Investigation of Electrochemical Behaviour of Quercetin on the Modified Electrode Surfaces with Procaine and Aminophenyl in Non-Aquous Medium

In this study, cyclic voltammetry and electrochemical ımpedance spectroscopy have been used to investigate the electrochemical behaviour of quercetin (3,3′,4′,5,7-pentahydroxyflavone) on the procaine and aminophenyl modified electrode. The modification of procaine and aminophenyl binded electrode surface with quercetin was performed in +0,3/+2,8 V (for procaine) and +0,4/+1,5 V (for aminophenyl) potential range using 100 mV s-1 scanning rate having 10 cycle. A solution of 0.1 M tetrabutylammonium tetrafluoroborate in acetonitrile was used as a non-aquous solvent. For the modification process a solution of 1 mM quercetin in 0.1 M tetrabutylammonium tetrafluoroborate was used. In order to obtain these two surface, a solution of 1 mM procaine and 1 mM nitrophenyl diazonium salt in 0.1 M tetrabutylammonium tetrafluoroborate was used. By using these solutions bare glassy carbon electrode surface was modified. Nitrophenyl was reduced to amine group in 0.1 M HCl medium on the nitrophenyl modified glassy carbon elelctrode surface. Procaine modified glassy carbon electrode surface was quite electroactive. Although nitrophenyl modified glassy carbon elelctrode surface was electroinactive, it was activated by reducing nitro group into amine group. For the characterization of the modified surface 1 mM ferrocene in 0.1 M tetrabutylammonium tetrafluoroborate for cyclic voltammetry and 1 mM ferricyanide/ferrocyanide (1:1) mixture in 0,1 M KCl for electrochemical impedance spectroscopy were used

Isophtalic acid terminated graphene oxide modified glassy carbon nanosensor electrode: Cd2+ and Bi3+ analysis in tap water and milk samples

In this study, graphene oxide was derivative with 5-aminoisophtalic acid by amidization reaction. The nanomaterial in suspension was denoted as graphene oxide-isophtalic acid. The graphene oxide-isophtalic acid suspension was covered on the glassy carbon electrode surface under the infrared lamb. The graphene oxide was characterized with transmission electron microscopy and x-ray diffraction. Surface characterization of the glassy carbon/graphene oxide-isophtalic acid was performed with x-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The ultrasensitive nanoplatform for the simultaneous electrochemical square-wave anodic stripping voltammetry assay of Bi3+ and Cd2+ in aqueous solution has been developed on the glassy carbon/graphene oxide-isophtalic acid. The linearity range of Bi3+ and Cd2+ were 1.0x10(-8) - 1.0x10(-12) M (S/N = 3). The responses of species were practically unaltered with the increase of various species concentration. The detection limits of Cd2+ and Bi3+ were determined as 8.1x10(-13) M and 1.06x10(-13) M, respectively. The electrode performance was checked with tap water and commercially milk samples

Carbonaceous Materials-12: a Novel Highly Sensitive Graphene Oxide-Based Carbon Electrode: Preparation, Characterization, and Heavy Metal Analysis in Food Samples

Graphene oxide (GO) was covalently attached to glassy carbon (GC) electrode (GC-O-GO) for fabricating nanosensors to determine trace Pb2+ and Cd2+ using differential pulse anodic stripping voltammetry (DPASV). Surface characterization of the nanofilm-covered electrode was performed via electrochemical cyclic voltammetry (CV), transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) techniques. Surface pKa of the GO covalent attached GC (GC-O-GO) was calculated via CV. Under optimal conditions, a linear response was found for Pb2+ and Cd2+ in the range from 1 x 10(-8) to 1 x 10(-12) M. The limit of detections (LODs) of Pb2+ and Cd2+ were 0.25 pM and 0.28 pM, respectively. The method shows good reproducibility, and stability was successfully applied to measure Pb2+ and Cd2+ levels in rice, soya, milk, and tap water samples, with good agreement with those obtained by the standard inductively coupled plasma optical emission spectrometry (ICP-OES) method. The method was evaluated by application with the simultaneous determination of the ions in food samples (n = 6) using the standard addition method. The recoveries of the Pb2+ and Cd2+ were up to 98 %