Evaluation of a Nitric Acid-based Partial-digestion Method for Selective Determination of Inorganic Arsenic in Rice

Abstract

Arsenic (As) uptake in human occurs via the food chain mainly. The Joint FAO/WHO Expert Committee on Food Additives has established the provisional tolerable weekly intake level for As as an inorganic As (iAs) value, because iAs in food is much more toxic than organic As. In this study, we studied an acid based partial-digestion method for the complete extraction of arsenicals from rice. HPLC/ICP-MS was used to determine the concentration of iAs selectively. The conditions adopted to extract arsenicals from a 0.5 g of finely ground rice sample were addition of 2 mL of 0.15 mol/L nitric acid and heating at 80ῌ for 2 hr. The LOD and LOQ for iAs were 0.0024 and 0.0079 mg/kg dry weight, respectively. Recovery studies showed good accuracy. When the method was applied to ten short-grain brown rice samples, the iAs concentrations were 0.108ῌ 0.227 mg/kg dry weight and the total As concentrations were 0.118ῌ0.260 mg/kg dry weight. Although dimethylarsinic acid was also detected in most samples, the percentage of iAs content in total As content was 62.2ῌ96.3῍. Thus, iAs was the principal As species in the short-grain brown rice samples tested.

Effects of Water Management on Cadmium and Arsenic Accumulation and Dimethylarsinic Acid Concentrations in Japanese Rice

“…To determine As speciation in rice grain, a powdered sample of ground rice (0.5 g dry weight) was mixed with 2 mL of HNO 3 (0.15 M) in a 10 mL capped high-density polyethylene centrifuge tube, and the mixture was heated on an aluminum heating block at 80 °C for 2 h. The solution obtained was diluted to 10 mL with water and passed through a 0.45 µm filter before analysis (25). For As speciation of rice straw, ears, and stems and leaves, 5 mL of 68% aqueous HNO 3 was added to a ground powder sample (0.5 g dry weight) in a 50 mL Teflon tube, and the mixture was heated at 100 °C for 4 h. The solution obtained was diluted to 50 mL with water and passed through a 0.45 µm filter before analysis (26).…”

“…HPLC/ICP-MS analysis showed that the rice grain samples contained mostly arsenite and DMA, with trace amounts of arsenate. However, because HNO 3 is generally regarded as an oxidative acid (25), the sum of arsenite and arsenate was presented as the total inorganic As. The Student's t-test and the least-significant difference (LSD) test were used to test for statistical significance in differences between treatments.…”

Effects of Arsenic Compound Amendment on Arsenic Speciation in Rice Grain

“…To determine As speciation in rice grain and straw, a powdered sample of ground rice (0.5 g dry weight) was mixed with 2 mL of HNO 3 (0.15 M) in a 10 mL capped high-density polyethylene centrifuge tube, and the mixture was heated on an aluminum heating block at 80 °C for 2 h. The solution obtained was diluted to 10 mL with water and passed through a 0.45 μm filter prior to analysis. 13 As speciation in the grain, straw, soil solution and soil were determined by HPLC/ICP-MS. 14 A SuperIC-Anion column (5 μm, 4.6 mm id Â150 mm) and a guard column (Tosoh, Tokyo, Japan) with an isocratic mobile phase system consisting of 10 mM of ammonium acetate were used. The HPLC system PU 712i (GL Sciences, Tokyo, Japan) was used.…”

“…To determine As speciation in rice grain and straw, a powdered sample of ground rice (0.5 g dry weight) was mixed with 2 mL of HNO 3 (0.15 M) in a 10 mL capped high-density polyethylene centrifuge tube, and the mixture was heated on an aluminum heating block at 80 °C for 2 h. The solution obtained was diluted to 10 mL with water and passed through a 0.45 μm filter prior to analysis …”

Determination of Sixteen Elements and Arsenic Species in Brown, Polished and Milled Rice

“…Arsenic species were extracted from the prepared rice flour samples using a heating-block extraction technique with HNO3 as the solvent. 30,31 A portion of each sample (0.5 g) was placed in a 10-mL glass tube, and 2 mL of 0.15 mol L -1 HNO3 was added. The capped tube was placed in a heating block at 100 C for 2 h. After cooling, a small volume of water was added, and the tube was centrifuged at 3500 rpm for 10 min.…”