title: Compound-Specific Sulfur Isotope Analysis of Petroleum Gases.
abstract: We describe a simple, sensitive, and robust method for sulfur isotope ratio (34S/32S) analysis of ppm-level organic sulfur compounds (OSCs) in the presence of percent-level H2S. The method uses a gas chromatograph (GC) coupled with a multicollector inductively coupled plasma mass spectrometer (MC-ICPMS). The GC, equipped with a gas inlet and a valve that transfers the H2S to a thermal conductivity detector (TCD), enables a precise heart cut and prevents the saturation of the MC-ICPMS. The sensitivity and accuracy of the method are better than 0.3‰ for OSCs at a concentration of 25 pmol or 1.4 ppm, and better than 0.5‰ for concentrations ≥0.7 ppm of OSCs. An order of magnitude increase in sensitivity, with no effect on accuracy, can be achieved if the loop volume (0.5 mL) is changed to 5 mL. High concentrations of methane (95% v/v) and/or H2S (20% v/v) had no effect (within 0.5‰) on the precision and accuracy of the gas sample containing 2 ppm of OSCs after heart cut. The applicability and robustness of this method are demonstrated on a gas sample (10% v/v H2S) that was produced by pyrolysis of sulfur-rich kerogen. The results show good precision and reveal sulfur isotope variability between individual OSCs that may represent key processes during formation and degradation of OSCs.
authors.affiliation: Earth Sciences Institute, Hebrew University , Jerusalem 91904, Israel.
authors.forename: Ward
authors.initials: W
authors.lastname: Said-Ahmad
authors.affiliation: Air Liquide, Delaware Research & Technology Center , Newark, Delaware 19702, United States.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Wong
authors.affiliation: Air Liquide, Delaware Research & Technology Center , Newark, Delaware 19702, United States.
authors.forename: Monaca
authors.initials: M
authors.lastname: Mcnall
authors.affiliation: Earth Sciences Institute, Hebrew University , Jerusalem 91904, Israel.
authors.forename: Lubna
authors.initials: L
authors.lastname: Shawar
authors.affiliation: Air Liquide, Delaware Research & Technology Center , Newark, Delaware 19702, United States.
authors.forename: Tracey
authors.initials: T
authors.lastname: Jacksier
authors.affiliation: Schlumberger , 1 Rue Henri Becquerel, Clamart, France 92140.
authors.forename: Courtney
authors.initials: C
authors.lastname: Turich
authors.affiliation: Schlumberger , 5599 San Felipe, Houston, Texas 77056, United States.
authors.forename: Artur
authors.initials: A
authors.lastname: Stankiewicz
authors.affiliation: Earth Sciences Institute, Hebrew University , Jerusalem 91904, Israel.
authors.forename: Alon
authors.identifier: 0000-0003-2872-1451
authors.initials: A
authors.lastname: Amrani