Search results for "Quantitative"
showing 10 items of 2409 documents
On-line solvent recycling: a tool for the development of clean analytical chemistry in flow injection Fourier transform infrared spectrometry. Determ…
1998
Abstract A flow injection strategy has been developed for the direct determination of ketoprofen in pharmaceuticals by Fourier transform infrared spectrometry also incorporating a distillation unit which allows the carbon tetrachloride employed to dissolve samples and standards and used as a carrier to be recovered on-line. The system developed permits a drastic reduction of reagent consumption and easy and fast sampling and cleaning of the measurement cell. For the quantification of ketoprofen in pharmaceuticals the carbonyl bands at 1712 and 1666 cm −1 were employed and the developed method provided a 3 σ limit of detection of 0.04 mg ml −1 , a dynamic range up to 10 mg ml −1 and typical …
Application of ACC method to synchronous luminiscence: determination of alpha-tocopherol and alpha-tocopheryl acetate in beverages.
2001
A new method based on the Q parameter, that permits the determination of the C(compound A)/C(compound B) ratio without preparing calibration graphs of the two compounds, is proposed. This method has been applied to signals obtained by synchronous luminiscence. Simultaneous determination of alpha-tocopherol and alpha-tocopheryl acetate in beverages using synchronous fluorescence has been carried out. To isolate the compounds from samples, liquid extraction with n-hexane as the organic phase was employed. The presence of interferences was tested using the apparent content curves (ACC) method and the C(alpha-tocopherol)/C(alpha-tocopheryl acetate) ratio was calculated using the Q parameter. Th…
Determination of furosemide in urine samples by direct injection in a micellar liquid chromatographic system.
2002
A sensitive, selective and efficient micellar liquid chromatographic (MLC) procedure was developed for the determination of furosemide (4-chloro-N-furfuryl-5-sulfamoylanthranilic acid) in urine samples by direct injection and UV detection. The procedure makes use of a C18 reversed-phase column and a micellar mobile phase of 0.05 mol l(-1) sodium dodecyl sulfate-6% v/v propanol and phosphate buffer at pH 3 to resolve furosemide from its photochemical degradation products. The importance of protecting the standards and urine samples to be analysed from light in the assay of furosemide, avoiding its degradation, was verified. The limit of quantification was 0.15 microg ml(-1) and the relative …
Liquid Chromatography Quadrupole Time-of-Flight Mass Spectrometry Analysis of Carbosulfan, Carbofuran, 3-Hydroxycarbofuran, and Other Metabolites in …
2007
The potential of liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS) to identify and confirm carbosulfan and seven of its main metabolites (carbofuran, 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxy-7-phenol carbofuran, 3-keto-7-phenolcarbofuran, 7-phenolcarbofuran, dibutylamine) at trace levels from food is explored for the first time. The analytical method developed consists of pressurized liquid extraction (PLE) and LC-QqTOF-MS in positive ion mode, which attains unequivocal identification and quantification of the studied compounds in food, at levels well below of those of concern (0.05 mg/kg for the sum of carbosulfan, carbofuran, and 3-hydroxycarbofuran).…
Supercritical fluid chromatography in drug analysis: A literature survey
1996
The applications of supercritical fluid chromatography to the analysis of drugs have been carefully revised from the literature compiled in the Analytical Abstracts until March 1994. Easy-to-read tables provide useful information about the state-of-the-art and possibilities offered by SFC in pharmaceutical analysis. The tables comprise extensive data about samples analyzed, pharmaceutical principles determined, solvents used and sample quantity injected, supercritical fluids and modifiers employed, injection system, instrumentation, experimental conditions for chromatographic separations (density, pressure, flow, temperature), characteristics of columns employed (type, support, length, diam…
Amphetamine and methamphetamine determination in urine by reversed-phase high-performance liquid chromatography with sodium 1,2-napthoquinone 4-sulfo…
1995
A rapid method is described for the identification and determination of amphetamine and methamphetamine in human urine samples by liquid chromatography with UV-Vis detection. The samples were transferred onto a C18 solid-phase extraction column and chromatographed on a Hypersil ODS RP C18, 5 microns (250 x 4 mm I.D.) with an acetonitrile-water elution gradient containing propylamine. Under these conditions, the amines are eluted with a short retention time. The procedure has been applied to the determination of amphetamine and methamphetamine in the range 0.3-4.0 micrograms/ml in spiked urine samples. The detection limits at 280 nm were 4 and 2 ng/ml for amphetamine and methamphetamine, res…
Flow analysis-spectrophotometric determination of ?-dopa in pharmaceutical formulations by reaction with p-Aminophenol
1994
Abstract A new method has been developed for the spectrophotometric determination of l -dopa in pharmaceutical formulations. The method is based on the reaction between the open-chain quinone of l -dopa, obtained in NaOH, and the benzoqinoneimine form of p-aminophenol, in the presence of KIO4. The reaction product is determined at 574 nm by using both alternately procedures, one based on the stopped-flow and another on a flow injection approach. Under the best experimental conditions L-dopa can be determined with a limit of detection of 52 ng/ml and a relative standard deviation of 0.2% for three replicate measurements of a solution containing 4 μg/ml.
Determination of catecholamines as aminochromes by micellar liquid chromatography with thermal lens spectrophotometric detection
1994
The determination of catecholamines (CAs) using micellar liquid chromatography with thermal lens spectrophotometric detection has been studied. CAs are oxidized with hexacyanoferrate(III) to aminochromes which are separated with a mobile phase of 0.05 M sodium dodecyl sulphate, 7% propanol and 0.03 M citrate buffer, pH 4.8, on a partially endcapped C18 column. The aminochrome-micelles and aminochrome-stationary phase association constants are evaluated. Using the 488 nm line of an Ar+ laser with 250 mW pump power the limits of detection are about 4 ng mL−1. The technique is applied to the determination of unconjugated CAs in urine using isoproterenol as internal standard.
Flow injection determination of free and total cholesterol in animal greases using enzymes in non-aqueous media
1998
A non-covalently coimmobilized bienzymic reactor of horseradish peroxidase (HRP) and cholesterol oxidase (COD), operating in a continuous organic flowing stream of 1 × 10–3 M p-anisidine in buffer-saturated (pH 7.0) toluene, has been employed for cholesterol determination in animal greases, such as pig, beef, and chicken fat, and codfish liver oil. The method provides a good linear relationship up to 1.8 × 10–3 M cholesterol and average recoveries of 99.5%, a high sensitivity, with a detection limit of 1 × 10–6 M of cholesterol and a good precision (an interday RSD of 1.8% for the determination of total cholesterol in a codfish oil sample). The method permits the direct spectrophotometric d…
Comparative assessment of three extraction procedures for determination of emerging Fusarium mycotoxins in pasta by LC–MS/MS
2013
Abstract A new rapid, sensitive, reproducible and reliable method was developed for the quantitative determination of enniatins A, A1, B and B1, beauvericin and fusaproliferin in dry and fresh pasta by liquid chromatography-triple quadrupole-tandem mass spectrometry. A comparative study of different rapid and economical extraction procedures was performed for the extraction of these mycotoxins in pasta. For this purpose, three different approaches were studied during the extraction step (Ultra-Turrax, ultrasonic bath and microwave). Optimal extraction conditions were reached using Ultra-Turrax with acetonitrile for 3 min without purification step. The chromatographic separation of the six m…