WELCOME S.Y.B.Sc. (Analytical Chemistry) U.V.& Visible Spectroscopy By Prof.Bhagure G.R.

Reason for deviation 1) Real Deviation 2) Chemical Deviation 3) Instrumental Deviation 1) Real Deviation:- Concentration should be below 0.01M At higher concentration average distance between molecule decreases which affect in absorbance. Molar absorptivity changes because at higher concentration refractive index of solution changes

PERIODIC TABLE OF ELEMENTS

2) Chemical Deviation:- This deviation occurs when solute present in solution undergoes association, dissociation or ionization. Association: Diluting or concentrating the solution of Benzyl alcohol in chloroform undergoes polymerization. 4C6H5CH2OH---->(C6H5CH2OH)4 Dissociation:- Cr2072- + H20 2HCrO42- 2H+ +2CrO42- (Orange) (Yellow)

3)Instrumentatal Deviation:- The law is valid If light used is monochromatic. If not deviation may occur. Deviation may occur if width of slit is not proper which may allow undesired radiation to pass through it. 5

INSTRUMENTATIONS Instrument used in visible region (400 to 800 nm) is called as colorimeter or photometer Instrument used in Ultra violet & visible region (200 to 800 nm) is called as Spectrophotometer. The basic component of the instruments are :- Radiation Source (Tungsten Filament lamp/ hydrogen or deuterium lamp) Wave length selector( Filter/ monochromator) Sample cell Detector

Detectors:- 1)Photovoltic Cell 2) Phototube 3) Photomultiplier tube

1)Photovoltic Cell

FORMULA ABSORBANCE(A)=E x L x C E= A/L X C A= -log10T A= log10 Io/It A= - log10 It/Io %Transmittance= T x 100