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1.
András Gergely Péter Horváth György Szász Gábor Veress 《Analytical and bioanalytical chemistry》2009,394(8):2105-2109
A three-step gradient reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the separation
of dehydroepiandrosterone (DHEA), its sulfate ester (DHEA-S), its three C7-oxidized metabolites (7αOH-DHEA, 7βOH-DHEA, 7-keto-DHEA),
and its biosynthetic congeners (androstenedione, testosterone, estradiol, pregnenolone). This new method allows the quantitative
characterization of DHEA metabolism and biosynthetic transformation under given physiological, pathological, or therapeutically
influenced circumstances. Tetrahydrofuran probably acts as a proton acceptor coadsorbent, while isopropanol behaves as a proton
donor during the separation of testosterone, estradiol, and the stereoisomers of 7-OH-DHEA.
Figure Optimized gradient RP-HPLC results in full separation of DHEA from its biosynthetic congeners and metabolites 相似文献
2.
A method based on use of functionalized gold nanoparticles on polyethylenimine film has been developed for colorimetric detection of immunoglobulin G (IgG). The immunogold nanoparticles were immobilized on quartz slides by recognition between antibody and antigen, with the antigen chemically adsorbed on the polyethylenimine film. By measurement of the UV–visible spectra of the immobilized immunogold, detection of h-IgG was achieved. The detection limit for h-IgG by use of this method can be as low as 0.01 μg mL−1. This method is quite promising for numerous applications in immunoassay.
Figure 相似文献
3.
An X-ray fluorescence method (XRF) is presented that allowed low detection limits (at the 0.1–23 ng mL−1 level) to be obtained for Cr, Mn, Fe, Ni, Zn, Sr, Pb, Bi and Br in water. The samples were prepared using a thin layer method. Trace elements were determined via the calibration curve and standard addition. Absorption effects and inhomogenities in prepared samples were checked for using the emission–transmission method and internal standards, respectively. The results from the XRF method were compared with the results from the inductively coupled plasma atomic emission spectrometry method.
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4.
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
5.
A new spectrofluorimetric method was developed for the determination of trace amounts of lecithin using the ciprofloxacin (CIP)–terbium (Tb3+) ion complex as a fluorescent probe. In a buffer solution at pH=5.60, lecithin can remarkably reduce the fluorescence intensity of the CIP–Tb3+ complex at λ=545 nm. The reduced fluorescence intensity of the Tb3+ ion is proportional to the concentration of lecithin. Optimum conditions for the determination of lecithin were also investigated. The linear range and detection limit for the determination of lecithin were 1.0×10−6–3.0×10−5 mol L−1 and 3.44×10−7 mol L−1, respectively. This method is simple, practical, and relatively free of interference from coexisting substances. Furthermore, it has been successfully applied to assess lecithin in serum samples.
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6.
J. L. López-Paz M. Catalá-Icardo B. Antón-Garrido 《Analytical and bioanalytical chemistry》2009,394(4):1073-1079
A simple, economic, sensitive and rapid method for the determination of the pesticide diquat was described. This new method
was based on the coupling of flow injection analysis methodology and direct chemiluminescent detection; to the authors’ knowledge,
this approach had not been used up to now with this pesticide. It was based on its oxidation with ferricyanide in alkaline
medium; significant improvements in the analytical signal were achieved by using high temperatures and quinine as sensitiser.
Its high throughput (144 h−1), together with its low limit of detection (2 ng mL−1), achieved without need of preconcentration steps, permitted the reliable quantification of diquat over the linear range
of (0.01–0.6) μg mL−1 in samples from different origins (river, tap, mineral and ground waters), even in the presence of a 40-fold concentration
of paraquat, a pesticide commonly present in the commercial formulations of diquat.
Figure Quartz luminometer cell 相似文献
7.
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
8.
Enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase (HRP)-catalyzed fluorescent reaction, and oxalate chemiluminescence
imaging analysis have been combined to develop a sensitive, simple, and rapid method for analysis of interferon alpha (α-IFN)
in human serum samples. A typical “sandwich type” immunoassay was used. Reaction of o-phenylenediamine (OPD) with hydrogen peroxide (H2O2), catalyzed by HRP, produced 2,3-diaminophenazine (PDA), which was detected by chemiluminescence imaging analysis with the
bis(2,4,6-trichlorophenyl)oxalate (TCPO)–H2O2–glyoxaline–PDA chemiluminescent system. The TCPO chemiluminescent imaging system is more sensitive and the chemiluminescence
quantum yield is at least five times higher than for the luminol–H2O2–HRP–PIP (p-iodophenol) chemiluminescent imaging system. The results showed there was a very good linear correlation between response
and amount of α-IFN in the range 1.3–156.0 pg mL−1 (R = 0.9991) and the detection limit was 0.8 pg mL−1 (S/N=3). The relative standard deviation (n = 9) was 4.7%. The proposed method has been used for successful analysis of the amount of α-IFN in human serum. The results
obtained compared well with those obtained by conventional colorimetric ELISA and luminol chemiluminescent ELISA.
Figure Procedures of the proposed method 相似文献
9.
Tribalat L Paisse O Dessalces G Grenier-Loustalot MF 《Analytical and bioanalytical chemistry》2006,386(7-8):2161-2168
In the framework of developing analyses for exogenous contaminants in food matrices such as honey, we have compared data obtained
by high-performance liquid chromatography coupled with mass spectrometry (LC–MS) to those provided by high-performance liquid
chromatography and tandem mass spectrometry (LC–MS–MS). Initial results obtained with LC–MS showed that the technique lacked
selectivity, which is why the method was validated by LC–MS–MS. This method involves a solid-phase extraction (SPE) of nitrofuran
metabolites and nitrofuran parent drugs, a derivatization by 2-nitrobenzaldehyde for 17 h, and finally a clean-up by SPE.
The data obtained show that the limits of detection varied between 0.2 and 0.6 μg kg−1 for the metabolites and between 1 and 2 μg kg−1 for nitrofuran parent drugs. The method was applied to different flower honeys. The results showed that nitrofurans (used
as antibiotics) are consistently present in this matrix, the predominant compound being furazolidone.
Figure Working bees 相似文献
10.
A new flow injection chemiluminescent immunoassay was developed for the detection of 17β-estradiol (E2). The method uses p–iodophenol (PIP) as enhancer and is based on a solid-phase immunoassay format in which an E2–OVA immobilized immunoaffinity column inserted in the flow system is used to trap unbound horseradish peroxidase (HRP)-labeled
anti-E2 antibody after an off-line incubation of E2 with HRP-labeled anti-E2 antibody. The trapped enzyme conjugate was detected by injecting substrates to produce an enhanced chemiluminescence (CL)
response. The linear range for E2 was 10.0–1,000.0 ng mL−1 with a correlation coefficient of 0.996 and a detection limit of 3.0 ng mL−1. The sampling and chemiluminescence detection time for one sample was 400 s after a pre-incubation procedure of 30 min. Serum
samples detected by this method were in good agreement with the results obtained by EIA with E2–biotin.
相似文献
11.
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
12.
A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde
has been proposed for the first time. In the presence of 3.0×10−3 g ml−1 formaldehyde, netilmicin exhibits a sensitive cathodic peak at −1.30 V (vs. the saturated calomel electrode, SCE) in a medium
of Britton–Robinson buffer (pH 8.7) with a scan rate of 100 mV s−1 after a preconcentration period of 120 s at −1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin
concentration over the range 4.2×10−9–1.0×10−7 g ml−1. The achieved limits of detection and quantitation were 1.0×10−10 and 3.3×10−10 g ml−1 netilmicin, respectively. It was deduced from the experiments that the amine–aldehyde condensation product formed between
netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin
in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable
formulations and spiked human urine and serum samples.
相似文献
13.
Du D Huang X Cai J Zhang A Ding J Chen S 《Analytical and bioanalytical chemistry》2007,387(3):1059-1065
A simple method has been devised for immobilization of acetylcholinesterase (AChE)—covalent bonding to a multiwall carbon
nanotube (MWNT)–cross-linked chitosan composite (CMC)—and a sensitive amperometric sensor for rapid detection of acetylthiocholine
(ATCl) has been based on this. Fourier-transform infrared spectroscopy proved that the native structure of the immobilized
enzyme was preserved on this chemically clean and homogeneous composite film, because of the excellent biocompatibility and
non-toxicity of chitosan. Glutaraldehyde was used as cross-linker to covalently bond the AChE, and efficiently prevented leakage
of the enzyme from the film. Because of the inherent conductive properties of the MWNT, the immobilized AChE had greater affinity
for ATCl and excellent catalytic effect in the hydrolysis of ATCl, with a value of 132 μmol L−1, forming thiocholine, which was then oxidized to produce a detectable and rapid response. Under optimum conditions the amperometric
current increased linearly with the increasing concentration of ATCl in the range 2.0–400 μmol L−1, with a detection limit of 0.10 μmol L−1. Fabrication reproducibility of the sensor was good and the stability was acceptable. The sensor is a promising new tool
for characterization of enzyme inhibitors and for pesticide analysis.
Abstract 相似文献
14.
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
15.
Arvand M Pourhabib A Shemshadi R Giahi M 《Analytical and bioanalytical chemistry》2007,387(3):1033-1039
Liquid polymer membrane electrodes based on nickel and manganese phthalocyanines were examined for use as anion-selective
electrodes. The electrodes were prepared by incorporating the ionophores into plasticized poly(vinyl chloride) membranes,
which were directly coated onto the surfaces of graphite electrodes. The resulting electrodes demonstrate near-Nernstian responses
over a wide linear range of perchlorate anion (5 × 10−7 to 1 × 10−1 M). The electrodes have a fast response time, submicromolar detection limits (5 × 10−7 M perchlorate), and could be used over a wide pH range of 3.5–10. The influences of lipophilic cationic and anionic additives
on the response properties of the electrodes were investigated. The proposed sensors revealed high selectivity for perchlorate
over a number of common inorganic and organic anions. The highest selectivity was observed for the electrode based on manganese
phthalocyanine in the presence of the lipophilic anionic additive sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. Application
of the electrodes to determine perchlorate in tap water and human urine is also reported.
相似文献
16.
Nan Li Hui Tang Hongwei Gai Xiuling Dong Qi Wang Edward S. Yeung 《Analytical and bioanalytical chemistry》2009,394(7):1879-1885
Determination of protein surface excess is an important way of evaluating the properties of biomaterials and the characteristics
of biosensors. A single-molecule counting method is presented that uses a standard fluorescence microscope to measure coverage
of a liquid/solid interface by adsorbed proteins. The extremely low surface excess of lysozyme and bovine serum albumin (BSA),
in a bulk concentration range from 0.3 nmol L−1 (0.02 μg mL−1) to 3 nmol L−1 (0.2 μg mL−1), were measured by recording the counts of spatially isolated single molecules on either hydrophilic (glass) or hydrophobic
(polydimethylsiloxane, PDMS) surfaces at different pH. The differences observed in amounts of adsorbed proteins under different
experimental conditions can be qualitatively explained by the combined interactions of electrostatic and hydrophobic forces.
This, in turn, implies that single-molecule counting is an effective way of measuring surface coverage at a liquid/solid interface.
Figure Adsorption fraction of proteins on different surfaces changed with pH. 相似文献
17.
Feng QZ Zhao LX Yan W Ji F Wei YL Lin JM 《Analytical and bioanalytical chemistry》2008,391(3):1073-1079
Highly sensitive flow-injection chemiluminescence (CL) combined with molecularly imprinted solid-phase extraction (MISPE)
has been used for determination of 2,4-dichlorophenol (2,4-DCP) in water samples. The molecularly imprinted polymer (MIP)
for 2,4-DCP was prepared by non-covalent molecular imprinting methods, using 4-vinylpyridine (4-VP) and ethylene glycol dimethacrylate
(EGDMA) as the monomer and cross-linker, respectively. 2,4-DCP could be selectively adsorbed by the MIP and the adsorbed 2,4-DCP
was determined by its enhancing effect on the weak chemiluminescence reaction between potassium permanganate and luminol.
The enhanced CL intensity was linear in the range from 1 × 10−7 to 2 × 10−5g mL−1. The LOD (S/N = 3) was 1.8 × 10−8g mL−1, and the relative standard deviation (RSD) was 3.0% (n = 11) for 1.4 × 10−6g mL−1. The proposed method had been successfully applied to the determination of 2,4-DCP in river water.
Figure Effect of 4-VP content on the ultraviolet spectrum of 2,4-DCP in chloroform 相似文献
18.
Casas V Llompart M Garcia-Jares C Cela R Dagnac T 《Analytical and bioanalytical chemistry》2007,387(5):1841-1849
The aqueous instability of pyrethroids and other compounds usually found in commercial pesticide formulations has been demonstrated
in this work. Several types of sample treatment have been studied to avoid analyte losses during sample manipulation and storage.
Analysis was performed by SPME–GC–MS. Addition of sodium thiosulfate to tap water prevented pyrethroid degradation as a result
of oxidation by free chlorine. The amount added was optimized to minimize the effect of the salt on the analytical results.
Analysis of samples that had been stored at 4 °C for several days revealed loss of some of the pyrethroids in the first period
of storage. The effect of freezing the samples was studied and it was confirmed that samples could be stabilized for at least
one week by freezing. Finally, addition of a miscible organic solvent, for example acetone, led to improvement of the analytical
precision. The quality of the SPME–GC–MS method was studied. Linearity (R > 0.993), repeatability (RSD < 15%), and sensitivity
(detection limits between 0.9 and 35 pg mL−1) were good. When the procedure was applied to real samples including run off and waste water some of the target compounds
were identified and quantified.
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19.
Lee KC Cheuk MW Chan W Lee AW Zhao ZZ Jiang ZH Cai Z 《Analytical and bioanalytical chemistry》2006,386(7-8):2225-2232
A reversed-phase HPLC method has been developed for determination of twelve intact glucosinolates—glucoiberin, glucocheirolin,
progoitrin, sinigrin, epiprogoitrin, glucoraphenin, sinalbin, gluconapin, glucosibarin, glucotropaeolin, glucoerucin, and
gluconasturtiin—in ten traditional Chinese plants. The samples were extracted with methanol and the extracts were cleaned
on an activated Florisil column. A mobile phase gradient prepared from methanol and 30 mmol L−1 ammonium acetate at pH 5.0 enabled baseline separation of the glucosinolates. Glucosinolate detection was confirmed by quadrupole
time-of-flight tandem mass spectrometric analysis in negative-ionization mode. Detection limits ranged from 0.06 to 0.36 μg
g−1 when 5 g of dried plant was analyzed. Recoveries of the glucosinolates were better than 85% and precision (relative standard
derivation, n = 3) ranged from 5.3 to 14.6%. Analysis of the glucosinolates provided scientific evidence enabling differentiation of three
pairs of easily confused plants.
Figure Glucosinolates Analysis for the Differentiation of Easily-Confusing Herbs 相似文献
20.
Self-assembled monolayers (SAMS) of chemisorbed thioglycollate on a gold electrode surface have been used as a base interface
for the electrostatic adsorption of ferrocenium ion. Electrochemical impedance spectra (EIS) and cyclic voltammetry (CV) were
used to evaluate the electrochemical properties of the supramolecular film. The bare gold electrode failed to distinguish
the oxidation peaks of ascorbic acid (AA) and uric acid (UA) in phosphate buffer solution (PBS, pH 7.0), while the ferricinium–thioglycollate
modified electrode could separate them efficiently. In differiential pulse voltammetric measurements, the prepared gold electrode
could separate AA and UA signals, allowing the simultaneous determination of AA and UA. Under optimal conditions and within
the linear range of 1.0 × 10−6 to 5.0 × 10−4 M, the detection limits of AA and UA achieved were 2.0 × 10−7 and 1.0 × 10−7 M, respectively. The applicability of the prepared electrode was demonstrated by measuring AA and UA in human urine without
any pretreatment.
Figure Fabrication process for the modified electrode 相似文献