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1.
P. L. Zhu 《Chromatographia》1985,20(7):425-433
Summary In RPLC the dead volume can be defined as the difference between the maximum column hold-up volume and the volume of the adsorbed phase. The composition of the adsorbed phase depends on the composition of the mobile phase and therefore, the dead volume also varies with it. In this work, the alkyl bonded phase acetonitrile (ACN)-water mobile phase system is investigated. In the system, deuterated water (D2O) and deuterated acetonitrile (D-ACN) are retained due to the isotopic dilution effect. By means of D2O and D-ACN, the absolute adsorption isotherm of the organic modifier ACN is measured. Based on the isotherm, the chromatographic behaviour of ACN, D-ACN and D2O, the variation of the dead volume with the composition of the mobile phase, and the approach to determine the maximum column hold-up volumn are explained. In addition, the various approaches to determine the dead volume are compared and the recommendations are given for the case of common unbuffered binary systems (MeOH/H2O, THF/H2O and ACN/H2O). 相似文献
2.
用热分析技术TG-DTA(thermal gravimetric and differential thermal analysis)测定浆料中碳化硅粉体对分散剂聚乙二醇PEG(polyethylene glycol)的吸附量. 结果显示PEG在Ar气氛中411.5 ℃时完全分解; 碳化硅表面分散剂PEG的吸附量随着pH的增大而下降, 在较高pH下大多数分散剂仍存在于溶液中; 分散剂PEG的吸附量通过公式(1)进行计算. 该方法简单方便, 可以应用于测量氧化物或非氧化物吸附紫外-可见分光光度法不能测定的一些有机聚合物分子. 相似文献
3.
Summary In this paper, we report and discuss the adsorption isotherms of hydro-organic mixtures and of compounds used as mobile phase
in reversed phase and normal phase high performance liquid chromatography (RP-HPLC and NP-HPLC, respectively). This work is
the first attempt to study the solid-liquid interface between two types of chromatographic silica surfaces and pure organic
adsorbates from water and from organic eluents by HPLC. Frequently, among the dynamic techniques the method of choice for
the measurement of an adsorption isotherm is frontal analysis. We suggest here the combination of the technique based on peak
asymmetry calibration and peak profiles, which allows calculations directly from integration data. The group of systems studied
permits the analysis of the intermolecular interactions on the silica surface. Particular attention was given to the system
methanol-water and the measurement of the adsorption ofn-octanol from methanol on RP-silica was also carried out. 相似文献
4.
Summary A process to synthesize silica and titania as spherical packing materials has been investigated on the laboratory scale by the sol-gel method. The silica and titania obtained were tested under normal-phase separation conditions for comparison of their retention characteristics silica witha a commercial. The silica was found to be similar in its retention behaviour to the commercial silica. The titania showed basic properties and strongly retained acidic compounds. 相似文献
5.
Summary A method for the quantitative analysis of the organochloro-pesticides heptachlor, dieldrin, DDT and aldrin in water, using the HPLC technique of on-line trace enrichment, has been developed. A standard HPLC isocratic analytical system was employed the principle modification being the incorporation of a short pre-column across the sample loop connections of a Rheodyne 7125 valve to serve as the trace enrichment column. Pesticide recoveries of >95% were achieved at sample flow rate of 5–15 ml/min by employing stainless steel fittings throughout the system and with 5% methanol included in the pesticide sample reservoir. The pesticides were concentrated onto a 50 mm, 10 m Spherisorb ODS column; analysis was performed on a 25 cm, 5 m Spherisorb ODS column with methanol-water (7525) elution; detection was by UV absorption measurement at 220 mm and 0.64 AUFS.Resolution achieved was >=1.16 and selectivity >=1.14. 100 ml aqueous samples allow ppb detection of the named pesticides in real samples. Total analysis time including concentration and chromatography was less than 30 minutes. 相似文献
6.
Elhossein A. Moawed 《Chromatographia》2008,67(1-2):77-84
The effect on polyurethane foam (PUF) of washing with different concentrations of HCl (1, 3, 6, or 11.8 M) has been studied.
After washing, PUF was characterized by use of different techniques. The adsorption properties of PUF and its chromatographic
behavior in the separation and preconcentration of gold from thiocyanate solution were investigated by batch and dynamic processes.
Uptake of Au(III) was maximum after washing with 0.05–0.2 M HCl. The kinetics of adsorption of the Au(III) were found to be
rapid; the average half-live of adsorption (t
1/2) was 60 s. Average values of the thermodynamic quantities ΔH and ΔG were −40.7 and −5.9 kJ mol−1, respectively. These data indicate that adsorption of Au(III) by white PUF proceeds via both weak anion exchange and an ion-association
mechanism. PUF was verified as a good adsorbent by determination of Au(III) in spring water and in gold alloy samples. 相似文献
7.
M. del Olmo A. Garballo M. Nimer I. López J. A. de Ferrer J. L. Vílchez 《Chromatographia》2004,60(3-4):157-164
Linear alkylbenzenesulfonates (LAS) are used extensively as surfactants in consumer formulations as a complex mixture of homologues and isomers. Separation of homologues and isomers of LAS is important in industrial and environmental samples in order to establish their behaviour. Here we present a HPLC methodology with fluorescent detection (FD) for the determination of the homologues and isomers as well as the sum of LAS present. The quantification of total LAS was achieved without a column, using the liquid chromatograph as a FIA system. The different homologues were separated using a Lichrospher-100 RP-8 column of 125 × 4 mm using a linear gradient of methanol and 30.0 mM sodium dodecyl sulphate (SDS), increasing the methanol content linearly from 55% to 70% in 16 min. The resolution of isomers was carried out by using two coupled Lichrospher-100 RP-18 columns of 250 × 4 mm. Elution of isomers was done with a gradient of flow rate from 1.0 to 0.25 mL min–1 using a linear gradient of acetonitrile and 5.0 mM SDS increasing the acetonitrile content linearly from 20% to 40% in 160 min. The methods were validated and applied satisfactorily to the determination of LAS in urban wastewater and ground water. 相似文献
8.
Summary The silica-supported comb-shaped polymer (Sil-ODA18) with a “crystalline-to-isotropic” phase transition showed the characteristic behaviors of both polymeric and monomeric ODS
phases. This was examined using a SRM 869 test mixture. Furthermore, Sil-ODA18 exhibited a specific selectivity towards the critical pairs of polycyclic aromatic hydrocarbons (PAHs), such as acenaphthene
and fluorene, or benz(a)anthracene and chrysene, or benzo(ghi)perylene, indeno(1,2,3-cd)pyrene and dibenz(a,h)anthracene.
The separation of these solutes was controlled by selecting temperature and solvent systems. The selectivity on Sil-ODA18 was also compared with a conventional ODS (octadecylsilyl silica gel) column. The selectivity on a Sil-ODA18 matrix is attributable to an orientation change of the long-chain alkyl substituents on the surface of the silica base material
on transition from crystalline to isotropic state. 相似文献
9.
A. K. Chatjigakis Ph. J. P. Cardot A. W. Coleman H. Parrot-Lopez 《Chromatographia》1993,36(1):174-178
Summary In the course of systematic studies on the solubility, hydrophobicity and complexation properties of cyclodextrins and modified cyclodextrins, the retention behavior of , , and of some glycosylated cyclodextrins has been examined by means of reverse phase HPLC. Mobile phase mixtures containing large amounts of water have been used because of the possible application of such systems to biological studies. Mobile phase mixtures with both methanol and acetonitrile show a linear relationship between the volume fraction of the organic part of the mobile phase and the logarithm of the capacity factor. The extrapolation of capacity factors to a total aquous system are used and compared to other techniques (including solubility) in order to evaluate the hydrophobic properties of the cyclodextrins. In particular, the solubility of cyclodextrins has been explored for a wide range of organic solvent/water mixtures. Whilst cyclodextrins are definitely the most hydrophobic, followed by glycosylated cyclodextrins, the others behave differently in the two mobile phase systems. The differences observed in the results are related to the chemical nature of the organic phase. Comparisons between chromatographic and solubility methods are given and interpretations are proposed. Some cyclodextrins have been modified to increase or modify not only the hydrophobicity but also the solubility, the complexation and the molecular recognition of drugs. The most important aim of this study was to define conditions and rules for further drug vectorization by cyclodextrin-drug complexation. 相似文献
10.
Summary The ability of titania to recognize the position of hydroxyl groups was previously found to result from the formation of a
chelate ring between a titanium ion and the two oxygen atoms of the hydroxyl group and carboxylate anion of 2-hydroxycarboxylic
acids. We investigated how titania could recognize the position of hydroxyl group of monosaccharides and disaccharides. The
retention behavior of monosaccharides and disaccharides on titania was found to be characteristic. Thus, sucrose was eluted
much faster than the other sugars, whereas D-ribose, D-fructose and L-sorbose were most strongly retained on titania of all
of the sugars tested. It is apparent that the sugars strongly retained on titania have an axial hydroxyl group or neighboring
hydroxyl groups of the same conformation. 相似文献
11.
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
12.
Analysis of azines and diazines by HPLC on bonded alkyl stationary phases. Pyridine and quinoline in environmental samples 总被引:1,自引:0,他引:1
Summary Several heterocyclic compounds have been investigated by HPLC on RP-8 and RP-18 with methanol-water mixtures as mobile phase.
The chromatographic systems developed showed good selectivity for determination of azines and diazines. Pyridine and quinoline
have been determined in environmental samples and in food. Samples for analysis were preconcentrated by solid phase extraction
on-column with octadecyl silane packing. 相似文献
13.
J. López-Cervantes D.I. Sánchez-Machado P. Paseiro-Losada J. Simal-Lozano 《Chromatographia》2003,58(5-6):327-330
Summary The effects of compression, stacking, vacuum packing and temperature on the migration of bisphenol A from polyvinyl chloride plastic sheeting into European Union food simulants (water, 3% acetic acid and olive oil), 1.5% agar, and mixtures of olive oil with various proportions of inert material (fine washed sea sand) were evaluated using previously developed methods for identification and quantitation of migrants. Compression, stacking and increasing temperature all increased migration.Presented at the International Symposium on Separation and Characteristics of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, February 5–7, 2003 相似文献
14.
Summary The use of HPLC-NMR-MS for the detection and identification of the metabolites of ibuprofen present in a solid phase extract
of human urine is described. Gradient reversed-phase HPLC was used to separate the components present in the extract, which
were then characterised by a combination of stopped-flow1H NMR and on line electrospray-MS. This approach led to the rapid identification of the known phase 1 human metabolites of
ibuprofen, including hydroxy- and carboxy- metabolites, together with their respective glucuronide conjugates. In addition
a probable artefact resulting from the dehydration of one of the side chainhydroxylated glucuronides was also identified. 相似文献
15.
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
16.
Determination of eight penicillins in serum from cattle and pigs by generic HPLC method 总被引:1,自引:0,他引:1
Summary An HPLC method was developed for determination of amoxicillin, penicillin G, penicillin V, ampicillin, oxacillin, cloxacillin,
nafcillin and dicloxacillin in serum from pigs and cattle. Serum was cleaned up by solid-phase extraction (SPE), ultra-filtered
and derivatised. The method was linear in the range tested up to 2000 ng mL−1 of individual penicillins in serum. Limits of detection were 11–14 ng mL−1. Mean recoveries were 90–103% in the range 20–2000 ng mL−1. The relative repeatability, standard deviation was <10% at 20 ng mL−1 level and <6% in the range 100–2000 ng mL−1. 相似文献
17.
A microwave-assisted extraction procedure using water as extractant has been performed for the extraction of acid herbicides
(namely, bentazone, 2,4-D, trichlopyr, 2,4,5-T and 2,4,5-Tp) from different types of soil. Two experimental designs were used
for the optimization of the leaching step. The selection of water as extractant provided a clean approach by avoiding the
use of organic solvents. The use of water also enhanced the extraction efficiency due to the high interaction of the microwave
irradiation with polar solvents. The time required for total removal of the target compounds was 35 min. The recoveries yield
were from 87.64 to 106.14% with a repeatability (expressed as relative standard deviation) ranging between 1.34 and 9.24%.
A within-laboratory reproducibility, also expressed as relative standard deviation, varied from 3.97 to 10.41%. A flow-injection
manifold allowed automation of the whole process by hyphenating the steps subsequent to extraction (namely, filtration, preconcentration,
chromatographic separation and UV detection) for the determination of the analytes. 相似文献
18.
M. Piñeiro-Iglesias M. Miñones-Vázquez E. Vázquez-Blanco S. Muniategui-Lorenzo P. López-Mahía D. Prada-Rodríguez 《Chromatographia》2002,56(7-8):483-488
Summary The aim of this work is to establish the best conditions for concentration and purification steps in the trace analysis of
aliphatic and polycyclic aromatic hydrocarbons (PAH) from atmospheric particulate matter by gas chromatography-flame ionisation
detection (GC-FID) and high performance liquid chromatography with ultraviolet and fluorescence detection (HPLC-UV-FL). The
best results for the more volatile compound were obtained with a combination of rotary evaporation and a stream of nitrogen
(near to 100% for aliphatic hydrocarbons and from 70 to 105% for PAH). Two types of solid phase extraction (SPE)cartridges
(Supelclean
tm
LC-Silica SPE tubes and Sep-Pak? Plus silica cartridges) and glass column were examined for the purification and fractionation step. Blank chromatograms of
both types of cartridges analysed by GC-FID made this study difficult, because a PSS (programmed split-splitless) injector
was employed thereby increasing the sensitivity. This problem was not observed in the HPLC-UV-FL blank chromatograms of these
cartridges. Glass columns filled with silica and alumina were chosen because no interference was found in the GC-FID blank
chromatograms and the best recoveries in the fractionation of both aliphatic hydrocarbons and PAH were achieved. This is especially
important when aliphatic hydrocarbons concentrations are lower than 1 μg mL−1. Finally, the selected conditions were applied to the analysis of hydrocarbons in real atmospheric particulate samples. 相似文献
19.
J. P. Guenier P. Simon J. Delcourt M. F. Didierjean C. Lefevre J. Muller 《Chromatographia》1984,18(3):137-144
Summary After a brief review of several methods described in the literature this paper discusses air-sampling on 2,4-dinitrophenylhydrazine-coated silica gel and identification requirements for aldehydes and ketones most commonly found in industrial pollution.Quantitative analysis of formaldehyde and acetaldehyde either by GC or by HPLC techniques is established using a dynamic system producing test atmospheres and compared with the usual colorimetric determinations. 相似文献
20.
Summary Monomeric and polymeric reversed-phase (C18) column packing materials have been prepared for HPLC. Columns have been tested with aromatic hydrocarbons, acidic and basic
solutes. Good separation of carotenoids can be achieved on well-endcapped phases, but at the separation of some pairs (e.g.
carotenoids with ∈-and β-endgroups) nonendcapped materials give better resolution. The influence of coating structure and
that of endcapping have been discussed.
This paper is dedicated to Professor Csaba Horváth on the occasion of his 60th birthday. 相似文献