Search results for " Electrokinetic"

RAPID LIQUID CHROMATOGRAPHIC DETERMINATION OF TETRACYCLINES IN ANIMAL FEEDS USING A SURFACTANT SOLUTION AS MOBILE PHASE

2002

ABSTRACT A chromatographic procedure was developed for the determination of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), doxycycline (DC) and minocycline (MINO) in animal feeds. Clear analyte-rich extracts were obtained using a 1 : 1 acetonitrile/water mixture buffered at pH 3. The extracts were injected into a conventional unprotected C18 chromatographic column and eluted with a mobile phase of 0.05 M sodium dodecyl sulfate/5% 1-butanol/0.01 M oxalic acid at pH 3. Good resolution was achieved for the five compounds, whereas OTC and TC coeluted with an optimized aqueous-organic mobile phase of methanol/acetonitrile/0.01 M oxalic acid at pH 3. Mean recoveries from spike…

Determination of synthetic antioxidants in dairy products and dietetic supplements by micellar liquid chromatography with direct sample injection

2000

A simple and rapid HPLC method for the determination of synthetic antioxidants (propyl gallate, tert-butylhydroquinone, 2,4,5-trihydroxybutyrophenone, nordihydroguaiaretic acid, octyl gallate, 3-tert-butyl-4-hydroxyanisole and dodecyl gallate) in powdered and liquid milk, cream of milk and dietetic supplements is described. The samples are diluted or solved in a micellar solution, filtered and directly injected. The retention behavior of the antioxidants on a C18 column, with micellar mobile phases containing SDS (0.05–0.15 M), n-propanol (1–9%, v/v) and 10 mM phosphate at pH 3, has been studied by using mathematical models. Retention is predicted with errors below 3%. To optimize the mobil…

Determination of furosemide in urine samples by direct injection in a micellar liquid chromatographic system.

2002

A sensitive, selective and efficient micellar liquid chromatographic (MLC) procedure was developed for the determination of furosemide (4-chloro-N-furfuryl-5-sulfamoylanthranilic acid) in urine samples by direct injection and UV detection. The procedure makes use of a C18 reversed-phase column and a micellar mobile phase of 0.05 mol l(-1) sodium dodecyl sulfate-6% v/v propanol and phosphate buffer at pH 3 to resolve furosemide from its photochemical degradation products. The importance of protecting the standards and urine samples to be analysed from light in the assay of furosemide, avoiding its degradation, was verified. The limit of quantification was 0.15 microg ml(-1) and the relative …

MICELLAR LIQUID CHROMATOGRAPHIC DETERMINATION OF ANTI-CONVULSANT DRUGS IN PILLS AND CAPSULES

2000

A simple chromatographic procedure is reported for the determination of several anti-convulsant drugs in pharmaceuticals: carbamazepine, and the benzodiazepines bentazepam, halazepam, oxazepam, pinazepam, and tetrazepam. The procedure utilizes a C18 column, a hybrid micellar mobile phase of 0.1 M SDS-3% butanol-0.1% triethylamine-0.01 M phosphate buffer (pH 3), and UV detection (230 nm). The drugs eluted in less than 13 min, in accordance to their relative polarities, as indicated by their octanol-water partition coefficients. The limits of detection (μg/mL), and intra and inter-day repeatabilities (%), for 4 μg/mL were: carbamazepine (0.03, 1.0, 4.1), bentazepam (0.05, 1.3, 1.6), halazepam…

Micellar electrokinetic capillary chromatography for therapeutic drug monitoring of carbamazepine and its main metabolites.

1998

In carbamazepine (CBZ) therapy the concomitant monitoring of concentrations of CBZ and its metabolites is strictly recommended, primarily to avoid toxic side effects. Currently, clinical routine monitoring of CBZ is accomplished by high-performance liquid chromatography or immunological methods. In this study a micellar electrokinetic capillary chromatographic (MECC) method was developed for routine drug monitoring of CBZ and its main metabolites, carbamazepine 10,11-diol and carbamazepine 10,11-epoxide, in human serum or plasma samples. The MECC method enabled baseline separation of all analytes within 2.5 min. The assay revealed sufficient precision and sensitivity and the results of eith…

Rapid in vitro test to predict ocular tissue permeability based on biopartitioning micellar chromatography.

2003

The drug permeability prediction across the ocular tissues is important in the development of new drugs and drug delivery strategies. Physicochemical characteristics of drugs, mainly acid-base character, hydrophobicity and the molecular size determine both their transport across the eye tissue barriers and their retention in biopartitioning micellar chromatography (BMC). An in vitro model able to describe and predict the whole cornea drug permeability is proposed. The model uses the retention of drugs in BMC and molecular weight (MW) as predictive variables. The relationships between drug retention data in BMC and their bibliographic permeability values in stroma, epithelium-plus-stroma and…

Electrochemical remediation of kaolin-soil contaminated by phenol: effect of several operative parameters

Electrochemical remediation technology is considered an appealing strategy for the remediation of fine- grained soils, characterized by a low hydraulic conductivity and large specific surface area, contaminated with inorganic, organic, and mixed pollutants. In both Electrokinetic (EK) and Electrochemical Geo-Oxidation (ECGO) technologies, an electric field is imposed on the contaminated soil to remove the pollutants by the combined mechanisms of electroosmosis, electromigration, and/or electrophoresis. Moreover, ECGO uses low voltage and both direct and alternating amperage (DC/AC) applied in a proprietary series to induce reduction-oxidation reactions on soil surfaces at the micro-scale. A…

Micellar electrokinetic chromatography of polyamines and monoacetylpolyamines

2001

A selective procedure for qualitative and quantitative analysis of ten polyamines by micellar electrokinetic chromatography (MEKC) was developed. Benzoylated polyamines and acetylpolyamines in micellar phase of SDS (10 mM) were separated at 25 degrees C by 20 mM borate buffer pH 8.5, containing 8% ethanol, with an applied voltage of 25 kV (5 microA) and then detected at 198 nm. The experimental factors and operational parameters were optimized by performing analysis at different surfactant concentrations, pH, voltage and temperature with and without ethanol. The repeatibility of migration times and peak heights is a peculiarity of the method here described.

Determination of urea-derived pesticides in fruits and vegetables by solid-phase preconcentration and capillary electrophoresis

2001

A multiresidue analytical method based on solid-phase extraction (SPE) enrichment combined with capillary electrophoresis (CE), using micellar electrokinetic capillary chromatography (MEKC), was developed to determine ten substituted urea pesticides in orange and tomato samples. Several factors such as pH, composition and concentration of the buffer, concentration of surfactant, addition of organic solvent, and working voltage were optimized to obtain the best compound separation in the shortest time. Separation can be achieved in 7 min using a micellar aqueous pH 9 buffer composed of 4 mM borate and 35 mM sodium dodecyl sulfate. After an SPE procedure, which provided a 10-fold enrichment, …

Comparison between sodium dodecylsulphate and cetyltrimethylammonium bromide as mobile phases in the micellar liquid chromatography determination of …

2004

The retention behaviour of non-steroidal anti-inflammatory drugs (NSAIDs) using micellar mobile phases of sodium dodecylsulphate (SDS) is studied and compared with that observed with micellar mobile phases of cetyltrimethylammonium bromide (CTAB). A liquid chromatographic procedure for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, naproxen and tolmetin in pharmaceutical preparations is described. The proposed system uses a Kromasil C18 analytical column and a solution of 0.15 M SDS at pH 3 with 10% 1-propanol as mobile phase. Under these conditions, the studied NSAIDs elute between 6 and 10 min at a 1 mL min(-1) flow rate. Limits of detection (LOD) are lower than 0.…