Development and Application of Enzymeless and Selective Electrochemical Sensors

• Main Authors: Chen Jyh-Cheng, 陳志誠
• Other Authors: Zen Jyh-Cheng
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/79074154304850188313

博士 === 國立中興大學 === 化學系 === 94 === An enzymeless electrochemical approach using a preanodized screen-printed carbon electrode for the selective and quantitative recognition of uric acid, urinary creatinine and nitroaromatic compounds. A single-use amperometric uric acid sensor strip, incorporating a three-electrode configuration, has been fabricated on a polypropylene substrate using low cost screen-printing (thick-film) technology to apply for fast monitoring of uric acid in human whole blood. The present report relates to a method of producing a non-enzymatic detecting electrode strip for use on whole blood. Both the working and counter electrodes were prepared by screen printing a commercial carbon ink. The integration on the same support of pseudo-reference electrode was obtained by screen printing a commercial silver ink, and subsequent electrochemical pretreatment. The method does not require plasma separation via centrifugation prior to analysis. Simply by placing a 20 l human whole blood drop on the electrochemical cell is enough for uric acid analysis by square wave voltammetry. The strip is not only tolerable to ascorbic acid interference but also highly reproducible in analytical results. Real human whole blood samples were analyzed by this method and compared to the phosphotungstic acid clinical test procedure with satisfied results. The formation of carbon-carbon bond between the electrogenerated >C=O of the preanodized screen-printed carbon electrode and the active methylene group of creatinine was found to be a key for the observation. X-ray photoelectron spectroscopy was used to probe the surface features. A linear calibration curve in the window of 374 M  3614 M creatinine with a slope and regression coefficient value of 16.7 A/mM and 0.9982, respectively, was observed by square-wave voltammetry. Ten successive detection of 374 M creatinine showed a relative standard deviation of 3.42% indicated a detection limit (signal/noise = 3) of 8.61 M. The disposable in nature of screen-printed electrode can offer a cheap and simple way to clinical analysis. The reduction potential of different nitroaromatic compounds was found to systematically shift with the substituent group at an electrochemically preanodized screen-printed carbon electrode. The preanodization treatment makes the peak sharp and hence provides a precise way to identify the substituent effect on nitroaromatic compounds. By using potential shifts as analytical characteristics of nitroaromatic compounds, a suitable internal standard can be chosen based on the criteria of well-separated peak potential and rarely found in the real sample of interest. Simply by measuring the ratio of peak currents between analytes of interest and internal standard, the analysis can be done in a single run measurement. Both the matrix effect and the variation of electrode during the preparation process can be cancelled out in this approach and thus allows for a high precision analysis. Just by placing a 20 L drop on a single-use amperometric sensor strip incorporating a three-electrode configuration is enough for rapid and sensitive detection of nitroaromatic compounds by square-wave voltammetry. For example, the linear detection range can be up to 100 M with a detection limit of 0.42 M (S/N = 3) in the detection of chloramphenicol. This approach was successfully demonstrated in real sample analysis to verify the applicability of the method. The promising performances open new possibilities for rapid detection of nitroaromatic compounds in environmental and biological samples.