3. AOACRIFeedsFertilzerMethods-2018Awards

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W EBB : J OURNAL OF AOAC I NTERNATIONAL V OL . 101, N O . 2, 2018 383

ANIMAL AND PLANT NUTRITION, HEALTH, AND SAFETY Simultaneous Determination of Arsenic, Cadmium, Calcium, Chromium, Cobalt, Copper, Iron, Lead, Magnesium, Manganese, Molybdenum, Nickel, Selenium, and Zinc in Fertilizers byMicrowave Acid Digestion and Argon Inductively Coupled Plasma-Optical Emission Spectrometry Detection: Single-Laboratory Validation, First Action 2017.02

S HARON F. W EBB University of Kentucky, Division of Regulatory Services, 103 Regulatory Services Bldg, Lexington, KY 40546

A single-laboratory validation method for the simultaneous determination of nutrient and non-nutrient metals in commercial fertilizers was reviewed by the AOAC Expert Review Panel (ERP) and Stakeholder Panel for Fertilizers at the 2017 midyear AOAC INTERNATIONAL meeting. In addition to using 15 of the original 30 fertilizer materials from the previous Method 2006.03 collaborative study, NIST Standard Certified Reference Material 695 and Magruder check sample 2009-06 were also incorporated as accuracy, recovery, and repeatability materials. Method 2017.02 is suitable for the simultaneous determination of arsenic, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, molybdenum, nickel, selenium, and zinc in all major types of commercial fertilizer products by microwave digestion and inductively coupled plasma-optical emission spectroscopy analysis. With recoveries ranging from 92.8 to 103.2% for analytes above the LOQs, improved RSDs, and enhanced efficiency as compared with the previous method, Method 2006.03, the ERP recommended this method for First Action Official Methods SM Status. I n 2002, the fertilizer community began holding annual meetings, initially as the Metals Forum and now as the Methods Forum, to discuss method needs for determining trace metals in fertilizers due to the regulatory motivation to establish limits for certain metals (1). The first major development was Statement of Uniform Interpretation and Policy No. 25 based on risk assessment and the result based Received June 12, 2017. Accepted by NT July 24, 2017. This method was approved by the AOAC Expert Review Panel for Fertilizers-Metals as First Action. The Expert Review Panel 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 e-mail: sharon.webb@uky.edu DOI: https://doi.org/10.5740/jaoacint.17-0241

on the analytical capabilities of common instrumentation in state regulatory fertilizer laboratories (2). The second major result of these yearly meetings was a fully collaborated method, Method 2006.03 , which was the fruition of 4 years of analytical work from the combined efforts of chemists from regulatory, academic, industry, commercial, and private laboratories (3). From the continued annual forum meetings, new criteria were established so that this and other fertilizer methodologies could be improved, turnaround times decreased, new instrument technology introduced, quality systems evaluated, and other efficiencies realized. In September 2009, this method, including an in-depth statistical analysis of the results of a minilaboratory study, was presented to the stakeholders at the annual AOAC INTERNATIONAL meeting, and the community agreed with the findings of the Method Forum, so a single-laboratory validation (SLV) study was undertaken (4). The eventual method, Method 2017.02 , was first described in 2009, and, in 2014, the SLV was submitted to the AOAC Expert Review Panel (ERP; 1). Briefly, 1 g test portion is heated with either nitric acid (option 1) or nitric and hydrochloric acids (option 2) in a closed-vessel microwave digestion system at 200°C. The digestion test solution is diluted to a final volume of 100 mL and presented to an inductively coupled plasma-optical emission spectrometry instrument calibrated with acid-matched standard calibrant solutions. An ionization buffer (cesium) is used to minimize easily ionized element effects, and scandium and/or beryllium are used as the internal standard(s). Option 1 is applicable only to the non-nutrient metals, which are arsenic, cadmium, chromium, cobalt, lead, molybdenum, nickel, and selenium, and are called “ group A metals. ” “ Group B metals, ” or the nutrient metals, are defined as calcium, copper, iron, magnesium, manganese, and zinc. Option 2 is applicable to both group A and group B metals in fertilizers (1, 3, 4). The statistical requirements from the publication entitled, AOAC Guidelines for Single-Laboratory Validation of Chemical Methods for Dietary Supplements and Botanicals , was adopted by Methods Forum participants for performance requirements in 2008 (5, 6). These requirements can be seen in Table 1. AOAC Methods 2006.03 and 2017.02

03/10/2019