共查询到20条相似文献,搜索用时 15 毫秒
1.
Molecular activation analysis for iridium 总被引:1,自引:0,他引:1
C. F. Chai P. Kong X. Y. Mao S. L. Ma 《Journal of Radioanalytical and Nuclear Chemistry》1995,192(1):101-108
Molecular activation analysis (MAA) of iridium in geological samples, based on a combination of a newly-developed chemical sequential dissolution method and radiochemical and instrumental NAA, was described to study the distribution pattern and chemical species of iridium in various fractions (soluble carbonate, metal, sulfide, oxide, silicate and acid-insoluble residue) of geological boundary samples, meteorites, ultrabasic rock and volcanic lava. The correlations of Ir with Au, Os, siderophile, chalcophile and lithophile elements were discussed. In addition, the role of kerogen and noble-nugget in the Ir enrichment was scrutinized. The MAA results of Ir favors a mixed effect of asteroid impact, volcanic eruption and post-depositional redistribution to interpret the extant Ir anomaly at Cretaceous-Tertiary boundary layer. 相似文献
2.
Y. Serfor-Armah B. J. B. Nyarko E. K. Osae D. Carboo F. Seku 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(1):193-197
Eight seaweed species were sampled for a two year period from June 1996 to August 1998 along the coast of Ghana which is being
washed by the gulf of Guinea (part of the Atlantic ocean). An analysis was made of the levels of fourteen chemical elements
namely: Al, As, Au, Ca, Cd, Fe, K, Mg, Mn, Na, Ni, Hg, V and Zn by instrumental neutron activation analysis (INAA). Apart
from As, Au, Cd, Fe, and Hg the elements were measured in all the seaweed species studied. Al, Ca, K, Mg, and Na generally
showed the highest concentrations in most of the species analysed while the Hg content was low. The results showed high variability
in and between species, among sampling sites and times of collection. The high values of metal concentration in the macroalgae
suggest that these marine organisms can be used as biological indicators for studying marine pollution. 相似文献
3.
R. Kurt V. Hoffmann R. Reiche W. Pitschke K. Wetzig 《Fresenius' Journal of Analytical Chemistry》1999,363(2):179-184
Analytical methods with low detection limits were used for the investigation of Ir-Si thin films, the physical properties
of which vary strongly with the chemical composition and the amount of impurities. It is demonstrated how to solve chemical
characterization of different thermoelectric Ir-Si thin films by spark source mass spectrometry (SS-MS), glow discharge optical
emission spectroscopy (GD-OES) and X-ray photoelectron spectroscopy (XPS). The combined use of the three different facilities
allows the quantification of impurities of elements of the entire periodic system in the ppm range (down to 30 at.-ppm in
dependence on the element) incorporated in thin film samples. Additional information about the in-depth distribution of elements
or specifically bonded species can be achieved with a high depth resolution.
Received: 6 April 1998 / Revised: 9 July 1998 / Accepted: 14 July 1998 相似文献
4.
A. P. Paiva 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(1):135-141
The aim of this paper is to put in evidence the role played by solvent extraction when it is used as an analytical tool, in
association with activation analysis, to avoid problematic interferences or to increase the detection limit of specific elements
or groups of elements present in various sorts of samples. Some significant examples of this successful association, particularly
from the 1980 decade, are presented and discussed according to the type of chemical reaction involved in the extraction of
the species of interest to be determined. Solvent extraction is no longer widely used for this specific purpose, however,
the acquired knowledge has been the basis for the development of other alternative methods for separation and/or pre-concentration,
applied to different matrixes, prior to, or after, activation analysis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
A versatile, relatively selective, chemically and mechanically robust solid-phase microextraction (SPME) fiber based on methacrylic acid-trimethylolpropanetrimethacrylate (MAA/TRIM) co-polymers was developed in a simple way and directly coupled with gas chromatography. Thus, using a glass capillary as a "mold", MAA/TRIM co-polymers were immobilized on a stainless steel wire base as a novel coating for SPME. The extraction performance of the MAA/TRIM-coated fiber was evaluated in detail using four triazines as model compounds, and several typical and important species of chemical compounds including opioids, xanthic alkaloids and phenoxyacetic acid herbicides were selected as additional examples to further illustrate the extraction mechanism and applicability of the fiber. The fiber showed high extraction efficiency for highly functionalized molecules (typically containing multiple amino, hydroxy, carbonyl and carboxy groups) via a hydrogen-bonding extraction mechanism. The maximum extraction ability and selectivity of the fiber could be obtained only in non-polar (aprotic) organic solvents, which are effective for the hydrogen-bonding interaction. The inherent chemical stability of MAA/TRIM co-polymers and the mechanical strength of the stainless steel wire as the fiber support made the MAA/TRIM-coated fiber highly durable in practical use. 相似文献
6.
Letizia Canziani Manuela Marenco Giorgio Cavenaghi Giulia Manfrinato Angelo Taglietti Alessandro Girella Carlo Aprile Giovanna Pepe Lorenzo Lodola 《Molecules (Basel, Switzerland)》2022,27(2)
Background: Macroaggregated human serum albumin (MAA) properties are widely used in nuclear medicine, labelled with 99mTc. The aim of this study is to improve the knowledge about the morphology, size, dimension and physical–chemical characteristics of MAA and their bond with 99mTc and 68Ga. Methods: Commercial kits of MAA (Pulmocis®) were used. Characterisation through experiments based on SEM, DLS and Stokes’ Law were carried out. In vitro experiments for Langmuir isotherms and pH studies on radiolabelling were performed and the stability of the radiometal complex was verified through competition reactions. Results: The study settles the MAA dimension within the range 43–51 μm. The Langmuir isotherm reveals for [99mTc]MAA: Bmax (46.32), h (2.36); for [68Ga]MAA: Bmax (44.54), h (0.893). Dual labelling reveals that MAA does not discriminate different radioisotopes. Experiments on pH placed the optimal pH for labelling with 99mTc at 6. Conclusion: Radiolabelling of MAA is possible with high efficiency. The nondiscriminatory MAA bonds make this drug suitable for radiolabelling with different radioisotopes or for dual labelling. This finding illustrates the need to continue investigating MAA chemical and physical characteristics to allow for secure labelling with different isotopes. 相似文献
7.
K. Janssens L. Vincze B. Vekemans C. T. Williams M. Radtke M. Haller A. Kn?chel 《Fresenius' Journal of Analytical Chemistry》1999,363(4):413-420
The sensitivity and applicability of the synchrotron radiation induced X-ray microfluorescence (μ-SRXRF) spectrometer at
the Hamburg synchrotron laboratory Hasylab for the determination of the distribution of trace concentrations of rare-earth
elements (REE) in fossilized bone are discussed and critically compared to those of other trace analytical methods such as
instrumental neutron activation analysis (INAA) and LAMP-ICPMS (laser ablation microprobe inductively-coupled plasma mass
spectrometry). Measurements were carried out on two bone samples from contrasting terrestrial depositional environments at
Olduvai Gorge (Tanzania). Results indicate that the microdistribution of the REE in these biological materials is not homogeneous
and that the relative abundance of these elements can provide information on the palaeoenvironment during the fossilization
process. The heterogeneous distribution of the REE can be determined in a quantitative and completely non-destructive manner
provided the concentrations of individual REE are above 10 μg/g.
Received: 18 January 1998 / Revised: 6 October 1998 / Accepted: 10 October 1998 相似文献
8.
Trace elements in land plants: Concentration ranges and accumulators of rare earths,Ba, Ra,Mn, Fe,Co and heavy halogens 总被引:2,自引:0,他引:2
M. Koyama M. Shirakawa J. Takada Y. Katayama T. Matsubara 《Journal of Radioanalytical and Nuclear Chemistry》1987,112(2):489-506
More than 2000 samales of land plant leaves, mostly of tree, have been analyzed by neutron activation analysis in order to find out macroscopic relations between distributions of chemical elements in plants and soil characteristics. The distributions of the elements in plants were also examined from the view point of botanical taxonomy or phylogeny. New species which accumulate Co, rare earths, Ba, Ra, heavy halogens and some other elements have been found. Capability or potentiality for accumulating elements could be related to higher ranks of taxonomy, that is, genus or family. The nature of soil is also found to have profound effects on the extent of accumulation of elements in plants. 相似文献
9.
Studies on batch emulsion copolymeization of styrene with acrylic acid (AA) or methacrylic acid (MAA) were carried out. The
effect of AA or MAA on the total conversion of the monomers was studied by a gravimetric method. The distribution of the carboxylic
group in the copolymer microspheres was investigated by X-ray photoelectron spectroscopy and elemental analysis. The surface
content of the carboxylic groups of styrene (St)/AA copolymer microspheres was found to be higher than that of St/MAA copolymer
microspheres. The effects of partial neutralization of MAA in emulsifier-free emulsion copolymerization and seeded emulsion
copolymerization on the distribution of the carboxylic group was also investigated.
Received: 14 December 1999/Accepted: 23 August 2000 相似文献
10.
R. Cornelis 《Journal of Radioanalytical and Nuclear Chemistry》2000,244(2):255-257
Speciation analysis of trace elements is the identification and/or measurement of the quantities of one or more individual chemical species in a sample. The general procedure starts with the separation of the species followed by the measurement of trace elements in the different fractions. The identification of the species may be done by UV-detection, mass spectrometry or other techniques. For the development of the methodology, and for in-vivo and in-vitro studies radiotracers are ideally suited. In speciation analysis of trace elements in biological fluids and tissues the search goes on for small inorganic and organometallic compounds, and for metal-protein complexes. 相似文献
11.
F. C. Adams 《Accreditation and quality assurance》1998,3(8):308-316
The basic concepts of traceability as they are defined by the Comité Consultatif pour la Cluantité de Matière are contrasted
with the practical exploitation in chemical analysis. The applicability of traceability concepts are tested for their practical
applicability on four different analytical methodologies, neutron activation analysis, plasma mass spectrometry, beam microscopical
analysis and speciation analysis of organometallic compounds.
Received: 31 March 1998 · Accepted: 6 June 1998 相似文献
12.
Andrea Tredici Roberta Pecchini Massimo Morbidelli 《Journal of polymer science. Part A, Polymer chemistry》1998,36(7):1117-1126
The application of self-propagating frontal polymerization (FP) to synthesize copolymers has been investigated. Frontal copolymerizations of methyl methacrylate and methacrylic acid (MMA–MAA), acrylic acid and methacrylic acid (AA–MAA), and styrene and methacrylic acid (STY–MAA) with benzoyl peroxide (BPO) as initiator have been performed. The measured front velocities have been compared with the results of a suitably developed model. This is based on the pseudokinetic approach, accounts for the depropagation reaction, and is fully predictive; i.e., it does not include any adjustable parameter (although one had to be used for the specific experimental setup used in this work). An explicit, simplified solution of the model has been obtained using the constant pattern approximation. The microstructures of copolymers produced in bulk and by FP have been analyzed by differential scanning calorimetry. Their comparison indicates that self-propagating frontal copolymerization provides a substantial improvement in the uniformity of the chain composition distribution. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1117–1126, 1998 相似文献
13.
C. Chen Peiqun Zhang Xiangli Lu Xiaolin Hou Zhifang Chai 《Analytical and bioanalytical chemistry》1999,363(5-6):512-516
The elemental concentrations and chemical species of Al, Br, Cl, Cu, K, Mg, Mn, Na and I in human liver and its subcellular
fractions were studied by several biochemical techniques combined with neutron activation analysis. The highest concentrations
of Al, Mg, and I were found in the nuclei, whereas those of Br, Cu, Cl, K, Mn and Na in the cytosol. About 20% of Br, half
of Al and most of Cu (78.8%), Mg (65.9%) and Mn (80.6%) remained in the cellulose bags after dialysis of liver homogenate,
which were suggested to be bound to macromolecules. K (100%) and more than 95% of Cl and Na were found to be in the dialyzates.
Similar results were found in the fractions of nuclei, mitochondria, lysosome and microsome, respectively, after the same
treatment. Further study was carried out to elucidate the elemental distribution in the cytosol by ethanol precipitation and
by ammonium sulfate fractionation. The results suggested that several kinds of Cu-, Mn- and Mg-bound proteins existed in the
cytosol of human liver cells.
Received: 3 August 1998 / Revised: 22 September 1998 / Accepted: 26 September 1998 相似文献
14.
Zeev B. Alfassi 《中国化学会会志》1990,37(2):101-115
Activation analysis in general and mainly reactor neutron activation analysis (NAA) has been used extensively for measuring trace elements in high purity materials, particularly semiconductor materials. The advantages of NAA in determination of trace elements differ from one semiconductor material to another. For all of them the inherent properties of activation analysis especially those of non contamination with the reagents, low blanks and high sensitivity are the reasons for the choice of NAA as the main analytical procedure. These inherent properties are essential for analysis of high-purity materials where concentrations of ppb's and sub ppb's have to be measured. NAA is specially suitable for the determination of trace elements in silicon due to the very short lived very low activity induced by neutron reaction in silicon. This enables easy instrumental (i.e. without chemical separations) determination of trace elements in silicon. In the HFR reactor at Peten, Netherlands, a special facility was constructed for irradiation of silicon samples of Philips, in which silicon wafers of up to 15 cm diameter can be irradiated with 4 × 1013n. cm?2. sec?1 and the irradiation is done for 72–96 hours. using large Ge(Li) detectors (100 to 150cc) and long counting time (8–16 hours) they measured 22 elements in concentrations below ppb and 10 others between ppb and 300 ppm. Trace elements in germanium have been determined both instrumentally after very long decay time (100 days) or after short decay time removing the activities from the matrix by chemical separation. Trace elements in GaAs are determined only after chemical separtion. Several other semiconductor material such as Sc, Te, GaP and CuInS2 were also determined by NAA. Some trace elements cannot be determined by neutron activation. Carbon, nitrogen and oxygen are determined by activation with protons, alphas or 3He particles. Boron and hydrogen are determined by prompt emission induced by charged particle activation, which gives not only the total concentration but also the depth profile. Carbon, nitrogen, oxygen and phosphorus were also determined by prompt proton activation analysis. The environmental samples studied by activation analysis can be divided into three categories: atmospheric aerosols, water samples and solid wastes. NAA of atmospheric aerosols have been used for their posible toxicological hazards, their source identification and for studies of atmospheric transport processes. 相似文献
15.
Xiaolin Hou 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(1):49-61
The compositional changes of inorganic elements on freshwater leaching of 35 species of Chinese algae were studied by the
determination of the element contents in marine algae using instrumental neutron activation analysis. It was found that alkali
metals and chlorine mainly exist as ions in algae, in which, water-soluble K and Na exist as chlorides. While, other elements
exist as the states of both ions and organic combination in which the water leaching ratios of alkaline earth metals are the
lowest. The combination of trace elements with various organic macromolecules inSargassum kjellmanianum was also studied using neutron activation analysis combined with chemical and biochemical separation techniques. The results
indicate that the concentration of many trace elements, such as Zn, Fe, Sc, Th are earths in protein are quite high, and some
trace elements can also be combined by pigment and polyphenol. Alkaline earth metal mainly bind with alginic acid inSargassum kjellmanianum. 相似文献
16.
Ch. L. Ndiokwere 《Journal of Radioanalytical and Nuclear Chemistry》1984,85(6):325-337
This study of the inorganic chemical composition of 10 different Nigerian medicinal plant species, using the technique of instrumental neutron activation analysis /INAA/, resulted in the determination of the concentrations of 18 major, minor, and trace elements: Al, Ba, Br, Ca, Cl, Eu, Fe, Ga, K, La, Mn, Na, Sb, Sc, Si, Sm, V, and Zn. The parts of the plants used were roots, leaves, and bark. The NBS SRM 1571 Orchard Leaves was also analyzed to assess the accuracy of the procedures used. 相似文献
17.
CHEMICAL SPECIES OF IRIDIUM AND OTHER TRACE ELEMENTS AT K-T BOUNDARY CLAY LAYER, STEVNS KLINT, DENMARK, AND ITS IMPLICATION 总被引:2,自引:0,他引:2
The chemical species of anomalous Ir in the Fish Clay K-T boundary at Stevns Klint, Denmark, was studied by using a newly-developed chemical stepwise dissolution procedure and neutron activation analysis. The experimental results indicate that the anomalous Ir mostly exists in the acid-insoluble residue phase. The Ir pattern of the K-T boundary resembles that of the Ningqiang carbonaceous chondrite, while remarkably different from those of the ultrabasic rock and volcanic lava. Thus, we deduce that the Ir anomaly at K-T boundary is mainly extraterrestrial, instead of volcanogenic or geochemical enrichment origin. The patterns of other trace elements in various phases also confirm the above conclusion. 相似文献
18.
B. Michalke 《Analytical and bioanalytical chemistry》1999,363(5-6):439-445
This contribution describes the need and some strategies for a rigid quality control in speciation analysis. Firstly, the
term “chemical speciation” is defined and differentiated from experimental concepts now called “operationally defined speciation”
or “functionally defined speciation”. The need for quality control in speciation is given by the big number of sources of
errors during sampling, sample preparation, separation and detection. Errors such as stability problems, contaminations or
losses, spectral interferences etc. are discussed. On the other hand, several concepts for problem solutions are described.
One of these solutions is the use of certified reference materials (CRM). Unfortunately, species-certified CRM are only available
for few matrices and few elements, e.g. mercury in fish or sediments, lead in solutions and urban dust etc. Therefore special
quality control strategies are necessary for each part of the analytical speciation procedure. Several examples of such procedures
are given and discussed.
Received: 25 July 1998 / Accepted: 8 August 1998 相似文献
19.
Optical waveguide sensors in analytical chemistry: today’s instrumentation, applications and trends for future development 总被引:1,自引:0,他引:1
R. A. Potyrailo S. E. Hobbs G. M. Hieftje 《Fresenius' Journal of Analytical Chemistry》1998,362(4):349-373
Current concepts for chemical and biochemical sensing based on detection with optical waveguides are reviewed. The goals
are to provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection
techniques and waveguide arrangements. Sensor designs are categorized on the basis of the five parameters that completely
describe a light wave: its amplitude, wavelength, phase, polarization state and time-dependent waveform. In the fabrication
of a successful sensor, the physical or chemical property of the determined species and the particular light wave parameter
to detect it should be selected with care since they jointly dictate the sensitivity, stability, selectivity and accuracy
of the eventual measurement. The principle of operation, the nature or the detected optical signal, instrumental requirements
for practical applications, and associated problems are analyzed for each category of sensors. Two sorts of sensors are considered:
those based on direct spectroscopic detection of the analyte, and those in which the analyte is determined indirectly through
use of an analyte-sensitive reagent. Key areas of recent study, useful practical applications, and trends in future development
of optical waveguide chemical and biochemical sensors are considered.
Received: 19 January 1998 / Revised: 15 May 1998 / Accepted: 21 May 1998 相似文献
20.
Neutron activation analysis has been used to assay the trace elements Co, Fe, Sc, Rb and Zn in pollen and derived sporopollenins.
The method is capable of high precision and avoids the necessity for sample ashing and the introduction of reagent contamination.
Rubidium was completely removed during the chemical isolation of sporopollenins and the remaining elements which survived
chemical treatment were found in reduced amounts. The ratio of Sc: Fe in pollen and in several derived sporopollenins was
found to be approximately constant. Results are discussed with reference to the possibilities of anomalous chemical behaviour
of the elements resulting from irradiation. 相似文献