Electrochemical determination of dopamine and paracetamol using glassy carbon electrode modified with polyoxometalate and carboxyl functionalized multi-wall carbon nanotubes

In this thesis, individual and simultaneous electrochemical determinations of dopamine (DA) and paracetamol (PAR) were performed using a glassy carbon electrode (GCE) modified with composite prepared by mixing Keggin type {[(C6H16N)5(H2O)2](BW12O40)} polyoxometalate (POM) complex and -COOH functionalized multi-walled carbon nanotubes (f-MWCNT) in certain proportions. Since the amounts of POM complex and f-MWCNT, that will form the POM-f-MWCNT composite, will affect the current response of DA and PAR analytes, the amount of f-MWCNT was kept constant and the amount of POM was optimized to determine the appropriate composition. Structural characterization of the prepared POM-f-MWCNT composite and POM complex was performed by ATR Fourier Transform Infrared Spectroscopy (FT-IR). The surface morphologies of the POM-f-MWCNT composite and the POM complex were examined using the scanning electron microscopy (SEM) method. Electrochemical characterization of the GCE/POM-f-MWCNT electrode was performed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. In the thesis study, the electrochemical determination of DA and PAR was carried out by the DPV method. Individual analysis studies, the linear working range for DA was 4,0-100 μmol L−1 and the detection limit was 0,18 μmol L−1. Two linear working ranges were found for PAR, 0,1-1,0 μmol L−1 and 1,0-40 μmol L−1, and the detection limit was determined as 0,008 μmol L−1. For the simultaneous determination of DA and PAR, the linear working range for DA is 1-200 μmol L−1 and the detection limit is 0.11 μmol L−1; the linear working range for PAR was 0.1-10 μmol L−1 and the limit of detection was 0.01 μmol L−1.