Biomedical subjects

A I Gasco-Lopez

Publications and source records attributed to A I Gasco-Lopez.

6 recordsLinked to original sources

PubMed2000

High-performance liquid chromatographic separation of a complex mixture of diuretics using a micellar mobile phase of sodium dodecyl sulphate. Application to human urine samples.

A systematic optimization of the HPLC separation of a complex mixture containing 19 diuretics by micellar liquid chromatography using sodium dodecyl sulphate (SDS), a Hypersil (150 mmx3.0 mm I.D., 5 microm) C18 column, a flow-rate of 0.5 ml min(-1) and UV absorbance detection has been carried out. Several mobile phases consisting of SDS and organic modifiers such as acetonitrile, tetrahydrofuran, propanol, butanol or pentanol, and the pH adjusted to 3.2, were tested. The effect of the organic modifier and SDS concentration on the retention behavior and separation of the diuretics was investigated. A mobile phase containing 40 mM SDS and 4% tetrahydrofuran was finally selected. Under these conditions, 14 out of 19 diuretics were separated in about 31 min. A bivariant optimization method for the mobile phase SDS-tetrahydrofuran corroborated the above results. The effect of temperature on the retention was also studied, and 50 degrees C was selected. The optimized method was applied to human urine samples of subjects administered Diurex (tablets containing 20 mg of the active ingredient xipamide) without sample preparation.

Calibration↗

PubMed1999

LC method development for ibuprophen and validation in different pharmaceuticals.

An isocratic LC method for the simultaneous determination of ibuprophen (IBU) and its degradation product (4-isobutylacetophenone) has been developed and validated for different pharmaceuticals (sachets, tablets and gels). The chromatographic separation was achieved with phosphoric acid solution (pH 3.2)-acetonitrile (50:50, v/v) as mobile phase, a Hypersil C18 column and UV detection at 254 nm. In all cases, sample preparation was required before HPLC analysis.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1997

Development and validation of a high-performance liquid chromatography method for the determination of cold relief ingredients in chewing gum.

An isocratic high-performance liquid chromatography (HPLC) method for the simultaneous determination of the active compounds paracetamol, pseudoephedrine and chlorpheniramine in chewing gum samples has been developed and validated. The method required a simple liquid-liquid extraction using n-hexane and a mixture of water-acetonitrile prior to HPLC analysis. The chromatographic separation was achieved with an aqueous solution containing hexylamine (pH 3)-acetonitrile as the mobile phase, a Spherisorb C18 column and UV detection at 220 nm. As an application, the proposed method has been used to evaluate the release into saliva of these compounds from samples under a controlled human chewing process.

Acetaminophen↗

PubMed1994

Extraction and high-performance liquid chromatographic separation of deflazacort and its metabolite 21-hydroxydeflazacort. Application to urine samples.

Two HPLC methods for the separation of a mixture of corticoids including the oxazolinic corticoid deflazacort and its metabolite 21-hydroxydeflazacort using different water-tetrahydrofuran mobile phases were developed. Both separations allowed the detection and determination of fifteen out of sixteen corticoids using different C18 columns. Extraction data for deflazacort and its metabolite using different extraction procedures are also reported. These separation conditions were applied to urine samples from two male volunteers administered Dezacor, with both doping control and clinical purposes.

Adrenal Cortex Hormones↗

PubMed1994

Solvent and solid-phase extraction of natural and synthetic corticoids in human urine.

Optimization of the main variables that affect solvent and solid-phase extraction processes, using disposable C18 cartridges and the non-ionic polymeric resin Serdolit AD-2, of human urine containing natural and synthetic corticoids is described. The data were obtained from different HPLC separations of these compounds using calibration graphs obtained before and after extraction of these compounds. The procedures, including sample preconcentration, showed efficiencies over 90%. NaCl was used to avoid emulsion formation in solvent extraction. The results achieved using solvent and solid-phase extraction are discussed.

Adrenal Cortex Hormones↗

PubMed1993

Optimization of the high-performance liquid chromatrographic separation of a mixture of natural and synthetic corticosteroids.

Systematic optimization of the HPLC separation of a mixture of natural and synthetic corticosteroids was carried out for screening purposes. The method involves binary, ternary or quaternary mixtures containing water, methanol, acetonitrile and tetrahydrofuran. It was possible to separate thirteen out of fourteen corticosteroids contained in a sample in about 26 min, with a 5-microns Hypersil-C18 (250 mm x 4.6 mm I.D.) column thermostated at 30 degrees C, using a mobile phase composed of water-tetrahydrofuran (72:28, v/v). This separation was not improved using other C8 or C18 columns. The effect of temperature on the separation of these compounds was also studied. Calibration graphs were established for each corticosteroid up to 8 micrograms/ml using indapamide as internal standard. The detection limits were in the range 0.02-0.14 ng. The optimized method was applied to urine samples spiked with corticosteroids and showed potential for future applications.

Acetonitriles↗