Volume  Number

previous article

next article

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

Pipat Chooto^a,*, Puchong Wararattananurak^a, Tawatchai Kangkamano^a, Chalermpol Innuphat^a, Waraporn Sirinawin^b

 
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.

Download PDF

28 Downloads 1750 Views

* Corresponding author, E-mail: pipat.c@psu.ac.th

Received 4 Aug 2014, Accepted 7 Jul 2015