Detection of small traces of N-15(2) and N-14(2) by Faraday LMR spectroscopy of the corresponding isotopomers of nitric oxide

A Faraday LMR spectrometer for detection of low concentrations of N-15(2) in a gas phase sample is described. The nitrogen is transformed by a microwave discharge into nitric oxide NO. The latter is analyzed by recording both a (NO)-N-15 and a (NO)-N-14 Faraday LMR signal. The determination of the transformation rate from N-2 into NO is described. The method of measurement and the achieved sensitivity (similar to 0.1 ppm N-15(2) approximate to 4 nanomoles N-15(2)/liter gas) of the spectrometer are discussed. An application in pharmacology, where N-15 is used as a tracer for metabolism is indicated. First experiments with the exhalation of a rat show that the apparatus is useful to give a new quality of results.