共查询到20条相似文献,搜索用时 46 毫秒
1.
Tomás Pérez-Ruiz Carmen Martínez-Lozano Virginia Tomás Antonio Sanz Jesús Martín 《Fresenius' Journal of Analytical Chemistry》1998,362(4):399-403
A flow-injection configuration is proposed for the fluorimetric determination of ethylenethiourea. The procedure is based
on the inhibitory effect of ethylenethiourea on the oxidation of thiamine to thiochrome by mercury(II). A linear calibration
graph was obtained between 0.1 and 2.0 μg mL–1, with a sampling rate of 40 samples per hour and a relative standard deviation of about 1.11%. The usefulness of the method
was tested for the determination of ethylenethiourea residues in water, milk, potatoes, pear, grape and apple.
Received: 26 January 1998 / Revised: 6 April 1998 / Accepted: 9 April 1998 相似文献
2.
Tomás Pérez-Ruiz Carmen Martínez-Lozano Virginia Tomás Antonio Sanz Jesús Martín 《Analytical and bioanalytical chemistry》1998,362(4):399-403
A flow-injection configuration is proposed for the fluorimetric determination of ethylenethiourea. The procedure is based
on the inhibitory effect of ethylenethiourea on the oxidation of thiamine to thiochrome by mercury(II). A linear calibration
graph was obtained between 0.1 and 2.0 μg mL–1, with a sampling rate of 40 samples per hour and a relative standard deviation of about 1.11%. The usefulness of the method
was tested for the determination of ethylenethiourea residues in water, milk, potatoes, pear, grape and apple.
Received: 26 January 1998 / Revised: 6 April 1998 / Accepted: 9 April 1998 相似文献
3.
A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane
electrode without added ion-exchanger is described. A solution of a derivative of tetraphenylborate is used as titrant. The
method is based on the ion association between an excess of 2-aminoperimidinium added to the sulfate containing sample and
the tetraphenylborate derivative in the titrant. The titration end-point is detected as a sharp potential change due to an
increase in the concentration of the free tetraphenylborate derivative at the equivalence point. The sharpness of the titration
curve at the end-point is compared for two tetraphenylborate derivatives. Good results are obtained with a solution of sodium
tetrakis (4-fluorophenyl) borate.
Received: 9 March 1998 / Revised: 21 April 1998 / Accepted: 25 April 1998 相似文献
4.
Preconcentration and separation of Ni, Pb and Cd have been investigated using the metalfix chelamine resin prior to inductively
coupled plasma – atomic emission spectrometry (ICP-AES) under various experimental conditions. The recoveries of the analytes
obtained with 95% confidence level were 92 ± 1% for Ni, 100 ± 4% for Pb and 93 ± 3% for Cd.
Received: 5 February 1998 / Revised: 30 April 1998 / Accepted: 12 June 1998 相似文献
5.
Recent developments in quantitative surface analysis by Auger (AES) and x-ray photoelectron (XPS) spectroscopies are reviewed and problems relating to a more accurate quantitative interpretation of AES/XPS experimental data are discussed. Special attention is paid to consideration of elementary physical processes involved and influence of multiple scattering effects on signal line intensities. In particular, the major features of core-shell ionization by electron impact, Auger transitions and photoionization are considered qualitatively and rigorous approaches used to calculate the respective transition probabilities are analysed. It is shown that, in amorphous and polycrystalline targets, incoherent scattering of primary and signal Auger and photoelectrons can be described by solving analytically a kinetic equation with appropriate boundary conditions. The analytical results for the angular and energy distribution, the mean escape depth, and the escape probability as a function of depth of origin of signal electrons as well as that for the backscattering factor in AES are in good agreement with the corresponding Mote Carlo simulation data. Methods for inelastic background subtraction, surface composition determination and depth-profile reconstructions by angle-resolved AES/XPS are discussed. Examples of novel techniques based on x-ray induced photoemission are considered. 相似文献
6.
Gerald Remberg Pat Sandra Wolfgang Nyiry Norbert Winker A. Nikiforov 《Fresenius' Journal of Analytical Chemistry》1998,362(4):404-408
The distribution of the 8557 theoretically possible structures of polychlorinated terphenyls (PCT) over the different degrees
of chlorination and basic terphenyl backbones has been calculated and is presented in detail. As congeners missing chlorine
atoms in an ortho position are suspected to be as noxious to organisms as dioxins, the number of these congeners is specified
as well. The gas chromatographic retention behavior of 14 PCT single standards is studied on four stationary liquid phases
for capillary columns (HP-Ultra 1, HP-5MS, RSL-300 and Polycarbonate) relative to 2,2′,3,4,4′,5,5′-heptachlorobiphenyl and
shows no consequent separation of PCT in terms of the degree of chlorination. Individual congeners have been assessed for
their suitability as internal standards in PCT analysis.
Received: 16 January 1998 / Revised: 3 April 1998 / Accepted: 7 April 1998 相似文献
7.
Wang CC Kornilov O Gessner O Kim JH Peterka DS Neumark DM 《The journal of physical chemistry. A》2008,112(39):9356-9365
Helium droplets doped with Xe and Kr atoms were photoionized by using VUV synchrotron radiation from the Advanced Light Source and the resulting photoelectron images were measured. A wide range of He droplet sizes, photon energies, and dopant pick-up conditions was investigated. Significant ionization of dopants was observed at 21.6 eV, the absorption maximum of 2p (1)P1 electronic excited state of He droplets, indicating an indirect ionization mechanism via excitation transfer. The photoelectron images and spectra reveal multiple photoionization mechanisms and pathways for the photoelectrons to escape the droplet. Specifically, they show sets of sharp peaks assigned to two mechanisms for Penning ionization of the dopant by He* in which the photoelectrons leave the droplet with no detectable energy loss, a broad, intense feature representing electrons that undergo significant energy loss, and a small amount of ultraslow electrons that may result from electron trapping at the droplet surface. The droplet-size dependence of the broad, intense feature suggests the development of the conduction band edge in the largest droplets seen here ((N) approximately 250,000). 相似文献
8.
This paper presents two different methods to enhance the stability of the bonding between thin polymer layers and glass substrates.
With these stabilised polymer layers the detection of hydrocarbons in waste waters using Reflectometric Interference Spectrometry
(RIfS) is possible. The sensors could be used between 30 and 60 days in continuous measurements. In calibration measurements
with regular fuel dissolved in deionised water, all sensors showed a linear correlation between the signal and the concentration
in the examined range from 0 to 50 mg/L. A detection limit of 1.95 mg/L regular gasoline in water (for RTV 3140 layers) could
be found. River water as matrix for regular fuel caused no changes in the response behaviour of the sensors, only an off-set
value occurred. Even raw aqueous phases from industrial interceptors could be investigated without any pre-treatment.
Received: 13 February 1998 / Revised: 14 April 1998 / Accepted: 18 April 1998 相似文献
9.
E. A. H. Timmermans I. A. J. Thomas J. Jonkers E. Hartgers J. A. M. van der Mullen D. C. Schram 《Fresenius' Journal of Analytical Chemistry》1998,362(5):440-446
The effect of introducing molecular compounds into argon plasmas has been studied using an expanding microwave induced plasma
at atmospheric pressure. Besides the use of optical emission spectroscopy (OES), also the time dependent behavior of line
intensities during power interruptions has been studied. From the measurements it is found that even an injection of small
amounts of molecular compounds (> 0.5%) leads to important changes in excitation mechanisms in the plasma. It is also found
that in the recombination zone downstream in the plasma an excitation mechanism which is independent of the electron density,
e.g. excitation transfer from metastables or Penning ionization, must be responsible for the excitation of analytes.
Received: 12 February 1998 / Revised: 14 April 1998 / Accepted: 17 April 1998 相似文献
10.
E. A. H. Timmermans I. A. J. Thomas J. Jonkers E. Hartgers J. A. M. van der Mullen D. C. Schram 《Analytical and bioanalytical chemistry》1998,362(5):440-446
The effect of introducing molecular compounds into argon plasmas has been studied using an expanding microwave induced plasma
at atmospheric pressure. Besides the use of optical emission spectroscopy (OES), also the time dependent behavior of line
intensities during power interruptions has been studied. From the measurements it is found that even an injection of small
amounts of molecular compounds (> 0.5%) leads to important changes in excitation mechanisms in the plasma. It is also found
that in the recombination zone downstream in the plasma an excitation mechanism which is independent of the electron density,
e.g. excitation transfer from metastables or Penning ionization, must be responsible for the excitation of analytes.
Received: 12 February 1998 / Revised: 14 April 1998 / Accepted: 17 April 1998 相似文献
11.
Qing-Zhi Zhu Feng-Hua Liu J.-G. Xu Wen-Jin Su Jian-Wei Huang 《Fresenius' Journal of Analytical Chemistry》1998,362(6):537-540
A novel mimetic enzyme immunoassay to determine α-1-fetoprotein (AFP) in solution was developed. Hemin, a horseradish peroxidase
substitute, was used as a labelling reagent to catalyze the reaction of p-hydroxyphenylacetic (HPA) and hydrogen peroxide
in alkaline media. In the competitive immunoassay, monoclonal anti-AFP antibody was coated on a 96-well plate (polystyrene)
and a constant amount of hemin-labelled AFP and a known volume of test solution were added. Non-labelled and hemin-labelled
AFP compete for binding to the plate-bound antibody. After the immunoreaction, the immunochemically adsorbed hemin-AFP conjugate
moiety was determined by measuring the fluorescence produced in a solution containing HPA and hydrogen peroxide. The calibration
graph for AFP was linear over the range 0 ∼ 380 ng/ well with a detection limit of 1.0 ng/well. The method has been applied
to determine the AFP in human blood serum with satisfactory results.
Received: 21 January 1998 / Revised: 1 April 1998 / Accepted: 4 April 1998 相似文献
12.
V.V. Grechov 《Chemical physics letters》1983,96(2):237-242
It has been shown that the real escape depth L of low-energy (? 2 eV) electrons determined in homogeneous tetracene films (obtained by vacuum evaporation on cooled substrate at 120 K) does not exceed 6–10 A. For such small L values photoemission should be considered as essentially a surface phenomenon since the energy distribution of emitted photoelectrons substantially depends on energetic and structural peculiarities of the near-surface molecules of the crystal. 相似文献
13.
A flow injection system with spectrophotometric detection is proposed for the determination of low levels of nitrite based
on its catalytic effect on the oxidation of gallocyanine by bromate in acidic media. Various analytical parameters such as
acidity, reagent concentration, flow rate, sample size, time, temperature, and interfering species were studied. The calibration
graph was linear for 0.020–0.500 μg/mL of nitrite. The method is successfully applied to food samples. Up to 30 ± 5 samples
can be analyzed per hour.
Received: 8 April 1998 / Revised: 3 June 1998 / Accepted: 31 July 1998 相似文献
14.
Ultra-trace analysis of nitrite in food samples by flow injection with spectrophotometric detection 总被引:2,自引:0,他引:2
A flow injection system with spectrophotometric detection is proposed for the determination of low levels of nitrite based
on its catalytic effect on the oxidation of gallocyanine by bromate in acidic media. Various analytical parameters such as
acidity, reagent concentration, flow rate, sample size, time, temperature, and interfering species were studied. The calibration
graph was linear for 0.020–0.500 μg/mL of nitrite. The method is successfully applied to food samples. Up to 30 ± 5 samples
can be analyzed per hour.
Received: 8 April 1998 / Revised: 3 June 1998 / Accepted: 31 July 1998 相似文献
15.
F. Jüttner 《Fresenius' Journal of Analytical Chemistry》1999,363(1):128-129
Two widely accepted indophenol-type reactions with ammonium, which use phenol/hypochlorite and salicylate/dichloroisocyanurate
as reagents, were compared for possible interferences with other naturally occurring nitrogen-containing compounds. Unlike
the first method, the second showed strong interference from all amino acids and peptides tested. As much as 57 mole % of
threonine and 49 mole % of serine were degraded to ammonium. Pyrimidines, purines, nucleosides and urea were negative in both
reactions. The wide distribution and importance of free and combined amino acids in naturally occurring waters favours the
application of the classical phenol/ hypochlorite reaction with ammonium rather than the modified salicylate/dichloroisocyanurate
reaction.
Received: 20 April 1998 / Revised: 28 May 1998 / Accepted: 5 Juni 1998 相似文献
16.
K. Wagner W. Görner M. Hedrich P. Jost C. Segebade 《Analytical and bioanalytical chemistry》1998,362(4):382-386
The analysis of halogens in various matrices is described. Activation analysis with mainly high energy bremsstrahlung (PAA)
and pile neutrons (NAA) was applied. In the case of chlorine, fast procedures were worked out requiring not more than 100
min for one determination. The particular problems of fluorine analysis are discussed. The described techniques were applied
for the following cases: Determination of total chlorine resp. bromine in oil samples; determination of chlorine in wood,
glasses and TiN powders; determination of iodine in ZnSe single crystals using instrumental photoactivation.The limits of
detection are: (interference-free in μg/g) F: 0.03/–; Cl: 0.1/0.05; Br: 0.04/0.003 and I: 0.1/0.01 using PAA/NAA. Activation
analysis, being independent upon the chemical status of the analyte and usually less affected by blank problems has been found
to be a useful complement to conventional chemical analysis.
Received: 28 February 199 / Revised: 14 April 1998 / Accepted: 18 April 1998 相似文献
17.
K. Wagner W. G?rner M. Hedrich P. Jost C. Segebade 《Fresenius' Journal of Analytical Chemistry》1998,362(4):382-386
The analysis of halogens in various matrices is described. Activation analysis with mainly high energy bremsstrahlung (PAA)
and pile neutrons (NAA) was applied. In the case of chlorine, fast procedures were worked out requiring not more than 100
min for one determination. The particular problems of fluorine analysis are discussed. The described techniques were applied
for the following cases: Determination of total chlorine resp. bromine in oil samples; determination of chlorine in wood,
glasses and TiN powders; determination of iodine in ZnSe single crystals using instrumental photoactivation.The limits of
detection are: (interference-free in μg/g) F: 0.03/–; Cl: 0.1/0.05; Br: 0.04/0.003 and I: 0.1/0.01 using PAA/NAA. Activation
analysis, being independent upon the chemical status of the analyte and usually less affected by blank problems has been found
to be a useful complement to conventional chemical analysis.
Received: 28 February 199 / Revised: 14 April 1998 / Accepted: 18 April 1998 相似文献
18.
Jian Huang Xingguo Chen Zhide Hu Zhengfeng Zhao Martin Hooper 《Fresenius' Journal of Analytical Chemistry》1999,363(1):117-118
A flow injection method was developed for the determination of palladium, based on the reaction of palladium with DBOK-chlorophosphonazo
with a detection limit of 0.07 μg/mL and a linear calibration range from 0.1 to 3.2 μg/mL of palladium. The reaction product
has a maximum absorption at 630 nm. The method was applied to determine Pd2+ in catalysts and in anode mud samples. The relative error is less than 3% and the recovery of palladium is in the range 95%
to 105%
Received: 27 April 1998 / Revised: 24 August 1998 / Accepted: 26 August 1998 相似文献
19.
Jian Huang Xingguo Chen Zhide Hu Zhengfeng Zhao Martin Hooper 《Analytical and bioanalytical chemistry》1999,363(1):117-118
A flow injection method was developed for the determination of palladium, based on the reaction of palladium with DBOK-chlorophosphonazo
with a detection limit of 0.07 μg/mL and a linear calibration range from 0.1 to 3.2 μg/mL of palladium. The reaction product
has a maximum absorption at 630 nm. The method was applied to determine Pd2+ in catalysts and in anode mud samples. The relative error is less than 3% and the recovery of palladium is in the range 95%
to 105%
Received: 27 April 1998 / Revised: 24 August 1998 / Accepted: 26 August 1998 相似文献
20.
H. Rameb?ck Y. Albinsson M. Sk?lberg U. B. Eklund 《Fresenius' Journal of Analytical Chemistry》1998,362(4):391-394
A method was developed for the determination of 99Tc at low concentrations in clay samples. The chemical treatment of the samples prior to chemical separation and analysis
comprised leaching with sulphuric acid/ sodium bromate. After leaching, pertechnetate was extracted with Alamine-336/chloroform
and then back-extracted into nitric acid. Detection was carried out using inductively coupled plasma mass spectrometry, ICP-MS.
The instrumental detection limit was 0.45 pg/mL, which corresponds to 0.28 mBq/mL. With the use of a desolvating nebuliser,
the detection limit was lowered by about a factor of five. The results were compared with a method using radiometric detection.
Received: 16 April 1998 / Revised: 12 June 1998 / Accepted: 16 June 1998 相似文献