Wed, 02 Nov|
ChromSA online lecture by Adriaan Marais
Compound-specific isotope ratio analysis using low-resolution single quadrupole GC-EI-MS: Analytical potential and pitfalls for chlorinated compounds.
Time & Location
02 Nov 2022, 15:00 – 17:00
About the event
Abstract: Stable isotope ratio mass spectrometry (IRMS) allows the accurate measurement of small differences in the abundances of isotopes such as 2H/1H, 13C/12C, 15N/14N, and 18O/16O, in a wide variety of sample types applicable to numerous disciplines e.g. geochemistry, environmental science, food science, and forensic science. The underlying principle is the fractionation of light (e.g. 12C) versus heavy isotopes (e.g. 13C) occurring during any natural or synthetic chemistry process. The differential incorporation of light and heavy isotopes in a chemical structure, as directly related to the starting material and specific process that originates that structure, thus leads to a specific subset of heavy/light isotope ratios that may impart a degree of uniqueness to a compound. Simply put, a chemical compound originating under specific conditions may display isotope ratios that are unique and dissimilar to the same compound originating under differing conditions. The measured isotope ratios are often expressed as the amount of enrichment of the heavier isotope compared to some comparative or standardised value. Chlorine occurs as two stable isotopes with a known natural relative abundance, 35Cl (approx. 75.8%) and 37Cl (approx. 24.2%). In contrast to other compound specific isotope analyses (CSIA) such as 13C/12C, chlorine has only recently been used to identify and quantify shifts in the δ37Cl of compounds, most prominently in environmental chemistry applications. CSIA-Cl presents an attractive option for organochlorine isotope analyses as routine gas chromatography (GC) instrumentation coupled to either low-resolution quadrupole mass spectrometry (qMS) or high-resolution mass spectrometry (HRMS) platforms can be utilised, as opposed to dedicated IRMS instruments. However, some intrinsic limitations of GC-EI-qMS need to be addressed before and during method development for successful measurements.
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