Vanillylmandelic acid (VMA) and homovanillic acid (HVA) are diagnostic markers of neuroblastoma. The purpose of this study was to understand the reason for the discrimination of structural analogues (VMA and HVA) onto a graphite electrode coated with an electrochemically oxidized urea derivative. Density functional theory calculations (DFT), FTIR spectroscopic measurements, and electrochemical impedance spectroscopic measurements were used in this work. Density functional theory calculations (DFT) were used to identify the most suitable binding sites of the urea derivative and to describe possible differences in its interaction with the studied analytes. The FTIR measurement indicated the enhancement and disappearance of NH vibrations on graphite and platinum surfaces, respectively, that could be connected to a different orientation and thus provide accessibility of the urea moiety for the discrimination of carboxylates. Additionally, the higher the basicity of the anion, the stronger the hydrogen-bonding interaction with -NH-groups of the urea moiety: VMA (pKb = 10.6, KAds = (5.18 ± 1.95) × 105) and HVA (pKb = 9.6, KAds = (4.78 ± 1.58) × 104). The differential pulse voltammetric method was applied to detect VMA and HVA as individual species and interferents. As individual analytes, both HVA and VMA can be detected at a concentration of 1.99 × 10-5 M (RSD ≤ 0.28, recovery 110-115%).
- Klíčová slova
- differential pulse voltammetry, electrochemical impedance spectroscopy, neuroblastoma, urea-derivative receptor,
- MeSH
- elektrody MeSH
- grafit * MeSH
- kyselina homovanilová chemie MeSH
- kyselina vanilmandlová chemie MeSH
- lidé MeSH
- neuroblastom * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- grafit * MeSH
- kyselina homovanilová MeSH
- kyselina vanilmandlová MeSH
A new method for the simultaneous determination of two tumour biomarkers, homovanillic (HVA) and vanillylmandelic acid (VMA), using flow injection analysis (FIA) with amperometric detection (AD) at a commercially available boron doped diamond electrode (BDDE) was developed. It was found that this method is suitable for the determination of HVA (in the presence of VMA) and VMA (in the presence of HVA) in optimum medium of Britton-Robinson buffer (0.04 mol L-1, pH 3.0). Calibration dependences consist of two linear parts for both biomarkers, the first one being in the concentration range from 1 to 10 μmol L-1 and the second one from 10 to 100 μmol L-1 (with obtained LODs 0.44 μmol L-1 for HVA and 0.34 μmol L-1 for VMA, respectively). To minimize any negative effects related to the passivation of the working electrode, suitable cleaning pulses (+2.4 V for 30 s) were imposed on the working electrode after each measurement. An attempt to use FIA with multiple pulse amperometric detection to determine both analytes in one run was not successful. Changing potentials in short intervals in multiple pulse detection probably results in mutual interaction of analytes and/or products of their electrochemical oxidation, thus preventing the application of this approach.
- Klíčová slova
- Boron doped diamond electrode, Flow injection analysis, Homovanillic acid, Tumour biomarkers, Vanillylmandelic acid,
- MeSH
- bor chemie MeSH
- diamant chemie MeSH
- elektrochemické techniky přístrojové vybavení metody MeSH
- elektrody MeSH
- kyselina homovanilová analýza chemie MeSH
- kyselina vanilmandlová analýza chemie MeSH
- limita detekce MeSH
- nádorové biomarkery analýza chemie MeSH
- oxidace-redukce MeSH
- průtoková injekční analýza metody MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- bor MeSH
- diamant MeSH
- kyselina homovanilová MeSH
- kyselina vanilmandlová MeSH
- nádorové biomarkery MeSH
