Determination Method for Total Arsenic and Partial-digestion Method with Nitric Acid for Inorganic Arsenic Speciation in Several Varieties of Rice

Abstract

The determination method of total arsenic (As) and the speciation method of inorganic As for non-glutinous rice reported in our preceding paper were applied to several varieties of rice under optimized experimental conditions. In the determination of total As with ICP-MS, acetic acid was added to increase the sensitivity and an internal reference method with germanium was adopted to increase the precision. The extraction temperature in the partial-digestion method with nitric acid to speciate inorganic As was raised to 100°C, because extraction efficiency over 90% was obtained from glutinous rice and colored rice at this temperature. In the investigation of polished and unpolished forms of non-glutinous, glutinous, and colored rice, the amounts of total and inorganic As were 0.04-0.54 mg/kg and 0.02-0.41 mg/kg, respectively. The color of rice was not related to total or inorganic As content. These results indicate that the inorganic As content in commercial rice should be carefully monitored.