Abstract
A novel time-based flow-injection–solid-phase extraction system (FI–SPE) coupled with flame atomic absorption spectrometry (FAAS) for automatic on-line preconcentration and determination of thallium was developed. The efficiency of poly-tetrafluoroethylene (PTFE) turnings packed into a column as sorbent material was investigated for thallium extraction. Total thallium was determined by oxidizing thallium(I) to thallium(III), adding bromine in acidic solution. The formed [TlBr4]− anionic bromo complex was retained onto the PTFE turnings by on-line mixing with sodium diethyl dithiocarbamate (DDTC). The preconcentrated Tl(III)-DDTC complex was then effectively eluted with methyl isobutyl ketone (MIBK) and introduced into the flame atomizer for measurement and quantification. The column proved to be effective, stable, and reproducible, with a long lifetime. The enrichment factor was 105 for 60 s preconcentration time, and the sampling frequency 40 h−1. The detection limit was 1.93 μg L−1, and the relative standard deviation (RSD) was 3.2% at 50.0 μg L−1 concentration. The accuracy of the proposed method was estimated by analyzing certified reference materials and environmental and biological samples.
Highlights
Thallium can be found as thallium(I) and thallium(III) inorganic species, and the latter is considered thousand times more toxic [1]
Flame atomic absorption spectrometry is widely used for routine analysis, presenting inherent advantages and desirable characteristics
A Perkin-Elmer Model 5100 PC flame atomic absorption spectrometer (Perkin-Elmer, Norwalk, CT, USA) with deuterium background corrector was furnished with a thallium electrodeless discharge lamp (EDL) operated at 7 W
Summary
Thallium can be found as thallium(I) and thallium(III) inorganic species, and the latter is considered thousand times more toxic [1]. As thallium is toxic even at very low concentrations in environmental and biological systems, analytical techniques presenting high sensitivity and desirable selectivity are required. The actual tendency in trace metal determination involves atomic spectrometry (AS) techniques, such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), hydride generation atomic absorption spectrometry (HG-AAS), as well as inductively coupled plasma atomic emission spectrometry (ICP–AES). Direct determinations are limited by lack of sensitivity in case of metal quantification, as metals are present in various matrices at very low concentrations. This limitation can be overcome by using preconcentration/separation techniques
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