Throughout the US Food and Drug Administration’s routine monitoring of various juice samples for elemental contaminants, a limited number of samples exhibited unexpected behavior related to the arsenic content. Juice samples were subjected to total arsenic determination and those containing arsenic > 10 μg kg⁻¹ were subjected to arsenic speciation analysis using FDA Elemental Analysis Manual (EAM) 4.10 method (AOAC First Action Method 2016.04) to determine the concentration of iAs and other common organic arsenicals. For a subset of samples, the sum of the arsenic species was significantly less than the total arsenic value (i.e., mass balance < 65%), which is uncommon for a liquid-based matrix. Juice types that have exhibited this behavior include pomegranate, prune, and cherry juices. Causes for this issue were explored which ultimately led to an alternate sample preparation technique, extraction with 0.28 M HNO₃ along with heat, which resulted in drastically improved mass balances approaching 100%. The method proved robust, with both accurate and precise measurements for multiple juice samples analyzed by a total of four laboratories. Two laboratories performed a level 3 multilaboratory validation. This work discusses various issues that were encountered, attempts to determine the source of the problem, the eventual solution in the form of a modified extraction procedure, and the multilaboratory validation results.

在美国食品和药物管理局对各种果汁样品中元素污染物的例行监测中，有限数量的样品表现出与砷含量相关的意外行为。对果汁样品进行总砷测定，对含有砷> 10 μg kg ^-1的果汁样品采用 FDA 元素分析手册 (EAM) 4.10 方法（AOAC First Action Method 2016.04）进行砷形态分析，测定 iAs 和其他物质的浓度常见有机砷。对于样品的子集，砷物质的总和明显小于总砷值（即质量平衡< 65%），这对于液体基体来说是不常见的。表现出这种行为的果汁类型包括石榴汁、西梅汁和樱桃汁。我们对该问题的原因进行了探索，最终采用了替代的样品制备技术，即使用 0.28 M HNO ₃和加热进行萃取，从而使质量平衡显着改善，接近 100%。该方法被证明是可靠的，对总共四个实验室分析的多个果汁样品进行了准确和精确的测量。两个实验室进行了 3 级多实验室验证。这项工作讨论了遇到的各种问题，尝试确定问题的根源，以修改的提取程序的形式提出最终解决方案，以及多实验室验证结果。