CALIBRATION OF UV-VISIBLE SPECTROPHOTOMETER

1.0 CONTROL OF ABSORBANCES
PROCEDURE: REPARATION OF POTASSIUM DICROMATE SOLUTION: Dry K2Cr2O7 at 130oC for 2 hours. Weigh accurately about the quantity of sample equal to 60mg into 1000ml volumetric flask. Add 0.005m Sulphuric acid to dissolve and dilute with the same solvent.
Find out the absorbances of (A 1% 1cm) above said solution at wavelengths of a 235nm, 257nm, 313nm and 350nm. Calculate the (1% 1cm) value using the following expression.
Absorbance X 1 X 1000 / Weight of K2Cr2O7 in g X 100
Check the value for each wavelength with the tolerances given four wavelengths.


PREPARATION OF REAGENT:
(i) Dilute 3ml of concentrated sulphuric acid and make up 100ml with distilled water.
(ii) Dilute 20ml to 2000ml with distilled water.
2. LIMIT OF STRAYLIGHT:
The absorbance of a 1.2-% w/v solution of potassium chloride at a path-length of 1cm should be greater than 2.0 at about 200nm when compared with water as reference liquid.
1.2% POTASSIUM CHLORIDE SOLUTION:
Take 1.2 g of Potassium chloride previously dried at 105oC for two hours into the 100ml volumetric flask. Add water to dissolve and make up to volume with water.
3. RESOLUTION POWER:
Record the spectrum of a 0.02% v/v solution of Toluene in Hexane UV. The ratio of the absorbance at the maximum at about 269nm to that at the minimum at about 266nm is not less than 1.5 unless other wise specified in the monograph.
0.02% v/v TOLUENE:
Take 0.02ml of Toluene into the 100ml volumetric flask. Add Hexane to volume.