A novel high‐temperature combustion based system for stable isotope analysis of dissolved organic carbon in aqueous samples. I: development and validation

Abstract

The novel HTC system coupled to an isotope ratio mass spectrometer resulted in significantly improved sensitivity. The system is suitable for salt-containing liquids and compounds that are resistant to oxidation, and it offers a large concentration range. A second paper (which follows this one in this issue) will present a more comprehensive assessment of the analytical performance with a broad set of solutions and real samples. This highly efficient TOC stable isotopic analyzer will probably open up new possibilities in biogeochemical carbon cycle research.

A novel tool for stable nitrogen isotope analysis in aqueous samples

“…The focus of this work was the development and testing of a novel system for HTC TOC/IRMS δ 15 N BSIA. A HTC‐based system rather than a wet chemical oxidation (WCO)‐based system to enable measurement of δ 15 N–values was selected based on previous findings . In addition, previous findings with a HTC‐based HPLC/IRMS interface, such as the need for a reduction oven and an additional mass flow controller, were implemented .…”

“…Consequently, suitable and accurate online methods for stable isotope analysis (SIA) of carbon and nitrogen in aqueous samples such as soil extracts are required . Over the last decade, there has been much effort directed towards establishing the routine measurements of δ 13 C values of dissolved organic carbon (DOC) through the coupling of total organic carbon (TOC) analyzers with isotope ratio mass spectrometry (TOC/IRMS) . The natural abundance bulk stable isotope analysis (BSIA) of the δ 15 N values of total nitrogen bound (TN b ) still has large limitations and these values cannot be measured simultaneously with δ 13 C values directly from an aqueous sample.…”

A novel high‐temperature combustion interface for compound‐specific stable isotope analysis of carbon and nitrogen via high‐performance liquid chromatography/isotope ratio mass spectrometry

“…In a previously reported HTC interface, oxygen was used as carrier and reaction gas . Due to the need of a reduction tube (conversion of NO into N 2 ), the oxygen carrier gas had to be replaced by helium.…”

“…Furthermore, WCO‐based systems for δ 13 C CSIA suffer from the same problem as is common in BSIA, i.e. the risk of isotopic fractionation due to incomplete oxidation …”

“…In view of the limitations of the existing instrumental approaches and taking into account the positive experience with the HTC TOC analyzer, we have developed a novel high‐temperature combustion (HTC)‐based HPLC/IRMS system for δ 13 C and δ 15 N CSIA. In this manuscript, we present the technical details of the system and results of a first proof of principle study.…”