ABSTRACT
This work describes an electroanalytical investigation of dopamine using cyclic voltammetry (CV) and the graphite-polyurethane composite electrode (GPU). In CV studies, well-defined redox peaks characterize the oxidation process at the GPU electrode, which is indicative of electrocatalytic effects associated with active sites on the GPU electrode surface. A new analytical methodology was developed using the GPU electrode and square wave voltammetry (SWV) in BR buffer solution (0.1 mol L(-1); pH 7.4). Analytical curves were constructed under optimized conditions (f=60s(-1), DeltaE(a)=50 mV, DeltaE(I)=2 mV) and detection and quantification limits of 6.4x10(-8) mol L(-1) (12.1 microg L(-1)) and 5.2x10(-6) mol L(-1) (0.9 mg L(-1)), respectively, were achieved. The precision of the method was checked by performing ten successive measurements for a 9.9x10(-6) mol L(-1) dopamine solution. For intra-assay and inter-assay precisions, the relative standard deviations were 1.9 and 2.3%, respectively. In order to evaluate the developed methodology, the determination of dopamine was performed with good sensitivity and selectivity, without the interference of ascorbic acid in synthetic cerebrospinal fluid, which indicates that the new methodology enables reliable analysis of dopamine.
Subject(s)
Dopamine/cerebrospinal fluid , Electrochemistry/methods , Graphite/chemistry , Polyurethanes/chemistry , Electrodes , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
The association constant of isothiocyanic acid, HNCS, has been determined potentiometrically and found to be 0.135 +/- 0.007 and 0.168 +/- 0.007 at ionic strengths (NaClO(4)) of 2.0 and 4.0M respectively. The indicator electrode was Hg(SCN)(2-)(4)/Hg. For accuracy and precision the metal phase was used in the form of a dropping electrode. Because the association constant is so low, liquid-junction potentials would cause significant errors, since a strong acid was added to the working solutions in the procedure, and an estimate of this effect was taken into account.
