Search results for "nitrile"
showing 10 items of 1539 documents
Determination of free formaldehyde in cosmetics containing formaldehyde-releasing preservatives by reversed-phase dispersive liquid-liquid microextra…
2017
Abstract An analytical method for the determination of traces of formaldehyde in cosmetic products containing formaldehyde-releasing preservatives has been developed. The method is based on reversed-phase dispersive liquid–liquid microextraction (RP-DLLME), that allows the extraction of highly polar compounds, followed by liquid chromatography–ultraviolet/visible (LC–UV/vis) determination with post-column derivatization. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the selected conditions, a mixture of 500 μL of acetonitrile (disperser solvent) and 50 μL of water (extraction solvent) was rapidly injected into 5 mL of toluene sampl…
Characterization of particle morphology of biochanin A molecularly imprinted polymers and their properties as a potential sorbent for solid-phase ext…
2014
Abstract Molecularly imprinted polymers (MIPs) with biochanin A as a template were obtained using a bulk polymerization with non-covalent imprinting approach. The polymers were prepared in acetonitrile as porogen, using ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The synthesis, with an application of 1′,1′-azobis(cyclohexanecarbonitrile) (ACHN) as an initiator, has been performed thermally. During the synthesis process the effect of different functional monomers such as methacrylic acid (MAA), acrylamide (AA) and 4-vinylpyridine (4-VP) was investigated. The application of nitrogen sorption porosimetry, scanning electron microscopy (SEM), and Fourier transform infrared spec…
Assisted baseline subtraction in complex chromatograms using the BEADS algorithm.
2017
The data processing step of complex signals in high-performance liquid chromatography may constitute a bottleneck to obtain significant information from chromatograms. Data pre-processing should be preferably done with little (or no) user supervision, for a maximal benefit and highest speed. In this work, a tool for the configuration of a state-of-the-art baseline subtraction algorithm, called BEADS (Baseline Estimation And Denoising using Sparsity) is developed and verified. A quality criterion based on the measurement of the autocorrelation level was designed to select the most suitable working parameters to obtain the best baseline. The use of a log transformation of the signal attenuate…
Optimised procedures for the reversed-phase liquid chromatographic analysis of formulations containing tricyclic antidepressants.
2003
The chromatographic behaviour (retention, selectivity, peak shape and resolution) of seven tricyclic antidepressants (TCAs), amitryptiline, clomipramine, doxepin, imipramine, maprotiline, nortryptiline and trimipramine, was examined. Conventional unendcapped Cs and C18 columns and an endcapped XTerra MS C18 column recommended for the analysis of basic compounds were used together with acetonitrile-water and micellar sodium dodecylsulfate (SDS)-pentanol mobile phases. The two best combinations were XTerra C18/acetonitrile, which yielded the largest efficiencies and resolution, and C8/SDS-pentanol, which eliminated the peak tails that were still observed with the XTerra C18 column. Both the s…
Reversed phase liquid chromatography for the enantioseparation of local anaesthetics in polysaccharide-based stationary phases. Application to biodeg…
2020
[EN] A comprehensive study on the chiral separation of bupivacaine, mepivacaine, prilocaine and propanocaine with eight commercial polysaccharide-based chiral stationary phases (CSPs) in reversed phase conditions compatible with MS detection is performed. Methanol and acetonitrile are used as organic modifiers. Retention and resolution values obtained for each compound in the different CSPs and mobile phases are compared. The polysaccharide-based CSPs tested present different enantioselectivity towards the analytes. From the results, the experimental conditions for determining the enantiomers of bupivacaine, mepivacaine, prilocaine and propanocaine in saline aqueous samples using MS detecti…
A capillary liquid chromatography method for benzalkonium chloride determination as a component or contaminant in mixtures of biocides
2015
A method for quantifying benzalkonium chloride (BAK), an alkyl dimethyl benzyl ammonium compound, in several biocides formulations is proposed. A tertiary amine like N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine (TA) and a straight-chain alkyl ammonium compound like trimethyl-tetradecyl ammonium chloride (TMTDAC), have been employed as trade surfactants besides BAK. Two capillary analytical columns with different polarities are tested: inertsil CN-3 capillary column (150mm×0.5mm i.d., 3μm particle diameter) and a non endcapped Zorbax C18 capillary column (35mm×0.5mm i.d., 5μm particle diameter). This latter column provided the best separation of the BAK homologues in less than 12min using …
Sample Preparation Improvement in Polycyclic Aromatic Hydrocarbons Determination in Olive Oils by Gel Permeation Chromatography and Liquid Chromatogr…
2005
Abstract The determination of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil samples has been improved in order to obtain a fast methodology with a low limit of detection through the combination of liquid–liquid extraction with acetonitrile and preparative gel permeation chromatography (GPC) prior to the injection of purified extracts into a C18 column. Acetonitrile–water was used as the mobile phase with a gradient from 50 to 95%, w/w, acetonitrile in 30 min. The oven temperature was maintained at 15°C, and fluorometric detection was made at a fixed excitation wavelength of 264 nm and variable, optimal emission wavelength for each analyte ranging from 352 nm for 11-H-benzo(b)fluor…
The sustainable synthesis of levetiracetam by an enzymatic dynamic kinetic resolution and an ex-cell anodic oxidation
2021
Levetiracetam is an active pharmaceutical ingredient widely used to treat epilepsy. We describe a new synthesis of levetiracetam by a dynamic kinetic resolution and a ruthenium-catalysed ex-cell anodic oxidation. For the enzymatic resolution, we tailored a high throughput screening method to identify Comamonas testosteroni nitrile hydratase variants with high (S)-selectivity and activity. Racemic nitrile was applied in a fed-batch reaction and was hydrated to (S)-(pyrrolidine-1-yl)butaneamide. For the subsequent oxidation to levetiracetam, we developed a ligand-free ruthenium-catalysed method at a low catalyst loading. The oxidant was electrochemically generated in 86% yield. This route pro…
1,4-regioselective iodofunctionalizations of 1,3-butadiene
1988
Abstract Addition reactions of benzene and acetonitrile to 1,3-butadiene are described. This new iodofunctionalization process proceeds “via” iodonium ion-allylic cation equilibrium and gives regioselectively 1,4-adducts, which can be alternatively obtained by acid treatment of the 1,2-derivative 8 .
The kinase inhibitor LS104 induces apoptosis, enhances cytotoxic effects of chemotherapeutic drugs and is targeting the receptor tyrosine kinase FLT3…
2008
Activating mutations of FLT3 are found in approximately one-third of acute myeloid leukemia (AML)-cases and are considered to represent an attractive therapeutic target. In this study, we report that the hydroxystyryl-acrylonitrile compound LS104 inhibits proliferation and induces potent cytotoxic effects in FLT3 expressing leukemic cells in vitro. Immunoblot and phosphoprotein-FACS analysis demonstrated inhibiton of phosphorylation of FLT3-ITD and of its downstream targets. In pharmacokinetic studies, a rapid and dose dependent cellular uptake of LS104 lasting up to 11h could be demonstrated. Combination of LS104 with chemotherapeutic agents markedly enhanced cytotoxic effects. Recently, a…