VPE 511: Environment and Environmental Hygiene (2+1)

Chemical Impurity

CHEMICAL IMPURITIES

Chemical Impurity to be analysed	Procedure for analysis	Reaction expected	MPL	Inference
1. Ammonia	10 ml of sample in a test tube, add few drops of Nessler’s reagent	Deep yellow or brown or black precipitate	0.06 ppm
2. Chloride	10ml of sample in a test tube, add a few drops of silver nitrate	White precipitate	250 ppm
3. Sulphate	10 ml of sample add a few drops of HCl and a few drops of Barium Chloride	White precipitate formation hastened by heat	250 ppm
4. Nitrites	10 ml of sample, add a few drops of sulphanilic acid and add few drops of a -naphthalamine. Shake well.	Formation of pink colour	Not even
5.Nitrates                     (If nitrites are     absent)	10 ml of sample , add a few drops of sulphanilic acid, add few drops of a -naphthalamine and pinch of Zinc dust	After 3 minutes a pink colour is noticed	1.5 ppm
6. Nitrates                       (If nitrites are      present)	5ml of sample add equal quantity of brucine solution. Effervescence settles down run con. H 2 SO 4 along the sides agitate gently.	Formation of pink colour	1.5 ppm
7. Phosphate	10 ml of sample, add a few drops of  ammonium molybdate solution.  Warm and agitate gently	Yellow precipitate soluble in ammonia solution and reappears	Not even in traces
8. Fluoride	10 ml of sample add a few drops of Ferric chloride	formation of White crystalline precipitate	1 ppm
9. Cyanide	10 ml of sample add a few drops of ferrous sulphate, boil add HCl to obtain clear solution, add few drops of FeCl 2	A greenish to blue colour  is developed	Not even in traces