Laser-induced fluorescence determination of thallium in sediments

A simple dissolution procedure is decribed for sediments to be analyzed for thallium by Laser-Excited Atomic Fluorescence Spectrometry (LEAFS). It simply uses a nitric – hydrofluoric acid mixture at room temperature (a “cold dissolution” procedure as opposed to the hot acid digestion) followed by a dilution with water (as opposed to the tedious steps of separation and preconcentration). Excellent accuracy (91–106% recoveries) and precision (4–10% relative standard deviation) were demonstrated by the use of five sediment reference materials of diverse origins. The detection limit was estimated to be 0.5 ng/g of thallium. Additionally, a hot plate digestion procedure, using an in-house designed semi-enclosed Teflon beaker, was also investigated; its analytical results agreed with certified values and confirmed the adequacy of the cold dissolution technique. The method is being applied to study the sediment – water interactions in lake environments. Received: 30 December 1996 / Revised: 20 March 1997 / Accepted: 30 March 1997