Determination of Thallium in River Sediment by Flow Injection On-line Sorption Preconcentration in a Knotted Reactor Coupled With Electrothermal Atomic Absorption Spectrometry

Abstract

A flow injection on-line sorption preconcentration electrothermal atomic absorption spectrometric (ETAAS) method was developed for the determination of thallium. The Tl ³⁺ –tetramethylenedithiocarbamate (pyrrolidinedithiocarbamate) complex formed in strongly acidic medium (0–3 mol l ^{- 1} HNO ₃ , 0–3 mol l ^{- 1} H ₂ SO ₄ , 0–2.5 mol l ^{- 1} HClO ₄ or 0–2 mol l ^{- 1} HCl) is sorbed on the inner walls of a PTFE knotted reactor (100 cm × 0.5 mm id) and quantitatively eluted with 45 µl of ethanol. The ETAAS determination is performed in parallel with the preconcentration of the next sample. Using a preconcentration time of 30 s and a sample loading rate of 4.8 ml min ^-1 , an enhancement factor of 27 is obtained in comparison with direct injection of 45 µl of aqueous solution. The adsorption efficiency is 51%. The detection limit (3s) is 0.015 µg l ^{- 1} and the precision (RSD) is 2.9% for 0.4 µg l ^{- 1} Tl (n = 11). The accuracy of the method is demonstrated by the analysis of a Community Bureau of Reference certified reference material 320 river sediment (indicative value for thallium concentration).