Abstract
Measurements of sulfur stable isotope ratios (34S/32S) have suffered in the past from technical difficulties in analyzing low-S materials reducing their use despite their undeniable scientific interest. The measurement of 34S/32S ratios is a powerful tool for deciphering problems such as determining the sources of environmental pollutants, to detect adulteration, tracking the evolution of the redox state of the oceans, and quantifying the role of the bacterial activity in sulfide minerals genesis. We have used an innovative high–precision, easy and rapid method of simultaneous analysis of carbon (13C/12C), nitrogen (15N/14N) and sulfur (34S/32S) isotope ratios as well as elemental concentrations using a new combination of elemental analyzer and isotopic ratio mass spectrometer. This new technique provides multiple isotopic signatures on smaller sample aliquots with high precisions especially for sulfur determinations. The technique described here is Isotopic Ratio Mass Spectrometry (IRMS) on line in continuous flow mode with an Elemental Analyzer (EA) based on “purge and trap” technology rather than conventional packed-GC gas separation. Emphasis is put on the efficiency of the system to reliably combust sulfur–bearing compounds of both organic and inorganic origin with high conversion yields. This new technique demonstrates the high quality of 34S/32S measurements for samples with S concentrations lower than 1 wt%. International calibrated references of diverse sulfur-bearing materials were used to calibrate two low (<1%) S -bearing phosphorites used as compositional reference material for future use as isotopic references: BCR32 and NBS120c. High quality of 34S/32S determinations is illustrated using various international reference materials. Working calibrated material has been selected and characterized for all three isotopic signatures as well in order to fully use the capacities of the system in future work. The possibilities of such a system to reliably measure S isotopes as well as N and C within the same aliquot of sample opens up new fields of investigation in many domains where multi-isotopic approaches are required.
Highlights
Sulfur isotopic analyses have suffered for a long time from their high degree of technical difficulties compared to carbon or nitrogen isotopic analyses 1
This demonstrates the capacity of the system to combust S-bearing samples into SO2 as well as the linearity of such combustion yields, which is an important parameter when trying to tackle samples with low S concentrations
The results reported in this study demonstrate the capacities of the PyroCube Elemental Analyzer coupled online with an Isotopic Ratio Mass Spectrometry (IRMS) instrument to determine simultaneously G13C, G15N and G34S values from the same sample aliquot with high–levels of precision for the three isotopic systems (±0.2‰; ±0.2‰; ±0.4‰; respectively)
Summary
Sulfur isotopic analyses have suffered for a long time from their high degree of technical difficulties compared to carbon or nitrogen isotopic analyses 1. Beyond those technical difficulties, the interest of sulfur is that it occurs under different oxidation states (-2 to +6) and it is present under various organic and inorganic species. Sulfur at natural abundance shows four isotopic species 32S (95.02%), 33S (0.75%), 34S (4.21%) and 36S (0.02%) Due to those technical difficulties most studies concentrate on 34S/32S isotopic fractionation. The technique we present here is significantly different and uses “purge and trap” technology to separate the analyte gases which first improves significantly their separation and allows the simultaneous determination of both G15N, G13C and G34S isotopic signatures as well as N, C and S elemental concentrations within 12 minutes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
