Measurement of nitrogen dioxide in cigarette smoke using quantum cascade tunable infrared laser differential absorption spectroscopy (TILDAS)

Although nitrogen dioxide (NO2) has been previously reported to be present in cigarette smoke, the concentration estimates were derived from kinetic calculations or from measurements of aged smoke, where NO2 was formed some time after the puff was taken. The objective of this work was to use tunable infrared laser differential absorption spectroscopy (TILDAS) equipped with a quantum cascade (QC) laser to determine if NO2 could be detected and quantified in a fresh puff of cigarette smoke. A temporal resolution of ∼0.16 s allowed measurements to be taken directly as the NO2 was formed during the puff. Sidestream cigarette smoke was sampled to determine if NO2 could be detected using TILDAS.Experiments were conducted using 2R4F Kentucky Reference cigarettes with and without a Cambridge filter pad. NO2 was detected only in the lighting puff of whole mainstream smoke (without a Cambridge filter pad), with no NO2 detected in the subsequent puffs. The measurement precision was ∼1.0 ppbV Hz−1/2, which allows a detection limit of ∼0.2 ng in a 35 ml puff volume. More NO2 was generated in the lighting puff using a match or blue flame lighter (29 ± 21 ng) than when using an electric lighter (9 ± 3 ng). In the presence of a Cambridge filter pad, NO2 was observed in the gas phase mainstream smoke for every puff (total of 200 ± 30 ng/cigarette) and is most likely due to smoke chemistry taking place on the Cambridge filter pad during the smoke collection process. Nitrogen dioxide was observed continuously in the sidestream smoke starting with the lighting puff.