| Summary: | 碩士 === 國立臺灣師範大學 === 化學研究所 === 90 === Piezoelectric(PZ) quartz crystal is well-known to be sensitive to pressure exerted on its surface. The vibrational frequency of an oscillating piezoelectric quartz crystal decreases when a foreign substrance is adsorbed onto its surface. This phenomenon enables us to detect the characteristics of the substance. In this study, a multi-channel piezoelectric quartz crystal gas detection system with various organic material coated quartz crystals and a home-made computer interface for data processing were prepared and employed to detect various organic pollutants from PVC plants such as methanol, formic acid, propionaldehyde, carbon disulfide and N,N-dimethyl formamide.
The principal component analysis (PCA) method was than applied to analyze the signals from each channel with each coating material, and the appropriate coating materials for organic pollutants were selected. After performing PCA assay, the data set obtained from 29 piezoelectric crystal sensors for 5 analytes and the first three factors of the reduced set explained 98.66﹪of the variation. Six representative coating materials such as C60/PPA, Polyethylene glycol, Nafion, Triphenyl phosphine, Cryptand-22 and Polyvinyl pyrrolidone were selected. Five vaporized organic pollutants, Methanol、Formic acid、Propionaldehyde、Carbon disulfide and N,N-Dimethyl formamide could be effectively distinguished from PCA Scores Map generated by employing factor 1(PRIN1) as the x-axis and factor 2(PRIN2) as the y-axis. Furthermore, since different evaporated organic molecules tend to have distinguishing profile discrimination maps, profile discrimination maps can be used as finger-prints for distinction.
Effects of coating load, concentration and interference of water were also investigated and discussed. The result of multi-channel piezoelectric quartz crystal gas detection system showed the good detection limit, but the detection with some coating materials such as Polyvinyl pyrrolidone was found to be interfered by water.
The relationship between concentration and profile discrimination maps of organic mixtures with methanol, carbon disulfide, propionaldehyde and N,N-dimethyl formamide detected by the six-channel piezoelectric detection system were also probed and discussed afterward in this study. By comparing the signal intensity of specific axis in profile discrimination maps of the organic mixtures, specific gases could be identified. The multichannel piezoelectric crystal detection system developed in this study can be potentially expected to be applied for organic pollutants from other polymer industrial plants.
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