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1.
Based on comparison of the results ofab initio and semiempirical configuration-interaction calculations, we have plotted the potential energy surface for the ground state
and a number of low-lying excited states of ozone which correlate with the three lowest dissociation limits. We calculate
the matrix elements for the spin-orbit coupling operator at points of singlet-triplet term crossing. Based on this, we evaluate
the nonadiabatic decomposition process
occurring with a change in spin on absorption of ozone in the Huggins band. We also predict a triplet-singlet nonadiabatic
transition in the triplet channel for recombination of the speciesO(
3
P)+O
2(X
3
Σ
g
−
) with formation of ozone in the ground state.
Cherkassy Engineering and Technological Institute, 460 Bul’var Shevchenko, 257006 Cherkassy, Ukraine. Translated from Teoreticheskaya
i éksperimental’naya Khimiya, Vol. 33, No. 4, pp. 219–223, July–August, 1997. 相似文献
2.
The ground state and some lowest excited states of ozone are calculated by the semiempirical MNDO method using configuration
interaction to explain the Wulf absorption band and photodissociation of ozone. The results of calculations show that3A2(13A′’) is the lowest excited triplet state of O3; a transition to this state from the ground X1 A1 state is responsible for the weak Wulf absorption. The oscillator strength (f = 3.2·10-7) and the radiative lifetime of the A2 state (Τ = 0.01 s) are in agreement with recent ab initio calculations.
Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 6, pp. 1067–1073, November–December, 1997. 相似文献
3.
Using the technique of liquid scintillation,32P and45Ca activites were determined in biological samples such as bones, blood, milk and egg shells, white and yolk. Samples were
mineralized in 70% HClO4 and 30% H2O2 at 70 °C and measured after addition of the “Aquasol” scintillation liquid. A correction for quenching was made by the method
of sample channels ratio. High detection efficiencies were obtained, above 80% for45Ca and about 50% for32P in a second measuring channel. Recoveries amounted to 0.95–1.06 for32P and to 0.93–0.98 for45Ca. 相似文献
4.
A. N. Garg A. Kumar R. P. Choudhury 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(2):481-488
A nondestructive NAA method based on the reaction 31P(n,γ)32P (T
1/2 = 14.23 d) has been developed where the product nucleus, a pure β-emitter with end point energy 1.71 MeV is measured by using
an end window G.M. counter and an Al filter of 27 mg·cm−2. 32P was identified by measuring E
β using Feather’s analysis and its half-life was found to be 15.3±0.2 days in standard reference materials (SRMs) and samples.
For most reference materials (RMs) from NIST (USA) and IAEA (Vienna), our values agree within ±5% of the certified values.
A variety of biological samples have also been analyzed and our values are in the range; medicinal herbs (n = 43), 0.29–5.23 mg/g; bhasmas (n = 19), 0.09–51.4 mg/g; vegetables (n = 8), 1.85–5.73 mg/g; lentils (n = 6), 2.1–5.5 mg/g; flours (n = 6), 1.3–3.3 mg/g; vegetarian diet (n = 5), 2.41–2.90 mg/g; fish (n = 43), 3.61–36.8 mg/g; human and animal milk (n = 6), 1.24–7.95 mg/g; commercial milk powders (n = 14), 2.76–11.9 mg/g; water from various sources (n = 14), 1–417 μg/l; human and animal blood (n = 9), 1.00–15.0 mg/g; cancerous and healthy breast tissue (n = 60), 1.00–8.63 mg/g; human hair (n = 43), 0.12–5.81 mg/g, where n is the number of samples analyzed. The method is simple, fast, and nondestructive and provides
data within ±5% error limit with a detection limit of 0.1 mg/g. 相似文献
5.
Determination of endosulfan and some pyrethroids in waters by micro liquid-liquid extraction and GC-MS 总被引:1,自引:0,他引:1
A. Fernández-Gutiérrez J. L. Martínez-Vidal F. J. Arrebola-Liébanas A. Gonzalez-Casado J. L. Vílchez 《Fresenius' Journal of Analytical Chemistry》1998,360(5):568-572
A simple, rapid and reproducible method for the determination of some pesticide residues in water was developed using micro
liquid-liquid extraction and gas chromatography - mass spectrometry with selected ion monitoring (GC/MS-SIM). The chlorinated
insecticides α- and β-endosulfan and endosulfan-sulfate as well as the synthetic pyrethroids bifenthrin, permethrin, cypermethrin,
fenvalerate and deltamethrin can be separated from a 500 mL sample water extracted with 0.5 mL of n-hexane containing anthracene-d10 as internal standard without clean-up in only 13 min. The recovery efficiencies of the tested compounds yielded more than
93.0% at a fortification level of 5 ng mL–1 and their relative standard deviations were between 1.9 and 11.7%. Detection limit of each compound ranged between 3 and
35 pg mL–1. The method was applied to ground, sea and tap waters from Almería (Spain). The solubilities in water at 20° C were determined.
Received: 21 March 1997 / Revised: 28 July 1997 / Accepted: 18 August 1997 相似文献
6.
Y. Ogata 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(1):253-256
Liquid scintillation counting is widely used to measure radioactivity, but it generates radioactive organic liquid waste.
Not to generate the liquid waste using a liquid scintillation counter, novel counting method with a plastic scintillation
vial was designed. The counting efficiency for 32P was 10–40% and that for 125I was 4–8%. The efficiency depended on the sample volume. The color quenching effect was negligible. No radioactive liquid
waste was generated by this method. In addition, you can reuse the measured sample. 相似文献
7.
Target purification of Sα is carried out by distillation at 444±2 °C under N atmosphere and diluting the vapors in CS2. The solution is filtered through fiberglass, Teflon and cellulose to obtain Sα by CS2 evaporation. Once 30 g of this target are irradiated with fast neutron fluxes from 4.5 to 7.4·1012 n·cm−2s−1 from 6 to 12 hours, the nuclear reaction 32S(n,p)32P takes place. So, the irradiated Sα sample is placed in a Pyrex container situated inside a furnace as the most important piece of equipment in one aluminum
and Lucite glove box. The distillation of irradiated sulfur takes place at 444±2 °C under N atmosphere during 1–2 hours. The
vapors are connected to a sulfur diluter containing 20% CS2 aqueous solution, followed by an activated carbon filter and the two similar additional sulfur diluters. Once cooled, the
distillation chamber keeps the radioactive, carrier-free 32P stuck to the wall. Then 25–50 ml of 0.1N HCl acid was injected by suction and heated again at 110±2 °C during 1 hour. The
corresponding chemical reaction takes place and the labeled H3
32PO4 solution is produced. In such a way, industrial production of 32P labeled molecules has started in Mexico, with an initial production of 3700–5550 MBq per week. 相似文献
8.
J. L. Martínez Vidal P. Parrilla Vázquez J. Martínez Fernández 《Chromatographia》2000,51(3-4):187-192
Summary A sensitive and selective coupled-column liquid chromatography (LC-LC) method was developed for the trace level determination
of some N-methylcarbamates and some of their main metabolites as aldicarb, aldicarb-sulphoxide, aldicarb-sulphone, carbofuran
and 3-hydroxicarbofuran in drinking and ground waters. The limit of determination can be reduced to 0.1 μg.L−1 by solid phase extraction with a subsequent evaporation step. Environmental samples spiked at 0.1 μg.L−1 were preconcentrated off-line with graphite carbon and then analyzed by LC-LC with UV detection yielding average recoveries
between 81–109% (n=5) with RSD between 5–9%. The overall procedure allowed a sample throughput of up to 30 samples per day. 相似文献
9.
The measurements of electro-optical discharge characteristics and concentration of produced ozone were performed to evaluate
the efficiency of ozone production in an AC surface dielectric barrier discharge (SDBD) in pure oxygen at atmospheric pressure.
The discharge was driven in an amplitude-modulated regime with a driving AC frequency of 1 kHz, variable discharge duty cycle
of 0.01–0.8 and oxygen flow rate of 2.5–10 slm. We observed asymmetric SDBD behaviour as evidenced by the variation in the
ratio of the OI/O2
+ emission intensities registered during the positive/negative half-periods and complemented by the transferred charge measurements
through the Lissajous figures. We also found a strong dependence of O3 concentration on the discharge duty cycle. The highest calculated ozone production yield reached 170 g/kWh with a corresponding
energy cost of about 10 eV/molecule when combining the lowest inspected duty cycle with the lowest AC high voltage amplitude. 相似文献
10.
To enrich cosmogenic 7Be and 22Na, artificial 137Cs and natural radium isotopes, three chemical methods were applied to large volumes (100–300 l) of ground water from Daisen
Volcano, Japan. The co-precipitation method using BaSO4, Fe(OH)3 and AMP, yielded 7Be, 137Cs and radium isotope levels of nearly 100%. An ordinary ion-exchange column method, selectively recovered 22Na (77%) through two continuous column operations. 40K was satisfactorily removed in both, the co-precipitation and column methods. In addition, the simple batch method was suitable
for rapid treatment even on the slope of a volcano without sacrificing yields. Low-background γ-spectrometry combined with
these chemical treatments enabled the determination of extremely low-levels of 7Be, 22Na, 137Cs and radium isotopes (0.01–4 mBq/l) in ground water samples. The measurement of these nuclides of Daisen ground water provide
new information on the flow system of volcanic water, including residence time, the mixing of precipitation, and the aquifer’s
environment. 相似文献
11.
I. I. Zakharov O. I. Kolbasina T. N. Semenyuk I. V. Yudanov N. F. Tyupalo G. M. Zhidomirov 《Journal of Structural Chemistry》1994,35(2):176-181
The ab initio LCAO-MO-SCF method with the STO-3G basis set is employed to calculate the electronic structure of different
hydrated Fe2+ complexes. The general scheme of the interaction of ozone with Fe2+ (aq) is considered, whose first stage involves formation of an intermediate of the type of the ferryl ion FeO2+.
Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Ruberzhansk Branch of Dnepropetrovsk Chemical-Technological
Institute. Translated fromZhurnal Struktumoi Khimii, Vol. 35, No. 2, pp. 32–39, March–April, 1994.
Translated by O. Kharlamova 相似文献
12.
Bitao Su Ke Wang Jie Bai Hongmei Mu Yongchun Tong Shixiong Min Shixiong She Ziqiang Lei 《Frontiers of Chemistry in China》2007,2(4):364-368
Fe3+-doped TiO2 composite nanoparticles with different doping amounts were successfully synthesized using sol-gel method and characterized
by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultravioletvisible spectroscopy (UV-Vis) diffuse reflectance
spectra (DRS). The photocatalytic degradation of methylene blue was used as a model reaction to evaluate the photocatalytic
activity of Fe3+/TiO2 nanoparticles under visible light irradiation. The influence of doping amount of Fe3+ (ω: 0.00%–3.00%) on photocatalytic activities of TiO2 was investigated. Results show that the size of Fe3+/TiO2 particles decreases with the increase of the amount of Fe3+ and their absorption spectra are broaden and absorption intensities are also increased. Doping Fe3+ can control the conversion of TiO2 from anatase to rutile. The doping amount of Fe3+ remarkably affects the activity of the catalyst, and the optimum efficiency occurs at about the doping amount of 0.3%. The
appropriate doping of Fe3+ can markedly increase the catalytic activity of TiO2 under visible light irradiation.
__________
Translated from Journal of Northwest Normal University (Natural Science), 2006, 42(6): 55–56 [译自: 西北师范大学学报(自然科学版)] 相似文献
13.
Petisco C García-Criado B Mediavilla S Vázquez de Aldana BR Zabalgogeazcoa I García-Ciudad A 《Analytical and bioanalytical chemistry》2006,386(6):1823-1833
Near-infrared reflectance spectroscopy (NIRS) was used to estimate N, neutral detergent fibre (NDF), acid detergent fibre
(ADF), lignin and cellulose contents in leaves of a heterogeneous group of 17 woody species from the Central Western region
of the Iberian Peninsula. The sample set consisted of 182 samples of leaves of deciduous and evergreen species, showing a
wide range of concentrations determined by reference methods: 6.60–35.2 g kg−1 (N), 15.5–66.0% (NDF), 10.2–57.3% (ADF), 3.45–27.4% (lignin) and 5.79–31.3% (cellulose). Reflectance spectra, obtained for
samples of dried and ground leaves, were recorded as log1/R (R=reflectance) from 1,100 to 2,500 nm. NIRS calibrations were developed using multiple linear (MLR) and partial least-squares
(PLSR) regressions, and tested by external validation. Spectral data were transformed to the first and second derivative (1D,
2D). The PLSR method and derivative transformations provided the best statistics and showed lower standard errors of calibration
(SEC) and higher coefficients of multiple determination (R
2). In the external validation the standard errors of prediction (SEP) were 0.76 g kg−1 (N), 2.11% (NDF), 1.47% (ADF), 0.85% (lignin) and 0.86% (cellulose). The results obtained show that NIRS is very effective
for the estimation of these organic constituents in leaf tissue of woody species. This technique can be used in ecological
or ecophysiological studies as an alternative to the more time-consuming standard methods. 相似文献
14.
Summary A new method for the simultaneous identification and quantification of base/neutral and acidic pesticides at a low nanogram
per liter concentration level in natural waters is presented. The method includes enrichment of the compounds by solid phase
extraction on graphitized carbon black, followed by sequential elution of the base/neutral and acidic pesticides. Identification
and quantification of the compounds is performed with HPLC-ESI-MS. This procedure involves passing 1 L of ground water and
2 L of drinking water samples through a 0.5 g graphitized carbon black (GCB) extraction cartridge. A conventional 4.6-mm-i.d.
reversed phase LC C-18 operating with a 1 mL min−1 flow of the mobile phase was used to chromatograph the analytes. A flow of 100 μL min−1 of the column effluent was diverted to the ESI source. The ESI source was operated in positive ion mode for base/neutral
pesticides and in negative-ion mode for acid pesticides. For the analyte considered, the response of the mass detector was
linearly related to the amount of the analytes injected between 5 and 250 ng. In all cases, recoveries of the analytes were
better than 90%. The limit of detection (signal-to-noise ratio=3) of the method for the pesticides considered in drinking
water samples was estimated to be about 3–10 ng L−1. 相似文献
15.
Sz. Osváth N. Vajda Zs. Molnár É. Széles Zs. Stefánka 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(3):675-680
The majority of long-lived radionuclides produced in the nuclear fuel cycle can be regarded as “difficult-to-measure” nuclides,
hence chemical separation is needed before the nuclear measurement of them. A combined radiochemical procedure that enables
the simultaneous determination of some “difficult-to-measure” nuclides in medium and low level radioactive wastes has been
developed in our laboratory. Recently, this method has been extended for determination of 237Np and 93Zr. 237Np and 93Zr are pre-concentrated by co-precipitation on iron(II) hydroxide and zirconium oxide, separated by extraction chromatography
using UTEVA, and measured by inductively coupled plasma mass spectrometry (ICP-MS). As even traces of polyatomic ions and
isotopes at m/z 237 or 93 cause considerable interferences during ICP-MS detection, a purification step by extraction chromatography
was needed. Analyzing real samples (evaporation concentrates of a nuclear power plant) 66–99% and 31–99% chemical yields were
achieved for Np and Zr, respectively. 相似文献
16.
A novel method combining matrix solid phase dispersion (MSPD) with Soxhlet simultaneous extraction clean-up (SSEC) was developed.
Being a single-step extraction and clean-up procedure, it could be used instead of multistep solvent extraction and Florisol
column clean-up. It not only reduces sample contamination during the procedure, but it also decreases the amount of organic
solvent needed. The retention times of standards were used to qualitatively assess the method, and the external standard method
was used to quantitatively assess it. Residues of organochlorine pesticides (OCP) in tobaccos were determined by gas chromatography–electron
capture detection (GC–ECD), and their identities were confirmed by the standard addition method (SAM). The performance of
the method was evaluated and validated: the detection limit was 0.01–0.02 μg g−1, relative standard deviations were 5–26%, and recoveries were 72–99% at fortification levels of 0.10, 1.00 and 10.0 μg g−1. The analytical characteristics of MSPD–SSEC compared very favorably with the results from the classical multistep solvent
extraction and Florisol column clean-up method. 相似文献
17.
A method for separation and quantitative determination of the iodosulfuron-methyl-sodium in water samples by high-performance
liquid chromatography (HPLC) was developed and in-house validated in order to demonstrate its performance for monitoring of
heterogeneous photocatalytic elimination of the herbicide iodosulfuron-methyl-sodium from water. Surface and ground water
samples were used to demonstrate its selectivity, detection and quantification limits, linearity, trueness and precision.
In addition, stability of iodosulfuron-methyl-sodium was studied in function of temperature and time. Method accuracy was
quantified through measurement uncertainty estimate based on method validation data. The paper gives practical and easy to
follow guidance on how uncertainty estimates can be obtained from method validation experiments. It shows that, if properly
planned and executed, key precision and trueness studies undertaken for validation purposes can also provide much of the data
needed to produce an estimate of measurement uncertainty. Our analytical protocol allowed us to quantify iodosulfuron-methyl-sodium
in ground water and surface water in concentration level between 2.50–50.0 μmol L−1 with satisfactory recoveries (99–104%) and repeatability lower or equal than 0.3% for all the matrices. We also estimated
within-laboratory reproducibility over 3-month period, which was 0.7%. We proved that the method was selective for determination
of iodosulfuron-methyl-sodium in the relevant matrices. Measurement uncertainty of results was evaluated to be 4.0% with 95%
confidence level. After validation and measurement uncertainty evaluation steps, results obtained showed that the method can
be applied to efficiently monitor heterogenous photocatalytic degradation of the herbicide iodosulfuron-methyl-sodium. 相似文献
18.
An approach for rapid quantitation of 5-hydroxymethylfurfural (HMF) in honey using planar chromatography is suggested for
the first time. In high-performance thin-layer chromatography (HPTLC) the migration time is approximately 5 min. Detection
is performed by absorbance measurement at 290 nm. Polynomial calibration in the matrix over a range of 1:80 showed correlation
coefficients, r, of ≥ 0.9997 for peak areas and ≥ 0.9996 for peak heights. Repeatability in the matrix confirmed the suitability of HPTLC–UV
for quantitation of HMF in honey. The relative standard deviation (RSD, %, n = 6) of HMF at 10 ng/band was 2.9% (peak height) and 5.2% (peak area); it was 0.6% and 1.0%, respectively, at 100 ng/band.
Other possible detection modes, for example fluorescence measurement after post-chromatographic derivatization and mass spectrometric
detection, were also evaluated and can coupling can be used as an additional tool when it is necessary to confirm the results
of prior quantitation by HPTLC–UV. The confirmation is provided by monitoring the HMF sodium adduct [M + Na]+ at m/z 149 followed by quantitation in TIC or SIM mode. Detection limits for HPTLC–UV, HPTLC–MS (TIC), and HPTLC–MS (SIM) were 0.8 ng/band,
4 ng/band, and 0.9 ng/band, respectively. If 12 μL honey solution was applied to an HPTLC plate, the respective detection
limits for HMF in honey corresponded to 0.6 mg kg−1. Thus, the developed method was highly suitable for quantitation of HMF in honey at the strictest regulated level of 15 mg kg−1. Comparison of HPTLC–UV detection with HPTLC–MS showed findings were comparable, with a mean deviation of 5.1 mg kg−1 for quantitation in SIM mode and 6.1 mg kg−1 for quantitation in TIC mode. The mean deviation of the HPTLC method compared with the HPLC method was 0.9 mg kg-1 HMF in honey. Re-evaluation of the same HPTLC plate after one month showed a deviation of 0.5 mg kg−1 HMF in honey. It was demonstrated that the proposed HPTLC method is an effective method for HMF quantitation in honey.
相似文献
19.
M. C. Yebra M. F. Enríquez A. García A. Moreno-Cid 《Analytical and bioanalytical chemistry》2001,370(1):64-68
A minicolumn packed with poly(aminophosphonic acid) chelating resin incorporated in an on-line preconcentration system for
flame atomic-absorption spectrometry was used to determine ultratrace amounts of lead in mussel samples at μg L–1 level. The preconcentrated lead was eluted with hydrochloric acid and injected directly into the nebulizer for atomization
in an air-acetylene flame for measurement. The performance characteristics of the determination of lead were: preconcentration
factor 26.8 for 1 min preconcentration time, detection limit (3σ) in the sample digest was 0.25 μg g–1 (dry weight) for a sample volume of 3.5 mL and 0.2 g sample (preconcentration time 1 min), precision (RSD) 2.3% for 25 μg
L–1 and 2.0% for 50 μg L–1. The sampling frequency was 45 h–1. The method was highly tolerant of interferences, and the results obtained for the determination of lead in a reference material
testify to the applicability of the proposed procedure to the determination of lead at ultratrace level in biological materials
such as mussel samples.
Received: 1 November 2000 / Revised: 8 January 2001/ Accepted: 11 January 2001 相似文献
20.
Enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase (HRP)-catalyzed fluorescent reaction, and oxalate chemiluminescence
imaging analysis have been combined to develop a sensitive, simple, and rapid method for analysis of interferon alpha (α-IFN)
in human serum samples. A typical “sandwich type” immunoassay was used. Reaction of o-phenylenediamine (OPD) with hydrogen peroxide (H2O2), catalyzed by HRP, produced 2,3-diaminophenazine (PDA), which was detected by chemiluminescence imaging analysis with the
bis(2,4,6-trichlorophenyl)oxalate (TCPO)–H2O2–glyoxaline–PDA chemiluminescent system. The TCPO chemiluminescent imaging system is more sensitive and the chemiluminescence
quantum yield is at least five times higher than for the luminol–H2O2–HRP–PIP (p-iodophenol) chemiluminescent imaging system. The results showed there was a very good linear correlation between response
and amount of α-IFN in the range 1.3–156.0 pg mL−1 (R = 0.9991) and the detection limit was 0.8 pg mL−1 (S/N=3). The relative standard deviation (n = 9) was 4.7%. The proposed method has been used for successful analysis of the amount of α-IFN in human serum. The results
obtained compared well with those obtained by conventional colorimetric ELISA and luminol chemiluminescent ELISA.
Figure Procedures of the proposed method 相似文献