AOAC RI ERP EBOOK FOR FERTILIZERS

Table-6 AOAC 959.03 (Urease Method) vs. AOAC 2003.14 (HPLC) Results for Analyses of Unreacted Urea in Urea-Triazone Liquid Fertilizers Urease HPLC Urease HPLC Urease vs HPLC 1 A 0.20 0.34 20.2 33.7 60 20ml 1% Solution B 0.11 0.16 10.9 16.1 68 C 0.24 0.32 23.5 32.1 73 D 0.27 0.35 27.3 35.1 78 2 A 0.17 0.34 16.9 33.7 50 10ml Glycerol Ext. B 0.08 0.16 7.5 16.1 47 C 0.14 0.32 14.2 32.1 44 D 0.25 0.35 25.4 35.1 72 2 A 0.34 0.34 34.3 33.7 102 20ml Glycerol Ext. B 0.17 0.16 17.0 16.1 106 C 0.32 0.32 32.4 32.1 101 D 0.33 0.35 33.4 35.1 95 3 A 0.15 0.34 15.0 33.7 45 20ml 1% Solution B 0.10 0.16 9.5 16.1 59 C 0.18 0.32 17.8 32.1 55 D 0.32 0.35 32.4 35.1 92 4 A 0.18 0.34 18.1 33.7 54 20ml 1% Solution B 0.11 0.16 11.0 16.1 68 C 0.18 0.32 18.4 32.1 57 D 0.24 0.35 23.5 35.1 67 5 A 0.17 0.16 6.9 16.1 43 Two Tablets B 0.13 0.32 13.0 32.1 40 6 B 0.17 0.16 16.9 16.1 105 10ml Glycerol Ext. C 0.33 0.32 33.1 32.1 103 6 B 0.17 0.16 17.1 16.1 106 20ml Glycerol Ext. C 0.33 0.32 33.2 32.1 103 7 A 0.34 0.34 34.0 33.7 101 20ml 1% Solution B 0.16 0.16 16.2 16.1 101 C 0.32 0.32 32.3 32.1 101 D 0.33 0.35 33.0 35.1 94 Sample amount used In quantitative terms, hydrolyses of urea in these four fertilizer samples by these urease sources tended to be in the range of 40-80%. Each of the urease sources should have hydrolyzed all the urea in these type of fertilizers based on the tests done using the pure urea (Table 4), within the scope of the Urease Method. Fertilizer “B” contains only about half of the urea of the other three fertilizer samples (A, C, and