A previously reported single-column gas chromatographic separation method was modified for dual detection gas chromatography (TCD + FID) and evaluated for the low concentration analysis of volatile anaesthetics (halothane, isoflurane) and nitrous oxide. It was found that no serious problem occurs in the determination of volatile anaesthetics with FID (<10 ppm), but nitrous oxide introduces lack of sensitivity at lower concentrations with TCD (<40 ppm) in the described analysis method with a 0.25 mi sample loop.