SOP for STANDARD WORKING PROCEDURE FOR ESTIMATION OF SELENIUM

PRINCIPLE:

 The method is based on the atomic absorption spectrometric measurement of selenium generated by the thermal decomposition of selenium hydride. Under the Condition of this method only Se (IV) is quantitatively converted to the hydride to avoid by reaction with NaBH₄ in a HCL medium.

Limit of Detection: 0.01 mg/l

REAGENTS:

1. Sodium Borohydride: 3% NaBH₄ in 1% NaOH

2. Sodium Hydroxide

3. Hydrochloric Acid: Concentrated

4. Sulphuric Acid: Concentrated

5. Hydrogen Peroxide: 30%

6. Selenium Stock Solution: Merck 1000 mg/l NIST Certified reference Material or Place 1.4053 gm of selenium Dioxide in a volumetric flask of 1000 ml .Add 2 gm of sodium Hydroxide and dissolved in a small quantity of water( 1ml =1 mg of se)

7. Working Solution: Prepare daily. Prepare series of standard covering the required range (0.005, 0.010, 0.015, 0.020 and 0.025 mg/l). Add 2 ml Hydrochloric Acid per 100 ml to all working standard solution before diluting to volume with water.

PROCEDURE:

Preparation of Blank Solution: Pipette 2 ml of HCL in to 100 ml volumetric flask and dilute to volume with distilled water. Treat the blank in exactly the same way as the sample

Preparation of Sample: Transfer 100 ml sample to 200 ml beaker Add 5 ml of Sulphuric Acid and 5 ml of Hydrogen Peroxide. Boil gently on a preheated  hot plate for about 30 minute or until the final volume reduced to 10 ml .Do not let sample go to dryness. After Manual digestion, dilute to 100 ml with water

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

REFERENCE: IS: 3025(Part-56)-2003