SOP for STANDARD WORKING PROCEDURE FOR ESTIMATION OF ZINC

PRINCIPLE:

            The Zinc content of the sample is determined by AAS. For dissolved zinc. The filtrated sample is directly aspirated to the atomizer. For total recoverable zinc an acid digestion procedure is done prior to aspiration of the sample.

Limit of Detection: 0.01 mg/L

REAGENTS

1. Hydrochloric Acid – Concentrated

2. Nitric Acid : Concentrated

3. Nitric Acid : (1:499)

4. Zinc Stock Solution: Dissolve 1 g of acid washed and rinsed zinc granules or 1.245 g of zinc oxide (ZnO) in 20 ml of (1:1) nitric acid. Dilute to 1:1 with distilled water (1 ml = 1 mg of Zn) or Dissolve 1.0 gm of Zinc metal in minimum volume of (1+1) HCl and dilute to 1 liter 1% (v/v) HCl. 

PROCEDURE

Preparation of Standard Solution: Prepare a reagent blank and a series of 100 ml standards containing 0.05, 0.10, 0.15, 0.20 and 0.25 mg/L of Zinc by diluting a suitable volume of the standard solution with dilute nitric acid.

Sample Preparation: To 100 ml portion of the acidified sample add 0.5 ml of nitric acid. If total recoverable zinc is to be determined, add 5 ml of concentrated HCl and filter the sample through acid washed filter paper. Make up to 100 ml in a volumetric flask.

Analysis: Operate the instrument as per SOP. Aspirate nitric acid (1:499) as blank. Then aspirate series of standards and then aspirate the sample solution. Read the concentration in mg/L of zinc directly.

REFERENCE: IS 3025 (Part 49): 1994