Search results for "HPLC"
showing 10 items of 201 documents
Resolution of inherently chiral resorcarene derivatives by enantioselective HPLC
1999
Abstract The HPLC enantiomeric resolution of five inherently chiral tetrabenzoxazine derivatives of resorcarenes has been achieved by HPLC using Whelk-Ol and in one case Chiralpak AD as stationary phases. Enantiomeric separation was only observed in a very narrow range of mobile phase compositions. On-column enantiomeric interconversion of a racemic compound with a typical plateau-like elution profile was observed using a Chiralpak AD column
Peptides analysis in blood plasma using on-line system of supported liquid membrane and high-performance liquid chromatography
2005
The potential of using supported liquid membrane (SLM) technique, combined with reversed-phase high-performance liquid chromatography (RP-HPLC) has been investigated for the determination of peptides in human blood plasma. The peptides studied were (DL)Leu(DL)Phe, MetLeuPhe, GlyLeuTyr and ValGluProlleProTyr. The carrier (Aliquat 336) was incorporated in membrane phase in order to facilitate the transport of investigated peptides. After extraction, the analyte-enriched acceptor phase was directly injected into an HPLC system for analysis. With SLM, high selectivity and efficiency were achieved for extraction of peptides in aqueous solutions. Lower extraction efficiency was obtained in plasma…
Separation, isolation and stereochemical assignment of imazalil enantiomers and their quantitation in an in vitro toxicity test
2016
A simple method for the separation of the enantiomers of the fungicide imazalil was developed. Racemic imazalil was separated into its enantiomers with an enantiomeric purity of 99% using HPLC-UV with an enantioselective column (permethylated cyclodextrin) operated in reversed phase mode (water with 0.2% trimethylamine and 0.08% acetic acid and methanol). The absolute configuration of the separated enantiomers was assigned and unequivocally confirmed by optical rotation as well as by vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) combined with ab-initio calculations. The same enantioselective column was also used to develop an HPLC-MS/MS method for the quantifi…
HPLC study on the ‘history’ dependence of gramicidin A conformation in phospholipid model membranes
1989
AbstractA novel HPLC methodology for the study of gramicidin A reconstituted in model membranes has been tested in comparison with circular dichroism data. It is shown that this chromatographic technique not only corroborates most of the recent spectroscopic results but allows one to explain them in terms of mass fractions of different actual conformational species of GA in the phospholipid assemblies. In particular, the dependence of the inserted peptide configuration on the organic solvent and other parameters involved in the ‘history’ of the sample preparation and handling has been analyzed by HPLC in two phospholipid model systems: small unilamellar vesicles and micelles. Moreover, a sl…
Physiological and molecular analysis of the maturation process in fruits of Clementine Mandarin and one of its late-ripening mutants
2009
Peel color is one of the main features affecting citrus quality. Clementine is a widespread citrus species with several mutants showing a delay in pigmentation and harvesting. This work characterizes the fruit development and ripening of two clementine clones, 'Comune', a widespread variety, and one of its natural mutations, 'Tardivo', which differ by a delayed color-break and extended harvest period. Morphological, chemical, and molecular analyses were carried out on fruits of both genotypes during the whole maturation process. Analysis showed that mutation did not affect ripening characteristics such as juice acidity and TSS. However, biochemical and molecular analysis revealed marked dif…
Exploring the apparent properties and Q-markers for quality control of Cornus officinalis
2023
Cornus officinalis Siebold & Zucc. has a high nutritious value and is widely used in food fields. To distinguish the quality of cornus in different areas, this research provided a new strategy for comprehensively evaluating cornus. As a result, 12 iridoid glycosides and 7 polyphenols were identified and quantified by UHPLC-Q-TOF/MS in 13 batches of samples from five different origins. Chromaticity analysis pointed out that pelargonidin-3-O-galactoside, total iridoids, and total polyphenols performed high relation with 1365*. Antioxidant activity and inhibition of α-glucosidase effect correlated with the chemical analysis suggested that iridoid glycosides and polyphenols should represent…
Novel σ1 antagonists designed for tumor therapy: Structure – activity relationships of aminoethyl substituted cyclohexanes
2021
Abstract Depending on the substitution pattern and stereochemistry, 1,3-dioxanes 1 with an aminoethyl moiety in 4-position represent potent σ1 receptor antagonists. In order to increase the stability, a cyclohexane ring first replaced the acetalic 1, 3-dioxane ring of 1. A large set of aminoethyl substituted cyclohexane derivatives was prepared in a six-step synthesis. All enantiomers and diastereomers were separated by chiral HPLC at the stage of the primary alcohol 7, and their absolute configuration was determined by CD spectroscopy. Neither the relative nor the absolute configuration had a large impact on the σ1 affinity. The highest σ1 affinity was found for cis-configured benzylamines…
Advantages of monolithic over particulate columns for multiresidue analysis of organic pollutants by in-tube solid-phase microextraction coupled to c…
2011
Abstract The performance of a monolithic C 18 column (150 mm × 0.2 mm i.d.) for multiresidue organic pollutants analysis by in-tube solid-phase microextraction (IT-SPME)-capillary liquid chromatography has been studied, and the results have been compared with those obtained using a particulate C 18 column (150 mm × 0.5 mm i.d., 5 μm). Chromatographic separation has been carried out under isocratic elution conditions, and for detection and identification of the analytes a UV-diode array detector has been employed. Several compounds of different chemical structure and hydrophobicity have been used as model compounds: simazine, atrazine and terbutylazine (triazines), chlorfenvinphos and chlorp…
Fourier transform infrared determination of imidacloprid in pesticide formulations
2004
A simple method has been developed for Fourier Transform Infrared (FTIR) determination of Imidacloprid in pesticide formulations. Samples were diluted with CHCl3 and the FTIR spectra of samples and standards were obtained at a nominal resolution of 4 cm-1 from 4000 to 900 cm-1 accumulating 25 scans. Imidacloprid determination was based on the measure of either peak area from 1577 to 1567 cm-1 or peak height at 1572 cm-1, both corrected using a horizontal baseline defined at 1900 cm-1. The limits of detection achieved, of the order of 9 µg g-1, were appropriate for the determination of Imidacloprid in commercially available formulations. FTIR results were statistically comparable to those fo…
In-tube solid-phase microextraction and liquid chromatography using a monolithic column for the selective determination of residual ethylenediamine i…
2009
The selective determination of the diamine ethylenediamine (EDA) in the presence of a higher amount of residual dimethylamine in cationic polymers has been developed. The strategy uses both a solution derivatization with a selective agent of primary amines such as o-phthaldialdehyde-N-acetyl-L-cysteine (OPA-NAC) and an in-tube solid-phase microextraction (IT-SPME) coupled to liquid chromatography (LC). A 70 cm long, 0.32 mm internal diameter, and 3 microm thick commercially available capillary column coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane was employed to replace the injection loop of a Rheodyne injection valve. A volume of 1 mL of derivatized sample was passed thro…