Process control with mass-sensitive chemical sensors - Cyclodextrin modified polymers as coatings

Chemical sensors can also be used for process control since they are able to follow concentration changes nearly instantaneously. The mass sensitive quartz-microbalance (QMB), coated with cross-linked cyclodextrin cavities was applied to monitor the formation of the Grignard reagent. It was possible to detect the reactant chlorobenzene even in a saturated diethyl ether atmosphere down to some ppm (mu L/L). This is equivalent 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 application, 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 derivative.