Gas Bench Principles
The Gas Bench is a configurable device that accommodates multiple options to adapt to the experiment at hand. At its simplest, the Gas Bench is a head space sampling tool that is used to measure δ18O and δD of natural waters, &delta13C of dissolved inorganic carbon (DIC) in natural waters, or δ18O and δ13C of inorganic carbonates. Furthermore, at UCSC, the Gas Bench has been modified and configured to run δ15
N and δ18O of nitrates in natural waters.
Operationally, headspace gas (H2, N2, O2,N2O, CO2) sealed in a vial (1) is entrained in a helium stream via a sampling needle (2). The flushed gas is dryed (3) in a nafion dreyer and either streams through a fixed volume (typically 100 µL) or is cryogenically trapped in an arm of a six-port valve (4, red loop). All or part of this gas is then sent toward the isotope ratio mass spectrometer by actuating the six-port valve (4, blue loop).
Before reaching the mass spectrometer, the gas passes through a gas chromatographic column (5), to separate interfering gases that may compromise the isotopic analyses, passes through a second nafion gas dryer, and the introduced into the mass spectrometer via an active open split (6).