Use of focused microwaves for expeditive shortening of sample pre-treatment: digestion and reduction procedures prior to selenium speciation as selenium(IV) or selenium(VI)

Abstract

Digestion programmes for different types of samples (milk, sausage and lyophilized pig kidney certified reference material) have been developed using a focused microwave digestor prior to the determination of selenium. The digestion step does not alter the oxidation state of the analyte; thus, the speciation of the target analyte is also achieved with the help of the microwave digestor, which facilitates a subsequent on-line reduction step in a flow injection (FI) manifold before determination by FI cathodic stripping voltammetry. Excellent recoveries for the spiked and certified values were obtained using digestion programmes which varied from 20–45 min. The on-line microwave procedure for the reduction of Se^VI affords good sensitivity and linearity (3–120 µg l^–1, r= 0.994) of the over-all determination method, and dramatically reduces the time necessary for Se^VI reduction.