Combination Of Capillary Zone Electrophoresis Research Articles

Analysis of flavonoids in propolis by capillary electrophoresis

Flavonoid contents of nine raw and nine commercial propolis samples were analyzed by capillary electrophoresis. At first, 15 commercially available flavonoid standards including apigenin, chrysin, luteolin, galangin, kaempferol, morin, myricetin, quercetin, quercitrin, rutin, hesperetin, naringin, naringenin, daidzein and genistein were used to develop the electrophoretic conditions. At a running temperature of 25°C and detection wavelength at 214 nm, the separation of these standards was most satisfactorily achieved by a combination of capillary zone electrophoresis (CZE), utilizing 0.1 M borate buffer (pH 9.5) containing 5% methanol under a voltage of 18 kV, and micellar electrokinetic capillary electrophoresis (MECC), utilizing 0.03 M sodium borate (pH 8.5) containing 0.05 M SDS under a voltage of -15 kV. We found 12 out of the 15 flavonoids were identified in raw propolis, but only 11 were detected in commercial propolis products. The total contents of the identified flavonoids in raw and commercial propolis were 254 to 19147 ppm and 1228 to 7985 ppm, respectively, suggesting that both the origin and processing are important factors affecting the flavonoid content in propolis.

Parallel analysis and orthogonal identification of N-glycans with different capillary electrophoresis mechanisms

The deep involvement of glycans or carbohydrate moieties in biological processes makes glycan patterns an important direction for the clinical and medicine researches. A multiplexing CE mapping method for glycan analysis was developed in this study. By applying different CE separation mechanisms, the potential of combined parallel applications of capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC) and capillary gel electrophoresis (CGE) for rapid and accurate identification of glycan was investigated. The combination of CZE and MEKC demonstrated enhancing chromatography separation capacity without the compromises of sample pre-treatment and glycan concentration. The separation mechanisms for multiplexing platform were selected based on the orthogonalities of the separation of glycan standards. MEKC method exhibited promising ability for the analysis of small GU value glycans and thus complementing the unavailability of CZE. The method established required only small amount of samples, simple instrument and single fluorescent labelling for sensitive detection. This integrated method can be used to search important glycan patterns appearing in biopharmaceutical products and other glycoproteins with clinical importance.

Analysis of lysozyme in cheese samples by on-line combination of capillary zone electrophoresis and mass spectrometry

Some methodological aspects of an on-line combination of capillary zone electrophoresis with mass spectrometric detection (CZE–QqQ–MS) were studied in this work as well as the possibilities of using this combination for analysis of the high-molecular mass compounds present in multi-component matrices. All experiments using an on-line combination of capillary electrophoresis with mass spectrometric detection were carried out in cationic mode in covalently-coated capillary. The optimised electrolyte system consisted of 100mmol/L formic acid. Prior to the CZE–QqQ–MS analysis, an extraction of lysozyme from cheese samples using 1mol/L of acetic acid was performed. The LOD was 3.6mg lysozyme per kg and the LOQ was 10.9mg lysozyme per kg. The concentration range of the lysozyme determined in four cheese samples analysed in this work was from 0.5 to 3.3g of lysozyme per kg. The values of the relative standard deviations thus obtained were from 4.6% to 9.3% depending on the cheese sample.

Analysis of buserelin in urine by online combination of capillary zone electrophoresis with electrospray mass spectrometry

A fast and precise analysis of the synthetic peptide buserelin in urine using CZE-ESI-MS method has been demonstrated. Formic acid at 50 mmol/L concentration served as background electrolyte in CZE stage and it is compatible with MS detection in positive ionization mode. Two injection modes were tested, i.e. pressure (50 mbar for 5 s) and electrokinetic injection (5 kV for 5 s), of which electrokinetic injection provided better calibration parameters. Buserelin LODs were 0.47 microg/mL in water and 0.63 microg/mL in ten times diluted urine samples using pressure injection, while they were 0.32 microg/mL in water and 0.34 microg/mL in ten times diluted urine samples using electrokinetic injection. Repeatability of buserelin migration times was below 6% (pressure injection mode) and 1% (electrokinetic injection mode). Repeatability of buserelin peak area in SIM mode (m/z=620.5+/-0.5) was less than 12% (pressure injection mode) and 5.8% (electrokinetic injection mode). In this work, no interferences were observed during the analyses of spiked urine samples.

Assay of phenolic compounds in red wine by on-line combination of capillary isotachophoresis with capillary zone electrophoresis

The on-line combination of capillary zone electrophoresis (CZE) with capillary isotachophoresis (ITP) increases significantly the separation capability and sensitivity of capillary electrophoresis. This technique was used for separation and quantification of fourteen selected natural constituents in red wine belonging to flavonoids and phenolic acids. The leading electrolyte (LE) in the ITP pre-separation step was 10 mM HCl of pH * 7.2 with Tris as counterion, the terminating electrolyte (TE) was 50 mM boric acid of pH * 8.2 (adjusted with barium hydroxide). The background electrolyte in the electrophoretic step contained 25 mM β-hydroxy-4-morpholinopropanesulfonic acid (MOPSO), 50 mM Tris, 15 mM boric acid and 5 mM β-cyclodextrin of pH * 8.5. The content of methanol in all electrolytes was 20% (v/v). For exact timing of the transfer of isotachophoretically stacked analyte zones into the CZE column and for the control of the residual amount of leading and terminating ITP electrolytes picric acid was used as coloured marker. The R.S.D. values ( n=6) ranged between ∼0.1% (for 0.25 μg ml −1 rutin) and ∼11% (for 0.25 μg ml −1 of quercitrin). Detection limits were 30 ng ml −1 for phenolic acids, quercitrin and rutin, 100 ng ml −1 for quercetin, kaempferol and epicatechin and 250 ng ml −1 for catechin. A single analysis took 45 min.

Combination of microporous membrane liquid–liquid extraction and capillary electrophoresis for the analysis of aromatic amines in water samples

A method has been established for the simultaneous analysis of eight aromatic amines in water samples by the combination of capillary zone electrophoresis and microporous membrane liquid–liquid extraction (MMLLE). Eight aromatic amines including N, N-dimethylaniline, m-methylaniline, 3,4-dimethylaniline, 2-naphthylamine, 1-naphthylamine, 4-aminobiphenyl, 2-chloroaniline and 2,4-chloroaniline were well separated under optimal separation conditions. The influence factors relevant to the MMLLE process were investigated and the final optimized parameters were used for analysis. The correlation coefficients were excellent with R 2 values larger than 0.99 and the detection limits (S/N=3) were in the range of 0.16–7.5 ng ml −1. The precision and recoveries were within the ranges of 1.7–13.5 and 78.8–112.6%, respectively.

Trace ion analysis of sea water by capillary electrophoresis: determination of strontium and lithium pre-concentrated by transient isotachophoresis.

The applicability of capillary zone electrophoresis (CZE) to ions having relatively low natural occurrences in sea water is limited by method's relatively poor concentration detection sensitivity. A combination of CZE with indirect UV detection and transient isotachophoresis (tITP) pre-concentration was developed to evolve the CZE practical utility towards the quantitative determination of the minor sea water cationic components, strontium and lithium. The ITP stacking criterion at the initial stage of a CZE separation was met by taking a highly mobile sodium, the principle matrix cation, to perform the role of a leading ion, whereas the moderately mobile sample macrocomponents, Ca2+ and Mg2+, acted as the terminating ion. The carrier electrolyte, consisting of 10 mM 4-methylbenzylamine and 1.5 mM citric acid at pH 4.8, was found to be optimal to accommodate both analyte cations in the ITP range and then separate them in the CZE mode, with relative standard deviations for migration times from 0.06-0.15% and for peak areas from 4-8%. The limits of detection were 1.3 mg l(-1) Sr2+ and 0.12 mg l(-1) Li+. The developed method was applied to the analysis of a surface sea water sample and a sea water reference material. The results were in good agreement with those obtained by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and electrothermal atomic absorption spectrometry (ET-AAS).

Extracellular glutamate, aspartate and arginine increase in the ventral posterolateral thalamic nucleus during nociceptive stimulation

Although there is evidence that the thalamus plays a remarkable role in pain processing few in vivo studies on the thalamic neurochemical correlates of pain have been done. In the present experiments a combination of capillary zone electrophoresis with laser-induced fluorescence detection (CZE–LIF) and microdialysis in freely moving rats was used to measure extracellular arginine, glutamate and aspartate in the thalamus during the formalin test. Microdialysis probes were implanted in the left ventral posterolateral (VPL) nucleus of the thalamus in rats. Samples were collected every 30 s, derivatized with fluorescein isothyocyanate and injected into a CZE–LIF instrument. After nine baseline samples, a subcutaneous formalin (5%, 50 μl) injection in the right hind paw caused an increase of arginine, glutamate and aspartate that lasted for about 3 min. These increases were calcium and nerve impulse dependent. These results indicate that the release of arginine, glutamate and aspartate may mediate rapid pain neural transmission in the VPL nucleus of the thalamus.

A Potentiometric Detection Technique for Chelating Agents after Separation by Capillary Zone Electrophoresis

The combination of capillary zone electrophoresis with potentiometric detection has been investigated for the determination of chelating agents such as diethylenetriaminepentaacetic acid. The detector consists of a metallic copper electrode with a diameter of 100 μm arranged in an end-capillary configuration. The electrode potential depends on the concentration of copper ions at the electrode surface and therefore decreases when chelating agents pass the electrode. In combination with UV detection, both free ligands and metal complexes could be detected.

Capillary zone electrophoresis of proteins.

This review article with 237 references is focused on capillary zone electrophoresis (CZE) of proteins. It includes discussion of modeling electrophoretic migration of proteins, sample pretreatment before the analysis, methods reducing the sorptions of proteins on the capillary wall, and techniques for increasing selectivity by using electrolyte additives including the sieving matrices. Significant progress in detection techniques, namely in laser-induced fluorescence and mass spectrometry, is emphasized. Modifications of CZE using specific interactions, such as affinity capillary electrophoresis or capillary immunoelectrophoresis, are debated as well as combination of CZE with other separation methods such as high performance liquid chromatography (HPLC). A number of practical applications of CZE of proteins are described.

4] Structural characterization of hemoglobin variants using capillary electrophoresis and fast atom bombardment mass spectrometry

Publisher Summary The combination of capillary zone electrophoresis (CZE) with fast atom bombardment mass spectrometry (FAB/MS) analysis according to the FAB mapping procedure couples a potentially fast high-resolution separation method with one of the most powerful techniques for structural characterization. Capillary electrophoresis has the ability to handle very small volume samples (picoliter range) and attomole (10 -18 mol)-level detection limits reaching separation efficiencies of the order of 10 6 theoretical plates. The CZE of proteins with UV detection have often resulted in broad, tailing peaks because of the absorption of proteins on active sites of the negatively charged capillary wall. However, the introduction of coated capillaries made CZE a fast and sensitive method for the detection of even similarly charged variants; the resolution obtained using this technique is comparable to the well-established electrophoretic and chromatographic procedures and requires smaller samples. Its speed and simplicity with respect to the given techniques and the possibility of automation and of development on a micropreparative scale mean the whole procedure is a significant alternative to conventional systems.

Capillary zone electrophoresis and packed capillary column liquid chromatographic analysis of recombinant human interleukin-4

Capillary zone electrophoresis (CZE) and packed capillary column liquid chromatography (micro-LC) have been applied to the analysis of the recombinant human protein interleukin-4 (rhIL-4). Separations for both the parent protein and its enzymatic digest were developed for the purpose of characterizing protein purity and identity. CZE separations of the intact protein were investigated over the pH range of 4.5 to 8.0 using uncoated fused silica capillaries. Gradient reversed-phase micro-LC was performed using 0.32 mm packed capillary columns at flow-rates of 5–6 μl/min. Emphasis was placed on the ability of these methods to separate close structural variants and degradation products of the protein. Peptide mapping of the tryptic digest of rhIL-4 using a combination of CZE and micro-LC provided complimentary high resolution methods for establishing protein identity. Reproducible separations were achieved using sub-picomol amounts of sample. The advantages and problems encountered with these two techniques for characterizing rhIL-4 were assessed.

Studies in capillary zone electrophoresis with a post-column multiple capillary device for fraction collection and stepwise increase in electroosmotic flow during analysis.

A new approach involving the stepwise increase in electroosmotic flow during analysis in capillary zone electrophoresis is introduced and evaluated in the rapid separations of proteins and peptides. The stepwise increase in electroosmotic flow is based on the principle of coupled capillaries in series having different flow characteristics, a concept that was introduced recently by our laboratory. To produce stepwise changes in electroosmotic flow during analysis, a post-column multiple capillary device, which allowed the switching between several coupled capillary systems, was designed and constructed in-house. The utility of the multiple capillary device was also demonstrated and extended to fraction collection of separated analytes in short capillary segments. The fraction collection in capillaries facilitated the quantitative transfer of the collected fractions to high performance liquid chromatography (HPLC) for further analysis or to mass spectrometry (MS) for structural determination. The off-line combination of capillary zone electrophoresis with HPLC or MS utilized commercial instruments without the need of expensive interfacing designs.

Conversion of capillary zone electrophoresis to free-flow zone electrophoresis using a simple model of their correlation: Application to synthetic enkephalin-type peptide analysis and preparation

A simple mathematical model of the correlation between capillary zone electrophoresis (CZE) and continuous free-flow zone electrophoresis (FFZE) was developed. The model results from the fact that both methods are based on the same separation principle (zone electrophoresis) and both are performed in a free solution of the same composition. Based on this model, a procedure for the conversion of an analytical microscale CZE separation into a preparative FFZE separation was developed. The applicability of this procedure is demonstrated by CZE analysis at the picomole level and FFZE preparative fractionation (60 mg/h throughput) of crude synthetic biologically active peptide [ d-Tle 2,5]-dalargin. The combination of CZE and FFZE provides an efficient and economical tool for synthetic peptide analysis and preparation.