A new strategy for the modification of a carbon paste electrode with carrageenan hydrogel for a sensitive and selective determination of arsenic in natural waters

• Published in: Talanta (Oxford) Vol. 187; pp. 259 - 264
• Main Authors: Núñez, Claudia, Arancibia, Verónica, Triviño, Juan José
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-09-2018
• Subjects: Adsorptive stripping voltammetry; Carrageenan modified carbon paste electrode; Determination of arsenic; Determination of arsenic; Carrageenan modified carbon paste electrode; Adsorptive stripping voltammetry
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2018.05.028

An adsorptive stripping voltammetric method for the determination of As(III) and Astotal in water samples using a carrageenan modified carbon paste electrode is presented for the first time (CAR−CPE). The modified electrode was prepared in different ways: by adding CAR in solid form or as a hydrogel together with graphite and paraffin, as well as adsorbing CAR by applying a potential on an unmodified carbon paste electrode. The best results were obtained when CAR was incorporated as hydrogel (HCAR−CPE). The selection of the ratio amounts for electrode preparation was carried out applying a multivariate experimental design. Variables like amount of graphite (U1), HCAR (U2) and paraffin (U3) were optimized using a (2K+2K+C) model. The results showed that the amount of HCAR was the most significant factor, and the adequate U1:U2:U3 ratio to prepare the electrode was: 493 mg of graphite, 214 μL of paraffin and 134 μL of carrageenan as gel. The optimum parameters for the determination of As(III) were pH = 3.25 (0.01 mol L−1 H3PO4/H2PO4− solution); Eacc = −0.50 V and tacc = 30 s. The electrode presents good linear behavior concentration range from 0.50 to 6.70 μg L−1, with a limit of detection of 0.22 μg L−1. The relative standard deviation was 5.0% at the 1.5 μg L−1 As(III) level (n = 16). The method was validated by quantifying As(III) in spiked tap water from laboratory (RE: 3.0%), and it was applied for the determination of Astotal in water samples from the Loa River (North of Chile) prior reduction of As(V) with Na2S2O3 solution, obtaining 814.00 ± 0.03 μg L−1. The results of the proposed method were compared with those obtained by adsorptive stripping voltammetry with HMDE and by Inductively Coupled Plasma Mass Spectrometry (ICP−MS) techniques.
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•A sensitive and selective method for the determination of As(III) and Astotal is presented.•The carbon paste electrode was modified with carrageenan as hydrogel incorporated in the paste.•The method is based on the formation of arsenic complex with carrageenan.•The adsorbed complex produces a strong peak at − 1.20 V whereas free carrageenan is reduced to − 0.20 V.