Nafion-Modified Infrared Chemical Sensor for Selective Detection of Arginine in Biological Sample

• Main Authors: Mon-Yu Lu, 呂滿玉
• Other Authors: 楊吉斯
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/35963185927604977794

碩士 === 國立中興大學 === 化學系所 === 95 === In this work, an evanescent wave type of infrared (IR) chemical sensor for the detection of arginine was developed to integrate the advantages of IR spectroscopy into chemical sensing technology. Arginine bears a quanidine moiety, which exhibits positive in charge in acidic to weak base solutions. To sensitively and selectively detect this compound, a negative-charged polymer of nafion was chosen to modify the surface of IR internal reflection elements (IREs). This polymer contains a sulfonate group that can selectively interact with quanidine moiety in arginine. Besides, nafion provides other unique properties, such as chemical inertness, nonelectroactive, and hydrophilic nature. These properties can further improve the performance of IR sensor in detection of arginine in biological or environmental samples. To modify the surface of IREs, two methods were proposed including drop-coating and dip-coating methods. Comparing both reproducibilities and homogeneities of the modified IR sensor using these two methods, dip-coating method provided a superior performance. To characterize the performances of the nafion-modified IR sensor, the basic properties of nafion were first examined. Results indicated that nafion was water stable for long period of time. It is not sensitive to pHs as the variations of the IR absorption bands of nafion were not significantly varied for pH ranged from 3 to 11. Also, the thickness of the nafion thin film could be simply controlled by using different concentration of coating solutions of nafion. To optimize the detection conditions, the influences of pH of arginine solution, the response behaviors, and the adsorption behavior were studied. Results indicated that the optimal pH of the sample solution was found at a pH in the range of 8.5 to 10.0. Also, the detection speed was fast and it reached 95% of the maximum signals in a detection time of ca. 10 min. Two speeds in detection of arginine with different concentrations were found indicating that the mechanisms for nafion-modified IR sensor in detection of arginine contain both surface adsorption and diffusion behavior. In terms of quantitative analyses, the selectivity of nafion-modified IR sensor in detection of arginine was studied by addition of second interference component into the sample solutions. Several classes of interference species were examined including amino acids, organic species, cations, and anions. Results indicated that lysine and histidine could also be detected due to the positive-charge nature. Fortunately, the IR absorption band of quanidine moiety has no spectral interferences from these two amino acids and can be used quantitatively for the detection of arginine. Organic species and anions are generally no effect to the analytical signals. Among the examined cations, few of them affected the analytical signals significantly. Results showed that the linear range was up to ca. 200 μM with an estimated detection limit of ca. 300 nM.