Search results for "Pill"
showing 10 items of 1870 documents
Determination of optical purity of phosphonic acid analogues of aromatic amino acids by capillary electrophoresis with alpha-cyclodextrin.
2000
A simple and efficient method for the determination of enantiomeric purity of structurally diverse phosphonic and phosphinic acid analogues of phenylalanine and phenylglycine using capillary electrophoresis is presented. These preliminary studies indicated that the enantiomer separation is strongly dependent on the structure of the aminophosphonic acid.
Gas chromatography of homologous esters
1984
Abstract The gas chromatographic retention behaviour of the butanoyl and 2-, 3- and 4-chlorobutanoyl esters of C 3 —C 5 saturated aliphatic branched-chain and unsaturated C 3 —C 6 alcohols on SE-30 and OV-351 glass capillary columns operated iso-thermally at several temperatures is reported. Retention index increments at 80, 120 and 160°C show the effects of chain branching and the olefinic and acetylenic unsaturation in the alkyl chain and the effect of the position of the chlorine substituent in the acyl chain. The results are compared with the behaviour of the corresponding n -alkyl esters and the chlorinated propanoyl esters.
Fast determination of prominent carotenoids in tomato fruits by CEC using methacrylate ester-based monolithic columns.
2007
In this study, the major carotenoids (beta-carotene and lycopene) present in tomato fruits were analyzed by CEC with a methacrylate ester-based monolithic column. The effects of the porogenic solvent ratio, and the hydrophobicity of bulk monomer employed were examined on carotenoids separations. A fast separation of these analytes was achieved in less than 5.0 min in a mobile phase containing 35% THF, 30% ACN, 30% methanol, and 5% of a 5 mM Tris aqueous buffer, pH 8, with lauryl methacrylate-based monoliths. The CEC method was evaluated in terms of detection limit and reproducibility (retention time, area, and column preparation) with values below 1.6 microg/mL and 7.2%, respectively. The p…
In-tube solid-phase microextraction coupled by in valve mode to capillary LC-DAD: Improving detectability to multiresidue organic pollutants analysis…
2009
Abstract A simple and fast capillary chromatographic method has been developed to identify and quantify organic pollutants at sub-ppb levels in real water samples. The major groups of pesticides (organic halogens, organic phosphorous, and organic nitrogen compounds), some hydrocarbons (polycyclic aromatic hydrocarbons), phthalates and some phenols such as phenol and bisphenol A (endocrine disruptors) were included in this study. The procedure was based on coupling, in-tube solid-phase microextraction (IT-SPME) by using a conventional GC capillary column (95% methyl–5% phenyl substituted backbone, 80 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve to capillary liquid chromatog…
Chemical degradation products of lignin and humic substances part I Synthesis, structure verification and gas chromatographic separation of chlorinat…
1993
Abstract Chlorinated vanillins (4-hydroxy-3-methoxybenzaldehydes) and syringaldehydes (3,5-dimethoxy-4-hydroxy-benzaldehydes) were synthesized and their purities and structures were examined by quartz capillary gas chromatography and mass spectrometry. The detailed procedures for the synthesis, gas chromatographic separation and mass spectroscopic features are presented.
Lauroyl peroxide as thermal initiator of lauryl methacrylate monolithic columns for CEC
2008
The preparation of lauryl methacrylate (LMA)-based monolithic columns for CEC using lauroyl peroxide (LPO) as thermal initiator of polymerization has been investigated. The influence of initiator amount and composition of porogenic solvent on the physical and electrochromatographic properties of the resulting LMA-based monoliths was evaluated. A comparison with LMA-based columns thermally polymerized with AIBN was performed. At a given porogenic solvent composition, LMA stationary phases initiated with LPO showed higher permeabilities and better efficiency values than those prepared using AIBN as initiator. The optimum polymerization mixture found for LPO initiator provided a minimum plate …
Determination of major carotenoids in vegetables by capillary electrochromatography.
2006
A simple and rapid method for the isocratic separation and determination of carotenoids (carotenes and xanthophylls) in vegetables by CEC is described. The capillary column (100 microm ID, 25 cm effective length) was packed with 3 microm Hypersil ODS particles. The optimized mobile phase contained 60% ACN, 35% THF and 5% of a 5 mM Tris aqueous buffer of pH 8. beta-Carotene, lycopene and lutein were separated with efficiencies of 66 000-128 000 plates/m within a short time (less than 12 min for the last peak eluted, 13/13'-cis-beta-carotene). An excellent resolution of the three carotenoids, as well as partial resolution of their geometrical isomers, was achieved. Application to the determin…
Quantitative analysis of broad molecular weight distributions obtained by matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry
1996
In order to quantify the error of matrix-assisted laser desorption ionisation (MALDI) time-of-flight (TOF) mass spectrometry in the determination of broad molecular weight distributions, different mixtures by weight of two poly(methyl methacrylate) standards were prepared. These mixtures, with well-defined bimodal molecular weight distributions were analysed by MALDI-TOF mass spectrometry using different matrices (2,4,6-trihydroxyacetophenone and 2,5-dihydroxybenzoic acid) and different cations (Li+, Na+, K+, Rb+ and Cs+) for doping the analyte. From the MALDI-TOF mass spectrometric data, the weight fractions of the two polymers of all mixtures were determined and compared to the values mea…
Temperature-Responsive Surface Coatings Based on Poly(methylsilsesquioxane)-hybrid Polymers
2007
The present paper presents a new method to build up temperature-responsive surfaces. First a poly(silsesquioxane)-block-poly(N-isopropyl-acrylamide) (PMSSQ-b-PNIPAM) was successfully synthesized using RAFT polymerization. Spin-coating or dip-coating of PMSSQ-b-PNIPAM onto glass surfaces resulted in temperature-responsive surfaces. Surface ATR FT-IR measurements proofed the successful surface modification using PMSSQ-b-PNIPAM. IR fine structures of PNIPAM and PMSSQ could be assigned, respectively. In capillary rise experiments a change of the meniscus height measured at temperatures below or above LCST was observed, indicating a different wetting behavior. Thus, a simple spin- or dip-coating…
Determining sulfur-containing amino acids by capillary electrophoresis: A fast novel method for total homocyst(e)ine human plasma
1999
A high-performance capillary electrophoresis (HPCE) method based on laser-induced fluorescence detection is presented here. It enables the determination of sulfur-containing amino acids within 15 min. Fluorescence of sulfur-containing amino acids in plasma is linear over a range of 50-150 micromol/L for L-methionine, 5-100 micromol/L for L-homocysteine, and 50-200 micromol/L for L-cysteine. For homocysteine, we were able to detect 1 fmol injected, equivalent to a plasma concentration of 10 nmol/L. A similar sensitivity is present for cysteine, an even lower one being found for methionine. The intra- and interassay relative standard deviations are < 1%. High-performance liquid chromatography…