SELECTIVITY OF CALIX [6]ARENE-COATED PIEZOELECTRIC QUARTZ CRYSTAL SENSOR FOR THE DETECTION OF SOME ORGANIC AMINE IN GAS FLOW

Abstract

In this study, we developed calixarene-coated PQC sensors for the determination of organic amines in gas faze and study the selectivity of this coated sensor for normal and iso- form of propyl and butyl amines. p-tert-Butylcalix[6]arene compound was applied as piezoelectric quartz crystal (PQC) sensory coatings for the selective detection of volatile organic in gas phase. The AT-cut quartz crystals used in this study (Stanford Research Systems) having a diameter of 25.4 mm and a thickness of 0.33 mm. An oscillator circuit providing an alternating voltage will produce a fundamental frequency of 5 MHz for this particular crystal diameter and thickness. About 10.0 ml of analyte was injected into the mixing chamber with an approximately volume of 250 ml. The measuring chamber with coated PQC has a volume of approximately 5 mL. The concentration of amine sample in mixing chamber and respectively in gas flow was around 40 ppm. Al experiments were conducted at 30^oC. The complexation based on the host–guest interaction between the calixarene coating and the analyte makes the coated PQC sensors sensitive to organic amines and results in quasi-irreversible frequency changes. A PQC sensor coated with a p-tert-Butylcalix[6]arene exhibits different selectivity for amines in gas phase, in the order: iso-propylamine< iso-butylamine<<n-butylamine. The relative selectivity of the analytes is explained by the cavity inclusion of analyte molecule, complete or partial, or by steric hindrance interaction. The application of PQC sensors to gas faze has provided new analytical possibilities for the food control, environmental science, biotechnology and medicine.