Trace elemental analysis of commercial bottled drinking water by a portable total reflection X-ray fluorescence spectrometer.

A portable total reflection X-ray fluorescence spectrometer was applied to commercial bottled drinking water containing 62 ppb (microg/L) V, 7.5 ppm (mg/L) Ca, and 1 ppm K. A dry residue, prepared by repeated pipetting and drying a 20 microL portion of drinking water on a sample holder six times, and another dry residue, prepared by pipetting and drying a 120 microL portion of the drinking water, were measured. The size of the dry residue of the drinking water was reduced by repeating the pipetting and drying. Calcium and potassium were easily detected in these two dry residues. Vanadium was detected in the dry residue prepared by repeated pipetting and drying. Vanadium, calcium, and potassium were quantified by using an internal standard, and the average quantified concentrations of V, Ca, and K were 91 ppb, 8.2 ppm, and 1.5 ppm, respectively. Although these quantified concentrations deviated from the certified concentrations (62 ppb of V, 7.5 ppm of Ca, and 1 ppm of K), it was possible for this portable spectrometer to estimate approximate concentrations.