Polarimetry

Polarimetry

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  POLARIMETRY
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  POLARIMETRY Presented By- Mr. Shaise Jacob Faculty Nirmala College of Pharmacy Muvattupuzha, Kerala India Email – [email protected]
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  The term Polarimetrymay be defined as the study of the rotation of polarised light by transparent substance. Optical rotatory power is useful for » Qualitative analysis Quantitative analysis Elucidation of chemical structures An ordinary light usually vibrates in all the planes -> UNPOLARISED LIGHT
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  The vibrations mayall be restricted to one direction only, in the perpendicular plane -> PLANE POLARIZED LIGHT 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 ) NICOL Prism – Iceland Spar Calcite ( CaCO 3 form ) (or) Polaroid
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  A plane polarizedlight 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
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  THEORY An opticallyactive substance is one that rotates the plane of polarized light (1) Lactic acid
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  Latin : Dexter= right designated by ‘d’ Latin : Laevus = left designated by ‘l’ OPTICAL ACTIVITY 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
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  Magnitude of rotationdepend upon Nature of the substance Length of liquid column Conc. Of the solution Nature of the solvent Temperature of the solution WL of the light used The rotatory power of a given solution is generally expressed as Specific rotation
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  a –observed angle of rotation L – length in decimeters C - grams of substance in 100ml of solution INSTRUMENTATION Optical activity may be detected & measured by an instrument -> Polarimeter
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  Light source – Sodium vapor lamp Analyzer – another Nicol prism aligned to intercept the linearly polarized ray as it emerges from the sample solution
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  Determination of opticalactivity of Pharmaceutical substances Optical rotation Specific optical rotation noting the angle through which the plane of polarization is rotated.
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  Applications Identification Determinationof O.A compounds Quantitative – sugar industry (sucrose) O.A is the only one parameter, for distinguishing b/w D & L isomeric forms SACCHARIMETRY » important practical application of polarimetry » determination of high conc. of sugars » visual saccharimeters called POLAROSCOPES
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