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Fluid Journal : Early Spring 2011
7 The Fluid Journal Early Spring 2011 Method 959.03 is dependent. Method 983.01, a liquid chromatographic method, also is not reliable for determination of urea in the cited class of fertilizers because in most, if not all cases, there is co-elution of a non-urea peak with the urea peak. As a consequence, there presently exits no official method suitable for regulatory analysis for urea (or urea N) in commercial fluid fertilizers containing the described urea-formaldehyde reaction products even though dissolved, unreacted urea is always a substantial component of such products and is quantitatively claimed on the registration labels thereof. Figure 4. Controlled reaction of urea, formaldehyde, and ammonia A better way? A liquid chromatographic method from a proposed collaborative study (using a different column, eluent, and operational parameter from 983.01) has been developed and in industry use for over a decade for the determination of urea in the class of fluid fertilizers noted here as not being suitable for urea analysis by present official methods. It would seem to be a suitable candidate for the collaborative study to provide an official method for use in the cases cited here where present official methods are unsuitable. The liquid chromatographic method was developed by Tessenderlo Kerley, Inc. of Phoenix, Arizona, in collaboration with ten other laboratories of which five were commercial labs and the other five were state labs. This method is based on liquid chromatography that separates efficiently and clearly and calculates the amount of unreacted urea from the other N-containing compounds present in the solution that could be used to calculate the amount of CRN/SRN in solution. Using an accurate methodology to determine the amount of CRN/SRN in solution prevents inaccurate and false reporting. This method has been approved by the AOAC International