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PubMed2002

Modification of capillary electrophoresis capillaries by poly(hydroxyethyl methacrylate), poly(diethylene glycol monomethacrylate) and poly(triethylene glycol monomethacrylate).

Modification of capillary electrophoresis (CE) capillaries by poly(hydroxyethyl methacrylate) (poly(HEMA), poly(diethylene glycol monomethacrylate) (poly(DEGMA) and poly(triethylene glycol monomethacrylate) (poly(TEGMA), was studied. Methods based on physical adsorption of the modifier and on its chemical binding were compared on the basis of the electroosmotic flow (EOF) reproducibility, the EOF dependence on the pH, the symmetry of the peak of positively charged tyramine, the stability of the coating and the separation of standard and milk proteins in the modified capillaries. Reproducible coatings were obtained by chemical binding of the polymers to the capillary walls and by coating with a solution of a polymer, as also demonstrated by the atomic force microscopy.

Adsorption↗
PubMed1998

Simultaneous chiral separation of 3,4-methylenedioxymethamphet- amine, 3-4-methylenedioxyamphetamine, 3,4-methylenedioxyethylam- phetamine, ephedrine, amphetamine and methamphetamine by capillary electrophoresis in uncoated and coated capillaries with native beta-cyclodextrin as the chiral selector: preliminary application to the analysis of urine and hair.

The importance of the chiral analysis of amphetamine-related substances in both clandestine preparations and biological samples is widely recognized. For this purpose, capillary electrophoresis was successfully applied by several authors, but only few reports concerned ring-substituted amphetamines, which represent the main components of "ecstasy", a widely abused "recreational" substance. In the present work, the simultaneous chiral analysis of ephedrine, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3-4-methylenedioxyamphetamine (MDA) and 3,4-methalenedioxyethylamphetamine (MDE) is reported, by using capillary electrophoresis with native beta-cyclodextrin (15 mM) as the chiral selector. After preliminary tests at different pH values (phosphate buffer 100 mM, pH 2.5-9.0) and with bare or coated fused-silica capillaries, the optimized conditions were: pH 2.5 phosphate, uncoated capillary (45 cm x 50 microm inner diameter), potential 10 kV. Detection was either by fixed wavelength (200 nm) or multiwavelength (190-400 nm) UV absorbance. Under these conditions, good resolution was obtained for all the analytes, with excellent chiral selectivity and efficiency. The sensitivity for the individual enantiomers was better than 0.2 microg/mL, analytical precision was characterized by relative standard deviation values < 0.8% (< or = 0.15% with internal standardization) for migration times intra-day and < 2.0% (< or = 0.54% with internal standardization) day-to-day; linearity, in the range 0.156-40 microg/mL, and accuracy were also satisfactory. After a simple liquid-liquid extraction, urine samples could be analyzed with a sensitivity well below the recommended NIDA cut-off of 500 ng/mL. For hair samples, it was necessary to increase the sensitivity by applying a field-amplified sample stacking procedure, which allowed the chiral determination of MDA, MDMA and MDE at concentrations occurring in real samples from ecstasy users, with the possibility of recording UV spectra of the peaks.

Amphetamines↗
PubMed1998

Detectability improvements in capillary zone electrophoresis by combining single capillary isotachophoretic preconcentration and frequency doubled argon ion laser-induced fluorescence detection.

Due to the small path length and low injection volume the concentration limit of detection is comparatively poor in capillary electrophoresis (CZE) with UV detection. This limitation can be overcome by means of preconcentration methods and/or improved detection techniques. This paper describes a strategy where isotachophoresis (ITP) is used to preconcentrate a new cholinesterase inhibitor (NXX-066) prior to a capillary zone electrophoresis analysis in the same single capillary. A hydrodynamic backpressure is used to prevent the analyte from migrating out of the capillary. Laser-induced fluorescence (LIF) is used to further increase the detectability. The total gain in detectability with ITP-CZE-LIF compared to CZE-UV was at least 5500-fold, and it is possible to determine NXX-066 at the 1 nM level. The ITP-CZE method was further evaluated for two beta-blockers; the mean coefficient of variation of the peak areas was 3.4% and the linearity of the calibration plots was satisfying.

Argon↗
PubMed1998

Preconcentration and separation of antisense oligonucleotides by on-column isotachophoresis and capillary electrophoresis in polymer-filled capillaries.

Small, single-stranded, chemically modified oligonucleotides, complementary to a specific gene section, commonly referred to as antisense compounds, are being investigated as potential therapeutic drugs. A number of modified oligonucleotides, in particular phosphorothioates, are in clinical development. Shorter fragments are found as metabolic products. Isotachophoresis (ITP) allows the introduction of large, diluted sample plugs into the separation capillary. In this work, ITP and capillary electrophoresis (CE) in polymer solutions were successfully coupled in a single capillary in a commercial instrument to increase sensitivity with UV detection and to shorten the time for sample pretreatment. It was shown that ITP-CE can be used as a preconcentration and clean-up method for phosphodiester- and phosphorothioate-containing samples. Up to 3 microL sample could be injected into the capillary without significantly disturbing the separation performance. ITP-CE of phosphodiesters directly out of salt- and protein-containing samples could be demonstrated. For phosphorothioates in serum samples an additional sample clean-up was necessary, due to oligonucleotide-protein binding. An optimized replaceable polymer solution was developed to increase the separation performance for heterogeneous phosphorothioates. A dextran-based sieving medium showed a good separation performance in ITP-CE of phosphorothioates. A concentration detection limit of 8.10(-9) mol/L for the 20-mer phosphorothioate ISIS5132, isolated from rat serum, was found.

Animals↗
PubMed1998

Analysis of antisense oligonucleotides by on-capillary isotachophoresis and capillary polymer sieving electrophoresis.

An attempt was made to evaluate the stability of an antisense oligonucleotide against nucleases present in HBL 100ras cells. To detect nanomolar concentrations of the oligonucleotide, a sensitive detection system was required. A combination of capillary electrophoresis/laser-induced fluorescence (CE-LIF) with fluorescence derivatization did not improve the sensitivity significantly and also resulted in loss of separation of the derivatized sample. On-column isotachophoresis for the preconcentration of oligonucleotide samples in DB-17 coated capillaries filled with hydroxyethyl cellulose solution could be an alternative. The isotachophoresis (ITP) step allows injection of up to 40% of the capillary volume without loss in peak resolution and peak efficiency. Using ITP-capillary polymer sieving electrophoresis (CPSE), the limit of quantitation at a signal-to-noise ratio of 10 was 73 ng/mL for a 12-mer oligonucleotide. Using these conditions, the gain in sensitivity was 125.

Breast↗
PubMed1998

Simultaneous measurement of alpha-amylase and glucoamylase activities in sake rice koji by capillary electrophoresis of sodium dodecyl sulfate-protein complexes and activity measurement of glucoamylase by in-capillary enzyme reaction method.

Capillary electrophoresis (CE) of sodium dodecyl sulfate (SDS)-protein complexes using a nongel sieving matrix (CE-SDS) has been applied to the simultaneous analysis of alpha-amylase and glucoamylase activity in sake rice koji which is employed for the brewing of sake. Alpha-amylase and glucoamylase in sake rice koji extracts were successfully analyzed by CE-SDS. Alpha-amylase and glucoamylase were found to have molecular masses of 53000 and 63000 Da, respectively, as determined by the migration times of eight standard proteins. These values agree with those determined by SDS-polyacrylamide gel electrophoresis (PAGE). The results of CE-SDS method were compared with those achieved by the official method. The relative standard deviations (RSD) of the alpha-amylase and glucoamylase activities by CE-SDS were less than 5.0% in both intra-day and inter-day experiments. An electrophoretic analysis of products of an enzyme reaction of a substrate by in-capillary reaction was also useful for the activity measurement of glucoamylase in sake rice koji. p-Nitrophenyl-beta-D-maltoside (PNP-Mal) was employed as a substrate and p-nitrophenyl-beta-D-glucopyranoside (PNP-Glu) was the product of the enzyme reaction. The glucoamylase activity of sake rice koji samples gave the good linear relationship with the peak area observed in the in-capillary enzyme reaction method. The glucoamylase activity in sake rice koji was measured by either CE-SDS or the in-capillary enzyme reaction more easily than by the official method. Both methods can be applied to the routine quality control of alpha-amylase and glucoamylase activities in sake rice koji.

Alcoholic Beverages↗
PubMed1998

Capillary affinity chromatography and affinity capillary electrophoresis of heparin binding proteins.

A new approach for separation, capillary affinity chromatography, is introduced for studying the interaction of heparin with antithrombin III and secretory leukocyte proteinase inhibitor. Heparin is covalently immobilized on the surface of an etched capillary through a silane spacer. The proteins are injected into the heparinized capillary, bound to the heparin, washed with buffer, eluted with sodium chloride in the same buffer using a pressure injection mode and eluting protein detected by absorbance. The resulting affinity separation is similar to that obtained from traditional affinity chromatography. The quantity of loaded protein in capillary affinity chromatography is at the nanogram level, offering an improvement over the milligram levels required for standard affinity chromatographic methods.

Antithrombin III↗
PubMed1998

Screening for urinary amphetamine and analogs by capillary electrophoretic immunoassays and confirmation by capillary electrophoresis with on-column multiwavelength absorbance detection.

This paper characterizes competitive binding, electrokinetic capillary-based immunoassays for screening of urinary amphetamine (A) and analogs using reagents which were commercialized for a fluorescence polarization immunoassay (FPIA). After incubation of 25 microL urine with the reactants, a small aliquot of the mixture is applied onto a fused-silica capillary and unbound fluorescein-labeled tracer compounds are monitored by capillary electrophoresis with on-column laser-induced fluorescence detection. Configurations in presence and absence of micelles were investigated and found to be capable of recognizing urinary D-(+)-amphetamine at concentrations > about 80 ng/mL. Similar responses were obtained for racemic methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA). The electrokinetic immunoassay data suggest that the FPIA reagent kit includes two immunoassay systems (two antibodies and two tracer molecules), one that recognizes MA and MDMA, and one that is geared towards monitoring of A. For confirmation analysis of urinary amphetamines and ephedrines, capillary electrophoresis in a pH 9.2 buffer and multiwavelength UV detection was employed. The suitability of the electrokinetic methods for screening and confirmation is demonstrated via analysis of patient and external quality control urines.

Amphetamines↗
PubMed2003

A new and selective capillary column coated with cationic diazacrown ether for separation of organic and inorganic anions by capillary electrophoresis.

A new coated capillary has been introduced for capillary electrophoretic separation of anions by using a positively charged diazacrown ether with a 12-membered ring. A positive charge spread over the inner capillary surface led to a substantial anodic electroosmotic flow (EOF) over the range of migrating buffer of pH 2-11. Under the optimum conditions of 25 mM phosphate buffer at pH 7, the diazacrown-coated capillary showed a successful simultaneous separation of 7 inorganic anions and 13 aromatic anions (including positional isomers) in less than 15 min. The migration times of the sample anions and EOF marker for consecutive runs on a single column were highly reproducible, giving a relative standard deviation of 1%. Theoretical treatment of the migration behavior clearly demonstrated that ion association between the diazacrown and analyte anions is strongly dependent on the nature of the functional groups of anions (e.g., sulfonate groups > carboxyl groups) and the number of negative charges (e.g., trivalent anions > divalent anions > monovalent anions) on the analyte.

Anions↗
PubMed2003

Recent advances in capillary electrophoresis and capillary electrochromatography of peptides.

An overview of the recent developments in the applications of high-performance capillary electromigration methods, namely zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography, to analysis, preparation, and physicochemical characterization of peptides is presented. New approaches to the theoretical description and experimental verification of the electromigration behavior of peptides and the methodological aspects of capillary electroseparations of peptides, such as rational selection of separation conditions, sample treatment, and suppression of adsorption, are discussed, and new developments in individual separation modes and new designs of detection systems applied to peptide separations are shown. Several types of applications of capillary electromigration methods to peptide analysis are presented: quality control and purity tests, determination in biomatrices, monitoring of physical and chemical changes and enzymatic conversions, amino acid and sequence analysis, and peptide mapping. The examples of micropreparative peptide separations are given and capabilities of capillary electromigration techniques to provide important physicochemical characteristics of peptides are demonstrated.

Animals↗
PubMed2004

Monomer surface modifications for rapid peptide analysis by capillary electrophoresis and capillary electrochromatography coupled to electrospray ionization-mass spectrometry.

In this study, positively charged alkylaminosilyl monomers were used to modify the inner surface of fused silica capillaries, which subsequently were employed in capillary electrophoresis (CE) and capillary electrochromatography (CEC). The obtained surfaces yield a reversed electroosmotic flow (EOF) and have varying carbon chain lengths, that interact with the analytes and give chromatographic retention. The coating procedure is very simple and fast. The performance of the modified capillaries was evaluated regarding pH influence on EOF and chromatographic interactions. The experiments were conducted with UV and mass spectrometry (MS) and applied to the separation of various neuropeptides. The derivatized surfaces showed a linear (R(2) approximately 0.99) pH dependence with isoelectric points (pI) at 8.6-8.8. Rapid separations of peptide standards and a protein digest with efficiencies as high as 5 x 10(5) plates/m were performed.

Chromatography↗
PubMed2004

Capillary sieving electrophoresis-micellar electrokinetic chromatography fully automated two-dimensional capillary electrophoresis analysis of Deinococcus radiodurans protein homogenate.

We report the one- and two-dimensional (1-D and 2-D) capillary electrophoresis separation of Deinococcus radiodurans protein homogenate. Proteins are labeled with the fluorogenic reagent 3-(2-furoyl)quinoline-2-carboxaldehyde (FQ), which reacts with lysine residues and creates a highly fluorescent product. Detection is by laser-induced fluorescence. 1-D capillary sieving electrophoresis (CSE) produces over 150,000 plates and micellar electrokinetic capillary chromatography (MEKC) produces over 900,000 plates for components in a D. radiodurans protein homogenate. In a 2-D separation, proteins are first separated by CSE. Fractions are repetitively transferred to a second capillary for further separation based on MEKC. The 2-D separation has a approximately 550 spot capacity. Over 150 components are partially resolved from the homogenate. Resolution is limited in the first dimension by diffusion of proteins during the long separation period and in the second dimension by the combination of a long fraction-transfer time and short separation period.

Automation↗
PubMed2005

Large-volume stacking in capillary electrophoresis using pH hysteresis of the electroosmotic flow in a bare fused-silica capillary.

For large-volume stacking with the electroosmotic flow pump (LVSEP) in capillary electrophoresis of anionic analytes it is required that the electroosmotic mobility (EOM) should be smaller than the magnitudes of the effective mobilities of the analytes. When a fused-silica capillary is treated with an acidic solution, the silanoate group on the silica surface is neutralized to silanol and the EOM is suppressed. Due to the slow deprotonation equilibrium of the silanol group at an intermediate pH, this reduced EOM can be retained during a number of electrophoresis runs. Using a bare fused-silica capillary preconditioned with 0.01 M HCl, successful LVSEP at pH 6.0 was achieved for weakly acidic compounds with two orders of magnitude enhancements in the concentration sensitivity. The repeatability in migration times of ten analytes stacked by LVSEP in a single day was excellent with the relative standard deviation (RSD) less than 1% (n = 6). The day-to-day repeatability was also excellent with RSD less than 3% (n = 3 x 6) when the capillary was preconditioned each day.

Benzene Derivatives↗
PubMed2006

In-capillary solid-phase extraction-capillary electrophoresis for the determination of chlorophenols in water.

A novel CE method combined with SPE in a single capillary was developed for analysis of chlorophenols in water. A frit of 0.5 mm was first made by a sol-gel method, followed by packing a SPE sorbent in the inlet end of the capillary. Two phenol derivatives, 2,4-dichlorophenol and 2,4,5-trichlorophenol, were used as the model compounds. By loading sample solutions into the capillary, the two chlorophenols were extracted into the sorbent. They were desorbed by injecting only about 4 nL of methanol. Finally, the analytes were separated by conventional CE. The technique provided a concentration enhancement factor of over 4000-fold for both chlorophenols. The detection limits (S/N = 3) of 2,4-dichlorophenol and 2,4,5-trichlorophenol were determined to be 0.1 ng/mL and 0.07 ng/mL, respectively. For replicate analyses of 5 ng/mL of 2,4-dichlorophenol, within-day and between-day RSDs of migration time, peak height and peak area were in the range of 1.8-2.0%, 4.0-4.4% and 4.1-4.6%, respectively. The method shows wide linear range, acceptable reproducibility and excellent sensitivity, and it was applied to the analyses of spiked river water samples. The capillary packed with the SPE sorbents can be used for more than 400 runs without performance deterioration.

Chlorophenols↗
PubMed2006

Efficient and highly reproducible capillary electrophoresis-mass spectrometry of peptides using Polybrene-poly(vinyl sulfonate)-coated capillaries.

The potential of capillaries noncovalently coated with a bilayer of oppositely charged polymers for the analysis of peptides by CE-MS was investigated. Bilayer coatings were produced by subsequently rinsing fused-silica capillaries with a solution of Polybrene (PB) and poly(vinyl sulfonate) (PVS). The PB-PVS coating showed to be fully compatible with MS detection causing no ionization suppression or background signals. The bilayer coating provided a considerable EOF at low pH, thereby facilitating the fast separation of peptides using a BGE of formic acid (pH 2.5). Under optimized CE-MS conditions, for enkephalin peptides high separation efficiencies were obtained with plate numbers in the range of 300,000-500,000. It is demonstrated that both the cancellation of the hydrodynamic capillary flow induced by the nebulizer gas and a sufficiently high-data acquisition rate are crucial for achieving these efficiencies. The overall performance of the CE-MS system using PB-PVS-coated capillaries was evaluated by the analysis of a tryptic digest of cytochrome c. The system provided an efficient separation of the peptide mixture, which could be effectively monitored by MS/MS detection allowing identification of at least 13 peptides within a time interval of 1.5 min. In addition, the PB-PVS coating proved to be very consistent yielding stable CE-MS patterns with highly favorable migration time reproducibilities (RSDs < 1% over a 3-day period).

Electrophoresis, Capillary↗
PubMed1998

Capillary electrophoresis of insulin-like growth factors: enhanced ultraviolet detection using dynamically coated capillaries and on-line solid-phase extraction.

Insulin-like growth factor-I and -II (IGF-I and IGF-II) are difficult to separate and measure as a result of their homology, both structurally and immunologically. A number of binding proteins (BPs) which interact with the IGFs with high affinity complicate the ability to measure the IGFs accurately and reproducibly. Current methodology for measuring IGF is immuno-based and involves dissociation from the IGFs and removal of the binding proteins through sample acidification and removal by solid-phase adsorption. However, the net result is an assay that is time-consuming and, at best, semiquantitative. In an attempt to improve the reproducibility and accuracy of IGF-I and -II measurement, electrophoretic systems employing dynamically coated and bare silica capillaries were evaluated. Separations in bare silica capillaries in the presence or absence of the cationic additive, decamethonium bromide were ineffective for resolving IGF-I and IGF-II. However, when the capillary was coated dynamically with polybrene, IGF-I and -II could be resolved in a BSA sample matrix using a low pH buffer. Despite the fact that the IGFs could be resolved in the presence of an IGF-I analog used as an internal standard, polybrene recoating was required after as few as 12 runs and poor coating-to-coating reproducibility was observed. Use of polydiallyldimethylammonium chloride (PDMAC) as a dynamic cationic coating and a low pH buffer containing 0.5% PDMAC was found to be much more effective, providing reproducible separation of IGF-I and -II. It was found that PDMAC need not be included in the separation buffer to obtain reproducible analyses regarding IGF separation. Subsequently, functionality remained intact for as many as 35-40 consecutive analyses before recoating was required. Without the need for PDMAC in the buffer, on-line solid-phase extraction-capillary electrophoresis could be accomplished for detection of IGF-I and -II at concentrations as low 195 ng/ml.

Buffers↗
PubMed1975

Fenestrated blood capillaries and lymphatic capillaries in rat skeletal muscle.

Capillary fenestrae occur in one of about 60 cross-sectioned blood capillaries in normal adult rat skeletal muscles. The fenestrae occur singly or in groups. Fenestrated capillaries are found close to muscle fibers as well as in the perimysial and perineurial connective tissue. Small numbers of lymphatic capillaries are also present, mostly in the perimysial connective tissue.

Animals↗
PubMed1992

Flow patterns of blood cells in the retinal capillaries. Retinal capillary flow patterns.

We present a new technique for retinal blood cell angiography which was used to investigate flow patterns of blood cells in the retinal capillary net of normal cats. Capillary paths were defined to be the path taken by the labelled blood cells from the terminal arteriole to the entry point into a collecting venule. We were able to define two types of capillary paths. The 'simple' paths were minimally coiled and had a high blood cell flux. The 'complex' paths were coiled, structurally complex and had a low blood cell flux in comparison to the simple paths of the same eye. A simultaneous fluorescein angiogram was performed to reveal the complete anatomy of the capillary net in which the functional paths exist. The possibility that such flow patterns exist in the human retina should be considered.

Animals↗