Search results for "STANDARDS"
showing 10 items of 394 documents
On-line analysis of carbonyl compounds with derivatization in aqueous extracts of atmospheric particulate PM10 by in-tube solid-phase microextraction…
2011
Abstract A new device for carbonyl compounds based on coupling on-line and miniaturizing both, sample pretreatment and chromatographic separation, is reported. Two capillary columns, a GC capillary column (95% methyl–5% phenyl substituted backbone, 70 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve for in-tube solid-phase microextraction (IT-SPME) and a Zorbax SB C18 (150 mm × 0.5 mm i.d., 5 μm particle diameter) LC capillary column were employed. Different combinations of IT-SPME and derivatization using 2,4-dinitrophenylhydrazine (DNPH) were examined for mixtures containing 15 carbonyl compounds (aliphatic, aromatic and unsaturated aldehydes and ketones). A screening analys…
New micromethod combining miniaturized matrix solid-phase dispersion and in-tube in-valve solid-phase microextraction for estimating polycyclic aroma…
2008
Abstract Miniaturized matrix solid-phase dispersion (MSPD) was developed for the extraction of common polycyclic aromatic hydrocarbons (PAHs) from bivalve samples (100 mg, dry weight). Additional clean-up and analyte enrichment was accomplished by in-tube solid-phase microextraction (SPME). For this purpose the extracts collected after MSPD were diluted with water and injected into a capillary column coated with the extractive phase. This capillary column was connected to the analytical column by means of a switching valve. Separation and quantification of the PAHs were carried out using a monolithic LC column and fluorescence detection. Since the in-tube SPME device allowed the processing …
Fishing for a drug: solid-phase microextraction for the assay of clozapine in human plasma
1999
Solid-phase microextraction (SPME) was investigated as a sample preparation method for assaying the neuroleptic drug clozapine in human plasma. A mixture of human plasma, water, loxapine (as internal standard) and aqueous NaOH was extracted with a 100-micron polydimethylsiloxane (PDMS) fiber (Supelco). Desorption of the fiber was performed in the injection port of a gas chromatograph at 260 degrees C (HP 5890; 30 m x 0.53 mm I.D., 1 micron film capillary; nitrogen-phosphorous selective detection). Fibers were used repeatedly in up to about 75 analyses. The recovery was found to be 3% for clozapine from plasma after 30 min of extraction. However, in spite of the low recovery, the analyte was…
Determination of water-soluble UV-filters in sunscreen sprays by liquid chromatography.
2002
Abstract Liquid chromatography was used for the determination of the three most used water-soluble UV filters, benzophenone-4 (BZ4), terephthalylidene dicamphor sulfonic acid (TDS), and phenylbenzimidazole sulphonic acid (PBS), in aqueous sunscreen sprays. A C 18 stationary phase and an isocratic mobile phase of EtOH–20 m M sodium acetate buffer of pH 4.6 (30:70, v/v) were used at a flow-rate of 0.5 ml min −1 . Mobile phase was also used as solvent for samples and standards. UV detection was at 313 nm. The analytical run took 5.5 min. The limits of detection were 0.5, 0.9 and 2 μg ml −1 for BZ4, TDS and PBS, respectively. The proposed method does not involve highly toxic solvents.
Solid-Phase Microextraction Liquid Chromatography/Tandem Mass Spectrometry To Determine Postharvest Fungicides in Fruits
2003
A method to determine five postharvest fungicides (dichloran, flutriafol, o-phenylphenol, prochloraz, tolclofos methyl) in fruits (cherries, lemons, oranges, peaches) has been developed using solid-phase microextraction (SPME) coupled to liquid chromatography (LC) with photodiode array (DAD), mass spectrometry (MS), or tandem mass spectrometry (MS/MS) with ion trap detection. Extraction involved sample homogenization with an acetone/water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. The pesticides were isolated with a fused-silica fiber coated with 50-microm Carbowax/template resin. The effects of pH, ion strength, sample volume, and extraction time were in…
Identification of lipid binders in old oil paintings by separation of 4-bromomethyl-7-methoxycoumarin derivatives of fatty acids by liquid chromatogr…
2005
A HPLC-fluorescence method for identification of drying oils from binding media or protective film used in pictorial works of art prior to conservation or restoration is proposed. Fluorescence derivatization of fatty acids released by hydrolysis of structural drying oils is studied. The derivatization reagent was 4-(bromomethyl)-7-methoxycoumarin with 18-crown-6 as catalyst. Mobile phase was programmed from methanol-water (90:10 v/v) to methanol-water (100:0 v/v) in 25 min. The excitation and emission wavelengths were 325 and 395 nm, respectively. Under these chromatographic conditions, coumarin derivatives of myristic, palmitic, oleic and stearic acids were satisfactorily resolved. The met…
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 …
Delphi study for the design and validation of a questionnaire about digital competences in higher education
2016
The study of digital competence remains an issue of interest for both the scientific community and the supranational political agenda. This study uses the Delphi method to validate the design of a questionnaire to determine the perceived importance of digital competence in higher education. The questionnaire was constructed from different framework documents in digital competence standards (NETS, ACLR, UNESCO). The triangulation of non-parametric techniques made it possible to consolidate the results obtained through the Delphi panel, the suitability of which was highlighted through the expert competence index (K). The resulting questionnaire emerges as a good tool for undertaking future na…
Querying Dynamic and Context-Sensitive Metadata in Semantic Web
2005
RDF (core Semantic Web standard) is not originally appropriate for context representation, because of its initial focus on the ordinary Web resources, such as web pages, files, databases, services, etc., which structure and content are more or less stable. However, on the other hand, emerging industrial applications consider e.g. machines, processes, personnel, services for condition monitoring, remote diagnostics and maintenance, etc. to be specific classes of Web resources and thus a subject for semantic annotation. Such resources are naturally dynamic, not only from the point of view of changing values for some attributes (state of resource), but also from the point of view of changing “…
Taxation in Romania – Some Positive Aspects
2013
Abstract The field of taxation is often a subject of analysis, due to its importance for the formation and administration of public financial resources. By taking into account the local, national and international size of taxation, may be thus identified strengths, weaknesses, opportunities and threats. Although the taxation in Romania is often criticized both by taxpayers and by specialists, there is a progress in taxation field as a result of actions taken in forming and managing fiscal revenues. Without claiming an exhaustive approach, through this article we mention some positive aspects of Romanian taxation. We believe that these should be consolidated and continued.