ul><ul><li>Plane polarized light is the vector sum of these two components </li></ul>
  6. 8. THEORY <ul><li>An optically active substance is one that rotates the plane of polarized light </li></ul><ul><li>(1) Lactic acid </li></ul>
  7. 9. <ul><li>Latin : Dexter = right </li></ul><ul><li>designated by ‘d’ </li></ul><ul><li>Latin : Laevus = left </li></ul><ul><li>designated by ‘l’ </li></ul><ul><li>OPTICAL ACTIVITY </li></ul><ul><li>When a certain organic liquids, solutions (sugar) or quartz crystals are placed in the path of plane polarized light, the plane of polarization is rotated </li></ul>
  8. 10. Magnitude of rotation depend upon <ul><li>Nature of the substance </li></ul><ul><li>Length of liquid column </li></ul><ul><li>Conc. Of the solution </li></ul><ul><li>Nature of the solvent </li></ul><ul><li>Temperature of the solution </li></ul><ul><li>WL of the light used </li></ul><ul><li>The rotatory power of a given solution is generally expressed as Specific rotation </li></ul>
  9. 11. <ul><li>a – observed angle of rotation </li></ul><ul><li>L – length in decimeters </li></ul><ul><li>C - grams of substance in 100ml of solution </li></ul><ul><li>INSTRUMENTATION </li></ul><ul><li>Optical activity may be detected & measured by an instrument -> Polarimeter </li></ul>
  10. 12. <ul><li>Light source – Sodium vapor lamp </li></ul><ul><li>Analyzer – another Nicol prism aligned to intercept the linearly polarized ray as it emerges from the sample solution </li></ul>
  11. 15. <ul><li>Determination of optical activity of Pharmaceutical substances </li></ul><ul><li>Optical rotation </li></ul><ul><li>Specific optical rotation </li></ul><ul><li>noting the angle through which the plane of polarization is rotated. </li></ul>
  12. 16. Applications <ul><li>Identification </li></ul><ul><li>Determination of O.A compounds </li></ul><ul><li>Quantitative – sugar industry (sucrose) </li></ul><ul><li>O.A is the only one parameter, for distinguishing b/w D & L isomeric forms </li></ul><ul><li>SACCHARIMETRY </li></ul><ul><li>» important practical application of polarimetry </li></ul><ul><li>» determination of high conc. of sugars </li></ul><ul><li>» visual saccharimeters called POLAROSCOPES </li></ul>

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