Abstract: A high throughput analytical method for the direct determination of inorganic arsenic content in rice by hydride generation (HG) inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) was established. Inorganic arsenic was extracted from rice samples with a mixture of nitric acid and hydrogen peroxide. Arsenic (V) was pre-reduced into arsenic (III) by adding 5 mol/L hydrochloric acid, and then 2 g/100 mL sodium borohydride solution was used to reduce inorganic arsenic (III) into volatile arsenic hydride (AsH3) in a multimode sample introduction system (MSIS). Finally, AsH3 was injected into the ICP-MS/MS system and directly detected. In the MS/MS mode, arsenic was transferred to arsenic oxide using oxygen as reaction gas to eliminate the mass spectral interference. The limit of detection (LOD) for arsenic was 0.004 μg/L. The results of the method for inorganic arsenic in standard reference materials of rice flour (GBW(E)100348a, GBW(E)100349a, and NIST SRM1568b) were consistent with the certified values, indicating good accuracy of the method. Inorganic arsenic in rice could be detected using this method without chromatographic separation of different arsenic species. This method was characterized by simple and rapid operation, high sensitivity, good accuracy and high reliability, and applicable for the determination of inorganic arsenic content in rice.

Key words: rice; inorganic arsenic; inductively coupled plasma-tandem mass spectrometry; hydride generation; multimode sample introduction system