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1.
Summary Polymethyloctylsiloxane-coated stationary phases have been prepared for liquid chromatography, by thermal reaction. The influence of the reaction conditions on retention and efficiency of test substances with different structures has been discussed. The materials have good stability in both acidic and basic eluents. 相似文献
2.
Summary A general equation for the final retention of a solute chromatographed under conditions of stepwise gradient elution has been
derived. The elution process and the distances travelled by solutes as a function of eluent volume were simulated by computer
for the optimization of stepwise gradient prorams from isocratic HPLC data. The validity of the equations was experimentally
veritied. 相似文献
3.
Summary Lansoprazole is a new inhibitor of gastric proton secretion. An HPLC method for the quantitative determination of lansoprazole
in serum is described. The method consists of liquid-liquid extraction and enrichment of the analyte and subsequent reverse-phase
liquid chromatography with UV detection. The method is specific, sensitive and practical. It has been applied to serum from
healthy volunteers.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
4.
Summary A very rapid, sensitive and reproducible HPLC method was developed for simultaneous determination of eight anti-epileptic
drugs (AEDs): lamotrigine, primidone, ethosuximide, sulthiame, felbamate, phenobarbital, carbamazepine, phenytoin and oxcarbazepine-metabolite
(10-hydroxy-carbazepine) in human serum. Sample purification requires only protein precipitation with an appropriate reagent.
Separation was by reversed-phase HPLC, using a C18 column, 20% acetonitrile and 40 mM phosphoric acid buffer as mobile phase.
Column temperature was set at 50°C, and measurement was by UV detection at 205 nm. The inter and intra-assay coefficients
of variation (CV) ranged 1.13–7.10% and 1.14–8.49%, respectively. The absolute (measured) and relative (analytic) recoveries
of the drugs ranged 96.7%–104.4% and 97.3%–106.1%, respectively. No interference with other common antiepileptic drugs and
analgesics were observed. The method requires only 100 μl serum or less. It is very fast (sample preparation and analysis
time approx. 23 min for all 9 AEDs), and suitable for routine clinical use, especially for epileptic patients on polytherapy. 相似文献
5.
A study of ten silica-based stationary phases and gradient elution conditions to separate dietary folates by reversed-phase HPLC was performed. Alkyl-bonded stationary phases (both conventional and alternative) were found to be the most promising for the separation of different folate monoglutamates in terms of selectivity and peak shape. These phases were better than phenyl-bonded phases which lacked selectivity when separating 10-formyl-folic acid and 5-formyl-tetrahydrofolate. Polar-bonded (cyano) stationary phase showed similar retention characteristics as the conventional alkyl-bonded phases, but ranked below those in terms of peak shape. Overall, alternative stationary phases exhibited slightly higher retention of late-eluted folates and greater retention variability for early-eluting tetrahydrofolate and 5-methyl-tetrahydrofolate. Best selectivity was achieved on alternative polar endcapped Aquasil C18 followed by conventional Synergy MAX C12 and Genesis C18 stationary phases. 相似文献
6.
B. T. Mathews A. E. Beezer M. J. Snowden M. J. Hardy J. C. Mitchell 《Chromatographia》2000,53(3-4):147-155
Summary The reversed phase chromatographic properties of the [G1]-L-glutamic and ethyl ester-AC-silica (1), [G2]-L-glutamic acid ethyl ester-AC-silica (2) and the [G1]-L-glutamic acidt-butyl ester-AC-silica (3) dendrimer stationary phases were evaluated. Initial studies involved the comparison between these phases with a classic
reversed phase (i.e. ODS1) by the separation of a standard reversed phase test mixture composed of dimethylphthalate, nitrobenzene,
anisole, diphenylamine and fluorene. Separations were achieved with comparable performance to those obtained with the conventional
reversed phase (ODS1). However, it was apparent that the chromatographic selectivity exhibited by the dendrimer stationary
phases was different from that of the ODS1 phase. On a per mole basis, the dendrimers exhibited similar (and sometimes greater)
affinity for these analytes compared with the ODS1 ligand. Subsequent chromatographic experiments were conducted upon the
dendrimer chiral stationary phases using chiral analytes under reversed phase and normal phase conditions. Chiral resolution
was not observed. 相似文献
7.
Summary The mechanism of separation of solutes under gradient elution conditions has been studied. Separation of a mixture of soybean
phospholipids (phosphatidylethanolamine, phosphatidylinositol, and phosphatidylcholine) in the ternary mobile phase: methanol,
hexane, isopropanol was considered as an example. An analytical expression in terms of the composition of the ternary mobile
phase was obtained to calculate retention factors in two-step gradient modes. The following new polynomial equation was derived:
logk=A+BF+CF
2+DG+EG
2 where A, B, C, D, and E are empirical coefficients; F and G are volume fractions of isopropanol and methanol respectively
in the mobile phase based on hexane. The coefficients for phospholipids were obtained under gradient conditions. 相似文献
8.
Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using a common empty flow cell. 相似文献
9.
Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in
liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the
flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing
to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced
for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were
improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using
a common empty flow cell. 相似文献
10.
Summary A computer-assisted method is presented for the optimization of separation in gradient elution reversed-phase HPLC. The method is based on a polynomial estimation from nine preliminary experiments according to a two-factor (initial solvent composition C and gradient time T) rectangular design. This is followed by a two-dimension computer scanning technique. Resolution is used as the selection criterion. Good agreement was obtained between predicted data and experimental results. 相似文献
11.
Summary The employment of three chiral stationary phases (CSPs) obtained by derivatizing γ-mercaptopropyl-silanized silica gel with
quinine, quinidine and N-methyl-quinium iodide, for the separation of organic racemates, is presented. They are quite useful
in the resolution of alkylarylcarbinols, binaphthyl derivatives, amides and other substances of pharmaceutical interest. 相似文献
12.
Summary A fast and easy, iscratic high-performance liquid chromatographic method for the simultaneous determination of primidone, phenobarbital, phenytoin, carbamazepine and thiobutabarbital from serum samples has been developed. The optimal eluent composition is 36% acetonitrile, 24% methanol and 40% phosphate buffer. Using a programmable wavelength detector very low (sub-therapeutic) levels of the drugs can be measured. 相似文献
13.
Summary A gradient delivery system for microbore and open tubular liquid chromatography is described. A gradient mixing vessel of 5–100l, or 25–1000l allows the generation of binary gradients with high reproducibility. The suitability of the system for short packed micro bore columns and open tubular columns is demonstrated. 相似文献
14.
Summary A new and simple HPLC method is described for the separation and quantitative determination of the (+)-and (−)-enantiomers
of lansoprazole. The analytes were extracted from serum as previously described for whole lansoprazole [K. Borner, Chromatographia
45, 450–452 (1997)]. The enantiomers were separated by chromatography on a CHIRAL-AGPR column which contained covalently bound acid α1-glycoprotein as chiral selector. In the pure drug the (−)/(+) ratio was 0.99:1.01. In serum of twelve human volunteers the
concentration of the (−)-enantiomer was 3 to 5 times higher than that of the (+)-enantiomer. Both enantiomers differ remarkably
in their pharmacokinetics. 相似文献
15.
Summary In this work, an optimization procedure for gradient RPLC separation, using ternary mobile phases, is described. This procedure requires eight preliminary experiments in gradient elution mode to predict the retention surface for each solute over the whole triangular space. This is followed by computerized calculations to determine the best ternary gradient elution profile with respect to both selectivity and analysis time. The efficiency of this procedure from the point of view of rapidity and of accuracy, is illustrated for the specific separation of twelve phenyl urea herbicides. 相似文献
16.
D. Ishii Y. Hashimoto H. Asai K. Watanabe T. Takeuchi 《Journal of separation science》1985,8(9):543-546
A simple gradient method for capillary column and micro high performance liquid chromatography using either single or multiple mixing chambers is presented. The gradient profile is dependent on the number of the mixing chambers. This system permits solvent gradient elution at flow rates less than 10 μl/min with satisfactory reproducibility. 相似文献
17.
Summary A general chromatographic model has been set up starting from a set of equations based on the concept of the velocity of a
solute along the column. The composition of the mobile phase is taken into account solely as a numerical factor entering into
suitable equations and totally independent of the chemical-properties of the constituents. A few isocratic experimental runs
are necessary as input data, and subsequently a small amount of computational effort is sufficient to make predictions of
retention times under gradient elution conditions for solutes of whatever chemical structure. The prediction errors are dependent
on the steepness of the linear gradient chosen but are, in any case, acceptably low. 相似文献
18.
Summary A method of reserved-phase HPLC analysis for mixtures of triglycerides (TG's) that provides good resolution at acceptable
analysis times for high-ECN TG's has been developed. An elution gradient of methyltert-butyl-ether (MTBE) in acetonitrile
(ACN) was used with an ultraviolet detector operated at 215nm. The effect of the proportion of MTBE in the mobile phase, gradient
time, temperature and sample solvent on TG retention and resolution was studied. Linear relationships were derived between
the logarithm of the capacity factor (log k'), and the logarithm of selectivity (log α) and the above-mentioned chromatographic
factors. The conditions selected were: an elution gradient of from 23 to 30% MTBE, an elution gradient time of 25 minutes,
and a temperature of 30°C, which provided good resolution of soybean oil TG's in less than 30 minutes. 相似文献
19.
Summary A method is described for the preparative HPLC of up to 50mg of carotenoid using a self-packing axially-compressed column.
Oxygenated carotenoids, xanthophylls, are separated with silica as the stationary phase and acetone/petroleum ether as the
mobile phase, while carotenes are separated using magnesium oxide/polyamide as the stationary phase and undiluted petroleum
ether as the mobile phase. 相似文献
20.
Summary A simplex method for determining the constantsS andk
o from the equation lnk’=lnk
o−S ϕ (was developed and applied to the reversed phase separation of high molar mass polystyrenes using gradients of any curvature.
Experimental retention times described using the equation had a standard deviation of 1.1%. The inclusion of a quadratic term
in the equation was found to be unwarranted. BothS and lnk
o varied linearly with ln molar mass. The logarithm of peak width of an eluting polystyrene peak was found to be a linear function
of the mobile phase composition at elution. The slope was equal toS. 相似文献