Development of a Dy2O3@Eu2O3-carbon nanofiber based electrode for highly sensitive detection of papaverine.

A sensitive electrochemical method based on carbon nanofibers (CNFs) and bimetallic nanoparticles of dysprosium oxide (Dy2O3) and europium oxide (Eu2O3) was developed for the determination of papaverine in pharmaceuticals and human urine. Several electrodes were compared in respect to their electrochemically active surface area calculated as 0.0603, 0.1300, 0.3440, 0.3740 and 0.4990 cm2 for bare GCE, CNFs/GCE, Eu2O3-CNFs/GCE, Dy2O3-CNFs/GCE and Dy2O3@Eu2O3-CNFs/GCE, respectively. Electrodes were also compared in respect to their performance towards the voltammetric process of papaverine. The peak potential (Epa) of papaverine was 1.094 V, 0.993 V, 0.978 V, 0.969 V and 0.966 V at unmodified GCE, CNFs/GCE, Eu2O3-CNFs/GCE, Dy2O3-CNFs/GCE and Dy2O3@Eu2O3-CNFs/GCE, respectively. This indicated that the oxidation peak potential of papaverine shifted gradually towards the negative potentials and the peak current increased gradually from unmodified GCE to CNFs/GCE, Eu2O3-CNFs/GCE, Dy2O3-CNFs/GCE and Dy2O3@Eu2O3-CNFs/GCE. The influence of experimental parameters such as scan rate and pH on the voltammetry of papaverine was studied. The Dy2O3@Eu2O3-CNFs/GCE system presented a dynamic working range between 1.0 × 10-7 and 2.0 × 10-6 M with a detection limit of 1.0 × 10-8 M for papaverine. The platform (Dy2O3@Eu2O3-CNFs/GCE) exhibited excellent sensitivity and selectivity for papaverine in the presence of uric acid and was successfully applied for determining papaverine in pharmaceuticals and urine samples.

A novel electrochemical platform based on carbon nanofibers and tri-metallic nanoparticles of gold, nickel and cobalt for the quantification of ethyl paraben.

A composite of carbon nanofibers (CNFs) and tri-metallic nanoparticles of gold, cobalt and nickel were used for the preparation of a novel voltammetric platform. The proposed voltammetric platform was utilized for quantifying ethyl paraben (EPB) in pharmaceutical and cosmetic products. The electrode layers were characterized by utilizing X-ray diffraction method (XRD) and Fourier transform infrared spectroscopy (FTIR). The electrode system, (Au-Ni-Co)NPs-CNFs/GCE, exhibited high catalytic activity and enhanced the electrochemical behaviour of EPB compared with several other electrodes. The proposed composite layer based electrode produced a well-defined oxidation peak at 0.760V. The determination of EPB was carried out by square wave voltammetry (SWV). The electrode produced a linear plot with a concentration range from 1.0×10-9 to 1.0×10-7M at (Au-Ni-Co)NPs-CNFs/GCE. The composite material enabled a detection limit of 3.5×10-10M for EPB. Good reproducibility, high precision and excellent accuracy for EPB were obtained at (Au-Ni-Co)NPs-CNFs/GCE. The composite layer based platform was successfully applied for the quantification of EPB in pharmaceutical and cosmetic products. The sensitive quantification of EPB is of great importance for the public health care. Furthermore, data show that EPB binds to DNA via intercalation with a binding constant of 2.51(±0.40)×104.

A sensitive determination of terbutaline in pharmaceuticals and urine samples using a composite electrode based on zirconium oxide nanoparticles.

An accurate and precise determination of terbutaline has been carried out using a glassy carbon electrode (GCE) modified with a composite of multi-walled carbon nanotubes (MWCNTs) and nanoparticles of zirconium oxide (ZrO2NPs). Energy dispersive X-ray and scanning electron microscopic techniques were utilized for the characterization of the composite layer. Terbutaline exhibited a broad oxidation peak at 770mV on a GCE. However, MWCNTs/GCE presented an electrocatalytic effect toward the oxidation of terbutaline with a better anodic peak at 660mV. Furthermore, the electrochemical behavior of terbutaline has greatly been improved at a GCE modified with a composite of MWCNTs and nanoparticles of ZrO2. The ZrO2NPs/MWCNTs/GCE exhibited a sharp anodic wave at 645mV with a large enhancement of the current response for terbutaline. Square wave voltammetry (SWV) was performed for the determination of terbutaline at ZrO2NPs/MWCNTs/GCE. A linear plot was obtained for the current responses of terbutaline against concentrations in the range of 10-160nM yielding a detection limit of 2.25nM (based on 3Sb/m). Improved voltammetric behavior, long-time stability and good reproducibility were obtained for terbutaline at the proposed electrode. A mean recovery of 101.2% with an RSD% of 1.9 was obtained for the analysis of the drug formulation. The accurate and precise quantification of terbutaline makes the ZrO2NPs/MWCNTs/GCE system of great interest for monitoring its therapeutic use.

A composite material based on nanoparticles of yttrium (III) oxide for the selective and sensitive electrochemical determination of acetaminophen.

An electrochemical sensor was prepared by modifying a glassy carbon electrode (GCE) with a composite of yttrium (III) oxide nanoparticles (Y2O3NPs) and carbon nanotubes (CNTs) for the determination of acetaminophen (ACT). Compared with a bare GCE and CNTs/GCE, the Y2O3NPs/CNTs/GCE exhibited a well-defined redox couple for ACT and highly enhanced the current response. The separations in the anodic and cathodic peak potentials (ΔEp) for ACT were 552mV, 24mV and 10mV at ba4re GCE, CNTs/GCE and Y2O3NPs/CNTs/GCE, respectively. The observation of only 10mV of ΔEp for ACT at Y2O3NPs/CNTs/GCE was a clear indication of a great acceleration of the electrode process compared to bare GCE and GCE modified with CNTs. Also, l-ascorbic acid (l-AA) and l-tyrosine (l-TRY) did not interfere with the selective determination of ACT. Square wave voltammetry (SWV) was performed for the quantification of ACT. A linear plot was obtained for current responses versus the concentrations of ACT over the range from 1.0×10(-10) to 1.8×10(-8)M with a detection limit of 3.0×10(-11)M (based on 3Sb/m). The proposed composite material provided high electrocatalytic activity, improved voltammetric behavior, good selectivity and good reproducibility. The accurate quantification of ACT makes the proposed electrode of great interest for the public health.

A novel voltammetric sensor based on carbon nanotubes and nanoparticles of antimony tin oxide for the determination of ractopamine.

An electrochemical sensor was prepared by the modification of a glassy carbon electrode (GCE) with carbon nanotubes (CNTs) and nanoparticles of antimony tin oxide (ATO). The surface layer was characterized by scanning electronmicroscopy (SEM), energy dispersive X-ray diffraction method (EDX) and ATR FT-IR spectroscopy. The proposed electrode was assessed in respect to the electro-oxidation of ractopamine. Compared with a bare GCE and a GCE electrode modified with CNTs, the ATONPs/CNTs/GCE exhibited a great catalytic activity towards the oxidation of ractopamine with a well-defined anodic peak at 600 mV. The current response was linear with the concentration of ractopamine over the range from 10 to 240 nM with a detection limit of 3.3 nM. The proposed electrode enabled the selective determination of ractopamine in the presence of high concentrations of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The proposed electrode was successfully applied for the determination of ractopamine in feed and urine samples. The sensitive and selective determination of ractopamine makes the developed method of great interest for monitoring its therapeutic use and doping control purposes.

A novel composite electrode based on tungsten oxide nanoparticles and carbon nanotubes for the electrochemical determination of paracetamol.

An electrochemical sensor was prepared by the modification of a glassy carbon electrode (GCE) with a composite of nanoparticles of tungsten oxide (WO3) and carbon nanotubes (CNTs) for the quantification of paracetamol (PR). Energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) were performed for the characterization of the nanocomposite layer. Compared with a bare GCE and a GCE modified with CNTs, the proposed electrode (WO3NPs/CNTs/GCE) exhibited a well-defined redox couple for PR and a marked enhancement of the current response. The experimental results also showed that ascorbic acid (AA) did not interfere with the selective determination of PR. The proposed electrode was used for the determination of PR in 0.1M phosphate buffer solution (PBS) at pH7.0 using square wave voltammetry (SWV). The peak current increased linearly with the concentration of PR in the range of 1.0×10(-9)-2.0×10(-7)M. The detection limit (LOD) was 5.54×10(-11)M (based on 3Sb/m). The proposed voltammetric sensor provided long-time stability, improved voltammetric behavior and good reproducibility for PR. The selective, accurate and precise determination of PR makes the proposed electrode of great interest for monitoring its therapeutic use.