- 期刊
使用不鏽鋼電極研究酸鹼度對電極極化阻抗的影響
The influence of pH on electrode polarization impedance using stainless-steel electrode
摘要
電化學與生醫臨床應用上普遍使用三電極系統測量in vitro或in vivo的阻抗值，由於三極系統的工作電極同時擔負提供電流與量測電壓的角色，所以必須定量分析電極介面的極化阻抗大小方能獲得實際的待測阻抗值。依照電極極化Bockris-Davanathan-Muller模型的描述，陰離子可以突破outerHelmholtz plane (OHP)在電極表面形成特性吸附，因而影響電極的極化阻抗；相似的，OH^-與H_3O^+也可以如同特性吸附的陰離子突破OHP接近到電極的表面，因此酸鹼度的改變應該也可以造成極化阻抗的變化，但是，目前探討不鏽鋼電極的極化阻抗與酸鹼度的相關性的研究較少。在這個研究中我們使用兩電極系統，當兩極系統的參考電極面積遠大於工作電極面積時，非對稱的兩極系統將近似三極系統。研究中以時安培法(chronoamperometry)於不鏽鋼工作電極上施加相對於參考電極 0.8伏特的步級電壓 (potential step)，同時測量電極極化的瞬態電流，並分析極化阻抗。結果顯示，不鏽鋼工作電極與0.1 M KCl水溶液(pH 5.5)介面的極化阻抗對10^(-4) M HCl (pH 4.2)的濃度變化遠比10^(-2) M KCl(pH 5.7)的變化敏感，在磷酸鹽緩衝溶液中，溶液pH 5.9的極化電流也與溶液pH 7.0的極化電流有明顯的分別。這些結果顯示在使用不鏽鋼電極進行測量時，待測物的酸鹼值將影響量測的阻抗值。由於不鏽鋼電極被廣泛使用於生物醫學的量測，進一步定量分析酸鹼度對於阻抗測量的干擾應值得更多的研究。
並列摘要
The three-electrode impedance system is widely used not only in electrochemistry but also in biomedical in vivo assessment. Because the working electrode used in the three-electrode system serves both to carry current and to measure voltage, quantitative analysis of electrode polarization impedance (EPI) is of great importance. According to the Bockris-Davanathan-Muller model, anions could penetrate outer Helmholtz plane and form specific adsorption to influence EPI. In the same vein, because OH^- and H_3O^+ could also approach to electrode surface, it seems reasonable that pH will influence the EPI. In this study, we used chronoamperometry technique in which 0.8 volt potential step of the working electrode was applied higher than the reference electrode. The results indicate that EPI in 0.1 M KCl solution (pH 5.5) is more sensitive to 10^(-4) M HCl variation (pH 4.2) than to 10^(-2) M KCl variation (pH 5.7) on the stainless-steel electrode. A similar result was also found clearly among pH 5.9 and pH 7.0 phosphate buffer solutions. This result implies that the pH sensitive effect should not be neglected on the measurements using the stainlesssteel electrode.