AUTOMATED ONLINE PRECONCENTRATION FOR TRACE-METALS DETERMINATION IN WATER SAMPLES BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

A preconcentration flow system using the cationic resin AG50W-X8 for m ultielement determinations of trace constituents in water samples to w ork on-line with ICP-MS is described. The flow network comprises two s mall resin columns inserted in parallel channels of the injector port. Sample loading onto the columns occurs simultaneously and independent ly. Elution takes place intermittently through each column, releasing eluent fractions containing similar concentrations of the analytes, wh ich are merged downstream. The volume of eluent in the alternate aliqu ots sent through the columns was adjusted to attain precise transient signals. Enrichment factors from 10 to 95 for sample! loading times of 0.5 to 5 min were attained. The eluted band produced a transient peak with width at half peak maximum of approximately 20 s, enough to scan several masses for multielement determinations by ICP-MS. The feasibi lity of the proposed system was demonstrated by determination of Cd, P b, Ni, Cu and Zn in the certified reference water sample SLRS-1. Accur ate results were obtained using a preconcentration factor of 30 fold a nd a sample throughput of 20 samples per hour.