Abstract
In this proof-of-concept study, a highly sensitive electrochemical sensor using a graphite paste electrode modified with ellagic acid and multi-walled carbon nanotubes (MGPE/MWCNTs-EA) was developed for the simultaneous determination of six biomolecules: ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), xanthine (XA), and caffeine (CA). Differential pulse voltammetry (DPV) was performed at a potential range from 0.1–1.2 V vs. Ag/AgCl in phosphate electrolyte (pH 2.0). The modified GPE enabled the simultaneous determination of biomolecules under investigation in human urine and blood serum samples with detection limits ranging from 11–91 nM with recoveries of 94.0–106.0%. The electrochemical performance of the modified GPE for the analytes was stable and reproducible and checked with standard high performance liquid chromatography technique. The data suggested that the modified GPE provided a promising platform for routine quantitative determination of the biomolecules under investigation in quality control studies of real samples collected from food and pharmaceutical products.
Highlights
The quantitative determination of small molecules such as ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), xanthine (XA) and caffeine (CA) is generally performed using separation methods such high performance liquid chromatography (HPLC), ultra-performance liquid chromatography, and capillary electrophoresis [1,2,3,4,5,6,7,8,9,10]
Were analyzed for the anodic peak current (Ipa ) of the respective cyclic voltammograms obtained in the presence of 1.0 mM of [Fe(CN)6 ]3− in 0.1 M KCl of supporting electrolyte (Figure S1B–E)
GPE were analyzed for the anodic peak current (I pa) of the respective cyclic voltam grams obtained in the presence of 1.0 mM of [Fe(CN)6]3− in 0.1 M KCl of supporting trolyte (Figure S1(B–E)
Summary
The quantitative determination of small molecules such as ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), xanthine (XA) and caffeine (CA) is generally performed using separation methods such high performance liquid chromatography (HPLC), ultra-performance liquid chromatography, and capillary electrophoresis [1,2,3,4,5,6,7,8,9,10]. In comparison with separation and spectroscopic techniques, electrochemical methods offer advantages such as low cost, rapid procedures, and simple systems that can be operated for individual and simultaneous determinations without any limitations on the color of sample solutions [19,20]; for better results, the analytes should be redox-active on the surface of the working electrodes (WEs) For this purpose, WEs were modified using different organic/inorganic compounds, nanomaterials, and nanocomposite structures to develop sensors with higher selectivity, sensitivity, and precision for simultaneous determination of more than three biomolecules without extensive use of sample preparation and separation techniques [19,20]. An electrochemical method was developed for simultaneous determination of six biomolecules: AA, DA, UA, Trp, XN, and CA using ellagic acid (2,3,7,8-Tetrahydroxy-chromeno(4,3-cde)chromene-5,10dione, EA (see chemical structures of the modifier and target biomolecules in Scheme 1 and multi-walled carbon nanotubes (MWCNTs) for modification of graphite paste electrode (GE). Ments were performed in compliance with relevant laws and institutional guidelines
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