Quantifying gas sensor and delivery system response time using GC/MS

Semiconducting metal oxide (SMO) chemiresistive sensors have applications for gas detection in chemical, biological, medical and environmental fields. We examine how properties of the sensor test system can introduce errors into measurements of sensitivity, reproducibility and response time of SMO sensors. We describe and characterize the performance of a typical gas delivery system using a gas chromatograph/quadruple mass spectrometer (GUMS) and custom-designed gas sampling system. The accuracy of parameters extracted from the sensor response is assessed from a model that incorporates both the delivery system characteristics and surface reaction kinetics on SMO sensors. Our analysis shows that effects of the test system on response time are significant, particularly at lower concentrations and for less volatile compounds. Sensor to sensor reproducibility is critically dependent upon sensor RTD temperature calibration, while the variation in sensor response from pulse to pulse is controlled by the gas delivery system. (C) 2003 Elsevier B.V. All rights reserved.