SPSFAM Heavy Metals ERP Book

K ubachka et al .: J ournal of AOAC I nternational V ol . 100, N o . 4, 2017  1077

RESIDUES AND TRACE ELEMENTS

Multilaboratory Validation of First Action Method 2016.04 for Determination of Four Arsenic Species in Fruit Juice by High-Performance Liquid Chromatography–Inductively Coupled Plasma–Mass Spectrometry K evin K ubachka and D ouglas T. H eitkemper U.S. Food and Drug Administration, Forensic Chemistry Center, 6751 Steger Dr, Cincinnati, OH 45237 S ean C onklin U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, 5100 Paint Branch Pkwy, College Park, MD 20740 Collaborators: S. Conklin; T. Ehresmann; T. Hanley; H. Lyons; K. Min; D. Ouellette; K. Seely; C. Smith; M. Swarbrick; B. Wels; Z. Kassa

A rsenic is widely distributed in the environment from natural sources such as volcanic activity and erosion and from anthropogenic activities, including the burning of fossil fuels, mining, ore smelting, and the use of arsenic- containing pesticides, herbicides, and wood preservatives (1, 2). Because of its presence in soil and water, small amounts of arsenic are found in foods. Arsenic in the environment and in food exists in many chemical forms; however, from a public health perspective, arsenic may be categorized broadly as inorganic arsenic (iAs), the primary toxic form, or as organic arsenic, which is generally considered less toxic. iAs species, specifically arsenite [As(III)] and arsenate [As(V)], are known carcinogens, and the consumption of iAs has also been associated with noncancer health effects such as cardiovascular disease, neurotoxicity, and diabetes (2). Organic forms, including monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and arsenosugars, are considered significantly less toxic than iAs, whereas some organic forms commonly found in seafood, such as arsenobetaine and arsenocholine, are considered nontoxic (3). Recently, the Joint Food and Agriculture Organization/ World Health Organization Expert Committee on Food Additives concluded that in addition to drinking water, food can be a significant contributor to iAs exposure (4). Drinking water contains primarily iAs, and the U.S. Environmental Protection Agency set a regulatory limit for total arsenic in drinking water at 10 μg/L (5). For many years, the U.S. Food and Drug Administration (FDA) has been monitoring total arsenic concentrations in a variety of foods, including fruit juices, through the Total Diet Study program (6). Some fruit juices, however, have been shown to contain significant amounts of less-toxic organic arsenic compounds, primarily DMA and MMA, in addition to iAs (7). Therefore, the quantitation of individual arsenic species of varying toxicity in fruit juice samples is necessary to improve estimates of dietary exposure and evaluate health impacts of iAs in fruit juices. HPLC coupled with inductively coupled plasma (ICP)- MS is the primary method used for arsenic speciation and is well reviewed (8). Anion-exchange chromatography is often used to separate the four main arsenicals, i.e., As(III), As(V), DMA, and MMA, whereas ICP-MS offers ultralow detection

Before being designated AOAC First Action Official Method SM 2016.04, the U.S. Food and Drug Administration’s method, EAM 4.10 High Performance Liquid Chromatography–Inductively Coupled Plasma–Mass Spectrometric Determination of Four Arsenic Species in Fruit Juice, underwent both a single-laboratory validation and a multilaboratory validation (MLV) study. Three federal and five state regulatory laboratories participated in the MLV study, which is the primary focus of this manuscript. The method was validated for inorganic arsenic (iAs) measured as the sum of the two iAs species arsenite [As(III)] and arsenate [As(V)], dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) by analyses of 13 juice samples, including three apple juice, three apple juice concentrate, four grape juice, and three pear juice samples. In addition, two water Standard Reference Materials (SRMs) were analyzed. The method LODs and LOQs obtained among the eight laboratories were approximately 0.3 and 2 ng/g, respectively, for each of the analytes and were adequate for the intended purpose of the method. Each laboratory analyzed method blanks, fortified method blanks, reference materials, triplicate portions of each juice sample, and duplicate fortified juice samples (one for each matrix type) at three fortification levels. In general, repeatability and reproducibility of the method was ≤15% RSD for each species present at a concentration >LOQ. The average recovery of fortified analytes for all laboratories ranged from 98 to 104% iAs, DMA, and MMA for all four juice sample matrixes. The average iAs results for SRMs 1640a and 1643e agreed within the range of 96–98% of certified values for total arsenic.

Received December 21, 2016. Accepted by AK February 28, 2017. Corresponding author’s e-mail: kevin.kubachka@fda.hhs.gov DOI: 10.5740/jaoacint.16-0429