1,720,985 research outputs found
Determination of simvastatin in pharmaceutical forms by HPLC and derivative UV-spectrophotometry
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Determination of Tenoxicam in Human Plasma using Solid-Phase Extraction and High-Performance Liquid Chromatography with Ultraviolet Detection
No full textA sensitive, specific and rapid liquid chromatographic procedure to selectively monitor tenoxicam in human plasma was developed and validated. Plasma samples were acidified and extracted using solid-phase exctration column. The procedure was linear from 0.1 to 10 μ.g/ml with a detection limit of 0.05μg/ml. The coefficient of variation for the procedure is 6.2% and 2.0% for the range of concentrations examinated. This method is suitable for pharmacological, toxicological and pharmacokinetic studies of tenoxicam
Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography
No full textA sensitive and stereoselective liquid chromatographic (HPLC) assay for the S and R enantiomers of furprofen in human plasma has been developed. The assay is based on derivatization with S(−)-1-phenylethylamine with formation of two diastereoisomeric derivatives and on their separation and quantitation using HPLC with uv detection. The method is linear from 25 to 600 ng ml−1 of both enantiomers, with a variation coefficient below 10.8%, and a detection limit of 20 ng ml−1. This procedure is suitable for pharmacokinetic studies
Simultaneous determination of enalapril maleate and hydrochlorothiazide in tablets by derivative UV spectrophotometry and high-performance liquid chromatography
No full textA method for the simultaneous determination of enalapril maleate and hydrochlorothiazide in pharmaceutical formulations (tablets) is described. The procedure is based on the use of the high-performance liquid chromatography (HPLC), and of the second-derivative ultraviolet spectra, by utilizing the linear relationship between substances concentration and derivative peak amplitude. The minimum concentration detectable by derivative spectrophotometry was 1 μg ml−1 for both drugs, and by HPLC 50 ng ml−1 for hydrochlorothiazide and 100 ng ml−1 for enalapril maleate. The relative standard deviations observed were approx. 2% for derivative spectrophotometry, and 1.5% for HPLC. The proposed methods, which give thoroughly comparable data, are simple and rapid, and allow precise and accurate results
Determination of Ofloxacin in Pharmaceutical Forms by High - Performance Liquid Chromatography and Derivative Uvspectrophotometry
No full textA method for the determination of ofloxacin in pharmaceutical forms is described. The procedure is based on the use of the high-performance liquid chromatography, and of the second-derivative ultraviolet spectra, by utilizing the linear relationship between substance concentration and derivative peak amplitude. The minimum concentration detectable by derivative spectrophotometry was 20 ng/ml, and by HPLC 10 ng/ml. The proposed methods, which give thoroughly comparable data, are simple and rapid, and allow precise and accurate results
Mitomycin C in biological fluids: Comparison of disk and cartridge solid-phase extraction and quantitation by HPLC in human plasma and ultrafiltrate
No full textThe performance of particle-loaded disks and traditional, packed extraction columns is compared. In this study, solid-phase extraction and liquid chromatographic analysis of the anticancer drug mitomycin C are duplicated using two devices that contain chemically similar C18 bonded silica. The following parameters are used to assess performance: linearity, recovery, precision, and lowest limit of detection. The extraction of mitomycin C from plasma and ultrafiltrate using particle-loaded membranes achieves better precision, improved concentration ability, lower detection limits, and greater efficiency. In addiction, elution of drug from the membrane adsorbent is efficiently accomplished using a small volume of mobile phase, eliminating analyte instability problems and the need for additional time-consuming evaporation
Determination of Rufloxacin, a New Tricyclic Fluoroquinolone in Biological Fluids Using High-Performance Liquid Chromatography with Ultraviolet Detection
No full textA simple, specific, and sensitive high-performance liquid chromatography method has been developed for routine monitoring of the antimicrobial agent rufloxacin in human serum and urine. Serum or urine-spiked with internal standard pipemidic acid, were vortex-mixed for 2 min with dichloromethane at pH 7.4. The evaporated extract was dissolved in 0.05 M NaOH. The mobile phase consisted of orthophosphoric acid, tetrabutylammonium iodide, and methanol. Drugs were resolved at ambient temperature on a 10 micron Viosfer LC-RP-18 column (250 x 4.6 mm I.D.) equipped with a guard column. Flow rate was 1.8 ml/min, and monitoring was performed at 295 nm. The calibration curve was linear from 0.1 to 10 micrograms/ml for human serum and from 0.05 to 10 micrograms/ml for urine. Retention times were 3.1 and 6.3 min for internal standard and rufloxacin. The detection limit of rufloxacin was 0.05 microgram/ml for human serum and 0.03 microgram/ml for urine. No interference from other commonly administered drugs or endogenous substances was observed. The assay demonstrated sufficient sensitivity and specificity for the study of the pharmacokinetics of rufloxacin in humans
Modelling of retention of pesticides in reversed-phase high-performance liquid chromatography: Quantitative structure-retention relationships based on solute quantum-chemical descriptors and experimental (solvatochromic and spin-probe) mobile phase descriptors
No full textA quantitative structure-retention relationship (QSRR) analysis based on multilinear regression (MLR) and artificial neural networks (ANNs) is carried out to model the combined effect of solute structure and eluent composition on the retention behaviour of pesticides in isocratic reversed-phase high-performance liquid chromatography (RP-HPLC). The octanol-water partition coefficient and four quantum chemical descriptors (the total dipole moment, the mean polarizability, the anisotropy of the polarizability and a descriptor of hydrogen-bonding based on the atomic charges on acidic and basic chemical functionalities) are considered as solute descriptors. In order to identify suitable mobile phase descriptors, encoding composition-dependent properties of both methanol- and acetonitrile-containing mobile phases, the Kamlet-Taft solvatochromic parameters (polarity-dipolarity, hydrogen-bond acidity and hydrogen-bond basicity, pi*, alpha and beta, respectively) and the N-14 hyperfine-splitting constant (a(N)) of a spin-probe dissolved in the eluent are examined. A satisfactory description of mobile phase properties influencing the solute retention is provided by a(N) and beta or alternatively pi* and beta. The two seven-parameter models resulting from combination of a(N) and beta, or pi* and beta, with the solute descriptors were tested on a set of 26 pesticides representative of 10 different chemical classes in a wide range of mobile phase composition (30-60% (v/v) water-methanol and 30-70% (v/v) water-acetonitrile). Within the explored experimental range, the acidity of the eluent, as quantified by alpha, is almost constant, and this parameter is in fact irrelevant. The results reveal that a(N) and pi*, that can be considered as interchangeable mobile phase descriptors, are the most influent variables in the respective models. The predictive ability of the proposed models, as tested on an external data set, is quite good (Q(2) close to 0.94) when a MLR approach is used, but the modelling capability can be further improved using an artificial neural network. (c) 2007 Elsevier B.V. All rights reserved
Development of a Liquid Chromatographic Method for the Determination of Sildenafil in Seminal Plasma
No full textA sensitive high performance liquid chromatographic (HPLC) method with ultraviolet absorption detection (230 nm) was developed and validated for the determination of a phosphodiesterase V inhibitor, Sildenafil, in seminal plasma. A single step liquid–liquid extraction procedure using ethyl acetate was performed to recover sildenafil from 1.0 mL of seminal plasma combined with 200 μL of NaOH 0.1 M. A symmetry C18 column (150 × 4.6 mm I.D. 5 μm) was used as a stationary phase and the mobile phase consisted of 32% acetonitrile and 68% phosphoric acid (0.016 M; pH 5.3) at a flow rate of 1.0 mL/min. The quantitation limit was 5 ng/mL. Intra‐ and inter‐day relative standard deviation (RSD) did not exceed 6.6%. This HPLC method has been successfully used in medical laboratories to assay seminal plasma samples for studies on the treatment with sildenafil
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