sured; the AES results were supported by LEED measurements on the Cu (110) surface (12). Therefore, the estimated accuracy is about &lo%. In general, the systematic error for quantification of the surface coverage by the decrease in the matrix signal (5) is higher and depends mainly on the knowledge of the mean escape depth of the Auger electrons, which may be wrong by f30% (1 7).With conventional trace analysis techniques, e.g., acid digestion in combination with microtitrimetric or spectrophotometric determination of sulfur in metals, a detection limit of 0.2 ppm, an accuracy of typical *IO% at 2 ppm and I f l o % precision can be achieved with about 0.5 g of a sample consumed (18). As compared to these figures, the segregation/ sputtering and AES method shows comparable accuracy, better precision, lower detection limit, and negligible sample consumption (

The conditions (e.g. pH, resin, particle size, foreign ions) affecting the uptake of Cd(II), Cr(III), Cu(II) and Pb(II) from aqueous solution by the SM-7 (also called XAD-7) resin, were studied. Based on these studies, a two-column method was developed to overcome the effect of complexation by humic substances. The method was successfully tested with the NBS multielement water standard, SRM 1643a, and was subsequently applied to enrich Cd(II), Cr(III), Cu(II) and Pb(II) in 15 drinking water samples from Hamilton, Ontario. The metals were determined using graphite furnace atomic absorption spectrometry. The results for the drinking water samples showed that leaching of copper and lead occurred from the distribution system.

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