Polarimetry SAP.ppt

Principle
Instrumentation
Applications

1. POLARIMETRY

2. A.Introduction
B.Plane Polarised Light
C.Optical Activity
D.Theory of Optical Activity
E.Polarimeter
F.Applications

3. A. INTRODUCTION
•Polarimetryisoneoftheimportantinstrumentalmethods
employedinanalysis.Thismeasurestherotationofthe
polarizedlightasitpassesthroughanopticallyactive
compound.Thistechniqueinvolvesthemeasurementof
changeinthedirectionofvibrationofpolarizedlight
wheninteractwithanopticallyactivecompound.A
substanceissaidtobeopticallyactiveifitrotatestheplane
ofthepolarizedlight.

4. B. PLANE POLARISED LIGHT
•Accordingtowavetheoryoflight,anordinaryray
lightisconsideredtobevibratinginallplanesatright
angletothedirectionofpropagation.Ifthisordinary
rayoflightispassedthroughaNicolprism,the
emergentrayhasitsvibrationonlyinoneplane.This
lighthavingwavemotioninonlyoneplaneisknown
asPlanePolarisedLight.
•NICOL Prism –Iceland Spar
Calcite ( CaCO3 form )
(or) Polaroid

7. •Aplanepolarizedlightwhichconsistsoftwocomponentsoffixed
magnituderotatinginoppositedirectionstooneanother;
•Therightcirculatorypolarizedlight
•Theleftcirculatorypolarizedlight
•Planepolarizedlightisthevectorsumofthesetwocomponents

8. C. OPTICAL ACTIVITY
•Definition
•ItHasfindthatmagnitudeofrotationdependuponthe
followingfactors:
1.NatureofSubstance
2.Lengthofliquidcolumn(l)throughwhichlight
passes.
3.Concentrationofthesolution.
4.Natureofthesolvent.
5.Temperatureofthesolution(t)
6.Wavelengthofthelightused

9. •TheRotatoryPowerofagivensolutionisgenerally
expressedasspecificrotation.Itisthenumberof
degressofrotationofplanepolarizedlightproducedby
onegramofthesubstanceper100ml.Themeasurement
iscarriedoutattempusingsodiumlight.TheSpecific
rotationcanbeCalculatedbythefollowingrelation:
[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 analysedby 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
Opticalactivitymaybedetected&measuredbyan
instrument→Polarimeter

14. •Lightsource–Sodiumvaporlamp
•Analyzer–anotherNicolprismalignedtointerceptthe
linearlypolarizedrayasitemergesfromthesample
solution
•ApolarimeterconsistsofapolarizedLightsource–
Sodiumvaporlamp,Polarizer–quartzprismmaterialand
Analyzer–Nicolprismalignedtointerceptthelinearly
polarizedrayasitemergesfromthesamplesolution,a
graduatedcircle-tomeasuretherotationangle,and
sampletubes.

15. POLARIMETER

16. Jasco-p-2000-digital-polarimeter

17. F. APPLICATIONS
Quantitativeapplication
Ifthespecificrotationofsampleisknownits
concentrationinthesolutioncanbeestimated.
Qualitativeapplication.
Opticalactivityistheonlyparameteravailablefor
distinguishingbetweenDandLisomericforms.
Saccharimetry
importantpracticalapplicationofpolarimetry
determinationofhighconc.ofsugars
visualsaccharimeterscalledPOLAROSCOPES

18. Thank You