An Inexpensive Auto-injection Preprocessing System for N₂O by Isotope Ratio Mass Spectrometer to Measure δ¹⁵N and δ¹⁸O of Nitrate

Abstract

Nitrogen and oxygen isotope ratios (δ¹⁵N, δ¹⁸O) of nitrate have been measured by denitrifier method aiming to analyze N material flows and their sources (ocean, lake, river, and groundwater). The denitrifier method developed in 1990s allows us to measure both δ¹⁵N and δ¹⁸O of nitrate simultaneously employing small amounts (i.e. 30nmol). The instruments including online auto-injection of N₂O gas are still expensive(generally cost more than two hundred thousand US$). Here, we have developed a self-made auto-injection system of N₂O to IRMS connected to the interface(Conflo III). This self-made system is inexpensive(i.e. twenty thousand US$) and has equal precisions of δ¹⁵N and δ¹⁸O with the past systems.