Precise Isotopic Measurements of Nitrogen at the Sub-Nanomole Level

Naoto TAKAHATA, Yoshiro NISHIO, Naohiro YOSHIDA, Yuji SANO
1998 Analytical Sciences  
Although nitrogen constitutes the major portion of the Earth's atmosphere, its degassing from the mantle and its circulation in the mantle are not well known. The reason is that because of a <1 nmol/g-N concentration, the nitrogen isotope ratios contained in mantle-derived materials, such as mid-ocean-ridge basalt glasses and diamonds, have been difficult to measure precisely using conventional dynamic mass spectrometers. Recently, Wright et al. 1 established a technique that enabled nitrogen
more » ... enabled nitrogen isotopic ratios on sub-nanomole level samples to be precisely measured by using a high-vacuum line used for gas extraction and purification, and a modified noble gas mass spectrometer. Subsequently, studies of isotopic sub-nanomole quantities of nitrogen in terrestrial samples by a similar measurement technique have been reported. 2,3 In order to discuss the origin of nitrogen, noble gas data (especially argon isotopes) are particularly useful. 4 Therefore, we have developed a system that enables the measurement of multiple elements simultaneously, without compromising the precision of the nitrogen isotopes. In this paper we give an outline of the system, and its performance by using the results of some basic experiments, and then measurements of nitrogen isotopes in reference mid-ocean ridge basalt glasses (which are already reported 2 ) in order to evaluate the usefulness of the new system.
doi:10.2116/analsci.14.485 fatcat:qoscthq46vdgtghhx6keqovcgu