PROCESS-CONTROL WITH MASS-SENSITIVE CHEMICAL SENSORS - CYCLODEXTRIN MODIFIED POLYMERS AS COATINGS

Chemical sensors can also be used for process control since they are a ble to follow concentration changes nearly instantaneously. The mass s ensitive quartz-microbalance (QMB), coated with cross-linked cyclodext rin cavities was applied to monitor the formation of the Grignard reag ent. It was possible to detect the reactant chlorobenzene even in a sa turated diethyl ether atmosphere down to some ppm (mu L/L). This is eq uivalent to a molar ratio of 50000:1 of diethyl ether to chlorobenzene . The sensor characteristic is completely linear in the concentration range from 10 to 500 ppm (mu L/L) chlorobenzene. As a practical applic ation, the end point of the Grignard reaction can be determined in an accuracy of approximately 2% of the reagent supply. This was achieved by a direct on-line acquisition of the QMB frequency response or its d erivative.