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1.
Summary The influence of the injection volume and the sample solvent on column efficiency has been evaluated in packed nano liquid
chromatography using columns 150μ i.d. Evaluation of column performance was by means of reduced plate height (h) versus reduced velocity (v) for four polyaromatic hydrocarbon test compounds (PAHs). When compounds are dissolved in a weak solvent (such as MeCN: H2O, 30∶70), and whatever the injection volume −60 or 200 nL-a gain in efficiency can be observed due to the well-known on-column
focusing phenomenon, but keeping constant solute retention factors. Under optimized conditions (flow rate: 150 nLmin−1, solvent sample MeCN: H2O, 30∶70, injection volume 200 nL), a reduced plate height of 1.83 has been obtained for a 15 μm C18 packing corresponding to 36000 plates m−1, which illustrates the absence of any extracolumn band broadening under nano LC conditions. 相似文献
2.
Maria Chiara Pietrogrande Dimitri Bacco Mattia Mercuriali 《Analytical and bioanalytical chemistry》2010,396(2):877-885
This paper describes methods for the determination of low-molecular-weight (LMW) dicarboxylic acids in atmospheric aerosols
as important chemical tracers for source apportionment of aerosol organics and for studying atmospheric processes leading
to secondary organic aerosol formation. The two derivatization procedures most widely used in GC analysis of dicarboxylic
acids were compared: esterification using BF3/alcohol reagent and silylation using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA). The advantages and drawbacks of the two methods are investigated and compared
in terms of (1) precision and accuracy of the results and (2) sensitivity and detection limit of the procedure. The comparative
investigation was performed on standard solutions containing target C3–C9 dicarboxylic acids and on experimental particulate matter (PM) samples. Attention was focused on low-volume sampling devices
that collect small amounts of sample for organic speciation. The results show that, overall, both the techniques appear suitable
for the analysis of LMW dicarboxylic acids in atmospheric aerosols since they provide low detection limits (≤4 ng m−3) and satisfactory reproducibility (RSD% ≤ 15%). Between them, BSTFA should be the reagent of choice under the most limiting
conditions of PM filters collected by low-volume air samplers: It provides determination of all the target C3–C9 dicarboxylic acids with lower detection limits (≤2 ng m−3) and higher reproducibility (RSD% ≤ 10%)
相似文献
3.
I. G. Fomina Zh. V. Dobrokhotova G. G. Aleksandrov O. Yu. Proshenkina M. L. Kovba A. S. Bogomyakov V. N. Ikorskii V. M. Novotortsev I. L. Eremenko 《Russian Chemical Bulletin》2009,58(1):11-20
Methods were developed for the controlled thermal synthesis of high-spin cubane-like pivalates {MII
4(μ3−OR)4} (M = Co or Ni; R = H or Me) starting from mono-and polynuclear complexes. The solid-state thermal decomposition of the known
pivalate clusters [MII
4(μ3−OMe)4−(μ2−OOCBut)2(η2−OOCBut)2(MeOH)4] and the new clusters [M4II(μ3)−OH4(η1−OOCBut)3−(μ−(NH2)2C6H2Me2)3(η1−(NH2)2C6H2Me2)3]+(OOCBut)− (M = Co or Ni) was studied by differential scanning calorimetry and thermogravimetry. The thermolysis of cubane-like CoII
and NiII pivalates is a destructive process. The phase composition of the decomposition products is determined by the nature
of coordinated ligands and the structural features of the metal core. 相似文献
4.
Summary A novel procedure had been developed for the preparation of RP packings. A C18 alkyl-chain was bound onto spherical silica (particle size dp=5 μm, s=300 m2g−1) with glycidoxypropyltrimethoxysilane as coupling agent. Elemental analysis, X-ray photoelectron spectroscopy (XPS), Fourier
transform infrared (FT-IR) and chromatographic evaluation confirmed the bonding of the packings and their RP behavior. 相似文献
5.
The kinetics of nucleophilic substitution of pyridine in bis-cationic [Pt(L)(py)]2+ complexes (L=SNS, NNN, NSN) [SNS=bis(methylthiomethyl)pyridine, NNN=bis(2-pyridylmethyl)amine, NSN=bis(2-pyridylmethyl)sulphide]
by a series of nucleophiles (Cl−, Br−, I−, N3−, (C2H5)2S, NH3, thiourea (tu), NO2−, C5H10NH, SeCN−, SCN−, CN− when L=SNS; Cl−, Br−, I−, N3−, (C2H5)2S, SCN−, NH3, NO2− when L=NNN; Br−, N3−, NO2−, NH3, C5H10NH when L=NSN) have been measured in MeOH at 25 °C, μ =0.1 mol dm−3 (LiClO4 or LiCF3SO3). The logarithms of the second-order rate constants calculated at μ=0, log k° 2, do not follow the dependence upon the n° Pt scale. In particular, the reactivity of the biphilic reagents tu, SeCN−, SCN− and, to a lesser extent, NO− 2, towards these doubly charged substrates is largely lower than expected on the basis of the n° Ptscale. There are good linear relationships between logk° 2 for the bis-cationic substrate [Pt(SNS)(py)]2+, chosen as the standard, and log k° 2 for the same reactions with [Pt(NNN)(py)]2+, [Pt(NSN)(py)]2+ and other double charged complexes previously studied. A new wide nucleophilicity scale based on [Pt(SNS)(py)]2+, that is appropriate to all the bis-cationic substrates, is here proposed 相似文献
6.
K. E. Ozbas 《Journal of Thermal Analysis and Calorimetry》2008,93(2):641-649
In this study, the relationship between particle size and pyrolysis characteristics of Elbistan lignite was examined by using
the thermogravimetric (TG/DTG) and differential thermal analysis (DTA) techniques. Lignite samples were separated into different
size fractions. Experiments were conducted at non-isothermal conditions with a heating rate of 10°C min−1 under nitrogen atmosphere up to 900°C. Pyrolysis regions, maximum pyrolysis rates and characteristic peak temperatures were
determined from TG/DTG curves. Thermogravimetric data were analyzed by a reaction rate model assuming first-order kinetics.
Apparent activation energy (E) and Arrhenius constant (A
r) of pyrolysis reaction of each particle size fraction were evaluated by applying Arrhenius kinetic model. The apparent activation
energies in the essential pyrolysis region were calculated as 27.36 and 28.81 kJ mol−1 for the largest (−2360+2000 μm) and finest (−38 μm) particle sizes, respectively. 相似文献
7.
Tahra Ayed Nathalie Guihéry Bahoueddine Tangour Jean-Claude Barthelat 《Theoretical chemistry accounts》2006,116(4-5):497-504
Correlated ab initio calculations have been performed on three dipalladium(I) complexes. These compounds differ both by the metal–metal interaction and by the metal–ligand interaction. The [Pd2Cl2(μ −H2PCH2PH2)2] complex exhibits a σ overlap between the two binding metallic orbitals and has no bridging ligand. In [Pd2Cl4(μ −CO)2]2−, the leading interaction between the two palladium involves a π overlap between the metallic orbitals and goes through the two bridging CO ligands. In [Pd2Cl2(μ −CO)(μ −H2PCH2 PH2)2], a single CO ligand bridges the two palladium atoms which interact through a hybrid σ–δ overlap. The three compounds also differ by the metal–metal distances. Surprisingly enough, while the palladium atoms are formally d
9 in all these complexes, none of them is paramagnetic. We propose here a detailed analysis of the electronic structures of these compounds and rationalize their chemical structures as well as the role of back-donation in the CO bridged compounds. Finally, since highly correlated treatments are used to describe these complexes, a detailed study of the role of both non-dynamical and dynamical correlations is performed. Concerning the [Pd2Cl4(μ −CO)2]2− complex, this analysis has revealed that the complex is not bound at the lowest correlated levels of calculation and therefore dynamical correlation is alone responsible for its binding energy. 相似文献
8.
R. Kopunec F. N. Abudeab S. Skraŝková 《Journal of Radioanalytical and Nuclear Chemistry》1998,230(1-2):51-61
Solvent extraction of pertechnetate anions from aqueous solutions of some mineral acids (HCl, HNO3, HClO4, H2SO4), (NaCl, NaNO3, NaClO4, K2CrO4, NaCO3), NaOH and NH4OH by tetraphenylphosphonium chloride in chloroform and nitrobenzene was studied. The results are presented in the form of
the dependencies of extraction characteristics of TcO
4
−
(distribution ratio, percentage of extraction) on the (C6H5)4PCl, H+ and competitive anion concentrations. The solvent extraction of sub-and super-stoichiometric ratio of TcO
4
−
: (C6H5)4P+ was performed. The extraction constant values of ion pairs TcO
4
−
−Cl−, TcO
4
−
−NO
3
−
, TcO
4
−
−ClO
4
−
and of individual anions TcO
4
−
, Cl−, NO
3
−
, ClO
4
−
were calculated. 相似文献
9.
Alain Mallard Corine Simonnet-Jégat Hélène Lavanant Jérôme Marrot Francis Sécheresse 《Transition Metal Chemistry》2008,33(2):143-152
The reaction of DMA (C2(CO2Me)2) with MoS42−, WS42−, and VS43− led to six dithiolene compounds. (NEt4)2[Mo2(X)2(μ-S) 2(η2-S2C2(CO2Me)2)2] 1, (X = O or S), (NEt4)2[V(η2-S2C2(CO2Me)2)3] 2a, (NEt4)2[V(O)(η2-S2C2(CO2Me)2)2] 2b, (NEt4)2[W2(S)2(μ-S)2(η2-S2C2(CO2Me)2)2] 3, (NEt4)2[W(O)(η2-S2C2(CO2Me)2)2] 4 and (NEt4)2[W2(μ-S)2(η2 -S2C2(CO2Me)2)4] 5 were isolated in the solid state. The structures of 2a, 3, 4 and 5 were determined by single crystal X-ray diffraction study. The compounds 1 and 2b were characterised in solution by ESMS (Electrospray Mass Spectrometry) and in the solid state by IR spectroscopy. ESMS data
also allowed proposal of a reaction scheme which rationalizes the formation of the different species present in solution. 相似文献
10.
Summary Indirect UV detection in capillary zone electrophoresis (CZE) is frequently used for the determination of inorganic anions
and carboxylic acids. However, there are few reports on direct UV detection of these solutes in real samples. This paper describes
the use of direct UV detection of inorganic anions and organic acids in environmental samples using co-electroosmotic capillary
zone electrophoresis (co-CZE) at 185 nm. The best separation and detection of the solutes was achieved using a fused silica
capillary with an electrolyte containing 25 mM phosphate, 0.5 mM tetradecyltrimethylammonium bromide (TTAB) and 15% acetonitrile
(v/v) at pH 6.0. Four common inorganic anions (Cl−, NO2
−, NO3
− and SO4
2−) and 11 organic acids (oxalic, formic, fumaric, tartaric, malonic, malic, citric, succinic, maleic, acetic, and lactic acid),
were determined simultaneously in 15 min. Linear calibration plots for the test solutes were obtained in the range 0.02–0.5
mM with detection limits ranging from 1–9 μM depending on the analyte. The proposed method was successfully used to determine
inorganic anions and carboxylic acids in soil and plant tissue extracts with direct injection of the sample. 相似文献
11.
LiCheng Song 《中国科学B辑(英文版)》2009,52(1):1-14
This article describes recent developments in chemical study on a series of butterfly-shaped μ-CO-containing Fe/E (E = S, Se, Te) cluster salts. These salts include eleven novel cluster anions, which are the single butterfly one μ-CO-containing [(μ-RE)(μ-CO)Fe2(CO)6]- (A), the double butterfly two μ-CO-containing {[(μ-CO)Fe2(CO)6]2(μ-EZE-μ)}2- (B, E = S; C, E = Se), the triple butterfly three μ-CO- containing {[(μ-CO)Fe2(CO)6]3[(μ-SCH2CH2)3N]}3- (D), {[(μ-CO)Fe2(CO)6]3[1,3,5-(μ-SCH2)3C6H3]}3- (E), {[(μ- CO)... 相似文献
12.
The review summarizes the results of investigations of ionic fullerene compounds containing negatively charged dimers and
fullerene anions coordinated to metalloporphyrins. Fullerene radical anions were found to form diamagnetic singly bonded (C60
−)2 and (C70
−)2 dimers. Dimerization is reversible and leads to paramagnetic—diamagnetic phase transitions or a decrease in the magnetic
moment of the complexes. The temperature, at which dissociation of the (C60
−)2 dimers begins, varies from 140 to 320 K; the corresponding temperature for the (C70
−)2 dimers varies from 260 to 360 K and higher. We prepared the first doubly bonded (C60
−)2 dimer. At 300 K, this dimer exists as a biradical. The fullerene radical anions form Co—C coordination bonds with cobalt(II) porphyrinates. The resulting anions are diamagnetic. In some cases, Co—C coordination bonds undergo reversible dissociation,
resulting in magnetic transitions from the diamagnetic to the paramagnetic state.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 361–381, March, 2007. 相似文献
13.
Yong Leng Kelvin Tan Chin Wai Alaric Koh Ting Bin Lim Weng Kee Leong 《Journal of Cluster Science》2006,17(3):509-516
Reaction of the heteronuclear cluster RuOs3(μ−H)2(CO)13, 1, with diphenylacetylene afforded the tetrahedral cluster RuOs3(μ−H)2(μ3,η1:η2:η1−C2Ph2)(CO)11, 2, in good yield. Spectroscopic evidence suggests that 2 exist as two isomers in solution. 相似文献
14.
Comparison of adsorbents for on-line solid-phase extraction of polycyclic aromatic hydrocarbons before liquid chromatography with UV detection 总被引:1,自引:0,他引:1
Summary On-line solid-phase extraction (SPE) coupled with reversed-phase liquid chromatography and UV detection at 254 nm has been
used for the determination of trace-level polycyclic aromatic hydrocarbons (PAH) in soil extracts. Five commercially available
adsorbents (C8, C18, PLRP-S, PRP-1, and Bond-Elut Env) were evaluated. Results showed that recovery of the PAH decreased with increasing molecular
weight, because of their poorer solubility. Recovery of high-molecular-weight PAH was significantly improved by addition of
10% (v/v) acetonitrile to the sample before loading of the SPE adsorbent. PAH recovery ranged from 64.0 to 108% when a 50
mL sample spiked with 1 μg L−1 was applied to these adsorbents. Determination of PAH was possible with detection limits below 0.05 μg L−1, which corresponds to 0.2 μg kg−1 soil. The method was successfully used to determine PAH in soil extracts. 相似文献
15.
V. A. Lucca Neto A. E. Mauro A. V. G. Netto A. C. Moro V. M. Nogueira 《Journal of Thermal Analysis and Calorimetry》2009,97(1):57-60
The cyanate-bridged cyclopalladated compound [Pd(C2,N-dmba)(μ-NCO)]2 (dmba=N,N-dimethylbenzylamine) reacts in acetone with pyrazole (pz), 3,5-dimethylpyrazole (dmpz), imidazole (imz) and 2-methylimidazole
(mimz) to give [Pd2(C2,N-dmba)2(μ-NCO)(μ-pz)] (1), [Pd2(C2,N-dmba)2(μ-NCO)(μ-dmpz)] (2), [Pd(C2,N-dmba)(NCO)(imz)] (3) and [Pd(C2,N-dmba)(NCO)(mimz)] (4), respectively. The compounds were characterized by elemental analysis, IR spectroscopy and TG. The thermal decomposition
of the compounds occurs in three consecutive steps and the final decomposition products were identified as Pd(0) by X-ray
powder diffraction. The thermal stability order of the complexes is 2>3>1>4. 相似文献
16.
Summary An isocratic, reversed-phase liquid chromatographic (LC) method has been developed for the simultaneous determination of azelaic
and benzoic acids in pharmaceutical creams. The compounds were separated on a C18 column (4 μm particles); the mobile phase was methanolwater, 40∶60, containing 10mm ammonium acetate and with the pH adjusted to 5.0. Detection was performed at 220 nm. The method was validated for accuracy,
linearity, precision, and selectivity. Recoveries at levels corresponding to 80% to 120% of the declared content of the creams
ranged from 99.5 to 101.8% and from 100.4 to 102.1% for azelaic and benzoic acids, respectively. The calibration graphs were
linear in the ranges 20–1400 μg mL−1 for azelaic acid (correlation coefficient,r
1>0.99999), and 0.1–7.0 μg mL−1 for benzoic acid (r>0.99998). 相似文献
17.
D. M. Roitershtein K. A. Lyssenko P. A. Belyakov M. Yu. Antipin E. S. Petrov 《Russian Chemical Bulletin》1997,46(9):1590-1594
The reaction of the cyclopentadienyllutetium anthracenide, C5H5Lu(C14H10)2−(THF)2 (1), with azobenzene yielded the [C5H5(THF)Lu(μ−η2:η2−PhN—NPh)]2(THF)2 (2) binuclear complex. The structure of the reaction product was established by X-ray structural analysis. The dynamic behavior
of complex2 in a THF-d8 solution was studied by1H NMR spectroscopy in the temperature range of 265–330 K.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1667–1671, September, 1997. 相似文献
18.
A new adsorbent is proposed for the solid-phase extraction of phenol and 1-naphthol from polluted water. The adsorbent (TX-SiO2) is an organosilica composite made from a bifunctional immobilized layer comprising a major fraction (91%) of hydrophilic
diol groups and minor fraction (9%) of the amphiphilic long-chain nonionic surfactant Triton X-100 (polyoxyethylated isooctylphenol)
(TX). Under static conditions phenol was quantitatively extracted onto TX-SiO2 in the form of a 4-nitrophenylazophenolate ion associate with cetyltrimethylammonium bromide. The capacity of TX-SiO2 for phenol is 2.4 mg g−1 with distribution coefficients up to 3.4 × 104 mL g−1; corresponding data for 1-naphthol are 1.5 mg g−1 and 3 × 103 mL g−1. The distribution coefficient does not change significantly for solution volumes of 0.025–0.5 L and adsorbent mass less than
0.03 g; 1–90 μg analyte can be easily eluted by 1–3 mL acetonitrile with an overall recovery of 98.2% and 78.3% for phenol
and 1-naphthol, respectively. Linear correlation between acetonitrile solution absorbance (A
540) and phenol concentration (C) in water was found according to the equation A
540 = (6 ± 1) × 10−2 + (0.9 ± 0.1)C (μmol L−1) with a detection range from 1 × 10−8 mol L−1 (0.9 μL g−1) to 2 × 10−7 mol L−1 (19 μL g−1), a limit of quantification of 1 μL g−1 (preconcentration factor 125), correlation coefficient of 0.936, and relative standard deviation of 2.5%. A solid-phase colorimetric
method was developed for quantitative determination of 1-naphthol on adsorbent phase using scanner technology and RGB numerical
analysis. The detection limit of 1-naphthol with this method is 6 μL g−1 while the quantification limit is 20 μL g−1. A test system was developed for naked eye monitoring of 1-naphthol impurities in water. The proposed test kit allows one
to observe changes in the adsorbent color when 1-naphthol concentration in water is 0.08–3.2 mL g−1. 相似文献
19.
A. V. Eremin A. N. Belyaev S. A. Simanova 《Russian Journal of Coordination Chemistry》2005,31(11):761-767
Binuclear ruthenium μ-oxocarboxylates of the nonelectrolyte type [Ru
2
III
(μ-O)(μ-O2CR)2Py4(O2CR)2] (R = C(CH3)3, CH3, Ph, CH2Cl, CCl3, and CF3) were obtained and studied by electronic absorption and IR spectroscopy and FAB mass spectrometry. The carboxylate ions RCO
2
−
are symmetrically arranged (trans with respect to the bridging μ-O atom) and coordinated in a monodentate fashion. According to X-ray diffraction data, the
crystals of [Ru
2
III
(μ-O)(μ-O2CCF3)2Py4(O2CCF3)2] ⋅ (CH3)2CO are monoclinic; the unit cell parameters are a = 11.705(2) Å, b = 16.166(3) Å, c = 20.917(4) Å, β = 103.47(3)°, space group C2/c, Z = 4. The RCO
2
−
groups that are trans to the μ-O atom can be easily replaced by pyridine or acetonitrile.
__________
Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 11, 2005, pp. 803–809.
Original Russian Text Copyright ? 2005 by Eremin, Belyaev, Simanova. 相似文献
20.
Solutions of 80 mM benzophenone (BP) and up to 14 mM p-terphenyl (TP) in the ionic liquid methyltributylammonium bis[(trifluoromethyl)sulfonyl]imide
(R4NNTf2) have been investigated by nanosecond pulse radiolysis. The resulting transient absorption spectra of pulse-irradiated argon
saturated solutions correspond to the formation of several intermediates derived from BP and TP: benzophenone radical anion
[(C6H5)2CO]•− (BP•−) converted after ~20 μs into ketyl radicals (C6H5)2C•OH (BP•H), a hydrogen adduct to the phenyl ring of benzophenone C6H5COC6H6•, p-terphenyl triplet excited state 3TP*, and traces of TP radical ions. 3TP* was formed in two steps, the first immediately during the pulse and the second in pseudo-first order process with a second
order reaction rate constant calculated from TP concentration dependence: k = ~2 × 108 dm3 mol−1 s−1. 相似文献