Measurement of ³⁴S/³²S Ratios of NBS 120c and BCR 32 Phosphorites Using Purge and Trap EA‐IRMS Technology

Abstract

Measurements of sulfur stable isotope ratios (34S/32S) have suffered from technical difficulties in analysing 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 a high‐precision method of sulfur isotope determination using a new type of elemental analyser based on ‘purge and trap’ technology. This new technique demonstrates the high quality of 34S/32S measurements for samples with S concentrations lower than 1% m/m. 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: BCR 32 and NBS 120c. δ34SCDT values of, respectively, 18.2‰ (1s = 0.3; n = 23) and 18.3‰ (1s = 0.4; n = 20) are proposed for these. Calibration of both phosphorites with international reference materials led to calculation of a mean standard error close to 0.4‰. The demonstration of a capability to reliably measure S isotope ratios in low‐S phosphate minerals or rocks opens up new fields of palaeoenvironmental reconstructions.

High‐precision 34S/32S measurements in vertebrate bioapatites using purge‐and‐trap elemental analyser/isotope ratio mass spectrometry technology

“…The average δ 34 S V‐CDT value measured for BCR32 obtained during these four batches of isotopic measurements is +18.4‰ (1 σ = 0.5; n = 18) (Table ). This value is in agreement with that published by Fourel et al who measured an average δ 34 S V‐CDT value of +18.2‰ (1 σ = 0.3‰; n = 23) for BCR32.…”

“…The VarioPYROcube elemental analyser is equipped with a ‘purge‐and‐trap’ separation system, recently made available for isotope ratio mass spectrometry (IRMS) instruments, allowing CO, CO 2 and SO 2 gases to be trapped before being desorbed at appropriate timing. This system has been fully investigated in pyrolysis mode by Sieper et al and Fourel et al as well as in combustion mode by Fourel et al We emphasise the capacity of the ‘purge‐and‐trap’ technology to generate sharp and symmetrical chromatographic peaks and to minimise peak tailing compared with conventional packed gas chromatography (GC) column‐based chromatographic system. Moreover, the desorption timings for trapped species are user‐defined which improves the quality of the analyses for samples with high C/S ratios.…”

“…However, sulfate is present in very low concentration (<1 wt%), thus hitherto preventing its isotopic analysis due to technical difficulties. Fourel et al demonstrated the capacity of the VarioPYROcube elemental analyser system interfaced in continuous‐flow mode with an Isoprime isotope ratio mass spectrometer to measure with high precision the δ 34 S V‐CDT values of two phosphorites (a sedimentary rock compositionally close to apatite) with low‐S concentrations (< 1 wt%): BCR32 and NBS‐120c, for which they published δ 34 S V‐CDT values of, respectively, +18.2‰ (1σ = 0.3‰; n = 23) and +18.3‰ (1σ = 0.4‰; n = 20).…”

Sulfur isotope analysis by MC-ICP-MS and application to small medical samples

“…Continuous ow devices using a gas chromatograph with helium as the carrier, known as elemental analyzer-isotopic ratio mass spectrometers (EA-IRMS), have been developed, which are now considered a routine and commercially available technique. [3][4][5][6][7] Sample preparation is minimal, with no need for chemical separation. Precision for replicates of mineral isotopic standards measured is in the order of AE0.2& (2s), but requires the extraction of a few mg of elemental sulfur.…”

Atomic spectrometry update – a review of advances in environmental analysis

“…The N 2 passed straight through the trap assembly. Although the measurement of 32 S/ 34 S ratios in CRMs BCR 32 (Moroccan phosphate) and NIST 120c (Florida phosphate rock) containing 0.4-0.7% S m/m were accurate, 485 relatively large aliquots (5-8 mg) had to be analysed to ensure satisfactory precision (0.4&, 1SE). These materials were proposed as potential isotope RMs for future studies of S isotopes in biogenic apatites.…”