DETERMINATION OF TRACE-ELEMENTS IN MINERAL-WATER USING TOTAL-REFLECTION X-RAY-FLUORESCENCE SPECTROMETRY AFTER PRECONCENTRATION WITH AMMONIUM PYRROLIDINEDITHIOCARBAMATE

The determination of trace elements ire mineral water by preconcentrat ion with ammonium pyrrolidinedithiocarbamate (APDC) is described, Samp les were spiked with an internal Ga standard and the precipitated dith iocarbamates of trace elements were separated by filtration through a Nuclepore filter, A small amount of the deposit obtained on the filter was transferred to a quartz reflector plate and analyzed by total ref lection x-ray fluorescence (TXRF) spectrometry, The whole procedure wa s calibrated and tested with standard solutions of Fe, Ni, Cu, Zn, and PB in doubly distilled water in the concentration range 10-200 ng ml( -1). The method was applied to the analysis of mineral water, With Pin e described procedure the absolute limits of detection were improved b y about two orders of magnitude compared with the direct analysis of m ineral water, The improvement in detection limits was mainly due to pr econcentration of the abase metals but also partly to the background r eduction in the spectrum because of the removal of alkali and;alkaline earth elements in the preconcentration process. The precision of elem ental determinations on preconcentrated samples also improved relative to direct water analysis owing to the better counting statistics achi eved in a 200 s acquisition of the respective spectra. (C) 1997 by Joh n Wiley & Sons, Ltd.