共查询到20条相似文献,搜索用时 31 毫秒
1.
Jakubowska N Polkowska Z Kujawski W Konieczka P Namieśnik J 《Analytical and bioanalytical chemistry》2007,388(3):691-698
The analysis of volatile organic compounds in samples of biological fluids characterized by complex matrices is highly challenging.
This paper presents a comparison of the results obtained in this field using three solvent-free techniques: thin-layer headspace
with autogenous generation of liquid sorbent (TLHS) and membrane separation of the trace substances (pervaporation, PV), both
of which are coupled to direct aqueous injection gas chromatography–electron capture detection (TLHS–DAI–GC–ECD and PV–DAI–GC–ECD),
as well as conventional static headspace analysis followed by GC analysis with ECD detection (HS–GC–ECD). Basic validation
parameters of the HS–GC–ECD, TLHS–DAI–GC–ECD and PV–DAI–GC–ECD procedures were calculated for water and urine samples. The
calibration curves for all procedures were linear within the concentration range examined. The intermediate precisions of
the procedures were good and reached about 10% (for all analytes) for HS–GC–ECD and TLHS–DAI–GC–ECD. The poorest results were
obtained for PV–DAI–GC–ECD: about 20% for all analytes. The lowest method detection limits were obtained for the TLHS–DAI–GC–ECD
procedure: below 0.0022 μg/L for all analytes. The enrichment factors did not differ significantly between water and urine
samples, indicating little or no matrix effect in all procedures. 相似文献
2.
A simple and direct spectrophotometric method is developed for the determination of some cephalosporin group antibiotic drugs
such as Loracarbef (Lora), Ceftazidime (Ceft), and Cefaclor (Cefa) in bulk and pharmaceutical formulations. The optimum conditions
for the analysis of aqueous solutions of drugs are studied. Under the optimum conditions, the three drugs could be assayed
in the concentration range 2–9 × 10−5, 2–6 × 10−5, and 3–9 × 10−5 M for Lora, Ceft and Cefa, respectively. Detection and quantification limits are calculated. The obtained results showed
good recoveries of 100.4, 107.4, and 100.7% for Lora, Ceft, and Cefa, respectively. The results obtained are compared favorably
with those given by literature methods. 相似文献
3.
Ayşegül Gölcü 《Journal of Analytical Chemistry》2008,63(6):538-543
A sensitive, extraction, derivatization, evaporation and complexation-free, direct spectrophotometric method is developed
for the determination of some anthypertensive drugs such as acebutolol hydrochloride (ACH), atenolol (ATE), and propranolol hydrochloride (PRH) in bulk and pharmaceutical formulations. The optimum conditions for the analysis of aqua solutions of drugs are established.
The method permits the determination of ACH, ATE, and PRH over a concentration range of 37.3–111.9, 53.3–213.1 and 14.8–51.8
μg/mL, respectively. Detection and quantification limits are calculated. The obtained results showed good recoveries of 99.60,
99.20 and 99.80% with relative standard deviations of 0.82, 0.79 and 1.70% for ACH, ATE, and PRH, respectively. The repeatability
and reproducibility of the drugs for aqua media are determined. Precision and accuracy of the developed methods are used for
the recovery studies. The proposed method is applicable for the assay of the three drugs under investigation in dosage forms
and the results are in good agreement with those obtained by the literature method.
The text was submitted by the author in English. 相似文献
4.
A direct chemiluminescence method for the determination of nucleic acids has been developed based on the enhancement of
nucleic acids on the chemiluminescence light emission of the reaction between Ru(phen)3
2+(phen = 1,10-phenanthroline) and Ce(IV). Under the optimum conditions, the calibration graphs are linear in the range of 5.0
× 10–8–5.0 × 10–5 g/mL for calf thymus DNA, 8.0 × 10–8–5.0 × 10–5 g/mL for fish sperm DNA and 1.0 × 10–7–3.0 × 10–5 g/mL for yeast RNA, respectively. The limits of detection are 1.0 × 10–8 g/mL for calf thymus DNA, 3.1 × 10–8 g/mL for fish sperm DNA and 5.2 × 10–8 g/mL for yeast RNA, respectively. The final procedure allows the successful determination of calf thymus DNA, fish sperm
DNA and yeast RNA in six synthetic samples. This method is simple, rapid and specific.
Received: 22 January 1999 / Revised: 29 April 1999 / Accepted: 3 May 1999 相似文献
5.
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
6.
Calibration of analytical methods using laser ablation for sample introduction is often problematic. The availability of matrix-adapted
standard materials is a crucial factor in the analysis of biological samples in particular. In this work a method for preparation
of thin-film references for LA–ICP–MS is presented which is inexpensive, relatively simple and generally practicable. Aqueous
solutions of agarose spiked with defined amounts of the analytes were cast on a carrier and then dried. When the thin-film
references were characterized the average thickness of the films was 0.03 mm in the centre of the film and the relative standard
deviation was 8%. Nebulization ICP–MS analysis after acid digestion of the agarose film was used to investigate the effectiveness
of the spiking procedure. Recovery of the spiked elements was frequently in the range 90–110% (for rare earth elements 97–102%).
Laser ablation ICP–MS analysis was used to investigate the distribution of the spiked elements in the film. When the laser
was scanned across the gel the measured intensities were not constant, but had a peak-shaped profile with a flat top. Use
of this flat-top region for analytical purposes, after its characterization by laser ablation ICP–MS, is proposed. Analysis
of cell cultures was carried out by direct laser ablation-ICP–MS with the calibration method described. The results were in
accordance with values previously achieved by nebulization ICP–MS. 相似文献
7.
Jerzy Jurczyk Rafał Sitko Beata Zawisza Franciszek Buhl Ewa Malicka 《Mikrochimica acta》1999,132(1):41-47
A simple and quick method of durable samples preparation by the thin layer method through direct digesting of the analysed
material on the substrate has been presented. Four- and three-component mono- and polycrystals have been analysed. Standards
have been used in calibration containing: Cr, Co, Ni, Cu, Zn, Ga, Se, Sb, Yb. To improve the correlation between the concentration
and the fluorescent radiation models of mathematical corrections have additionally been used: multiple linear regression,
Lucas-Tooth-Pyne model (L. T. P.) and de Jongh model (d. J.).
Statistical parameters: detection limits for 0.5 mg samples: Cr–0.041%, Co–0.034%, Ni–0.042%, Cu–0.053%, Zn–0.054%, Ga–0.057%,
Se–0.057%, Sb–0.113%, Yb–0.077%. Correlation coefficients: simple regression 0.9946–0.9997, multiple regression 0.9974–1.0000,
L. T. P. 0.9993–1.0000, d. J. 0.9995–1.0000.
Received August, 1, 1998. Revision March 25, 1999. 相似文献
8.
Shen J Zhang Z Yao Y Shi W Liu Y Zhang S 《Analytical and bioanalytical chemistry》2007,387(4):1561-1564
This study describes the development and validation of a time-resolved fluoroimmunoassay (TR-FIA) for screening ractopamine
(RAC) in swine tissue. The method is based on the direct competitive-type immunoassay using europium-labeled anti-RAC monoclonal
antibody as a tracer and RAC–ovalbumin as a solid-phase antigen. When RAC was spiked at levels of 1–10 μg kg−1, recoveries ranged from 88.2 to 118.5% for swine liver and muscle with coefficients of variation from 7.1 to 20.5%. The detection
limit was 0.1 μg kg−1. The proposed TR-FIA method was applied to the determination of RAC in an actual residue study and the applicability was
confirmed by liquid chromatography–tandem mass spectrometry. 相似文献
9.
Nai-Xing Wang Lei Wang Wei Jiang Yue-Zhen Ren Zhi-Kun Si Xun-Xing Qiu Gao-Ying Du Ping Qi 《Analytical and bioanalytical chemistry》1998,361(8):821-824
Norfloxacin (NFX) is proposed as reagent for the derivative spectrophotometric determination of neodymium, holmium and erbium
in mixed rare earths. The absorption spectra of 4f electron transitions of the systems of neodymium, holmium and erbium complexes
with norfloxacin in presence of cetylpyridinium chloride were studied by normal and derivative spectra. The absorption bands
found normally at 575 nm for neodymium, 450 nm for holmium and 523 nm for erbium were enhanced markedly. Using the second
derivative spectrum, Beer’s Law is obeyed from 5.0 × 10–5∼ 2.5 × 10–4 mol dm–3 for neodymium, holmium and erbium. The relative standard deviations are 1.0, 1.4 and 1.1% for 6.9 × 10–5 mol dm–3 of neodymium, 6.1 × 10–5 mol dm–3 of holmium and 6.0 × 10–5 mol dm–3 of erbium, respectively. A method for the direct determination of neodymium, holmium and erbium in mixtures of rare earth
elements with good accuracy and selectivity, is described.
Received: 18 December 1997 / Revised: 23 February 1998 / Accepted: 26 February 1998 相似文献
10.
Nai-Xing Wang Lei Wang Wei Jiang Yue-Zhen Ren Zhi-Kun Si Xun-Xing Qiu Gao-Ying Du Ping Qi 《Fresenius' Journal of Analytical Chemistry》1998,361(8):821-824
Norfloxacin (NFX) is proposed as reagent for the derivative spectrophotometric determination of neodymium, holmium and erbium
in mixed rare earths. The absorption spectra of 4f electron transitions of the systems of neodymium, holmium and erbium complexes
with norfloxacin in presence of cetylpyridinium chloride were studied by normal and derivative spectra. The absorption bands
found normally at 575 nm for neodymium, 450 nm for holmium and 523 nm for erbium were enhanced markedly. Using the second
derivative spectrum, Beer’s Law is obeyed from 5.0 × 10–5∼ 2.5 × 10–4 mol dm–3 for neodymium, holmium and erbium. The relative standard deviations are 1.0, 1.4 and 1.1% for 6.9 × 10–5 mol dm–3 of neodymium, 6.1 × 10–5 mol dm–3 of holmium and 6.0 × 10–5 mol dm–3 of erbium, respectively. A method for the direct determination of neodymium, holmium and erbium in mixtures of rare earth
elements with good accuracy and selectivity, is described.
Received: 18 December 1997 / Revised: 23 February 1998 / Accepted: 26 February 1998 相似文献
11.
Synthesis,characterization and catalytic activities of bimetallic modified MCM-41 for epoxidation of styrene 总被引:1,自引:0,他引:1
Yuran Wang Yajie Guo Guangjian Wang Yiwu Liu Fei Wang 《Journal of Sol-Gel Science and Technology》2011,57(2):185-192
Mesoporous molecular sieves MCM-41 modified by bimetal (Zr and Ti) ions with ordered hexagonal arrangement were prepared by
direct synthesis under microwave–hydrothermal conditions at 403 K. FT-IR, N2 adsorption–desorption, scanning electron microscope, high-resolution transmission electron microscope, element mapping, X-ray
photoelectron spectroscopy, diffuse Reflectance UV–Visible Spectra etc. were used to characterize as-prepared materials. The
results showed that Zr and Ti were introduced into MCM-41 and bonds of Zr–O–Si and Ti–O–Si were formed in framework of the
MCM-41. Moreover, their structures with ordered arrangement were still retained. The microwave–hydrothermal method might shorten
the synthesis time from days to hours and the as-prepared catalyst had a high catalytic activity and selectivity for the liquid-phase
epoxidation of styrene. 相似文献
12.
Ramón Batlle Anders Colmsjö Ulrika Nilsson 《Analytical and bioanalytical chemistry》2001,369(6):524-529
An SPME method was developed for sampling gaseous 2,4-toluene diisocyanate (2,4-TDI) involving derivatisation of the isocyanate
by reacting with dibutylamine (DBA). The TDI-DBA derivative thus formed was determined by LC–MS–MS utilising atmospheric pressure
chemical ionisation (APCI). As a first step, DBA was loaded onto a poly(dimethylsiloxane)/divinylbenzene (PDMS–DVB) fibre
coating by direct vapour-phase extraction of a highly concentrated diethyl ether solution of DBA. The DBA-loaded fibre was
then exposed to an artificially generated atmosphere of gaseous 2,4-TDI. The linearity of the method ranged from 52.8 to 3100
μg m–3 (6.8 to 400 ppbv) with a sampling time of 60 min. The proposed method has been applied to 2,4-TDI determination in an artificially
generated dynamic standard atmosphere, yielding an approximate method detection limit (MDL) of 2 μg m–3 (0.25 ppbv). This concentration is one twentieth of the Occupational Safety and Health Administration (OSHA) 8-hour time-weighted
average (TWA) exposure limit. The sampler with the PDMS–DVB-DBA coating was found to be stable and retains the required amount
of DBA for at least 10 days, an important feature for sampling systems with potential in-situ applications.
Received: 2 October 2000 / Revised: 4 December 2000 / Accepted: 6 December 2000 相似文献
13.
A. Segura Carretero C. Cruces Blanco R. Estrada Fernández A. Fernández Gutiérrez 《Fresenius' Journal of Analytical Chemistry》1998,360(5):605-608
A method for the determination of the fungicide thiabendazole (TBZ) by micellar-stabilized room-temperature phosphorescence
is described. It does not require any separation step and allows the direct determination of the fungicide in canned pineapple
samples. The effect of various experimental conditions is discussed in detail. The analytical curve of thiabendazole gives
a linear dynamic range of 23.8–500.0 ng mL–1 and a detection limit of 23.8 ng mL–1. Recoveries of 103.9 and 89.2% for syrup and canned pineapple pulp, respectively, were obtained for 250 ng mL–1 thiabendazole.
Received: 30 April 1997 / Revised: 18 July 1997 / Accepted: 23 July 1997 相似文献
14.
V. Terzieva L. Jordanova S. Arpadjan 《Fresenius' Journal of Analytical Chemistry》1998,360(6):734-736
A fast, sensitive and reliable method for the indirect atomic absorption determination of SiO2 in copper composite coatings after extraction of silicomolybdic acid in a mixture of isobutyl methyl ketone and butanol (volume
ratio 5 : 1) and measurement of the molybdenum absorbance in an air/acetylene flame is described. The experimental conditions
are optimized for (i) prevention of the silicon polymerization during sample preparation and storage; (ii) for overcoming
of the Cu(SiF6) – complex formation and (iii) for quantitative extraction of the yellow complex into the organic phase for a wide silicon
concentration range. The method permits the determination of 0.5–10 mg/g Si in copper. The analytical performance of the proposed
method is compared with direct Si determination using ICP-AES.
Received: 15 May 1997 / Revised: 19 September 1997 / Accepted: 25 September 1997 相似文献
15.
Van Elslande E Guérineau V Thirioux V Richard G Richardin P Laprévote O Hussler G Walter P 《Analytical and bioanalytical chemistry》2008,390(7):1873-1879
Microsamples of pink cosmetic powders from the Greco–Roman period were analyzed using two complementary analytical approaches
for identification of the colouring agents (lake pigments originally manufactured from madder plants with an inert binder,
usually a metallic salt) present in the samples. The first technique was a methanolic acidic extraction of the archaeological
samples with an additional ethyl acetate extraction of the anthraquinone-type colouring agents which were identified using
high performance liquid chromatography coupled to electrospray ionization with high resolution mass spectrometry (LC–ESI–HRMS),
and the second was direct analysis of a microsample by laser desorption ionization–mass spectrometry (LDI–MS). The latter
technique is well suited when the quantity of samples is very low. This soft ionization technique enables the detection of
very small quantities of compounds using the combination of positive and negative-ion modes. It was also successfully applied
for the direct analysis of some laboratory-made reference compounds. However, the presence of lead in one of these ancient
samples induced a spectral suppression phenomenon. In this case and conditional on a sufficient quantity of available sample,
the former method is better adapted for the characterization of these anthraquinone-type molecules. This study also confirmed
that purpurin, munjistin, and pseudopurpurin are the principal colouring agents present in these ancient cosmetic powders
constituted from madder plants.
Presented at the Annual French National Symposium on Mass Spectrometry, Electrophoresis and Proteomics, 20–23 September 2007
in Pau, France. 相似文献
16.
Aigars Vītiņš 《Journal of Solid State Electrochemistry》2001,5(7-8):479-486
The impedance of a ZrO2–7.5 mol% Y2O3 ceramic specimen was measured using the two-probe technique in the frequency range 20 Hz–1 MHz at room temperature and in
the temperature range 457–595 K. The novelty of the research lies in the analysis of the intragrain part of the impedance
spectra of the ceramics on the basis of the approach proposed in the literature for impedance of ZrO2–Y2O3 single crystals. The method to determine a value of the intragrain direct current electrical conductivity from an impedance
spectrum has been developed. The frequency dependence of the intragrain complex dielectric response was interpreted according
to the common model used in the literature. Frequency domains, where a power-law dependence having different exponents n
1=0.825–0.844 and n
2=0.571–0.592 is observed, were found. The inner consistency of the model used is verified. Values of the transition frequency
and the relaxation frequency were determined for the grain interiors and compared with each other. The values of the activation
energies of the direct current conductivity, the transition frequency and the relaxation frequency are found to be the same
within experimental uncertainty in the temperature range 457–523 K.
Electronic Publication 相似文献
17.
The complexation of Pb(II) by natural organic matter (NOM) is better described by taking into account the dependence of the
strength of binding on metal loading conditions. The utility of a linear differential equilibrium function for interpretation
of metal ion binding data is demonstrated. This approach considers the binding intensity (log K*) as a function of metal ion
loading (ı = bound metal/binding site concentration). Three methods for calculating this function are presented:
– direct calculation from metal titration curves,
– direct calculation from polarograms, and
– compilation of data derived from interpretation of complexation in terms of one- or two- binding sites (e.g. Scatchard analysis),
i.e. Cc (complexation capacity = effective site concentration)–K pairs.
Heterogeneity also impacts on the apparent lability of complexes; complexes formed at the lowest metal loadings are the least
labile.
Received: 28 December 2000 / Revised: 23 February 2001 / Accepted: 28 February 2001 相似文献
18.
Novel approximate methods for calculating the vibrational structure of the electronic spectra of polyatomic molecules—a method
for the direct calculation of the overlap integrals of vibrational wave functions for the electronic states involved in a
transition and a variational method for the solution of the vibrational problem for the excited states—are discussed. The
methods are based on the consideration of the displacement and entanglement of normal coordinates, the quasiorthogonality
of the Dushinsky transformation, and the classification of the states by total vibrational quantum numbers. Matrix perturbation
theory is employed. It is shown that the accuracy of these methods compares well with the accuracy of the available “exact”
techniques (the errors are ∼1 cm−1 for frequency and 10% for relative intensity). At the same time, calculations by the new methods are performed more than
two orders of magnitude faster than by the previously known methods.
K. A. Timiryazev Agricultural Academy, Moscow. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 217–230, March–April, 1995.
Translated by I. Izvekova 相似文献
19.
Ying Wang Wanhui Liu Kemin Wang Guoli Shen R. Yu 《Fresenius' Journal of Analytical Chemistry》1998,360(6):702-706
A new optical fiber sensor was prepared for the determination of berberine in aqueous solution using a micrometer-sized flow-cell
and a bifurcated optical fiber. The sensing is based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole (PBBO)
in the PVC membrane. This process is accompanied by non-fluorescent ground-state complex formation. With this sensor, berberine
can be determined in sample solutions from 2.42 × 10–5 mol L–1 to 6.04 × 10–7 mol L–1. Satisfactory reproducibility, reversibility, and short response times of less than 1 min are realized. The sensor also shows
good selectivity over some common pharmaceutical species and alkali and alkali-earth metal salts, and can be used for the
direct assay of berberine in commercial tablets. The results are in correspondence with those obtained by the pharmacopoeia
method.
Received: 4 April 1997 / Revised: 8 August 1997 / Accepted: 12 August 1997 相似文献
20.
Combined analytical procedures consisting of wet digestion step followed by instrumental determination – differential pulse
cathodic stripping voltammetry (DPCSV) or electrothermal atomic absorption spectrometry (ETAAS) – as well as a direct analysis
method – slurry sampling ETAAS – for the determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in milk, cheese and chocolate are
described and compared. Wet digestion using a mixture of HNO3-HClO4-H2O2 is proposed for complete matrix decomposition prior to trace analyte determinati on by DPCSV or ETAAS. A mixture of HNO3-H2O2 is used for slurry preparation. Optimal instrumental parameters for trace analyte measurements are presented.
The reliability of the procedures has been verified by analyzing standard reference materials. Results obtained are in good
agreement with the certified values and the relative standard deviations (for these results) are in the range 5–10% for wet
digestion DPCSV or ETAAS and 3–9% for slurry sampling ETAAS in the range of 2 μgċg−1 (Cd) to 12 μgċg−1 (Fe).
Received August 24, 1999. Revision January 20, 2000. 相似文献