Speciation Analysis Using HPLC-ICP-MS: Arsenic in Rice

The contamination of apple juice and rice with potentially harmful arsenic compounds has been highlighted in the news recently, including in a November 2012 article from Consumer Reports (1). For most people, rice is far and away the major source of potentially harmful arsenic compounds in our diet. Relevant agencies have recently issued revised guidelines for human consumption, and there is discussion concerning possible regulation of the arsenic content of foods. Analytical methods capable of distinguishing between inorganic and methylated compounds are necessary to support any such regulation, because arsenic compounds vary widely in toxicity. Recent articles in the analytical chemistry literature illustrate the difficulties of making reliable measurements of the arsenic compounds in rice. Sample preparation is challenging, there is no agreement over the best chromatographic conditions, compound-dependent responses are evident, validation is difficult (if not impossible), and there is ambiguity over the severity of starch matrix effects. In a recent web seminar, Julian Tyson, professor of chemistry at the University of Massachusetts, Amherst, explained how to develop a reliable method for arsenic speciation. Below, he answers questions raised during the web seminar. A recording of the web seminar titled "Speciation Analysis: A Critical Look at Methods Involving HPLC with ICP-MS Detection, with a Focus on Rice" is available for free at http://www.spectroscopyonline.com/ArsenicRiceWebinar2013