Rapid micro-determination of nitrogen in biological materials by the iodic acid-strong phosphoric acid decomposition method

To develop a rapid and convenient means for the determination of nitrogen in animal and plant materials, the iodic acid strong phosphoric acid decomposition method was employed for the purpose, the method had been devised in our laboratory for nitrogen, carbon and sulfur in organic compounds. Nitrogen in biological materials are conventionally estimated by the Kjeldahl method in the routine works, but the procedure including the decomposition of sample, the distillation of ammonia and the standardization of acid or alkali solution is rather tedious and time consuming especially when the number of samples is small. In the proposed method, on the contrary, the analysis can be completed within about twenty minutes only by a simple apparatus and by reading the volume of the gas (nitrogen for the most part) evolved. The results obtained by the authors agreed well with those by the Kjeldahl method for various samples of animal and plant materials such as soybean powder, fish meal, ground tea and wheat flour. Several discussions were presented on the behavior of five- and six-membered nitrogen compound which might exist in the natural substances.