Determination of Trace Amounts of Cadmium with p-Acetyl-Benzenediazoaminoazobenzene by Primary–Secondary Wavelength Spectrophotometry

The reaction between Cd²⁺and a chromogenic agent, p-acetylbenzenediazoaminoazobenzene (p-ABAA) at pH 12.5 is sensitive and selective in the presence of triethanolamine and citrate. The solubilization and sensitization of the OP emulsifier (nonionic surfactant) was observed in the above reaction. Because the absorption of excess p-ABAA interferes with the absorption of the complex, primary–secondary wavelength spectrophotometry (PSWS) was used instead of the single-wavelength method in the determination of trace amounts of cadmium. Results showed that this method gave out a higher precision and better accuracy than the single-wavelength method, because two wavelengths that are located at the peak absorption and the valley absorption of the reaction solution were used simultaneously. By analyzing samples, the relative standard deviations were less than 8% and the recovery between 96.5 and 111%.