Stable Nitrogen Isotope Analysis of Amino Acids by Orbitrap Mass Spectrometry: Application for Extraterrestrial Samples

Abstract

Background Obtaining isotopic data on soluble organic compounds, such as amino acids, in extraterrestrial samples is crucial for understanding their origins, prebiotic chemistry, and potential contamination. Conventional GC-IRMS requires grams of material to measure isotopic compositions, limiting the analysis of low-concentration organics in meteorites and other astromaterials. We present an Orbitrap-based method optimized for nitrogen isotopic analysis of amino acids. Results This method determines δ¹⁵N values for picomole quantities (< 150 pmol) with 3‰–8‰ precision and accuracy within 2‰ compared with elemental analysis. Our approach was validated using amino acid enantiomer standards and a CM2 Murchison meteorite sample. The Murchison results demonstrate that comparable precision can be achieved on analytes extracted from a total sample size representing less than 7% of the mass previously required for CSIA analysis of the same meteorite. Significance These results highlight the potential of Orbitrap mass spectrometry for δ¹⁵N measurements with less material and lower analyte concentrations. This technique improves our ability to trace the origins and synthetic pathways of amino acids, providing valuable insights into prebiotic chemistry and possible abiotic mechanisms for organic compound formation in primitive solar system materials. Nitrogen isotopes serve as a powerful tool for distinguishing biological from non-biological sources, aiding in the identification of contamination in meteoritic samples and improving the reliability of analyses involving rare extraterrestrial materials.