共查询到20条相似文献,搜索用时 31 毫秒
1.
Webb A 《Analytical and bioanalytical chemistry》2007,388(3):525-528
Figure Schematic diagram of a typical arrangement used for hyphenating chemical microseparations (e.g. capillary HPLC, CE, or CEC)
with microcoil NMR detection 相似文献
2.
Arya SK Datta M Singh SP Malhotra BD 《Analytical and bioanalytical chemistry》2007,389(7-8):2235-2242
Cholesterol oxidase (ChOx), cholesterol esterase (ChEt), and horseradish peroxidase (HRP) have been co-immobilized covalently
on a self-assembled monolayer (SAM) of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTS) deposited on an indium–tin–oxide (ITO) glass surface. These enzyme-modified
(ChOx-ChEt-HRP/AEAPTS/ITO) biosensing electrodes have been used to estimate cholesteryl oleate from 10 to 500 mg dL−1. The sensitivity, K
m value, and shelf-life of these ChEt-ChOx-HRP/AEAPTS/ITO biosensing electrodes have been found to be 124 nA mg−1 dL, 95.098 mg dL−1 (1.46 mmol L−1), and ten weeks, respectively. The ChEt-ChOx-HRP/AEAPTS/ITO bio-electrodes have been used to estimate total cholesterol in
serum samples.
Figure Covalent immobilization of enzymes onto AEAPTS/ITO surface using EDC/NHS chemistry
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Surmeian A Diplasu C Groza A Ganciu M Belenguer P Tempez A Chapon P 《Analytical and bioanalytical chemistry》2007,388(8):1625-1629
A high-current pulsed hollow cathode discharge was used to study the role of atomic and ionic metastables involved in ionization
plasma processes. We observed the enhancement of the spectral emission lines of noble gas ions in the afterglow. A study of
the processes that involve atomic and ionic metastables is of great interest since it should lead to a better understanding
of and enhanced control over the ionization mechanisms crucial to analytical glow discharge mass spectrometry (GDMS) analysis.
Figure Time profile of Ti, Ti+, and Ne+ spectral lines 相似文献
4.
Ortner K Sivanandam VN Buchberger W Müller N 《Analytical and bioanalytical chemistry》2007,388(1):173-177
Enzymatically cleaved glycans from sub-milligram quantities of erythropoietin (EPO) and ovalbumin have been analyzed, without
further purification, by two-dimensional diffusion-ordered nuclear magnetic resonance spectroscopy. At NMR sample concentrations
below 50 μmol L−1 the major components of the oligosaccharide fractions could be distinguished by their anomeric proton chemical shift and
their size-dependent diffusion coefficients.
Figure
1H NMR diffusion decay curves of anomeric protons in the EPO glycan fraction 相似文献
5.
We have developed an iterative procedure for predicting the retention times of polycyclic aromatic hydrocarbons (PAHs) and
n-alkanes during separations by temperature-programmed gas chromatography. The procedure is based on estimates of two thermodynamic
properties for each analyte (the differences in enthalpy and entropy associated with movements between the stationary and
mobile phases) derived from data acquired experimentally in separations under isothermal conditions at temperatures spanning
the range covered by the temperature programs in ten-degree increments. The columns used for this purpose were capillary columns
containing polydimethylsiloxane-based stationary phases with three degrees of phenyl substitution (0%, 5%, and 50%). Predicted
values were mostly within 1% of experimentally determined values, implying that the method is stable and precise.
Figure Predicted values were mostly within 1 % of experimentally determined values, thus implying that the method is stable and precise 相似文献
6.
A nonradioactive 31P nuclear magnetic resonance (NMR) spectroscopy protocol has been developed and used to investigate in vitro autophosphorylation of insulin receptors. Optimum experimental conditions have been explored, and the effects of Mn2+ and phosphocreatine (PCr) on the determination of the phosphorylation reaction have been assayed. The method was used to monitor the time courses of the phosphorylation reaction in solution. The results from this NMR study were in agreement with observations of insulin receptor phosphorylation made by using Western blotting.
相似文献
7.
Pérez Pavón JL García Pinto C Guerrero Peña A Moreno Cordero B 《Analytical and bioanalytical chemistry》2008,391(2):599-607
In the present work we report the results obtained with a methodology based on direct coupling of a headspace generator to
a mass spectrometer for the identification of different types of petroleum crudes in polluted soils. With no prior treatment,
the samples are subjected to the headspace generation process and the volatiles generated are introduced directly into the
mass spectrometer, thereby obtaining a fingerprint of volatiles in the sample analysed. The mass spectrum corresponding to
the mass/charge ratios (m/z) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization
of the samples. The signals obtained for the different samples were treated by chemometric techniques to obtain the desired
information. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation
are required. The method is rapid, simple and, in view of the results, highly promising for the implementation of a new approach
for oil spill identification in soils.
Figure PCA score plots illustrate clear discrimination of types of crude oil in polluted soil samples (e.g. results are shown for
vertisol) 相似文献
8.
The application of near-infrared (NIR) dyes (λ
em > 750 nm) to the analysis of biological samples shows much promise, because the long emission wavelengths of such dyes allow
interferences from biomolecule matrices to be minimized. In this paper, a novel NIR dye, 5,5′-dicarboxy-1,1′-disulfobutyl-3,3,3′,3′-tetramethylindotricarbocyanine
(DCDSTCY) has been developed for the spectrophotometric determination of total protein in serum. Under acidic conditions,
the binding of DCDSTCY to proteins caused a new peak at 878 nm, the height of which was proportional to the concentration
of protein. The linear range of the method was found to be 0.04–0.5 μg mL−1 for bovine serum albumin (BSA) and human serum albumin (HSA), and detection limits of 5 ng mL−1 were obtained for these substances. The maximum binding number of BSA with DCDSTCY was measured to be 133. The method proposed
here has been applied to the quantitation of total protein in serum, and recoveries of 96.6–104% were achieved.
Figure Near-infrared probe for protein determination 相似文献
9.
Wax, 85% of which consists of orthorhombic crystals, has been found in the cocoon of the hornet Vespa analis Fabricius by means of high-resolution 13C solid-state nuclear magnetic resonance (NMR). GC–MS analysis revealed the major components of the wax in the cocoon were
linear alkenes and alkanes with a total of 23 or 34 carbon atoms. At 40.7 °C a DSC absorption peak and a 13C NMR chemical shift change were observed and interpreted as the result of a crystal transition from the orthorhombic to rotator
phase of the wax molecules. At 55.5 °C melting of the wax was observed. The amount of crystalline wax deposition varied with
the part of the cocoon—crystalline wax was concentrated in the silk sleeve lining the inner wall of each comb cell but there
was very little in the silk cap projecting from the end of each cell. Because the wax components of the larval cocoon were
almost identical to those of the larval cuticle, despite a slight difference in the profiles, they might have come from the
larval cuticle via direct body contact with the cocoon.
Figure Cocoon of the hornet Vespa analis Fabricius 相似文献
10.
Martens T Bogaerts A Brok W van Dijk J 《Analytical and bioanalytical chemistry》2007,388(8):1583-1594
A model developed for a dielectric barrier discharge (DBD) in helium, used as a new spectroscopic source in analytical chemistry,
is presented in this paper. The model is based on the fluid approach and describes the behavior of electrons, He+ and ions, He metastable atoms, He atoms in higher excited levels, and He2 dimers. The He ground-state atoms are regarded as background gas. The characteristic effect of charging/discharging of the
dielectrics which cover both electrodes is also simulated. Typical results of the model include the distribution of potential
inside the plasma (and the potential drop across the dielectrics), the electric current and gap voltage as a function of time
for a given applied potential profile, the spatial and temporal number-density profiles of the different plasma species, and
the relative contributions of the mechanisms of their production and loss.
Figure Schematic diagram of the dielectric barrier discharge (left) and typical temporal profiles of voltage and current, as obtained
from the simulations (right) 相似文献
11.
Ma X Zhu T Xu H Li G Zheng J Liu A Zhang J Du H 《Analytical and bioanalytical chemistry》2008,390(4):1133-1137
A chemical prototype sensor was constructed based on nanofiber-structured TiO2 and highly sensitive quartz resonators. The gas-sensing behavior of this new sensor to selected simulant warfare agents was
investigated at room temperature. Results showed rapid response and good reversibility of this sensor when used with high-purity
nitrogen. This provides a simple approach to preparation of materials needed as chemical sensors for selected organic volatiles
or warfare agents.
Figure Sensing behavior of TiO2 nanofiber sensor to chemical vapors 相似文献
12.
Solution-enhanced dispersion by supercritical fluids (SEDS) was applied to produce nano-sized recombinant human growth hormone
(hGH) particles. Ethanol was used to help the supercritical carbon dioxide to extract water from the aqueous protein solution.
Various sizes of hGH nanoparticles were successfully prepared with a narrow particle size distribution from aqueous ethanol
solution without using any additive. The theoretical particle sizes were deduced from the calculated droplet sizes based on
a modified Jasuja’s equation. The calculated mean particle sizes and the experimentally obtained ones were compared and the
results showed an excellent correlation coefficient (R
2) of 0.995.
Figure Distribution of hGH Nano-particles 相似文献
13.
Han X Wang C He L Beesley TE Armstrong DW 《Analytical and bioanalytical chemistry》2007,387(8):2681-2697
A new synthetic polymeric chiral stationary phase for liquid chromatography was prepared via free-radical-initiated polymerization
of trans-9,10-dihydro-9,10-ethanoanthracene-(11S,12S)-11,12-dicarboxylic acid bis-4-vinylphenylamide. The new polymeric chiral stationary phase (CSP) showed enantioselectivity
for many chiral compounds in multiple mobile phases. High stability and sample capacities were observed on this polymeric
chiral stationary phase. Mobile phase components and additives affected chiral separation greatly. This new synthetic chiral
stationary phase is complementary to two other related commercially available CSPs: the P-CAP and P-CAP-DP columns. Interactions
between the chiral stationary phase and analytes that lead to retention and chiral recognition include hydrogen bonding, dipolar,
and π–π interactions. Repulsive (steric) interactions also contribute to chiral recognition.
Figure LC chromatograms showing the analytical (blue) and preparative (red) separations of N-(3,5-dinitrobenzoylleucine) enantiomers on a new synthetic polymeric chiral stationary phase 相似文献
14.
Goryacheva IY Basova EY Van Peteghem C Eremin SA Pussemier L Motte JC De Saeger S 《Analytical and bioanalytical chemistry》2008,390(2):723-727
A rapid easy-to-use immunoassay was optimised for the non-instrumental detection of ochratoxin A (OTA) in beer. The analytical
method involves preconcentration on the immunoaffinity layer inside a column followed by direct competitive ELISA detection
in the same layer. The visual cut-off value, i.e. the lowest OTA concentration resulting in no colour development, was 0.2 μg
L-1. Assay validation was performed using samples spiked with OTA. Thirty-seven naturally contaminated samples were screened
with the gel-based method developed and no false-negative results were obtained. The method described offers a simple, rapid
and cost-effective screening tool, thus contributing to better health protection of consumers.
Figure Gel-based immunoassay of spiked beer samples. 相似文献
15.
A new post-chemiluminescence (PCL) phenomenon was observed when phenothiazine medications were injected into the reaction
mixture after the chemiluminescence (CL) reaction of luminol and potassium ferricyanide had finished. A possible reaction
mechanism was proposed based on studies of the kinetic characteristics of the CL, CL spectra, fluorescence spectra, and on
other experiments. The feasibility of determining various phenothiazine medications by utilizing these PCL reactions was examined.
A molecular imprinting–post-chemiluminescence (MI-PCL) method was established for the determination of chlorpromazine hydrochloride
using a chlorpromazine hydrochloride-imprinted polymer (MIP) as the recognition material. The method displayed high selectivity
and high sensitivity. The linear range of the method was 1.0×10−8∼1.0×10−6, with a linear correlation coefficient of 0.9985. The detection limit was 3×10−9 g/ml chlorpromazine hydrochloride, and the relative standard deviation for a 1.0×10−7 g/ml chlorpromazine hydrochloride solution was 4.0% (n=11). The method has been applied to the determination of chlorpromazine hydrochloride in urine and animal drinking water
with satisfactory results.
相似文献
16.
Determination of norfloxacin in human urine by capillary electrophoresis with electrochemiluminescence detection 总被引:3,自引:0,他引:3
A fast and sensitive approach that can be used to detect norfloxacin in human urine using capillary electrophoresis with end-column
electrochemiluminescence (ECL) detection of is described. The separation column was a 75-μm i.d. capillary. The running buffer was 15 mmol L−1 sodium phosphate (pH 8.2). The solution in the detection cell was 50 mmol L−1 sodium phosphate (pH 8.0) and 5 mmol L−1
The ECL intensity varied linearly with norfloxacin concentration from 0.05 to 10 μmol L−1. The detection limit (S/N=3) was 0.0048 μmol L−1, and the relative standard deviations of the ECL intensity and the migration time for eleven consecutive injections of 1.0 μmol L−1 norfloxacin (n=11) were 2.6% and 0.8%, respectively. The method was successfully applied to the determination of norfloxacin spiked in human
urine without sample pretreatment. The recoveries were 92.7–97.9%.
相似文献
17.
Berchmans S Vergheese TM Kavitha AL Veerakumar M Yegnaraman V 《Analytical and bioanalytical chemistry》2008,390(3):939-946
The present work describes, for the first time, in situ electrochemical preparation of dendrimer-encapsulated Cu nanoparticles
using a self-assembled monolayer of fourth-generation amine-terminated polyamidoamine (PAMAM) dendrimer as the template. Atomic
force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) studies of the modified surface confirmed the presence of
Cu nanoparticles entrapped in dendrimer film. Au electrode modified with a monolayer of the dendrimer enables preconcentration
and subsequent voltammetric detection of Cu2+ at picomolar concentrations. Further, Cu nanoparticles in the dendrimer monolayer could be electrochemically derivatised
to Cu hexacyanoferrate, which exhibits specific crystal planes, unlike the random distribution of crystal planes in bulk-formed
Cu hexacyanoferrate, which is another catalytically active material for sensor applications.
Figure Electrochemical preparation of copper–dendrimer nanocomposite 相似文献
18.
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
19.
Henchoz Y Schappler J Geiser L Prat J Carrupt PA Veuthey JL 《Analytical and bioanalytical chemistry》2007,389(6):1869-1878
A rapid and universal capillary zone electrophoresis (CZE) method was developed to determine the dissociation constants (pK
a) of the 20 standard proteogenic amino acids. Since some amino acids are poorly detected by UV, capacitively coupled contactless
conductivity detection (C4D) was used as an additional detection mode. The C4D coupling proved to be very successful on a conventional CE-UV instrument, neither inducing supplementary analyses nor instrument
modification. In order to reduce the analysis time for pK
a determination, two strategies were applied: (i) a short-end injection to reduce the effective length, and (ii) a dynamic
coating procedure to generate a large electroosmotic flow (EOF), even at pH values as low as 1.5. As a result, the analysis
time per amino acid was less than 2 h, using 22 optimized buffers covering a pH range from 1.5 to 12.0 at a constant ionic
strength of 50 mM. pK
a values were calculated using an appropriate mathematical model describing the relationship between effective mobility and
pH. The obtained pK
a values were in accordance with the literature.
Figure
a UV (1) and C4D (2) detectors placed on-line on the CE capillary. b Curve of effective mobility as a function of pH for histidine 相似文献
20.
An impurity-profiling method for 3,4-methylenedioxymethamphetamine (MDMA) is presented. The impurities of interest were extracted
by solid-phase extraction (SPE) on Bakerbond C18 spe columns from a weakly alkaline solution (pH 8.5). Development of the extraction conditions covered selection of the buffer
for dissolution of the sample and the volume of the eluent used to elute the impurities. An important part of the studies
was to optimise the separation conditions, and the simplex method was used for this purpose. Cluster analysis was applied
for comparison of samples and its grouping. The developed method was based on the areas of 33 selected peaks corresponding
to MDMA impurities. All examined samples were correctly classified into clusters corresponding to the synthetic route.
相似文献