Portable instrument employing a surface acoustic wave sensor with a regenerable reagent coating for direct measurement of 1,3-butadiene and styrene

The design and preliminary laboratory testing of a prototype portable instrument capable of near-real-time measurement of selected airborne olefins and dienes at lowand sub-ppm concentrations is described. The sensor employed is a 60-MHz surface-acoustic-wave (SAW) oscillator coated with a Pt-olefin coordination compound having the formula trans-PtC12(olefin)(pyridine) (olefin= 1-hexene or ethylene). The continual inass change that occurs upon replacement of the initially cotirdinated olefin by the olefin or diene analyte leads to a commensurate change in the output frequency of the SAW sensor. Analyte air concentrations can be determined therefore by measuring the rate of frequency change. In tests with 1,3-butadiene and styrene the instrument provided linear response isotherms from 0.050 to 3.0 and 0.60 to 50 ppm, respectively, and calculated detection limits of 0.043 and 0.28 ppm, respectively, based on a 10 s measurement interval. Repeated regeneration of the reagent sensor coating is accomplished automatically by brief exposure to a high concentration of the initially coordinated olefin generated from a reservoir that can be housed within the instrument.