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1.
The present work presents a measurement uncertainty evaluation according to Guide to the Expression of Uncertainty in Measurement (GUM) of the concentration of the cations K+ and Li+ and anions NO3−2 and SO4−2 in fine airborne particulate matter, refers to particles less than 2.5 μm in diameter (PM2.5), as measured by ion chromatography (US-EPA 300 method). The GUM method is not typically used to report uncertainty. In general, the analytical results only report the measurement’s standard deviation under repetition as an uncertainty; thus, not all sources of uncertainty are considered. In this work, the major sources of uncertainty regarding the measurements were identified as contributions to linear least square regression lines, repeatability, precision, and trueness. The expanded uncertainty was approximately 20% for anions and cations. The largest contribution to uncertainty was found to be repeatability.  相似文献   

2.
The structural geometries of three tripodal thiourea receptors, i.e. 1,3,5-triethyl-2,4,6-tris[(N′-methylthioureido)methyl]benzene (1), tris[N′-methyl-N-(2-aminoethyl)thiourea]methane (2), tris[N′-methyl-N-(2-aminoethyl)thiourea]amine (3), and their complexes with F, Cl, Br, I, NO3 , CO3 2−, SO4 2−, HSO4 , PO4 3−, HPO4 2− and H2PO4 were obtained using the density functional theory calculations. Electronic and thermodynamic properties of anion binding complexes of the receptors 1, 2 and 3 were investigated. Recognition abilities of all the receptors in terms of selectivity coefficients are reported. Intermolecular interactions in all the studied complexes occurring via multi-point hydrogen bonding were found. The receptors 1, 2 and 3 were found to be excellent selectivity for phosphate ion and their binding free energy for the phosphate ion are −292.57, −291.77 and −295.01 kcal/mol, respectively.  相似文献   

3.
CeO2-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical devices. This work presents the results of systematic studies of structural and electric properties and oxygen nonstoichiometry of the Ce0.8(Sm1 − x Ca x )0.2O2 − δ system in a wide range of concentrations of 0 < x < 1 performed in order to establish the causes affecting the system conductivity and its behavior in a reducing medium. It is found that a single-phase solid solution of the fluorite type is formed in the whole concentration range. Parameters of its lattice cells decrease linearly at an increase in the concentration of Ca2+. Conductivity in air grows when calcium is added due to a decrease in the grain boundary resistance. The maximum conductivity in air was obtained for the composition of Ce0.8(Sm0.8Ca0.2)0.2O2 − δ and is 13.71 × 10−3 S/cm at 873 K. Studies of the dependence of conductivity of the partial pressure of oxygen showed that electron conductivity is observed at a higher oxygen partial pressure at an increase in the temperature and calcium concentration. The critical partial pressure of oxygen ( pO2 * )\left( {p_{O_2 }^* } \right) for the compositions of Ce0.8(Sm1 − x Ca x )0.2O2 − δ with x = 0; 0.2, and 0.5 is 1.83 × 10−16, 1.73 × 10−13, and 3.63 × 10−13 atm at 1173 K, respectively, and 2.76 × 10−21, 5.05 × 10−18, and 1.31 × 10−18 atm at 1023 K.  相似文献   

4.
The oxidation of low concentration formaldehyde in air over Au/CeO2, prepared by co-precipitation, was investigated. Power-law kinetic models were proposed and the parameters were estimated, which are r = −0.46 × e −14612 / RTCHCHO(303 K < T < 363 K) and r = −295.78 × e −34178 / RT CHCHO (363 K < T < 413 K). The mechanism of the reaction at low temperatures might be different from that at high temperatures.  相似文献   

5.
A series of substituted triphenylphosphane complexes of the type CdL2X2 (L= triorthotolylphosphane or trimetatolylphosphane; X=Cl, Br or I) and HgL2X2 (L=triphenylphosphane or triorthotolylphosphane) was prepared fresh. The thermal decomposition was carried out in air with heating rate programmed at 10°C min−1 and it revealed that the complexes with ortho derivative were less stable and the triphenylphosphane moiety leaves along with halogen in the first step. All the complexes were stable up to 210°C. However, the stability order of the tetrahedral complexes was X=Cl>Br. Values of n, E, lnA and ΔS # have been approximated and compared. Complexes having Br have higher E a, lnA and ΔS # values than that having Cl.  相似文献   

6.
In the time period from June 2005 to May 2006 in 42 sampling campaigns 84 filter samples of airborne particulate matter, coarse (PM10–2.5) and fine (PM2.5), were collected using a Gent stacked filter unit in the coastal industrial area of Aspropyrgos in Attica, Greece. The average PM10 (PM10–2.5 + PM2.5) concentration was found to be 66 μg · m−3, exceeding more than 1.6 times the annual limit of 40 μg · m−3. The samples were analysed for Cl, NO3 , SO4 2−, Ca2+, Mg2+, Na+, K+ and NH4 + using ion chromatography. The data were compared with results obtained with other spectrometric methods, such as inductively coupled plasma-atomic emission spectrometry, atomic absorption spectrometry, energy dispersive X-ray fluorescence and reflectometry. The determined average ionic content comprised about 44% of the PM10 mass. The ionic composition, as well as the possible matrix compounds in both fractions were evaluated by dividing the sampling period into summer and winter season. In the PM10–2.5/PM2.5 fraction in summer time the concentrations of Ca2+, Mg2+ and NO3 were enriched in the coarse fraction. In winter time all species were enriched in the coarse fraction, especially Ca2+, Cl and NO3 . NH4 + was constantly higher in the fine fraction in summer as well as in winter time. Factor analysis was applied to obtain correlations between cations and anions leading to matrix compounds in both fractions. From the evaluation of the results obtained, some of the local air pollution sources could be identified. Correspondence: Klaus-Michael Ochsenkühn, Laboratory for Trace Element Studies, Institute of Physical Chemistry, NCSR “Demokritos”, Aghia Paraskevi 15310, Athens, Greece  相似文献   

7.
The kinetics of the electron-transfer reactions between promazine (ptz) and [Co(en)2(H2O)2]3+ in CF3SO3H solution ([CoIII] = (2–6) × 10−3 m, [ptz] = 2.5 × 10−4 m, [H+] = 0.02 − 0.05 m, I = 0.1 m (H+, K+, CF3SO 3 ), T = 288–308 K) and [Co(edta)] in aqueous HCl ([CoIII] = (1 − 4) × 10−3 m, [ptz] = 1 × 10−4 m, [H+] = 0.1 − 0.5 m, I = 1.0 m (H+, Na+, Cl), T = 313 − 333 K) were studied under the condition of excess CoIII using u.v.–vis. spectroscopy. The reactions produce a CoII species and a stable cationic radical. A linear dependence of the pseudo-first-order rate constant (k obs) on [CoIII] with a non-zero intercept was established for both redox processes. The rate of reaction with the [Co(en)2(H2O)2]3+ ion was found to be independent of [H+]. In the case of the [Co(edta)] ion, the k obs dependence on [H+] was linear and the increasing [H+] accelerates the rate of the outer-sphere electron-transfer reaction. The activation parameters were calculated as follows: ΔH = 105 ± 4 kJ mol−1, ΔS = 93 ± 11 J K−1mol−1 for [Co(en)2(H2O)2]3+; ΔH = 67 ± 9 kJ mol−1, ΔS = − 54 ± 28 J K−1mol−1 for [Co(edta)].  相似文献   

8.
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   

9.
There is a lack of fundamental knowledge about the scale up of biosurfactant production. In order to develop suitable technology of commercialization, carrying out tests in shake flasks and bioreactors was essential. A reactor with integrated foam collector was designed for biosurfactant production using Bacillus subtilis isolated from agricultural soil. The yield of biosurfactant on biomass (Y p/x), biosurfactant on sucrose (Y p/s), and the volumetric production rate (Y) for shake flask were obtained about 0.45 g g−1, 0.18 g g−1, and 0.03 g l−1 h−1, respectively. The best condition for bioreactor was 300 rpm and 1.5 vvm, giving Y x/s, Y p/x, Y p/s, and Y of 0.42 g g−1, 0.595 g g−1, 0.25 g g−1, and 0.057 g l−1 h−1, respectively. The biosurfactant maximum production, 2.5 g l−1, was reached in 44 h of growth, which was 28% better than the shake flask. The obtained volumetric oxygen transfer coefficient (K L a) values at optimum conditions in the shake flask and the bioreactor were found to be around 0.01 and 0.0117 s−1, respectively. Comparison of K L a values at optimum conditions shows that biosurfactant production scaling up from shake flask to bioreactor can be done with K L a as scale up criterion very accurately. Nearly 8% of original oil in place was recovered using this biosurfactant after water flooding in the sand pack.  相似文献   

10.
The radiation chemical redox transformations in solutions of bromides in the presence of minor additives of iodides were studied by pulse radiolysis. The change in the concentrations of the Br and I ions changes the ratio of the formed short-lived radical anions Br2 ·−, BrI·−, and I2 ·−. The spectrum of the mixed radical anion BrI·− contains a broad optical band at 370 nm with ɛ370 = 9650 L mol−1 cm−1. The reduction potential of the BrI·−/Br, I pair is 1.25 V. The rate constants for the forward and backward reactions Br2 ·− + I ⇌ BrI·− + Br are k f = 4.3·109 and k r = 1.0·105 L mol−1 s−1, respectively; for the reactions BrI·− ⇌ Br + I·, k f = 5.7·108 s−1 and k r = 1.0·1010 L mol−1 s−1. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1787–1792, September, 2008.  相似文献   

11.
Nonempirical methods are used to calculate the geometric parameters, the frequencies of normal vibrations, and thermochemical characteristics of ions existing in saturated vapors over sodium bromide and iodide: Na2X+, NaX2, Na3X2+, and Na2X3 (X = Br, I). According to the calculations, Na2X+ and NaX2 triatomic ions have a linear equilibrium configuration of D h symmetry. Pentaatomic ions can exist in the form of three isomers: linear with D h symmetry, planar cyclic with C 2v symmetry, and bipyramidal with D 3h symmetry. At a temperature of ∼1000 K, Na3X2+ and NaX3 pentaatomic ions are shown to be present in vapor mainly in the form of linear isomers. The energies and enthalpies of ion molecular reactions with the participation of the above ions are calculated, and the formation enthalpies of the ions are determined, Δ f H o(0 K): 293±2 kJ/mol (Na2Br+), 354±2 kJ/mol (Na2I+), −536±2 kJ/mol (NaBr2, −458±2 kJ/mol (NaI2, 24±5 kJ/mol (Na3Br2+, 143±5 kJ/mol (Na3I2+, −810±5 kJ/mol (Na2Br3, and −675±5 kJ/mol (Na2I3.  相似文献   

12.
The protonation constants for oxidized glutathione, H i−1L(4−i+1)−, K i H=[H i L(4−i)−]/[H i−1L(4−i+1)−][H+] i=1,2,…,6 have been measured at 5, 25 and 45 °C as a function of the ionic strength (0.1 to 5.4 mol⋅[kg(H2O)]−1) in NaCl solutions. The effect of ionic strength on the measured protonation constants has been used to determine the thermodynamic values (K i H0) and the enthalpy (ΔH i ) for the dissociation reaction using the SIT model and Pitzer equations. The SIT (ε) and Pitzer parameters (β (0), β (1) and C) for the dissociation products (L4−, HL3−, H2L2−, H3L, H4L, H5L+, H6L2+) have been determined as a function of temperature. These results can be used to examine the effect of ionic strength and temperature on glutathione in aqueous solutions with NaCl as the major component (body fluids, seawater and brines).  相似文献   

13.
Heat capacity and enthalpy increments of calcium niobates CaNb2O6 and Ca2Nb2O7 were measured by the relaxation time method (2–300 K), DSC (260–360 K) and drop calorimetry (669–1421 K). Temperature dependencies of the molar heat capacity in the form C pm=200.4+0.03432T−3.450·106/T 2 J K−1 mol−1 for CaNb2O6 and C pm=257.2+0.03621T−4.435·106/T 2 J K−1 mol−1 for Ca2Nb2O7 were derived by the least-squares method from the experimental data. The molar entropies at 298.15 K, S m0(CaNb2O6, 298.15 K)=167.3±0.9 J K−1 mol−1 and S m0(Ca2Nb2O7, 298.15 K)=212.4±1.2 J K−1 mol−1, were evaluated from the low temperature heat capacity measurements. Standard enthalpies of formation at 298.15 K were derived using published values of Gibbs energy of formation and presented heat capacity and entropy data: Δf H 0(CaNb2O6, 298.15 K)= −2664.52 kJ molt-1 and Δf H 0(Ca2Nb2O7, 298.15 K)= −3346.91 kJ mol−1.  相似文献   

14.
The formation of mixed-ligand complexes HgEdtaIm2−, HgEdtaL3−, HgEdtaHL2−, and (HgEdta)2L5− (L is histidine, lysine; Im is imidazole) was studied by calorimetry, pH-metry, and NMR spectroscopy. The thermodynamic parameters (logK, ΔrG 0, ΔrH, Δr S) for the reactions of complex formation at 298.15 K and ion strength of 0.5 (KNO3) were determined. The most likely coordination mode for the complexone and amino acid in the mixed complexes was identified.  相似文献   

15.
3,3-Dinitroazetidinium (DNAZ) salt of perchloric acid (DNAZ·HClO4) was prepared, it was characterized by the elemental analysis, IR, NMR, and a X-ray diffractometer. The thermal behavior and decomposition reaction kinetics of DNAZ·HClO4 were investigated under a non-isothermal condition by DSC and TG/DTG techniques. The results show that the thermal decomposition process of DNAZ·HClO4 has two mass loss stages. The kinetic model function in differential form, the value of apparent activation energy (E a) and pre-exponential factor (A) of the exothermic decomposition reaction of DNAZ·HClO4 are f(α) = (1 − α)−1/2, 156.47 kJ mol−1, and 1015.12 s−1, respectively. The critical temperature of thermal explosion is 188.5 °C. The values of ΔS , ΔH , and ΔG of this reaction are 42.26 J mol−1 K−1, 154.44 kJ mol−1, and 135.42 kJ mol−1, respectively. The specific heat capacity of DNAZ·HClO4 was determined with a continuous C p mode of microcalorimeter. Using the relationship between C p and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic time-to-explosion) was evaluated as 14.2 s.  相似文献   

16.
The ability of new synthetic receptors, i.e., p-tert-butylthiacalix[4]arenes tetrasubstituted at the lower rim and containing secondary amide groups to form complexes with a number of spherical (F, Cl, Br, I), Y-shaped (MeCOO), trigonal (NO3 ), and tetrahedral (H2POO4 ) anions has been studied. It was shown that the nature of substituents on the nitrogen atom of the amide groups and configuration of the macrocycle affect the stability constant values of the forming complexes.  相似文献   

17.
Formations of active species and by-products are different from bubbling different gases in a pulsed high-voltage discharge reactor. The identification of all the products and the formation rate determination of active species are quite important as the process is applied to wastewater disposal. Serials of measurements were conducted to do the identifications and determinations in this paper. Amounts of · OH all increased but that of H2O2 all decreased by bubbling gas. The · OH formation rate was 3.49 × 10−7, 3.56 × 10−7, 3.21 × 10−7 and 1.94 × 10−7 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen respectively, but it was 1.61 × 10−7 mol s−1 l−1 without bubbling. Without any bubbling, the H2O2 formation rate was up to 6.53 × 10−6 mol l−1 s−1, while it was 9.97 × 10−7, 1.663 × 10−7, 1.73 × 10−6 and 3.14 × 10−6 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen, respectively. NO2 and NO3 was detected in discharged water with bubbling nitrogenous gas. Their formation made the pH decreased.  相似文献   

18.
Two new heterotrinuclear FeIII-MII-FeIII oxalate-bridged complexes have been prepared, and characterized, namely MII[(ox)FeIII(Salen)]2, [Salen = N,N′-ethylenebis(salicylideneiminate), ox = oxalate, M = Cu (1) and VO (2)]. Based on elemental analysis, conductivity measurements and i.r. spectra, the complexes are proposed to have an oxalate-bridged structure. The magnetic susceptibilities of the complexes were measured over the 4.2–300 K range, giving the exchange integrals J AB = −4.23 cm−1, J AA = −2.47 cm−1 for (1) and J AB = −5.42 cm−1, J AA = −1.55 cm−1 for (2). These results revealed the operation of an antiferromagnetic spin-exchange interaction between the metal ions. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

19.
The study on thermodynamics of ion exchange equilibrium for uni-univalent Cl/I, Cl/Br, and uni-divalent Cl/SO42−, Cl/C2O42− reaction systems was carried out using ion-exchange resin Duolite A-113. The equilibrium constant K was calculated by taking into account the activity coefficient of ions both in solution as well as in the resin phase. The K values calculated for uni-univalent and uni-divalent anion exchange reaction systems were observed to increase with rise in temperature, indicating the endothermic exchange reactions having enthalpy values of 17.21, 36.60, 19.50, 18.43 kJ/mol respectively.  相似文献   

20.
Passive air sampling was undertaken using polyurethane foam passive air samplers at three types of locations, including indoors (six offices) at buildings in the central business district (CBD) and at a private suburban home (indoor and outdoor) located 9 km from the CBD in Brisbane, Queensland, Australia. Estrogenic (E-SCREEN—MCF7-BOS) and aryl hydrocarbon receptor (AhR) (CAFLUX—H4G1.1c2) activity were assessed for samples collected from each of these locations. The samples were tested either as crude extracts (“untreated”) or were subjected to H2SO4 silica gel (“treated”) for each location in order to determine whether chemicals, which are not resistant to this treatment like polycyclic aromatic hydrocarbons, potentially account for the observed activity. In most cases, H2SO4 treatment resulted in a statistically significant reduction of potency for both endpoints, suggesting that chemicals less resistant to treatment may be responsible for much of the detected biological activity in these locations. Estrogenic potency measurements (<0.22–185 pg m−3) were highest in the indoor offices, followed by the indoor suburban home and finally the outdoor suburban home (which was not estrogenic). Total AhR activity for crude extracts (1.3–10 pg m−3) however was highest for the outdoor suburban home site. Levels of polycyclic aromatic hydrocarbons were monitored indoors and outdoors at the suburban home. At that location, polycyclic aromatic hydrocarbon air concentrations were on average approximately two times higher outdoor than indoor, while AhR potency was five times higher outdoor than indoor. No significant correlation was found between the estrogenic and AhR activity (P = 0.88) for the sites in this study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

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