Electrochemical methods for the determination of total arsenic and arsenic compounds

Abstract

The determination of total arsenic and of arsenic compounds in biological and inorganic samples is a task frequently encountered by analysts. Several electrochemical methods have been developed for the determination of total arsenic (generally after mineralization of the sample), arsenite, arsenate, methylarsonic acid and dimethylarsinic acid. The electrochemical behavior of several other organic arsenic compounds was also studied. This paper reviews these electrochemical methods, their application to environmental samples, and the problems encountered in the electrochemical determination of arsenic and arsenic compounds.

Analysis and Speciation of Traces of Arsenic in Environmental, Food and Industrial Samples by Voltammetry: a Review

“…In particular and as far as arsenic is concerned, there are the two additional closely related aspects that must be taken into account when planning the pretreatment: first, the speciation of arsenic [9,139,140] and, secondly, the different electrochemical behavior of its two oxidation states. The analytical procedures proposed in literature can be separated into those that aim just at As(III) (or, rarely, only As(V)) or total inorganic As(III V) determination, and others in which a separate quantification of each species is pursued (organic compounds of arsenic are only very seldom discriminated by voltammetric techniques [57,141,142]). When speciation is pursued, normally the determination of inorganic arsenic is carried out in two stages, that is, before and after the interconversion between As(III) and As(V).…”

Especiação analítica de compostos de arsênio empregando métodos voltamétricos e polarográficos: uma revisão comparativa de suas principais vantagens e aplicações

“…Essas técnicas são conhecidas como voltametria de redissolução (catódica ou anódica) ou, ainda, como voltametria inversa. Na determinação de compostos de arsênio por voltametria, as técnicas mais empregadas são a voltametria de redissolução anódica (ASV) e a voltametria de redissolução catódica (CSV) empregando, respectivamente, o eletrodo de ouro e o de mercúrio como eletrodos de trabalho 31 . O princípio da determinação de arsênio por voltametria de redissolução pode ser descrito esquematicamente pelos seguintes mecanismos: De acordo com o esquema apresentado, a espécie As(III) (na forma do íon arsenito) é reduzida para arsênio elementar (As 0 ) no eletrodo de trabalho, que pode ser então redissolvido catodicamente pela redução a As 3-, ou anodicamente pela oxidação a AsO 3 3-, durante a varredura do potencial.…”

“…De acordo com a literatura, na ASV para arsênio empregando carbono vítreo como eletrodo de trabalho o As(III) é incompletamente reduzido. Entretanto, a redução de As(III) neste eletrodo é completa quando realizada na presença de Cu(II) ou Hg(II) 31 . Nestas condições, o As(III) é reduzido e reage subseqüentemente com Cu(II) ou Hg(II) formando arsenetos 78,79 .…”

As(III) Determination in the Presence of Pb(II) by Differential Alternative Pulses Voltammetry

“…The lowest LOD achieved by DPP in 1 M HCl was 0.3 ppb As(III) [25]. However, differential pulse anodic stripping voltammetry (DPASV) application allows attaining a LOD as low as 0.02 ppb, as reported by Forsberg et al [45].Species as Pb(II), Sn(II), Tl(I), Bi(III), Sb(III), and selenite having E 1/2 close to that of As(III) interfere the As(III) determination causing overlapping of its peak [46]. In 1 M HCl, the most commonly applied supporting electrolyte, the presence of Pb(II) causes complete overlapping of the As(III) peak as shown bellow, thus requiring the application of complicated laboratory sample pretreatment procedures for analyte separation [8, 19, 41, 42 47, 48] …”

“…In 1 M HCl, the most commonly applied supporting electrolyte, the presence of Pb(II) causes complete overlapping of the As(III) peak as shown bellow, thus requiring the application of complicated laboratory sample pretreatment procedures for analyte separation [8, 19, 41, 42 47, 48]. Various procedures were developed for this purpose: extraction into toluene [46], retaining the interfering cations by cation exchanges resins while the arsenite anion (AsO 3À 3 Þ remains in the solution [35,49], etc. Unfortunately none of them can be applied in-situ.…”