On-line preconcentration flow system for multi-elemental analysis by total reflection X-ray fluorescence spectrometry

A scaled-down preconcentration flow system coupled with total reflection X-ray fluorescence spectrometry is proposed for the simultaneous determination of Co, Cu, Mn, Ni, Pb and Zn. The flow system, assembled with an 11-μl column of AG50W-X8 resin and three-way solenoid valves commanded by a computer program, permits the automatic preconcentration, addition of internal standard (Ga) and the deposition of the eluate on the reflector plate. Interferences due to Na and Ca were evaluated. When compared with conventional flow systems, the proposed approach allows a significant reduction in the consumption of eluent (200 μl per determination) and only 1075 μl of sample is required to obtain enrichment factors of approximately 20. Detection limits of Co, Cu, Mn, Ni, Pb and Zn were improved 11, 13, 13, 12, 17 and 14 times, respectively. The proposed system was applied to analyze human saliva and river water samples. Analysis of a Natural Water Standard Reference Material-1640 (Natural Institute of Standard and Technology) showed excellent agreement with certified values. The recoveries for Co, Cu, Mn, Ni, Pb and Zn in a spiked saliva sample were between 64 and 108%.