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Optimisation of analytical parameters in inorganic arsenic (III and V) speciation by hydride generation using L-cysteine as prereducing agent in diluted HCl medium

Domenii publicaţii > Chimie + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Emil A. Cordos, Tiberiu Frentiu, Michaela Ponta, Bela Abraham, Ioan Marginean

Editorial: Chemical Speciation and Bioavailability, 18 (1), p.1-9, 2006.


The effects on the arsenic spectrophotometric absorption signal and hydride generation of the reaction medium (HCl: 0–0.05M), reducing agent (NaBH4: 0.2 –1% stabilised in NaOH: 0.2 –1%), prereducing agent (L-cysteine: 0–2%) and contact time between L-cysteine and arsenic (III) and arsenic (V) solutions were investigated using FIA–HG–QFAAS. The speciation procedure involved three steps: (i) arsenic (III) determination immediately after the sample was mixed with L-cysteine; (ii) total arsenic determination after a 10 min-contact time between sample and L-cysteine by boiling in water bath at 90+-5 C degrees and (iii) arsenic (V) determination as difference between total arsenic and arsenic (III). Under optimized conditions to generate arsine from arsenic (III) (0.01M HCl, 0.2% L-cysteine, 0.6% NaBH4 in 0.5% NaOH), the arsenic speciation was possible with good recovery (98 –105%) for arsenic (III), arsenic (V) and total arsenic. A rigorous pH control at 2.00+-0.01 prior to arsine generation was necessary. The detection limit based on 3s criteria and parameters of calibration curve was 0.1 ng/mL arsenic. The simple and inexpensive optimised method is used for the determination of leachable inorganic arsenic species within a distribution study of arsenic in the Baia-Mare area, Romania, which is the subject of another paper.

Cuvinte cheie: inorganic arsenic speciation; hydride generation; quartz furnace atomic absorption spectrometry; L-cysteine reducing agent