Analysis

The laboratory is equipped with a variety of high-quality instruments for analyzing the samples that are gathered from the high-pressure shock tube. The main instruments are two HP-6890 gas chromatographs, GCs, which are equipped with gas sampling valves, GSVs. These GSVs are used to introduce the gaseous samples onto the analytical columns in a precise and repeatable manner. After a species elutes from a column it can be fed to a variety of different detectors including FID, TCD, ECD and NPD. In addition to these standard detectors one of the gas chromatographs is coupled to a HP-5973 mass spectrometer that allows us to obtain structural information about a species and aids in the identification of unknown molecules in the sample.

Some of the species that are produced in a reaction are present in only very small concentrations. Consequently, we also have a CDS-6000 purge and trap injector that concentrates our sample by removing the bath gas attached to one GC.

The samples obtained from the shock tube can be at pressures in excess of 2000 psi. These high pressures are incompatible with the GC and therefore it is necessary to reduce the pressure of the sample before admitting it to the GC. To this end a portion of the sample gas is admitted to a pressure vessel attached between the sample vessel and the GC inlet. A side vent on the vessel is opened to allow gas to flow out of the vessel until the pressure in the pressure reduction vessel is one atmosphere. Gas is then allowed to flow from the pressure reduction vessel to the GC.

GC/MS analytical system in the high-pressure shock tube laboratory

Diagram of sample rig used to introduce gaseous samples into the GC/MS