| Summary: | 博士 === 中原大學 === 化學研究所 === 91 === Abstract
Attenuated total reflection (ATR) infrared sensing method was developed toward detection of high polarity aromatic acids. In this method, the different cavity sizes of cyclodextrins (CDs) were modified to increase the capability in detection of aromatic acids. To overcome the problem in immobilization of polar CDs to the surface of the evanescent waveguide, and high stability in aqueous solution was achieved. Selectivity for CD immobilized sensor was detected for aromatic compounds with different functional groups. Results indicated that this type of sensor provided high selectivity in detection of aromatic acids. To facilitate the use for this method to quantitatively analyses of aromatic acids in aqueous solution, the analytical functions were theoretical considered. Factors that influenced the IR signals were also studied including the effect of detection time, CD loadings, the pH values, and concentrations. The detection limits for aromatic acids at two minutes of detection time can be lower than 100 ppb but the dynamic range in detection was around two orders of magnitude only.
To conduct the behavior of the formation of inclusion complexes of analytes with CD phases, the interaction behavior was theoretical considered and the kinetic data were treated with the developed theoretical equations. Results indicated that the behaviors of the interactions between guest molecules and CDs could be explained by either parallel or consecutive reaction mechanisms. Two types of complexes were observed when aromatic acids interacted with CDs. The formation of less stable complex was highly fast and the time to reach equilibrium could be shorter than few minutes. The formation of more stable complex was also observed and the speed in formation of this type of complex was relatively slow and the time to reach equilibrium could be longer. Based on the observed signals, the amount of complex in less stable form was around three times more than that of the more stable complex.
The sensitivities of immobilized cyclodextrin IR sensing devices in determination of aromatic acids were described in the study. To develop a parameter for determination of the sensitivity in detection of aromatic acids, formation constant was determined and used to correlate with the IR signals. By examination of several aromatic acids, which formation constants are available in the literature, the results indicated that formation constants of inclusion complexes of CDs could be determined in this developed method. Meanwhile, the formation constants played an important indicator for determination of aromatic acids in aqueous solutions.
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