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 sampl e digestion with ICP-AES detection. In brief, sucrose samples were sub jected to a preliminary digestion and were then analysed with and with out 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 su ggests that additional decomposition was occurring in the aerosol phas e and that the decomposition products (gaseous NO2 and CO2) were remov ed from the aerosol flow stream by the membrane desolvator. For sucros e samples spiked at 100 ng g(-1) with Pb and digested by an open-vesse l procedure, the average recovery (n=5) improved from 25 to 106% when the digests were analysed with the desolvator. The RSD improved from 7 6 to 7.3% by the addition of the desolvator. Improved performance with out the desolvator could only be achieved by the addition and evaporat ion of an excess of oxidizing agents which increases cost, analysis ti me and the chance for environmental contamination. With closed-vessel digestion, sucrose samples spiked with lead at 1.0 mu g g(-1) demonstr ated improvement in the average recovery from 19 to 84% when analysed with the desolvator. Similarly, the RSD decreased from 21 to 4.6% by t he addition of the desolvator. In addition to Pb, similar improvements were demonstrated for As, Cd, Cu and Sn by the closed vessel procedur e.