Determination of inorganic arsenic species by hydride generation atomic absorption spectrophotometry and cathodic stripping voltammetry

Abstract

Flow injection-hydride generation-atomic absorption spectrophotometry (FI-HG-AAS) and square wave cathodic stripping voltammetry (SWCSV) were compared to detect inorganic arsenic species in lemongrass and turmeric. Two species, arsenite (As III ) and arsenate (As V ), were considered as they are known to occur in most terrestrial plants. As III and total water-soluble inorganic arsenic (TAs inorg ) were determined under different conditions.As III was selectively determined by using a soft generation condition, i.e., low HCl concentration, whereas TAs inorg was determined after pre-reduction of As V to As III with a KI/ascorbic acid mixture. The As V content was estimated as the difference between both measurements. Under optimal conditions, the limits of detection (LOD) by FI-HG-AAS were 0.02 and 0.03 µg/l for As III and TAs inorg , respectively. Relative standard deviations (n = 9) of less than 4% were obtained for both inorganic arsenic species. The accuracy was also verified by analysing spiked samples and certified reference material: CTA-VTL-2 (Virginia Tobacco leaves). The recoveries of both species were found to be between 90 and 115%. The determination of inorganic arsenic species by SWCSV in the samples is based on the formation of a copper-arsenic intermetallic compound at the hanging mercury drop electrode (HDME) during the preconcentration step. Only As III was deposited on the Hg electrode when Cu was present in the HCl medium. TAs inorg can be determined by reducing As V to As III with sodium thiosulphate. As V is quantified as the difference. At optimum conditions, the LOD for As III and As V were 0.5 and 0.4 µg/l, respectively. Relative standard deviations (n = 10) of less than 5% were obtained and the method was validated by analysing the spiked samples and certified reference material. FI-HG-AAS showed better LOD than SWCSV for both inorganic arsenic species. There was, however, a strong agreement between TAs values obtained by using FI-HG-AAS and SWCSV technique in lemongrass, turmeric, and the certified reference material (CTA-VTL-2). As V was the main inorganic arsenic species found in lemongrass and turmeric. The results confirm that the As content of both samples do not exceed the food safety limits for Thailand and several countries.

Inorganic Arsenic Determination in Food: A Review of Analytical Proposals and Quality Assessment Over the Last Six Years

“…This review considers types of electrode systems, including electrodes based on nanomaterials, and highlights the increased demand by researchers for sensors to measure in situ. The vast majority of applications of such systems have been applied to the analysis of iAs in water and waste water, or in some plant samples, 222 and no applications to the measurement of iAs in food samples have been found. A new arsenate-selective electrode have been recently developed by Somer et al., 223 prepared from solid salts: Ag 3 AsO 4 , Ag 2 S, Cu 2 S. The responses of some interfering anions are studied, and it is applied to the determination of arsenate in beer.…”

A Versatilidade Do Eletrodo De Gota Pendente De Mercúrio Em Química Analítica – Uma Revisão Sobre Recentes Aplicações

“…32 Estudos com As, Cu, Pb, Cd e Zn foram realizados na tentativa de determinar a concentração destes elementos em plantas possivelmente contaminadas. 35,36 Locatelli e Melucci desenvolveram um método sequencial de duas etapas para a determinação de Hg, Cu, Pb, Cd e Zn em amostras de vegetais como espinafre, alface e tomate empregando um eletrodo de ouro e o HMDE. O HMDE foi utilizado na determinação do Cu, Pb, Cd e Zn e o eletrodo de ouro empregado na determinação de Hg e Cu.…”

Determination of inorganic arsenic species by hydride generation–inductively coupled plasma optical emission spectrometry

“…In the environment, arsenic is found to combine with other elements such as carbon and hydrogen which is referred to as organic arsenic whereas that with oxygen, chlorine, and sulphur is called inorganic arsenic 4 . Inorganic arsenic is considered to be the most toxic form found in groundwater, surface water, and food 2,5 . Its toxicity 6 and mobility depend on the existing chemical forms; the most toxic species are arsenite As(III) and arsenate As(V) which are main forms in the environment 4 .…”