Multiple component analysis of cigarette combustion gases on a puff-by-puff basis using a dual infrared tunable diode laser system

A dual infrared tunable diode laser system (IR-TDL) has been developed for the simultaneous detection of multiple gaseous components in cigarette smoke. The high spectral resolution (0.001 cm(-1)) and rapid time response (20 Hz) of the TDL system are ideal for separating the absorptions from the multitude of gas phase components found in this matrix. The combustion products are sampled into a 0.3 liter, 18 meter multiple pass absorption cell with a flow response time of 0.15 seconds, which provides ample time resolution to observe variations within each 2-second puff. Two independent beam paths allow simultaneous detection in two wavelength regions; the first for ethylene and ammonia and the second for formaldehyde. Rapid scan-sweep integration with direct absorption permits absolute gas concentrations to be determined on-line. A nonlinear least squares procedure is used for "fingerprint" fitting of up to four gases with each diode. Results demonstrating the instrument sensitivity and rime response, along with potential caveats, for several gaseous components will be presented.