共查询到20条相似文献,搜索用时 31 毫秒
1.
S. G?r?g 《Fresenius' Journal of Analytical Chemistry》1998,362(1):4-8
The present and past use of chemical derivatization reactions is overviewed with emphasis on the present role of derivatization
in chromatographic and electrophoretic methods with special respect to fluorogenic derivatization to increase the selectivity
and sensitivity, chiral derivatization to transform enantiomeric pairs to easily separable diastereomers, and GC/GC-MS derivatization.
Non-chromatographic derivatization is also discussed with emphasis on UV-VIS spectrophotometry, fluorimetry, and immunoassay
methods. The up-to-dateness of derivatization methods with negative examples mainly from the field of UV-VIS analysis are
also discussed. Finally, examples are given on how the experiences obtained in the course of old studies can be used to solve
current problems with the aid of chemical derivatization.
Received: 19 January 1998 / Revised: 2 March 1998 / Accepted: 6 March 1998 相似文献
2.
N. Binding Holger Kl?ning U. Karst Wilhelm P?tter Peter A. Czeschinski Ute Witting 《Fresenius' Journal of Analytical Chemistry》1998,362(3):270-273
Solid sorbents coated with the fluorescent reagent 5-dimethylaminonaphthalene-1-sulfohydrazide (dansylhydrazine, DNSH) have
been used for derivatization and quantitative determination of airborne carbonyl compounds, for example in investigations
on atmospheric pollution. The evaluation of this derivatization reaction presented here revealed that, for several reasons,
it may not be recommended when sampling is performed with impingers containing liquid reagent solutions. Derivative yields
came out to be strongly influenced by water and phosphoric acid which are essential for sufficient derivatization rates, but
also responsible for the degradation of derivatives. Even at water and acid concentrations considered as an optimal compromise
between accelerating and degrading effects, the analytical reliability of the method can only be guaranteed under controlled
laboratory conditions. The reduced or lacking reactivity of DNSH towards aromatic aldehydes or aliphatic and aromatic ketones
is an additional finding discarding the DNSH method for routine air monitoring at least when impingers are used for sampling.
Received: 8 January 1998 / Revised: 9 March 1998 / Accepted: 15 March 1998 相似文献
3.
Kevin A. Wepasnick Billy A. Smith Julie L. Bitter D. Howard Fairbrother 《Analytical and bioanalytical chemistry》2010,396(3):1003-1014
To utilize carbon nanotubes (CNTs) in various commercial and scientific applications, the graphene sheets that comprise CNT
surfaces are often modified to tailor properties, such as dispersion. In this article, we provide a critical review of the
techniques used to explore the chemical and structural characteristics of CNTs modified by covalent surface modification strategies
that involve the direct incorporation of specific elements and inorganic or organic functional groups into the graphene sidewalls.
Using examples from the literature, we discuss not only the popular techniques such as TEM, XPS, IR, and Raman spectroscopy
but also more specialized techniques such as chemical derivatization, Boehm titrations, EELS, NEXAFS, TPD, and TGA. The chemical
or structural information provided by each technique discussed, as well as their strengths and limitations. Particular emphasis
is placed on XPS and the application of chemical derivatization in conjunction with XPS to quantify functional groups on CNT
surfaces in situations where spectral deconvolution of XPS lineshapes is ambiguous.
相似文献
4.
5.
Derivatization of inorganic ions in capillary electrophoresis 总被引:1,自引:0,他引:1
Padarauskas A 《Electrophoresis》2003,24(12-13):2054-2063
This review gives a short overview of the main approaches to the derivatization of inorganic ions in capillary electrophoresis (CE) with emphasis on the most recent works. Various derivatization procedures and detection methods are discussed. A brief account of their advantages and limitations is given. More specific areas such as microchip CE, simultaneous separation of anions and cations, and speciation analysis are also briefly discussed. 相似文献
6.
Molecular recognition: Supramolecular, polymeric and biomimetic coatings for chemical sensors and chromatographic columns 总被引:2,自引:0,他引:2
Complete control of the selective and reversible interaction of molecules from the gas or liquid phase at complementary recognition
sites is of increasing interest for both basic science and practical applications. This recognition may occur at the surface
or in the bulk of optimized chemically sensitive coatings. It is either monitored discontinuously by chromatography or continuously
by a suitable sensor. The latter contains the optimized coating and converts the chemical information about concentrations
of certain molecules by means of a certain transducer into an electronic signal. Generally speaking, these transducers form
the essential part of ‘chemical sensors’; they monitor the molecular interactions at the chemically sensitive layer by changes
in resistivity, impedance, mass, capacitance, work function, heat, electrochemical potential, optical thickness, or optical
absorption in a certain spectral range. Three selected case studies of such molecular recognition devices which utilize supramolecular,
polymeric, and biomimetic coatings are presented. Examples are given for both gas and liquid sensing devices. For simplification,
because of its general applicability and its easy absolute calibration, particular emphasis is put on signal transduction
via quartz crystal oscillators. The measurement principle is based on frequency changes which are directly correlated with
mass changes and thus provide a particularly suitable signal transduction. The examples presented here concern systematic
variations in the design of supramolecular cages, of selective interaction sites in polymeric matrices, and of covalently
attached biomimetic recognition sites to monitor antibodies or enzyme interactions.
Received: 11 August 1997 / Revised: 3 March 1998 / Accepted: 3 March 1998 相似文献
7.
Complete control of the selective and reversible interaction of molecules from the gas or liquid phase at complementary recognition
sites is of increasing interest for both basic science and practical applications. This recognition may occur at the surface
or in the bulk of optimized chemically sensitive coatings. It is either monitored discontinuously by chromatography or continuously
by a suitable sensor. The latter contains the optimized coating and converts the chemical information about concentrations
of certain molecules by means of a certain transducer into an electronic signal. Generally speaking, these transducers form
the essential part of ‘chemical sensors’; they monitor the molecular interactions at the chemically sensitive layer by changes
in resistivity, impedance, mass, capacitance, work function, heat, electrochemical potential, optical thickness, or optical
absorption in a certain spectral range. Three selected case studies of such molecular recognition devices which utilize supramolecular,
polymeric, and biomimetic coatings are presented. Examples are given for both gas and liquid sensing devices. For simplification,
because of its general applicability and its easy absolute calibration, particular emphasis is put on signal transduction
via quartz crystal oscillators. The measurement principle is based on frequency changes which are directly correlated with
mass changes and thus provide a particularly suitable signal transduction. The examples presented here concern systematic
variations in the design of supramolecular cages, of selective interaction sites in polymeric matrices, and of covalently
attached biomimetic recognition sites to monitor antibodies or enzyme interactions.
Received: 11 August 1997 / Revised: 3 March 1998 / Accepted: 3 March 1998 相似文献
8.
M. Valcárcel Mercedes Gallego Angel Ríos 《Fresenius' Journal of Analytical Chemistry》1998,362(1):58-66
The interfaces between low-pressure continuous sample treatment systems and high-level information instruments such as gas
chromatographs, capillary electrophoresis equipment and graphite furnace atomic spectroscopic instruments, which are characterized
by conventional discrete sample introduction devices, are presented. The present and future developments are discussed of
(directly) linking real samples and those analytical equipments with the main objective of avoiding or minimizing manually
implemented preliminary operations of the analytical process.
Received: 27 January 1998 / Revised: 5 March 1998 / Accepted: 7 March 1998 相似文献
9.
Microwave radiation is used to speed up chemical derivatization. In the present study, three microwave-assisted techniques for the methylation of chlorophenoxy acid herbicides prior to analysis by gas chromatography coupled with mass spectrometry are compared. Derivatization was performed with the catalysts sulphuric acid and boron trifluoride as well as with trimethylsilyldiazomethane. In order to establish optimized and stable conditions, a screening for statistically significant factors by means of experimental designs was carried out and supplemented by a careful optimization. Special emphasis has been given to an accurate validation to prove the performance of the techniques. Furthermore, all microwave-assisted methods were compared with their conventional analogues. The optimized methods are valid for routine analysis of different matrices such as water, soil, sediment or tissues, especially for high sample throughput since a simultaneous derivatization of up to 64 samples in one run is possible. 相似文献
10.
11.
N. Huppert Marion Würtele Hermann H. Hahn 《Fresenius' Journal of Analytical Chemistry》1998,362(6):529-536
A rapid, inexpensive and solvent-free method for the simultaneous determination of the polyamide plasticizer N-butylbenzenesulfonamide
(NBBS) and the widely used pharmaceutical Ibuprofen by solid phase microextraction (SPME) combined with gas chromatography/mass
spectrometry (GC/MSD) in wastewater samples was developed. Besides the optimized analytical conditions, results of investigations
with varying analytical parameters are reported. Problems, which may occur during the analytical procedure (e.g. salt deposits,
adsorption phenomena, carry-over), are discussed. For the determination of Ibuprofen, it is important to carry out the extraction
under acidic conditions with sufficiently buffered samples; the GC/MSD system must be very clean and well maintained. SPME
allows an extraction of Ibuprofen without derivatization of its carboxylic group. For quantification in complex matrices,
the standard addition technique is necessary. Limit of detection and limit of determination are 0.1 μg/L for both analytes.
NBBS and Ibuprofen were detected in several raw and treated wastewater samples from municipal wastewater treatment plants
in the range from < 0.1 to 3.5 μg/L.
Received: 13 March 1998 / Revised: 16 June 1998 / Accepted: 19 June 1998 相似文献
12.
13.
Thermoanalytical (TA) methods are relatively seldom applied for assessing the physical and chemical proeprties of thin films, but they can be used in studies of composition, phase transitions and film—substrate interactions. In the present paper the possibilities of TA methods in thin film studies are reviewed. The thermoanalytical methods considered are the classical TG and DTA/DSC methods but some complementary methods will also be briefly mentioned. The main emphasis is given to true thin films. Details of sample preparation are also given. An important application of TA methods is characterization of precursors for the CVD growth of thin films, and this is also discussed. 相似文献
14.
P. C. Uden Susan M. Bird Mihaly Kotrebai Paula Nolibos Julian F. Tyson Eric Block Eric Denoyer 《Fresenius' Journal of Analytical Chemistry》1998,362(5):447-456
Consumption of selenium enriched plants or yeast-based nutritional supplements has been reported to provide anticarcinogenic
benefits which are selenium compound dependent. Separation and identification of these selenium compounds is critical to understand
the activity. Plants and yeast convert inorganic selenium in the soil or growth media into organoselenium compounds, probably
following a route similar to the sulfur assimilatory pathway. Non-volatile selenium compounds produced include selenoamino
acids, some of which have shown anticarcinogenic activity. Volatile compounds produced by chemical reaction of involatile
precursors have also been found. An ion pair chromatographic method with ICP-MS detection for the separation of selenoamino
acid standards potentially present in real samples is given. The method allows separation of selenoamino acids including such
analytes as the cis-trans isomers of Se-1-propenyl-dl-selenocysteine. The method also provides the capability of determining the presence of selenoxides and possibly selenones,
and tracking of other functionalities and reactions by selective derivatization. Alternatively, selenoamino acids are treated
with ethylchloroformate to produce stable volatile derivatives which are amenable to GC separation with element specific atomic
emission detection (GC-AED). Results of total selenium determination and speciation of selenium enriched yeast-based nutritional
supplements, selenium enriched allium vegetables and bioremediation samples are presented.
Received: 16 February 1998 / Revised: 4 June 1998 / Accepted: 9 June 1998 相似文献
15.
V. Minganti R. Capelli R. De Pellegrini 《Fresenius' Journal of Analytical Chemistry》1995,351(4-5):471-477
A multi-element, element-specific detector for gas chromatography (GC) based on atomic emission spectroscopy (AES) with a microwave induced plasma (MIP) source was tested on some environmental samples. As derivatization procedure, direct aqueous phase ethylation and chelation/extraction followed by Grignard reaction were tested on the following ions: methylmercury, ethylmercury, phenylmercury, mercury(II), trimethyllead, dimethyllead, lead(II), trimethyltin, dimethyltin, triethyltin, tripropyltin, tributyltin, dibutyltin, butyltin, and tin(IV). For mercury species a direct aqueous phase phenylation was successfully tested. The different methods of derivatization are compared, and the performance (sensitivity, linearity) of the GC-MIP-AES system is discussed. Some examples of application to environmental samples (biological tissues) are given. 相似文献
16.
Van Berkel GJ Quirke JM Adams CL 《Rapid communications in mass spectrometry : RCM》2000,14(10):849-858
A survey of derivatization strategies and prospective derivatization reactions for conversion of simple alkenes and alkynes to 'electrospray-active' species is presented. General synthetic strategies are discussed and illustrative examples of prospective derivatives prepared from model compounds are presented along with their electrospray ionization (ES) mass spectra. The identified derivatives of these neutral, nonpolar analytes are either ionic or are ionizable in solution through Bronsted acid/base chemistry, by Lewis acid/base chemistry, or by chemical or electrochemical electron-transfer chemistry. Once ionized, the derivatives are expected to be amenable to detection by electrospray ionization-mass spectrometry. Derivatives are identified for positive and negative ion analysis of both alkenes and alkynes. Copyright 2000 John Wiley & Sons, Ltd. 相似文献
17.
Following an approach to density functional theory calculations based on the matrix representation of operators, we implemented
a scheme as an alternative to traditional grid-based methods. These techniques allow integrals over exchange-correlation operators
to be evaluated through matrix manipulations. Both local and gradient-corrected functionals can be treated in a similar way.
After deriving all the required expressions, selected examples with various functionals are given.
Received: 7 March 1998 / Accepted: 21 May 1998 / Published on line: 6 August 1998 相似文献
18.
V. Schütz V. Purtuc S. Felsinger W. Robien 《Fresenius' Journal of Analytical Chemistry》1997,359(1):33-41
A new method for spectrum prediction is presented permitting incorporation of stereochemical features, which highly improves
the quality of the obtained chemical shift values. The method is based on comparison of the query-structure with a reference
library of ring skeletons, so that stereochemical interactions can be counted. The number of stereochemical interactions obtained
over a five-bond sphere is used to produce a three-dimensional HOSE-code leading to a more accurate spectrum prediction. The
advantages of this new concept will be discussed using examples from natural product chemistry.
Received: 25 October 1996/Revised: 20 March 1997/Accepted: 29 March 1997 相似文献
19.
Elemental speciation analysis in capillary electrophoresis 总被引:1,自引:0,他引:1