1 Definition
Determination of total chrome is to determine the total chrome with 1.5 Diphenylcarbahydrazide spectrophotometric method after trivalent chromium is oxidized into hexavalent chromium. If the chromium content is high (>1mg/L), the ammonium iron sulphate titration may also be adopted.
Method I Potassium Permanganate Oxidization - 1.5 Diphenylcarbahydrazide Spectrophotometric Method
2 Application Scope
2.1 This standard is applicable to the determination of total chromium in surface water and industrial waste water.
2.2 Determination scope
With 50mL of test portion and a cuvette of 30mm optical path, the minimum detectable quantity of chromium is 0.2μg and the minimum detection concentration is 0.004mg/L; if a cuvette of 10mm optical path is used, the upper limit concentration is 1.0mg/L.
2.3 Interference
The iron takes on yellow when the iron content is greater than 1mg/L. Molybdenum (VI) and mercury (Hg) also react with colour reagent to generate colored compounds, however, under the colour rendering acidity of this method, the reaction is insensitive, and the molybdenum and mercury (Hg) with concentration reaching 200mg/L will not interfere determination. The vanadium, when its content is greater than 4mg/L, will interfere the colour rendering. 10min after reaction between vanadium and the colour reagent, the color may fade automatically.
