The United States Food and Drug Administration (FDA) currently uses liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS) to regulate the proposed action level, or limit, of 100 parts per billion (ppb) for inorganic arsenic (iAs) in infant rice cereal. This level seeks to reduce infant exposure to inorganic arsenic. However, the best way to prevent rice that is highly contaminated with inorganic arsenic is to keep it out of the food supply in the first place. This presentation will discuss a newly developed inorganic arsenic test method designed to be put into place upstream in the supply chain, such as at rice mills. This method extracts arsenic from the rice using dilute muriatic acid available from hardware stores as a swimming pool pH adjuster. 10 grams of rice and 100 mL of 1% muriatic acid are boiled for 40 minutes on a hotplate. The rice/extract slurry is cooled and then mixed with premeasured and packaged sulfamic acid. Premade sodium borohydrate tablets are added, and the flask is capped with a HgBr saturated filter paper holder. The reagents and rice slurry react to generate AsH3 gas which rises in the flask and is collected by filter paper in the cap. The filter paper darkens when exposed to AsH3 gas. iAs in the sample is quantified by measuring the darkness of the stained filter paper using a battery powered digital spectrometer. This method costs less than $2 per sample, requires no expensive instrumentation, no laboratory ventilation, and no highly trained analysts. The kits come pre-calibrated and the total analysis time is 1 hour per sample. We will compare the field test method’s accuracy and cost to the LC-ICP-MS methods, and discuss steps taken to improve the kit’s accuracy and detection limits.

A scalable field test method to speciate arsenic in rice for less than $2 per sample

255th National Meeting (2018)

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