Simultaneous determination of hydrogen, methane, and carbon monoxide in water by gas chromatography with a semiconductor detector

A portable gas chromatograph with a semiconductor detector (GC/SCD) has been constructed and used in the held for measurements of H-2, CH4, and CO in water. These gases were separated:from water by the headspace method in a 100-mL glass bottle with 80 or 90 mt of a water sample. A 1- or 2-mL portion of the headspace was injected into the GC/SCD;after complete equilibration between the gaseous and aqueous phases. Hydrogen, CH4, and CO were separated from each other through a column packed with molecular sieve 13X-S and detected by the SnO2 semiconductor sensor. Nitrogen and O-2 were used as a carrier gas and an additive gas for the sensor, respectively. Using standard gases in the field studies, the SCD exhibited a linearity at least up to 140 pmol with low detection limits of 1.4, 0.55, and 0.26, pmol for H-2, CH4, and CO, respectively. The good analytical results obtained for water samples at marine, lake, and wetland sites showed the GC/SCD to be an efficient analytical system for these reduced gases in natural waters.