Quantification of Benzene in Groundwater Using SH-Surface Acoustic Wave Sensors

A need exists for compact sensor systems capable of in-situ monitoring of groundwater for fuel and oil contamination. The work reported here addresses this need using shear horizontal surface acoustic wave (SH-SAW) sensors, which function effectively in the liquid phase. To achieve enhanced sensitivity and partial selectivity for hydrocarbons, the devices are coated with thin chemically sensitive polymer films. Various polymer materials are investigated with the goal of identifying a set of coatings suitable for a sensor array. The system is tested with compounds indicative of fuel and oil contamination, in particular, BTEX (benzene, toluene, ethylbenzene and xylenes), at relatively low concentrations. Of particular importance is benzene, a known carcinogen. Using responses of the SH-SAW sensor devices coated with three different polymer materials, benzene was quantified in the aqueous phase in the presence of other aromatic interferents. It is shown that various concentrations of BTEX in water can be identified and quantified by evaluation of both steady-state and transient response information. Key words: groundwater, fuel and oil contamination, surface acoustic wave sensors, liquid-phase sensing, benzene, transient response information