Online Sulfur-Isotope Determination Using an Elemental Analyzer Coupled to a Mass Spectrometer

Abstract

An on-line method for S-isotope analysis is described. Samples are combusted in an elemental analyzer. SO2 is separated from other combustion gases by gas chromatography, and the gases enter the ion source of the mass spectrometer through a split interface. Integrated peak areas for 32S02+ and 34SC>2+ are compared to the response for a standard gas sample to determine the S^S value. 534S values of samples analyzed using the on-line method correspond linearly with those achieved from the same sample prepared off-line, where Kiba reduction followed by oxidation of the sulfur to SO2 is carried out prior to S-isotope analysis against a known standard. With the described on-line method, the amount of sulfur necessary for S-isotope analysis is reduced to about 10 #tg of S per analysis. The time needed for on-line preparation and measurement is less than one-third of the off-line procedure.Stable sulfur-isotope analysis is often associated with many problems concerning sample preparation and mass spectrometric determination. The 34S/32S ratios are most commonly determined after SO2 has been generated out of natural materials. Sample preparation always requires several chemical transformation steps to finally produce SO2 out of the S-containing compounds. The standard preparation techniques used for most sulfur-bearing samples start with conversion of all sulfur to BaSO*, which is then reduced to H2S by one of the following three procedures: graphite reduction at 1000 °C,' reduction with tin(II)-strong phosphoric acid (Kiba's reagent) at 300 °C in a stream of nitrogen,2 or application of a HI-H3PO4-HCI reduction solution.3 The generated H2S is converted to Ag2S, which is finally oxidized to SO2. One major disadvantage of these methods is that they all need relatively large amounts of the original material to obtain sufficient sulfur as the numerous chemical processes require rather high amounts of sulfur (3-7 mg of S). Although

Oxygen and sulphur isotopes of gypsum from the Mogilno Salt Dome cap-rock (Central Poland)

“…The first was used to de ter mine the d 34 S value (cf. Giesemann et al, 1994); V 2 O 5 was added to the sul phate sam ples as a com bus tion aid. The val ues found are ex pressed in per mil, rel a tive to the Vi enna-Can yon Diablo Troilite stan dard (V-CDT); the an a lyt i cal pre ci sion is ±0.2‰.…”

Sulfur Isotopes as Indicators of Amended Bacterial Sulfate Reduction Processes Influencing Field Scale Uranium Bioremediation

“…Sulfur isotope samples were prepared at the University of California Berkeley (40) and sent to the University of Nevada at Reno Stable Isotope Laboratory for analysis. Sulfur isotope analyses were performed in helium continuous flow mode, using a Eurovector model 3028 elemental analyzer interfaced to a Micromass IsoPrime isotope ratio mass spectrometer following established methods (42,43), with a precision of (0.15‰ (1σ). V2O5 was added to BaSO4 samples as a (Figure 2g), and uranium averaged of 1.0 mM and ranged from 0.7 to 1.5 mM (Figure 2h).…”

Isotopic composition of sulfur in size‐resolved marine aerosols above the Atlantic Ocean

“…Sulfate precipitated in the capsule as the solution dried out. The tin foil was then wrapped up and compacted, ready to be introduced in the elemental analyzer (Carlo Erba NC-2500) for on-line CF-IRMS analysis [Giesemann et al, 1994;Parris et al, 1999]. Tin encapsulated samples were combusted in a flash of oxygen at temperature reaching locally 1800øC.…”