Speciation of Arsenic in Rice by LC-ICP-MS on PlasmaQuant MS Elite Application Note · PlasmaQuant MS Elite

Introduction

According to the World Health Organization guide lines, the permissible level for total arsenic in drinking water is 10 ng/mL. Although no such limit exists for food products, the Food and Agriculture Organization / World Health Organization (FAO/WHO) recommend an intake no greater than 15 µg per kg body weight per week.

Next to drinking water, rice consumption is a major source of arsenic that concerns approximately 3 billion people. World rice consumption has risen from 156 million in 1960 to 496.6 million metric tons in 2013. Moreover, studies show that arsenic exposure is more critical in rice than in any other food stuff. For example, the arsenic level in rice is 10 times higher than in wheat and barley. In addition to direct ingestion, using rice straw for cattle feed increases the risk of arsenic exposure.

The toxicity of arsenic depends not only on the total concentration, but also its chemical forms as these differ in terms of mobility, toxicity and bioavailability. The inorganic trivalent arsenic (AsIII) and pentavalent arsenic (AsV) are the most toxic forms, whereas other common forms including the organic monomethyl arsenic (MMA) and dimethyl arsenic (DMA) have significantly reduced toxicities. Rice typically contains a high proportion of the inorganic forms of arsenic, emphasizing the importance of arsenic speciation in the analysis of rice samples.