6. AOACSPIFANMethods-2018Awards

86

1390 Jaudzems : J ournal of AOAC I nternational V ol. 98, N o. 5, 2015

INFANT FORMULA AND ADULT NUTRITIONALS

Determination of Chloride in Infant Formula and Adult/ Pediatric Nutritional Formula by Automated Potentiometry: Single-Laboratory Validation, First Action 2015.08 Gregory G. Jaudzems Nestlé Quality Assurance Center, 6625 Eiterman Rd, Dublin, OH 43017

A potentiometric method was evaluated to establish an international consensus method for the determination of chloride in infant formula and adult/pediatric nutritional formula. StandardMethod Performance Requirements (SMPR ® ) for chloride were approved by the AOAC Stakeholder Panel for Infant Formula and Adult Nutritionals (SPIFAN) and are described in AOAC SMPR 2014.015 (1). The single-laboratory validation (SLV) was conducted on 17 SPIFAN matrixes and a Standard Reference Material [SRM; National Institute of Standards and Technology (NIST) 1849a Infant Formula/Adult Nutritional Formula]. LOQ, precision, and accuracy were assessed in this study. On March 17, 2015, anAOAC Expert Review Panel (ERP) on Infant Formula and Adult Nutritionals reviewed the SLV study on the potentiometric method for determination of chloride and adopted the method as AOAC Official Method SM 2015.08 . The next step in the process will be to have a multiple laboratory study performed using SPIFAN kits, after which the ERP may recommend the method to the AOAC Official Methods Board for Final Action Status (2). [Applicable to the determination of chloride in ready-to-feed (RTF) liquid concentrate and powder products from levels of 1.4 to 1060 mg/100 g reconstituted product or RTF liquids.] See Tables 2015.08 A–C for the results of the SLV study supporting acceptance of the method. The method was evaluated against Standard Method Performance Requirements AOAC SMPR 2014.015 (1). A. Principle Reconstitute powder samples by dissolving 25 g powder sample in 200 g warm water (40°C). Add 50 mL of 2% (v/v) nitric acid solution. Stir with a magnetic stirrer until mixed or finely suspended. Ensure pH is <1.5. Titrate potentiometrically against standardized silver nitrate (AgNO 3 ) solution, 0.1 M, using a silver electrode to detect the end point. B. Apparatus Common laboratory equipment and, in particular, the following: AOAC Official Method 2015.08 Determination of Chloride in Infant Formula and Adult/Pediatric Nutritional Formula Potentiometry First Action 2015

Received May 26, 2015. Accepted by SG July 2, 2015. The method was approved by the Expert Review Panel on Infant Formula and Adult Nutritionals as First Action. The Expert Review Panel on 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. Corresponding author’s email: greg.jaudzems@us.nestle.com DOI: 10.5740/jaoacint.15-136 A direct potentiometric method involving titration against a standard volumetric silver nitrate solution using a silver electrode to detect the end point was evaluated for the determination of chloride in infant formula and adult/pediatric nutritional formula. It was assessed for compliance against AOAC Standard Method Performance Requirements (SMPR ® ) established by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN). A single-laboratory validation (SLV) study was conducted as a first step in the process to validate the method. In this SLV, 17 SPIFAN matrixes representing a range of infant formula and adult nutritional products were evaluated for their chloride content. The analytical range was found to be between 1.4 and 1060 mg/100 g reconstituted product or ready-to-feed (RTF) liquid. The LOQ was estimated as 1.4 mg/100 g. Method repeatability was between 0.03 and 1.60% in the range of 20 to 167 mg/100 g RTF, and intermediate precision was between 0.09 and 2.77% in the same range. Recovery values based on spiking experiments at two different levels of chloride ranged from 99.0 to 103% for 15 different SPIFAN products. Evaluation of trueness was performed on National Institute of Standards and Technology Standard Reference Material 1849a (Infant/Adult Nutritional Formula) and showed 97.2% of the theoretical value, with no bias at the 95% confidence level. Based on the results of the SLV, the method met the SMPR and was approved as a First Action method by the AOAC Expert Review Panel on Infant Formula and Adult Nutritionals on March 17, 2015.