Direct determination of dissolved and total thallium in lake waters by laser-excited atomic fluorescence spectrometry

Thallium is a highly toxic, under-studied priority element. However, it has recently created much interest due to afresh and rapid improvements in detection limit. It appears that there are no published Tl data for Great Lakes waters, likely due to the poor sensitivity of classical methods. An electrothermal Laser-Excited Atomic Fluorescence Spectrometer has been optimized to detect sub-femtogram of thallium and used to develop a method for direct determination of dissolved and total thallium in lake waters. The method voids the labor-intensive, contamination-prone tasks of filtration, centrifugation and acid digestion of collected particulates. Adequate precision and recoveries were achieved using several lake waters (undigested and digested) and a certified reference material. The concentration of thallium in the acidified (0.2% HNO3) Milli-Q-Water was monitored over a period of four months and averaged 0.02 +/- 0.01 ng/l. The concentration in Hamilton Harbor ranged from 3 to 48 ng/l. The mean of dissolved/total fraction of Tl in the Harbor water was 80%.