The absorption and desorption of chlorobenzene, odichlorobenzene, and chloroform in poly[n-butyl methacrylate] (PBMA) was studied in polymer-coated 104 MHz surface acoustic wave (SAW) sensors, and in freestanding polymer films by thermogravimetric analysis (TGA). The sorption processes were analyzed by a Fickian simulation and best-fit partition, and diffusion coefficients were derived. Good correlations were found between simulated and observed data. Partition coefficients derived from SAW response were independent of coating thickness and were found to be about two to three times bigger than those derived from the gravimetric response. In contrast, the diffusion coefficients increased linearly with coating thickness in the range 70-560 kHz. For the thickest polymer coating, SAW-derived diffusion coefficients were comparable with TGA-related diffusion coefficients. This study reconfirms the finding for other polymers that the response of SAW chemosensors is higher than that anticipated from a mass change only. The viscoelastic effect is again more pronounced than the gravimetric effect. Moreover, the similarity of diffusion coefficients obtained at higher polymer thicknesses suggests that the rate of change of the SAW viscoelastic component is similar to that of the gravimetric element. It is fair to assume that both processes originate from the same event: the absorption of the analyte in the polymer. In this view the polymer-coated SAW sensor may be regarded as an enhanced gravimetric sensor.

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A fast gas chromatograph (GC) equipped with a pulsed‐flame photometric detector (PFPD) was designed and built with the intention of facilitating field analysis of the full range of chemical warfare agents (CWA). This GC‐PFPD system was tested with five organophosphorus and organosulfur CWA simulants that cover the volatility range of common CWA. Fast repetitive analysis was demonstrated with a cycle time as short as 30 s, combined with very low detection limits of 20 ng/m3 for organophosphorus CWA simulants and 200 ng/m3 for organosulfur compounds. With a longer analysis time of 80 s, a 3‐ng/m3 detection limit was demonstrated for DMMP. In the GC‐PFPD system, the separation power of each of these techniques is orthogonal and independent; thus, this hyphenated combination is characterized by a very low false‐alarm rate, combined with CWA identification capability at the molecular level. The large improvement in system selectivity is demonstrated in the direct analysis of a low level of triethylphosphate in the headspace of diesel fuel without any interference. The system inlet was heated and the sample path was inert without any metal, enabling fast response time and low detection limits for a low volatility agent such as VX. The same fast GC‐PFPD system could also be quickly and easily switched to a continuous sampling “sniff” mode of operation with 2‐s response time. Alternatively, it could be operated in a novel mode of thermally modulated inlet (TMI) that provided intermediate results between those of GC and “sniff” in terms of the trade‐off of response time and performance. The fast GC‐PFPD system is also characterized by low average hydrogen consumption (about 4 ml/min), small size, and low weight. No attempt was made to complete the system in terms of portable control electronics. The advantages and unique features of this system, as well as the importance of CWA identification at the molecular level, are discussed. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 170–194, 2000

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