Determination of trace cadmium in water samples with 4,5-dimethyl-2-thiazolylazodiazoaminoazobenzene by solid phase extraction spectrophotometry

A new method for the determination of trace cadmium in water samples by solid phase extraction spectrophotometry using 4,5-dimethyl-2-thiazolylazodiazoaminoazobenzene(DMTDAA) as chromogenic reagent was studied.In the medium of pH 10.0 buffer solution and in the presence of TritonX-100, DMTDAA can react with cadmium to form a stable 2∶1 complex.The apparent molar absorptivity is 1.76×10~5 L·mol~ -1 ·cm~ -1 at 518 nm.Beer’s law is obeyed in the range of 0-1.0 μg/mL for cadmium. The cadmium in samples can be enriched and extracted using the cartridge of solid phase filled with strong anion exchange resin(30 μm of grain diameter) and Waters SPE equipment,which can separate Cd from interferential ions such as Hg~ 2+ ,Zn~ 2+ ,Co~ 2+ ,Ni~ 2+ ,Cu~ 2+ ,Pb~ 2+ , etc.The method was applied to the determination of cadmium in water samples.The results are consistent with those of AAS method with RSD of 2.5%-3.1%(n=5) and recovery of 97.0%-106.0%.