Biomedical subjects

Josep Esteve-Romero

Publications and source records attributed to Josep Esteve-Romero.

13 recordsLinked to original sources

PubMed2006

Optimization of a capillary zone electrophoresis method by using a central composite factorial design for the determination of codeine and paracetamol in pharmaceuticals.

Capillary zone electrophoresis was optimized to quantitatively determine codeine and paracetamol via central composite factorial design. Critical parameters (concentration, buffer, pH, voltage) assessed effects on resolution, analysis time and efficiencies. Optimum separation conditions were achieved using phosphate buffer 20 mM (pH 6.8) and voltage (15 kV). The optimized procedure easily determined codeine and paracetamol with separation in less than 3 min. Calibration curves (R > 0.999) were prepared, with LODs of 13.5 and 340 ng mL(-1) for codeine and paracetamol, respectively, and a good R.S.D.% (<3%). This method was applied to determine codeine and paracetamol in pharmaceutical formulations; recoveries coincided with stated contents.

Acetaminophen↗

PubMed2006

Solute-solvent interactions in micellar liquid chromatography. Characterization of hybrid micellar systems of sodium dodecyl sulfate-pentanol.

The solvation parameter model has been applied to the characterization of hybrid micellar chromatographic systems with mixtures of sodium dodecyl sulfate (SDS) and pentanol as mobile phases. Retention factors for 22 compounds in two groups, phenethylamines and antihistamines, were used for the characterization of the systems after the calculation of their Abraham descriptors. Three equations were developed as multiple linear regressions using Abraham descriptors and properties, such as log Poct and polar surface area to correlate the retention factors. A group of 30 data points was used as an independent test set to assess the predictive capability of the equations. Micellar chromatographic systems were compared against other separation systems using principal components analysis. Conventional RPLC chromatography using mobile phases with high amounts of organic solvents are close to the micellar mobile phases that only use small amounts of alcohol.

Chromatography, Liquid↗

PubMed2006

Optimization by factorial design of a capillary zone electrophoresis method for the simultaneous separation of antihistamines.

A 3(2) full factorial design was used to optimize the experimental conditions of a capillary zone electrophoresis method aimed at achieving simultaneous separation and quantification of the antihistamines brompheniramine, chlorpheniramine, cyproheptadine, diphenhydramine, doxylamine, hydroxyzine, and loratadine according to their therapeutic group. A statistical program, SPSS, was used to calculate the mathematical model with which to obtain the response surface. Critical parameters such as pH and applied voltage were studied to evaluate their effect on resolution and on efficiency. Optimum separation conditions were phosphate buffer pH 2.0, 5kV, and 2psis(-1) at 214nm. The analysis time was below 9min and the theoretical plates were between 6000 and 63,000N. Calibration curves were prepared for the antihistamines. The limits of detection were 4-14ngmL(-1), which allow their quantification in pharmaceuticals. The RSD% of each antihistamine was fairly good. Up to seven antihistamines belonging to the antihistaminic H(1)-receptor group were separated in the same electropherogram. The proposed method was then applied to the determination of antihistamines in pharmaceutical, urine, and serum samples with recoveries in agreement with the stated contents.

Algorithms↗

PubMed2005

Amitriptyline and nortriptyline serum determination by micellar liquid chromatography.

INTRODUCTION: Amitriptyline and nortriptyline are tricyclic antidepressants which act by enhancing the actions of norepinephrine and serotonin caused by blocking the re-uptake of various neurotransmitters at the neuronal membrane. A micellar liquid chromatographic procedure was developed to determine these drugs in serum samples for use in clinical monitoring. METHODS: The chromatographic determination of these highly hydrophobic substances was carried out using a 0.15 M SDS-6% (v/v) pentanol buffered at pH 7, in a C18 column, and electrochemical detection at 650 mV. The flow-rate was 1.5 mL/min. The analysis time was 14 min. RESULTS: The limits of detection (ng/mL) in serum were 0.25 and 0.31 for amitriptyline and nortriptyline, respectively. Repeatability and intermediate precision were evaluated at three different concentrations in serum samples. DISCUSSION: Untreated serum samples were injected directly into the HPLC system after filtration, leading to be a simple procedure that can be applied in routine analyses for Therapeutic Drug Monitoring.

Amitriptyline↗

PubMed2005

Direct injection determination of benzoylecgonine, heroin, 6-monoacetylmorphine and morphine in serum by MLC.

A simple and sensitive direct injection chromatographic procedure is developed for the determination of heroin, two of its metabolites (morphine and 6-monoacetylmorphine (6-MAM)), and benzoylecgonine (a metabolite of cocaine) in serum samples. The proper resolution of the four substances is obtained with a chemometrics approach, where the retention is modelled as a first step using the retention factors obtained in a limited number of mobile phases. Afterwards, an optimisation criterion that takes into account the position and shape of the chromatographic peaks is applied. The mobile phase selected to carry out the analysis was 0.1 mol L(-1) SDS-4% (v/v) butanol buffered at pH 7, in which the separation is performed in less than 18 min. The limits of quantification were in the 17-36 ng mL(-1) range. Intra- and inter-day assay accuracy and precision (below 3%) were obtained following ICH guidelines. The method developed was applied to the determination of the drugs studied in serum samples with good recoveries (90-104%). Serum samples from subjects that have been ingested cocaine and heroin were also analysed. The samples were injected directly in the chromatographic system without any pretreatment.

Chromatography, Liquid↗

PubMed2005

Monitoring bronchodilators with direct injection.

A procedure was developed for the determination of caffeine and theophylline using a C18 column (5 microm, 250 mm x 4.6 mm) and micellar liquid chromatography using hybrid mobile phases containing sodium dodecyl sulfate (SDS) and propanol, butanol or pentanol as modifiers. Detection was performed with a variable wavelength UV-vis detector at 272 nm. After the application of an interpretative strategy for the selection of the optimimum mobile phase, caffeine and theophylline can be resolved and determined in serum samples by direct injection, using a mobile phase made up of 50 mM SDS-2.5% (v/v) propanol-10 mM KH2PO4, pH 7, with an analysis time below 5 min. Calibration was linear in the range 0.05 to 50 microg mL(-1) with r > 0.999. The statistical evaluation of the method was examined by performing intra-day (n = 6) and inter-day calibration (n = 7) and was found to be satisfactory, with highly accurate and precise results. The proposed method was suitably validated and applied to the determination of caffeine and theophylline in serum samples of patients treated with bronchodilators.

Bronchodilator Agents↗

PubMed2005

Therapeutic monitoring of imipramine and desipramine by micellar liquid chromatography with direct injection and electrochemical detection.

A micellar liquid chromatographic (MLC) procedure was developed for the clinical monitoring of imipramine and its active metabolite, desipramine. The determination of these highly hydrophobic substances was carried out after direct injection of the serum samples using a mobile phase composed of 0.15 m SDS--6% (v/v) pentanol buffered at pH 7, pumped at 1.5 mL/min into a C(18) column (250 x 4.6 mm), and electrochemical detection at 650 mV. Using this MLC method, calibration was linear (r > 0.995) and the limits of detection (ng/mL) were 0.34 and 0.24 for imipramine and desipramine, respectively. Repeatabilities and intermediate precision were tested at three different concentrations in the calibration range and a CV (%) below 2.2 was obtained. In this MLC procedure, the serum is determined without treatment, thus allowing repeated serial injections without changes in retention factors, and reducing the time and consumables required to carry out the pretreatment process. The assay method can be applied to the routine determination of serum imipramine and its metabolite in therapeutic drug monitoring.

Antidepressive Agents, Tricyclic↗

PubMed2004

Micellar liquid chromatography in clinical chemistry: application to the monitorization of B6 vitamins.

BACKGROUND: A micellar reversed-phase liquid chromatographic procedure was developed for the determination of B6 group vitamins, i.e. pyridoxine, pyridoxal and pyridoxamine, in human serum. METHODS: Chromatographic conditions used were a C18 column, isocratic mode, flow-rate of 1 ml/min and UV-detection at 290 nm. Optimization of the composition of the mobile phase was performed using an interpretative strategy. RESULTS: After modeling, the composition of the selected mobile phase was 150 mM sodium dodecyl sulphate (SDS)--2% (v/v) pentanol-dihydrogenphosphate buffer 10 mM at pH 3. In this mobile phase, serum samples were injected without pretreatment and analysis time was below 14 min. Calibrations for the three vitamins were linear, with coefficient regression better than 0.999, and intra- and inter-day precision, achieved according to ICH, offering values below 4.3% and 3.2%, respectively. The method was applied to the determination of the B6 vitamins in spiked serum samples, with recoveries around 100%, and in the pharmacokinetic determination of pyridoxine half-life in serum, which was found to be 47.5 +/- 3.2 min (n = 5). The procedure was also applied for the analysis of pyridoxine in human serum spiked with several pharmaceutical preparations that contain other drugs which do not produce any kind of interference. Finally, solutions of B6 vitamins kept at -201 degrees C are stable for up to 3 months. CONCLUSIONS: Using the method proposed here, with an SDS-pentanol mobile phase, it is possible to carry out the fast sensitive determination of B6 vitamins in serum following direct injection, without sample pretreatment.

Buffers↗

PubMed2003

Micellar liquid chromatography determination of B vitamins with direct injection and ultraviolet absorbance detection.

A micellar reversed-phase liquid chromatographic procedure was developed for the control of five water-soluble vitamins, B (nicotinamide), B1 (thiamine), B2 (riboflavin), B6 (pyridoxine and pyridoxamine), in multivitamin pharmaceutical formulations (capsules, pills and syrups). Optimization procedure includes studies about the composition of the mobile phase (sodium dodecyl sulphate and the modifiers propanol, butanol or pentanol), flow-rate and temperature. Chromatographic analysis of all vitamins was carried out using a single mobile phase of 0.1 M SDS-4% (v/v) pentanol at pH 3, in a C18 column in isocratic mode, and UV-detection at 270, 290 and 325 nm. The flow-rates selected were 1.0 ml/min in the interval 0 to 6 min, and 2.0 ml/min until the end of the chromatogram and temperature was 45 degrees C. In the micellar liquid chromatographic system, the samples were injected without pretreatment, and the analysis time was below 12 min. Repeatabilities and intermediate precision were achieved according to ICH, and were below 5%. When the method is applied to real samples, the amount found with respect to the declared compositions were within the 91-105% range. These results were similar to those obtained with a conventional 60:40 (v/v) methanol-water mixture for some of the vitamins, but with the advantage of use a single mobile phase for the analyses of the five vitamins, with direct injection of the samples and reduced toxicity, flammability, environmental impact and cost of the micellar-pentanol solutions.

Chromatography, Liquid↗

PubMed2002

Direct injection micellar liquid chromatographic determination of benzodiazepines in serum.

A simple micellar liquid chromatographic (MLC) procedure is reported for the determination of several benzodiazepines in serum: bromazepam, diazepam, flunitrazepam, halazepam, medazepam, nitrazepam, oxazepam and tetrazepam. The optimization studies have been made in C(18) and C(8) columns, using solutions containing sodium dodecyl sulphate (SDS) modified with butanol or pentanol as mobile phases. The method proposed for the determination of the benzodiazepines uses a hybrid micellar mobile phase of 0.06 M SDS-5% butanol-0.01 M phosphate buffer (pH 7) at 25 degrees C, and UV detection (230 nm) in a C(18) column. The serum samples were injected directly, without any pretreatment, and eluted in less than 22 min, in accordance with their relative polarities, as indicated by their octanol-water partition coefficients. The limits of detection (ng ml(-1)) were within the ranges of 2-6 and 4-18 for aqueous and serum samples, respectively. Repeatability and intermediate precision were tested for three different concentrations of the drugs, and RSD (%) was below 10 for most of the assays. The MLC results were compared with those obtained from a conventional HPLC method using methanol-water 5:5 (v/v) which requires a previous extraction procedure.

Benzodiazepines↗

PubMed2002

Determination in serum of some barbiturates using micellar liquid chromatography with direct injection.

A procedure was developed for the determination of several barbiturates, amobarbital, barbital, hexobarbital, and secobarbital, using a C18 column (120 x 4.6mm) and micellar liquid chromatography (MLC) mobile phases containing sodium dodecyl sulfate (SDS) and propanol, butanol, or pentanol as a modifier, with UV detection at 230nm. After the application of an interpretative strategy of optimization, the four barbiturates can be resolved and determined in serum samples, allowing the direct injection in 0.10M SDS-4% (v/v) butanol, pH 7, with an analysis time below 8 min. In the proposed MLC procedure, linearities (r >0.999), limits of detection (ngmL(-1)) in the 30-70 range, repeatabilities, and intermediate precision below 1.8% are adequate for the quantification. The proposed method could be applied to the determination of barbiturates in serum samples with recoveries that agreed with the concentration added.

Barbiturates↗

PubMed2002

Therapeutic drug monitoring of anticonvulsant drugs by micellar HPLC with direct injection of serum samples.

BACKGROUND: We developed a micellar liquid chromatographic (MLC) procedure for the determination of three extensively monitored antiepileptics in serum samples: carbamazepine, phenobarbital, and phenytoin. METHODS: We determined the composition of the mobile phase after modeling the elution behavior of the antiepileptics in hybrid micellar mobile phases of sodium dodecyl sulfate (SDS) with different organic modifiers (propanol, butanol, or pentanol) in an experimental design that used five mobile phases, a C(18) column, and ultraviolet detection. In the micellar chromatographic system, the serum samples can be injected directly. RESULTS: The optimum mobile phase was 70 mL/L butanol in 0.05 mol/L SDS, pH 7, in which the three antiepileptics were resolved in <10 min. Intra- and interday precision was evaluated at four different drug concentrations within the therapeutic range (n =10); CVs were <2.1%. The method was applied to the analysis of 120 serum samples, and results were similar to those obtained by the TDx method. CONCLUSIONS: The MLC method allows chromatographic determination of three antiepileptics, using an interpretative strategy of optimization, without pretreatment of the serum samples and with direct injection in a hybrid micellar mobile phase of SDS-butanol. The method provides complete resolution and quantification of mixtures of two and three antiepileptics.

Anticonvulsants↗

PubMedDate not supplied

Simultaneous determination of three opiates in serum by micellar liquid chromatography using direct injection.

A simple and reliable micellar liquid chromatographic method was developed for the simultaneous determination of 3 opiates (codeine, morphine, and thebaine) in serum, using direct injection and ultraviolet detection. The separation of the drugs was optimized on a C18 column, thermostatically controlled at 25 degrees C, by evaluating mobile phases containing sodium dodecyl sulfate (SDS) and various modifiers (propanol, butanol, or pentanol). Adequate resolution of the opiates was obtained with a chemometrics approach, in which retention was modeled as a first step by using the retention factors for several mobile phases. Next, an optimization criterion that takes into account the position and shape of the chromatographic peaks was applied. The 3 opiates were totally resolved and determined in 12 min with the mobile phase 0.15M SDS-7% (v/v) butanol buffered at pH 7. The limits of detection for codeine and morphine were greatly improved by using fluorimetric detection. Repeatability and intermediate precision were tested for 3 different concentrations of the drugs, and the relative standard deviations were <0.8% for most of the assays. Finally, the method was successfully applied to the determination of morphine and codeine in serum samples.

Algorithms↗