Search results for "Performance."
showing 10 items of 4178 documents
Quantitation of talinolol in rat plasma by LC-MS-MS.
2010
The aim of this study was to develop and validate an assay based on liquid chromatography-tandem mass spectrometry to quantitate talinolol in rat plasma. After a simple protein precipitation step, separation was performed by reversed-phase liquid chromatography using gradient elution with acetonitrile-water-formic acid. Electrospray ionization in the positive ion mode with multiple reaction monitoring was used to analyze talinolol employing propranolol as internal standard. The calibration curve for talinolol was linear over the concentration range 1-250 ng/mL with a correlation coefficient0.995. The method was sensitive (limit of quantitation, 1 ng/mL) and had acceptable accuracy (85-115% …
Simultaneous quantification of the main organic acids and carbohydrates involved in tomato flavour using capillary zone electrophoresis
2002
A capillary zone electrophoresis (CZE) procedure for the simultaneous determination of the major organic acids (oxalate, malate and citrate) and carbohydrates (fructose, glucose and sucrose) in Lycopersicon fruits is reported. Comparison of this method with routine HPLC methods indicates that the CZE method offers several attractive features (speed, resolution, sensitivity and cost) which significantly improve the determination of these compounds. Detection limits were better than 1.6 µg ml−1 for organic acids and from 13 to 24 µg ml−1 for carbohydrates; repeatabilities were better than 2.1% for migration times and between 1.4 and 7.3% for peak areas. The proposed protocol is very useful to…
Extraction and analysis of ochratoxin A in bread using pressurised liquid extraction and liquid chromatography.
2005
A pressurised liquid extraction (PLE) method for the analysis of ochratoxin A (OTA) in bread samples is given. Parameters such as solvent, temperature, pressure and time were investigated thoroughly. The optimized PLE conditions were: methanol as extraction solvent, 80 degrees C, 2000 psi and a 5-min cycle. OTA was determined by liquid chromatography coupled with fluorescence detection and confirmed by methyl ester derivatization. Under these conditions OTA recovery is 92.3% with a RSD of 5%. Limits of detection and quantification were 0.02 and 0.06 microg/kg, respectively. The proposed method was applied to 20 bread samples, finding two positive samples with OTA levels below the maximum pe…
Determination of ochratoxin A in maize bread samples by LC with fluorescence detection.
2007
Ochratoxin A (OTA) is a secondary fungal metabolite produced by several moulds, mainly by Aspergillus ochraceus, A. carbonarius, A. niger and by Penicillium verrucosum. The present work shows the results of comparative studies using different procedures for the analysis of OTA in maize bread samples. The studied analytical methods involved extraction with different volumes of PBS/methanol, different extraction apparatus, and clean-up through immunoaffinity columns. The separation and identification were carried out by high-performance liquid chromatography with fluorescence detection. The optimized method for analysis of OTA in maize bread involved extraction with PBS:methanol (50:50), and …
DETERMINATION OF PENTOBARBITAL IN BIOLOGICAL SAMPLES BY MICELLAR LIQUID CHROMATOGRAPHY
1999
A liquid chromatographic procedure for the determination of pentobarbital in urine and plasma samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C18 analytical column, a guard column of similar characteristics, and a 0.02 M CTAB-15% 1-propanol at pH 7.5 mobile phase. The UV detector was set at 250 nm. Pentobarbital was isolated from urine and plasma samples by using a single solid phase extraction procedure with LMS cartridges. Mephobarbital was used as internal standard. Limits of detection were 0.53 μg/mL and 0.60 μg/mL in urine and plasma samples respectively. In both cases the coefficients of variation were lower than 6.5%, and the recoveries ranged betwe…
Automated determination of reboxetine by high-performance liquid chromatography with column-switching and ultraviolet detection.
2000
A fully automated method including column-switching and isocratic high-performance liquid chromatography (HPLC) was developed for quantitative analysis of the new antidepressant reboxetine, a noradrenaline reuptake inhibitor. After serum injection into the HPLC system and on-line sample clean-up on a silica C8 (10x4.0 mm I.D.) clean-up column with an eluent consisting of 2.5% acetonitrile in deionized water, the chromatographic separation was performed on an analytical column (Lichrospher CN; 250x4.6 mm I.D.) with an eluent of acetonitrile-aqueous potassium phosphate buffer (0.008 M, pH 6.4) (50:50). The UV detector was set at 273 or 226 nm. The limit of quantification was about 15 ng/ml at…
Determination of abamectin in citrus fruits by liquid chromatography-electrospray ionization mass spectrometry.
2000
Liquid chromatography coupled to electrospray mass spectrometry (LC-ES-MS) with positive ion detection was used to determine abamectin in oranges. MS conditions were optimized to achieve maximum sensitivity. The main ion for abamectin was [M+Na]+ at a fragmentor voltage of 180 V. Abundant structural information can be obtained at different fragmentor voltages. The detection limit for the standard solution was 12 pg injected, and good linearity and reproducibility were observed. Abamectin residues were extracted using matrix solid-phase dispersion. Orange samples were homogenized with C18 bonded silica placed onto a glass column and eluted with dichloromethane. Recoveries of the abamectin fr…
Derivatization techniques for automated chromatographic analysis of amphetamine usingo-phthaldialdehyde: A comparative study
2000
The potential of different chromatographic systems for automated, on-line analysis of amphetamine in biological fluids is illustrated. The various systems integrate analyte purification and enrichment, separation, derivatization in different derivatization modes witho-phthaldialdehyde (OPA) and N-acetyl-L-cysteine (NAC), and fluorimetric detection. The reliability of the systems has been tested by analysing urine and plasma samples containing amphetamine in the 0.1–20.0 μg mL−1 range. Pre, on and post-column derivatization strategies are compared in terms of their instrumental requirements, selectivity, sensitivity, linearity and reproducibility.
Automated determination of amisulpride by liquid chromatography with column switching and spectrophotometric detection.
2003
A fully automated chromatographic method including on-line blood serum or plasma clean-up, isocratic high-performance liquid chromatography (HPLC) and spectrophotometric detection was developed for quantitative analysis of the new antipsychotic drug amisulpride. After injection of serum or plasma onto the HPLC system and clean-up on a pre-column (10x4.0 mm I.D.) filled with Silica CN 20 micrometer (pore size 10 nm) by an eluent consisting of 8% acetonitrile in deionized water, the chromatographic separation was performed on Lichrospher CN (5 micrometer; 250x4.6 mm I.D.) by an eluent consisting of 50% acetonitrile and 50% aqueous potassium phosphate buffer (0.008 M, pH 6.4). The UV detector …
Thermal Lens Spectrometric Detection of Catecholamines after Oxidation to Aminochromes
1992
Abstract Experimental conditions for the spectrophotometric and thermal lens spectrometry (TLS) detection of catecholamines after oxidation to aminochromes with hexacyanoferrate (III) are optimized. At the low concentrations used in TLS, and in a 0.07 M citrate buffer, catecholamine oxidation can be performed at pH 7 and is immediate, whereas a lower pH value is required in spectrophotometry to avoid aminochrome polymerisation, the oxidation reactions being much slower. Similar TLS sensitivities are obtained for all catecholamines which facilitates HPLC evaluation. Sensitivity can be enhanced using a 50% ethanol-water medium. The linear dynamic range extends over two orders of magnitude, th…