Coated surface acoustic wave sensor employing a reversible mass-amplifying ligand substitution reaction for real-time measurement of 1,3-butadiene at low- and sub-ppm concentrations

Abstract

Real-time measurement of 1,3-butadiene gas using a surface acoustic wave (SAW) sensor coated with the square-planar Pt(II)-olerin pi-complex PtCl2-(1-hexene)(pyridine) and related complexes is described. Amplification of the sensor response results from displacement of two 1-hexene molecules by each butadiene molecule and formation of the bridged complex [PtCl2(pyridine)]2(1,3-butadiene). Using a 30-MHz SAW oscillator, the rate of frequency change is linearly related to the butadiene air concentration from 150 ppb to greater-than-or-equal-to 13 ppm and a calculated detection limit of 101 ppb is obtained. Using a 60-MHz oscillator, the detection limit is reduced to 24 ppb. No effect on the sensor response is observed with changes in relative humidity from 5 to 80 % or changes in temperature from 25 to 35-degrees-C. No interference is observed from several industrially relevant non-olefin organic gases and vapors. Responses are obtained for several olefins, but they interfere with the response to butadiene only at higher relative concentrations. The reagent can be regenerated repeatedly by brief exposure to 1-hexene vapor with retention of the original response characteristic upon subsequent exposure. The potential for using this sensor to monitor occupational 1,3-butadiene exposures is discussed in light of the recently proposed occupational exposure limit of 2 ppm.