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1.
Summary The influence of different reversed-phase packings and the addition of acidic modifiers to the mobile phase was observed on
the separation of basic and neutral polypeptide antibiotics by gradient elution. A dependence of pore size, coverage, reaction
type and endcapping of the packings was not observed. Nevertheless, not all reversed-phase packings were suitable for the
separation of polypeptides, especially of basic molecules. The addition of phosphoric or perchloric acid to the mobile phase
prevented adsorption of the basic polypeptide antibiotics on the stationary phase. 相似文献
2.
Summary A reversed-phase high performance liquid chromatographic method on C-18 bonded silica is described for the separation of trisubstituted iodo/bromothyronines, which exert thyroid hormone activity. The composition of the mobile phase has been systematically optimized resulting in a ternary mixture of methanol/acetonitrile/water acidified with trifluoroacetic acid. The applicability of ultraviolet absorption detection, amperometric detection and off-line radioimmunoassay was investigated. The latter method allows detection of the different iodo/bromothyronines down to 40–120 ng/l mobile phase; this sensitivity is high enough for application to thyroid hydrolysates in order to clarify the question as to whether bromine can substitute iodine in the biosynthesis of thyroid hormones. 相似文献
3.
Summary Two simple methods were developed for the simultaneous determination of six alkaloids (ephedrine, pseudoephedrine, norephedrine,
norpseudoephedrine, methylephedrine and methyl-pseudoephedrine) inEphedrae Herba by high-performance liquid chromatography. The first method was carried out by using a Cosmosil 5C18-MS column with a gradient solvent system consisting of a phosphate buffer and acetonitrile, and detection at 210 nm. The
contents of alkaloids in non-pretreated ephedra herb extracts could be determined easily in 50 min. Alternatively, the alkaloids
could be determined within 35 minutes by using a Cosmosil 5C18-MS column with an isocratic solvent system of a sodium dodecyl sulfate-acetonitrile solution. The two methods are compared
and discussed. 相似文献
4.
Summary The separation of fullerenes with a monomeric octadecylsilica bonded phase using n-hexane or toluene/methanol mobile phase systems is described. Analytical and preparative separations, incorporating on-line UV/VIS spectral measurements, confirmed the existence of large fullerenes such as C76, C78 and C84. However, isomers of C78 and C84 were not conclusively found. 相似文献
5.
Summary In addition to their value in the nutritional context, the carotenoids have other important functions, including some epidemiological
significance in disease prevention. With increasing interest in the carotenoids methods for their characterization and quantification
in various matrices are essential particularly with regard to epidemiologic studies dealing with diet and health. Since high-performance
liquid chromatography (LC) is the most promising analytical method for this purpose, having high reliability, high selectivity
and quantification ability, this work presents the evaluation of reversed-phase LC methods using polymeric and monomeric octadecylsilica
(ODS) stationary phases for the highly selective separation of carotenoids. It has been found that the polymeric ODS has a
better selectivity for carotenoids, taking account of their molecular shape and size recognition, than the monomeric ODS phase
and that the former is more suitable than the latter for separations of the carotenoids. 相似文献
6.
Summary An RP-HPLC procedure which separates chlorophylls and their degradation products is described. By employing an amonium acetate buffered mobile phase and a linear gradient elution, complex mixtures of chloroand phaeopigments are separated in less than 30 minutes. The method has been applied to the control of chlorophyll enzymatic degradation in cultures of two algal species, and has also been successfully used in the analysis of algal xanthophylls. 相似文献
7.
B. Dalmadi Kiss K. Balogh Nemes I. Ürmös J. Szúnyog I. Klebovich 《Chromatographia》2000,51(1):S217-S220
Summary A new sensitive HPLC-UV method has been developed and validated for the determination of amboroxol in dog plasma enabling
the investigation of a newly developed 75 mg ambroxol-containing retard capsule of EGIS Pharmaceuticals Ltd., Budapest, Hungary.
A gradient method was used for removing the longer retained plasma components of no interest. The separation was performed
on a BDS Hypersil C18 (5 μm, 250×2.1 mm) analytical column, supplied with a 10 mm guard column containing the same packing
material. The detection was performed at 210 nm. The calibration curve was linear in the range 25–2000 ng·mL−1. Nerisopam (EGIS-6775) was used as internal standard.
Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
8.
Summary Twelve triterpenes were isolated from the alcoholic extract ofMentha villosa as their acetyl methyl ester derivatives. This vegetal specimen, which was collected in the Horto de Plantas Medicinais da
Universidade Federal do Ceará, Fortaleza, Brazil, is used as popular remedy in the treatment of amebiasis, giardiasis and
shistosomiasis. The separation and purification of the triterpenoid derivatives from complex mixtures of closely related isomeric
triterpenoid acids has been performed successfully by reversed-phase HPLC. 相似文献
9.
Summary A reversed-phase high-performance liquid chromatographic method for the determination of chloride in plasma, urine, saliva, sweat and aqueous solution is described. Chloride, in solution in aqueous acetone, is converted by means of pentafluorobenzyl bromide into pentafluorobenzyl chloride. This derivative is separated on a ODS-5 m reversed-phase column using isocratic elution with acctonitrile/water, 50/50, v/v, at a flow rate of 2.0 ml/min, and detected by a UV detector at 264 nm. The method is rapid, accurate and sufficiently sensitive for the determination of chloride in less than 10 l sample volume of a biological fluid. 相似文献
10.
Summary High-performance liquid chromatography with diode-array detection has been used for the separation and quantitation of phenolics
from fresh and processed green beans. Whole beans, pods and seeds of green beans were studied separately. Chromatographic
profiles from pods were more complex than those found in seeds. Flavonol glycosides were confined to quercetin and kaempferol
classes and they were typical of external parts of the fruit. Flavan-3-ols monomers ((+) catechin and (−) epicatechin) as
well as procyanidins structures were identified in pods and seeds. Chromatographic profiles from processed beans revealed
a polyphenolic composition similar to those found in pod fresh green beans. The chromatographic method was carefully validated
in regard to precision and accuracy. High reproducibility of peak area (RSD<3%) and calibration slopes (RSD<4%) was obtained.
Recoveries between 94–104% revealed good accuracy for the overall method. Application to quantitative determination in a representative
number of samples allowed good knowledge of the phenolic composition of green beans (Phaseolus vulgaris v.vulgaris). 相似文献
11.
12.
Modelling and prediction of retention in high-performance liquid chromatography by using neural networks 总被引:1,自引:0,他引:1
Y. L. Xie J. J. Baeza-Baeza J. R. Torres-Lapasió M. C. García-Alvarez-Coque G. Ramis-Ramos 《Chromatographia》1995,41(5-6):435-444
Summary Multi-layer feed-forward neural networks trained with an error back-propagation algorithm have been used to model retention
behaviour of liquid chromatography as a function of the composition of the mobile phases. Conventional hydro-organic and micellar
mobile phases were considered. Accurate retention modelling and prediction have been achieved using mobile phases defined
by two, three and four parameters. With micellar mobile phases, the parameters involved included the concentrations of surfactant
and organic modifier, pH and temperature. It is shown that neural networks provide a competitive tool to model varied inherent
nonlinear relationships of retention behaviour with respect to the mobile phase parameters. The soft models defined by the
weights of the networks are capable of accommodating all types of linear and nonlinear relationships, neural networks being
specially useful when the relationships between retention behaviour and the mobile phase parameters are unknown. However,
to train neural networks more experimental points than with hard-modelling methods are required, hence the use of the networks
is recommended only for those cases where adequate theoretical or empirical models do not exist. 相似文献
13.
M. A. Garcia C. Solans A. Calvo M. Royo E. Hernandez R. Rey M. A. Bregante 《Chromatographia》2002,55(7-8):431-434
Summary A sensitive HPLC method has been developed for determination of ofloxacin (OFL) in biological fluids. Sample preparation was
performed by adding phosphate buffer (pH 7.4, 0.1m) then extraction with trichloromethane. OFL and the internal standard, sarafloxacin (SAR), were separated on a reversed-phase
column with aqueous phosphate solution-acetonitrile, 80∶20, as mobile phase. The fluorescence of the column effluent was monitored
at λex 338 and λem 425 nm. The retention times were 2.66 and 4.24 min for OFL and SAR, respectively, and the detection and quantitation limits
were 8 and 15 ng mL−1, respectively. Plots of response against ofloxacin concentration were linear in the range 8 to 2000 ng mL−1. Recovery was 92.9% for OFL. 相似文献
14.
H. Hosotsubo 《Chromatographia》1988,25(10):887-890
Summary A high-performance liquid chromatographic method for the analysis of thiopental in 100l of human serum or plasma is described. The procedure involves protein precipitation with acetonitrile. The supernatant is directly injected into a chromatograph containing a reversed-phase CLC-ODS (Shimadzu) column. A 5050 (v/v) mixture of water-acetonitrile, at a flow-rate of 1.0ml/min is used as the mobile phase. Detection is carried out ata wavelength of 280nm. Total analysis time per sample is 10min. The assay was found to be linear in the range of 0.1 to 120g/ml. Reproducibility was good, with intra-assay coefficients of variation from 1.780 to 3.208% and inter-assay coefficients of variation from 3.241 to 4.860%. The absolute recoveries were 97.4 to 101,4%. Other drugs were tested for potential interference with the assay, but none was found. 相似文献
15.
Summary The effect of column temperature, especially at low temperatures, on the separation of fullerenes on monomeric and polymeric octadecyl silica (ODS) bonded phases has been studied. Decreasing the column temperature induces an increase in selectivity. The best temperature for the separation of fullerenes was determined for both types of ODS phase with n-hexane eluent. The selectivity for higher fullerenes on monomeric phases becomes similar to that on polymeric phases to low temperature. It has been found that as the carbon content of monomeric phases is increased, the selectivity also becomes similar to polymeric phases. 相似文献
16.
Summary A high-performance liquid chromatographic procedure for the isolation of azadirachtins A, B, D, H and I is described. While azadirachtins A, B, and D are already known, azadirachtins H and I have been isolated for the first time from neem kernels. 相似文献
17.
Summary Pig brain NAD glycohydrolase immobilized on Affi-Gel 10 or nylon 6 was used for the conversion of NAD into 3-acetylpyridine
adenine dinucleotide (APAD) or 3-aminopyridine adenine dinucleotide (AAD).
A reversed-phase chromatographic system consisting of a C18 Resolve column and phosphate buffer (pH 6.2)-methanol as the mobile phase was used to monitor the production of APAD and
AAD. 相似文献
18.
Summary The enantiomers of diphenylalanine (DPA) were well separated by chiral HPLC and NMR spectroscopy on the chiral stationary
phase (CSP) derived from (18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA). The chromatographic parameters such as separation
factors and retention times were greatly influenced by the mobile phase conditions. The (+)-18-C-6-TA used in the CSP was
also employed as a chiral solvating agent for the enantiodiscrimination of the DPA enantiomers by NMR spectroscopy. The proton
of the DPA analyte showing the chemical shift nonequivalences was used in determining the enantiomeric composition of the
analyte. 相似文献
19.
M. A. Campanero A. Lopez-Ocariz E. García-Quetglás B. Sádaba A. de la Maza 《Chromatographia》1998,47(7-8):391-395
Summary An HPLC method has been developed for the quantification of rantidine in plasma for pharmacokinetic studies. Metoclopramide
was used as internal standard. The method uses a simple and rapid sample clean-up procedure involving single-step extraction
with organic solvent to extract ranitidine from plasma. After evaporation and reconstitution the samples are chromatographed
on a 250 mm×4 mm base-stable reversed-phase column with 0.05 M ammonium acetate-acetonitrile, 75∶25 (v/v) as mobile phase and UV detection at 313 nm. The calibration graph was linear for quantities of ranitidine between 10 and
2000 ng mL−1. Intra- and inter-dayCV did not exceed 11.64%. The quantitation limit was 10 ng mL−1 for human plasma. The applicability of this method for pharmacokinetic studies of ranitidine after oral administration are
described. Approximately 90 samples can be processed in 24 h. 相似文献
20.
Fast determination of tetracycline antibiotics in different media by high-performance liquid chromatography 总被引:1,自引:0,他引:1
A. Aszalos 《Chromatographia》1985,20(5):313-322
Summary The use of high-performance liquid chromatography (HPLC) for the identification and determination of tetracycline antibiotics is reviewed. HPLC chromatograms provide fast identification by retention time, tR, and precise quantitation by measurement of peak height or peak area. For separation of tetracycline compounds, most HPLC methods use reversed-phase C18 or C8 columns and UV detection. The HPLC solvent system should have a pH of about 6 to prevent steric changes in the tetracycline molecule. For accurate quantitation it is necessary to avoid tailing and this is accomplished by adding a zwitter ion to the solvent system. Methanol and acetonitrile are frequently used as organic modifiers in these solvent systems. In a single analysis, HPLC methods can be used to separate as many as nine or ten commercially used tetracycline compounds and to determine four to five tetracyclines in commercial tetracycline preparations or in biological fluids. 相似文献