I need to determine the concentration of organic forms of nitrogen in a fertilizer and distinguish them from urea.
The fertilizer is composed by ammonium nitrate, urea, and these organic forms. I outsourced the analysis to a lab which measured the total nitrogen with Dumas method, and the ammonium and the nitrate with AAS. Finally, they subtracted the ammonium and nitrate concentrations from the total conc. and claimed that it is the organic fraction. As reliable as these methods can be, they do not distinguish between the urea and other organic forms of nitrogen. I asked the lab if they could measure the urea and they said they couldn't, which I found odd.
Can you suggest some cheap methods to measure urea in a liquid fertilizer?
Total nitrogen can be determined through the oxidative digestion of all digestible nitrogen forms to nitrate, followed by quantitation of the nitrate. Kjeldahl method is the very old and conventional method but The enhanced Dumas method is an automated instrumental technique that is beginning to compete with the Kjeldahl method as the standard method of Nitrogen analysis due to its rapidness and ease of use. In Dumas process high cost initially but fast ,it requires 3/5 minutes for each sample analysis.
Prem Baboo Thanks but that didn't address my question. I'm asking about methods to distinguish between urea and other forms of organic nitrogen.
I imagine that in the matrix and the likely urea concentrations, IR would be feasible and rapid.
Not my speciality but surely the structure of urea would immediately tell a specialist the energies to look at. Best of luck and let me know how it goes!
Dear Nicolò M. Villa ! Potentiometric titration, liquid chromatography, and organic carbon analysis are suitable for urea analysis. Carbamide is very similar to amino acids, so it can be determined by chromatography on sulfocationite.I prefer potentiometric titration, it's fast and reliable. It is necessary to conduct it with alkali, then add an additive of urea suspension and titrate again.
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