Atomic absorption spectrophotometry of cadmium and copper by using solvent extraction with potassium ethylxanthate-methylisobutylketone

Potassium ethylxanthate (KEtX) reacts with many metal ions to form chelate compounds which are easily extracted with various kinds of organic solvents. The present paper is concerned with the study of the optimum conditions and the development of sensitive method for the determination of cadmium and copper with atomic absorption spectrophotometry by using solvent extraction in which KEtX is used as a chelating agent. Methylisobutylketone (MIBK) was the best solvent for the extraction of Cd-EtX and Cu-EtX complexes. The general procedure is as follows: into a 50 ml separatory funnel is taken an aliquot of sample solution containing less than 5.0 μg of cadmium or less than 40.0 μg of copper, then 5.0 ml of 10% ammonium acetate solution is added as buffer solution. If necessary, the pH of the solution is adjusted to 8.5 with (1+2) aqueous ammonia or diluted acetic acid. After the addition of 5.0 ml of 5% KEtX solution, the Cd-EtX or Cu-EtX complex is extracted with 10.0 ml of MIBK by shaking for 3 minutes. The MIBK phase is aspirated after the separation from the aqueous phase directly into the flame. With regard to the interference of diverse ions on the solvent extraction, the presence of Co(II), Ni(II), Fe(III), Cr(III) and Al(III) in large excess amounts (above two hundred times as much as cadmium or fifty times as much as copper) affected. By this method, the determination of cadmium and copper in human tissues was performed successfully. Moreover, because the sensitivity and accuracy of the present method were similar to those the method using sodium diethyldithiocarbamate or ammonium pyrollidine dithiocarbamate as a chelating agent, this method may be used satisfactorily for other practical analysis. (auth.)