Determination of trace cadmium by spectrophotometry with 5-chloro-2-hydroxy- benzenediazoaminoazobenzene

The synthesis of 5-chloro-2-hydroxy-benzenediazoaminoazobenzene (CHDBA) was described. CHDBA as a new chromogenic reagent for the spectr ophotometric determination of cadmium(Ⅱ) was studied. In a borax buffer at pH 10 with the presence of triton 100, cadmium (Ⅱ) reacted with CHDBA to form a stable red complex with molar ratio of 2∶1, giving a maximum absorpt ion at 524 nm with the apparent molar absorptivity of 1.78×10 5 L/mol·cm. Be er′s law was obeyed up to 25 μg of cadmium(Ⅱ) in 25 mL of so lution and the relative standard deviations was less than 3.2%. The method was applied to determine cadmium(Ⅱ)in waste water samples.