AOAC ERP Fertilizers - December 2017

AOAC RESEARCH INSTITUTE AOAC OFFICIAL METHODS OF ANALYSIS (OMA) OMAMAN-24: DETERMINATION OF TOTAL SULFUR IN FERTILIZERS BY HIGH TEMPERATURE COMBUSTION

SUMMARY OF RESPONSES FROM ERP: ER 1

I AGREE that the method as revised, Total Sulfur in Fertilizers by High Temperature Combustion , is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL. I AGREE that the method as revised, Total Sulfur in Fertilizers by High Temperature Combustion , is now ready for publication in the Official Methods of Analysis of AOAC INTERNATIONAL. ER 3 According to Magruder data presented at the annual AAFPCO summer meeting in Pittsburg in 2016, Sulfur analysis by combustion showed slightly better RSD within Lab than gravimetric and Microwave. However, at this point I will disagree with moving the OMAMAN‐24 to first action pending the following: 1. Because one of the stated strength of the method is the simultaneity of analysis with nitrogen it would be prudent to present nitrogen data generated simultaneous with the sulfur data. 2. Information on sample throughput would also be of help 1. Table 1 is out-of-place. The First Action method recommendation is based upon the SLV study and as such there is no collaborative/interlaboratory data available yet. This would be appropriate at the next stage after the collaborative study has been completed, but should be deleted at this point. That said, based upon my next comment, a modified version of Table 1 would be appropriate if previous Elementar data from the SLV study could be compared with new Apparatus B/Figure 2 instrument data from another source(s). 2. The ERP expressed concerns that the method was primarily tailored to one manufacturer. Apparatus B and Figure 2 does adequately address the fact that another common approach/technology exists, but there are also concerns expressed regarding its performance. If data could be generated from one competent lab that uses the Apparatus B/Figure 2, then this comparative data would go a long way to satisfy anyone’s concern about the method being developed for only one instrument manufacturer. 3. This may be beyond the scope of simply determining whether the authors addressed the concerns raised by the ERP, but extra work will be required to place the document in First Action format. For example, sections B and C will require the manufacturer, model or part number, and corporate headquarters and the word “or equivalent.” Also, more information on Preparation of Test Samples (i.e. Prepare an analytical sample of sufficiently small particle size to ensure sufficient representation… is too vague; how to prepare the sample and particle size range is recommended). Reconciling the difference between %S in the sample and mg S in the sample to weigh may need to be added to the calculations and/or in a Table. ER 2 ER 4

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