An electrochemical flow-cell for permanent modification of graphite tube with palladium for mercury determination by electrothermal atomic absorption spectrometry

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Spectrochimica Acta - Part B Atomic Spectroscopy
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Moreno R.G.M.
De Oliveira E.
Pedrotti J.J.
Oliveira P.V.
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An electrochemical procedure for palladium deposition on the inner surface of pyrolytic graphite-coated tubes for permanent chemical modification and a cold vapor generation system for the pre-concentration and determination of mercury trace levels in rain, potable, and non-potable water and lake sediment by electrothermal atomic absorption spectrometry is proposed. A tubular electrochemical flow-cell was assembled on the original geometry of the graphite tube, which operated as the working electrode. A stainless steel tube, positioned downstream from the working electrode, was used as the auxiliary electrode. The applied potential was measured against a micro Ag/AgCl(sat) reference electrode inserted in the auxiliary electrode. Palladium solution in acetate buffer (100 mmol l-1, pH=4.8), flowing at 0.5 ml min-1 for 60 min was used to perform the electrodeposition. A homemade cold vapor generation system composed of a peristaltic pump, an injector-commutator, a flow meter and a disposable polyethylene gas-liquid separator flask (approx. 4.0 ml volume) were used. Volumes of 1.0 ml of reagent (2.0% w/v NaBH4 in 0.10 mol l-1 of NaOH) and 1.0 ml of reference or sample solution in 0.25 mol l-1 of HNO3 were carried to the gas-liquid separator using the peristaltic pump. The mercury vapor was carried out to the modified graphite tube by argon flow (200 ml min-1), and pre-concentrated for 120 s. The characteristic mass for 1.0 ml of reference solution was 26 pg (R.S.D.=0.12%, n=5). The detection limit obtained was 93 pg (n=20, 3δ). The reliability of the entire procedure was confirmed by addition and recovery tests and cold vapor atomic absorption spectrometry. © 2002 Elsevier Science Ltd. All rights reserved.
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Atomic absorption spectrometry
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