AOAC RI ERP EBOOK FOR FERTILIZERS

EXPERT REVIEW PANEL (ERP) FOR FERTILIZERS

EXPERT REVIEW PANEL FOR FERTILIZERS - UREA

Is this method recognized or adopted by another agency outside of AOAC? 1) Not at my knowledge 2) N/A 3) As an AOAC fertilizer method, this method is recognized and could be utilized by our laboratory for fertilizer sample analysis. 4) Yes Does your organization support the proposed modification being submitted to AOAC? Please indicate explanations. 3) Yes, the proposed modification is supported. The data presented in the "Evaluation of the Determination of Free Urea in Water-Soluble Liquid Fertilizers containing Urea and Ureaforms by Urease Method and by HPLC Methods" supports the need to provide this clarification. 4) Yes,The authors present significant and sufficient evidence that Official Method 959.03 is not suitable for urea-formaldehyde products. In this situation, HPLC-based methods are preferred, particularly AOAC Official Method 2003-14. It is clear that with one of the major sources of variability in the Official Method 959.03 is the source of urease, which should be further specified. Does your organization, have any additional suggestions regarding the modification of this method? 3) The following 4 typo/transcription type comments are submitted for consideration regarding the "Evaluation of the Determination of Free Urea in Water-Soluble Liquid Fertilizers containing Urea and Ureaforms by Urease Method and by HPLC Methods" document: Comment 1: Page 4, line 3 - change "...difference of the unreacted free urea subtracted from total the N, both..." to "...difference of the unreacted free urea subtracted from the total N, both..." Comment 2: Page 11, line 4 - update the Table 3 values to reflect changes described in Comment 3. Comment 3: Page 12 Table 3. The % Urea-N HPLC Method AOAC 2003.14 (Means from two Labs) entry for Fertilizer Sample 9 should be 11.73 instead of 11.37 (transcribed from Table 2). This would then make the %Urea-N Difference Urease-HPLC (Mean) become -2.84. Comment 4: Page 16, line 2 - confirm the data is in Table 5 vs. Table 6. 4) No 1) Yes, my organisation supports the change 2) Yes, many of our formulas are urea based. 1) No 2) No

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