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1.
A new sample insertion device for the stabilized capacitive plasma (SCP) has been developed, which enables it to analyze
dry residues of micro amounts of liquid samples. Insertion was applied into an SCP as plasma source because of its good stability
and excitation properties as well as its low instrument and operation costs. The plasma is sustained at a frequency of 27.12 MHz
and an RF power of 150 W. For analysis the liquid samples are positioned at the tip of a quartz rod with the aid of a μL syringe.
Then the sample is dried and the sampling rod inserted into the plasma. After optimization of the carrier gas flow (5 L/h)
and the sample volume (20 μL) the detection limit for Pb with Ar as plasma gas is 200 pg.
By further improving the guidance of the insertion detection limits for Pb, Cu, Cd and Mg in the 1 to 30 ng/mL range or 20
to 600 pg range absolute were obtained. It was found that the detection limits in the case of He are better than those obtained
with Ar. The matrix interferences caused by changes in the concentration of the easily ionizable element Na were found to
be below 10% for Na concentrations of up to 0.45 μg/mL. Ethanol concentrations of up to 14% in the analyte solutions did not
cause any interferences.
Received December 17, 1998. Revision June 4, 1999. 相似文献
2.
Celestino Sanz-Segundo María P. Hernández-Artiga José L. Hidalgo-Hidalgo de Cisneros Dolores Bellido-Milla Ignacio Naranjo-Rodriguez 《Mikrochimica acta》1999,132(1):89-94
The difficulties associated with the development of a microwave-assisted acid digestion of lubricating oils in determination
of wear metals are presented. The interest of this sample treatment lies in its basis for determining the total metal contents
with enough sensitivity by flame atomic absorption spectrometry (FAAS). It allows earlier diagnosis of the engine state than
is obtained by the widely applied simple dilution procedure. Another advantage is the avoidance of contamination and loss
of the metals to be determined. The procedure employs nitric acid and hydrogen peroxide in a four-stage programme. Fe, Cu,
Cr and Pb are determined by FAAS as representative of engine wear. The limits of detection are 0.1 μg/g for Fe and Cr and
0.05 μg/g for Cu and Pb. A comparison with other procedures is presented for spiked samples. Different types of used lubricating
oils supplied by an oil company were analysed to prove the suitability of the procedure proposed.
Received November 11, 1998. Revision Februray 20, 1999. 相似文献
3.
The iodine-azide reaction induced by eight thiosemicarbazones was investigated. Inducing properties of thiosemicarbazones
are different and depend on the parent carbonyl compound used for synthesis. The inductor coefficients of the examined thiosemicarbazones
vary from 61 to 176. Optimum conditions for the determination of microamounts of thiosemicarbazones are given. The detection
limit for the determination by the back-titration method depends on the inducing activity and is 0.9 μg for phenyl-thiosemicarbazones
and 2 μg for diethyl-thiosemicarbazone in a 5-mL sample, and this corresponds to a concentration of 0.9 × 10−6 mol/L and , respectively. The automatic titration with the diluted iodine solution decreases the detection limit to about 50 ng in a
10-mL sample.
Received October 28, 1998. Revision April 9, 1999. 相似文献
4.
The applicability of tetramethylenedithiocarbamate (TMDTC−) and hexamethylenedithiocarbamate (HMDTC−) for colloid flotation separation of manganese in traces from fresh (spring, well and tap) water was studied. The experimental
conditions for the successful manganese separation and preconcentration before electrothermal atomic absorption spectrometric
(ETAAS) determination were optimised. Higher enrichment of manganese was achieved when a larger amount of HMDTC− is used. Applying iron(III) hexamethylenedithiocarbamate, Fe(HMDTC)3, as a precipitate collector, manganese was determined at μg/L levels singly or simultaneously with lead and zinc in 1 L of
water sample. The applicability of the proposed procedure have been verified by analyses of fresh water samples using the
method of standard addition, as well as by comparing the results obtained by ETAAS with those obtained by inductively coupled
plasma-atomic emission spectrometry (ICP-AES). The detection limit of manganese using this method is 0.025 μg/L.
Received August 30, 1999. Revision May 15, 2000 相似文献
5.
The fungicide triadimenol consists of a mixture of two diastereoisomers. Diastereoisomer A (1RS,2SR) could be obtained from the mixture by fractionated crystallization from ethanol/water and toluene, successively, whereas
diastereoisomer B (1RS,2RS) could be separated by column chromatography on a silica gel column using ethylacetate as eluent. Four different crystal
forms of diastereoisomer A could be derived. The modifications were characterized by means of thermal analysis (thermomicroscopy,
DSC), FTIR-spectroscopy, FT-Raman-spectroscopy and powder X-ray diffraction, as well as pycnometry. The thermodynamic relationships
are illustrated in a semischematic energy/temperature-diagram which provides information about the relative thermodynamic
stabilities and physical properties of the four crystal forms. Mod. II (m.p. 132 °C, ΔHf 33.1±0.2 kJ mol−1, density 1.271±0.001 g cm−3) was obtained from toluene after the separation of diastereoisomer A and is enantiotropically related to mod. I (m.p. 138 °C,
ΔHf 32.0 ± 0.2 kJ mol−1, density 1.243±0.001 g cm−3). The transition point of mod. II with mod. I was determined between 30 and 40 °C, which means that mod. II is thermodynamically
stable at ambient conditions. Mod. III (m.p. 112 °C, ΔHf 25.1±0.5 kJ mol−1) and mod. IV were obtained from the melt. Furthermore, the phase diagrams of the binary systems of diastereoisomer B and
the four modifications of diastereoisomer A were calculated by means of the experimentally obtained thermodynamical data.
Received September 30, 1999. Revision July 30, 2000. 相似文献
6.
The surface characteristics of mixed zirconium and titanium oxides prepared from different starting materials are investigated.
One mode of preparation entailed the use of zirconium sulfate and titanium oxysulfate as starting materials and ammonium hydroxide
as precipitating agent. The produced oxides were washed to different extents to obtain samples with different sulfate content.
A second preparative mode used zirconium oxychloride and titanous chloride as starting materials also with ammonium hydroxide
as precipitating agent. The oxidation of the titanous to the titanic form for these oxides was carried out by means of oxygen
gas. Resulting samples were heat treated at 400 °C and 600 °C, and textural characteristics determined from the adsorption
of N2 at 77 K, complemented by infrared and thermal studies.
The samples precipitated from the oxychloride and chloride salts of zirconium and titanium, as well as those precipitated
from the sulfate and oxysulfate salts and washed free of the sulfate ions displayed quite similar textural characteristics.
The unheated samples and those heat-treated at 400 °C were mesoporous, with some microporosity, and relatively large surface
areas in the order of 200–300 m2/g. Heat treatment to 600 °C led to a relative decrease in surface area, in the order of 100 m2/g, and to the disappearance of microporosity.
The mixed zirconium and titanium oxides with a sulfate content of ≈17% displayed significantly lower surface areas, smaller
than 10 m2/g, with a prevalence of micro and mesoporosity. Infrared and thermal studies indicated the presence of differently bounded
sulfato groups, which seem to have a blocking effect on the pores, resulting in the observed smaller surface areas. 相似文献
7.
T. Hellweg C. D. Dewhurst E. Brückner K. Kratz W. Eimer 《Colloid and polymer science》2000,278(10):972-978
Poly (N-isopropylacrylamide) microgel particles are found to form colloidal crystals similar to those occurring in typical hard-sphere
colloids like poly(methylmethacrylate) beads. Samples made of particles with different cross-linker concentrations are investigated
and their deswelling ratio is determined using dynamic light scattering. Small-angle neutron scattering data are also presented
and analysed in terms of a face-centred-cubic crystal structure. The characteristic length, a, of the elementary cell is found to be 535 ± 16 and 495 ± 15 nm for the two systems investigated. This leads to particle
radii of 189 ± 6 and 175 ± 5 nm, respectively. These values compare well to the radii determined using several different methods.
Received: 26 July 1999/Accepted: 21 March 2000 相似文献
8.
J. A. Weima A. M. Zaitsev R. Job G. Kosaca F. Blum G. Grabosch W. R. Fahrner J. Knopp 《Journal of Solid State Electrochemistry》2000,4(8):425-434
Polycrystalline chemical vapor deposition (CVD) diamonds films grown on silicon substrates using the microwave-enhanced CVD
technique were polished using the thermochemical polishing method. The surface morphology of the samples was determined by
optical and scanning electron microscopes before and after polishing. The average surface roughness of the as-grown films
determined by the stylus profilometer yielded 25 μm on the growth side and about 7 μm on the substrate side. These figures
were almost uniform for all the samples investigated. Atom force microscopic measurements performed on the surface to determine
the average surface roughness showed that thermochemical polishing at temperatures between 700 °C and 900 °C reduced the roughness
to about 2.2 nm on both the substrate and growth sides of the films. Measurements done at intermittent stages of polishing
using confocal micro-Raman spectroscopy showed that thermochemical polishing is accompanied by the establishment of non-diamond
carbon phases at 1353 cm−1 and 1453 cm−1 at the initial stage of polishing and 1580 cm−1 at the intermediate stage of polishing. The non-diamond phases vanish after final fine polishing at moderate temperatures
and pressures. Photoluminescence of defect centers determined by an Ar+ laser (λlexct= 514.532 nm) showed that nitrogen-related centers with two zero-phonon lines at 2.156 eV and 1.945 eV and a silicon-related
center with a zero-phonon line at 1.681 eV are the only detectable defects in the samples.
Received: 26 July 1999 / Accepted: 15 November 1999 相似文献
9.
A very sensitive flow-through optosensor with solid phase UV spectroscopic detection is proposed for the direct determination
of adrenaline without prior derivatization. Sample is transported by the carrier stream (0.05 M NaCl/0.01 M NaOH) to the sensing
microzone composed of Sephadex QAE A-25 resin placed in a flow-through cell, and its intrinsic absorbance is monitored at
287 nm. After development of the analytical signal adrenaline is easily and quickly desorbed from the solid support by a 0.7 M
NaCl/0.01 M NaOH eluting solution stream. Adrenaline can be determined in the range 1–12 μg/ml, the detection limit being
0.17 μg/ml. The RSD (10 replicates) and sample throughput are 1.4% and 12 per hour, respectively. The procedure has been successfully
applied to the determination of adrenaline in different medical formulations.
Received May 26, 1999. Revision February 3, 2000 相似文献
10.
Carlos E. C. Magalhães Éder C. Lima Francisco J. Krug Marco A. Z. Arruda 《Mikrochimica acta》1999,132(1):95-100
A method for direct analysis of tea and coffee samples by using electrothermal atomic absorption spectrometry is described.
Coffee and tea from different sources were analyzed without digestion step. For slurry analyses the samples were ground, sieved
at 105 μm and then suspended in 0.2% v/v HNO3 and 10% v/v Triton X-100 medium. For liquid phase aluminium determination the samples were prepared in the same way and only
the liquid is introduced directly into the graphite furnace. Calibration was performed by aqueous standards for both cases
and the determinations were carried out in the linear range between 50 and 250 μg L−1. The characteristic mass of aluminium and the detection limit were 45 pg and 2 μg L−1, respectively. Using a typical 0.1% m/v coffee slurry sample, the relative standard deviation of measurements (n=15) for
repeatability was about 8.2%.
Received December 27, 1998. Revision March 18, 1999. 相似文献
11.
Micellar behavior of acrylamide– octylphenylpoly(oxyethylene) acrylate copolymer in aqueous solution
The copolymer of acrylamide and octylphenylpoly(oxyethylene) acrylate macromonomer (AM-C8PhEO7Ac) was synthesized and characterized by IR and NMR spectroscopy. The molecular weight of the copolymer was determined to
be 1.21 × 105 by static light scattering. The weight contents of AM and macromonomer were determined to be 67.8 and 32.2%, respectively,
by elemental analysis. The micellar behavior of the copolymer in aqueous solution was studied by UV spectroscopy and atomic
force microscopy (AFM). The molecules of AM-C8PhEO7Ac copolymer form monomolecular micelles in the concentration range 4 × 10−6 – 3 × 10−5 g/ml and polymolecular micelles at concentrations above 3 × 10−5 g/ml according to the UV analysis. The AFM images indicate that the monomolecular micelles are globular with diameters of
70 nm and have a narrow size distribution. The polymolecular micelles can be globular or cylindrical depending on the concentration,
and have a wide size distribution.
Received: 10 February 1999 Accepted in revised form: 28 June 1999 相似文献
12.
Three simple and sensitive colorimetric methods (A–C) for the determination of melatonin in bulk samples and in pharmaceutical
formulations are described. They are based on the formation of coloured species by reaction of ninhydrin with the drug (method
A, λmax 397 nm) by oxidation of the indol moiety in melatonin with potassium persulphate (method B, λmax 450 nm) or by reduction of osmium (VIII) (method C, λmax 516 nm). Regression analysis of Beer-Lambert plots showed good correlations in concentration ranges between 0.8–14.2, 70.0–140.0
and 2.0–40.0 μg/mL for methods A, B and C, respectively. The molar absorptivity, Sandell sensitivity and detection limit were
calculated. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The validity of the proposed
methods was tested by analysing pharmaceutical formulations containing melatonin. The relative standard deviations were ≤ 0.95%
with recoveries 99.0–101.33%.
Received October 20, 1999. Revision February 10, 1999. 相似文献
13.
B. Muralidhara Rao 《Mikrochimica acta》1999,132(1):101-103
A new method for the complexometric determination of Bi in the presence of co-ions using 2-mercaptoethanol as selective masking
agent has been proposed. Bismuth along with other ions in a given sample solution are initially complexed with excess of EDTA.
The pH of the solution is adjusted to 5.0–6.0 using solid hexamine (10 ± 2 g) and the remaining uncomplexed EDTA is titrated
with lead-nitrate solution using xylenol orange indicator. A known excess of 2-mercaptoethanol solution (5% alcoholic) is
then added, the mixture is shaken well and the released EDTA from the Bi(III)-EDTA complex is titrated against standard lead-nitrate
solution. The method is applied to the determination of bismuth in Wood’s alloy. Reproducible and accurate results are obtained
for 2–40 mg of bismuth with relative errors ≤ 0.5% and standard deviations ≤ 0.04 mg.
Received January 15, 1999. Revision March 29, 1999. 相似文献
14.
Whether a semiconductor has a direct or an indirect band gap is important in determining physical properties such as photoconductivity
and electroluminescence. For one-dimensional conjugated polymeric semiconductors, as well as organic molecular crystals, we
show how the band gap type (direct or indirect) is determined by the shapes of the HOMO and the LUMO of constituent monomeric
conjugated molecules. The connectivity of the monomer units, and the topology of orbital interaction determine the band gap
type. Pairing symmetry in the π electronic system of even alternant hydrocarbons allows the immediate prediction of the band
gap type, direct or indirect, by examining only the structures of the monomer units and their connectivity in polymers or
molecular stacks.
Received: 29 June 1998 / Accepted: 3 September 1998 / Published online: 8 February 1999 相似文献
15.
There are several methods for sensitive detection of oversulfated chondroitin sulfate (OSCS) in heparin. Although contamination
with OSCS is unlikely to be repeated, use of other compounds to counterfeit heparin must be considered. We have previously
developed a two-step fluorescence microplate assay (two-step FI assay) for detection of OSCS. First, the heparin sample is
incubated with heparinase I, then its increasing effect on the fluorescence intensity (FI) of the sensor molecule Polymer-H
is measured (PolyH assay). The high sensitivity of the assay is shown to be based on heparinase I inhibition by OSCS. The
objective of this study was to evaluate another assay option — indirect quantification of OSCS after heparinase I incubation
by means of the anti-Factor Xa (aXa) activity of the remaining undegraded heparin (two-step aXa assay). We also examined,
whether other heparin mimetics (HepM), direct Factor Xa inhibitors (DXI), and protein impurities are detectable by use of
these assays. Heparin was spiked with different amounts of HepM including OSCS, pentosan polysulfate, dextran sulfate, curdlan
sulfate, the natural contaminant dermatan sulfate, the DXI rivaroxaban, and BSA as a protein. These samples were compared
with pure heparin in the two-step FI assay, the two-step aXa assay, and in the PolyH assay and the aXa assay without heparinase
I incubation. Both two-step assays sensitively measured contamination with all the HepM (LOD ≤ 0.5%, LOQ ≤ 0.7%). The two-step
aXa assay also detected rivaroxaban (LOD 0.3%, LOQ 0.4%), whereas the two-step FI assay was shown to be suited to determination
of protein impurities (LOD 0.11%, LOQ 0.13%). Use of two different heparinase I inactivation procedures enabled clear differentiation
between protein, HepM, and both contaminants. Finally, with the aXa assay the heparin potency can be determined in the same
assay run, whereas the FI increase in the PolyH assay was shown to be useful for identification. In conclusion, both the two-step
FI assay and the two-step aXa assay are sensitive, rapid, and simple tests for the detection of counterfeit heparin. Comprehensive
information about heparin quality can be obtained by their combined use and the parallel measurement of non-incubated heparin
samples. 相似文献
16.
Malachite green oxalate (MG oxalate) and leucomalachite green (LMG) have been prepared and certified as pure reference materials.
The purities of MG oxalate and LMG were assessed by high-performance liquid chromatography–diode array detection (HPLC–DAD),
nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), Karl Fischer titration, ashing and
thermogravimetric analysis (TGA). MG oxalate was purified by supercritical fluid extraction (SFE). Prior to purification,
commercial MG oxalate purity was estimated to be about 90%. The main impurities present in SFE-purified MG oxalate were identified
and quantified using HPLC–DAD. The main impurities were found to be monode-MG (monodemethylated MG oxalate synthesis impurity),
4-(dimethylamino)benzophenone (4-DMABP), MG-carbinol and LMG. The homogeneity of both reference materials was also determined.
Issues associated with the stability of LMG and MG oxalate in solution forced an extensive study investigating different parameters
i.e. solvent, acid, analyte concentration and temperature. MG oxalate (100 μg/mL) was found to be stable in acetonitrile containing
1% v/v glacial acetic acid for at least 155 days and LMG (100 μg/mL) was stable in acetonitrile for at least 133 days. The
final purity value for MG oxalate was 94.3 ± 1.4% m/m at the 95% confidence interval (or 67% m/m if MG cation is reported).
For LMG, the certified purity was found to be 98.8 ± 0.8% m/m at the 95% confidence interval.
Figure Calibration reference materials for malachite green and leucomalachite green, certified for purity, are essential in characterising
these key analytes in a fish matrix reference material 相似文献
17.
The present paper focuses on the characterisation of surface composition and alloying element in-depth distribution of water-atomised
Al–Zn–Mg–Cu alloy powders by secondary ion mass-spectrometry and Auger electron spectroscopy. A pronounced segregation of
Mg and some impurities (Fe, Ca, S) concurrently with some Zn depletion are observed on the powder surface. The oxide film
formed on the powder surface mainly consists of Al and Mg oxides. The film is non-uniform in thickness: rather coarse surface
oxide islands coexist with surface areas covered by a thin (<1.8 nm) oxide layer. The extent of surface oxidation is strongly
affected by solidification conditions: The average thickness of the surface oxides increases with increasing particle size
or with decreasing cooling rate. All alloying elements are homogeneously distributed in the bulk of individual particles.
No significant differences in chemical composition between different particles of a given powder are observed.
Received November 26, 1999. Revision September 25, 2001. 相似文献
18.
V. Natarajan B. Rajeswari B. A. Dhawale N. S. Hon S. V. Godbole V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2009,280(1):27-31
Energy dispersive X-ray fluorescence (EDXRF) spectrometric methods have been developed for the determination of some common
metallic impurities in ThO2 matrix. A series of ThO2 standards containing the analyte impurities in the range 10–100 (or 100–500) μg/g was prepared synthetically. The spectrometer
conditions were optimized to obtain calibration plots for the various analytes. The accuracy and precision of the developed
methodology for regular assay of ThO2 was evaluated by analyzing three synthetic samples. Further three secondary ThO2 standards were analyzed by EDRXF to check the developed methods. The determined concentrations of Ca, Cr, Fe, Ni and Cu were
in good agreement with the certified values of the secondary standards. 相似文献
19.
Tadeusz Błaszczyk Danuta Kaźmierczak Pawel Krzyczmonik Henryk Scholl Krzysztof Polański 《Journal of Solid State Electrochemistry》2000,4(2):95-106
The oxidation of cobalt electrodes has been carried out by means of cyclic voltammetry and coulometry under controlled potential
in sulfuric acid solutions of different concentrations. The electrochemical scanning tunneling microscope/scanning tunneling
microscope (ECSTM/STM) systems constructed by the authors and scanning electron microscopy (SEM) with the SEM-EDX system of
surface analysis of the elements have been used. The procedure applied in this work made it possible to observe the fragments
of the same surface by means of SEM and ECSTM/STM. The most typical images for a polycrystalline Co electrode with a ±10%
accuracy at the scales of 4800 nm × 4800 nm and 100 nm × 100 nm are presented and the results are discussed. In a diluted
electrolyte (0.1 M), irregular forms of a stable cobalt oxide with Co:O ratio ∼1:1 appear. Unreproducible results have been
obtained in a 1.0 M H2SO4 solution. Compact and relatively regular layers of cobalt oxide of the same ratio have been obtained in 0.1 M H2SO4, as well as in 10.0 M sulfuric acid solution, under controlled oxidation potential at the passivation range.
Received: 6 January 1999 / Accepted: 5 May 1999 相似文献
20.
Éder C. Lima Francisco J. Krug Fernando Barbosa Jr Carlos E. C. Magalhães 《Mikrochimica acta》2000,134(1-2):113-121
A tungsten-rhodium coating on the integrated platform of a transversely heated graphite atomiser (THGA) was used as a permanent
chemical modifier for the determination of Cd in sediment slurries by electrothermal atomic absorption spectrometry. Slurries
were ultrasonicated during 20 s before being delivered to the previously W-Rh treated platform. The permanent W-Rh modifier
remains stable by approximately 250 measurements when 20 μl of slurries containing up to 1.0% m/v are delivered into the atomiser.
In addition, the permanent modifier increases the tube lifetime up to 720 analytical firings. Also, when the W-Rh permanent
modifier was employed, there was less variation of the slope of the analytical curves during the total atomiser lifetime,
resulting in a decreased need of re-calibration during routine analysis, increasing the sample throughput.
The atomiser lifetime was limited to the THGA wall durability, because the W-Rh treated platform was intact after more than
720 analytical firings.
Detection limits based on integrated absorbance for 1.0% m/v slurries were 1.5 ng g−1 Cd for 250 μg W +200 μg Rh permanent modifier and 11.5 ng−1 Cd for 5 μg Pd +3 μg Mg(NO3)2.
Results for the determination of cadmium in sediment slurries using the W-Rh permanent modifier were in agreement with those
obtained with dissolved sample solutions by using Pd + Mg(NO3)2, since no statistical differences were found by the paired t-test at the 99% level.
Received September 6, 1999. Revision December 1, 1999. 相似文献