Search results for "Reference Standards"
showing 10 items of 156 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 …
Stability of nitroaromatic specialty explosives in reversed-phase liquid chromatographic systems
2008
Abstract In this study, the stability of 2,4-dinitroanisole, 2,2′,4,4′,6,6′-hexanitrodiphenylsulfide, 2,3,4,6-tetranitroaniline, 2,4,6-trinitroaniline, 2,4,6-trinitroanisole, and 2,4,6-trinitrochlorobenzene in liquid chromatographic systems was studied under different solvent/eluent conditions. Stock solutions of the explosives were prepared in acetonitrile and diluted with acetone/water, acetonitrile/water, or methanol/water mixtures. Within 48 h, these working solutions were repeatedly injected onto a silica column and eluted with acetonitrile/water or methanol/water mobile phases. Under all conditions, 2,4-dinitroanisole was stable, whereas 2,4,6-trinitroaniline was stable only in the me…
Photo-induced fluorescence of magnesium derivatives of tetracycline antibiotics in wastewater samples
2009
Abstract An analytical strategy, for the determination of tetracyclines (TCs), based on a HPLC system coupled with a photo-reactor followed by post-column derivatization was developed. Higher fluorescence emission after coupling the resulting photo-fragments with magnesium ions was observed for the determination of minocycline (MC), epitetracycline (ETC), tetracycline (TC) and doxycycline (DC). The manifold included a HPLC system with a photo-reactor (PTFE tubing helically coiled around a low-pressure mercury lamp), a mixing T-piece and a fluorescence detector. The derivatization reagent was delivered at 0.5 mL min −1 by a pump. After HPLC separation using a gradient system with a mobile ph…
Study of mycotoxin calibration approaches on the example of trichothecenes analysis from flour
2012
The aim of this study was to evaluate the applicability of different calibration approaches in trichothecenes analysis from wheat flour. Concretely eight trichothecenes (five type B trichothecenes and three type A trichothecenes) were analyzed by matrix solid-phase dispersion (MSPD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the first set of experiments the presence of matrix effects was evaluated; values ranged between 59% and 79%. In the second set of experiments, solutions to compensate these signal suppressions were examined. Different calibration methods showed to tackle matrix effects obtaining values between 69% and 85% for external matrix matched calibration a…