Ultra-low (ppb) quantitative analysis using Ultra Carry method for river water standard JAC0032

Water investigation for contaminants that could be harmful to humans and surrounding flora and fauna is not typically done by XRF due to the very low levels of detection required for this analysis. Government regulations are in place to monitor harmful substances in water. Lead (Pb), chromium (Cr), arsenic (As), and selenium (Se) are some of the more important analytes of interest because of the potentially adverse effects these trace metals have on the brain and reproductive systems in human and animal alike, as well as the mutagenic changes they can cause in crop and plant life.

The Ultra Carry preparation method uses a filter paper to concentrate an aqueous liquid sample on a specially designed absorbent pad that is mounted on a Mylar film, which is stretched across a rigid plastic disk. This unusual sample holder (as seen in Figure 1) allows the Rigaku ZSX Primus II WDXRF spectrometer to do a standard water type analysis in only a few minutes and attain values at the PPB level, which rival its competitive ICP analysis method for sensitivity- while offering a drastically reduced preparation set-up time.

Figure 1

The specially designed Ultra Carry method was used in the following analysis of river water standard JAC0032 (River Water standard) for ultra low ppb levels of Pb, Cr, As and Se. Because the standard contains such low concentration levels it was pre-concentrated from 50 mL to 500 μL. Spectral scans of the hazardous analytes of interest can be for Pb, Se, As, and Cr, respectively.

Quantitative calibrations were created using typical AA standard solutions dried on the Ultra Carry. The lower limits of detection for each element are shown in table 1.

Table 1

500 microliters of the pre-concentrated river water sample (1/100 concentration) was then dripped and dried on the Ultra Carry and run under a vacuum atmosphere. The resulting values of the test sample were then recalculated back to an "as received" basis producing the final results shown in table 2.

Table 2