A static calibration method for the gas chromatographic determination of per cent concentrations of volatile anaesthetic agents.

A method is described for preparing static standards of per cent concentrations of volatile anaesthetic agents, that is designed to minimize adsorptive losses in the container used for the standards. The extent to which this aim has been realized was investigated for atmospheres of halothane, enflurane and isoflurane, both by monitoring the relative concentration within the container over a period of 30 min after the standard was prepared, and by measuring the absolute concentration of the volatile agents. Gas chromatography was used for both sets of measurements, with liquid standards being used for the absolute measurements. No discernible loss of volatile agent occurred over the 30-min period, and the measured concentrations agreed closely with the predicted values. The standard mixtures prepared by the method were suitable for calibrating a gas chromatograph, and allowed accurate determinations of volatile anaesthetics to be made. The relative standard error of the predicted concentration for a single standard mixture was less than 0.5%, and the calibration accuracy could be further improved by taking the mean chromatograph response to several standard mixtures prepared in succession.