Search results for " High pressure liquid"
showing 10 items of 705 documents
Classification of Extra Virgin Olive Oils Produced at La Comunitat Valenciana According to Their Genetic Variety Using Sterol Profiles Established by…
2009
A method to classify extra virgin olive oils (EVOOs) according to their genetic variety using sterol profiles obtained by high-performance liquid chromatography (HPLC) with mass spectrometry (MS) detection has been developed. Sterol extracts were chromatographed on a dC18 Atlantis column (100x3 mm, 3 microm) with a gradient of acetonitrile/water (0.01% acetic acid) at a flow rate of 1.0 mL min(-1) and positive-ion mode MS detection. Using linear discriminant analysis of the HPLC-MS data (extracted ion chromatograms), EVOO samples belonging to six genetic varieties cultivated at La Comunitat Valenciana, Spain (Arbequina, Borriolenca, Canetera, Farga, Picual, and Serrana), were correctly clas…
Determination of benperidol and its reduced metabolite in human plasma by high-performance liquid chromatography and electrochemical detection.
1991
An isocratic high-performance liquid chromatographic method with electrochemical detection for the quantification of benperidol and its suggested reduced metabolite TVX Q 5402 in human plasma is described. The method included a two-step solid-phase extraction on reversed-phase and cation-exchange material, followed by separation on a cyanopropyl silica gel column (5 microns; 250 mm x 4.6 mm I.D.). The eluent was 0.15 M acetate buffer (pH 4.7) containing 25% acetonitrile (w/w). Spiperone served as internal standard. The inclusion of the cation-exchange step provided sample purity higher than those achieved with other methods. After extraction of 1 ml of plasma, concentrations as low as 0.5 n…
Impact of the post-treatment conditions of parent silica on the silanization of n-octadecyl bonded silica packings in reversed-phase high-performance…
2001
Native mesoporous silica beads were subjected to a sequence of post-treatment procedure including hydrochloric acid treatment, calcination and subsequent rehydroxylation. The post-treated silica beads were converted into RP-18 silica by silanization with monochloro- and dimethoxy-n-octadecylsilanes, respectively. The influence of post-treatments and silanization conditions on the physico-chemical characteristics and on the chromatographic behaviour of the RP-silicas was studied. Also the changes of the pore structural parameters and the silanol group densities during the post-treatment and silanization were assessed.
Chemical reduction of the mycotoxin beauvericin using allyl isothiocyanate.
2011
Abstract Beauvericin (BEA) is a bioactive compound produced by the secondary metabolism of several Fusarium strains and known to have various biological activities. This study investigated the reduction of BEA present in the concentration of 25 mg/kg on a solution model (phosphate buffer saline at pH 4 and 7) and in wheat flour using allyl isothiocyanate (AITC) as a reactant. The concentration of the mycotoxin studied was evaluated using liquid chromatography coupled to the diode array detector (LC-DAD), whereas adducts formed between the BEA and AITC were examined by liquid chromatography coupled to mass spectrometry-linear ion trap (LC-MS-LIT). In solution, BEA reduction ranged from 20% t…
Rapid and simultaneous high-performance liquid chromatography assay of polyamines and monoacetylpolyamines in biological specimens
2000
A rapid, resolutive and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for polyamines and acetylpolyamines by adopting pre-column derivatization with benzoyl chloride. In a single run lasting less than 15 min ten polyamines were separated as well as traces of benzoic acid, methylbenzoate and benzoic anhydride. These contaminants, produced during the derivatization reaction, were almost all eliminated by washing steps envisaged in the same procedure. This simple and sensitive method can be applied to routine determination of polyamines in biological samples. A fine application of this procedure to the determination of endogenous content of p…
Application of Dopant-Assisted Atmospheric Pressure Photoionisation HPLC–MS Method for the Sensitive Determination of Polycyclic Aromatic Hydrocarbon…
2017
Multiple food research studies have shown that the polycyclic aromatic hydrocarbon (PAHs) are frequently found in processed cocoa products and chocolate. In a present study a method based on dopant-assisted atmospheric pressure photoionisation (DA-APPI) combined with a liquid chromatography/high-resolution mass spectrometer (HPLC-HRMS) for high-sensitivity analysis of four EU marker PAHs in dark chocolate samples was developed and fully validated according to the performance criteria set in EU guidelines. PAHs detection was achieved by HRMS in positive electrospray ionization mode with toluene used as a dopant to enhance the ionization efficiency of non-polar PAHs. The on-column instrument …
Extraction of polycyclic aromatic hydrocarbons from cookies: a comparative study of ultrasound and microwave-assisted procedures.
2008
The chromatographic determination of 15 polycyclic aromatic hydrocarbons (PAHs) in cookies has been improved in order to obtain a fast method with a low limit of detection through the combination of microwave-assisted extraction (MAE), oil saponification and solid-phase extraction clean-up before the injection of purified extracts in a C18 201TP52 (5 microm, 250 x 2.1 mm) column. Using acetonitrile-water as mobile phase, with a 50% to 95% w/w acetonitrile gradient for a fixed flow of 0.250 ml min(-1), 15 PAHs were separated in 45 min. The column temperature was maintained at 15 degrees C; and fluorimetric detection was made at a fixed excitation wavelength of 264 nm and emission measurement…
Covalent DNA adducts formed by benzo[c]chrysene in mouse epidermis and by benzo[c]chrysene fjord-region diol epoxides reacted with DNA and polynucleo…
1997
The metabolic activation in mouse skin of benzo[c]chrysene (B[c]C), a weakly carcinogenic polycyclic aromatic hydrocarbon (PAH) present in coal tar and crude oil, was investigated. Male Parkes mice were treated topically with 0.5 mumol of B[c]C, and DNA was isolated from the treated areas of skin at various times after treatment and analyzed by 32P-postlabeling. Seven adduct spots were detected, at a maximum level of 0.89 fmol of adducts/microgram of DNA. Four B[c]C-DNA adducts persisted in skin for at least 3 weeks. Treatment of mice with 0.5 mumol of the optically pure putative proximate carcinogens (+)- and (-)-trans-benzo[c]chrysene-9,10-dihydrodiols [(+)- and (-)-B[c]C-diols] led to th…
Characterization of gramicidin A in an inverted micellar environment. A combined high-performance liquid chromatographic and spectroscopic study
1992
We have investigated the conformational adaptability of gramicidin A incorporated into reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water, a so far unexplored "host" membrane-mimetic model system for this peptide. A high-performance liquid chromatographic strategy previously developed for the study of gramicidin in phospholipid vesicles and normal micelles [Bañó et al. (1989) FEBS Lett. 250, 67; Bañó et al. (1991) Biochemistry 30, 886] has been successfully extended to this system. The method has permitted the separation of peptide conformational species, namely, double-stranded dimers and monomers, and an accurate quantitation of their proportion in the invert…
Conformational transitions of gramicidin A in phospholipid model membranes. A high-performance liquid chromatography assessment.
1991
We have investigated the conformation of gramicidin A reconstituted in different phospholipid environments, small unilamellar vesicles, extensive bilayers, and micelles by exploiting a recently proposed experimental approach based on high-performance liquid chromatography [Bano et al. (1988) J. Chromatogr. 458, 105; Bano et al. (1989) FEBS Lett. 250, 67]. The method allows the separation of conformational species of the peptide namely, antiparallel double-stranded (APDS) dimers and β 6.3 -helical monomers, and quantitation of their proportions in the lipid environment. Various experimental parameters (e.g., nature of organic solvent, time of incubation in organic solvent, lipid-to-peptide m…