Template synthesis of maghemite nanoparticle in carboxymethyl cellulose and its application for electrochemical cabergoline sensing.

Maghemite (γ-Fe2O3) nanoparticles were produced via coprecipitation onto carboxymethyl cellulose matrix based templates followed by calcination. The resulting maghemite nanoparticles were characterized by Fourier transform infrared spectra, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The magnetization measurement of as-synthesized γ-Fe2O3 displayed superparamagnetic characteristics at room temperature. Then, a novel maghemite nanoparticles carbon paste modified electrode was developed for determination of cabergoline. The modified electrode has an outstanding catalytic effect on the oxidation current of cabergoline and the mechanism was studied using cyclic voltammetry. The oxidation peak current was proportional to the concentration of cabergoline from 1×10-7 to 3.5×10-5molL-1 with a detection limit of 3×10-8molL-1 at signal to noise ratio of 3. The proposed method was examined as a selective, simple and precise method for voltammetric determination of cabergoline in plasma and pharmaceutical samples.

Simultaneous determination of ascorbic acid, acetaminophen and codeine based on multi-walled carbon nanotubes modified with magnetic nanoparticles paste electrode.

Based on incorporating ZnCrFeO4 into multi-walled carbon nanotubes paste matrix (MWCNTs/ZnCrFeO4/CPE), a chemically modified electrode was prepared for the simultaneous determination of ascorbic acid (AA), acetaminophen (AC) and codeine (CO). The prepared electrode, MWCNTs/ZnCrFeO4/CPE, was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The MWCNTs/ZnCrFeO4/CPE showed an efficient electrocatalytic activity for the oxidation of AA, AC, and CO. The separations of the oxidation peak potentials for AA-AC and AC-CO were about 250mV and 630mV, respectively. The calibration curves obtained for AA, AC, and CO were in the ranges of 0.4-730.0µmolL(-1), 0.1-368.0µmolL(-1), and 0.3-250.0µmolL(-1), respectively. The detection limits (S/N=3) were 0.03µmolL(-1), 0.009µmolL(-1), and 0.01µmolL(-1) for AA, AC, and CO, respectively. The method was also successfully employed as a selective, simple, and precise method to determinate AA, AC, and CO in pharmaceutical and biological samples.

Simultaneous determination of cysteine, uric acid and tyrosine using Au-nanoparticles/poly(E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol film modified glassy carbon electrode.

A novel Au nanoparticles/poly(E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol (AuNPs/PTAT) film modified glassy carbon electrode (AuNPs/PTAT/GCE) was fabricated for the simultaneous determination of three antioxidants named, cysteine (Cys), uric acid (UA) and tyrosine (Tyr). The bare glassy carbon electrode (GCE) fails to separate the oxidation peak potentials of these molecules, while PTAT film modified electrode can resolve them. Electrochemical impedance spectroscopy (EIS) study indicates that the charge transfer resistance of bare electrode increased as (E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol was electropolymerized at the bare electrode. Furthermore, EIS exhibits enhancement of electron transfer kinetics between analytes and electrode after electrodeposition of Au nanoparticles. Differential pulse voltammetry results show that the electrocatalytic current increases linearly in the ranges of 2-540µmolL(-1) for Cys, 5-820µmolL(-1) for UA and 10-560µmolL(-1) for Tyr with detection limits (S/N=3) of 0.04µmolL(-1), 0.1µmolL(-1) and 2µmolL(-1) for Cys, UA and Tyr, respectively. The proposed method was successfully applied for simultaneous determination of Cys, UA and Tyr in human urine samples.

Highly Selective Electrochemical Determination of Taxol Based on ds-DNA-Modified Pencil Electrode.

In this research, TiO2/ZrO2 nanocomposite has been prepared using sol-gel method. The TiO2/ZrO2 composite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). A sensitive electrochemical biosensor is also presented for the determination of Taxol based on ds-DNA decorated multiwall carbon nanotubes-TiO2/ZrO2-chitosan-modified pencil electrode (ds-DNA-MWNTs-TiO2/ZrO2-CHIT-PGE). The UV spectroscopic data and differential pulse voltammetry revealed that there is a strong interaction between ds-DNA and Taxol. The groove binding of Taxol to ds-DNA helix has been characterized by a red shift (less than 8 nm) in wavelength and the decrease in the differential pulse voltammetry oxidation signal intensity of the Taxol at pencil graphite electrode (PGE) after its interaction with ds-DNA. Finally, a pretreated PGE modified with ds-DNA-MWNTs-TiO2/ZrO2-CHIT was tested in order to determine Taxol content in the solution. The dynamic range was from 0.7 to 1874.0 nmol L(-1) with a detection limit of 0.01 nmol L(-1). This sensing platform was successfully applied for the determination of Taxol in pharmaceutical and biological samples.

Simultaneous determination of norepinephrine, acetaminophen and tyrosine by differential pulse voltammetry using Au-nanoparticles/poly(2-amino-2-hydroxymethyl-propane-1,3-diol) film modified glassy carbon electrode.

A novel Au-nanoparticles/poly-(2-amino-2-hydroxymethyl-propane-1,3-diol) film modified glassy carbon electrode (AuNPs/poly(trisamine)/GCE) was constructed for the simultaneous determination of norepinephrine (NE), acetaminophen (AC) and L-tyrosine (Tyr) by differential pulse voltammetry. Electrochemical impedance spectroscopy and scanning electron microscopy indicate that the trisamine film was successfully polymerized on the surface of GCE and the film efficiently decreased the charge transfer resistance value of electrode and improved the electron transfer kinetic between analytes and electrode. The separation of the oxidation peak potentials for NE-AC and AC-Tyr were about 160 mV and 240 mV, respectively. The calibration curves for NE, AC and Tyr were obtained in the range of 1.3-230.1 µmol L(-1), 1.90-188.0 µmol L(-1), and 3.9-61.8 µmol L(-1), respectively. The detection limits (S/N=3) were 0.07 µmol L(-1), 0.1 µmol L(-1) and 0.9 µmol L(-1), for NE, AC and Tyr, respectively. The diffusion coefficient and the catalytic rate constant for the oxidation reaction of NE at AuNPs/poly(trisamine)/GCE were calculated as 1.55 (±0.2)×10(-6) cm2 s(-1) and 2.28 (±0.17)×10(3) mol(-1) L s(-1), respectively. Finally, AuNPs/poly(trisamine)/GCE was satisfactorily used for the determination of NE, AC, and Tyr in pharmaceutical and biological samples.

Simultaneous voltammetric determination of enrofloxacin and ciprofloxacin in urine and plasma using multiwall carbon nanotubes modified glassy carbon electrode by least-squares support vector machines.

A simple and sensitive method is proposed for the electrochemical determination of enrofloxacin (ENRO) and its primary metabolite ciprofloxacin (CIPRO) at a multiwall carbon nanotubes/glassy carbon electrode (MWCNT/GCE) using a least-squares support vector machine (LS-SVM) and linear sweep voltammetry. Simultaneous determination of ENRO and CIPRO at bare glassy carbon is associated with certain difficulties due to voltammogram overlapping and their low sensitivity. The resolution of the mixture was carried out using LS-SVM as a multivariate calibration method. Under the optimum conditions at pH 7.0, the linear sweep currents increased linearly with ENRO and CIPRO concentrations in ranges of 2.0-780.0 micromol L(-1) (0.7-280.3 microg mL(-1)) and 3.0-1200 micromol L(-1) (1.0-397.7 microg mL(-1)), respectively. The detection limits for ENRO and CIPRO were 0.5 and 0.9 micromol L(-1), respectively. The proposed method was applied to simultaneously determine both compounds in human urine, plasma and in pharmaceutical samples.

Simultaneous determination of ascorbic acid, epinephrine, and uric acid by differential pulse voltammetry using poly(p-xylenolsulfonephthalein) modified glassy carbon electrode.

A novel poly(p-xylenolsulfonephthalein) modified glassy carbon electrode was prepared for the simultaneous determination of ascorbic acid (AA), epinephrine (EP) and uric acid (UA). Cyclic voltammetric, chronoamperometric, and differential pulse voltammetric methods were used to investigate the modified electrode for the electrocatalytic oxidation of EP, AA, and UA in aqueous solutions. The separation of the oxidation peak potentials for AA-EP and EP-UA was about 200 and 130 mV, respectively. The calibration curves obtained for AA, EP, and UA were in the ranges of 10-1343, 2-390, and 0.1-560 micromol L(-1), respectively. The detection limits (S/N=3) were 4, 0.1, and 0.08 micromol L(-1) for AA, EP and UA, respectively. The diffusion coefficient and the catalytic rate constant for the oxidation of EP at the modified electrode were calculated as 1.40(+/-0.10) x 10(-4) cm(2) s(-1) and 1.06 x 10(3) mol(-1) Ls(-1), respectively. The present method was applied to the determination of EP in pharmaceutical and urine samples, AA in commercially available vitamin C tablet, and EP plus UA in urine samples.

Simultaneous chemiluminescence determination of thebaine and noscapine using support vector machine regression.

In this work, a batch chemiluminescence (CL) method has been proposed for the simultaneous determination of two structurally similar alkaloids, noscapine and thebaine. The method is based on the kinetic distinction of the CL reactions of noscapine and thebaine with Ru(bipy)(3)(2+) and Ce(IV) system in a sulfuric acid medium. The least squared support vector machine (LS-SVM) regression was applied for relating the concentrations of both compounds to their CL profiles. The parameters of the model consisting of sigma(2) and gamma were optimized by constructing LS-SVM models with all possible combinations of these two parameters to select the model with the minimum root mean squared error of cross validation (RMSECV) as the best. The parameters of this model were then selected as optimized values. Under the optimized experimental conditions for both compounds, the detection limits obtained using the LS-SVM regression were 0.08 and 0.1 micromo lL(-1) for noscapine and thebaine, respectively. The proposed method was utilized for the simultaneous determination of the compounds in pharmaceutical formulations and plasma samples with satisfactory results.

Determination of ultra trace amount of enrofloxacin by adsorptive cathodic stripping voltammetry using copper(II) as an intermediate.

In this work, a simple and sensitive electroanalytical method was developed for the determination of enrofloxacin (ENRO) by adsorptive cathodic stripping voltammetry (ADSV) using Cu(II) as a suitable probe. The complex of copper(II) with ENRO was accumulated at the surface of a hanging mercury drop electrode at -0.10 V for 40 s. Then, the preconcentrated complex was reduced and the peak current was measured using square wave voltammetry (SWV). The optimization of experimental variables was conducted by experimental design and support vector machine (SVM) modeling. The model was used to find optimized values for the factors such as pH, Cu(II) concentration and accumulation potential. Under the optimized conditions, the peak current at -0.30 V is proportional to the concentration of ENRO over the range of 10.0-80.0 nmol L(-1) with a detection limit of 0.33 nmol L(-1). The influence of potential interfering substances on the determination of ENRO was examined. The method was successfully applied to determination of ENRO in plasma and pharmaceutical samples.

An Internet-based telediagnosis system for Chinese medicine.

The Internet is becoming an increasingly popular medium for communication and is being used more and more for telemedicine. Telediagnosis is one of the most developed components of telemedicine. We have designed and partly implemented a telediagnostic system, using the Internet as the means of communication, to enhance access to specialists and health providers in Chinese medicine.