共查询到20条相似文献,搜索用时 15 毫秒
1.
An optical chemical sensor based on 2-mercaptopyrimidine (2-MP) in plasticized poly(vinyl chloride) (PVC) membrane incorporating
(N,N-diethyl-5-(octadecanoylimino)-5H benzo[a]phenoxazine-9-amine (ETH 5294) and sodium tetraphenyl borate (NaTPB) for batch and
flow-through determination of mercury ion is described. The response of the sensor is based on selective complexation of Hg2+ with 2-MP in the membrane phase, resulting in an ion exchange process between H+ in the membrane and Hg2+ in the sample solution. The influences of several experimental parameters, such as membrane composition, pH, and type and
concentration of the regenerating reagent, were investigated. The sensor has a response range of 2.0 × 10−9 to 2.0 × 10−5 mol L−1 Hg2+ with a detection limit of 4.0 × 10−10 mol L−1 and a response time of ≤45 s at optimum pH of 6.5 with high measurement repeatability and sensor-to-sensor reproducibility.
It shows high selectivity for Hg2+ over several transition metal ions, including Ag+, Cd2+, Co2+, Cr3+, Cu2+, Fe3+, Mn2+, Ni2+, and common alkali and alkaline earth ions such as Na+, K+, Mg2+, Ca2+, and Pb2+. The sensor membrane can be easily regenerated with dilute acid solutions. The sensor has been used for the determination
of mercury ion concentration in water samples. 相似文献
2.
3.
Asakawa D Moriguchi S Takayama M 《Journal of the American Society for Mass Spectrometry》2012,23(1):108-115
The influence of arginine (Arg), lysine (Lys), and phenylalanine (Phe) residues and phosphorylation on the molecular ion yields
of model peptides have been quantitatively studied using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry
in both positive- and negative-ion mode. The results obtained from these experiments have been interpreted from the standpoint
of two different components, namely, desorption and ionization, on the basis of the physicochemical properties of constituent
amino acids of the model peptides. The presence of basic residues such as Arg and Lys enhanced the ion yields of protonated
molecules [M + H]+. An N-terminal rather than a C-terminal Arg residue was advantageous for the formation of both [M + H]+ and [M – H]–. The presence of the Phe residue resulted in the increase of the ion yields of both [M + H]+ and [M – H]–. In contrast, the presence of phosphate group(s) contributed to the suppression of the yields of both [M + H]+ and [M – H]– due to the loss of phosphate group. The detection limits for both [M + H]+ and [M – H]– of model peptides have been evaluated. 相似文献
4.
In situ scanning tunneling microscopy (STM) was used to examine the structure of thiocyanate adlayers specifically adsorbed
on Rh(111) in solutions of potassium hydroxide and perchloric acid, both containing potassium thiocyanate (KSCN). An atomically
flat terrace-step structure was consistently observed on Rh(111) surfaces prepared by the flame-annealing-quenching method.
The Rh(111)-(1 × 1) atomic structure was discerned on the atomically flat terrace even in the alkaline solution. High-resolution
STM images disclosed two different structures of the SCN− adlayers, () and (2 × 2), in the alkaline and the acidic media, respectively. In each structure, an individual adsorbed SCN− ion appeared as a single spot with a constant corrugation height in STM images, suggesting that SCN− ions adsorbed predominantly with their
S-ends at particular bonding sites on Rh(111). The difference in the adlayer structure in the two solutions can be attributed
to the interaction between adsorbed SCN− and coadsorbed K+ in the alkaline solution, and is different from that between adsorbed SCN− and H+ in the acidic solution.
Received: 26 February 1997 / Accepted: 3 March 1997 相似文献
5.
Silvia Richter Matthias Bückins Anke Aretz Stepan Kyrsta Michael Spähn Joachim Mayer 《Mikrochimica acta》2004,145(1-4):187-192
Electron probe microanalysis (EPMA) offers high sensitivity and high accuracy in quantitative measurements of chemical compositions and mass coverages. Owing to the low detection limits of the wavelength-dispersive technique, monolayers with mass coverages of about 0.05µgcm–2 can be detected. Assuming a density of 5gcm–3 this corresponds to a thickness of 0.1nm. With these advantages in mind, EPMA was extended to depth profile analysis in the sub-micron range using a surface removal technique.The present paper shows how depth profile analysis can be improved by combining EPMA and the focused ion beam (FIB) technique. The focused ion beam system uses a Ga+ ion beam. The ion beam allows the milling of defined geometries on the nanometer scale, so that very shallow bevels with exactly defined angles in relation to the surface can be obtained. Low surface damage is expected due to low sputtering effects. Calibrated WDX measurements along the bevel deliver quantitative concentration depth profiles. First results obtained with this new combination of methods will be presented for a multilayered sample used in optical data storage. 相似文献
6.
Werner Hanay Heinz Böhland Mathias Noltemeyer Hans-Georg Schmidt 《Mikrochimica acta》2000,133(1-4):197-201
Di-N-selenocyanato-bis(N,N′-dimethylfor- mamide)beryllium (1) was prepared and characterized by chemical analyses, and single
crystal X-ray structure analysis. Crystals of 1 are monoclinic with a = 1837.2 (8) pm, b = 547.1 (2) pm, c = 1435.6 (6) pm, β = 93.27 (4)°, space group C2/c, Z = 4. Beryllium is tetrahedrally coordinated by two N-bonded selenocyanate and two O-bonded N,N′-dimethylformamide ligands
and intermolecular Se ⋯ Se as well as Se ⋯ H interactions are observed. 相似文献
7.
Malicka E Sitko R Zawisza B Heimann J Kajewski D Kita A 《Analytical and bioanalytical chemistry》2011,399(9):3285-3292
The paper presents possibilities and difficulties in nondestructive analysis of small multielement single crystals performed
by means of X-ray spectrometry techniques: micro-X-ray fluorescence spectrometry (μ-XRF), energy-dispersive electron probe
microanalysis (ED-EPMA), and X-ray photoelectron spectroscopy (XPS). The capability of the X-ray spectroscopy techniques in
elemental analysis is demonstrated with the single crystals of selenide spinels of the general formula M
x
N
y
Cr
z
Se4 (M+2 and N+3 are, for example, Zn+2, V+3, Ga+3, Cd+2, In+3, and Sb+3). The results of the nondestructive analyses (μ-XRF, ED-EPMA, and XPS) are compared with those obtained by inductively coupled
plasma optical emission spectrometry (ICP-OES) and wavelength-dispersive X-ray spectrometry (WDXRF) following sample digestion.
The present study shows satisfactory agreement between the results of μ-XRF analysis performed using the standardless fundamental
parameter method and the results obtained with the WDXRF and ICP-OES analyses. If the measured single crystal is precisely
positioned, the difference between μ-XRF and wet analysis (WDXRF and ICP-OES) does not exceed 5% rel. The reliable results
of ED-EPMA can be obtained only if the measured area is sufficiently large, i.e., of 200 × 300 μm. Even if this condition
is fulfilled, the relative difference between the ED-EPMA and the wet analysis may reach 10% rel. In case of the XPS analysis,
the accuracy of results depends on the proper preparation of the sample surface. It should be free of contamination that can
be obtained by scraping in situ in ultrahigh vacuum. The ion etching, commonly used for cleaning the surface, leads to preferential
sputtering; therefore, the reliable results cannot be obtained. 相似文献
8.
Shangfen Gao Guangqun Tan Hongyan Yuan Dan Xiao Martin M. F. Choi 《Mikrochimica acta》2006,153(3-4):159-162
A simple and green analytical procedure based on chlorophyll a is presented for the determination of Hg2+ ion. Chlorophyll a was extracted and purified from the leaves of pea and is employed as a reagent for analysis of Hg2+ ion. It displays remarkable fluorescence emission at 674 nm when excited at 412 nm. The emission intensity decreased significantly
on exposure to various concentrations of Hg2+ ion. This forms the basis for the determination of Hg2+ ion. The proposed method was evaluated for sensitivity and selectivity. The linear concentration range was found to be 2.0–10 μM
with r2 = 0.997 and the limit of detection for Hg2+ ion was 1.3 μM. Ions including Pb2+, Cd2+, Ag+, Zn2+, Co2+, Ni2+, Cu2+, Mg2+, Mn2+, Ru3+, Er3+, K+, Na+, NH4+, Cl−, NO3−, CH3COO− and SO42− did not interfere with the measurement of Hg2+ ion even at 500-fold excess. Since chlorophyll a is widely available in the leaves of most plants, and the extraction and purification process is simple, this technique can
provide an alternative, sensitive and economical way to determine Hg2+ ion. 相似文献
9.
Zhao Yang Gao-Shao Cao Jian Xie Xin-Bing Zhao 《Journal of Solid State Electrochemistry》2012,16(3):1271-1277
LiMnPO4, with a particle size of 50–150 nm, was prepared by oleic acid-assisted solid-state reaction. The materials were characterized
by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical
properties of the materials were investigated by galvanostatic cycling. It was found that the introduction of oleic acid in
the precursor led to smaller particle size and more homogeneous size distribution in the final products, resulting in improved
electrochemical performance. The electrochemical performance of the sample could be further enhanced by Co doping. The mechanism
for the improvement of the electrochemical performance was investigated by Li-ion chemical diffusion coefficient
( [(D)\tilde]\textLi ) \left( {{{\tilde{D}}_{\text{Li}}}} \right) and electrochemical impedance spectroscopy measurements. The results revealed that the
[(D)\tilde]\textLi {\tilde{D}_{\text{Li}}} values of LiMnPO4 measured by cyclic voltammetry method increase from 9.2 × 10−18 to 3.0 × 10−17 cm2 s−1 after Co doping, while the charge transfer resistance (R
ct) can be decreased by Co doping. 相似文献
10.
Compositional characterization of metal-DLC (metal-containing diamond-like carbon) hard coatings is carried out by (WDS)-EPMA
and MCs+-SIMS. EPMA enables accurate (± 5% relative) quantitative analysis including minor concentrations (0.1–10 at%) of N, O and
Ar. Under conditions of “near-surface” EPMA (E0 < 10 keV) the influence of surface oxide films on “pure” metal standards may be a limiting factor in respect of accuracy.
Depth profiling of sufficiently “thick” layered structures (film thickness ≥ 2 μm) is carried out by EPMA-line scans along
mechanically prepared bevels. The depth resolution is about 0.2 μm. SIMS in the MCs+-mode enables high resolution (< 20 nm) depth profiling of metal-DLC layered structures including the determination of H (1–20 at%).
MCs+-SIMS, i.e. employing Cs+ primary ions and monitoring MCs+ molecular secondary ions (M is the element of interest) is presented as a promising route towards sufficiently accurate (10–20%)
SIMS-quantification. Matrix-independent relative sensitivity factors for MCs+-SIMS are derived from homogeneous coating materials defined by EPMA. EPMA proves to be also useful to detect problems related
to SIMS of Ar in metal-DLC materials. The combination EPMA-SIMS is demonstrated as an effective analytical strategy for quality
control in industrial production and to support the development of metal DLC layered structures with optimum tribological
properties. 相似文献
11.
Kilpatrick LE Neta P Yang X Simón-Manso Y Liang Y Stein SE 《Journal of the American Society for Mass Spectrometry》2012,23(4):655-663
Tandem mass spectra of peptide ions, acquired in shotgun proteomic studies of selected proteins, tissues, and organisms, commonly
include prominent peaks that cannot be assigned to the known fragmentation product ions (y, b, a, neutral losses). In many
cases these persist even when creating consensus spectra for inclusion in spectral libraries, where it is important to determine
whether these peaks represent new fragmentation paths or arise from impurities. Using spectra from libraries and synthesized
peptides, we investigate a class of fragment ions corresponding to yn-1 + 10 and yn-1 + 11, where n is the number of amino acid residues in the peptide. These 10 and 11 Da differences in mass of the y ion were
ascribed before to the masses of [+ CO – H2O] and [+ CO – NH3], respectively. The mechanism is suggested to involve dissociation of the N-terminal residue at the CH-CO bond following
loss of H2O or NH3. MS3 spectra of these ions show that the location of the additional 10 or 11 Da is at the N-terminal residue. The yn-1 + 10 ion is most often found in peptides with N-terminal proline, asparagine, and histidine, and also with serine and threonine
in the adjacent position. The yn-1 + 11 ion is observed predominantly with histidine and asparagine at the N-terminus, but also occurs with asparagine in positions
two through four. The intensities of the yn-1 + 10 ions decrease with increasing peptide length. These data for yn-1 + 10 and yn-1 + 11 ion formation may be used to improve peptide identification from tandem mass spectra. 相似文献
12.
Quantitative electron-probe microanalysis was used to determine the chemical composition of an Fe- and Nb-doped bismuth-based
BaBi4Ti4O15 perovskite compound. Elemental concentrations of Fe, Nb, Bi, Ba and Ti were accurately measured using wavelength-dispersive
X-ray spectroscopy that was optimised for the analysis of a complex oxide matrix containing minor concentrations of dopants.
Measurements were performed with a JEOL JXA 840A electron probe microanalyser at 20 and 26 kV, 50 nA beam current, 100 s maximum
counting time and 0.3% preset counting deviation (σc) using both PET and LiF crystals. K-ratios were quantified by the ZAF and the φ(ρz) PAP matrix-correction procedures. The
results showed that dopants incorporate into the BaBi4Ti4O15 at Ti4 + sites according to the Ba1−4XBi4 + 4XTi4−4XFe4XO15 and Ba1 + 4XBi4−4XTi4−4XNb4XO15 solid-solution formulae. The majority of the excess charge introduced by the substitution of Ti4 + with Fe3 + or Nb5 + is compensated for the change in the Ba2 + /Bi3 + ratio. 相似文献
13.
Takahashi S Nakamura M Fujii T 《Journal of the American Society for Mass Spectrometry》2012,23(3):547-552
This report describes the development of a compact ion attachment mass spectrometry system. A single turbomolecular pump was
employed to fill the basic requirements for vacuum conditions simply and cost-effectively, without the need for a differential
pumping stage. A Li+ ion source was placed in the first of two vacuum chambers; a 0.4 mm aperture allowed the product ions to enter the second
chamber for mass analysis. With the present system, any chemical species, including radical intermediates, can be detected
at atmospheric pressure in real-time. The minimum detectable amount (at S/N = 3) of toluene was around 1.3 × 10–12 g/s with a linearity greater than 104. For illustrative purposes, we tested the system on laboratory air and on aroma compounds in the headspace of the Yuzu plant,
Citrus junos. 相似文献
14.
Uranium single particle analysis has been performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the performances are compared with that provided by scanning electron microsopy and single particle counting. The transient signal induced by the flash of ions due to the ionisation of an uranium colloidal particle in the plasma torch can be detected and measured for selected uranium ion masses (238U+, 235U+ or 254[238U16O]+) by the mass spectrometer. The signals recorded via time scanning are analysed as a function of particle size or fraction of the studied element or isotope in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. The feasibility tests were performed on uranium dioxide particles. The study also describes the experimental conditions and the choice of mass to detect uranium colloids in a single particle analysis mode. 相似文献
15.
The application of a hexapole collision cell in quadrupole based inductively coupled plasma mass spectrometry (HEX-ICP-QMS)
was studied systematically in order to characterize the performance of this approach for multielement analysis. Additionally,
the performance of different solution introduction systems was studied for use with HEX-ICP-QMS (Platform, Micromass Ltd.,
Manchester, UK) and the developed methods were applied in the multielement analysis of biological tissue. A significant improvement
in detection limits was achieved for ions affected by interferences with argon ions and argon-based molecular ions due to
the removal of Ar+ and ArX+ ions (X = H, C, N, O, Ar) as well as for heavy elements (m > 100 u) due to better ion transmission through the hexapole ion
guide. Metal oxide ion formation was reduced by up to ten times by the application of hexapole bias potential. Accuracy of
the HEX-ICP-QMS measurements was assessed by analyzing standard reference material SRM 1566a Oyster Tissue and comparison
with neutron activation analysis. Good agreement of measured trace element concentrations with certified values was found
for most elements.
Received December 7, 2000. Revision April 3, 2001. 相似文献
16.
Iovka Dragieva Christina Deleva Mladen Mladenov Ivania Markova-Deneva 《Monatshefte für Chemie / Chemical Monthly》2002,82(1):807-814
Different structures of the interglobular space or voids between self-organized nanoparticles lead to differences in the measurable magnetic properties of single-domain particle chains of similar composition, grain size, and amorphous structure of the single globules. The volumes and radii of nanoparticles obtained by application of a magnetic field (3 to 15 nm) are larger than those determined without application of a magnetic field during the borohydride reduction process. Two types of hydrogen containing nanotubes with diameters of up to 2 (small-size containers) and 5 nm (large-size containers) are produced using as a driving force the domain wall formation energy between ferromagnetic nanoparticles with quantum size effected dimensions prepared by this reduction method at room temperature and ambient atmosphere. Nanoscale hydrogen containers can be used instead of MeH nanoparticle electrodes as perfect energy charge transfer media of high efficiency (close to 100%) using Li ion electrolytes. No influence on the electrode temperature and no participation of OH− and H2O in the main charge/discharge transfer reactions were observed. 相似文献
17.
Torsten Barfels Bernd Schmidt Andreas von Czarnowski Hans-Joachim Fitting 《Mikrochimica acta》2002,139(1-4):11-16
For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary
electron energy E
0 = 2…30 keV. Applying a constant incident power regime (E
0·I
0 = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx.
Thermally grown SiO2 layers of thickness d = 500 nm have been implanted by Ge+-ions of energy 350 keV and doses (0.5–5)1016 ions/cm2. Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of dm≅240 nm are expected. Afterwards the layers have been partially annealed up to T
a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of
the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth
towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster
formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm. 相似文献
18.
The specificity of the exchange between divalent (Di2+ = Ca2+ or Ba2+) and monovalent (M+ = Li+, Na+ or K+) ions onto a polyacrylic chain is examined using conductometric and microcalorimetric techniques. Assuming the formation
of a bidentate complex between the Di2+ and the carboxylate groups, the conductometric data give the exchange ratio (Di2+/M+) and the speciation of the acrylic groups. No significant difference is observed between the three alkali-metal ions for
a given Di2+ ion. Comparisons between Ca2+ and Ba2+ show a stronger hydrophobicity of the former as it precipitates at a complexation ratio r = 0.33 versus r = 0.45 for the Ba2+ salt. Microcalorimetric data show that all Di2+/M+ exchange energies are positive and depend significantly on the type of cations. The largest displacement energy (the more
positive) is found for the binding of Ca2+ with sodium polyacrylate (8.13 kJ · mol−1) and the smallest for Ba2+ with lithium polyacrylate (1.88 kJ · mol−1). The interpretation of the data leads to the conclusion that specificity of the Di2+ binding originates in the dehydration phenomenon and specificity between the three alkali-metal ions is due to the decrease
in the electrostatic bond strength with an increase in the ionic radii. The Di2+/M+ exchange is entropically driven.
Received: 28 January 1999 Accepted in revised form: 7 April 1999 相似文献
19.
A mechanism for the recombination of tert-butyl radicals is postulated to involve the loosely bonded intermediates tert-C4H9⋯tert-C4H9. Three processes contribute to the overall recombination rate constant: tert-C4H9 + tert-C4H ⇆ tert-C4H9⋯tert-C4H9 characterized by the equilibrium constant K
1 and tert-C4H9⋯tert-C4H9 → C8H18* characterized by the rate constant k
2, k
rec,∞(T) ≈ K
1
k
2. This recombination rate constant exhibits a negative temperature dependence and is proportional to T
−3/2. The agreement with experiment is very good.
Received: 2 October 2000 / Accepted: 2 May 2002 / Published online: 7 August 2002 相似文献
20.
Gao J Owen BC Borton DJ Jin Z Kenttämaa HI 《Journal of the American Society for Mass Spectrometry》2012,23(5):816-822
Saturated and unsaturated, linear, branched, and cyclic hydrocarbons, as well as polyaromatic and heteroaromatic hydrocarbons,
were successfully ionized by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as reagents in a linear
quadrupole ion trap (LQIT) mass spectrometer. Pentane was proved to be the best reagent among the hydrocarbon reagents studied.
This ionization method generated different types of abundant ions (i.e., [M + H]+, M+•, [M – H]+ and [M – 2H]+ •), with little or no fragmentation. The radical cations can be differentiated from the even-electron ions by using dimethyl
disulfide, thus facilitating molecular weight (MW) determination. While some steroids and lignin monomer model compounds,
such as androsterone and 4-hydroxy-3-methoxybenzaldehyde, also formed abundant M+• and [M + H]+ ions, this was not true for all of them. Analysis of two known mixtures as well as a base oil sample demonstrated that each
component of the known mixtures could be observed and that a correct MW distribution was obtained for the base oil. The feasibility
of using this ionization method on the chromatographic time scale was demonstrated by using high-performance liquid chromatography
(HPLC) with hexane as the mobile phase (and APCI reagent) to separate an artificial mixture prior to mass spectrometric analysis. 相似文献