Improvement approaches for the determination of Cr(VI), Cd(II), Pd(II) and Pt(IV) contained in aqueous samples by conventional XRF instrumentation

This work was aimed to achieve improved instrumental sensitivity and detection limits for the determination of several elements (Cr (VI), Cd, Pd and Pt) in liquid samples by using conventional energy dispersive x-ray fluorescence (EDXRF) and wavelength dispersive x-ray fluorescence (WDXRF) instrumentation. In all cases, the preconcentration of metals from liquid solutions was performed by using membranes activated with the commercial anionic exchanger Aliquat 336 (a quaternary ammonium salt), which also permits the isolation of Cr (VI) species for further x-ray fluorescence analysis. Likewise, for the improvement of the instrumental sensitivity, a special sample holder device was used in the case of Cd determination by EDXRF (tungsten x-ray source) instrumentation. For WDXRF analysis, the spectral evaluation was carried out by the integration of the peak area (using WinQXAS software) instead of the common net peak line intensity traditionally used in conventional WDXRF systems. With the proposed methodologies, a linear response between the metal present in the aqueous solutions and the metal extracted in the membranes was obtained, highlighting the feasibility of using these membranes as standards for x-ray fluorescence spectrometry (XRF) analysis for future determination of these elements when contained in liquid samples. Concerning the calculated detection limits, in all cases, they were in the mu g l(-1) range, indicating the possibilities of the proposed methodology for trace determination content of Cd, Cr(VI), Pd and Pt in liquid solutions using conventional EDXRF and WDXRF instrumentation. Copyright (C) 2008 John Wiley & Sons, Ltd.