SOP for STANDARD WORKING PROCEDURE FOR ESTIMATION OF IRON

Determination of Iron  content

REAGENTS:

1. Hydrochloric Acid: Concentrated

2. Hydrochloric Acid: (1:1)

3. Nitric Acid: Concentrated

4. Nitric Acid: (1:499)

5. Sulphuric Acid: Concentrated

6. Iron Stock Solution: Merck 1000 mg/L NIST Certified Reference Material or

      Dissolve 1.0 gm of Iron wire in a mixture of 10 ml 1:1 HCl and 3 ml of conc.

      HNO₃ and dilute to 1000 ml with water in volumetric flask. (1ml=1mg of Fe)

PROCEDURE:

Preparation of Standard Solution: Prepare a regent blank and a series of 100 ml

Standards containing 0.5, 1.0, 1.5, 2.0 and 2.5 mg/L of Iron 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 and 0.5 ml H₂SO₄. 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 concentrate in mg/L of Iron directly.

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

REFERENCE: IS 3025 (Part 53): 2003