A modified method for diffusive monitoring of 3-ethenylpyridine as a specific marker of environmental tobacco smoke

A previously introduced method for monitoring environmental tobacco smoke (ETS) was further validated. The method is based on diffusive sampling of a vapour-phase marker, 3-ethenylpyridine (3-EP), with 3 M passive monitors (type 3500). Experiments were done in a dynamic chamber to assess diffusive sampling in comparison with active sampling in charcoal tubes or XAD-4 tubes. The sampling rate for 3-EP collected on the diffusive sampler was 23.1±0.6 mL min−1. The relative standard deviation for parallel samples (n=6) ranged from 4% to 14% among experiments (n=9). No marked reverse diffusion of 3-EP was detected nor any significant effect of relative humidity at 20%, 50% or 80%. The diffusive sampling of 3-EP was validated in field measurements in 15 restaurants in comparison with 3-EP and nicotine measurements using active sampling. The 3-EP concentration in restaurants ranged from 0.01 to 9.8 μg m−3, and the uptake rate for 3-EP based on 92 parallel samples was 24.0±0.4 mL min−1. A linear correlation (r=0.98) was observed between 3-EP and nicotine concentrations, the average ratio of 3-EP to nicotine being 1:8. Active sampling of 3-EP and nicotine in charcoal tubes provided more reliable results than sampling in XAD-4 tubes. All samples were analysed using gas chromatography-mass spectrometry after elution with a 15% solution of pyridine in toluene. For nicotine, the limit of quantification of the charcoal tube method was 4 ng per sample, corresponding to 0.04 μg m−3 for an air sample of 96 L. For 3-EP, the limit of quantification of the diffusive method was 0.5–1.0 ng per sample, corresponding to 0.04–0.09 μg m−3 for 8 h sampling. The diffusive method proved suitable for ETS monitoring, even at low levels of ETS.