SOP for the determination of Sulphate
Scope
This SOP is applicable for the determination of sulphate in all type of water and waste water.
Principle
Sulphate ion is precipitated in hydrochloric acid medium with barium chloride in such a manner as to form barium Sulphate crystals of uniform size. The absorbance of barium Sulphate suspension is measured by a nephlometer or transmission photometer (turbidity meter) and the sulphate ion concentration is determined by comparison of the reading with a standard curve.
Interference
Colour or suspended matter in large amounts will interfere.
Reagents
- Conditioning Reagent
Mix 50 ml glycerol with a solution containing 30 ml concentrated hydrochloric acid, 300 ml distilled water, 100 ml 95 percent ethyl or isopropyl alcohol and 75 g sodium chloride.
- Stock Sulphate solution (100 mg/l)
Dissolve 0.1479 g of anhydrous sodium Sulphate in distilled water and dilute to one litre. (1 ml = 1 mg SO42- )
- Standard Sulphate solution
A series of standard Sulphate solution (1 to 50 ppm) was prepared by diluting 1 ml, 5ml, 10 ml, 15 ml, 20 ml, 25ml, 30 ml, 35ml, 40 ml, 45ml and 50ml of the stock Sulphate solution in separate 100 ml standard volumetric flask by using DM water.
- Barium Chloride
- Conditioning Reagent (Gelatin)
Add 0.3 g gelatin in 100 ml distilled water and warm it on hot plate till it is dissolved. The gelatin solution is kept for about 12 hours, or overnight preferably, at 4°C. After bringing the solution to room temperature, 3.0 g of barium chloride is added to gelatin solution and dissolved by mixing. The turbid solution is kept standing for 2 hours and mixed before use.
Procedure (By Spectrophotometer Method)
Calibration Curve
- The calibration curve was prepared by using standard Sulphate solution (1 to 50 ppm) was prepared by diluting 0 ml as Blank, 1 ml, 5ml, 10 ml, 15 ml, 20 ml, 25ml, 30 ml, 35ml, 40 ml, 45ml and 50ml of the stock Sulphate solution in separate 100 ml standard volumetric flask, add 1 ml conditioning Reagent (Gelatin) and shake well and make up to 100 ml by using DM water.
- Take 10 ml of clear aliquot of the water sample.
- Add 1 ml of conditioning Reagent (Gelatin) and mix well and make up volume to 100ml and wait for 10 min.
- The analysis was done at the wavelength of 420 nm by using spectrophotometer.
Calculation
Read the Sulphate concentration of sample directly from the calibration curve.
Safety guidelines
Proper safety & health precaution are taken while doing the analysis by using safety goggles, apron, safety shoes & using fume chamber for fume generating chemicals.
Reference
IS: 3025 (P-24) 1986 RA 2019