AOAC OMA# 2011.14 (Final Action Review)-OMB

2011.14 (MTE-01) MLT FOR ERP USE ONLY DO NOT DISTRIBUTE

P oitevin : J ournal of AOAC I nternational V ol . 95, N o . 1, 2012  177

FOOD COMPOSITION AND ADDITIVES

Determination of Calcium, Copper, Iron, Magnesium, Manganese, Potassium, Phosphorus, Sodium, and Zinc in Fortified Food Products by Microwave Digestion and Inductively Coupled Plasma-Optical Emission Spectrometry: Single-Laboratory Validation and Ring Trial E ric P oitevin Nestlé Research Center, QS Department Mineral Laboratory, Lausanne, Switzerland

spectrometry (ICP-OES) after microwave digestion is one of the priority methods identified as part of an AOAC pilot project to validate approximately 10 prospective methods deemed most urgently needed. Food-testing and nutrition laboratories need robust and efficient methods with well-characterized reference materials to facilitate compliance for minerals with nutritional labeling laws and claim requirements, provide traceability for food exports needed for acceptance in many foreign markets, and improve the accuracy of nutrition information that is provided to assist consumers in making sound dietary choices. ICP-OES is one of the most commonly used techniques within the food industry for accurate and cost-efficient routine analyses of nutritional minerals in food products, plants, pet food, raw materials, and feeding stuffs. This report describes a multielemental and simultaneous determination of nine major elements (calcium, copper, iron, potassium, magnesium, manganese, phosphorus, sodium, and zinc) in food products by ICP-OES after microwave digestion. Analytical procedure of validation of this extended and updated version of AOAC Method 984.27 was performed in accordance with ISO 17025 and AOAC guidelines. The main differences compared to AOAC Method 984.27 method concern ( 1 ) the use of microwave digestion systems (MDS) with open and closed vessels, and a single acid (nitric acid) for an optimized sample preparation in order to strengthen, improve element recoveries from difficult matrixes, and increase sample throughput, favoring safety precautions and time-saving for laboratory analysts; ( 2 ) the use of appropriate analytical wavelengths for each element of interest and of an automatically addedmix solution of appropriate internal standards and ionization buffer in order to correct for physical and chemical interferences, compensate for matrix effects induced by the complexity of the food samples, improve short-term accuracy (repeatability) and long-term stability (reproducibility and calibration curve validity in a long analysis batch); and ( 3 ) the extension of application to food matrixes, including infant formula covering all nine AOAC food triangle sectors. Procedure of method validation was performed through three independent studies on food-grade salts, and in-house reference and certified food materials. Single-laboratory validation (SLV). —With eight food-grade salts and 10 in-house and certified reference materials using ICP-OES equipment after a closed-vessel microwave-based optimized digestion with a Mars Xpress system (CEM Corp., Matthews, NC).

Submitted for publication September 2011. The recommendation was approved by the Methods-Centric Committee on Nutritional Elements in Food as First Action. See “Methods News,” (2011) Inside Laboratory Management , September/ October issue. Corresponding author’s e-mail: eric.poitevin@rdls.nestle.com DOI: 10.5740/jaoacint.CS2011_14 the AOAC triangle food sectors, which fulfilled AOAC criteria and recommendations for accuracy (trueness, recovery, and z -scores) and precision (repeatability and reproducibility RSD, and HorRat values) regarding SLVs and RTs. This multielemental method is cost-efficient, time-saving, accurate, and fit- for-purpose according to ISO 17025 Norm and AOAC acceptability criteria, and is proposed as an extended updated version of AOAC Official Method SM 984.27 for fortified food products, including infant formula. I mprovement of AOAC Official Method SM 984.27 for the determination of nine nutritional elements in food products by inductively coupled plasma-optical emission A single-laboratory validation (SLV) and a ring trial (RT) were undertaken to determine nine nutritional elements in food products by inductively coupled plasma-optical emission spectrometry in order to modernize AOAC Official Method SM 984.27. The improvements involved extension of the scope to all food matrixes (including infant formula), optimized microwave digestion, selected analytical lines, internal standardization, and ion buffering. Simultaneous determination of nine elements (calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, and zinc) was made in food products. Sample digestion was performed through wet digestion of food samples by microwave technology with either closed- or open-vessel systems. Validation was performed to characterize the method for selectivity, sensitivity, linearity, accuracy, precision, recovery, ruggedness, and uncertainty. The robustness and efficiency of this method was proven through a successful RT using experienced independent food industry laboratories. Performance characteristics are reported for 13 certified and in-house reference materials, populating