Elemental Analyzer–Interface–Off-Axis Integrated Cavity Output Spectroscopy (EA-OA-ICOS): A Universal Coupling for Carbon Stable Isotope Analysis of Organic Materials

An innovative coupling between a custom-built elemental analyzer (EA) and an off-axis integrated cavity output spectroscopy (OA-ICOS) laser is introduced for δ¹³C analysis of solid organic samples, providing an efficient and eco-friendly alternative to conventional elemental analysis─isotope ratio mass spectrometry (EA-IRMS). This study demonstrates that δ¹³C can be efficiently measured after sample combustion, through a dedicated interface, with high accuracy (standard deviations δ¹³C ± 0.22‰, % C ± 0.24%). Using a thorough methodology, EA-ICOS analysis of international standards was compared to conventional EA-IRMS, giving similar mean values and standard deviations. The interface coupled to the OA-ICOS laser is universal and can be connected to various commercial EAs. In this study, two different EAs were tested, giving highly comparable results and demonstrating that this coupling is compatible with EAs commonly available in analytical laboratories.