Compound-Specific Chlorine Isotope Analysis: A Comparison of Gas Chromatography/Isotope Ratio Mass Spectrometry and Gas Chromatography/Quadrupole Mass Spectrometry Methods in an Interlaboratory Study

• Published in: Analytical chemistry (Washington) Vol. 83; no. 20; pp. 7624 - 7634
• Main Authors: Bernstein, Anat, Shouakar-Stash, Orfan, Ebert, Karin, Laskov, Christine, Hunkeler, Daniel, Jeannottat, Simon, Sakaguchi-Söder, Kaori, Laaks, Jens, Jochmann, Maik A, Cretnik, Stefan, Jager, Johannes, Haderlein, Stefan B, Schmidt, Torsten C, Aravena, Ramon, Elsner, Martin
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.10.2011
• Subjects: Analytical chemistry; Applied sciences; Calibration; Chemistry; Chlorine; Chlorine - analysis; Chlorine - standards; Chromatographic methods and physical methods associated with chromatography; Chromatography; Comparative analysis; Environmental Pollutants - analysis; Exact sciences and technology; Gas chromatographic methods; Gas Chromatography-Mass Spectrometry - instrumentation; Gas Chromatography-Mass Spectrometry - standards; General, instrumentation; Global environmental pollution; Isotope Labeling; Isotopes; Isotopes - analysis; Isotopes - standards; Mass spectrometry; Pollution; Spectrometric and optical methods; Trichloroethylene - analysis; Performance evaluation; Trichloroethylene; Instrumentation; Isotopic composition; Standard; Round robin test; Laboratory; Calibration standards; Implementation; Quadrupole spectrometer; Chlorine compounds; Chlorides; Chlorocarbon; Flow injection; Chlorine; Sample; Use; Calibration; Gas chromatography; Pollutant; Environment; Application; Continuous flow method; Mass spectrometry; Comparative study
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac200516c

Chlorine isotope analysis of chlorinated hydrocarbons like trichloroethylene (TCE) is of emerging demand because these species are important environmental pollutants. Continuous flow analysis of noncombusted TCE molecules, either by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) or by GC/quadrupole mass spectrometry (GC/qMS), was recently brought forward as innovative analytical solution. Despite early implementations, a benchmark for routine applications has been missing. This study systematically compared the performance of GC/qMS versus GC/IRMS in six laboratories involving eight different instruments (GC/IRMS, Isoprime and Thermo MAT-253; GC/qMS, Agilent 5973N, two Agilent 5975C, two Thermo DSQII, and one Thermo DSQI). Calibrations of 37Cl/35Cl instrument data against the international SMOC scale (Standard Mean Ocean Chloride) deviated between instruments and over time. Therefore, at least two calibration standards are required to obtain true differences between samples. Amount dependency of δ37Cl was pronounced for some instruments, but could be eliminated by corrections, or by adjusting amplitudes of standards and samples. Precision decreased in the order GC/IRMS (1σ ≈ 0.1‰), to GC/qMS (1σ ≈ 0.2–0.5‰ for Agilent GC/qMS and 1σ ≈ 0.2–0.9‰ for Thermo GC/qMS). Nonetheless, δ37Cl values between laboratories showed good agreement when the same external standards were used. These results lend confidence to the methods and may serve as a benchmark for future applications.