Electrochemical Oxidation of l-selenomethionine and Se-methylseleno-l-cysteine at a Thiol-Compound-Modified Gold Electrode: Its Application in a Flow-Through Voltammetric Sensor.

A flow-electrolytic cell that consists of a bare gold wire or of different thiol-compound-modified gold electrodes (such as 2,4-thiazolidinedione, 2-mercapto-5-thiazoline, 2-mercaptothiazoline, l-cysteine, thioglycolic acid) was designed to be used in a voltammetric detector to identify l-selenomethionine and Se-methylseleno-l-cysteine using high-performance liquid chromatography. Both l-selenomethionine and Se-methylseleno-l-cysteine are more efficiently electrochemically oxidized on a thiol/gold than on a bare gold electrode. For the DC mode, and for measurements with suitable experimental parameters, a linear concentration from 10 to 1600 ng·mL was found.

Evaluating a Cobalt-Tetraphenylporphyrin Complex, Functionalized with a Reduced Graphene Oxide Nanocomposite, for Improved Tooth Whitening.

Objectives: To study using cobalt-tetraphenylporphyrin/reduced graphene oxide (CoTPP/RGO), a nanocomposite highly catalytic both for oxidizing and for reducing hydrogen peroxide (H O ), to whiten teeth.

Methods: Dyes (D&C Red 34, Orange No. 4), tea, and betel nuts (Areca catechu) were used to stain the tooth specimens for three days and subsequently bleached using H O alone, H O plus CoTPP, or H O plus CoTPP/RGO for 0.

Electrochemical oxidation of cysteine at a film gold modified carbon fiber microelectrode its application in a flow-through voltammetric sensor.

A flow-electrolytical cell containing a strand of micro Au modified carbon fiber electrodes (CFE) has been designedand characterized for use in a voltammatric detector for detecting cysteine using high-performance liquid chromatography. Cysteine is more efficiently electrochemical oxidized on a Au /CFE than a bare gold and carbon fiber electrode. The possible reaction mechanism of the oxidation process is described from the relations to scan rate, peak potentials and currents.

Studies on the electrochemical behavior of thiazolidine and its applications using a flow-through chronoamperometric sensor based on a gold electrode.

The electrochemical behaviors of thiazolidine (tetrahydrothiazole) on gold and platinum electrodes were investigated in a Britton-Robinson buffer (pH 2.77-11.61), acetate buffer (pH 4.

Design of a flow-through voltammetric sensor based on an antimony-modified silver electrode for determining lithol rubine B in cosmetics.

Lithol Rubine B (LRB; the disodium salt of 3-hydroxy-4-[(4-methyl-2-sulfophenyl) azo]-2-naphthalenecarboxylic acid) was detected using high-performance liquid chromatography with an electrochemical (antimony film on silver) detector (HPLC-ECD). For direct current (DC) mode, with the current at a constant potential, and measurements with suitable experimental parameters, a linear concentration from 0.125 to 1.

Study of the aerosol fragrances of eugenol derivatives in Cananga odorata using diffuse reflectance infrared Fourier transform spectroscopy and gas chromatography.

The purpose of this study was to develop and test a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) method, a fast and non-destructive method without extraction, and compare it with the standard gas chromatography (GC) method currently used. A micro-orifice uniform deposit impactor (MOUDI) was used to sample all the size distributions of the aerosol particles of essential oils to investigate the relation between size distributions and the indoor concentration distributions of ylang essential oils. Correlation coefficients for DRIFTS and GC were 0.

Electrochemical reduction of coumarins at a film-modified electrode and determination of their levels in essential oils and traditional Chinese herbal medicines.

The electrochemical reduction of coumarins on glassy carbon and electrodeposited metal electrodes was investigated in a Britton-Robinson buffer (pH 1.87-11.98).

Determining urinary trace elements (Cu, Zn, Pb, As, and Se) in patients with bladder cancer.

Objectives: Trace elements are essential components of biological structures, but they can be toxic at concentrations beyond those necessary for their biological functions.

Methods: A study group of 30 patients with bladder cancer and a control group of 30 healthy volunteers were measured for trace elements using a graphite furnace atomic absorption spectrophotometer.

Results: Urinary zinc and selenium levels in patients were significantly (P < 0.

Vehicle and enhancer effects on human skin penetration of aminophylline from cream formulations: evaluation in vivo.

The effects of four essential oils (rosemary, ylang, lilacin, and peppermint oils), and three plant oils (jojoba oil, corn germ oil, and olive oil) on the permeation of aminophylline were studied using human skin. The permeation effects of these oils were compared with those of three chemical penetration enhancers. Although all oils enhanced the permeation of aminophylline, their effects were less than that of ethanol.

Simultaneous determination of p-aminobenzoic acid and its metabolites in the urine of volunteers, treated with p-aminobenzoic acid sunscreen formulation.

p-Aminobenzoic acid (PABA) and its metabolites (p-aminohippuric acid, p-acetamidobenzoic acid, and p-acetamidohippuric acid) were detected using high-performance liquid chromatography with an electrochemical (carbon paste) detector (HPLC-ECD). For direct current (dc) mode, with the current at a constant potential, and measurements with suitable experimental parameters, a linear concentration from 0.125 to 1.

Simultaneous determination of urinary metabolites of methoxypsoralens in human and Umbelliferae medicines by high-performance liquid chromatography.

A high-performance liquid chromatography method has been developed for the determination of coumarins and furocoumarins (psoralens). Nine coumarins and furocoumarins are separated simultaneously on a Hypersil C(8) (25 cm x 4.6-mm i.

Simultaneous determination of chlorinated bacteriostats in cosmetic and pharmaceutical products.

A high-performance liquid chromatography method has been developed for simultaneous determination of triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether) and triclocarban (3,4,4'-trichlorocarbanilide) in cosmetic and pharmaceutical products. The two compounds could be separated on a Nucleosil C(18) column and eluted with acetonitrile and water (70:30, v/v) as the mobile phase and detected with a differential refractive index detector. The retention times of triclosan and triclocarban were 5.

Simultaneous determination of oxidative hair dye p-phenylenediamine and its metabolites in human and rabbit biological fluids.

A liquid chromatography with an electrochemical detector method has been developed for the quantitative measurement for three diamine derivatives (p-phenylenediamine, N,N(')-p-phenylenebisacetamide, and 4-aminoacetanilide) in human urine and rabbit blood, urine, and feces. The detection cell consisted of a glassy carbon electrochemical signal obtained with a supporting electrolyte containing 20% methanol-5mM octylammonium orthophosphate (pH 6.30) as the mobile phase.

Determination of 5-methoxypsoralen in human serum.

A high performance liquid chromatography with fluorometric and ultraviolet detection described to quantify 5-methoxypsoralen (5-MOP) percutaneous absorption in humans after the application of an essential oil, as well as 5-MOP in bergamot oil and cosmetics by fluorometric and voltammetric measurement, respectively. A muBondapack C(18) analytical column (particle size 5 microm, 3.9 x 300 mm) eluted with acetonitrile-tetrahydrofuran-water (70:15:15, v/v/v) containing 0.

Ion chromatography studies of quaternary ammonium halide solutions and the determination of pharmaceuticals.

The feasibility of using ion chromatography (IC) in solutions containing quaternary ammoniums is studied. The results establish the applicability of IC for the determination of halide ions in a pharmaceutical sample without interferences by various excipient ions. For IC measurements with suitable methodical parameters, linearity is maintained over the range of 20 to 200 mg/L and 10.