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CHALLENGES OF FLUORIDE ANALYSES OF ENVIRONMENTAL SAMPLES USING ION CHROMATOGRAPHY

Leong, T.

Fluoride is measured in QAL’s environmental discharges to monitor water quality as part of QAL’s Environmental Authority. QAL is a NATA accredited laboratory and accurate fluoride analysis is required for reporting concentrations in discharges to local aquatic environments.

At QAL, the analysis of fluoride for environmental samples has progressed from the time consuming Ion-Selective electrode method to a fully automated Ion Chromatography system. Ion chromatography was met with the issues of high salinity and low fluoride content limiting the level of dilution available, meaning samples had to be run with high chloride concentrations.

Progression from the initial Dionex DX500 system to the current DX2000/2001 systems has seen changes in columns used, eluent concentrations, current settings, retention times and improvements in suppressor technology. These systems produced acceptable repeatable results with good spike recoveries, reduced man-hours and were not dependent on the skills and expertise of analysts to produce results. Improvements in suppressor technology (and size) increased peak resolution and revealed a previous single peak showing as twin peaks.

This paper describes the challenges in resolving and separating the twin peaks to enable continued accurate analysis.