This method for measuring selenium in water uses the Spectroquant® Photometer and a clear, filtered sample to evaluate the results at 445 nm.
Spectroquant® Photometer NOVA 30 (Product No. 109748) or
Spectroquant® Photometer NOVA 60 (Product No. 109751)
Rectangular cells 50 mm (Product No. 114944)
Formic acid 98-100% for analysis (Product No. 100264 )
3,3‘-Diaminobenzidine tetrahydrochloride (CAS 868272-85-9) (Product No. 32750)
TitriplexIII® solution 0.1 mol/l (Product No. 109992)
Ammonia solution 25% for analysis (Product No. 105432)
Toluene for gas chromatography (Product No. 108389)
pH-indicator strips, pH 2.0 - 9.0 (Product No. 1.09584)
Sodium sulfate anhydrous for analysis (Product No. 106649)
Water for analysis (Product No. 116754)
Membrane filter with 0.45 μm pore diameter
0.05 – 2.00 mg/L
Fill 9.4 mL formic acid 100% in a calibrated or conformity-checked 100-mL volumetric flask. Make up to volume with water for analysis and mix.
Dissolve 0.5 g 3,3’-diaminobenzidine tetrahydrochloride in 100 mL chilled water for analysis. Prepare freshly each day and store in an amber glass bottle.
Fill 48 mL ammonia solution 25% for analysis in a calibrated or conformity-checked 100-mL volumetric flask. Make up to volume with water for analysis and mix.
The sample must be clear; if not, filter through a membrane filter with 0.45 μm pore diameter.
Calculation when measuring the absorbance value using NOVA photometers without programming the method in the memory of the instrument:
Concentration [mg/l] = Absorbance x 0.654 – 0.037
Result = measured value in mg/l Se4+
Standard deviation: 0.019 mg/l
Coefficient of variation: 2.9 %
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