Interlaboratory Comparison of Elemental Analysis and Gas Chromatography Combustion Isotope Ratio Mass Spectrometry (GC-C-IRMS) - Part I: Delta13C Measurements of Selected Compounds for the Development of an Isotopic Grob-test

Abstract

This study was directed towards investigating suitable compounds to be used as stable isotope reference materials for GC-C-IRMS calibration. Several compounds were selected from those used in the GROB-test mixture. Oxygen- and nitrogen-containing substances were added to these compounds to allow the mixture to be used as a possible multi-isotopic calibration tool for 2H/1H, 13C/12C, 15N/14N and 18O/16O ratio determinations. In this paper we present the results of delta13C measurements performed by the consortium of the five laboratories taking part in this intercalibration exercise. All the compounds were individually assessed for homogeneity, short-term stability and long-term stability by means of EA-IRMS, as required by the BCR Guide for Production of Certified Reference Materials. The results were compared then with the GC-C-IRMS measurements using both polar and non-polar columns and the final mixture of selected compounds underwent a further certification exercise assessing limits of accuracy and reproducibility under specified GC-C-IRMS conditions.