A large number of publications describe the determination of arsenic in “environmental” samples in the broadest sense, a substantial subset of which focus on plant-based foodstuffs. There is a considerable interest in the inorganic arsenic content of food, especially rice, as there is recent evidence that concentrations may be high enough to exceed acceptable risk thresholds. The methodology for the determination of arsenic in rice is critically evaluated and results (a) for a rice flour reference material (National Institute of Standards SRM 1568a, certified only for total arsenic) and (b) a recent proficiency test (run by the European Commission's Joint Research Centre Institute for Reference Materials and Measurement) are examined. Difficulties with this particular analysis may lie in the sample preparation stages, over which there is still disagreement with regard to species stability, though a simple, hot-water extraction may be sufficient. High performance liquid chromatography separations with plasma-source mass spectrometry detection are popular; however, chromatographic separations are often not adequately described, the enhancement effect of carbon-containing species is often overlooked, and the fate of chlorine-containing species, responsible for an isobaric overlap interference, often obscure. Compound-dependent responses, for which there is a plenty of evidence, are almost never acknowledged or discussed. 1. Introduction Writing reviews of some aspect of the measurement of arsenic compounds as described in the burgeoning literature is a popular activity. The field is too large to be encompassed by any one review article, and so the authors of each recent review have defined a subsample of the literature on which to focus; however, there is significant overlap, as several writers have chosen the topic of the measurement of arsenic compounds in environmental samples. In the paper that you are reading right now, the focus will be on an evaluation of the current status of our ability to measure one or more defined arsenic compounds of interest in a variety of materials, but with some emphasis on foodstuffs and a particular emphasis on rice. And to simplify matters even more, particular attention will be given to procedures in which the arsenic compounds are separated by high performance liquid chromatography (HPLC) and detected and quantified by inductively coupled plasma mass spectrometry (ICP-MS). A further restriction of a 5-year time horizon (approximately) has also been imposed. As will be discussed below, there is currently considerable
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