Search results for "Liquid Chromatography"
showing 10 items of 942 documents
Matrix solid-phase dispersion microextraction and determination by high-performance liquid chromatography with UV detection of pesticide residues in …
1999
A multiresidue method based on matrix solid-phase dispersion (MSPD) microextraction was studied to determine the carbamate, benfuracarb, and urea insecticides, diflubenzuron, flufenoxuron hexaflumuron and hexythiazox, used in control of citrus pests. Optimisation of different parameters, such as the type of solid support for matrix dispersion, elution solvents and the clean-up step were carried out. The method used 0.5 g of orange sample, C8 bonded silica as MSPD sorbent and dichloromethane as eluting solvent. Recoveries, at spiked concentrations below the maximum residue levels established by Spanish Government, were between 74 and 84% with relative standard deviations ranging from 2 to 4%…
Complementary mobile-phase optimisation for resolution enhancement in high-performance liquid chromatography.
2000
An optimisation methodology in high-performance liquid chromatography (HPLC) is presented for the selection of two or more mobile phases having an optimal complementary resolution. The complementary mobile phases (CMPs) are selected in such a way that each one resolves optimally only some compounds in the mixture, while the remainder, resolved by the other mobile phase(s), can overlap among them. The methodology is based on the computation of a peak purity measurement for each solute, using an asymmetrical peak model for peak simulation. Two global resolution criteria (product of elementary resolutions and worst elementary resolution) and two methods for solving the problem (a systematic ex…
Comparison of two partial least squares infrared spectrometric methods for the quality control of pediculosis lotions.
2006
Two vibrational spectroscopy procedures have been developed and compared for the direct and simultaneous determination of piperonyl butoxide and tetramethrin, the active ingredients of alcoholic capillary lotions, for hair pediculosis diseases. Nine lotions, purchased from the Spanish market, were analyzed using both, attenuated total reflectance (ATR) and transmission FT-IR measurements, and based on the use of partial least squares (PLS) multivariate calibration. A reduced set of 15 matched standards (11 for calibration and 4 for validation) was employed using both measurement modes. The spectral wave number ranges between 1757 and 1712 cm(-1) was selected to determine tetramethrin by bot…
Detection of batch effects in liquid chromatography-mass spectrometry metabolomic data using guided principal component analysis.
2014
Metabolomics based on liquid chromatography-mass spectrometry (LC-MS) is a powerful tool for studying dynamic responses of biological systems to different physiological or pathological conditions. Differences in the instrumental response within and between batches introduce unwanted and uncontrolled data variation that should be removed to extract useful information. This work exploits a recently developed method for the identification of batch effects in high throughput genomic data based on the calculation of a delta statistic through principal component analysis (PCA) and guided PCA. Its applicability to LC-MS metabolomic data was tested on two real examples. The first example involved t…
High-performance micellar liquid chromatography determination of sulphonamides in pharmaceuticals after azodye precolumn derivatization
1995
Abstract A chromatographic procedure with precolumn derivatization to form the N-(1-naphthyl)ethylenediamine dihydrochloride azodyes is proposed for the analysis of several sulphonamides (sodium sulphacetamide, sulphadiazine, sulphaguanidine, sulphamerazine, sulphamethizole, sulphamethoxazole, sulphanilamide and sulphathiazole) in pharmaceutical preparations (tablets, pills, capsules, suspensions and drops). The separation is performed with a 0.05 M sodium dodecyl sulphate/2.4% pentanol eluent at pH 7. The precolumn derivatization improved the resolution in the chromatograms and increased the selectivity in the determination of mixtures of sulphonamides and in preparations where other drugs…
Plasma pharmacokinetics and tissue distribution study of cajaninstilbene acid in rats by liquid chromatography with tandem mass spectrometry
2010
Cajaninstilbene acid (CSA; 3-hydroxy-4-prenyl-5-methoxystilbene-2-carboxylic acid) is a major active constituent of pigeonpea leaves, has been proven to be effective in clinical treatment of diabetes, hepatitis, measles and dysentery. A rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of CSA in rat plasma and various tissues (brain, heart, lung, liver, spleen, small intestine and kidney) of rat for the first time. Rat plasma and tissue distribution pre-treated by protein precipitation with acetoacetate was analyzed using LC-MS/MS with an electrospray ionization (ESI) interface, and isoliquiritigenin was us…
Are analysts doing method validation in liquid chromatography?
2014
International audience; Method validation is being applied in the reported analytical methods for decades. Even before this protocol was defined, authors already somehow validated their methods without full awareness. They wished to assure the quality of their work. Validation is an applied approach to verify that a method is suitable and rugged enough to function as a quality control tool in different locations and times. The performance parameters and statistical protocols followed throughout a validation study vary with the source of guidelines. Before single laboratory validation, an analytical method should be fully developed and optimized. The purpose of the validation is to confirm p…
Analysis of Urine Samples Containing Cardiovascular Drugs by Micellar Liquid Chromatography with Fluorimetric Detection
1999
A simple direct injection chromatographic procedure with fluorimetric detection is successfully applied to the determination of mixtures of 4 diuretics (amiloride, bendroflumethiazide, piretanide, and triamterene) and 6 beta-blockers (acebutolol, atenolol, labetalol, metoprolol, nadolol, and propranolol), which are usually administered in combinations for the treatment of hypertension, in urine samples. The procedure makes use of C18 columns and micellar mobile phases of sodium dodecyl sulphate (SDS), propanol, and phosphate buffer at pH 3. The adequate resolution of most drugs is obtained with a chemometrics approach where the retention is modeled as a first step using the retention factor…
Determination of the relative quantum yields of the conformational species of autoassociating polypeptide gramicidin A in organic solvent using combi…
1987
Abstract A simple, novel method is proposed for the accurate determination of the relative quantum yields of each of the interconverting conformational species of the autoassociating polypeptide gramicidin A in organic solution. The method is based on fitting the experimental results obtained independently from fluorescence emission spectroscopy and high performance liquid chromatography. The fluorescence parameters obtained are discussed in terms of the structural features of the individual conformational species. The advantages of this approach and its possible application to other different organic solvents or to other autoassociating polypeptides are also considered.
Biopartitioning micellar chromatoraphy to predict blood to lung, blood to liver, blood to fat and blood to skin partition coefficients of drugs
2009
[EN] Biopartitioning micellar chromatography (BMC), a mode of micellar liquid chromatography that uses micellar mobile phases of Brij35 in adequate experimental conditions, has demonstrated to be useful in mimicking the drug partitioning process into biological systems. In this paper, the usefulness of BMC for predicting the partition coefficients from blood to lung, blood to liver. blood to fat and blood to skin is demonstrated. PLS2 and multiple linear regression (MLR) models based on BMC retention data are proposed and compared with other ones reported in bibliography. The proposed models present better or similar descriptive and predictive capability. (C) 2008 Elsevier B.V. All rights r…