Measurement of Sulfur Isotopic Composition by Sector Field Inductively Coupled Plasma Mass Spectrometry

A precise method was developed for the determination of sulfur isotopic composition by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) under medium resolution mode (m/Delta m = 4000). To get the best accurate and precise S-34/S-32 ratio, multiple parameters were optimized and evaluated systematically, including the ion source, ion optical system, data acquisition parameters (i. e. scan time, scan numbers and integration window) and the effect of sulfur concentration. The instrumental mass discrimination was corrected using standard-sample bracketing. The delta(34) SV-CDT of sulfur isotopic reference materials GBW04414 and GBW04415 was measured in different days, the measurement values were -0. 01 parts per thousand +/- 0. 31 parts per thousand and 22. 15 parts per thousand +/- 0. 42 parts per thousand , respectively. The results showed that this method had a high accuracy (error <+/- 0. 06 parts per thousand ) and good precision (repeatability <+/- 0. 5 parts per thousand, n = 10) in the determination of sulfur isotopic composition. Meanwhile, the proposed procedure was adopted to determine sulfur isotopic composition in some natural water samples (bottled mineral water, rain water and river water), the measurement precision was +/- 0. 19 parts per thousand to +/- 0. 58 parts per thousand, similar to that of the isotopic reference materials. The proposed method was suitable for the determining the sulfur isotopic composition of natural water samples precisely.