The Stable Isotope Mass Spectrometry Facility is housed and staffed within the Soil and Water Science Department (SWSD). The instrumentation was purchased and is maintained as a collaborative research facility by the SWSD, and UF Departments of Geological Sciences and Botany. Samples from other UF Departments as well as other outside entities can be submitted to the facility and current pricing can be obtained by contacting Bill Pothier.

The centerpiece of the facility is a Thermo Finnigan MAT Delta Plus XL mass spectrometer designed to cover a mass range up to 70 amu to determine the stable isotope ratios of certain gaseous elements.Three peripherals are presently dedicated to the mass spectrometer for the purpose of converting the sample from a solid or liquid state to a gaseous state prior to introduction into the mass spectrometer:

• Elemental Analyzer (EA)- A Costech Instruments elemental analyzer system has been connected to the mass spectrometer for the purpose of flash combustion of soil and plant samples to produce N₂, CO₂, and H₂O. UHP Helium is used as a carrier gas to transport the gases produced during combustion thru a water trap to remove any water present in the gas stream prior to entering a GC column within the system where the N₂ and CO₂ are separated within the carrier gas before entering the mass spectrometer.

• Gas Chromatograph (GC)- A Hewlett Packard HP 6890 is utilized for carbon and nitrogen isotope analysis via Isotope-Ratio-Monitoring Gas Chromatography (irmGCMS). The irmGCMS technique involves on-line separation of compounds e.g. amino acids, FAMES, sterols and other hydrocarbons from mixtures. These compounds are separated by gas chromatography. The gas chromatography effluents are combusted and sent to the mass spectrometer continuously in a helium carrier stream.

• Gas Bench- A Thermo Finnigan GasBench III is utilized for multiple sample/standard comparison. The Gas Bench III is an on-line interface which allows automated ratio determination of small gas samples. The gas (CO₂) can be liberated from a liquid or solid phase into the headspace of the sample vial by different sample preparation methods, Used for DIC, carbonates or equilibration and in the near future nitrate via the microbial denitrifier method.