6. AOACSPIFANMethods-2018Awards

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198 B olong et al .: J ournal of AOAC I nternational V ol . 99, N o . 1, 2016 Infant Formula and Adult Nutritionals

Determination of Chloride in Infant Formula and Adult/ Pediatric Nutritional Formula by Potentiometric Titration: Single-Laboratory Validation, First Action 2015.07 W u B olong , Z hang F engxia , 1 M a X iaoning , and Z hou F engjuan Comprehensive Test Center of Chinese Academy of Inspection and Quarantine, Gao Bei Dian North Rd A3, Chao Yang District, Beijing, People’s Republic of China S haron L. B runelle Brunelle Biotech Consulting, 14104 194th Ave NE, Woodinville, WA 98077

Method Performance Requirement (SMPR ® ) 2014.015, “ Standard Method Performance Requirements for Determination of Chloride in Infant and Adult/Pediatric Nutritional Formula” (1). National Food Safety Standard GB 5413.24-2010, “Determination of chlorine in foods for infants and young children, milk and milk products,” is a Chinese nationally enforced testing method published by the Ministry of Health in 2010 as Notice 7. The notice includes 66 national standards in the area of dairy products and forms the regime of Chinese dairy product safety national standards. There are two methods within GB 5413.24-2010: one is a potentiometric titration method, and the other is a traditional titration method using a color indicator to determine the end of titration. The potentiometric titration method in GB 5413.24-2010 has a limitation in the end point determination or in precise titrant volume recording due to being an older titration technique using older instrumental analysis. A new potentiometric titration method was therefore developed at the Comprehensive Test Center of Chinese Academy of Inspection and Quarantine (CAIQTEST), which applied a modern, sophisticated, automatic titration system for enhancing the precision, accuracy, and efficiency of testing. It is a high-throughput, practical method that can be used in routine testing. CAIQTEST is a national institute under the leadership of Chinese Academy of Inspection and Quarantine (CAIQ) and operating as a third-party inspection agency in accordance with ISO/IEC 17025. CAIQ is a national public institute for researching and developing science and technology to be applied in inspection and quarantine. The mission of CAIQ is mainly to conduct research on the applied science of inspection and quarantine, as well as basic, high-tech, and soft science, with the focus on solving general and comprehensive problems and emergent and pivotal issues related to the administration of inspection and quarantine. CAIQ provides technical support to the policy making related to inspection and quarantine for China’s central government, and provides technical assistance to the law enforcement duties of the General Administration of Quality Supervision, Inspection, and Quarantine.

A potentiometric method for determination of chloride was validated against AOAC Standard Method Performance Requirement (SMPR ® ) 2014.015. Ten AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) matrixes, including National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1849a, were tested in duplicate on 6 independent days. The repeatability (RSD r ) ranged from 0.43 to 1.34%, and the intermediate reproducibility (RSD iR ) ranged from 0.80 to 3.04%. All results for NIST SRM 1849a were within the range of the certified concentration (701±17 mg/100 g). Recovery was demonstrated with two overspike levels, 50 and 100%, in the 10 SPIFAN matrixes. Samples were tested in duplicate on 3 different days, and all results were within the SMPR requirement of 95 to 105%. The LOQs of the method for powdered products and ready-to-feed or reconstituted products were 20 mg/100 g and 2.2 mg/100 mL, respectively. A wide analytical range from the LOQ to 99.5% chlorine content can be reached with an appropriate dilution factor, but in practice, the upper analytical value observed in routine matrix testing was approximately 1080 mg/100 g in skim milk powder. This is a rapid, simple, and reliable chlorine-testing method applicable to infant formula, adult nutritionals, and ingredients used in these dairy-based products, such as skim milk powder, desalted whey powder, whey protein powder, and whole milk powder. I n response to a need for a reference method for dispute resolution, the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) developed Standard Received June 01, 2015. Accepted by AK July 08, 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: zhangfengxia@caiqtest.com DOI: 10.5740/jaoacint.15-0143

Single-Laboratory Validation Study

The validation study compared the results of the method to the criteria of AOAC SMPR 2014.015. The requirements are presented in Table 1. Validation experiments included determination of system suitability, precision, accuracy, LOQ, and analytical range of the method.