Aerosol-phase assisted sample digestion for the determination of trace metals in organic samples by plasma atomic emission spectrometry

This report provides evidence of on-line, aerosol-phase assisted sample digestion with ICP-AES detection. In brief, sucrose samples were subjected to a preliminary digestion and were then analysed with and without a membrane separator/desolvator. In the presence of the desolvator, spike recoveries, for various metals including As, Cd, Cu, Pb and Sn, were higher and demonstrated better precision compared with results obtained for digests analysed without the membrane desolvator. This suggests that additional decomposition was occurring in the aerosol phase and that the decomposition products (gaseous NO2 and CO2) were removed from the aerosol flow stream by the membrane desolvator. For sucrose samples spiked at 100 ng g(-1) with Pb and digested by an open-vessel procedure, the average recovery (n=5) improved from 25 to 106% when the digests were analysed with the desolvator. The RSD improved from 76 to 7.3% by the addition of the desolvator. Improved performance without the desolvator could only be achieved by the addition and evaporation of an excess of oxidizing agents which increases cost, analysis time and the chance for environmental contamination. With closed-vessel digestion, sucrose samples spiked with lead at 1.0 mu g g(-1) demonstrated improvement in the average recovery from 19 to 84% when analysed with the desolvator. Similarly, the RSD decreased from 21 to 4.6% by the addition of the desolvator. In addition to Pb, similar improvements were demonstrated for As, Cd, Cu and Sn by the closed vessel procedure.