Electrochemical recognition of tryptophan enantiomers using a multi-walled carbon nanotube@polydopamine composite loaded with copper(II)
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The work describes a voltammetric method for the recognition of tryptophan (Trp) enantiomers. A glassy carbon electrode (GCE) was modified with polydopamine-coated multiwalled carbon nanotubes and subsequently loaded with copper(II) ions. The morphology and structure of the material were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and electrochemical methods. The recognition of Trp enantiomers by the modified GCE was investigated by differential pulse voltammetry. Under optimum conditions, the sensor revealed a linear range from 1.0 to 100.0 μM with the limit of detection values of 0.15 μM and 0.20 μM for D-Trp and L-Trp, respectively. The recognition efficiency for the Trp enantiomers (with a chiral separation factor of 5.4 for L-Trp over D-Trp) is much higher than that of other electrodes. This is assumed to be due to the unique features of MWCNTs, PDA and Cu(II). After optimizing various experimental conditions, the method was successfully applied to chiral sensing of Trp isomers in a racemic mixture. The potential application to chiral separation of the amino acids phenylalanine and tyrosine was also evaluated, with a chiral separation factor of 2.14 and 1.33 for L−/D-phenylalanine and L−/D-tyrosine, respectively.
KeywordsChiral recognition Chiral sensing Tryptophan Electrochemical sensors Chiral amino acids
We acknowledge the support from the National Natural Science Foundation of China (21607061), the Natural Science Foundation of Jiangsu Province (BK20190543)the Opening Project of State Key Laboratory of Chemo/Biosensing and Chemometrics of Hunan University (2018019), the Priority Academic Program Development of Jiangsu Higher Education Institutions, Collaborative Innovation Center of Technology and Material of Water Treatment, and the Program of Young Backbone Teachers in Jiangsu University (2015).
Compliance with ethical standards
The author(s) declare that they have no competing interests.