Determination of cadmium in water by spectrophotometry

A new sensitive colour reaction of cadmium (Ⅱ) is described, in which cadmium formed an ion-association complex with rhodamine B and iodide, in the presence of polyvinyl alcohol and gum arabic. The ion-association complex shows a maximum absorption at 598 nm and an apparent molar absorptivity of 6.44×105 L·mol-1·cm-1,Beer’s law is obeyed for cadmium in the concentration of 0～0.092 μg/mL cadmium. Combining with sulfhydry cotton enrichment, the method has been successfully applied to the determination of cadmium in the river water, The recovery rate is 94.8﹪ to 101.9﹪.