Measurement of very small heavy nitrogen content

The accurate measurement of N-15 content in the samples of very small amount may be one fundamental way to develop N-15 tracer research. The measurement of very small amount of heavy nitrogen is required for the research on the nitrogen cycle in ocean, the measurement of nitrogen metabolism activity in soil and the measurement of activity in microscopic structure units. At present, the author performs the development of N-15 tracer method for the samples of very small amount. As the main measuring instrument, a mass analyzer for the precise measurement of isotopic ratio developed in the field of geochemistry, Hitachi RMU-6R type, has been used. This method requires somewhat more samples than light emission spectroscopic analysis, but the accuracy of N-15 measurement is better, accordingly, very small heavy nitrogen content can be measured by isotope dilution method. The sample intake system, analyzer and sensor of a mass analyzer for the precise measurement of N-15/N-14 ratio, N2 gasifying of granular organic substance, the measurement of heavy nitrogen content in NO2- and NO3-, and the measurement of denitrifying activity are described. (Kako, I.)