Gas Chromatography in the Low Concentration Determination of Nitrous Oxide and Volatile Anaesthetics

Anaesthetic pollution is of interest to people subject to low concentrations of all types of gases and volatile anaesthetic during occupational activities. The decrease in recent years in the number of relevant publications does not necessarily mean that pollution has gone away or that the problem has been solved. A number of coincidental factors have brought the matter back into consideration. Although some aspects of the hazardous effect of low-concentration exposure to anaesthetics have been satisfactorily explained, new questions have been raised . Therefore, there is still a need for methods which will allow simultaneous analysis of volatile anaesthetic (halothane, isoflurane) and nitrous oxide from the operating theatre or intensive care unit, atmospheres or else at low concentration level. This type of analysis method is usually associated with gas chromatography2−6 . However, the separation of multi-component mixtures (including light gases) is an important step in gas chromatography, as the remarkably different physical and chemical nature of the components makes the simultaneous detection of the anaesthetics studied more difficult after the separation. For example, the thermal conductivity detector (TCD) is known to be insufficiently sensitive for measurements of low concentrations7−9 . The electron capture (ECD) and flame ionisation (FID) detection systems are much more sensitive to these components, but ECD is non-linear and FID does not respond to nitrous oxide, and both types of detectors are of a destructive character, making a serial connection impossible . To overcome this difficulty, a previously described gas chromatographic separation system was modified for dual-detector gas chromatography in order to detect both inorganic gases (with TCD) and anaesthetic vapours (with FID) at low concentration levels.