Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers submicron to submillimeter direct sampling of materials for their elemental composition over levels ranging from single ng/g to weight percent concentrations. Detection levels depend on the laser ablation spot size, element properties and isotope abundance, and the technique is capable of the determination of the chemical or isotopic composition at (1) high spatial resolution, and (2) large area sampling (mm<sup>2</sup>) for bulk sample analysis. In this study, we present a LA-ICP-MS determination of the spatial distribution of multiple elements in several types of rice. The bio-images obtained from the analysis allowed for correlation between elemental content (arsenic, iron, potassium, manganese, phosphorus and zinc), rice anatomy and processing. In brown rice, the highest accumulations of toxic and nutrient elements were in the husk/bran layers. For white rice, similar results were observed with a very narrow or non-existent husk/bran layer, consistent with the rice milling processing in which the outer layers of the grains are removed. In parboiled rice, elemental distributions were uniform throughout the grain, indicating that both nutrient and toxic elements have migrated towards the center of the grain.<br/>Another example of the use of LA-ICP-MS is for rapid elemental screening of food samples. Solid samples were combined with several internal standards (premixed in a cellulose matrix modifier), pressed using a pellet press, and analyzed by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). Quantification was performed using an in-house prepared standard material based on a powdered mixture of several food products, including rice, cocoa, oyster, and spinach powders. The choice of multiple internal standards for the analysis of the same elements ensures accurate quantification. The LA-ICP-MS method was validated using food reference materials, as well as by comparison with food samples analyzed by microwave digestion followed by ICP-MS analysis. Figures of merit and analytical performance of the method are similar to those obtained by solution ICP-MS for the samples of interest.

Direct elemental analysis of food by laser ablation inductively coupled plasma mass spectrometry

254th National Meeting (2017)

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