We have been using Quantofix Iron indicator papers Ref MN/913.02. By running spiked samples the results have been lower than expected due to discolouration of the indicatior sticks probably caused by the prssence of heavy metals. The instructions state that this can be eliminated by the addition of cadmium powder. Please could you advice on what source of cadmium powder is required as the instruction does not detail specifics i.e grade and quality.
Any laboratory grade cadmium powder will work for this interference