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SPECIAL GUEST EDITOR SECTION
New and Improved Methods of Analysis for Plant Food Materials The AOAC Agricultural Inputs Community’s Collaborations: A Decade of Method Forum Outcomes and Other Work
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his Special Guest Editor Section includes contributions related to the development and validation of analytical methods for fertilizers, soil amendments, and beneficial substances. It is with great excitement that we present these papers. As a collection, they represent a leap forward with respect to analytical methodology for the discipline. With a few exceptions, the studies presented in this section were undertaken and guided as activities of the Methods Forum, which serves as the “stakeholder panel” for the Fertilizer Community. The Forum meets annually, immediately following the Association of American Plant Food Control Officials (AAPFCO) Midyear Meeting, to discuss how to best meet the need for new or improved fertilizer analytical methods. The Methods Forum is comprised of scientists from industry, regulatory agencies, regulatory laboratories, academia, commercial laboratories and instrument vendors. The Methods Forum began in 2002 as the “Metals Forum” in response to the needs for an analytical method to address the AAPFCO call for a Statement of Uniform Interpretation and Policy No. 25. The outcome was AOAC Official MethodSM 2006.03. With the success of the model apparent, the “Metals Forum” evolved into the “Methods Forum” in 2008 to address the myriad of analytical needs brought forward by attendees. Forum topics are prioritized within the Community based on needs, such as the development or selection of analytical methods as new commercial DOI: 10.5740/jaoacint.SGEThiex_Intro
fertilizer products emerge; changes to state, federal, or trade regulations; use in trade specifications; use in monitoring fraud; potential health, safety, or adulteration issues; new instrument technology and efficiencies; decreased sample turnaround time; and data quality. Upon prioritization, subsequent efforts by Forum volunteers center on the development and validation of analytical methods to meet as many of the needs as possible. The Methods Forum has been conceived, organized, and driven, in all aspects, by Bill Hall of The Mosaic Co. He has organized and led each of the 13 annual forums. His energy and foresight are reflected by the success of the Methods Forums, the large attendance, and the commitment of the methods “champions” and volunteers. It is with heartfelt thanks that these papers are dedicated to Bill Hall for his many years of leadership. This collection of papers is very comprehensive for the fertilizerrelated industries, covering many aspects of analytical testing, including phosphorus, potassium, sulfur, secondary micronutrients, heavy metals, adulterants, slow-release fertilizers, and beneficial substances. Those activities not associated with the Methods Forum are so noted. Papers included in this section include the following: In three manuscripts, Medina et al. present the validation of a 180 day soil incubation method to characterize nitrogen release patterns of enhancedefficiency fertilizers, an accelerated method for use in production of laboratory environments to approximate the results of the 180 day extraction, and the statistical correlation between the two analytical methods. These three
Nancy J. Thiex Special Guest Editor
manuscripts offer much of the work done by Medina in her doctoral thesis under the direction of Jerry Sartain and Tom Obreza at the University of Florida. Bartos et al. present the validation of two analytical approaches for the determination of phosphorus (P) and potassium (K) by inductively coupled plasma-optical emission spectrometry. One option is the determination of acid-soluble P and K, which estimates the total P and K content in phosphate ores and fertilizer materials. The second option validates the determination of citrate-EDTA soluble P and K, which represent fractions considered available to plants. Webb et al. present the validation of both a modification of the digestion procedure for AOAC Official MethodSM 2006.03 to improve recoveries of certain metals, and an extension of the method to include calcium, copper, iron, magnesium, manganese, and zinc. The proposed multi-analyte inductively coupled plasma-atomic emission
642 Thiex: Journal of AOAC International Vol. 97, No. 3, 2014 spectrometry method is for 14 metals with two alternative digestion methods. Hojjatie and Abrams present the validation of the extension of AOAC SM Official Method 2003.14 for the LC determination of biuret in ureabased fertilizer materials. In a second technical report, Abrams et al. report on the omission of a copper sulfate catalyst in determining total nitrogen in nonnitrate fertilizers. Lamar et al. present a validation of an analytical method for the determination of humic and fulvic acids in humic products by alkaline extraction and gravimetric determination. This work was a collaboration of the International Humic Substances Society and the Humic Products Trade Association. Bernius et al. present the validation of an analytical method using combustion for the determination of total sulfur in fertilizers. Rezende and Coelho present the determination of total arsenic and arsenic(III) in phosphate fertilizers by atomic absorption after ultrasoundassisted extraction. This work was not a
Methods Forum activity, but is an area of mutual interest. Hall and Siegel evaluate commonly used analytical methods for the determination of acid-soluble phosphate in internationally traded phosphate fertilizers. This was the effort of a working group of The International Fertilizer Association. Hall et al. report on the effect of varying particle size on the ability to mix, and sample bulk blend fertilizers. While not an analytical method, particle size can have an effect on data quality. This was the effort of a working group of The Florida Department of Agriculture and Consumer Services and the Florida Fertilizer and Agrochemical Association. With a bit of a diversion from analytical method validation, Wegner reports on the process improvement for analysis of custom-blended fertilizers in a regulatory laboratory. This work was not a Methods Forum activity, although Wegner is a Forum participant. A 2013 paper titled A 5-Day Method for Determination of Soluble Silicon Concentrations in Nonliquid Fertilizer
Materials Using a Sodium CarbonateAmmonium Nitrate Extractant Followed by Visible Spectroscopy with Heteropoly Blue Analysis: SingleLaboratory Validation, by D. Sebastian, H. Rodrigues, C. Kinsey, G. Korndörfer, H. Pereira, G. Buck, L. Datnoff, S. Miranda, and M. Provance-Bowley was published in J. AOAC Int. 96, 251–259. Most of the method validation presented in this Special Section will move toward acceptance as an international standard, either by the AOAC process or the International Organization for Standardization (ISO) process, or ideally, by both processes. Dedicated to: Bill Hall, Metals Forum Champion and AOAC Agricultural Inputs Community Chair. —Nancy Thiex Professor Emerita South Dakota State University Thiex Laboratory Solutions LLC 46747 214th St Brookings, SD 57006
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Copyright: © 2014 AOAC INTERNATIONAL. This is an open-access article, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. As part of a team effort, several entities contributed to the open access rights for most of these manuscripts including the Association of American Plant Food Control Officials (AAPFCO), the Colorado Department of Agriculture, Elementar, the Florida Fertilizer and Agrochemical Association (FFAA), Harsco, the Magruder Check Sample Program, Potash Corp, Tessenderlo Kerley Incorporated (TKI), The Fertilizer Institute (TFI), The Mosaic Company and Thornton Laboratories.
