Simultaneous delta15N, delta13C and delta34S measurements of low-biomass samples using a technically advanced high sensitivity elemental analyzer connected to an isotope ratio mass spectrometer.
Conventional simultaneous CNS stable isotope abundance measurements of solid samples usually require high sample amounts, up to 1 mg carbon, to achieve exact analytical results. This rarely used application is often impaired by high C:S element ratios when organic samples are analyzed and problems such as incomplete conversion into sulphur dioxide occur during analysis. We introduce, as a technical innovation, a high sensitivity elemental analyzer coupled to a conventional isotope ratio mass spectrometer, with which CNS-stable isotope ratios can be determined simultaneously in samples with low carbon content (<40 microg C corresponding to approximately 100 microg dry weight). The system includes downsized reactors, a temperature program-controlled gas chromatography (GC) column and a cryogenic trap to collect small amounts of sulphur dioxide. This modified application allows for highly sensitive measurements in a fully automated operation with standard deviations better than +/-0.47 per thousand for delta15N and delta34S and +/-0.12 per thousand for delta13C (n = 127). Samples collected from one sampling site in a Baltic fjord within a short time period were measured with the new system to get a first impression of triple stable isotope signatures. The results confirm the potential of using delta34S as a stable isotope tracer in combination with delta15N and delta13C measurements to improve discrimination of food sources in aquatic food webs.
Hansen
T
T
Leibniz-Institute for Marine Sciences at Kiel University, Düsternbrooker Weg 20, 24105 Kiel, Germany. thansen@ifm-geomar.de
Burmeister
A
A
Sommer
U
U
D000818:Animals; D018533:Biomass; D002247:Carbon Isotopes / Q000032:analysis*; D004867:Equipment Design; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation* / Q000379:methods*; D007448:Invertebrates / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000032:analysis*; D015203:Reproducibility of Results; D012623:Seawater / Q000737:chemistry; D012680:Sensitivity and Specificity; D013460:Sulfur Isotopes / Q000032:analysis*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D013460:Sulfur Isotopes