Electrochemical determination of sulfanilamide at preanodized screen-printed carbon electrodes

[[abstract]]本研究是在網版印刷碳電極 (screen-printed carbon electrode, SPCE)上以電化學氧化方式製備過氧化電極 (SPCE*)，針對磺胺 (Sulfanilamide, SAA)進行微量的定量分析。由於台灣食品管理局規定食品中磺胺最低檢出濃度標準不得超過0.1 ppm，如今符合此規定的分析技術包含HPLC、MS、LC等貴重儀器。而這些儀器設備昂貴，因此我們開發出可降低成本、方便檢測的電化學偵測技術，以此修飾電極進行磺胺的定量分析。 本研究利用循環伏安法(cyclic voltammetry, CV)偵測磺胺時，由實驗結果發現SAA氧化電位在約 +0.25V且電流值不明顯，而在溶液中額外添加鄰苯二酚 (Catechol, CA)後使得SAA的氧化電位降低至+0.15V，電流上升兩至三倍。另外本研究發現利用浸泡方式，可讓SAA吸附在電極上，推測可能因SPCE*表面的含氧官能基團，而讓電極表面帶負電荷性質，並與溶液中帶正電荷CA-SAA相互吸引，因此能使SAA偵測靈敏度提高，進而降低SAA的偵測極限。根據實驗結果發現，改變不同溶液的pH值來觀察SAA和CA的吸附變化。從實驗結果發現在酸性下所得SAA氧化電流值最大，推測由於磺胺在酸性環境下帶正電荷，可明顯吸附至負電荷的電極表面，因此可讓SAA電流值明顯上升，此外在pH 5.0的溶液中偵測SAA穩定性較好。利用差式脈衝伏安法(Differential Pulse Voltammetry, DPV)進行磺胺的定量分析，此分析方法的最低極限檢測值為0.027 M (0.0046 ppm)，能符合國家規定的偵測最低濃度。[[abstract]]In this study, an overoxidized screen-printed carbon electrodes (SPCE*) was prepared for sulfanilamide (SAA) detection. The adsorption behavior of SAA on the SPCE* surface in the presence of catechol (CA) was investigated by electrochemical study. The electrochemical oxidation current distinctly enhanced 2~3 times using cyclic voltammetry (CV) at SPCE* +0.15V a the mixture of CA and SAA solution, in contrast to the very small faradaic current of SAA at +0.25 in the absence of CA. The SPCE* was observed to adsorb adduct of SAA and CA strongly and perform catalytic oxidation of compound. The minimum detection limit of SAA must be less than 0.1 ppm in food according to the rule of Food and Drug Administration (FAD) in Taiwan. The analysis techniques include HPLC、LC and MS, but the instruments are expensive. Therefore we will focus on the development of electroanalytical sensors for accurate and fast screening of SAA. The proposed assay exhibits a low detection limit of SAA in pH 5 under the optimized differential pulse voltammetry (DPV). The detection limit (S/N = 3) is 0.027 M.[[note]]碩