1.1 This standard is applicable to determination of surface water and industrial waste water.
1.2 Determination scope
Volume of the test portion is 50mL. Cuvette with 30mm optical path is used, the minimum detectable amount of this method is 0.2μg Chromium (VI), and the minimum detectable concentration is 0.004mg/L; and the detectable upper concentration limit is 1.0mg/L.
1.3 Interference
When the iron content is greater than 1mg/L, it will show yellow. molybdenum (VI) and mercury (Hg) also react with color reagent to generate colored compound, however, under the color rendering acidity of this method, the reaction is insensitive, and the molybdenum and mercury (Hg) with concentration reaching 200mg/L will not interfere determination; while for vanadium, when its content is greater than 4mg/L, the color rendering will be interfered. 10min after reaction between vanadium and the color reagent, the color may fade automatically.
2 Principle
Chromium (VI) will react with 1, 5 diphenylcarbohydrazide to generate aubergine compound in acid solution, and the spectrophotometric determination will be conducted at 540nm wave length.
