PPB ANALYSIS OF RIVER WATER BY XRF

X-ray fluorescence spectrometry is used for environmental analysis because of its non-destructive, rapid, simple, and highly reproducible feature. It is possible to analyze not only solid but liquid samples such as sewage, waste water, industrial discharge, and river and sea water with XRF spectrometers. Liquid cells or a micro-droplet filter paper are used in XRF analysis for liquid. With micro-droplet filters, a small amount of liquid is dropped on a filter paper and the dried paper containing the non-volatile elements is measured. While liquid cells must be placed in He or other gaseous mediums with standard atmospheric pressure, the dried paper of the micro-droplet method can be measured in a vacuum. However, since the filter paper is now the matrix of the specimens to be measured, background scattering is increased causing the lower limit of detection (LLD) to deteriorate.

In this study of river water, a newly developed micro-droplet method using "Ultra Carry" is presented. This method implements a new absorbent substance instead of the older paper type filters. The method shows reduced background scattering and improved LLDs.

Calibration lines for Pb, As, Cr, Se, and Cd were generated with standard solutions of river water. In this study, 50mL sample was concentrated to about 1mL with a rotary evaporator, and the concentrated sample was dropped twice at 250uL on the Ultra Carry. The reproducibility tests (n=5) were performed, and standard deviation of a few dozen ppb was obtained for each element (Cr 17ppb, As 14ppb, Se 27ppb, Cd 29ppb, Pb 24ppb).

The newly-developed micro-droplet method, which is easy, simple, and highly reproducible, allows analysis at ppb levels for trace elements in water with a standard XRF spectrometer.