Validation of microwave dissolution of lyophilized vegetal tissue for the subsequent determination of copper, lead, chromium and cadmium by using atomic absorption spectrometry

This paper describes the optimization and validation of a microwave oven dissolution procedure for the analysis of lyophilized vegetal tissue and the subsequent determination of Cu, Pb, Cr and Cd by using atomic absorption spectrometry (AAS). The optimization method was devised on the basis of Plackett-Burman designs. Each design of n experiments can study up to (n - 1) variables, but no attempt was made to identify whether two or more effects were interfering with each main effect. The optimum conditions found for each variable were: 0.2-0.5 g sample weight; 2.5 ml of concentrated nitric acid; 1 ml of concentrated hydrofluoric acid; pre-digestion; 12 digestion vessels; 90% microwave power for a digestion time of 9 min. Results for Cu, Pb, Cr and Cd in lyophilized vegetal tissue were in agreement with the reference values provided by an interlaboratory study.