Fundamental studies of analyte/film interactions and their applications for chemical sensor devices

Coated Surface Acoustic Wave (SAW) devices typically measure vapor concentrations during vapor/film equilibrium. However, many practical sensor applications require the analysis of pulsed sample streams. Thus, the research described was motivated by the desire to develop SAW chemical sensor systems to detect environmentally important compounds utilizing pulsed sample introduction.; A semi-automated pulsed injection and data analysis system utilizing 200 MHz SAW resonators has been constructed. A cell consisting of separate sample splitting chamber, sample transfer lines, and sensor device areas allows temperature control over the individual regions. Injections involving hexane, trichlorobenzene, and 1% (w/v) of biphenyl in hexane show that all three temperatures play an important role in the magnitude and time dependency of the SAW response.; The interactions of various classes of compounds with poly(isobutylene) (PIB) coated SAW devices and quartz crystal microbalances (QCM) have been examined. For the pulsed system, a new parameter ("pulse coefficient") has been developed that is analogous to the partition coefficient in a continuous flow system. Using the pulse coefficients, Linear Solvation Energy Relationships (LSER) were calculated that provided insight into analyte/film interactions. Pulse coefficients and LSER calculations compare favorably with values reported for continuous flow SAW and GLC experiments.; PIB films coated on SAW devices and FTIR/ATR internal reflection elements were exposed to nitromethane, isooctane, and perchloroethylene vapors. A correlation was found between a spectroscopic indication of vapor induced polymer swelling and the responses of the polymer coated SAW devices. Sorption of perchloroethylene and isooctane caused PIB films to swell significantly while sorption of nitromethane swelled PIB films to a lesser degree. The observed polymer swelling occurs nearly simultaneously with analyte sorption, and both IR and SAW results indicate that the polymer swelling changes were reversible.; The responses of uncoated, PIB, poly(vinyl alcohol), and OV-275 coated SAW devices to 4% (w/v) biphenyl or 500 ppm pentachlorobiphenyl (PCB) in acetone, methanol, or hexane have been determined. SAW results obtained from the PIB coated devices indicate that dispersion forces are most important for both biphenyl and PCB. The nature of the solvent does not affect the sensor response to biphenyl. However, the response to PCB in hexane is larger than for PCB in methanol and acetone, regardless of polymer coating.