Fabrication of electrolytic cell for online post-column electrochemical derivatization in ion chromatography |
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Authors: | Shuchao Wu Wei Xu Bingcheng Yang Mingli Ye Peimin Zhang Chao Shen-Tu Yan Zhu |
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Affiliation: | 1. Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028, Zhejiang, PR China;2. State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310028, Zhejiang, PR China;3. School of Pharmacy, East China University of Science and Technology, Shanghai 200237, PR China;4. Thermofisher scientific (China), Shanghai 201203, PR China;5. College of Biology and Environmental Engineering, Zhejiang Shuren University, Hangzhou 310015, PR China |
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Abstract: | An electrolytic cell (EC), composed of two ruthenium-plated titanium electrodes separated by cation-exchange membranes, was fabricated and evaluated for online postcolumn derivatization in ion chromatography (IC). Folic acid (FA) and methotrexate (MTX) were preliminarily used as prototype analytes to test the performance of EC. After separation by an anion exchange column, FA and MTX, which emit very weak fluorescence when excited, were electrochemically oxidized online in the anode chamber of the EC. The compounds with strong fluorescence, which are oxidation products, were detected by the fluorescence detector. The phosphate buffer solution (100 mM KH2PO4) served as an optimal eluent for anion exchange chromatographic separation and a suitable supporting electrolyte for electro-oxidation, leading to ideal compatibility between IC separation and the postcolumn electrochemical derivatization. For the presently proposed method, the linear ranges were from 0.01 mg L−1 to 5 mg L−1 for both FA and MTX. The detection limits of FA and MTX were 1.8 and 2.1 μg L−1, and the relative standard deviations (RSD, n = 7) were 2.9% and 3.6%, respectively. The method was applied for the simultaneous determination of FA and MTX in the plasma of patients being treated for rheumatoid arthritis. The determination of MTX in the urine of the patients of diffuse large B cell lymphoma was also demonstrated. |
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Keywords: | Electrolytic cell Electrochemical derivatization Ion chromatography Fluorescence |
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