Search results for "Liquid Chromatography"

Performance of micellar mobile phases in reversed-phase chromatography for the analysis of pharmaceuticals containing beta-blockers and other antihyp…

1996

A rapid and simple reversed-phase micellar liquid chromatographic procedure for the simultaneous determination of the beta-blockers atenolol, metoprolol and oxprenolol, the diuretics amiloride, bendroflumethiazide, chlorthalidone and hydrochlorothiazide and the vasodilator hydralazine in pharmaceuticals, is proposed. An interpretive optimization procedure, which uses the chromatographic data for only five mobile phases, was applied to select a suitable micellar mobile phase. A comparative study was also made of the performance of micellar and aqueous-organic mobile phases in the analysis of pharmaceuticals that combine beta-blockers and diuretics. The determination of all the drugs could be…

Comparative HPLC/ESI-MS and HPLC/DAD study of different populations of cultivated, wild and commercial Gentiana lutea L.

2015

The root of Gentiana lutea L., famous for its bitter properties, is often used in alcoholic bitter beverages, food products and traditional medicine to stimulate the appetite and improve digestion. This study presents a new, fast, and accurate HPLC method using HPLC/ESI-MS and HPLC/DAD for simultaneous analysis of iridoids (loganic acid), secoiridoids (gentiopicroside, sweroside, swertiamarin, amarogentin) and xanthones (isogentisin) in different populations of G.lutea L., cultivated in the Monti Sibillini National Park, obtained wild there, or purchased commercially. Comparison of HPLC/ESI-MS and HPLC/DAD indicated that HPLC/ESI-MS is more sensitive, reliable and selective. Analysis of twe…

Chiral determination of amphetamine and related compounds using chloroformates for derivatization and high-performance liquid chromatography

1999

The enantiomeric determination of amphetamine and various amphetamine-type compounds by liquid chromatography after chiral derivatization with 9-fluorenylmethyl chloroformate-L-proline (FMOC-L-Pro) is reported. The results obtained were compared with those achieved after achiral derivatization with 9-fluorenylmethyl chloroformate and subsequent separation of the derivatives on a beta-cyclodextrin chiral stationary phase. Conditions for the derivatization of amphetamines with FMOC-L-Pro were investigated, including the effect of the derivatization reagent concentration, pH and reaction time, using amphetamine, ephedrine and pseudoephedrine as model compounds. On the basis of these studies, p…

Determination of Caffeine in Analgesic Formulations Using the Apparent Content Curves Method

1994

Abstract The determination of caffeine by UV spectroscopy in pharmaceutical samples, containing different compounds which provide spectral interferences as aspirin, paracetamol, chlorfeniramine or propylphenazone, is carried out. The proposed procedure is based on the apparent content curves method in order to resolve binary, ternary and multicomponent mixtures. Results obtained are, in all cases, in agreement with contents found by a HPLC procedure used as reference method.

Influence of the addition of modifiers on solute-micelle interaction in hybrid micellar liquid chromatography

1998

In reversed-phase micellar liquid chromatography (MLC) organic modifiers are usually added to the mobile phase to modify the eluent strength and to increase the efficiency of the chromatographic peaks. The effect of the modifiers methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, acetonitrile and tetrahydrofuran on the critical micelle concentration (cmc) of the anionic surfactant sodium dodecylsulphate (SDS) has been studied to enable understanding of the interactions between solute, micelles and bulk liquid in such hybrid eluents. Methanol, acetonitrile and tetrahydrofuran increased thecmc, whereas the other alcohols reduced its value. For butanol and pentanol, which partition into the…

Simple high-performance liquid chromatographic assay for polyamines and their monoacetyl derivatives.

1993

A rapid reversed-phase high-performance liquid chromatographic method, using pre-column derivatization with benzoyl chloride and ultraviolet detection at 254 nm, was developed for the simultaneous measurement of polyamines and their monoacetyl derivatives. Calibration curves were linear for concentrations from 1.25 to 25 nmol/ml. The method was employed to assay these compounds in chick embryo retina explants using organic solvent extraction and 1,7-diaminoheptane as an internal standard. This simple and sensitive method can be applied to routine determinations of these compounds in various biological samples.

Validation of a high-performance chromatographic method for determination of cefotaxime in biological samples

1999

An analytical method for detecting and quantifying cefotaxime in plasma and several tissues is described. The method was developed and validated using plasma and tissues of rats. The samples were analyzed by reversed phase liquid chromatography (HPLC) with UV detection (254 nm). Calibration graphs showed a linear correlation (r > 0.999) over the concentration ranges of 0.5–200 μg/mL and 1.25–25 μg/g for plasma and tissues, respectively. The recovery of cefotaxime from plasma standards prepared at the concentrations of 25 μg/mL and 100 μg/mL was 98.5 ± 3.5% and 101.8 ± 2.2%, respectively. The recovery of cefotaxime from tissue standards of liver, fat and muscle, prepared at the concentration…

Evaluation by HPLC-UV of Polar Pesticides in Rice Fields

1999

Ultra-high-pressure liquid chromatography tandem mass spectrometry method for the determination of 9 organophosphate flame retardants in water samples

2016

Few methods are available for comprehensive organophosphate flame retardants (PFRs) detection in water and wastewater. Gas chromatography has been employed previously, but this approach is less selective, not amenable for use with deuterated standards and can suffer unfavorable fragmentation. Ultra-high-pressure liquid chromatography tandem mass spectrometry (UHPLC-QqQ-MS/MS) has become the most promising platform, already applied successfully for analysis of selected PFRs in some environmental matrices like water and wastewater. However, the presence of some interferences from the dissolvent, the equipment and the used materials should be taken into account. The procedure involves: The fir…

Liquid chromatography–mass spectrometry as a tool for wastewater-based epidemiology: Assessing new psychoactive substances and other human biomarkers

2017

Wastewater-based epidemiology (WBE) started to develop significantly in the last 8 years due, in part, to the advance of liquid chromatography–mass spectrometry (LC–MS). Its initial objective ― to estimate the consumption of illicit drugs ― has been expanded to new psychoactive substances (NPS) and other human biomarkers of health, lifestyle and disease. The purpose of this review is to introduce recent methods and outstanding challenges in the application of LC–MS to these new targets, including target, suspect and non-target screening and, outline the workflows developed for discovering metabolites of NPS and biomarkers. Further, we discuss a number of specific methodological challenges t…