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1.
Werner Ahrer Isolde Hagenauer Wolfgang Buchberger 《Monatshefte für Chemie / Chemical Monthly》2000,22(6):155-163
The separation of pyrimidine derivatives by capillary electrochromatography (CEC) using either UV or mass spectrometric detection is described. For UV detection an aqueous phosphate carrier electrolyte containing acetonitrile is employed. The results are compared to the analysis of the same compounds by micellar electrokinetic chromatography in terms of selectivity, migration times, linearity, and detection limits. For the combination of CEC and mass spectrometry (MS) an inexpensive way to couple commercially available instruments is presented; the interface consists of an electrically grounded stainless steel connector (containing a stainless steel frit) serving as the electrode and coupling the CEC capillary with a fused silica transfer capillary to the MS instrument. Alternatively, a PEEK adapter combining the CEC capillary and a grounded stainless steel transfer capillary serving as the electrode is employed. To avoid the formation of hydrogen gas at the coupling piece or the transfer capillary, p-benzoquinone is added to the carrier electrolyte consisting of aqueous ammonium acetate and acetonitrile. 相似文献
2.
Werner Ahrer Isolde Hagenauer Wolfgang Buchberger 《Monatshefte für Chemie / Chemical Monthly》2000,131(2):155-163
Summary. The separation of pyrimidine derivatives by capillary electrochromatography (CEC) using either UV or mass spectrometric detection
is described. For UV detection an aqueous phosphate carrier electrolyte containing acetonitrile is employed. The results are
compared to the analysis of the same compounds by micellar electrokinetic chromatography in terms of selectivity, migration
times, linearity, and detection limits.
For the combination of CEC and mass spectrometry (MS) an inexpensive way to couple commercially available instruments is presented;
the interface consists of an electrically grounded stainless steel connector (containing a stainless steel frit) serving as
the electrode and coupling the CEC capillary with a fused silica transfer capillary to the MS instrument. Alternatively, a
PEEK adapter combining the CEC capillary and a grounded stainless steel transfer capillary serving as the electrode is employed.
To avoid the formation of hydrogen gas at the coupling piece or the transfer capillary, p-benzoquinone is added to the carrier electrolyte consisting of aqueous ammonium acetate and acetonitrile.
Received July 21, 1999. Accepted July 29, 1999 相似文献
3.
The preparation of packed capillaries with stable frits of good quality can be a hurdle to obtain efficient separations in capillary electrochromatography (CEC). Especially with particles smaller than 3 microm, frit preparation is cumbersome. Highly efficient separations using packed capillaries without frits are presented. Under appropriate CEC conditions the particles were retained by electrophoretic attraction towards the anode by a tapered capillary inlet, without the need of a frit at the outlet end. Such fritless capillaries, packed with 1.5 microm nonporous reversed-phase particles, allowed separations with efficiencies of more than 500,000 plates/m. Once the capillaries were conditioned properly, more than 100 separations could be performed with good repeatability. With respect to separation efficiency, fritless capillaries packed with 3 microm particles were comparable with standard CEC capillaries with frits. Examples of separations of steroids, a pesticide and its by-products, and cardiac glycosides under various CEC conditions are shown. 相似文献
4.
Enantiomer separation by electrochromatography (CEC) can be performed in three modes: (i) open-tubular capillary electrochromatography (o-CEC), in which the chiral selector is physically adsorbed coated, and thermally immobilized or covalently attached to the internal capillary wall; (ii) packed capillary electrochromatography (p-CEC), in which the capillary is either filled with chiral modified silica particles or with an achiral packing material, and a chiral selector is added to the mobile phase; and (iii) monolithic (rod)-capillary electrochromatography (rod-CEC) in which the chiral stationary phase (CSP) consists of a single piece of porous solid. We present an overview on methods and new trends in the field of electrochromatographic enantiomer separation such as CEC with either nonaqueous mobile phases or stationary phases with incorporated permanent charges, or with packing beds consisting of nonporous silica particles or particles with very small internal diameters. 相似文献
5.
依据分子印迹技术(MIT)制备的分子印迹聚合物(MIP)颗粒对模板分子及其结构类似物具有特异性识别和选择性吸附作用,同时具有较大的比表面积和快速的传质动力学特性,因而被广泛用作液相色谱固定相和固相萃取材料。将MIP颗粒作为固定相应用于毛细管电色谱(CEC),结合了CEC的快速、高效和MIP的高亲和性、高选择性的特点,成为分析科学领域最具有发展前景的分离技术之一。MIP颗粒在CEC领域有几种不同的应用形式: 作为填充材料填充到毛细管柱中;作为嵌入材料嵌入到毛细管柱内部不同基质的骨架中;作为准固定相添加到CEC运行缓冲溶液中。本文综述了近几年MIP颗粒在CEC领域应用的发展,对该领域今后的发展前景进行了展望。 相似文献
6.
7.
Caliceti Paolo Fassina Giorgio Chaiken Irwin M. 《Applied biochemistry and biotechnology》1987,16(1):119-128
Analytical immuno high performance liquid affinity chromatography (analytical immuno HPLAC) was evaluated as a molecular diagnostic
tool. Antibodies raised in rabbits against bovine neurophysin II were immobilized through Protein A crosslinking onto coated
silica. Interaction of immobilized antibody with mobile antigen was characterized by zonal and frontal elutions of14C-labeled bovine neurophysin II under isocratic, nondenaturing conditions. The Chromatographic behavior shows that analytical
immuno HPLAC with immobilized antibodies can be used to detect the number and functional nature of matrix-interacting antigens
in mixtures, thus providing a quantitative Chromatographic technology for “antigen mapping”. 相似文献
8.
9.
Summary A packing procedure was adopted for capillary electrochromatography (CEC) that produces capillary columns with high separation
efficiencies. The columns were fully packed, 50 cm long, with UV detection being performed through the packed section 30 cm
from the inlet end. The CEC experiments were run at ambient pressure, with no additional pressure applied to the ends of the
column. The stationary phase (octadecyl silica (ODS), 5 μm) promoted a high velocity electroosmotic flow (EOF), enabling rapid
and efficient separation of a hydrocarbon test mixture. Some 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives of mono- and
disaccharides were baseline separated, using a 5 mM NaH2PO4 in 80% acetonitrile and 20% water (v/v) buffer solution. CEC shows promise for future applications in carbohydrate analysis.
Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
10.
In capillary electrochromatography (CEC), magnetic particles (MPs) were packed in a fused silica capillary by using the magnetic field to be retained without frits. For a chiral CEC separation, avidin was immobilized onto the surface of the MPs (AVI-MPs) as a stationary phase by using the physical adsorption technique. The injected AVI-MPs into the capillary were stably captured with the magnet (surface magnetic flux density, 250 mT) under the separation voltage of 10 kV (190 V/cm). By employing the fritless AVI-MPs packed capillary, the chiral separation of ketoprofen was successfully attained with the packing length of only 5 cm. Effects of the modification condition of avidin, pH of background solution, and the packing length on the enantioseparation were also investigated. Under the optimal condition, furthermore, the repeatability for the retention time of ketoprofen was better than 1.5% in the relative standard deviation and the capillary-to-capillary reproducibility was also acceptable in the prepared fritless capillaries. 相似文献
11.
Gucek M Gaspari M Walhagen K Vreeken RJ Verheij ER van der Greef J 《Rapid communications in mass spectrometry : RCM》2000,14(16):1448-1454
The successful coupling of capillary electrochromatography (CEC) to an ion trap mass spectrometer via a nanoelectrospray interface (nESI) is described. Using a conductively coated tip butted to the end of a CEC column, it was possible to obtain a stable spray without any sheath liquid being employed. Selected small peptides were separated with CEC columns (100 microm i.d./25 cm long) packed with 3 microm Hypersil C8 or C18 bonded silica particles with an eluent composed of ammonium acetate/acetonitrile. Peptide mixtures of desmopressin, peptide A, oxytocin, carbetocin and [Met(5)]-enkephalin were detected in the mid-attomole range, which is the lowest amount analyzed using CEC combined with MS detection. It was also observed that sensitivity can be compromised at higher separation voltages. We demonstrate that CEC/nESI-MS, at the current stage of development, represents one of the most sensitive systems for peptide analysis. 相似文献
12.
This paper describes the preparation and optimization of packed capillary columns for reversed‐phase separation of steroids with CEC. The fabrication of on‐column frits is considered to be the most important step for obtaining a reproducible packed column for CEC separation. Porous silicate frits were generated in a fused‐silica capillary by heating the silica gel/sodium hydroxide solutions electrically. The optimized conditions involve silica gel (10.8%), sodium hydroxide (5.8%), and heating time (5 sec) with heating voltage (5V) for obtaining a 100‐μ end‐frit that can withstand pressure over 6000 psi. A HPLC pump was utilized to pack the 5‐μm ODS particle slurry into the capillary column. The ODS packed capillaries were then utilized for the separation of four anabolic cholesterols with a capillary electrophoresis system without pressurization of the column. The reproducibility of the packed columns was evaluated by measuring the relative standard deviations of four steroids. The relative standard deviations of migration time for column‐to‐column, day‐to‐day, and run‐to‐run are less than 7%, 2%, and 1% for four steroids, respectively. 相似文献
13.
Pavla Sedláková Adam Eckhardt Kateřina Lacinová Statis Pataridis Ivan Mikšík Vladimír Král Václav Kašička 《Journal of separation science》2009,32(22):3930-3935
Open‐tubular CEC (OT‐CEC) with a new stationary phase, salophene–lanthanide–Zn2+ complex, has been applied to the separation of tryptic peptides of native BSA and BSA glycated by glucose and ribose. Glycation of proteins (non‐enzymatic modification by sugars) significantly affects their properties and it is of great importance from a physiological point of view. Separation of tryptic peptides of glycated BSA by CZE was poor because of their strong adsorption to the bare fused silica capillary. An improved separation of tryptic peptides of both native and glycated BSA was achieved by OT‐CEC in the fused silica capillary non‐covalently coated with salophene–lanthanide–Zn2+ complex, which suppressed the adsorption of peptides to the capillary and via specific interactions with some (glyco)peptides enhanced selectivity of the separation. Significant differences have been found in OT‐CEC analyses of tryptic hydrolysates of native and glycated BSA. In OT‐CEC‐UV profile of tryptic peptides of native BSA, 44 peaks could be resolved, whereas a reduced number of 38 peaks were observed in the profile of tryptic peptides of glucose‐glycated BSA and only 30 peaks were found in the case of ribose‐glycated BSA. The developed OT‐CEC can be potentially used for monitoring of protein glycation. 相似文献
14.
Pressure-supported electrochromatography using capillaries packed with permethyl-cyclodextrin covalently linked via an octamethylene spacer to dimethylpolysiloxane and immobilized on silica (Chirasil-Dex silica) has been employed as an efficient and rapid method for the enantiomer separation of various racemic compounds. By comparing this method with micropacked liquid chromatography (LC), employing the same column in a unified instrumental setup, micropacked capillary electrochromatography (CEC) shows higher column efficiencies and hence better resolution factors. The influence of type and concentration of buffer, amount and nature of organic modifier, and pressure support is investigated. 相似文献
15.
Summary To characterize the retention and selectivity of separations of 23 flavonoids (aglycones and glycosides) relationships betweenR
F and modifier concentration were determined for silica and diol adsorbents (with mixtures of ethyl acetate and methanol as
mobile phases), for cyanopropyl silica (with mixtures of ethyl acetate and dichloromethane as mobile phases), for aminopropyl
silica (with mixtures of ethyl acetate, methanol and water as mobile phases) and for octadecyl silica (with mixtures of methanol
and water as mobile phases). Owing to large polarity differences between aglycones and glycosides, these groups of compounds
cannot be separated other than by use of reversed-phase systems, for which the selectivity is lower. It follows from correlation
plots ofR
F1 againstR
F2 that for some pairs of adsorbents (e. g. silica and diol) selectivity differences are small; for others the points in the
plot are widely dispersed, indicating selectivity differences. The chemometric database obtained can be used to choose optimum
chromatographic systems for the separation of given sets of flavonoids and for planning gradient elution programs for separation
of flavonoid aglycones and glycosides in a single TLC experiment. 相似文献
16.
Capillary electrochromatography (CEC) is an emerging technique that combines features of both micro-capillary high-performance liquid chromatography (microHPLC) and capillary electrophoresis (CE). This separation technique possesses high speed and the efficiency of an electro-driven system, while the selectivity and sample loadability compare to those of a packed capillary LC column. Since the separation mechanism is based on that of HPLC, the concept of isoeluotropic strength and selectivity of solvents as well as the on-column focusing techniques for sample introduction used in LC can be applied in CEC. This article examines some of these features of CEC in the context of our own experiences with the technique. More specifically, emphasis is placed on applications of CEC to the analysis of DNA adducts of polyaromatic hydrocarbons by coupling CEC to mass spectrometry. It is shown that, with proper selection of mixed organic modifiers in the mobile phase, i.e. ternary and quaternary mobile phases, complex DNA adduct mixtures derived from in vitro reactions can be separated isocratically with improved selectivity and much greater speed than by HPLC. Additionally, the speed of the analysis is further enhanced by employing a step gradient. Furthermore, CEC may be easily coupled to mass spectrometry such that the characterization of each isolated component from the mixtures is performed on-line with the separation. By using on-column focusing, the sample loadability onto a CEC column is improved. 相似文献
17.
Macroporous, monolithic capillary electrochromatography (CEC) columns, featuring a hydrophobic stationary phase, have been applied to the separations of steroids with good column efficiency. Using isocratic and gradient elution runs, mixtures of neutral or conjugated steroids could be resolved. While dansylated ketosteroids were detectable through laser-induced fluorescence at attomole levels, the CEC columns coupled to electrospray-ion-trap mass spectrometry featured femtomole detection limits. 相似文献
18.
In this report, microcolumn separation schemes involving monolithic capillary columns with immobilized lectins, and relevant to nanoglycomics/nanoproteomics were introduced. Positive and neutral monoliths based on poly(glycidyl methacrylate-co-ethylene dimethacrylate) were designed for achieving lectin affinity chromatography (LAC) by nano-LC and CEC. The positive monoliths (i.e., monoliths with cationic sites) afforded relatively high permeability in nano-LC but lack predictable EOF magnitude and direction, while neutral monoliths provided a good compromise between reasonable permeability in nano-LC and predictable EOF in CEC. Lectin affinity nano-LC permitted the enrichment of classes of different glycoproteins having similar N-glycans recognized by the immobilized lectin, whereas lectin affinity CEC provided the simultaneous capturing and separation of different glycoproteins due to differences in charge-to-mass ratio. Also, this investigation demonstrated for the first time the coupling of lectin capillary columns in series (i.e., tandem columns) for enhanced separation of glycoproteins by LAC using the CEC modality. Furthermore, in the coupled columns format, glycoforms of a given glycoprotein were readily separated. 相似文献
19.
Mixtures of nitroaromatic and nitramine explosive compounds and their degradation products were analyzed using electrokinetically driven separations with both indirect laser-induced fluorescence (IDLIF) and UV absorption detection. Complete separations of the 14-component mixture (EPA 8330) were achieved using both capillary electrochromatography (CEC) and micellar electrokinetic chromatography (MEKC). IDLIF detection was performed using an epifluorescence system with excitation provided by a 635 nm diode laser and micromolar concentrations of the dye Cy-5 as the visualizing agent. While the sensitivity of the two detection methods was similar for the nitroaromatic compounds, the nitramines could only be detected using UV absorption due to their low fluorescence quenching efficiency of Cy-5. The detection sensitivity using IDLIF was limited by low frequency oscillations in the fluorescence background. The oscillations increased with higher electric field strength and were attributed to thermal fluctuations caused by Joule heating. Due to the more conductive running buffer and higher separation currents used in MEKC, sensitive IDLIF detection could only be achieved using low (approximately 100 V/cm) field strengths, resulting in long analysis times. CEC separations, which are typically run with low conductivity mobile phases to avoid bubble formation, are less sensitive to this effect. In CEC separations with IDLIF detection a stable fluorescence background using Cy-5 could be established using only a nonporous stationary phase. In capillaries packed with porous silica particles, anomalous migration behavior was observed with charged dye molecules and a stable fluorescence background could not be established under electrokinetic flow. This is the first demonstration of IDLIF in packed channel CEC. 相似文献
20.
The separation of the major flavanone-7-O-glycoside constituents of Citrus was carried out by isocratic reversed phase capillary electrochromatography using a 75 microm i.d. silica fused column packed with 5 microm ODS silica gel. In comparison to HPLC mode, capillary electrochromatography resolution of flavanone glycosides was obtained with a high selectivity factor. Optimum separation conditions were found using a mixture of ammonium formate (pH 2.5)--acetonitrile (8:2, v/v) as the mobile phase by the short-end injection mode. Under these conditions all the investigated flavanones were baseline-resolved within short analysis time (i.e. between 5 and 10 min). A study, evaluating the intra- and inter-day repeatability as well as limit of detection and method linearity, was developed in accordance with the analytical procedures for method validation. The developed method was applied for the quantitative analysis of flavanone glycosides in commercial fruit juices (sweet orange, lemon and grapefruit). 相似文献