Industrial applications of SAW-sensors:: on-line control of preparative HPLC

Results of on-line process control with an SAW-sensor based gas-sensor microsystem (SAGAS PC) are presented for industrial applications. The control of the solvent mixer of an HPLC-system was chosen as a typical example. All applications dealt with the detection and subsequent qualification as well as quantification of volatile organic compounds (VOC's), e.g. organic solvents or even water by investigating their vapor. Mass-sensitive transducers, especially surface acoustic wave (SAW)-devices, have become a feasible tool for VOC-analytics. The measurement principle is based on frequency changes which are directly correlated with mass changes on the sensor surface and thus provide a particularly suitable signal transduction. The data analysis of all applications is based on pattern recognition methods, and focused on artificial neural networks for quantitative determination of these solvents and solvent-mixtures. The results obtained clearly showed the suitability of such a sensor system for on-line process-control purposes.