Application of EA-IRMS and a LA-GHG-IRMS approach for high-resolution carbon and oxygen isotope analysis in woody biomass

Isotopic analyses of carbon (δ¹³C) and oxygen (δ¹⁸O) are widely applied in biogeosciences to investigate biogeochemical cycles, ecosystem functioning, and environmental dynamics. Elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) represents one of the most widely applied systems for bulk samples. The laser ablation-IRMS (LA-IRMS) provides the possibility to resolve spatial and temporal variability at high resolution, but also presents some limitations due to gas handling, signal stability, and analytical comparability with conventional approaches.

For this study, we present a methodological comparison between δ¹³C and δ¹⁸O measurements obtained using EA-IRMS and an improved LA-IRMS configuration. In our configuration, the LA is coupled with the IRMS through a greenhouse gas (GHG) analyzer specifically modified to concentrate, purify, and stabilize CO₂ and CO generated during ablation to improve the gas signal for isotope measurements.

Analyses were conducted on hazelnut (Corylus avellana L.) wood slices for EA-IRMS and tree-ring increments for LA-GHG-IRMS. The comparison between the two methods showed main differences related to sampling resolution and analytical configuration. The LA-GHG-IRMS system provided high-resolution isotope measurements that allowed investigations of intra-seasonal patterns.

The application of the LA-GHG-IRMS system extends the analytical utility of laser-based stable isotope measurements in biogeosciences, providing new opportunities for high-resolution studies of ecological processes in terrestrial ecosystems.