Determination of Trace Cadmium (Ⅱ) in Water by Spectrophotometry in Cadmium (Ⅱ)-Potassium Iodide-Malachite Green-Gelatine / 环境与健康杂志

ABSTRACT

Objective To establish a high sensitive spectrophotometry for determination of trace cadmium in the water. Methods A complicated ion-association complex of Cd(Ⅱ)-potassium iodide-malachite green was formed in the phosphate acid, and the addition of gelatine could enhance the sensitivity of the reaction.The maximum absorption of the ion-association complex was at 680 nm,the effect of experimental conditions such as the reagents concentration,the temperature and the influence of foreign matters were considered.Results In the optimum condition(6.0 ml of 40% potassium iodide-aseorbic acid solution,0.5 ml of 5.0 mol/L phosphate acid solution,0.5 ml of 0.5% gelatine solution,1.5 ml of 1.0?10~(-3)mol/L malachite green solution in a 25ml volumetric flask,diluted with water and mixed well and determined immediately),the linear regression equation was △A=0.011+ 0.957 c,r=0.998 5.Beer's law was obeyed in the range of 0.02 ?g/ml to 0.80 ?g/ml for Cd(Ⅱ)and the limit detection was 0.02 ?g/ ml.The composing ratio of the complex was MGCdI=214,and its apparent molar absorptivity coefficient was 1.08?10~5 L/(mol? cm).The recovery rates of Cd(Ⅱ)were 97.0%-101.5%,RSDs were 1.36%-3.58%.Conclusion This method is sensitive,simple, rapid and is applicable to the determination of the trace Cd(Ⅱ)in water.