Rationale: Helium (He) and energy shortages have dramatically increased prices and reduced their availability of these commodities. The use of three combustion reactions per acquisition of carbon and nitrogen isotope ratios saved 50% He and energy used in elemental analysis/isotope ratio mass spectrometry (EA/IRMS). This approach should be tested for sulfur isotope analyses. Mathods: A method was developed to measure sulfur isotope ratios ( d 34S values) in the SO 2 produced from three sequential combustion reactions in a single EA/IRMS acquisition. The combustion cycles involved capsules of the same or different materials. Two other developments are presented: a system for simultaneous extraction of chromium-reducible sulfur from four sediments or rock samples and the connections between the SO 2 reference gas and nitrogen cylinders for purging residual gases at the end of the EA/IRMS sequences. Results: The 3×EA/IRMS- d 34S method was validated with replicate analyses of international reference materials and laboratory standards with a wide range of mineralogical compositions and d 34S values. It was used for d 34S measurements of CRS-pyrites from Archean black shales and Swiss lake sediments. The accuracy and precision of the 3×EA/IRMS values were essentially matched those obtained by conventional EA/IRMS, with good agreement between the mean ± SD values and the recommended values and their Conclusions: Compared with the conventional EA/IRMS method. the proposed method provides accurate and precise sulfur isotope compositions of sulfate and sulfide samples while saving approximately 50% of the He, energy, SO 2 reference gas, O 2, and analysis time and cost. Notably, 3×EA/IRMS provided two d 34S values unaffected by potential memory effects.

RATIONALE: Helium (He) is used in cutting-edge research in industry and science as a carrier and/or ionization gas. The global He shortages have dramatically increased its prices and reduced its availability, to what comes together the current energy crisis. A strategy is proposed to save He and energy in elemental analysis/isotope ratio mass spectrometry (EA/IRMS). METHODS: A method for analysis of carbon and nitrogen isotope composition (δ13C and δ15N values) is proposed using two or three sequential combustion reactions in a single EA/IRMS acquisition. The methods (hereafter called 2×EA/IRMS and 3×EA/IRMS) use the time needed for the peak center and reference gas (CO2 or N2) pulses to measure δ13C or δ15N in two or three capsules with samples or standards. The combustion cycles can be replicate analyses of the same or different material. RESULTS: The methods were validated with replicate analysis of C and N in RMs and laboratory standards of a broad range of biological and geological matrices, δ13C and δ15N values, and C/N molar ratios. The accuracy and precision of the 2×EA/IRMS and 3×EA/IRMS values were15 essentially the same, with good agreement between the mean ± 1 SD values from RMs and standard analyses and the recommended or accepted values and their uncertainties. CONCLUSIONS: The proposed methods save He, save energy, save reference gases (CO2, N2), and O2, while reducing the analysis and instrumental times by ca. 50 %.