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Fluid Journal : Early Spring 2011
8 The Fluid Journal Early Spring 2011 Figure 5. Nitrogen release pattern from urea and Triazone. and adopted by the Association of Plant Food Control Officials (AAPFCO). It can also be used for the determination of CRN/SRN in fluid fertilizers containing water-soluble, urea-formaldehyde reaction products. It also covers urea- containing N fluid fertilizers and, in particular, aqueous urea solution. The method is quantitative and applicable to the determination of urea (usually expressed as urea N) in commercial water-soluble urea-formaldehyde products, urea-containing fluid N fertilizers, and aqueous urea solutions. It could also be used for the determination of biuret contents in urea solutions. A comparison of the determination of SRN in different commercially available fluid fertilizers containing water-soluble urea-formaldehyde reaction products is shown in Table 1. Urease methodology does not accurately account for the free urea in these fluid fertilizers. To determine the CRN/SRN contents of these fertilizers one has to know the amount of free urea accurately. The reasons are: • SRN/CRN coming from the cyclic Triazone moiety and from the ureaform constituents • Free urea not providing slow-release N. Method HPLC (%) Urease (%) N-SURE 28-0-0 (72% SRN claimed) 72 88 FORMOLENE-PLUS 30-0-0 (60% SRN claimed) 60 77 N-SURE-PRO 30-0-0 0-0-0(50% SRN claimed) 50 68 CoRoN 28-0-0 (70% SRN claimed) 50 70 NITRO-30 30-0-0 (85% SRN claimed) 46 * *Not determined by urease Table 1. A comparison of the determination of SRN in different commercially available liquid fertilizers containing water-soluble urea-formaldehyde reaction products. Figure 6. Typical high performance liquid chromatographic fingerprint of a Triazone fertilizer. Dr. Michael Hojjatie is R&D Director, and Dean Abrams is senior chemist with R & D Laboratories, Tessenderlo Kerley, Inc, Tucson, AZ. External Standard Report Sorted by Signal Multiplier 1.0000 Dilution 1.0000 Sample Amount 1.06800e-1 [g/100ml] (not used in calc.) Area Percent Report Sorted by Signal Multiplier 1.0000 Dilution 1.0000 Sample Amount 1.06800e-1 [g/100ml] (not used in calc.) Triazone Analysis