6. AOACSPIFANMethods-2018Awards

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Thompson et al. : J ournal of AOAC I nternational V ol. 98, N o. 6, 2015  1711

INFANT FORMULA AND ADULT NUTRITIONALS

Determination of Minerals and Trace Elements in Infant Formula and Adult/Pediatric Nutritional Formula by Inductively Coupled Plasma/Mass Spectrometry—A Performance Evaluation: Single-Laboratory Validation, First Action 2015.06

Joseph J. Thompson and Lawrence Pacquette Abbott Nutrition, 3300 Stelzer Rd, Columbus, OH 43219 Sharon L. Brunelle Brunelle Biotech Consulting, 14104 194th Ave NE, Woodinville, WA 98077

I n response to a need for reference methods for dispute resolution, the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) developed Standard Method Performance Requirements (SMPRs ® ) for Official Methods of Analysis for the ultratrace elements Cr, Mo, and Se (AOAC SMPR 2011.009; 1) and for the major/trace elements Ca, Mg, P, K, Na, Cu, Fe, Mn, and Zn (AOAC SMPR 2014.004; 2) in infant formula and adult/pediatric nutritional formula. AOAC Official Method SM 2011.19 (3) for determination of Cr, Mo, and Se, previously validated and shown to conform to the requirements of SMPR 2011.009, was expanded to include the minerals and trace elements contained in SMPR 2014.004. The method includes addition of internal standards (ISTDs) prior to microwave digestion of the sample in the presence of nitric acid and hydrogen peroxide. The diluted digestate is analyzed by inductively coupled plasma (ICP)/MS, and response ratios of analyte:ISTD in unknown samples are compared to external calibration curves to generate a result for each analyte. AOAC SMPR 2011.009 (1) provides the performance criteria for Cr, Mo, and Se, and SMPR 2014.004 (2) provides the performance criteria for Ca, Cu, Fe, Mg, Mn, P, K, Na, and Zn. The criteria are summarized in Table 1. This manuscript reports the results of the single-laboratory validation (SLV) and some limited reproducibility data for the ICP/MS method for 12 minerals and trace elements and comparison to the acceptance criteria. Based on the data presented, the AOAC Expert Review Panel on SPIFAN Nutrient Methods granted the method First Action status for the nine elements in March 2015. Note that similar data for just Cr, Mo, and Se were presented in a prior publication (4), but that SLV was conducted on a different set of matrixes. The SLV was conducted in accordance with the guidelines recommended by SPIFAN (5) and included determinations of specificity, linearity, LOQ, repeatability precision, and recovery/ accuracy in 11 matrixes identified by SPIFAN. The matrixes cover a variety of nutritional formulations, including powders and ready-to-feed (RTF) liquids made from milk, soy, whey, hydrolyzed protein, and amino acids, with and without intact protein. This SLV was performed by two analysts using two Agilent (Santa Clara, CA) ICP/MS instruments, one a 7500cx and the other a 7700x. The microwave oven was a CEM Corp. (Matthews, NC) MARS 5 with MARSXpress™ vessels.

Submitted for publication June 1, 2015. This method was approved by the Expert Review Panel for Infant Formula and Adult Nutritionals as First Action. The Expert Review Panel for Infant Formula and Adult Nutritionals invites method users to provide feedback on the First Action methods. Feedback from method users will help verify that the methods are fit-for-purpose and are critical for gaining global recognition and acceptance of the methods. Comments can be sent directly to the corresponding author or methodfeedback@aoac.org. 1  Corresponding author’s e-mail: joseph.thompson@abbott.com DOI: 10.5740/jaoacint.15-142 for the 12 elements in 11 SPIFAN matrixes and National Institute of Standards and Technology Standard Reference Material (SRM) 1849a was <5%, meeting the SMPR criterion for repeatability. Intermediate reproducibility (8 days, two analysts, two instruments) in the 11 SPIFAN matrixes was <5% for nine (Na, Mg, P, K, Mn, Fe, Cu, Zn, Se) of the 12 elements in all 11 matrixes. The mean reproducibility across 6–7 laboratories and seven SPIFAN matrixes ranged from 2.5% for Cu to 7.1% for P. Recovery from spiked matrixes varied from 90.1 to 109%, and accuracy of determination using SRM 1849a ranged from 96.2 to 107.7%, meeting the requirement of 90–110% recovery/accuracy. A method for determination of 12 minerals and trace elements (Na, Mg, P, K, Ca, Cr, Mn, Fe, Cu, Zn, Se, and Mo) in infant formula and adult/ pediatric nutritional formula was developed and evaluated in a single-laboratory validation. Some additional reproducibility data were obtained from a small interlaboratory study. The method involves microwave digestion of the sample followed by inductively coupled plasma/MS and uses Ge and Te as internal standards. The method is an extension of Official Method SM 2011.19 and was compared to AOAC Standard Method Performance Requirements (SMPRs ® ) 2011.009 and 2014.004 developed by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN). Repeatability precision