Sourcing organic compounds based on natural isotopic variations measured by high precision isotope ratio mass spectrometry

High precision isotope ratio mass spectrometry (IRMS) enables the detection of variability in isotope abundance due to natural processes. IRMS instruments are highly specialized for the analysis of C-13/C-12, H-2/H-1, N-15/N-14, O-18/O-16, and S-34/S-32 via analysis gases CO2, H-2, N-2, and SO2 using a tight electron impact ion source, high transmission magnetic sector, and multiple collectors, delivering relative standard deviations of less than 0.01%. Recent developments exploiting continuous flow inlets have improved sample throughput and permitted a wide range of samples to be analyzed by highly automated systems. Isotope ratio analysis at the bulk mixture and compound-specific levels is now routine, and strategies for intramolecular analysis are on the horizon. Studies over 50 years have shown that isotopic fractionation due to physiological processes, specifically CO2 transport processes within plants and photosynthesis, leads to variation in isotope ratio in natural compounds. Different chemical processes leading to isotope fractionation operate in the generation of petroleum. IRMS analysis can, in many cases, distinguish petroleum derived from different geographical regions that are otherwise identical. In wines and juices, climate differences that depend on geographic location induce isotopic fractionation that can be detected by IRMS and are characteristic of region and even vintage. Intramolecular or chiral isotope analysis is able to detect the origin of flavor compounds such as vanillin. Use of illicit, endogenous drugs such as testosterone, can be detected by isotope ratio analysis when referenced against another endogenous steroid upstream or independent of the endogenous biosynthetic pathway. These and related applications show that natural isotopic structure is a powerful tool for determining the origin of organic compounds.