This kind of information is also vital to many manufacturing industries, as the chemical composition of raw materials, intermediates, final products, and wastes almost certainly impacts decisions about the various manufacturing processes that affect the financial “bottom line.” While the general public may not have ever had any formal education in the role that chemical measurements play in ensuring the quality of their lives, many citizens of western countries assume that information about the chemical composition of their blood can be reliably determined and transmitted to their doctor they also assume that it is safe to eat the food they buy and a high proportion of them will also assume that it is safe to drink the water that comes out of the tap in their homes.
Many areas of scientific study, research, and practice depend on the availability of information about the chemical composition of relevant materials. As will be discussed below, there is currently considerable interest in the arsenic content of rice (it may be high enough to be a health hazard), and there is quite recent evidence that the analytical chemistry community cannot get satisfactory results for the measurement of the relevant compounds in rice, even when the homogeneity and stability of the sample are not factors affecting the results. A further restriction of a 5-year time horizon (approximately) has also been imposed. 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). 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. 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. Writing reviews of some aspect of the measurement of arsenic compounds as described in the burgeoning literature is a popular activity. Compound-dependent responses, for which there is a plenty of evidence, are almost never acknowledged or discussed. 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. 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. 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. 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. 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.
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