(vi) Recently, Hilkert et al. showed that stable isotope ratio analysis (SIA) of nitrate is possible using ESI Orbitrap. Nitrogen (δ 15 NAIR), oxygen δ 18 OVSMOW, and δ 17 OVSMOW isotope ratios can be measured simultaneously with a long-term precision of ≤ 0.4 ‰ for reference material and purified nitrate samples. In order to develop an LC-IRMS method for the measurement of nitrogen isotope ratios from organic compounds, one problem that had to be solved first was whether nitrogen species formed during oxidation of organic compounds with peroxydisulfate that can be converted into a measurable gas form such as N2O, NO or N2. Our subsequent objective was therefore to develop a method for measurement of nitrogen isotope signatures of nitrate through an online conversion into gaseous nitrogen oxide species (NxOy) and subsequent reduction to elemental nitrogen, while maintaining the capability for low-volume injections of samples. Furthermore, the goal was to achieve a chromatographic separation of nitrate from the injection peak and potentially nitrite. Here, we present the initial findings of standard sample measurements conducted with the modified interface and discuss the method's limitations and possible options for further improvement and future applications. Additionally, we had the opportunity to test our system with samples from an enrichment experiment conducted in a small sandy river.