How to determine Cadmium Reduction

Cadmium Reduction Method Theory of Test

Nitrate is reduced to nitrate by copper coated cadmium granules. The nitrate is then measured by reaction with sulfanilamide and N-(1-napthyl) ethylenediamine. The deep pink color generated by this reaction is proportional to the sum of the nitrate and nitrite concentrations, but nitrate may be measured directly by this method in the absence of nitrite. When nitrite is present the sample must be analyzed with and without cadmium treatment. Nitrate is determined as the difference between the two results. The dynamic range of this method is 0.01 to 2-ppm nitrate as NO3.

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This procedure is best performed by a fully equipped laboratory. Alternatively, commercial testing kits using this method are also available.

Limitations of Test

Oxidizing and reducing agents are strong interferences. They adversely affect the cadmium reducing agent and also the nitrate nitrite balance. Cadmium reduction must be carried out at neutral pH so samples may require pH buffering. High concentrations of nitrite may reduce the accuracy of nitrate determinations. CAUTION: solutions and waste from this method contain appreciable amounts of cadmium. Cadmium should not be introduced into public water systems or ground waters.

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