SOP for STANDARD WORKING PROCEDURE FOR ESTIMATION OF CADMIUM

PRINCIPLE:

 The Cadmium content of the sample is determined by Pre-Concentrate aspirating the sample into the flame of an Atomic Absorption Spectrophotometer. The Absorbance is measured at 228.8 nm using a Cadmium Hollow Cathode Lamp.

Limit of Detection: 0.01 mg/L

REAGENTS

1. Hydrochloric acid – Concentrated

2. Nitric acid : Concentrated

3. Nitric acid : (1:499) 

4. Cadmium stock Solution : Merck 1000 mg/L NIST Certified Reference Material or Dissolve 1 g of pure cadmium metal in minimum quantity of concentrated nitric acid and dilute to 1 liter with distilled water (1 ml = 1 mg of Cd)

PROCEDURE

Preparation of standard solution: Prepare a reagent blank and a series of 100 ml standards containing 0.1, 0.2, 0.3, 0.4 and 0.5 mg/L of cadmium by diluting a suitable volume of the standard solution with dilute nitric acid.

Sample preparation: Transfer 1000 ml well-mixed sample to the evaporation dish and add 3 ml nitric acid. Heat and evaporate to 20 ml (do not boil). Cool and add 3 ml nitric acid and heat until digestion is complete. Add 2 ml HCl (1:1 v/v) and heat gently to dissolve the residue. Wash the evaporation dish for 3 to 4 times with water and filter. Wash the filter and discard. Dilute the filtrate & make up 100 ml volume with water. (10 times concentrate the sample)

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.

(Apply the dilution factor 0.1 because the sample is concentrate 10 times)

REFERENCE: IS 3025 (Part 41) : 1994