Analytical & Bioanalytical Electrochemistry
Volume:10 Issue: 11, Nov 2018

NiFe2O4 nanoparticles were successfully applied at a screen printed electrode (NiFe2O4/SPE). At first, NiFe2O4 nanoparticles were deposited on the SPE. This new modified electrode system was characterized by cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV). NiFe2O4/SPE was used for simultaneous determination of serotonin and norepinephrine. It was observed that an electrode with electrochemical deposited of NiFe2O4 nanoparticles has higher electrocatalytic activity for the oxidation of serotonin. Differential pulse voltammetry exhibited a linear dynamic range over the concentration range of 0.1-300.0 μM and a detection limit (3σ) of 0.07 μM for serotonin in the optimum conditions. Finally, DPV was used for simultaneous determination of serotonin and norepinephrine and their detection real samples.

A novel vildagliptin selective electrode has been investigated using tetrakis (p-chlorophenyl) borate as cation exchanger in polymeric matrix of polyvinyl chloride plasticized with orth-nitro phenyl octyl ether. The proposed sensor was fabricated using hydroxy propyl β-cyclodextrin as ionophore and compared to ionophore free sensor. A stable and reliable response of vildagliptin within the concentration range of 1×10-1to1×10-4 mol.L-1 was obtained on using ionophore based sensor with detection limit down to 5×10-6 mol.L-1. Nernstian slope was 55.3 mV/decade over in aqueous medium (pH 7) was observed with fast response time. The selectivity coefficients calculated for L-proline as in-process impurity and different inorganic cations indicated excellent selectivity for vildagliptin. Hydroxy propyl βcyclodextrin sensor displayed useful analytical characteristics for the determination of vildagliptin. The fabricated ionophore based sensor was validated and found to be accurate and precise compared with the manufacturer’s gradient HPLC method. Moreover, this potentiometric has advantage over previously published methods where no sample pretreatment is required.

In this work, PEI and PVC grafted Ni doped superparamagnetic iron oxide (i.e. PEI/Ni-SPIOs and PVC/Ni-SPIOs) were synthesized on steel sheet though galvanostatic (constant current) deposition mode. Structural and morphological properties of the fabricated PEI/Ni-SPIOs and PVC/Ni-SPIOs samples were studied and the results indicated the successful synthesis of polymer grafted iron oxide nanoparticles. The size of prepared particles was about 20 nm. Thermogravimetric data showed 7.2 wt % PEI and 6 wt % PVC coated onto the surface of Ni-SPIOs particles. The magnetite crystal phase of samples was proved via XRD and IR data. In addition, the obtained results from vibrating sample magnetometer analysis showed that the fabricated samples exhibit low residual magnetization values (i.e. Mr=0.95 and Mr=0.53 emu/g, respectively, for PVC and PEI grafted Ni-SPIOs), which revealed their suitability for biomedical uses.

Diacerein was used for the modification of carbon paste electrode (CPE) to determine the electrochemical behavior of paracetamol (PA) in 0.2 M phosphate buffer solution (PBS) at pH 7. The effect of concentration, scan rate, pH and surfactant was studied for electrochemical studies of paracetamol. The Diacerein modified carbon paste electrode showed an excellent electrocatalytic activity for the selective determination of PA in the presence of Dopamine and Diclofenac by using CV and differential pulse voltammetric techniques (DPV) respectively. The catalytic peak current obtained was linearly related to PA concentrations in the ranges of to 0.1 mM to 0.6 mM with correlation co-efficient of 0.9981 which reveals the adsorption controlled process. The detection limit of paracetamol was found to be 3.8×10−6 M. The present technique provides a novel method for the simultaneous determination of Paracetamol, Dopamine and Diclofenac in their mixture sample.

Magnetic particles i.e. Fe3O4 nanoparticles have received great attention because of their potential biomedical applications like as MRI contrast agent, hyperthermia and biosensing magnetic labels. For these biomedical applications, Fe3O4 nanoparticles particles must have proper surface coatings and also acquire superparamagnetic properties with relatively high Ms values. Here, we performed Gd doping of iron oxide particles and their in situ surface modification through an electrochemical strategy. The prepared particles were examined using XRD, IR, TG, FE-SEM and EDAX analyses and their covering with starch and doping by Gd cations were approved. VSM data further proved the superparamagnetic behavior of the electrosynthesized iron oxide particles.

The possibility of Insubosin electrochemical determination, assisted by CoO(OH) – Poly(3,4-ethylendioxythiophene) hybrid material has been evaluated. The correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It was shown that the hybrid material may be applied as an efficient electrode modifier in the detection of Insubosin as sodium salt in neutral and lightly alkaline media. The electrochemical response has to be clear and easy to interpret. The possibility of the oscillatory and monotonic instabilities has also been verified.

Risperidone (RSP) is an antipsychotic medication commonly used in the treatment of schizophrenia, schizoaffective and some forms of bipolar disorder. A novel RSP all-solidstate potentiometric membrane electrode (ASS-PME) was introduced for assay of risperidone active ingredient in dosage forms. The ASS-PME was made of a copper wire coated with a layer of conductive graphite-epoxy resin, a layer of carbon dots and finally a PVC sensing layer. The PVC layer was composed of 30% of PVC, 61% of dibutylphthalate (DBP) as solvent mediator, 2% of an ionic additive (sodium tetraphenyl borate (NaTPB)) and 7% of an ion-pair of RSP-TPB as a sensing material. The device worked well under laboratory condition and showed a Nernstian response of 58.2±0.4 mV/decade from 1.0×10-7 M to 1.0×10-3 M of the analyte with lower detection limit of 8.3×10-8 M. The ASS-PME has excellent selectivity toward RIS in presence of excipients in its pharmaceutical dosage forms.

A highly sensitive electrochemical sensor for Indigotine (IG) detection was fabricated at a carbon paste electrode (CPE) modified with TX-100 surfactant. The electrochemical behavior of IG was studied at TX-100 modified carbon paste electrode (TX100MCPE). The effect of different pH values, scan rate and effect of concentration was also studied using cyclic voltammetry. It was noticed that under optimized condition (pH 6.5) a well -defined redox peak with the higher current response was obtained for IG at TX100MCPE compare to bare carbon paste electrode (BCPE). The modified electrode exhibited an excellent electrochemical activity towards the oxidation of IG. The electrochemical response of IG is linearly observed in the range of 1.5×10-6 M to 2×10-5 M, with the detection limit and limit of quantification of 16×10-8 M and 5.3×10-7 M. The modified electrode showed good sensitivity (0.085 µA/µM) and stability and was employed for the determination of IG in the real sample.

Optimization single factor for the simultaneous determination of Cd, Cu, Cr, and Pb in water samples by adsorptive stripping voltammetry (AdSV) has been investigated. In preliminary studies, it has been proven that the Cd, Cu, Cr, and Pb react with fluorexon, giving rise to the formation of these complexes. Variable factors that affect the response were studied: fluorexon concentration, pH, potential accumulation and time accumulation. The optimum conditions of the AdSV-fluorexon method were: fluorexon concentration 0.6 mmol/L, pH 6, potential accumulation -0.7 V, and time accumulation 70 s. The relative standard deviations (RSD) were (0.46; 0.11; 2.39, and 0.90)% for ten replicates(n=10) measurements of 10 μg/L, recovery were (99.11; 99.88; 98.12, and 98.76)%, the linear calibration graph were (10.0-100.0) µg/L, the limit of detection (LOD) were (0.590; 1.794; 1.235, and 1.595) µg/L for Cd, Cu, Cr, and Pb. This procedure was successfully applied for the simultaneous determination of Cd, Cu, Cr, and Pb in the water (sea water, tap water, lake water and river water) with standard addition method.

Corrosion inhibition of mild steel in 1 M hydrochloric acid by water, hexane and ethanol extracts of Pimpinella Anisum plant were study using weight loss and Tafel polarization curves. The effects of temperature on the corrosion behavior of mild steel in 1M hydrochloric acid with addition of extracts were also studied. The inhibition efficiency (IE) increases with increasing concentration of Pimpinella Anisum extracts but decreases with increasing the temperature. The adsorption of the extracts on the surface of metal follows a Langmuir isotherm model. Polarization studies show that the extracts behave as mixed type inhibitors. Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) study confirmed that the inhibition of corrosion of mild steel is through adsorption of the extracts molecules on the surface of metal. Gas chromatography-mass spectroscopy (GC-MS) results showed that anethole was the major compound of both Yemeni and Moroccan Pimpinella Anisum plant.