Comparison of Gas and Liquid Chromatography (GC, LC) coupled with Isotope Ratio Mass Spectrometry (IRMS): a case study on rice amino acids

Compound-Specific Isotope Analysis (CSIA) of amino acids (AAs) is increasingly applied in food authentication and environmental studies, where precise and accurate δ13C measurements are essential. This study systematically compares the performance of Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS) and Liquid Chromatography coupled to Isotope Ratio Mass Spectrometry (LC-co-IRMS) for δ13C analysis of essential and non-essential AAs. The GC-C-IRMS showed high analytical precision, with standard deviations typically below 0.5 ‰ for standard AAs and 0.8 ‰ for rice samples, in close agreement with EA-IRMS reference values. The LC-co-IRMS, while generally reliable, exhibited higher variability, with deviations up to 1.6 ‰ for standard AAs and 1.9 ‰ for samples. The GC-C-IRMS also provided better chromatographic resolution, shorter run times, and broader amino acid coverage but involved complex workflows, including derivatization and the use of hazardous reagents. In contrast, LC-co-IRMS offered a simpler, safer protocol with fewer correction steps, though with longer analysis times, reduced throughput, and higher water consumption. Despite these trade-offs, both methods yielded comparable δ13C values overall, with some differences for specific AAs. This study finds GC-C-IRMS as suitable for high-precision, high-throughput applications, while LC-co-IRMS is more appropriate for simplified, sustainable workflows, with method selection depending on research purposes and operational priorities