Hydrophobicity‐aided potentiometric detection of catecholamines,beta‐agonists,and beta‐blockers in a mixed‐solvent capillary electrophoresis system |
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Authors: | Grzegorz Bazylak Maria Eugenia Monge Joseph Everaert Luc Joseph Nagels |
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Institution: | 1. Instituto de Quimica Fisica de Materiales, Ambiente y Energia (INQUIMAE), Departamento de Quimica Inorganica, Analytica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina;2. Department of Chemistry, Faculty of Science, University of Antwerp, Antwerp, Belgium |
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Abstract: | A series of cationic drug‐like substances with distinct basicity, hydrogen‐bonding ability, and hydrophobicity, including three catecholamines, two beta‐agonists, and thirteen beta‐blockers, was successfully detected in a capillary electrophoresis system using an end‐capillary coupled potentiometric sensor consisting of a PVC‐based liquid membrane deposited directly on a 100 μm diameter copper rod. The electrophoretic separation was performed on a 72 cm×75 μm id uncoated fused‐silica capillary with an acidic background electrolyte containing phosphoric acid in a water–acetonitrile mixture, pH* 2.8. Samples were injected electrokinetically at 5.0 kV for 10 s and a running voltage of 19.5 kV was applied. Excluding the bufuralol/practolol pair, baseline separation of all substances was achieved in the developed CE system within 9 minutes. A linear relationship (R2 0.8752) between the sensitivity of the applied potentiometric detector and the parameter log P characterising the hydrophobicity of the analytes was demonstrated. The best observable limits of detection (LODs) were obtained for the highly hydrophobic substances, i. e. bufuralol (8.10×10–8 M injected concentration, S/N = 3), propranolol, alprenolol, and clenbuterol (ca. 1.10×10–7 M). In the case of hydrophilic catecholamines and carbuterol their LODs with potentiometric detection were lowered by a factor of almost one thousand, reaching a value of 6.6×10–5 M. |
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Keywords: | Aqueous‐organic buffers Basic drugs Capillary electrophoresis Potentiometry Neurotransmitters |
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