AOAC Final Action Methods in 2017

536 P ACQUETTE & T HOMPSON : J OURNAL OF AOAC I NTERNATIONAL V OL . 101, N O . 2, 2018

INFANT FORMULA AND ADULT NUTRITIONALS Minerals and Trace Elements in Milk, Milk Products, Infant Formula, and Adult/Pediatric Nutritional Formula, ICP-MS Method: Collaborative Study, AOAC Final Action 2015.06, ISO/DIS 21424, IDF 243

L AWRENCE H. P ACQUETTE and J OSEPH J. T HOMPSON 1 Abbott Nutrition, 3300 Stelzer Rd, Columbus, OH 43219

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Collaborators: I. Malaviole; R. Zywicki; F. Woltjes; Y. Ding; A. Mittal; Y. Ikeuchi; B. Sadipiralla; S. Kimura; H. Veltman; A. Miura

M ineral analyses in which samples are prepared via closed-vessel microwave digestion and analyzed by either inductively coupled plasma (ICP)-atomic emission spectrometry (AES) or ICP-MS have become commonplace in the analytical laboratory, often replacing older methods that use flame or graphite furnace atomic absorption spectrophotometry because of the ICP ’ s multielement capability and excellent sensitivity. As ICP technology and the sample preparation technique have evolved, a need to update official methods was noted. For example, AOAC Official Method SM 2011.14 (ICP-AES, after closed-vessel microwave digestion of the sample in nitric acid – hydrogen peroxide) was introduced as a more modern version of AOAC Official Method 984.27 (open-vessel digestion with dangerous perchloric acid), which became a Final Action method in 1986. These methods covered analytes Na, Mg, P, K, Ca, Fe, Mn, Zn, and Cu. The AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) has recommended that the newest ICP methods be specifically examined for their performance on infant formula and child/adult matrixes so that there can be no doubt about the reliability of these methods in the case of regulatory or trade disputes. The goal is to develop and collaboratively study test methods that have the reproducibility/robustness needed by infant formula manufacturers as they market their products in many different countries. Such test methods would be recommended as new or replacement Codex Type II methods and be recognized as dispute-resolution methods. SPIFAN developed a set of Standard Method Performance Requirements (SMPRs SM ) for minerals. These contain the analytical range, recovery, LOQ, repeatability, and reproducibility of the test methods that are needed to be fit-for- purpose. Table 1 shows the two SMPRs (1, 2) developed for minerals combined into a single table. A collaborative study (also referred to as multilaboratory testing, or MLT; publication pending) has recently been concluded for Method 2011.14 , the ICP-AES method mentioned above, to test method performance relative to the SMPR parameters shown in Table 1. On the ICP-MS side, one MLT study of AOAC Official Method 2011.19 has already been completed and published for ultratrace elements Cr, Mo, and Se (3). AOAC Final Action Official Method 2015.06 extended Method 2011.19 to include the nine major/trace elements mentioned above in addition to the three ultratrace elements. We report herein the results of an MLT study of this 12-element method. The samples used in this study were identical to those used in the MLT study of Method

AOAC Final Action Official Method SM 2015.06 “ Minerals and Trace Elements in Milk, Milk Products, Infant Formula and Adult/Pediatric Nutritional Formula, ICP-MS Method ” was collaboratively studied. Note that “ milk, milk products ” has now been added to the title of the Final Action method because whole milk and several dairy ingredients were successfully incorporated into the collaborative study for the purpose of developing an International Organization for Standardization/International Dairy Federation standard (ISO/DIS 21424; in progress). The method determines sodium, magnesium, phosphorus, potassium, calcium, iron, manganese, zinc, copper, chromium, molybdenum, and selenium by inductively coupled plasma (ICP)-MS after microwave digestion. Ten laboratories participated in the study, and data from five different model ICP-MS units were represented. Thirteen products, five placebo products, and six dairy samples were tested as blind duplicates in this study, along with a standard reference material, for a total 50 samples. The overall repeatability and reproducibility for all samples met Standard Method Performance Requirements put forth by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals, with a few exceptions. Comparisons are made to ICP-atomic emission data from a collaborative study of AOAC Official Method 2011.14 carried out concurrently on these same samples. Received August 15, 2017. Accepted by SG September 13, 2017. The method was approved by the AOAC Official Methods Board as Final Action. See “ Standards News, ” (2016) Inside Laboratory Management , March/April 2017 issue. The AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) invites method users to provide feedback on the Final Action methods. Feedback from method users will help verify that the methods are fit for purpose and are critical to gaining global recognition and acceptance of the methods. Comments can be sent directly to the corresponding author. 1 Corresponding author ’ s e-mail: joseph.thompson@abbott.com Supplemental Information is available on the J. AOAC Int . Web site, http://aoac.publisher.ingentaconnect.com/content/aoac/jaoac DOI: https://doi.org/10.5740/jaoacint.17-0318