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A voltammetric sensor has been developed for dopamine and tyrosine based on the double modification of polycalconcarboxylic acid (pCCA) and electrochemically reduced graphene oxide (ERGO) on the glassy carbon electrode (GCE). The electrode was first modified with calconcarboxylic acid, followed by the modification with electrochemically reduced graphene oxide (ERGO/pCCA/GCE) over it. The extended п-electron system on pCCA helps to increase the conductivity of the material. The functional groups present on pCCA along with its extended conjugation increase the electrocatalytic effect of the modified electrode. ERGO has good electrochemical properties due to the reduction of oxygen-containing functional groups in their edge plane sites. Rapid electron transfer is possible in the case of ERGO-modified electrodes due to the high proportion of the edge plane defects. When pCCA and ERGO are clubbed together, there will be a synergistic effect of the properties of these two materials. Characterisation studies have been done, and different sensor parameters were optimised. Under optimal experimental conditions, a wide linear range was obtained for the determination of dopamine from 1.00 × 10−5 M to 5.00 × 10−7 M. The determination of tyrosine was possible in two linear ranges, from 7.00 × 10−5 M to 2.00 × 10−5 M and from 1.00 × 10−5 M to 3.00 × 10−6 M. The limit of detection values (LODs) obtained for dopamine and tyrosine were 1.00 × 10−7 M and 9.00 × 10−7 M. Application studies for the determination of the analytes were done in synthetic urine and blood serum using the spike recovery method. The electrochemical sensing of DA and Tyr using ERGO/pCCA/GCE [ABSTRACT FROM AUTHOR]

Monoamine neuromodulators norepinephrine (NE) and octopamine (OA) have been discovered to coexist and are associated with neurological and cardiovascular pathology. Here, we have developed a voltammetric sensor to determine NE and OA individually as well as simultaneously using an eco-friendly and cost-effective amino acid modifier, tyrosine (Tyr), which possesses favourable adsorption sites for the binding of these analytes. At poly-Tyr modified glassy carbon electrode (p-Tyr/GCE), the neuromodulators exhibited increased current response at lower overpotential than at the bare GCE. The submicromolar determination of these neuromodulators on p-Tyr/GCE was demonstrated in linear dynamic ranges (LDR) over 7.00 × 10−6–1.00 × 10−6 M and 9.00 × 10−7–1.00 × 10−7 M for NE and over the ranges 1.00 × 10−5–2.00 × 10−6 M and 1.00 × 10−6–2.00 × 10−7 M for OA with the detection limits of 1.37 × 10−8 M and 4.74 × 10−8 M for NE and OA, respectively. The mechanistic aspects were studied and the electro-oxidation of NE and OA on p-Tyr/GCE was found to be two electrons, two-proton transfer reaction. The utility of the proposed method was validated by the determination of NE in pharmaceutical formulations. [ABSTRACT FROM AUTHOR]