Simultaneous determination of neurotransmitters and a neuroprotector in human blood serum and urine samples using a diazonium grafted gold nanoparticle film electrode

An electrode modified with a film of aminophenyl grafted gold nanoparticles (AP-AuNPs) was used for the simultaneous determination of the neurotransmitters dopamine (DA) and adenosine (AD) in the presence of the neuroprotector guanosine (GN) at physiological pH. A bare glassy carbon electrode was unable to resolve the voltammetric signals of DA, GN and AD as a result of surface fouling caused by the oxidation products. However, the electrode modified with an AP-AuNP film separated the voltammetric signals of DA, GN and AD with potential differences of 800 mV between DA and GN and 340 mV between GN and AD; their oxidation peak currents were also enhanced. The simultaneous determination of DA, GN and AD was successfully achieved at the electrode modified with an AP-AuNP film using differential pulse voltammetry. The amperometric current response increased linearly with increasing concentrations of DA, GN and AD in the ranges 4.0 x 10(-8) to 1 x 10(-4) M, 7.0 x 10(-8) to 5 x 10(-5) M and 2.0 x 10(-7) to 1 x 10(-4) M, respectively, and the detection limits were 8.0 x 10(-11) M for DA, 2.6 x 10(-8) M for GN and 5.1 x 10(-8) M for AD (S/N = 3). The practical application of the electrode modified with an AP-AuNP film was demonstrated by simultaneously determining the concentrations of DA, GN and AD in human blood serum and urine samples.