Analytical Method: Thiocyanate and Cyanide in Wastewater

Reagents

Product No. 103883 Iron nitrate nonahydrate for analysis
Product No. 100456 Nitric acid 65 % for analysis
Product No. 116754 Water for analysis
Membrane filter 0.45 μm pore diameter

Reagent 1

Dissolve 20 g iron nitrate nonahydrate in 24.5 mL of nitric acid 65 % and make up to mark with water for analysis in a 100-mL volumetric flask.

Hints

Thiocyanate causes interference when cyanide is being determined in water and waste water. This is because it reacts as cyanide and its value is included in the total sum determined. This procedure is not disrupted by 100-fold amounts of cyanide based on thiocyanate. Separate determination of cyanide and thiocyanate allows both components to be determined by differential analysis.

Measurement Range

0.05 - 10.00 mg/l SCN at cell length 50 mm and 445/446 nm
0.3 - 50.0 mg/l SCN at cell length 10 mm and 445/446 nm

Sample Preparation

The sample solution must be clear; if not, filter through a folded filter membrane filter with 0.45 μm pore diameter.

Analysis

Mix 5.0 mL of sample solution, 0.30 mL of reagent 1. Allow to stand for 10 minutes and measure at 445 nm (at 446 nm in the photometer SQ 118 against water).

Calculation when measuring the absorbance value using the above NOVA photometers without programming the method in the memory of the instrument:

Calculation when measuring the absorbance value using the photometer SQ118 without programming the method in the memory of the instrument: