Gas Analysis Techniques
Analysis Techniques for Gases in Breakseals ( H2, CO2, SO2)
Pyrex tubes are used off-line to cryogenically trap selected gases, and are sealed with a torch. The most common size of tube or "breakseal" is 6mm outer diameter,and about 14cm in length.
There are two methods to analyse the gas in a breakseal:
Breakseals are loaded into the cracker tubes of the 10-port manifold on the Thermo Finnigan DeltaPlus, and pumped for 15 minutes. The breakseals are snapped to release the contained gas. The gas is run in dual-inlet against a calibrated reference gas. If there is less than about 20 micromoles of gas, then the microvolume (cold finger) must also be used to pull the gas into a smaller volume before analysis. Samples are run against a calibrated reference gas.
The analytical precision (2 sigma) for carbon isotopes is +/- 0.05 permil.
Breakseals are loaded one by one into a cracker tube attached to an off-line combination vacuum line and helium line. The cracker tube is evacuated. The breakseal is snapped, then helium is used to flush the sample gas into an Exetainer which can then be run as a regular headspace sample on the GasBench + Thermo Finnigan DeltaPlusXP IRMS. Aliquots of the calibrated reference gas used in dual-inlet are run with the samples to enable normalization of the data.
The analytical precision for carbon and oxygen is +/- 0.1 permil.