Determination of Ethylene and lsoprene in the Gas Phase of Cigarette Smoke by Infra-red Spectroscopy

An infra-red method was developed for the quantitative determination of ethylene and isoprene in the gas phase of cigarette smoke. The smoke was collected by smoking the cigarettes on a five-port syringe type smoking machine and transferring it to a gas cell positioned in a double-beam infra-red spectrophotometer for the duration of the analysis. The smoke transfer to the gas cell and its subsequent removal from the celI were accomplished by connecting the smoking machine to a vacuum pump through the automated solenoid valve unit which controlled the analysis system. In this manner any specific puff of interest could be analysed for the ethylene and isoprene concentrations by measuring the corrected absorbance of the 10.52 µm and 11.18 µm absorbance bands, respectively. TotaI deliveries of ethylene and isoprene per cigarette were obtained by adding the deliveries from the individual puffs. The puff-by-puff delivery profile also was obtainable at the same time. In addition filter efficiency for ethylene and isoprene removaI may be determined by this method. The relative standard deviation at the two-sigma level was 3 % for ethylene and isoprene in the gas phase smoke from commercial cellulose acetate filter cigarettes. The analysis of a particular puff of smoke required only 75 seconds insuring the analysis of a relatively fresh smoke with good reproducibility and accuracy.