Safe, accurate, and precise sulfur isotope analyses of arsenides, sulfarsenides, and arsenic and mercury sulfides by conversion to barium sulfate before EA/IRMS

Abstract

The stable isotope ratios of sulfur (δ34S relative to Vienna Cañon Diablo Troilite) in sulfates and sulfides determined by elemental analysis and isotope ratio mass spectrometry (EA/IRMS) have been proven to be a remarkable tool for studies of the (bio)geochemical sulfur cycles in modern and ancient environments. However, the use of EA/IRMS to measure δ34S in arsenides and sulfarsenides may not be straightforward. This difficulty can lead to potential health and environmental hazards in the workplace and analytical problems such as instrument contamination, memory effects, and a non-matrix-matched standardization of δ34S measurements with suitable reference materials. To overcome these practical and analytical challenges, we developed a procedure for sulfur isotope analysis of arsenides, which can also be safely used for EA/IRMS analysis of arsenic sulfides (i.e., realgar, orpiment, arsenopyrite, and arsenian pyrite), and mercury sulfides (cinnabar). The sulfur dioxide produced from off-line EA combustion was trapped in an aqueous barium chloride solution in a leak-free system and precipitated as barium sulfate after quantitative oxidation of hydrogen sulfite by hydrogen peroxide. The derived barium sulfate was analyzed by conventional EA/IRMS, which bracketed the δ34S values of the samples with three international sulfate reference materials. The protocol (BaSO4-EA/IRMS) was validated by analyses of reference materials and laboratory standards of sulfate and sulfides and achieved accuracy and precision comparable with those of direct EA/IRMS. The δ34S values determined by BaSO4-EA/IRMS in sulfides (arsenopyrite, arsenic, and mercury sulfides) samples from different origins were comparable to those obtained by EA/IRMS, and no sulfur isotope fractionations were introduced during sample preparation. We report the first sulfur isotope data of arsenides obtained by BaSO4-EA/IRMS. Graphical abstract

Identification and quantification of cucurbitacin in watermelon frost using molecular networking integrated with ultra‐high‐performance liquid chromatography‐tandem mass spectrometry

“…The accuracy of the method was defined as the difference between an accepted true value and the result obtained in an analytical run [41]. The difference reflects laboratory error and systematic error in the method.…”

Trace Element and Sulfur Isotope Signatures of Volcanogenic Massive Sulfide (VMS) Mineralization: A Case Study from the Sunnhordland Area in SW Norway

“…Sulfur isotope analyses were carried out at the University of Lausanne, Switzerland, using elemental analysis and isotope ratio mass spectrometry (EA/IRMS). The EA/IRMS system consisted of a Carlo Erba 1108 elemental analyzer coupled with a continuous helium flow interface to a Thermo Fisher Delta V isotope ratio mass spectrometer [35]. The samples were combusted at 1030 • C in a single oxidation-reduction quartz tube filled with oxidizing (tungsten trioxide) and reducing (elemental copper) agents.…”

“…The measured values of sulfur isotopes are given in the δ-notation and relative to the Vienna Cañon Diablo Troilite (VCDT) standard. The laboratory assured that the reproducibility with replicate analysis with given standards (natural pyrite -6.72 ‰, synthetic mercury sulfide, +15.82 ‰, barium sulfate, +12.73 ‰ δ 34 S; [35]) is better than 0.2‰. 3A).…”

Procedures from samples to sulfur isotopic data: A review

“…298 The pyrolysis part of EA is used to combust the sample in a He flow, trapped in an H 2 O 2 trap, and collected as BaSO 4 . 299…”

“…When samples with harmful or toxic parts like arsenopyrite are challenged, they can form gas‐phase arsenic oxides (As 2 , HgS, and Hg) which are hazardous for the environment and the people who work in the laboratory and operate instruments 298 . The pyrolysis part of EA is used to combust the sample in a He flow, trapped in an H 2 O 2 trap, and collected as BaSO 4 299 …”