[Advances in the process to standardize methodologies of nitrogen analysis in fertilizers]
1995
In order to unify the methodologies for Nitrogen analysis in fertilizers, 5 analytical methods for Ammonium-N, 6 for Ammonium + Nitrate-N and 10 for Total-N were compared. A common sample was analyzed for several participating laboratories and after that a unique methodology was, defined. The advantages and disadvantages of each analytical methodology were discussed. To the present the approved methods are: 1.- Method for the analysis of Ammonium-N, based on the transformation of ammonium salts into ammonia with sodium hydroxide. This free ammonia is then distilled and received in a boric acid solution. The amount of nitrogen is obtained for titration with a strong, mineral acid in the presence of a mixture of indicator. 2.- Method for the analysis of Nitrate + Ammonium-N based on nitrate reduction into ammonia by using metal alloys which produce hydrogen under alkaline conditions. This ammonia, together with the Ammonium-N of the sample is then distilled and received in the same manner as described in method I.
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