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 field for measurements of H2, 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 mL 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 O2 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 H2, 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.