Rapid detection of organophosphate pesticides in aqueous environment using a polysiloxane coated SH-SAW device

The choice of the chemically sensing layer for gas and liquid-phase microsensors greatly influences their sensitivity, selectivity, reversibility, and response time. It has been shown in previous work that poly(epichlorohydrin) (PECH) and polyurethane (PU) coated SH-SAW sensors on 36deg rotated Y-cut LiTaO₃ can be used to reversibly detect organophosphate (OP) pesticides (phosmet and parathion) directly in the liquid phase with high sensitivity. However, these chemical sensors exhibited relatively long response times hindering real-time detection. In this work, a polysiloxane film, poly(methylhydrosiloxane) (PMHS), is investigated to achieve real-time or near real-time detection of OP pesticides in aqueous solutions. Furthermore, using a nonlinear estimation technique in the form of an extended Kalman filter (EKF), parameters containing the sensor transient information are estimated on-line. This additional information is used to further reduce the time required for detection.