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1.
Jadwiga Opydo 《Mikrochimica acta》2001,137(3-4):157-162
Necessary conditions were established for simultaneous nickel and cobalt determination in environmental samples, such as
oak wood and soil, based on cathodic adsorptive stripping voltammetry. Ni(II) and Co(II), complexed with dimethylglyoxime,
were determined using a hanging mercury drop electrode. Optimum conditions were found to be: accumulation time 90 s, accumulation
potential −0.80 V vs. SCE, supporting electrolyte 0.2 mol dm−3 ammonia-ammonium chloride buffer (pH = 9.4) + 0.05 mol dm−3 NaNO2 and dimethylglyoxime 2 × 10−4 mol dm−3. A linear current-concentration relationship was observed up to 7.51×10 −7 mol dm−3 for Ni(II) and 7.0 × 10−7 mol dm−3 for Co(II). Excess amounts of zinc(II) interfering with cobalt peaks were masked by complexation with EDTA. Wood and soils
were mineralized by applying a microwave digestion system, using the mixtures H2O2 + HNO3 or HNO3 + HF, respectively. The developed procedure was tested by analysing international reference materials (BCR 62 Olive Leaves
and GBW 08302 Tibet Soil). The developed procedure was used to determine pollution of oak stand with nickel and cobalt in
different regions of Poland.
Received August 10, 2000. Revision May 22, 2001. 相似文献
2.
M. F. Butman D. N. Sergeev V. B. Motalov L. S. Kudin A. S. Kryuchkov K. W. Krämer 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(6):922-925
A procedure for determining the formation enthalpies of LnX
n
(n = 1–3) molecules of thermally unstable lanthanide di- and trihalides that is based on measuring the equilibrium constants
of reactions in Ln-X systems of various content and solving a system of thermochemical equations is suggested. The procedure
is used to determine the enthalpies of formation Δf
H
298o of molecules and negative ions found in the vapors of ytterbium bromides: YbBr (20 ± 3), YbBr2 (−135 ± 10), YbBr3 (−233 ± 12), YbBr3− (−615 ± 31), and YbBr4− (−766 ± 23) kJ/mol. 相似文献
3.
A new Schiff-base ligand [N, N′, N″-Tri- (2,4-dihydroxyacetophenone) – triaminotriethylamine (TDATA)] with a tripodal structure
was synthesized. Its fluorescence intensity with the europium(III) complex was increased about 178-fold in the presence of
sodium acetate (NaAc) and about 126-fold in the presence of sodium phosphate (Na3PO4) solution. After adding the organic solvent dimethylsulfoxide (DMSO) to the above system, which leads to Eu3+ the fluorescence was further enhanced about 12-fold. Spectrofluorimetric determination of trace amounts of Eu3+ based on the phenomenon was performed. The excitation and emission wavelength is 365 nm and 615 nm, respectively. Under optimum
conditions, the fluorescence intensities vary linearly with the concentration of Eu3+ in the range of 4.9 × 10−12–3.2 × 10−6 mol · L−1 with a detection limit of 4.5 × 10−12 mol · L−1 (for the TDATA-NaAc-DMSO system) or 6.2 × 10−11–8.6 × 10−6 mol · L−1 with a detection limit of 6.0 × 10−11 mol · L−1 (for the TDATA-Na3PO4-DMSO system). Interferences of some rare earth metals and other inorganic ions are described. The method is a selective,
sensitive, rapid and simple analytical procedure for the determination of europium(III) in a high purity yttrium oxide and
synthetic sample. The mechanism for the fluorescence enhancement is also discussed. 相似文献
4.
X. Y. Feng X. P. Geng J. J. Peng H. Y. Hou Q. Bai 《Journal of Thermal Analysis and Calorimetry》2010,102(2):799-807
The displacement adsorption enthalpies (ΔH) of denatured α-Amylase (by 1.8 mol L−1 GuHCl) adsorbed onto a moderately hydrophobic surface (PEG-600, the end-group of polyethylene glycol) from solutions (x mol L−1 (NH4)2SO4, 0.05 mol L−1 KH2PO4, pH 7.0) at 298 K are determined by microcalorimeter. Further, entropies (ΔS), Gibbs free energies (ΔG) and the fractions of ΔH, ΔS, and ΔG for net adsorption of protein and net desorption of water are calculated in combination with adsorption isotherms of α-Amylase
based on the stoichiometric displacement theory for adsorption (SDT-A) and its thermodynamics. It is found that the displacement
adsorptions of denatured α-Amylase onto PEG-600 surface are exothermic and enthalpy driven processes, and the processes of
protein adsorption are accompanied with the hydration by which hydrogen bond form between the adsorbed protein molecules favor
formation of β-sheet and β-turn structures. The Fourier transformation infrared spectroscopy (FTIR) analysis shows that the
contents of ordered secondary structures of adsorbed α-Amylase increase with surface coverages and salt concentrations increment. 相似文献
5.
M. W. McElfresh J. C. Meeks N. J. Parks 《Journal of Radioanalytical and Nuclear Chemistry》1979,53(1-2):337-344
An improvement in a method for the synthesis of13NO
2
−
from13NO
3
−
with specific activity>30 mCi/mL and radiochemical purity>99% is described.13NO
3
−
is produced by the16O(p, α)13N reaction using a recirculating water target and 20 MeV protons.13NO
2
−
is synthesized by reduction of13NO
3
−
in a cadmium-copper column. Contaminating13NH
4
+
is removed by rotatory evaporation at pH>11.0. The synthetic procedure takes less than 20 minutes from collection of irradiated
target water to sterilization of the radiopharmaceutical. 相似文献
6.
In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide
was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis,
a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the
determination of carbonate with a wide linear range of 1.0 × 10−10–5.0 × 10−6 mol L−1 and a low detection limit (S/N = 3) of carbonate of 1.2 × 10−11 mol L−1. The average relative standard deviation for 1.0 × 10−9–9.0 × 10−7 mol L−1 of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination
of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 × 10−6–6.0 × 10−2 mg L−1 and 0.08–30 mg L−1 carbon, respectively. Recoveries of 97.4–106.4% for TIC and 96.0–98.5% for TOC were obtained by adding 5 or 50 mg L−1 of carbon to the water samples. The relative standard deviations (RSDs) were 2.6–4.8% for TIC and 4.6–6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy
transfer from luminol to uranine was proposed.
Figure Chemiluminescence profiles in batch system. 1, Injection of 100 μL of K2CO3 into 1.0 mL luminol-1.0 mL H2O2 solution; 2-3 and 4-5, Injection in sequence of 100 μL of K2CO3 and 100 μL of uranine into 1.0 ml luminol-1.0 mL H2O2 solution; Cluminol = 1.0 × 10−7 mol/L, CH2O2 = 1.0 × 10−5 mol/L, Curanine = 1.0 × 10−5 mol/L, CK2CO3 = 1.0 × 10−7 mol/L except for 4-5 where CK2CO3 = 1.0 × 10−4 mol/L 相似文献
7.
Thato N. Mtshali Walter Purcell Hendrik G. Visser Steven S. Basson 《Transition Metal Chemistry》2008,33(4):481-491
The kinetics of the reaction between [ReN(H2O)-(CN)4]2− with different κ2
N,O-donor ligands (quin− and 2,3-dipic−, respectively) have been studied in the pH 4–12 range in aqueous solution. Two consecutive reaction steps with the formation
of the [ReN(η1-quin)(CN)4]3− and [ReN(μ2-quin) (CN)3]2− complexes, respectively, were spectrophotometrically observed and kinetically investigated. The same reaction mechanism is
proposed for these two ligands. The first fast reaction (for quin−) is attributed to the aqua substitution of [ReN(H2O)(CN)4]2− with forward and reverse rate constants of 1.96(5) × 10−1 M−1 s−1 and 5.6(3) × 10−2 s−1, while a rate of 2.64(3) M−1 s−1 was observed for the reaction between the conjugate base [ReN(OH)(CN)4]3− and quin− at 40.2 °C. Due to small absorbance changes, it was difficult to obtain any good quality data for the fast reactions for
2,3-dipic−. The second, slower reaction is attributed to cyano substitution with rate constants (k
3
K
1) of 4.17(4) × 10−3 for quin− and 4.68(7) × 10−3 M−1 s−1 for 2,3-dipic−, at 80.02 °C, respectively. The acid dissociation constant for the aqua complex was spectrophotometrically determined as
11.58(3) and 11.54(2) and kinetically as 11.51(8) and 11.41(1), at 80.4 °C, respectively. Negative values of −83.5(2) and −144.1(2) J K−1 mol−1 as well as the of 71.4(3) and 47.3(3) kJ mol−1, for the slow quin− and 2,3-dipic− reactions, respectively, point to an ordered transition state where bond formation is responsible for the major driving force
of the reaction. The and for the fast forward reaction of quin− is indicative of expected associative activation in the transition state.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Puspalata Rajesh G. R. Dey D. B. Naik K. Kishore 《Research on Chemical Intermediates》2008,34(1):53-65
Reactions of 2- and 3-nitro anilines (2- and 3-NA) with eaq−, H-atoms and one-electron reductants have been studied using pulse radiolysis in aqueous solutions. Reactions of eaq− were found to be quite fast with both 2-NA and 3-NA resulting in their corresponding semi-reduced species which are reducing
in nature. Reduction potentials for 2-NA/2-Na•′ have been estimated to be approx. −0.56 Vvs. NHE and that for 3-NA/3-NA•− was found to be between −0.185 V and −0.45 Vvs. NHE. Semi-reduced 2-NA has main absorption peak at 300 nm with a shoulder in the 350 nm region and a broad weak band in
the 470–500 nm region, whereas semi-reduced 3-NA possesses an absorption peak at 520 nm. Reducing radicals such as (CH3)2 C•OH and CO2•− reacted with 2-NA, producing semi-reduced species, whereas reactions of these radicals with 3-NA produced their corresponding
radical-adduct species. 相似文献
9.
The phenyl substituted acridine-1,8-dione (AD) dye reacts with (CH3)2*COH radicals with a bimolecular rate constant of 0.6 × 108 dm3 mol−1 s−1 in acidic aqueous-organic mixed solvent system. The transient optical absorption band (λmax = 465 nm, ɛ = 6.8 × 102 dm3 mol−1 cm−1) is assigned to ADH* formed on protonation of the radical anion. In basic solutions, (CH3)2*COH radicals react with a bimolecular rate constant of 4.6 × 108 dm3 mol−1 s−1 and the transient optical absorption band (λmax = 490 nm, ɛ = 10.4 × 103 dm3 mol−1 cm−1) is assigned to radical anion, AD*−, which has a pKa value of 8.0. The reduction potential value of the AD/AD*− couple is estimated to be between −0.99 and −1.15 V vs NHE by pulse radiolysis studies. The cyclic voltammetric studies showed
the peak potential close to −1.2 V vs Ag/AgCl. 相似文献
10.
A simple, rapid and specific chemiluminescence (CL) method for the determination of glutathione has been developed. The method
is based on the enhanced CL of the reaction between Ru(phen)3
2+ (phen = 1,10-phenanthroline) and KMnO4 by glutathione in HCl medium. Under the optimum conditions, the response is linearly proportional to the concentration of
glutathione between 1.5 × 10−7 and 1.0 × 10−5 mol L−1. The dection limit for glutathione (5.8 × 10−8 mol L−1) is about 10 and 200 times better than those of the spectrophotometric method using Ellman regent and the Lucigenin – CL
method, respectively. The final procedure allows the determination of glutathione in human serum with recoveries of 92%–108%.
A satisfactory agreement was obtained with a mean relative difference of 2.5% compared to the HPLC method. 相似文献
11.
Highly selective poly(vinyl chloride) (PVC) membrane electrode based on N-salicylidene-benzylamineato copper(II) complexes
[Cu(SBA)2] as new carriers towards thiocyanate-selective electrode was reported. The influence of membrane composition, pH and possible
interfering anions were investigated on the response properties of the electrode. The resulting electrode exhibits anti-Hofmeister
selectivity sequence: SCN− > ClO4− > Sal− > I− > Br− > NO3− > NO2− > SO32− > H2PO4− > Cl− > SO42−, and a near-Nernstian potential linear range for thiocyanate from 1.0 × 10−1 to 9.0 × 10−7 M with a detection limit of 7.0 10−7 M and a slope of , over a wide pH range of 3.0–9.0 in phosphate buffer solution at 20°C. The proposed electrode has a fast response time of
about 5–10 s and can be used for at least 3 months without any considerable divergence in potential. The electrode was successfully
applied to the determination of thiocyanate in waste water and human urine and saliva samples.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 3, pp. 293–299.
The text was submitted by the authors in English. 相似文献
12.
Md. Nurul Amin Satoshi Kaneco Yukitake Nakano Hideyuki Katsumata Tohru Suzuki Kiyohisa Ohta 《Mikrochimica acta》2008,161(1-2):73-79
A multi-pumping flow system for the spectrophotometric determination of nitrite and nitrate is described. The determination
of nitrite is based on the Griess-Ilosvay reaction. Nitrate can be determined after its on-line reduction to nitrite using
hydrazine sulphate in alkaline medium. Calibration was linear up to 3 mg NO2
− L−1 with a limit of detection (3sb/S) of 0.013 mg NO2
− L−1 an injection throughput of 55 injections h−1 and a repeatability (RSD) of 0.5% for the direct determination of nitrite. Two calibration graphs within the ranges 0.039–7 mg
NO3
− L−1 and 0.026–5 mg NO2
− L−1 were run for the determination of nitrate and nitrite under reducing conditions, respectively. A limit of detection of 0.039 mg
NO3
− L−1 was obtained. An injection throughput of 27 injections h−1 and an RSD lower than 1.5% were achieved. The method was successfully applied to the determination of nitrite and nitrate
in water samples.
Correspondence: Víctor Cerdà, Department of Chemistry, University of the Balearic Islands, Carretera de Valldemossa Km7.5,
07122 Palma de Mallorca, Spain 相似文献
13.
Eduardo Marafon Lauro T. Kubota Yoshitaka Gushikem 《Journal of Solid State Electrochemistry》2009,13(3):377-383
SiO2/ZrO2/C carbon ceramic material with composition (in wt%) SiO2 = 50, ZrO2 = 20, and C = 30 was prepared by the sol–gel-processing method. A high-resolution transmission electron microscopy image
showed that ZrO2 and the graphite particles are well dispersed inside the matrix. The electrical conductivity obtained for the pressed disks
of the material was 18 S cm−1, indicating that C particles are also well interconnected inside the solid. An electrode modified with flavin adenine dinucleotide
(FAD) prepared by immersing the solid SiO2/ZrO2/C, molded as a pressed disk, inside a FAD solution (1.0 × 10−3 mol L−1) was used to investigate the electrocatalytic reduction of bromate and iodate. The reduction of both ions occurred at a peak
potential of −0.41 V vs. the saturated calomel reference electrode. The linear response range (lrr) and detection limit (dl)
were: BrO3
−, lrr = 4.98 × 10−5–1.23 × 10−3 mol L−1 and dl = 2.33 μmol L−1; IO3
−, lrr = 4.98 × 10−5 up to 2.42 × 10−3 and dl = 1.46 μmol L−1 for iodate. 相似文献
14.
I. V. Borisova N. N. Zemlyanskii A. K. Shestakova V. N. Khrustalev Yu. A. Ustynyuk E. A. Chernyshev 《Russian Chemical Bulletin》2000,49(5):933-941
The [Ph3P+−CMe2−SiMe2−SEt]Br− salt was prepared by the reaction of betaine Ph3P+−CMe2SiMeR−S− (1a: R=Me) with EtBr. Acetylation of betaine1a or Et3P+−CHMeSiMe2−S− (2a) afforded 2,2,6-trimethyl-1,3-dioxa-2-silacyclohex-5-ene-4-thione 相似文献
15.
V. V. Senuta S. N. Bendrysheva M. A. Proskurnin 《Journal of Analytical Chemistry》2009,64(11):1174-1184
Thermal lens spectrometry was used for the differential kinetic determination of aniline (over the concentration range of
8 × 10−4–3.2 × 10−3 M) and 4-nitroaniline (2 × 10−4–1.6 × 10−3 M) present in combination in a single sample based on the oxidation reaction with periodate ions in an acidic medium (this
determination is not possible with the spectrophotometric monitoring of the rate of reaction). The thermal lens procedure
(λe = 488.0 nm; 80 mW) was characterized by good performance characteristics in the determination of aniline (c
min = 3 × 10−4 M; c
d = 8 × 10−4 M) and 4-nitroaniline (c
min = 7 × 10−5 M; c
d = 2 × 10−4 M), simplicity, and rapidity. 相似文献
16.
Robert G. Ewing Melanie J. Waltman 《International Journal for Ion Mobility Spectrometry》2009,12(2):65-72
In an effort to better understand the formation of negative reactant ions in air produced by an atmospheric pressure corona
discharge source, the neutral vapors generated by the corona were introduced in varying amounts into the ionization region
of an ion mobility spectrometer/mass spectrometer containing a 63Ni ionization source. With no discharge gas the predominant ions were O2
−, however, upon the introduction of low levels of discharge gas the NO2
− ion quickly became the dominant species. As the amount of discharge gas increased the appearance of CO3
− was observed followed by the appearance of NO3
−. At very high levels, NO3
− species became effectively the only ion present and appeared as two peaks in the IMS spectrum, NO3
− and the NO3
−·HNO3 adduct, with separate mobilities. Since explosive compounds typically ionize in the presence of negative reactant ions, the
ionization of an explosive, RDX, was examined in order to investigate the ionization properties with these three primary ions.
It was found that RDX forms a strong adduct with both NO2
− and NO3
− with reduced mobility values of 1.49 and 1.44 cm2V−1 s−1, respectively. No adduct was observed for RDX with CO3
− although this adduct has been observed with a corona discharge mass spectrometer. It is believed that this adduct, although
formed, does not have a sufficiently long lifetime (greater than 10 ms) to be observed in an ion mobility spectrometer. 相似文献
17.
A novel terbium 2-methyl-benzoimidazole-5-carboxylic acid complex was prepared and incorporated into silica matrix (tetraethoxysilane)
using a mild sol–gel technique. We then successfully fabricated a terbium luminescent xerogel, which maintained intense green
emission even in pure water. The emission was rapidly (~1 s) quenched by ClO− (detection limit 10−5 M) but not NO3
−, CH3COO−, F−, Cl−, Br−, I−, CO3
−, and OH−. The selectivity appears to be due to the high vibrational energy of ClO− as well as its strong oxidation capability. 相似文献
18.
N. M. Klimenko E. A. Rykova M. L. McKee I. N. Senchenya 《Russian Chemical Bulletin》1999,48(3):417-427
Ab initio MP2/6-31G*//HF/6-31G*+ZPE(HF/6-31G*) calculations of the potential energy surface in the vicinity of stationary points and the pathways of intramolecular rearrangements
between low-lying structures of the OBe3F3
+ cation detected in the mass spectra of μ4-Be4O(CF3COO)6 were carried out. Ten stable isomers with di- and tricoordinate oxygen atoms were localized. The relative energies of six
structures lie in the range 0–8 kcal mol−1 and those of the remaining four structures lie in the range 20–40 kcal mol−1. Two most favorable isomers, aC
2v isomer with a dicoordinate oxygen atom, planar six-membered cycle, and one terminal fluorine atom and a pyramidalC
3v isomer with a tricoordinate oxygen atom and three bridging fluorine atoms, are almost degenerate in energy. The barriers
to rearrangements with the breaking of one fluorine bridge are no higher than 4 kcal mol−1, except for the pyramidalC
3v isomer (∼16 kcal mol−1). On the contrary, rearrangements with the breaking of the O−Be bond occur with overcoming of a high energy barrier (∼24
kcal mol−1). A planarD
3h isomer with a tricoordinate oxygen atom and linear O−Be−H fragments was found to be the most favorable for the OBe3H3
+ cation, a hydride analog of the OBe3F3
+ ion; the energies of the remaining five isomers are more than 25 kcal mol−1 higher.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 420–430, March, 1999. 相似文献
19.
Sensitive fluorescent probes for determination of hydrogen peroxide and glucose based on enzyme-immobilized magnetite/silica nanoparticles 总被引:2,自引:0,他引:2
Qing Chang Lihua Zhu Guodong Jiang Heqing Tang 《Analytical and bioanalytical chemistry》2009,395(7):2377-2385
Sensitive fluorescent probes for the determination of hydrogen peroxide and glucose were developed by immobilizing enzyme
horseradish peroxidase (HRP) on Fe3O4/SiO2 magnetic core–shell nanoparticles in the presence of glutaraldehyde. Besides its excellent catalytic activity, the immobilized
enzyme could be easily and completely recovered by a magnetic separation, and the recovered HRP-immobilized Fe3O4/SiO2 nanoparticles were able to be used repeatedly as catalysts without deactivation. The HRP-immobilized nanoparticles were able
to activate hydrogen peroxide (H2O2), which oxidized non-fluorescent 3-(4-hydroxyphenyl)propionic acid to a fluorescent product with an emission maximum at 409 nm.
Under optimized conditions, a linear calibration curve was obtained over the H2O2 concentrations ranging from 5.0 × 10−9 to 1.0 × 10−5 mol L−1, with a detection limit of 2.1 × 10−9 mol L−1. By simultaneously using glucose oxidase and HRP-immobilized Fe3O4/SiO2 nanoparticles, a sensitive and selective analytical method for the glucose detection was established. The fluorescence intensity
of the product responded well linearly to glucose concentration in the range from 5.0 × 10−8 to 5.0 × 10−5 mol L−1 with a detection limit of 1.8 × 10−8 mol L−1. The proposed method was successfully applied for the determination of glucose in human serum sample. 相似文献
20.
Jinzhang Gao Jing Liu Jie Ren Xiuli Niu Yingying Zhang Wu Yang 《Central European Journal of Chemistry》2009,7(3):298-302
This paper described the determination of p-nitroaniline in a double organic substrate oscillating system of tartrate-acetone-Mn2+-KBrO3-H2SO4. Under the optimum conditions, temperature was chosen as a control parameter to design the bifurcation point and proposed
a convenient method for determination of p-nitroaniline. Results showed that the system consisting of 3.5 mL 0.06 mol L−1 tartrate, 4.0 mL 0.7 mol L−1 H2SO4, 1.5 mL 1.5×10−4 mol L−1 MnSO4, 4.0 mL 0.4 mol L−1 acetone and 7.0 mL 0.05 mol L−1 KBrO3 was very sensitive to the surrounding at 33.5°C. A good linear relationship between the potential difference and the negative
logarithm concentration of p-nitroaniline was obtained to be in the range of 2.50×10−7∼3.75×10−5 mol L−1 with a lower detection limit of 2.50×10−8 mol L−1.
相似文献