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1.
Magdalena C. Waldhier Michael A. Gruber Katja Dettmer Peter J. Oefner 《Analytical and bioanalytical chemistry》2009,394(3):695-706
Free amino acids are typically quantified as the sum of their enantiomers, because in terrestrial organisms they mainly exist
in the left-handed form. However, with increasing understanding of the biological significance of right-handed amino acids
interest in enantioselective quantification of amino acids has steadily increased. Initially, electrophoretic and chromatographic
methods using chiral (pseudo)-stationary phases or chiral eluents were applied to the separation of amino acid enantiomers.
Later, derivatization of amino acids prior to chromatography with chiral reagents gained in popularity, because the diastereomers
formed can be resolved on conventional reversed-phase columns. Novel multi-interaction chiral columns turned attention back
to direct chiral chromatographic methods. Hyphenation to mass spectrometry has increasingly replaced optical detection because
of superior selectivity, although this has not obviated the need for baseline resolution of amino acid enantiomers. Despite
the progress made, enantioselective separation and quantification of amino acids remains an analytical challenge owing to
frequently incomplete resolution of all naturally occurring enantiomers and insufficient sensitivity for the determination
of the trace amounts of d-amino acids typically found in biological fluids and tissues.
Chiral GC-MS analysis of heptafluorobutanol/pentafluoropropionanhydride amino acid derivatives on an Rt-gDEXsa column 相似文献
2.
C. R. Dockery A. R. Stefan A. A. Nieuwland S. N. Roberson B. M. Baguley J. E. Hendrix S. L. Morgan 《Analytical and bioanalytical chemistry》2009,394(8):2095-2103
Systematic designed experiments were employed to find the optimum conditions for extraction of direct, reactive, and vat dyes
from cotton fibers prior to forensic characterization. Automated microextractions were coupled with measurements of extraction
efficiencies on a microplate reader UV–visible spectrophotometer to enable rapid screening of extraction efficiency as a function
of solvent composition. Solvent extraction conditions were also developed to be compatible with subsequent forensic characterization
of extracted dyes by capillary electrophoresis with UV–visible diode array detection. The capillary electrophoresis electrolyte
successfully used in this work consists of 5 mM ammonium acetate in 40:60 acetonitrile–water at pH 9.3, with the addition
of sodium dithionite reducing agent to facilitate analysis of vat dyes. The ultimate goal of these research efforts is enhanced
discrimination of trace fiber evidence by analysis of extracted dyes.
Figure Fitted absorbance response surface for extraction of a direct dye, C. I. yellow 58, using a ternary solvent system. 相似文献
3.
Martinez Vazquez R Osellame R Cretich M Chiari M Dongre C Hoekstra HJ Pollnau M van den Vlekkert H Ramponi R Cerullo G 《Analytical and bioanalytical chemistry》2009,393(4):1209-1216
We use direct femtosecond laser writing to integrate optical waveguides into a commercial fused silica capillary electrophoresis
chip. High-quality waveguides crossing the microfluidic channels are fabricated and used to optically address, with high spatial
selectivity, their content. Fluorescence from the optically excited volume is efficiently collected at a 90° angle by a high
numerical aperture fiber, resulting in a highly compact and portable device. To test the platform we performed electrophoresis
and detection of a 23-mer oligonucleotide plug. Our approach is quite powerful because it allows the integration of photonic
functionalities, by simple post-processing, into commercial LOCs fabricated with standard techniques.
Figure Femtosecond laser written waveguides can selectively excite fluorescence in a microfluidic channel of a commercial lab-on-a-chip.
A compact scheme for on-chip detection by laser induced fluorescence is applied to capillary electrophoresis of a 23-mer Cy3-labeled
oligonucleotide 相似文献
4.
Kuroda D Zhang Y Wang J Kaji N Tokeshi M Baba Y 《Analytical and bioanalytical chemistry》2008,391(7):2543-2549
A thermo-responsive separation matrix, consisting of Pluronic F127 tri-block copolymers of poly(ethylene oxide) and poly(propylene
oxide), was used to separate DNA fragments by microchip electrophoresis. At low temperature, the polymer matrix was low in
viscosity and allowed rapid loading into a microchannel under low pressure. With increasing temperatures above 25°C, the Pluronic
F127 solution forms a liquid crystalline phase consisting of spherical micelles with diameters of 17–19 nm. The solution can
be used to separate DNA fragments from 100 bp to 1500 bp on poly(methyl methacrylate) (PMMA) chips. This temperature-sensitive
and viscosity-tunable polymer provided excellent resolution over a wide range of DNA sizes. Separation is based on a different
mechanism compared with conventional matrices such as methylcellulose. To illustrate the separation mechanism of DNA in a
Pluronic F127 solution, DNA molecular imaging was performed by fluorescence microscopy with F127 polymer as the separation
matrix in microchip electrophoresis.
Figure Temperature dependence of the viscosity of 20% w/w Pluronic F127 solution in 1xTBE buffer. Dotted approximates resultant curve. 相似文献
5.
A rapid and effective method was developed for the chiral separation of raltitrexed (RD) enantiomers by carboxymethyl-beta-cyclodextrin
(CM-β-CD)-modified micellar electrokinetic chromatography (MEKC). Optimization of conditions including the type and concentration
of the chiral selector, concentration of sodium dodecyl sulfate (SDS), pH and concentration of the background electrolyte
(BGE), capillary temperature, and applied voltage was investigated. The enantiomers of raltitrexed could be separated with
satisfactory resolution and linear response by using 75 mM Tris-phosphate at pH 8.0 containing 30 mM SDS and 8 mM CM-β-CD
as buffer system. Furthermore, the usefulness of this method was demonstrated in a purity test of a real synthetic drug sample.
Figure Chiral separation of raltitrexed by CM-β-CD MEKC was optimized and applied to test the purity of a synthetic drug sample 相似文献
6.
Amy R. Stefan Christopher R. Dockery Alexander A. Nieuwland Samantha N. Roberson Brittany M. Baguley James E. Hendrix Stephen L. Morgan 《Analytical and bioanalytical chemistry》2009,394(8):2077-2085
The extraction and separation of dyes present on textile fibers offers the possibility of enhanced discrimination between
forensic trace fiber evidence. An automated liquid sample handling workstation was programmed to deliver varying solvent combinations
to acid-dyed nylon samples, and the resulting extracts were analyzed by an ultraviolet/visible microplate reader to evaluate
extraction efficiencies at different experimental conditions. Combinatorial experiments using three-component mixture designs
varied three solvents (water, pyridine, and aqueous ammonia) and were employed at different extraction temperatures for various
extraction durations. The extraction efficiency as a function of the three solvents (pyridine/ammonia/water) was modeled and
used to define optimum conditions for the extraction of three subclasses of acid dyes (anthraquinone, azo, and metal complex)
from nylon fibers. The capillary electrophoresis analysis of acid dye extracts is demonstrated using an electrolyte solution
of 15 mM ammonium acetate in acetonitrile/water (40:60, v/v) at pH 9.3. Excellent separations and discriminating diode array spectra are obtained even for dyes of similar color.
Figure Capillary electropherogram of three acid dyes extracted from nylon 6,6 thread 相似文献
7.
Patterson EE Piyankarage SC Myasein KT Pulido JS Dundervill RF Hatfield RM Shippy SA 《Analytical and bioanalytical chemistry》2008,392(3):409-416
A low-volume automated injection system for the analysis of chemically complex, amino acid samples is presented. This system
utilizes submicroliter sample volumes stored on a 75-μm inner diameter capillary. A pulse of positive pressure (82 kPa) is
used to load nanoliter sample volumes into an in-house fabricated interface and onto a separation capillary. Residual sample
solution in the interface is immediately washed away by a continuous transverse flow through the injection interface, yielding
a sharp and reproducible sample plug. By performing multiple injections of a static sample, one may average the signals to
yield a signal-to-noise ratio improvement of up to 4.07-fold for 20 injections compared with a theoretical maximum of a 4.47-fold
improvement. Without interruption of the applied voltage, injections performed every 150 s were used to monitor the progress
of the reaction of multiple amino acids with the fluorogenic dye 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde. Analysis
of dialyzed clinical vitreous samples demonstrates the resolution and quantitation of arginine, lysine, leucine, glutamine,
and glutamate. Observed levels are comparable with those of nonautomated injection methods and reports by others.
Figure Multiple injections of fluorescently labeled human vitreous with a detailed view of a single injection (above) and with all injections
segmented and averaged for signal-to-noise ratio improvement (right) 相似文献
8.
Amino acids are important targets for metabolic profiling. For decades, amino acid analysis has been accomplished by either
cation-exchange or reversed-phase liquid chromatography coupled to UV absorbance or fluorescence detection of pre-column or
post-column-derivatized amino acids. Recent years have seen great progress in the development of direct-infusion or hyphenated
mass spectrometry in the analysis of free amino acids in physiological fluids, because mass spectrometry not only matches
optical detection in sensitivity, but also offers superior selectivity. The advent of cryo-probes has also brought NMR spectroscopy
within the detection limits required for the analysis of free amino acids. But there is still room for further improvement,
including expansion of the analyte spectrum, reduction of sample preparation and analysis time, automation, and synthesis
of affordable isotope standards.
Figure Fully automated gas chromatography-mass spectrometry analysis of amino acids. 相似文献
9.
The use of polymers in microchip fabrication affords new opportunities for the development of powerful, miniaturized separation
techniques. One method in particular, the use of phase-changing sacrificial layers, allows for simplified designs and many
additional features to the now standard fabrication of microchips. With the possibility of adding a third dimension to the
design of separation devices, various means of enhancing analysis now become possible. The application of phase-changing sacrificial
layers in microchip analysis systems is discussed, both in terms of current uses and future possibilities.
Figure Phase-changing sacrificial materials enable multilayer microfluidic device layouts 相似文献
10.
Zaher M Ravelet C Baussanne I Ravel A Grosset C Décout JL Peyrin E 《Analytical and bioanalytical chemistry》2009,393(2):655-660
In this paper, we describe the preparation and the evaluation of a porous graphitic carbon (PGC) column coated with a new
dinaphthyl derivative of neamine for chiral ligand-exchange (LE) chromatography. It was shown that the graphitic surface/dinaphthyl
anchor system efficiently (1.15 μmol/m2) and stably (three months of intensive use) adsorbs the neamine template onto the chromatographic support. The resulting
coated PGC stationary phase showed appreciable LE-based enantioselective properties towards several native amino acids.
Chromatographic separation of methionine enantiomers using a dinaphtyl neamine-based ligand-exchange chiral stationary phase 相似文献
11.
Ice chromatography, in which water-ice particles are employed as a chromatographic stationary phase, has proven an efficient
technique for probing the solution/ice interface. The preparation of fine ice particles has allowed us to not only obtain
higher-resolution separation but also investigate the molecular processes occurring on the ice surface in more detail. Chromatographic
investigations have revealed that two or more hydrogen bonds are simultaneously formed between a solute and the dangling bonds
on the ice surface when the solute gives measurable retention. Several compounds, including estrogens, amino acids, and acyclic
polyethers, have been successfully separated by ice chromatography with a hexane-based mobile phase. In addition, this method
effectively probes the surface melting of the ice stationary phase and the liquid phase that coexists with water ice at thermodynamic
equilibrium. The thickness of the surface liquid layer and the size of the liquid phase that grows inside an ice particle
have been evaluated. The perspectives of this method are also discussed.
相似文献
12.
Because variability exists within populations of cells, single-cell analysis has become increasingly important for probing
complex cellular environments. Capillary electrophoresis (CE) is an excellent technique for identifying and quantifying the
contents of single cells owing to its small volume requirements and fast, efficient separations with highly sensitive detection.
Recent progress in both whole-cell and subcellular sampling has allowed researchers to study cellular function in the areas
of neuroscience, oncology, enzymology, immunology, and gene expression.
相似文献
13.
Tuulia Hyötyläinen 《Analytical and bioanalytical chemistry》2009,394(3):743-758
Sample preparation before chromatographic separation is the most time-consuming and error-prone part of the analytical procedure.
Therefore, selecting and optimizing an appropriate sample preparation scheme is a key factor in the final success of the analysis,
and the judicious choice of an appropriate procedure greatly influences the reliability and accuracy of a given analysis.
The main objective of this review is to critically evaluate the applicability, disadvantages, and advantages of various sample
preparation techniques. Particular emphasis is placed on extraction techniques suitable for both liquid and solid samples.
Figure Miniaturised extraction techniques allow sensitive analysis of also small sample volumes. 相似文献
14.
A novel on-column sequential preconcentration method based on the combination of field-amplified sample injection induced
by acetonitrile and pseudo isotachophoresis (ITP)–acid stacking is developed for simply but efficiently concentrating alkaloid
cations in a high-salt sample matrix in capillary electrophoresis. Acetonitrile (70%) added to a sample solution with a high-salt
sample matrix not only induces field-amplified sample stacking by decreasing conductivity but also acts as a termination reagent
in the succeeding pseudo ITP. After sample injection had been completed, a plug of H+ was injected electrokinetically and a neutralization reaction between H+ and tartrate from the buffer solution produced a low conductivity zone, in which the injected analyte cations were further
concentrated. With the sequential preconcentration method, a 3 orders of magnitude detection sensitivity (1,400-fold) increase
could be observed compared with the conventional electrokinetic injection method, without compromising separation efficiency
and peak shape, and detection limits of 0.1 ng/mL for myosmine and 0.3 ng/mL for anabasine with the conditions selected were
achieved. The calibration curves demonstrated good linearity in the concentration ranges 1.3–600 ng/mL for myosmine and 4.9–900 ng/mL
for anabasine, respectively. The proposed method has been used to analyze successfully trace alkaloids in cigarette samples.
Figure Sequential preconcentration processes: a sample injection; b introduction of HCl; c capillary zone electrophoresis separation. A
−
tartrate, white circles acetonitrile, black circles Na+, sample zone, myosmine, anabasine 相似文献
15.
A simple method based on capillary electrophoresis with potential gradient detection was developed to separate and detect
neomycin components within 4 min without a derivatization step. Satisfactory separation and good repeatability were obtained
using a separation buffer composed of 1 mM ammonium citrate (pH 3.5). The linearity of the method ranged from 10 to 1000 ppm with a limit of detection for neomycin B
of about 7 ppm. After a simple dilution and filtering pretreatment step, neomycin components in three real samples were successfully
analyzed without any major interference. Due to its simplicity and reliability, this method could provide an excellent alternative
to the assays currently listed in U.S. and European Pharmacopoeia. The experiments were performed on a portable capillary
electrophoresis system and, hence, the method can be readily applied to field analysis and point-of-care testing.
Figure Photo of portable CE-P2-PGD system 相似文献
16.
Lillian Roth Jutta Zagon Anke Ehlers Lothar W. Kroh Hermann Broll 《Analytical and bioanalytical chemistry》2009,394(2):529-537
A new approach for the detection of DNA target molecules is described, using capture probes and subsequent signal enhancement
by a uniform polymerase chain reaction (PCR). Peptide nucleic acid probes were immobilized in real-time PCR-compatible microtiter
plates. After hybridization of biotinylated DNA targets, detection was performed by real-time immuno-PCR, a method formerly
used for protein detection. We demonstrate the feasibility of this strategy for the qualitative detection of DNA oligonucleotides
with a detection limit (LOD) of 6 attomol. Furthermore, the method was applied to PCR-amplified samples from genetically modified
maize DNA (Mon810). A 483-bp DNA fragment was detected in mixture with 99.9% of noncomplementary DNA with a sensitivity down
to the level of attomole.
Figure 相似文献
17.
Tastet L Schaumlöffel D Bouyssiere B Lobinski R 《Analytical and bioanalytical chemistry》2006,385(5):948-953
A method based on ICP collision-cell MS detection in capillary HPLC was developed to gain an insight into the purity and identity of selenium-containing proteins separated by 1-D and 2-D electrophoresis. The bands and spots obtained after the separation of water-soluble proteins in selenized yeast were digested with trypsin prior to chromatography. Selenium could be detected down to the subpicogram level. The method, assisted by information obtained by MALDI TOF MS on the 5000 Da cut-off fraction, permitted the purity of bands and spots to be estimated and the efficiency of tryptic digestion and the quantity of selenium present in individual peptides to be evaluated. Owing to the high sensitivity and the lack of matrix suppression effects, the method provided chromatograms with signal-to-noise ratios of 10–1000 in conditions where the common ES Q–TOF MS detection failed.
相似文献
18.
Bendrysheva SN Proskurnin MA Pyell U Faubel W 《Analytical and bioanalytical chemistry》2006,385(8):1492-1503
It is shown that organo-aqueous separation buffers show much promise when used in capillary electrophoresis separations with
photothermal (thermal lens) detection systems. Acetonitrile–water and methanol–water mixtures were selected, as conventionally
used in capillary electrophoresis. It is shown that, despite more sophisticated experimental conditions (significant heat
outflow from the capillary body) and peak detection, the theoretical ratio of the thermal lens signal for a binary mixture
to the thermal lens signal for an aqueous solution (or the corresponding ratio obtained experimentally under bulk batch conditions)
can be used to predict the sensitivity of thermal lens detection in capillary electrophoresis. The limits of detection for
2-, 3-, and 4-nitrophenols selected as model compounds in 70% v/v acetonitrile separation buffers are 1×10−6 M, 1×10−6 M and 3×10−7 M, respectively, and are therefore decreased by a factor of six compared to thermal lens detection in aqueous separation
buffers. The overall increase in the thermal lens detection sensitivity in a 100% ACN buffer is a factor of 13.
相似文献
19.
Free-flow electrophoresis (FFE) is a technique that performs an electrophoretic separation on a continuous stream of analyte
as it flows through a planar flow channel. The electric field is applied perpendicularly to the flow to deflect analytes laterally
according to their mobility as they flow through the separation channel. Miniaturization of FFE (μFFE) over the past 15 years
has allowed analytical and preparative separation of small volume samples. Advances in chip design have improved separations
by reducing interference from bubbles generated by electrolysis. Mechanisms of band broadening have been examined theoretically
and experimentally to improve resolution in μFFE. Separations using various modes such as zone electrophoresis, isoelectric
focusing, isotachophoresis, and field-step electrophoresis have been demonstrated.
Michael T. Bowser is currently an Associate Professor at the University of Minnesota where he has been a faculty member in the Department of Chemistry since 2000. Michael was the 2005 recipient of the ACS Award for Young Investigators in Separation Science. His research interests include microfluidic devices, high-speed neurotransmitter measurements and techniques for isolating high-affinity aptamers. 相似文献
Michael T. BowserEmail: |
Michael T. Bowser is currently an Associate Professor at the University of Minnesota where he has been a faculty member in the Department of Chemistry since 2000. Michael was the 2005 recipient of the ACS Award for Young Investigators in Separation Science. His research interests include microfluidic devices, high-speed neurotransmitter measurements and techniques for isolating high-affinity aptamers. 相似文献
20.
We have developed a concise tool for the investigation of the transition of humic substances in environmental water. The separation
of water-soluble humic substances was achieved rapidly and effectively by capillary electrophoresis using a polyacrylamide-coated
capillary and a phosphate electrophoretic buffer solution (pH 7.0) containing hydroxyethyl cellulose. The separation mechanism
was assessed using the ultrafiltration technique. The effect of the complexation of humic substances with metal ions was studied
by using the proposed method. When Fe(III) ions or EDTA was added to the sample solution of fulvic acid, a distinct change
in the electropherogram pattern based on the conformational change of fulvic acid was observed. The successful application
of the proposed method to the characterization of humic substances in a river water sample was also demonstrated.
Figure Addition of Fe(III) ions or EDTA to a solution containing fulvic acid (FA) results in a distinct change in the electropherogram
pattern, which reflects the conformational change of FA: this forms the basis for the characterization of humic substances
in river water samples 相似文献