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1.
Zahradnícková H Husek P Simek P Hartvich P Marsálek B Holoubek I 《Analytical and bioanalytical chemistry》2007,388(8):1815-1822
A rapid and simple method was developed for the determination of free amino acids (AAs) released from cyanobacteria. The procedure
involves trapping of AAs from the centrifuged cyanobacterial culture fluid on a cation-exchange resin, their release together
with the resin by direct treatment with the reaction medium, followed by immediate derivatization with a corresponding chloroformate.
The extractive alkylation transfers the analytes into an organic phase, an aliquot of which is subjected to GC analysis. Identification
and quantification of AAs was performed by GC/MS and GC/FID, respectively, using propyl chloroformate (PCF) as the derivatization
reagent. For chiral analysis, the cyanobacteria extracts were treated with 2,2,3,3,3-pentafluoropropyl chloroformate (PFPCF)
to create more volatile analytes. Separation of the AA enantiomers was accomplished on a Chirasil-Val capillary column and
the D/L enantiomeric ratios were determined. AAs of cyanobacteria are considered to be important for the assessment of energy flow
in an aquatic food web, nutrition value of cyanobacteria in a food web and for cell–cell communication within cyanobacteria.
The highest levels of AAs were found in the summer period at the beginning of the season (July). In the September and October
samples, the amount of AAs was lower, the number of D-AAs decreased and the D/L ratio was higher than in the July sample. Based on the obtained results it can be assumed that young populations excrete
AAs in higher concentrations and a different composition compared to actively growing populations.
Figure PFPCF derivatization scheme 相似文献
2.
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
3.
Zakir Hossain SM Shinohara H Wang F Kitano H 《Analytical and bioanalytical chemistry》2007,389(6):1961-1966
There is an increasing interest in new strategies to detect neurotransmitters released from nerve cells in real time for brain
science, drug assessment, and so on. Previously we reported real-time monitoring of dopamine release from nerve model cells
by enzyme-catalyzed luminescence measurement with tyramine oxidase and peroxidase. In the present study, the system was modified
with glutamate oxidase instead of tyramine oxidase to detect L-glutamate sensitively (≈ 10 nM) and rapidly with high temporal resolution (<1 s). We applied this modified method successfully
to perform real-time monitoring of L-glutamate release from brain model cell (C6 glioma cell) using a luminescence plate reader upon stimulation with high concentration
of KCl (>10 mM) or 5-hydroxytryptamine (>1 μM). The measurement solution was not toxic and therefore the L-glutamate release from the cell was measured by the second stimulation after exchanging the measurement solution. We conclude
that the developed monitoring system is suitable for real-time detection of dynamic L-glutamate release from nerve cells in vitro and will be suitable for application in assessment of drugs acting on the nervous
system.
Figure Enzyme luminescence detection of L-glutamate released from cells 相似文献
4.
Yan Sun Laixin Luo Fang Wang Jianqiang Li Yongsong Cao 《Analytical and bioanalytical chemistry》2009,395(2):465-471
A novel method based on solid-phase extraction was studied for the extraction of amitrole (3-amino-1,2,4-triazole), and its
residue determination in apples has been developed. The samples were derivatized with 4-chloro-3,5-dinitrobenzotrifluoride
(CNBF). The derivatization conditions and the influence of elution composition on the separation were investigated. In pH
9.5 H3BO3–Na2B4O7 media, the reaction of amitrole with CNBF was complete at 60°C after 30 min. The separation of derivatized amitrole was achieved
at room temperature within 13 min by gradient elution mode with cetyltrimethylammonium bromide in mobile phase as ion-pair
reagent. The method correlation coefficient was 0.9996, in concentrations ranging from 1.66 to 415 mg L−1. The calculated recoveries of the proposed method were from 94.17% to 105.67%, and relative standard deviations were 1.57%
to 6.44% in the application to the quantitative determination of amitrole in apples. The detection limit of amitrole was 0.10 mg L−1 with a signal-to-noise ratio of 3.
Figure Residue determination of amitrole in apple by ion-pairing high-performance liquid chromatography 相似文献
5.
The fluorescence of fluoresceinisothiocyanate-labeled concanavalin A (FITC-Con A) was quenched by forming an FITC-Con A–glycogen
conjugate and dequenched upon addition of sugars to the conjugate solution due to disaggregation of the conjugate. However,
fluorescence quenching was barely observed upon formation of FITC-Con A–dextran conjugate. The sugar-induced fluorescence
response of the FITC-Con A–glycogen conjugate depended significantly on the type of sugar: methylated α-D-glucose and α-D-mannose both induced high and rapid responses, while the responses to D-mannose and D-glucose were moderate. In contrast, no response was observed in the presence of D-galactose due to a lack of affinity to Con A. Thus, it is apparent that D-glucose and other sugars can be detected via the fluorescence of the FITC-Con A–glycogen conjugate.
相似文献
6.
The membrane proteomes of a wild-type Corynebacterium glutamicum and an L-lysine-producing strain were quantitatively analyzed by two complementary proteomics techniques—anion exchange chromatography
AIEC/SDS-PAGE and 16BAC-PAGE/SDS-PAGE—and the results were compared. Although both techniques allow for the fast screening
of differences in protein abundance, AIEC/SDS-PAGE was superior to 16BAC-PAGE/SDS-PAGE with respect to protein separation,
it was more suitable for relative protein quantification, and allowed more differentially regulated proteins to be detected
(the succinate dehydrogenase complex, an ABC-type cobalamin/Fe3+ siderophore transport system, the maltose binding protein, and a subunit of the cytochrome bc-aa3 supercomplex were upregulated, while a periplasmic component of an ABC-type transporter and an iron-regulated ABC-type transporter
were downregulated in the producer). The results indicate the important role of tricarboxylic acid cycle enzymes as well as
the adaptation of transport processes in L-lysine-producing cells. Since the only genetic differences between the wild type and the L-lysine producer occur between four central metabolic enzymes in the cytoplasm, our study illustrates the complex effects
of metabolic engineering on cell physiology and the power of the new AIEC/SDS-PAGE proteomics approach to detect these effects.
相似文献
7.
A method is described for determination of residues of the insecticide Etofenprox in environmental samples. Anionic surfactant
micelle-mediated extraction (coacervation extraction) was evaluated for isolation of Etofenprox before HPLC. The optimum conditions
used for extraction included: 0.09 g sodium dodecanesulfonate (SDoS), 3.1 mL (3.3, for concentrations below 0.04 mg L−1) 12 mol L−1 HCl, 5 min vortex stirring, 5 min centrifugation at 4000 rpm, 2 h equilibration time. The limits of quantification (LOQ)
and detection (LOD) were 0.01 and 0.004 mg L−1, respectively, and recoveries obtained from five real samples ranged from 94.33±2.48 to 100.13±2.71%. The precision of the
method was good; relative standard deviations (RSD) were less than 7%.
相似文献
8.
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
9.
Fakhrullin RF Vinter VG Zamaleeva AI Matveeva MV Kourbanov RA Temesgen BK Ishmuchametova DG Abramova ZI Konovalova OA Salakhov MK 《Analytical and bioanalytical chemistry》2007,388(2):367-375
We report the development of a novel quartz crystal microbalance immunosensor with the simultaneous measurement of resonance
frequency and motional resistance for the detection of antibodies to double-stranded DNA (dsDNA). The immobilization of poly(l-lysine) and subsequent complexation with DNA resulted in formation of a sensitive dsDNA-containing nanofilm on the surface
of a gold electrode. Atomic force microscopy has been applied for the characterization of a poly(l-lysine)–DNA film. After the blocking with bovine serum albumin, the immunosensor in flow-injection mode was used to detect
the antibodies to dsDNA in purified protein solutions of antibodies to dsDNA and to single-stranded DNA, monoclonal human
immunoglobulin G, DNase I and in blood serum of patients with bronchial asthma and systemic lupus erythematosus. Experimental
results indicate high sensitivity and selectivity of the immunosensor.
In memoriam Prof. Victor G. Vinter 相似文献
10.
SPME in environmental analysis 总被引:1,自引:0,他引:1
Recent advances in the use of solid-phase microextraction (SPME) in environmental analysis, including fiber coatings, derivatization
techniques, and in-tube SPME, are reviewed in this article. Several calibration methods for SPME, including traditional calibration
methods, the equilibrium extraction method, the exhaustive extraction method, and several diffusion-based calibration methods,
are presented. Recent developed SPME devices for on-site sampling and several applications of SPME in environmental analysis
are also introduced.
相似文献
11.
Maria Chiara Pietrogrande Dimitri Bacco Mattia Mercuriali 《Analytical and bioanalytical chemistry》2010,396(2):877-885
This paper describes methods for the determination of low-molecular-weight (LMW) dicarboxylic acids in atmospheric aerosols
as important chemical tracers for source apportionment of aerosol organics and for studying atmospheric processes leading
to secondary organic aerosol formation. The two derivatization procedures most widely used in GC analysis of dicarboxylic
acids were compared: esterification using BF3/alcohol reagent and silylation using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA). The advantages and drawbacks of the two methods are investigated and compared
in terms of (1) precision and accuracy of the results and (2) sensitivity and detection limit of the procedure. The comparative
investigation was performed on standard solutions containing target C3–C9 dicarboxylic acids and on experimental particulate matter (PM) samples. Attention was focused on low-volume sampling devices
that collect small amounts of sample for organic speciation. The results show that, overall, both the techniques appear suitable
for the analysis of LMW dicarboxylic acids in atmospheric aerosols since they provide low detection limits (≤4 ng m−3) and satisfactory reproducibility (RSD% ≤ 15%). Between them, BSTFA should be the reagent of choice under the most limiting
conditions of PM filters collected by low-volume air samplers: It provides determination of all the target C3–C9 dicarboxylic acids with lower detection limits (≤2 ng m−3) and higher reproducibility (RSD% ≤ 10%)
相似文献
12.
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.
相似文献
13.
Miyamoto A Nakamura K Kishikawa N Ohba Y Nakashima K Kuroda N 《Analytical and bioanalytical chemistry》2007,388(8):1809-1814
A method that combines sequential injection analysis (SIA), flow injection analysis and chemiluminescence (CL) detection was
developed for the quasi-simultaneous determination of antioxidative activities against superoxide anion and nitric oxide (NO). The antioxidative activity was expressed as the decrease in luminol CL intensity caused by the quenching
of or NO by an antioxidant. The SIA system consisted of two syringe pumps, two selection valves, two holding coils, an HPLC
pump to deliver luminol solution, and a CL detector. Operation of the syringe pumps and multiport valves was controlled automatically
using a personal computer with appropriate software. A hypoxanthine (HX)-xanthine oxidase (XOD) system was used for the generation
of , and (±)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexenamide (NOR1) was employed as NO donor agent. The repeatability of the method was
evaluated with 35.2 μg ml−1
L-ascorbic acid, and the relative standard deviations (RSD) of the antioxidative activities were less than 3.8%. The quasi-simultaneous
determination of the antioxidative activities in one sample was completed within 2.0 min. The antioxidative activities of
some antioxidants and commercially available supplements containing certain antioxidants were successfully determined using
this system. The proposed system is rapid and reproducible, and thus may be useful for the screening of functional foods,
supplements and pharmaceutical formulations that exhibit antioxidative activity.
Figure The system that utilizes a combination of SIA and FIA with CL for the quasi-simultaneous determination of antioxidative activity
against a NO and b
. SP1, 2: syringe pump, HC1, 2: holding coil, MV1, 2: multi-port valve, P: pump, D: chemiluminescence detector, I: integrator, M1, 2: mixing tee, NOR1: (±)-(E)-4-methyl-2-[(E)- hydroxyimino]-5-nitro-6-methoxy-3-hexenamide, HX: hypoxanthine, XOD: xanthine oxidase. 相似文献
14.
The solubilities of amino acids have been measured in water and aqueous poly(ethylene glycol) (PEG) solutions as a function of temperature and PEG concentration. The free energies of transfer from water to aqueous PEG solutions forl-alanine,l-valine,l-isoleucine andl-leucine were positive, while those forl-phenylalanine andl-tryptophan were negative. The corresponding enthalpies of transfer were almost zero for all amino acids. The equilibrium constants of the binding of amino acids to PEG chain were estimated from the solubility data. Amino acids with larger hydrophobicity are bound more strongly to the PEG chain due to the hydrophobic interaction between the methylene groups of PEG and the side chain of amino acid. The equilibrium constants showed a correlation with the dynamic hydration number (n
DHN) which expresses the hydration properties of amino acids in aqueous solution. 相似文献
15.
A new method for the highly sensitive and selective determination of boron at nanograms per cubic decimeter levels has been
developed based on the derivatization reaction of boron using salicylaldehyde and 1-amino-8-naphtol-3,6-disulfonate with reversed-phase
partition high-performance liquid chromatography. A detection limit as low as 2.0 nmol/dm3 (22 ng/dm3) was achieved without any preconcentration. No significant interference was observed in the determination of 16 μmol/dm3 of boron with the addition of nine metal ions (AlIII, CuII, CoII, FeII, FeIII, NiII, MnII, VV, ZnII) at concentrations 100 times greater than that of boron without any masking procedure. The proposed method was successfully
applied to the determination of boron in river water, tap water, doubly distilled water, and highly purified water.
Figure Scheme of formation of boron-azomethine-H complex with salicylaldehyde and 1-amino-8-naphthol-3, 6-disulfonate 相似文献
16.
Pérez-Sirvent C Martínez-Sánchez MJ García-Lorenzo M López-García I Hernández-Córdoba M 《Analytical and bioanalytical chemistry》2007,388(2):495-498
Use of small membrane pumps, instead of peristaltic pumps, to introduce sample and reagent solutions into the spectrometer
has several advantages in atomic fluorescence spectrometric determination of mercury. This simple modification results in
a substantial saving in the time required for the measurements and so 90% of reagent solution volumes and 95% of sample solution
volumes are saved, with a consequent decrease in the volume of waste generated. The sampling frequency is almost tripled,
with no deterioration in sensitivity, which is similar to that obtained by use of peristaltic pumps. The relative standard
deviation for ten consecutive measurements of a 1 μg L−1 mercury solution was approximately 2%.
Figure Small membrane pumps for the atomic fluorescene spectro metric determination of mercury 相似文献
17.
A convenient new method for the simultaneous determination of losartan potassium and hydrochlorothiazide, with minimum sample
pretreatment, is described. The procedure, based on the multivariate analysis of spectral data in the 220−274 nm region by
the partial least squares algorithm, is linear in the concentration range 1.06−5.70 mg L−1 for hydrochlorothiazide and 4.0−22.2 mg L−1 for losartan. It is simple, rapid and robust, allowing accurate and precise results, with drug recovery rates of 99.3 and
100.4% and relative standard deviations of 1.7 and 1.0% obtained for hydrochlorothiazide and losartan, respectively. The method
was applied to the simultaneous determination of both analytes in tablets, and it provided good results which were in statistical
agreement with those provided by independent HPLC analyses of the samples. The method has also been successfully applied for
the construction of drug dissolution profiles of a commercial pharmaceutical preparation containing both analytes.
Figure A UV-PLS method for the simultaneous determination of losartan potassium and hydrochlorothiazide in pharmaceutical tablet
formulations has been developed and validated 相似文献
18.
Jitaru P Cozzi G Gambaro A Cescon P Barbante C 《Analytical and bioanalytical chemistry》2008,391(2):661-669
A method based on anion exchange (AE) and affinity (AF)-HPLC (AE-AF-HPLC) hyphenated to inductively coupled plasma-(quadrupole)
mass spectrometry (ICP-QMS) was developed for the speciation analysis of selenoprotein P (SelP), glutathione peroxidase (GPx)
and selenoalbumin (SeAlb) in human serum. AE-HPLC is proposed here for the on-line alleviation of Cl and Br spectral interferences
on 77Se (40Ar37Cl) and 82Se (81Br1H). Separation of GPx, SelP and SeAlb by AE-AF-HPLC was obtained within a total chromatographic runtime of <20 min. On-line
(post-column) isotope dilution (ON-ID) and on-line external calibration (ON-EC)-ICP-QMS were used for the quantification of
Se in GPx, SelP and SeAlb. ON-EC using a Se-L-cystine standard was shown to be a suitable approach for the routine simultaneous speciation analysis of serum GPx, SelP
and SeAlb. The method validation was carried out by direct ICP-sector field MS determination of Se in GPx, SelP and SeAlb
fractions collected after AE-AF-HPLC separation. In addition, the method accuracy for the determination of total protein-bound
Se was assessed by analyzing a human serum reference material (BCR-637) certified for total Se content.
Figure A methodology for the alleviation of Cl and Br interferences in the accurate simultaneous speciation analysis of glutathione
peroxidase, selenoprotein P and selenoalbumin in human serum by affinity HPLC coupled on-line with ICP-quadrupole MS is proposed.
This approach may be particularly useful for clinical laboratories that only have an ICP-quadrupole MS without a collision
cell, or that lack an expensive ICP-SFMS (high-resolution) instrument 相似文献
19.
Perdivara I Deterding L Moise A Tomer KB Przybylski M 《Analytical and bioanalytical chemistry》2008,391(1):325-336
Using the bottom-up approach and liquid chromatography (LC) in combination with mass spectrometry, the primary structure and
sequence microheterogeneity of a plaque-specific anti-β-amyloid (1–17) monoclonal antibody (clone 6E10) was characterized.
This study describes the extent of structural information directly attainable by a high-performance LC–tandem mass spectrometric
method in combination with both protein database searching and de novo sequence determination. Using trypsin and chymotrypsin
for enzymatic digestion, 95% sequence coverage of the light chain and 82% sequence coverage of the heavy chain of the 6E10
antibody were obtained. The primary structure determination of a large number of peptides from the antibody variable regions
was obtained through de novo interpretation of the data. In addition, N-terminal truncations of the heavy chain were identified
as well as low levels of pyroglutamic acid formation. Surprisingly, pronounced sequence microheterogeneities were determined
for the CDR 2 region of the light chain, indicating that changes at the protein level derived from somatic hypermutation of
the Ig VL genes in mature B-cells might contribute to unexpected structural diversity. Furthermore, the major glycoforms at the conserved
heavy chain N-glycosylation site, Asn-292, were determined to be core-fucosylated, biantennary, complex-type structures containing
zero to two galactose residues.
Figure Primary structure and sequence microheterogeneities of a β-amyloid plaque-specific monoclonal antibody were identified by
high-performance LC-tandem-mass spectrometry. Sequence heterogeneities of the light chain CDR2 reveal unexpected diversity
from VL-gene hypermutations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
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