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1.
Contamination by Brettanomyces is a frequent problem in many wineries that has a dramatic effect on wine aroma and hence its quality. The yeast Brettanomyces/Dekkera is involved in the formation of three important volatile ethylphenols—4-ethylphenol, 4-ethylguaiacol and 4-ethylcatechol—that
transmit an unpleasant aroma to wine that has often been described as ‘medicinal’, ‘stable’ or ‘leather’. This study proposes
an in situ derivatisation and headspace solid-phase microextraction– gas chromatography coupled to mass spectrometry method
to determine the three ethylphenols in red Brettanomyces-tainted wines. The most important variables involved in the derivatisation (acetic anhydride and base concentration) and
the extraction (extraction temperature and salt addition) processes were optimised by experimental design. The optimal conditions
using 4 mL of wine in 20-mL sealed vials were 35 μL of acetic anhydride per millilitre of wine, 1 mL of 5.5% potassium carbonate
solution and 0.9 g of sodium chloride and the extraction was performed with a divinylbenzene–carboxen–poly(dimethylsiloxane)
fibre at 70 °C for 70 min. Then, the performance characteristics were established using wine samples spiked with the ethylphenols.
For all compounds, the detection limits were below the odour threshold reported in the literature and they were between 2
and 17 μg L−1 for 4-ethylguaiacol and 4-ethylphenol, respectively. Intermediate precision (as relative standard deviation) was acceptable,
with values ranging from 0.3 to 12.1%. Finally, the method was applied in the analysis of aged Brettanomyces-tainted wines. 相似文献
2.
T. A. Matyushina E. I. Morosanova Yu. A. Zolotov 《Journal of Analytical Chemistry》2010,65(3):308-315
Conditions for the oxidative coupling of rutin and quercetin with 3-methylbenztiazolinon-2-hydrazone have been determined
under the conditions of microsequential flow analysis (‘lab-on-a-valve’). To provide the high sensitivity of the determination,
methods aimed at improving the overlapping of the zones in the flow have been utilized; these are stopped flow and injection
of a ‘spacer’ zone. Good results have been obtained using a new approach, the injection of a ‘spacer’ zone with a rate gradient.
A program of operations for the automatic spectrophotometric determination of rutin and quercetin has been composed. The analytical
range is (6–50) × 10−5 M for the determination of rutin and (5–50) × 10−5 M for the determination of quercetin, the productivity of analysis being 59 samples per hour. The procedure has been applied
to the analysis of plant extracts and pharmaceutical product Askorutin. 相似文献
3.
U. Friess R. Lehmann C. Weigert H. U. Haering W. Voelter E. Schleicher 《Chromatographia》2002,56(5-6):375-378
Summary A sensitive, convenient and reliable free-zone capillary electrophoretic method has been developed for the determination of
adenylate nucleotides in cell lysates without pre-analytical sample clean up. Simultaneous quantification of AMP, ADP, and
ATP can be performed with precision (within run) of 1.7–2.7% and reproducibility (day to day) of 1.3–3.5%. Detection limits
for AMP, ADP, and ATP were 10 μm each and the linear range was 10–200 μm for each. The sample volume required was less than 10 nL. The proposed method greatly simplifies and accelerates determination
of cellular ‘adenylate energy charge’, the most reliable measure of cellular energy status. 相似文献
4.
K. Suvardhan P. M. Krishna E. T. Puttaiah P. Chiranjeevi 《Journal of Analytical Chemistry》2007,62(11):1032-1039
Three simple, rapid, and sensitive spectrophotometric methods for the determination of traces and ultratraces of tellurium(IV)
were studied. These methods were based on either the oxidation of 4-bromophenylhydrazine (4-BPH) by tellurium in a basic medium
and coupling with N-(1-naphthyl)ethylenediamine dihydrochloride (NEDA) to give a purple-colored product, the oxidation of 3-methyl-2-benzothazoline
hydrazone hydrochloride (MBTH) by tellurium in a basic medium and coupling with chromotropic acid (CA) to yield a red-colored
species, or the oxidation of 2,3-dimethoxystrychnidin-10-one (2,3-DMSO) by tellurium in an acidic medium to yield an orange-colored
derivative. Beer’s law was obeyed in the range 1.0–25 μg/mL (purple-colored product), 0.7–20 μg/mL (red-colored species),
and 0.3–15 μg/mL (orange-colored derivative). The reaction conditions and other analytical parameters were investigated to
enhance the sensitivity of the proposed methods. The tolerance limit of various ions has been studied. The methods were applied
to the analysis of tellurium in water samples (waste, river, lake, and spring), plant materials, soil samples, and telluride
thin films. The results obtained were superior to those obtained using the reported method. The performances of the proposed
methods were evaluated in terms of ‘t’-test and variance ratio ‘f’-test, which indicate the advances of the proposed methods
over reported methods.
The text was submitted by the authors in English. 相似文献
5.
Simple and sensitive methods for the spectrophotometric determination of iron(III) in food, based on the formation of coloured
complexes of Fe(III) with Chromazurol S (CAS) in the presence of tetradecyltrimethylammonium bromide (TTA) or octadecyltrimethylammonium chloride (ODTA) and Triton X-100 (TX100), have been developed. Optimum pH and the concentrations of CAS, TTA, ODTA, and TX100 ensuring maximum
absorbance have been determined. For the Fe-CAS-TTA-TX100 system the molar absorptivity is 1.12 × 105 L/(mol cm) at 650 nm; for Fe-CAS-ODTA-TX100 it is 1.35 × 105 L/(mol cm) at 659.5 nm. Beer’s law was obeyed for iron concentration in the range 0.08–0.56 μg/mL for the complex Fe-CAS-TTA-TX100
and 0.08–0.64 μg/mL for Fe-CAS-ODTA-TX100. The influence of several interfering ions has been discussed. The stoichiometry
of the complexes was established by applying Job’s method. The more sensitive method, based on the Fe-CAS-ODTA-TX100 system,
has been applied to the determination of iron in cereals. To evaluate the accuracy of the elaborated method, the determined
content of Fe was compared to the declared value as well as to the result obtained by the reference ICP-OES method. 相似文献
6.
I. V. Semak N. A. Alekseev E. O. Korik A. M. Drobyshevskii M. V. Antonova 《Journal of Analytical Chemistry》2011,66(2):195-200
A procedure has been developed for the determination of a macrolide antibiotic roxythromycin (RX) in blood serum using HPLC
with mass spectrometric detection using clarithromycin (CL) as the internal standard. RX and CL have been extracted from the
samples by solid-phase extraction in a cartridge filled with a polar adsorbent, cyanopropylsilyl silica gel. The absolute
recoveries of RX and CL are 89.6 and 92.5%, respectively. Chromatographic separation has been performed on a Nucleodur C18 Isis column with the mobile phase composed as follows: water-methanol-acetonitrile-formic aid (499: 250: 250: 1 by volume).
Registration has been performed in the mode of selected ion monitoring with m/z 837.7 (RX) and m/z 748.7 (CL). The analytical range for RX is 0.097–14.81 μg/mL, the quantification limit is 0.097 μg/mL, the detection limit
is 0.03 μg/mL, and the intraday and interday relative standard deviation are 2–6 and 4–8% respectively. The procedure has
been applied to the pharmacokinetic studies of the Rulid pharmaceutical preparation. 相似文献
7.
Bi2Al4O9 ceramics are difficult to sinter to greater than 80% theoretical density due to peritectic decomposition at 1,070 °C. A novel processing method is discussed where a high-bismuth oxide-based liquid is used as a sintering aid. After sintering, the high bismuth oxide phase is removed by leaching with 40% acetic acid. The resulting samples are phase pure and ∼91% dense. The grain size varies in a wide range with the average grain size of ∼1 μm. The electrical properties of these ceramics were measured as functions of temperature (550–850 °C) and oxygen partial pressure (6×10−6–1 atm). The total conductivity was separated into electronic and ionic contributions. The low ionic conductivity indicates that the material is not an ‘intrinsically defective fast ion conductor’. The ionic conductivity is due almost exclusively to compensating oxygen vacancies related to impurities. With increasing temperature and decreasing oxygen partial pressure, the electronic conduction dominates over the ionic conduction. 相似文献
8.
Summary The stability of emulsion of Toluene in water stabilized by partially flocculated ferric hydroxide sol has been studied. The
size of the emulsion droplets as determined by size frequency analysis is found to be of 1.1 μ radius. The flocculation studies were carried out haemocytometrically at different amount of electrolytes and at different
pH values. The electrokinetic potential ‘ζ’ was determined micro-electrophoretically at different amounts of electrolytes and
also at different pH's. In the case of tri and tetra valent anions the charge reversal was observed. In the light of the D.V.O. theory the interaction
energy profiles were drawn and 2–6 kT deep secondary minima obtained showing thereby the occurrence of reversible flocculation. Degree of aggregation has been
calculated theoretically at different values of ‘A’ and the value of A was found to be 1.0×10−12 erg to fit the value of degree of aggregation obtained haemocytometrically. The charge densities and binding parameters have
also been calculated. 相似文献
9.
Summary An isocratic, reversed-phase liquid chromatographic (LC) method has been developed for the simultaneous determination of azelaic
and benzoic acids in pharmaceutical creams. The compounds were separated on a C18 column (4 μm particles); the mobile phase was methanolwater, 40∶60, containing 10mm ammonium acetate and with the pH adjusted to 5.0. Detection was performed at 220 nm. The method was validated for accuracy,
linearity, precision, and selectivity. Recoveries at levels corresponding to 80% to 120% of the declared content of the creams
ranged from 99.5 to 101.8% and from 100.4 to 102.1% for azelaic and benzoic acids, respectively. The calibration graphs were
linear in the ranges 20–1400 μg mL−1 for azelaic acid (correlation coefficient,r
1>0.99999), and 0.1–7.0 μg mL−1 for benzoic acid (r>0.99998). 相似文献
10.
J. Weaver S. R. F. Biegalski A. Brand E. J. Artnak 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):687-692
A Nuclear Explosion Monitoring Inertial Impactor (NEMII) system was developed to physically separate naturally occurring radionuclides
from those produced in nuclear weapons explosions. Studies show that aerosols containing natural activity have an aerodynamic
diameter in the range of 0.1–1.0 μm. It has been established that atmospheric nuclear explosions produce radioactive aerosols
with aerodynamic diameters <0.1 μm and surface explosion produce a bimodal distribution of radioactive particles with aerodynamic
diameters both >1.0 μm and <0.1 μm. A high volume (66 m3 h−1) impactor was designed to separate the particles into three size distributions: aerosols with aerodynamic diameters >1.0 μm,
between 0.1 and 1.0 μm, and smaller than 0.1 μm. Calculations based on previous work for high-volume impactors were completed
to obtain the impactor geometry that yields the desired cutoff values. The components of the aerosol impactor were manufactured
or obtained and then assembled. In addition, a submicrometer aerosol generation system was assembled to benchmark the NEMII
system against a commercial Micro-Orifice Uniform-Deposit Impactor (MOUDI). The MOUDI was also used to verify the naturally
occurring radioactivity distribution using 212Pb gamma spectra. 相似文献
11.
A. Phonchai B. Janchawee S. Prutipanlai S. Thainchaiwattana 《Journal of Analytical Chemistry》2010,65(9):951-959
A methodology for the determination of 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and methamphetamine (MA) in seized tablets using gas chromatography with a flame ionization detector (GC-FID) is described. The chromatographic conditions, i.e. gas flow rates and temperatures for the column, injector and detector
were optimized. The optimum chromatographic conditions were as follows: a CP-SIL 24 CB WCOT fused silica capillary column
(30 m × 0.32 mm I.D., 0.25 μm film thickness), N2 carrier gas flowing at 2.6 mL/min, injector temperature at 290°C and detector temperature at 300°C. The oven temperature
was ramped from 80°C at a rate of 20°C/min to final temperature of 270°C (1 min). All analytes were well separated within
7 min with an analysis time of 10.5 min. Calibration curves were linear over the concentration ranges of 3.125–200 μg/mL for
MDMA and 6.25–200 μg/mL for MDA and MA (r > 0.990). The intra- and inter-day precisions for determining all analytes were 2.32–10.38% RSD and 1.15–9.77% RSD, respectively.
The intra- and inter-day accuracies ranged from −19.79 to +17.51% DEV and −6.84 to +5.2% DEV, respectively. The lower limits
of quantification (LLOQs) were 3.125 μg/mL for MDMA and 6.25 μg/mL for MDA and MA. All analytes were stable at room temperature during 24 h but significant
loss occurred after 2-month storage at −20°C. The method was shown to be useful for determining the purity of MDMA in seized
tablets. 相似文献
12.
Joseph E. Earley Sr. 《Foundations of Chemistry》2006,8(3):271-283
During a long and distinguished career, Belgian physical chemist Ilya Prigogine (1917–2003) pursued a coherent research program in thermodynamics, statistical mechanics, and related scientific areas. The main goal of this effort was establishing the origin of thermodynamic irreversibility (the ‘‘arrow of time’’) as local (residing in the details of the interaction of interest), rather than as global (being solely a consequence of properties of the initial singularity – the ‘‘Big Bang’’). In many publications for general audiences, he stated the opinion that this scientific research had great philosophical importance. Prigogine and his colleagues considered that the most recent stages of this research program have been successful, so that the local origins of the arrow of time are now established. There is no scientific consensus as to whether or not this claim is valid. Similarly, there is no consensus on whether the competing global (initial singularity) explanation has been proven. 相似文献
13.
Two simple, rapid and reproducible spectrophotometric methods have been described for the assay of olmesartan (OLM) in pharmaceutical formulation. The methods are based on the formation of ion associates in the reactions between the studied
drug substance and ion-pair agents [bromocresol green (BCG) and bromophenol blue (BPB)]. By the extraction with dichloromethane and chloroform, yellow-colored ion associates were formed in acidic medium and
absorbances were measured at 409 (BCG) and 412 nm (BPB). Optimizations of the reaction conditions were performed. Beer’s law
was obeyed within the concentration range from 1–40 μg/mL and 10–120 μg/mL, respectively, for BCG and BPB. The molar absorptivity,
detection and quantification limits were also determined. The developed methods were applied successfully to the determination
of this drug in tablets. 相似文献
14.
An optical video microscopic technique was used to study hetero-aggregation and selective aggregation phenomena among n-hexadecane oil drops (40–110 μm in diameter) and two types of polystyrene latex particles (6.76 and 30.2 μm, in diameter),
suspended inside an aqueous medium with pH varying between 1.1 and 12.9. A single drop was produced in situ using a micropipette
inside the aqueous phase-filled glass microcapillary (100–160 μm i.d.) containing the particles. Interactions between the
drop and the solid particles and among the solid particles was achieved by movement of the aqueous medium in and out of a
second micropipette. Drop–particle interactions were distinctly different from particle–particle interactions. It was observed
that the latex particles aggregated irreversibly with the oil drop in all cases except two, viz. for 6.76 μm particles at
around neutral pH whereas the irreversibility of aggregation in particle–particle interactions was only seen at the ends of
the pH spectrum. At around neutral pH, the flocs or clusters of small particles were very weak. Visual observations at each
pH are explained on the basis of the classical DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. Partial wetting of particles
surfaces by oil appears to be a key factor in the irreversibility of drop– particle hetero-aggregation. Results indicate that
the display of reversible, irreversible or weak aggregation depends on the location and depth of the secondary minimum and
that the long-range, attractive, London–van der Waals force is responsible for the initial formation of an aggregate.
Received: 4 July 1996 Accepted: 5 December 1996 相似文献
15.
Summary An oxalic acid-α-hydroxyisobutyric acid eluent has been used for the separation and determination of rare-earth elements by
high-performance ion-exchange chromatography. Fifteen rare-earth elements were separated within less than 25 min on a 150×4.6
mm i.d. column packed with 5-μm sulfonic acid-bonded silica particles by elution with a combined gradient of 0.60–9.0 mM oxalic
acid and 19.0–5.0 mM α-hydroxyisobutyric acid at pH 4.6. Detection and quantitation of the separated rare-earth elements was
accomplished by visible-absorbance measurements at 600 nm after postcolumn reaction with arsenazo I. The gradient of the two
complexing agents was optimized to enable the separation of yttrium(III) without interference from other elements, especially
dysprosium(III) and terbium(III). Mass detection limits of the elements were in the range of 2–4 ng. Finally, the chromatographic
system was applied to the quantitative analysis of rare-earth elements in monazite and xenotime. 相似文献
16.
Karadjova IB Lampugnani L D'Ulivo A Onor M Tsalev DL 《Analytical and bioanalytical chemistry》2007,388(4):801-807
A rapid, accurate, and precise method is described for the determination of Pb in wine using continuous-flow hydride generation
atomic fluorescence spectrometry (CF-HGAFS). Sample pretreatment consists of ten-fold dilution of wine followed by direct
plumbane generation in the presence of 0.1 mol L−1 HCl and 1% m/v K3[Fe(CN)6] with 1% m/v NaBH4 as reducing agent. An aqueous standard calibration curve is recommended for Pb quantification in wine sample. The method
provides a limit of detection and a limit of quantification of 0.3 μg L−1 and 1 μg L−1, respectively. The relative standard deviation varies between 2–6% (within-run) and 4–11% (between-run) at 3–30 μg L−1 Pb levels in wine. Good agreement has been demonstrated between results obtained by CF-HGAFS and direct electrothermal atomic
absorption spectrometry in analyses of red and white wines within the concentration range of 9.2–25.8 μg L−1 Pb. 相似文献
17.
Magdalena Staszewska Monika Dzieciuch Joanna Lewandowska Mariusz Kepczynski Szczepan Zapotoczny Marcin Oszajca Anna Łatkiewicz Maria Nowakowska 《Journal of Sol-Gel Science and Technology》2011,59(2):276-282
In this article, we report on the formation of well-defined highly emissive silica-covered porphyrin microstructures in base-catalyzed
sol–gel processes. The microstructures were obtained by self-assembly of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (mTHPP)
at room temperature. Tetraethoxysilane (TEOS) was used as a silica precursor. The hybrid mTHPP- silica particles were characterized
by means of reflectance UV–Vis and microscopy techniques including atomic force microscopy, scanning electron microscopy (SEM)
and confocal fluorescence microscopy (CM). The SEM and TEM observations revealed that depending on the porphyrin concentration
used in the synthesis, the shape of the hybrid mTHPP-silica particles has changed from ribbon-like (c
mTHPP = 2.09 mM) to rhombus-like structures (c
mTHPP = 4.35 mM). The ribbons were straight-edged, uniform in width (1.2–1.8 μm) and height (350–400 nm), and variable in length
(40–100 μm). The rhombs were 1–3.7 μm in height, 7–25 μm in length, and 3.5–15 μm in width, and the ratio of length to width
was uniform and equal to ca. 1.8–2. UV–Vis absorption spectra indicated that the J-aggregates and H-aggregates formed in the
systems with lower and higher porphyrin content, respectively. Formation of different type of porphyrin aggregates in both
systems resulted in different emission spectra, as it was shown with CM. 相似文献
18.
Neng Zhou Yi-Zeng Liang Ben-Mei Chen Ping Wang Xian Chen Feng-Ping Liu 《Chromatographia》2007,66(7-8):481-486
A rapid, simple and specific liquid chromatography-electrospray ionization mass spectrometry method has been developed and
validated for the determination of hydroxyzine hydrochloride in human plasma. Samples were separated using a Thermo Hypersil-HyPURITYC18
reversed-phase column (150 mm × 2.1 mm i.d., 5 μm). The mobile phase consisted of 50 mM ammonium acetate (pH 4.0)–methanol–acetonitrile
(45:36:19, v/v). Hydroxyzine and its internal standard were measured by electrospray ion source in positive selective ion monitoring mode.
The method was validated with a linear range of 1.56–200.0 ng mL−1 and the lowest limit of quantification was 1.56 ng mL−1 for hydroxyzine hydrochloride (r
2= 0.9991). The extraction efficiencies were about 70% and recoveries of the method were in the range of 93.5–104.4%. The intra-day
relative standard deviation (RSD) was less than 8.0% and inter-day RSD was within 7.4%. QC samples were stable when kept at
ambient temperature for 12 h at −20 °C for 30 days and after four freeze–thaw cycles. The method has been successfully applied
to the evaluation of pharmacokinetics and bioequivalence of two hydroxyzine hydrochloride formulations in 12 healthy Chinese
volunteers after an oral dose of 25 mg. 相似文献
19.
M. S. Chernov’yants N. V. Aleshina I. V. Burykin 《Journal of Analytical Chemistry》2011,66(3):280-284
A procedure was developed for the determination of the following thioamides based on thiazole, 1,3,4-thiadiazole, 1,2,4-triazole,
and tetrazole: 2-mercaptothiazole (I), 2-mercapto-1,3,4-thiadiazole (II), 2-mercapto-5-methyl-1,3,4-thiadiazole (III), 3-mercapto-1,2,4-triazole (IV), 3-mercapto-4-methyl-1,2,4-triazole (V), and 5-mercapto-1-methyltetrazole (VI). The determination was performed by reversed-phase HPLC on a column (150 × 4 mm) packed with Diaspher-110-C18 (5 μm) using
elution with an acetonitrile-acetate buffer solution (pH 4.70) mixture (5: 95). Detection was performed at the light absorption
maximums of compounds I (320 nm), II (305 nm), III (310 nm), IV (260 nm), V (254 nm), and VI (245 nm). The calibration graphs were linear over the following concentration ranges (μg/mL): 0.47–11.72 (I), 0.47–11.82 (II), 0.53–13.22 (III), 0.40–10.11 (IV), 0.46–11.52 (V), and 0.46–11.62 (VI). The limits of detection were 0.45, 0.43, 0.50, 0.37, 0.41, and 0.42 μg/mL for compounds I–VI, respectively. Conditions for the separation of a mixture of compounds I and III–V and for the quantitative determination of compounds I–VI by capillary zone electrophoresis (CZE) were optimized. CZE was performed on a quartz capillary of size 60 cm (effective length of 50 cm) × 75 μm at a voltage of
20 kV with a borate buffer solution (pH 9.18). The procedure allowed us to evaluate the concentrations of substances in the
ranges of 1.17–93.75 (I), 1.18–94.54 (II), 1.32–105.76 (III), 1.01–101.13 (IV) 1.15–115.16 (V), and 1.16–116.15 (VI) μg/mL with the detection limits of 1.10, 1.11, 1.20, 0.96, 1.01, and 1.02 μg/mL for compounds I–VI, respectively. 相似文献
20.
A. V. Bulatov A. L. Moskvin L. N. Moskvin P. A. Lepilova 《Journal of Analytical Chemistry》2011,66(6):641-645
The method of cyclic injection analysis in the ‘lab-in reaction-cell’ mode has been proposed for the miniaturization of flow
analysis; the hydraulic scheme of this mode assumes the formation of the analytical forms of the analytes and their detection
directly in the reaction cell of the cyclic injection analyzer through the combination of the latter with the measurement
cuvette of a fiber optic spectrophotometer. The possibilities of the proposed solution are illustrated by the example of the
determination of ‘active chlorine’ in aqueous media. A procedure has been developed for the automated photometric determination
of ‘active chlorine’ in the range from 0.2 to 1.3 mg/L in aqueous media in a 125 μL sample, the duration of one analysis being
2.5 min. 相似文献