Spectrophotometric determination of dadmium in Chinese herbs and preparations by the solid phase extraction

Objective:Based on synthesis of 2-(2'-quinolinylazo)-4,5-dimethylphenol,the color reaction of 2-(2'-quinolinylazo)-4,5-dimethylphenol with cadmium(Ⅱ)and the solid phase extraction of its colored complex with Waters Porapak Sep-Pak-C18 cartridge,a new method for the determination trace of cadmium(Ⅱ)was studied.Method:The presence of pH=2.5 HCl-potassium hydrogen phthalatebuffer solution.2-(2'-quinolinylazo)-4,5-dimethylphenol can reacts with cadmium(Ⅱ)to form a stable 2∶1 complex.The colored complex can be extracted by C18 cartridge and eluted by ethanol,then can be determined by spectrophotometry.Result:The molar absorptivity of the complex is 4.7×104 L·mol-1·cm-1at 550 nm.Beer's law is obeyed in range of 0-1.5 μg·mL-1.Conclusion:This method can be applied to the determination of cadmium in Chinese herbs.