SOP for STANDARD WORKING PROCEDURE FOR ESTIMATION OF MERCURY

PRINCIPLE:

            The flameless AAS procedure is physical method based of the absorption of radiation at 253.7 nm by Mercury vapor. The mercury is reduce to the elemental state and aerated from solution in a closed system. The mercury cold vapor passes through a cell positioned in the light path of mercury Hollow-Cathode lamp of an AAS.

Limit of Detection: 0.0005 mg/l

REAGENTS:

1. Stanous Chloride: Dissolved 25 gm of stannous chloride in water containing 50 ml conc.HCL and dilute to 250 ml with water

2. Hydrochloride Acid: Concentrate

3. Nitric Acid: Concentrate

4.  Mercury Stock Solution: Merck 1000 mg/l NIST Certified Reference Material or Dissolved 1.354 mg Mercuric Chloride in about 700 ml of distilled water Add 10 ml of conc. Nitric Acid and make to 1000 ml(1ml=1mg of Hg)

5. Working solution: Prepare daily .Prepare series of standard covering the range (0.01,0.02,0.03,0.04 and 0.05mg/l).Add 10 ml Hydrochloric Acid per 1000ml to all working standard solution before dilution.   

PROCEDURE:

Preparation of sample: Transfer 2000 ml sample to evaporate dish. Add 5 ml of Nitric acid .Evaporate gently (Do not boil) on a preheated hot plate until the final volume reduce 20 ml. Do not let sample go to dryness. After manual digestion, dilute 50 ml with water (40 times concentrate the sample)

Analysis: Operate the instrument as per SOP . Aspirate the blank. Then aspirate of standard and then aspirate the sample solution. Read the concentration in µg/l of mercury directly.

(Apply the dilution factor 0.025 because the sample is 40 times concentrate)

REFERENCE :IS: 3025 (PART 48)-1994