Search results for "Chromatography."
showing 10 items of 5021 documents
Colorimetric quantitation of trace amounts of sodium lauryl sulfate in the presence of nucleic acids and proteins
1992
A fast and sensitive procedure for the colorimetric detection of sodium lauryl sulfate (SDS) is presented. The assay is based upon the formation of a chloroform-extractable ion pair between lauryl sulfate and methylene blue that is quantified spectrophotometrically with an estimated detection limit of 150 ng of SDS. The method is suitable for the monitoring of contaminating traces of SDS in protein or nucleic acid samples that have the potential to interfere with enzymatic manipulations such as proteolytic digest, restriction analysis, or reverse transcription. Since the procedure is extremely simple and no special equipment is required it is accessible to every researcher concerned with SD…
Substituted Dibenzothiophenes I: Synthesis, Chromatography, Mass Spectrometry and Structure Elucidation by1H NMR Spectroscopy
1992
Abstract Some polychlorinated and polymethylated dibenzothiophenes have been synthesized to serve as model compounds in environmental analysis. In order to obtain pure isomers, the synthesis mixtures have been fractionated with reversed-phase high performance liquid chromatography. In spite of a high sensitivity, mass spectrometry does not provide any reliable way to determine the precise structures of different isomers. Therefore, 1H NMR spectroscopy has been utilized as an aid in their analysis. The structures for two isomeric tetramethyldibenzothiophenes could be suggested on the basis of their 1H NMR spectra. Also some proposals for possible structures of two isomeric trimethyldibenzoth…
The synthesis of metallocene-labelled drugs for biological assays
1990
Several drugs (amphetamine, desipramine, nortriptyline, phenobarbital) have been labelled with metallocenic fragments in order to develop a new immunoassay method. The metallocenic fragments are cymantrenic or benchrotrenic derivatives: the linkage between the organic and organometallic moieties has been achieved by reactions between amino and acidic functional groups. All the products (metallohaptens), purified by different chromatography techniques, have been fully characterized by IR and 1H NMR spectroscopy and their mass spectra.
Formation of 2,4,6-trichlorophenol and 2,4,6-trichloroanisole during treatment and distribution of drinking water
1995
Biomethylation of 2,4,6-trichlorophenol to the potent off-flavour compound 2,4,6-trichloroanisole has previously been found to cause taste and odour problems in drinking water. In the present study, both compounds were detected in seemingly unpolluted surface waters. However, the highest concentrations of 2,4,6-trichloroanisole in tap water were caused by the formation of 2,4,6-trichlorophenol during chlorine disinfection of drinking water and subsequent methylation of this compound in the distribution system. Analysis of samples from several sites in the investigated distribution systems showed that there was a substantial spatial and temporal variation of the concentration of both 2,4,6-t…
The molecular identification of organic compounds in the atmosphere: state of the art and challenges.
2015
SSCI-VIDE+ATARI:CARE+BNO:BDA; International audience
Shelf life improvement of the loaf bread using allyl, phenyl and benzyl isothiocyanates against Aspergillus parasiticus
2017
Abstract Fungal growth inhibition and aflatoxins (AFs) reduction using allyl (AITC), benzyl (BITC) and phenyl (PITC) isothiocyanates were studied in loaf bread contaminated with Aspergillus parasiticus . Two inoculated loaf bread slices were introduced into a plastic tray together with paper filters or small plastic bags paper filters soaked with AITC, BITC or PITC, the final concentration inside the package was of 0.5, 1 or 5 μL/L. The plastic trays, incubated at room temperature, were visual examined for the shelf life evaluation during 8 days. The quantification of the AFs was carried out using liquid chromatography coupled to mass spectrometry (LC-MS/MS). Shelf life increase of three an…
Cheese flavour : instrumental techniques
2004
This chapter discusses instrumental techniques to analyze cheese flavor. It focuses on recent advances made to study and identify the taste-active components present in the water-soluble fraction of cheese. A general procedure for the preparation of fractions involves an extraction of grated cheese by water followed by a fractionation scheme, generally adapted from the fractionation protocol used to isolate cheese nitrogen fractions in the study of proteolysis in cheese during ripening. However, as sub-fractions have to be evaluated sensorially to assess their relative sensory impact and try to link it to their chemical composition, a suitable eluent has to be used in the chromatographic st…
Volatile components of dry-cured ham
1991
The volatile components of dry-cured ham were isolated by vacuum distillation and analyzed by gas chromatography-mass spectrometry. The structures of 76 molecules were identified by mass spectrometry, cochromatography, or measured Kovats indices. The compounds identified may come from the catabolism of the main constituent parts of the meat (glucids, lipids and protids) during the curing of the hams, from the pig feed, or from technological processes. The volatile compounds extracted from 50 g of ham according to the technique described correspond to a chromatographical surface equivalent to 0.12 mg of the dodecane internal standard, or approximately 2.4 ppm of the weight of the sample. Fla…
Evaluation of taste compounds in water-soluble extract of goat cheeses
2000
Abstract The water-soluble fractions of two goat cheeses — one denomination of origin commercial trade mark (crottin de Chavignol®) and one bought in a local cheese making establishment (Bouton de culotte®) — containing many taste and flavour molecules were studied. Ultrafiltration with a 1000 Da threshold membrane, followed by gel filtration on Toyopearl HW-40S gel using water as eluent, led to the production of edible fractions. Physicochemical and sensory analysis of these fractions showed that the most tasty fractions contained, essentially, the free amino acids and mineral salts. Some of these tasty fractions also imparted some flavours. The quantity of small peptides (MW
Chiral Serum Pharmacokinetics of 4-Fluoroamphetamine after Controlled Oral Administration
2021
Abstract Over the last two decades, misuse of 4-fluoroamphetamine (4-FA) became an emerging issue in many European countries. Stimulating effects last for 4–6 hours and can impact psychomotor performance. The metabolism of amphetamine-type stimulants is stereoselective and quantification of (R)- and (S)-enantiomers has been suggested for assessing time of use. To date, no data on enantioselective pharmacokinetics is available for 4-FA in serum samples. An enantioselective liquid chromatography−tandem mass spectrometry (LC–MS-MS) method was developed using a chiral Phenomenex® Lux 3 μm AMP column. Validation of the method showed satisfactory selectivity, sensitivity, linearity (0.5–250 ng/mL…