Multi-channel piezoelectric quartz crystal sensor for organic vapours Original Research Article

A multi-channel piezoelectric (PZ) quartz crystal detection system with a home-made computer interface was prepared and employed to detect various organic molecules in a flow system. The oscillating frequency of the quartz crystal decreases on adsorption of organic molecules on the coating materials. The home-made computer interface includes a digital counting system Altera and an Intell-8255 data processing system. In addition, software was written to control the interface and data acquisition. The principal component analysis (PCA) method was applied to select the appropriate coating materials for organic vapours. A dataset for the multi-channel sensor with 14 PZ crystals for 30 analytes was collected. Six appropriate coating materials for various organic vapours such as amine, carboxylic acid, alcohol and aromatic molecules were selected after comparing the correlation between the 14 coating materials and the first four principal component (PC) factors. These organic molecules can be distinguished clearly by the six-channel PZ flow sensor. An artificial neural network, using back propagation (BP), was also used to recognize these organic analytes and it shows the distinction of these organic vapours.