Determination of the δ34S of Total Sulfur in Solids: RSIL Lab Code 1800

Techniques and Methods 10-C4
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Abstract

The purpose of Reston Stable Isotope Laboratory Lab (RSIL) Code 1800 is to determine the δ(34S/32S), abbreviated as δ34S, of total sulfur in a solid sample. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total sulfur in a solid sample into SO2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines the relative difference in stable sulfur isotope-amount ratio (34S/32S) of the product SO2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in tin capsules and loaded into a Costech Zero-Blank Autosampler on the EA. Under computer control, samples are dropped into a heated tube reaction tube that combines both the oxidation and the reduction reactions. The combustion takes place in a He atmosphere that contains an excess of oxygen gas at the oxidation zone at the top of the reaction tube. Combustion products are transported by a He carrier through the reduction zone at the bottom of the reaction tube to remove excess oxygen and through a separate drying tube to remove any water. The gas-phase products, mainly CO2, N2, and SO2, are separated by a gas chromatograph (GC). The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Thermo-Finnigan ConFlo II interface, which also is used to inject SO2 reference gas and He for sample dilution. The IRMS is a Thermo-Finnigan DeltaPlus CF-IRMS. It has a universal triple collector with two wide cups and a narrow cup in the middle. It is capable of measuring mass/charge (m/z) 64 and 66 simultaneously. The ion beams from SO2 are as follows: m/z 64 = SO2 = 32S16O16O; and m/z 66 = SO2 = 34S16O16O primarily.
Publication type Report
Publication Subtype USGS Numbered Series
Title Determination of the δ34S of Total Sulfur in Solids: RSIL Lab Code 1800
Series title Techniques and Methods
Series number 10-C4
DOI 10.3133/tm10C4
Edition Version 1.2, August 2012 (Version 1.1 2007)
Year Published 2006
Language ENGLISH
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Reston Stable Isotope Laboratory
Description viii, 31 p.; ill.; Appendices
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