Determination of arsenic(III) and copper(II) by stripping voltammetry in a mixed EDTA-phosphoric acid supporting electrolyte

Abstract

Arsenic is a priority environmental pollutant; therefore, monitoring its concentration in the environment, foodstuffs, and other materials is an important problem. Many authors, in particular Yu.A. Zolotov [1], noted that the development of highly sensitive, selective, reliable, and rapid methods for determining arsenic is a high-priority task. Among different methods used to determine arsenic(III), stripping voltammetry (SVA) plays an important role. The advantages of SVA are the high sensitivity of the simultaneous determination of all ions in the composition of a sample, the rapidity of the method, its high degree of automation, the possibility of performing measurements without removing oxygen from the test solution, etc.Arsenic is one of the elements that can be preconcentrated at the surface of a solid electrode only in the presence of an auxiliary element, for example, copper, mercury, or gold [2]. These elements facilitate the deposition of arsenic on the surface of a solid electrode as intermetallic compounds (IMCs). The auxiliary element can occur both in the solution and at the electrode surface. The discharge-ionization of the arsenic electrochemical concentrate is irreversible [3].The use of graphite, gold, and platinum electrodes and modifying components (Ag, Au, Pd, and Cu) for determining arsenic was considered in [4]. It was found that the total amount of the products of arsenic reduction (As, AsH 3 ) and the hydrogen overvoltage increase in the order Pt > Au > Cu > Ag > graphite.A graphite electrode with an electrolytically applied gold film (gold-graphite electrode) was proposed in [5,6] for determining arsenic. The preconcentration potential of arsenic was less negative at this electrode ( − 0.3 V) than at the gold electrode (-0.6 V). This allowed the effect of copper and other more electronegative elements (Cd, Pb) on anodic arsenic peaks to be reduced.The electrode surface was modified in the arsenic(III)-gold(III) system either by the in situ codeposition of both components on the electrode or by the preliminary deposition of a gold film. As the concentration of gold(III) in the solution was increased at a constant concentration of arsenic(III), anodic peaks of gold(III) and arsenic(III) grew proportionally. The authors of [4] stated that the sensitivity of determining arsenic was higher when deposition was carried out in situ .The electrolytic deposition of arsenic, copper, and gold was studied in [7]. Arsenic (2 × 10 -8 M) was determined (RSD = 20%) at a carbon paste electrode in a 1 M HCl solution containing 5 × 10 -6 M CuCl 2 and 5 × 10 -8 M AuCl 3 . The codeposition of copper and gold on the gold electrode gave Cu 3 As [8]. Postelectrolysis was proposed for obtaining an individual signal from arsenic in the presence of copper [9].Arsenic was determined at a rotating gold electrode after its accumulation at -0.3 V for 4 min [10]. Arsenic(V) was reduced to arsenic(III) with gaseous SO 2 . The electrode was kept at +2.5 V for 1-2 s before each measurement to enhance its reproducibility.A ...

Gold Nanoparticle Modified Screen Printed Electrodes for the Trace Sensing of Arsenic(III) in the Presence of Copper(II)

“…This methodology has been extended [16] but still requires the formation of in-situ formed nanoparticles on solid electrode substrates. Other approaches have explored the addition of complexing agents to the electrolyte [22,23] or via modification of gold macroelectrodes with cysteine allowing the separation of the arsenic(III) and copper(II) stripping peaks [24]. An alternative is to avoid the use of anodic stripping voltammetry and use in-situ formed platinum nanoparticles on solid electrodes based on the direct oxidation of arsenic(III) to arsenic(V) but lacks sensitivity [25].…”