Dual-wavelength spectrophotometric determination of cadmium with cadion.

Cadmium has been determined by dual-wavelength spectrophotometry with cadion, p-nitrobenzenediazoaminobenzene-p-azobenzene, and a non-ionic surfactant, Triton X-100. Cadion and its cadmium chelate are dissolved in a micellar solution of the surfactant. The absorbance difference at the wavelength of maximum absorption of the cadmium chelate (477 nm) and that of cadion (566 nm) is measured. A combination of triethanolamine, iminodiacetate and citrate is very effective for masking other ions. Cadmium in zinc metal can be determined without prior separation.