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1.
Laboratory measurements of gas-phase ion-molecule reactions of several negative ion species with formic and acetic acid have been carried out. A flow reactor operating at a temperature of 293 ± 3 K and total gas pressures of either 3 or 9 hPa was used. The negative reagent ion species investigated included OH, O2, O3, CO4, CO3, CO3H2O, HCO3H2O, NO3, NO3H2O, NO2, and NO2H2O. The reactions were found to proceed either via proton transfer or clustering. Our measurements of ion-molecule reactions of negative ions with gaseous formic and acetic acids provide a firm base for quantitative detection of these acidic trace gases in the atmosphere by negative ion ion-molecule reaction mass spectrometry.  相似文献   

2.
TiO2 photocatalytic mineralization of β-naphthol: influence of some inorganic ions, ethanol, and hydrogen peroxide. In this work, the photocatalytic oxidation of β-naphthol in aqueous suspensions of TiO2 was investigated at room temperature, by following the formation of CO2. The disappearance of β-naphthol fits a Langmuir-Hinshelwood kinetic model. The activation energy for the degradation reaction of β-naphthol is estimated at 10.2 kJ/mol. The effects of some additives such as ethanol, H2O2, and inorganic ions (Cl, SO42−, HCO3, NO3, Fe3+, Cu2+, and Cr3+) on the photomineralization of β-naphthol were examined. The inhibition of the anions for this reaction was in the order : NO3 < HCO3 < SO42− < Cl. This can be due to a partial blockage of catalyst active sites by these ions or their reaction with an oxidizing radical such as OH. The most photoactive systems for β-naphthol degradation were found in the presence of ferric ions, while the addition of Cr3+ strongly inhibited the photocatalytic decomposition of β-naphthol.  相似文献   

3.
The interaction between negative atmospheric ions and various types of organic compounds were investigated using atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. Atmospheric negative ions such as O2, HCO3, COO(COOH), NO2, NO3, and NO3(HNO3) having different proton affinities served as the reactant ions for analyte ionization in APCDI in negative-ion mode. The individual atmospheric ions specifically ionized aliphatic and aromatic compounds with various functional groups as atmospheric ion adducts and deprotonated analytes. The formation of the atmospheric ion adducts under certain discharge conditions is most likely attributable to the affinity between the analyte and atmospheric ion and the concentration of the atmospheric ion produced under these conditions. The deprotonated analytes, in contrast, were generated from the adducts of the atmospheric ions with higher proton affinity attributable to efficient proton abstraction from the analyte by the atmospheric ion.  相似文献   

4.
A chemiluminescence (CL) method for the determination of humic acid (HA) based on the oxidation of HA with hydrogen peroxide in the presence of formaldehyde in alkaline solution is described. This method is sensitive and selective for the determination of HA in natural water. HA produces strong CL in the oxidation of HA with MnO4, Br2, ClO, and Cr2O72−, and the H2O2. HA-H2O2-HCHO system is suitable for the determination of HA because of its high sensitivity and high selectivity. The detection limit was 50 ppb and relative standard deviation for five measurements of 0.5 ppm (w/w) HA was 1.8%. Cations such as Na+, K+, Mg2+, Cu2+, and Fe3+ and anions such as PO43−, NO3, CO32−, SO42−, Cl, and Y (EDTA-Na) did not interfere with the determination of HA. Addition of Mn(II) increased the CL intensity. The concentration of HA in natural water determined with this method is in good agreement with that determined by fluorometric analysis.  相似文献   

5.
The rate constants and product ion branching ratios were measured for the reactions of various small negative ions with O2(X 3Σg) and O2(a 1Δg) in a selected ion flow tube (SIFT). Only NH2 and CH3O were found to react with O2(X) and both reactions were slow. CH3O reacted by hydride transfer, both with and without electron detachment. NH2 formed both OH, as observed previously, and O2, the latter via endothermic charge transfer. A temperature study revealed a negative temperature dependence for the former channel and Arrhenius behavior for the endothermic channel, resulting in an overall rate constant with a minimum at 500 K. SF6, SF4, SO3 and CO3 were found to react with O2(a 1Δg) with rate constants less than 10−11 cm3 s−1. NH2 reacted rapidly with O2(a 1Δg) by charge transfer. The reactions of HO2 and SO2 proceeded moderately with competition between Penning detachment and charge transfer. SO2 produced a SO4 cluster product in 2% of reactions and HO2 produced O3 in 13% of the reactions. CH3O proceeded essentially at the collision rate by hydride transfer, again both with and without electron detachment. These results show that charge transfer to O2(a 1Δg) occurs readily if the there are no restrictions on the ion beyond the reaction thermodynamics. The SO2 and HO2 reactions with O2(a) are the only known reactions involving Penning detachment besides the reaction with O2 studied previously [R.S. Berry, Phys. Chem. Chem. Phys., 7 (2005) 289–290].  相似文献   

6.
N,N,N,N-tetrabutylmalonamide (TBMA) was synthesized and used for extraction of uranyl(II) ion from nitric acid media in toluene. The effects of nitric acid concentration, extractant concentration, temperature and salting-out agent (LiNO3) on distribution coefficients of uranyl(II) ion have been studied. The extraction of nitric acid is also studied. The main adduct of TBMA and HNO3 is HNO3. TBMA in 1.0 mol/l nitric acid solution. The 1:2:3 complex of uranyl(II) ion, nitrate ion and TBMA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBMA, and found that the NO 3 in the extraction species UO2(NO3)2·3TBMA did not participate in coordination of uranyl(II) ion. The values of thermodynamic parameters have also been calculated.  相似文献   

7.
Approximately 40 ions have been chromatographed on thin layers of silica gel impregnated with Alamine 336-S, Alamine 336-S oxide, tri-n-octylarsine oxide, tri-n-octylphosphine oxide or tri-n-butyl phosphate, and on non-impregnated silica gel. Solutions of 0.2–15 N HNO3 are used as eluants. RF spectra and a number of separations are reported. The ions are classified into four groups according to their chromatographic behaviour, which is explained on the basis of anion exchange, solvation, hydrolysis and interaction with the support.Data on the extraction of HNO3 and the co-extraction of water are reported. The behaviour of Alamine oxide and tri-n-octylarsine oxide parallels that of high-molecular-weight amines: extraction proceeds through anion exchange. Nitric acid taken up in excess of the stoichiometric amount is mainly present in the organic phase as part of the ion [O2NO…HONO2]. On the other hand, with tri-n-octyl-phosphine oxide (TOPO) and tri-n-butyl phosphate (TBP), extraction proceeds through solvation; TOPO·HNO3, TOPO·2HNO3 and TBP·HNO3 are the species present in the organic extracts.  相似文献   

8.
This paper describes how weakly bound adduct ions form when the precursor ions used in selected ion flow mass spectrometry, SIFT-MS, analyses, viz. H3O+, NO+ and O2+, associate with the major components of air and exhaled breath, N2, O2 and CO2. These adduct ions, which include H3O+N2, H3O+CO2, NO+CO2, O2+O2 and O2+CO2, are clearly seen when dry air containing 5% CO2 (typical of that in exhaled breath) is analysed using SIFT-MS. These adduct ions must not be misinterpreted as characteristic product ions of trace gases; if so, serious analytical errors can result. However, when exhaled breath is analysed these adduct ions are partly removed by ligand switching reactions with the abundant water molecules and the problems they represent are alleviated. But the small fractions of the adduct ions that remain in the SIFT-MS spectra, and especially when they are isobaric with genuine characteristic product ion of breath trace gases, can result in erroneous quantifications; such is the case for H3O+N2 interfering with breath ethanol analysis and H3O+CO2 with breath acetaldehyde analysis. However, these difficulties can be overcome when the isobaric adduct ions are properly recognised and excluded from the analyses; then these two important compounds can be properly quantified in breath. The presence of O2+CO2 in the product ion spectra interferes with the analysis of CS2 present at low levels in exhaled breath. It is likely that similar problems will occur as other trace compounds are detected in exhaled breath when consideration will have to be given to the possibility of overlapping between their characteristic product ions and ions produced by hitherto unknown reactions. Similar problems are evident in other systems; for example, H3O+CH4 adduct ions are observed in both SIFT-MS analyses of methane rich mixtures like biologically generated waste gases and in model planetary atmospheres.  相似文献   

9.
Through a combination of Raman spectroscopy, multi-element NMR spectroscopy and chemical analysis, the differences between the action of carbonate and carbamate as agents for dissolving Cs3PMo12O40xH2O(s) (CPM) and ZrMO2O7(OH)2(H2O)2(s) (ZM) have been elucidated. Alkaline H2NCO2/HCO3/CO32− solutions, derived from the dissolution of ammonium carbamate (NH4H2NCO2; AC), dissolve CPM by base hydrolysis of the PMo12O403− Keggin anion, ultimately forming [MoO4]2− and PO43− when excess base is present. If the initial concentration of H2NCO2/HCO3/ CO32− is lowered, base hydrolysis is incomplete and the dissolved species include [Mo7O24]6− and [P2Mo5O23]6−, and undissolved solid Cs3PMo12O40, CsxNH7−xPMo11O39, and CsxNH6−xMo7O24 remain. Na2CO3 solutions dissolve Cs3PMo12O40 through a similar mechanism, but the dissolution rate is much lower. We attribute this difference to the different buffering effects of H2NCO2/HCO3/CO32− and CO32−/HCO3 solutions, and the instability of carbamic acid, the protonated form of H2NCO2 (which rapidly decomposes into NH3 and CO2). The ability of NH3 to produce NH4+ and OH, together with the evolution of CO2 gas, drive the reaction forward. Low temperature measurements under conditions where pure H2NCO2 is kinetically stable, allowed the rates of dissolution of CPM by H2NCO2 and CO32− to be compared directly, confirming the faster dissolution by H2NCO2. Compared to CPM, the dissolution of ZM by H2NCO2/HCO3/CO32− is a much slower process and is driven by the formation of soluble ZrIV-carbonate complexes and MoO42−. The driving force for the dissolution of ZM is the superior complexing ability of carbonate over carbamate; consequently solutions containing a higher carbonate concentration dissolve ZM faster.  相似文献   

10.
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   

11.
The thermal decomposition of trifluoromethoxycarbonyl peroxy nitrate, CF3OC(O)O2NO2, has been studied between 278 and 306 K at 270 mbar total pressure using He as a diluent gas. The pressure dependence of the reaction was also studied at 292 K between 1.2 and 270 mbar total pressure. The rate constant reaches its high‐pressure limit at 70 mbar. The first step of the decomposition leads to CF3OC(O)O2 and NO2 formation, that is, CF3OC(O)O2NO2 + M ? CF3OC(O)O2 + NO2 + M (k1, k?1). Reaction (?1) was prevented by adding an excess of NO that reacts with the peroxy radical intermediate and leads to carbonyl fluoride (CF2O), carbon dioxide (CO2), nitrogen dioxide (NO2), and small quantities of CF3OC(O)O2C(O)OCF3. The kinetics of reaction (1) was determined by following the loss of CF3OC(O)O2NO2 via IR spectroscopy. The temperature dependence of the decomposition follows the equation k1(T) = 1.0 × 1016 e?((111±3)/(RT)) for the exponential term expressed in kJ mol?1. The values obtained for the kinetic parameters such as k1 at 298 K, the activation energy (Ea), and the preexponential factor (A) are compared with literature data for other acyl peroxy nitrates. The atmospheric thermal stability of CF3OC(O)O2NO2 and its dependence with altitude is discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 831–838, 2008  相似文献   

12.
This work presents alternatives for Fe and Co determination in pharmaceutical samples using flow analysis. The first procedure describes Fe extraction in mineral/vitamin complexes. The best conditions were reached when HNO3 concentration and volume, sample mass and shaking time were 1.0 mol l−1, 5 ml, 25 mg and 10 min. Three mineral/vitamin complexes of known concentrations (ranging from 12 to 32 g kg−1) were analyzed (10 authentic replicates for each) and recoveries of around 100% were obtained when compared with a well-established mineralization procedure employing concentrated HNO3 and H2O2 (30% w/v). The second work part shows the employment of Tiron and H2O2 reaction for Co determination in a drug for inappetence. The results (352±18.7 mg kg−1) were compared with those using Electrothermal Atomic Absorption Spectrometry—ETAAS (346±15.7 mg kg−1). The proposed method showed detection and quantification limits of 0.20 and 0.70 μg l−1, respectively. Both procedures for Fe and Co determination presented time, reagent and effort reduction.  相似文献   

13.
The rate of nitrogen isotope exchange between NO and HNO3 has been measured as a function of nitric acid concentration of 1.5–4M·1–1. The exchange rate law is shown to beR=k[HNO3]2[N2O3] and the measured activation energy isE=67.78kJ ·M–1 (16.2 kcal·M–1). It is concluded that N2O3 participates in15N/14N exchange between NO and HNO3 at nitric acid concentrations higher than 1.5M·1–1.  相似文献   

14.
The gas-phase reactions of O . (H2O)n and OH(H2O)n, n=20–38, with nitrogen-containing atmospherically relevant molecules, namely NOx and HNO3, are studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and theoretically with the use of DFT calculations. Hydrated O . anions oxidize NO . and NO2 . to NO2 and NO3 through a strongly exothermic reaction with enthalpy of −263±47 kJ mol−1 and −286±42 kJ mol−1, indicating a covalent bond formation. Comparison of the rate coefficients with collision models shows that the reactions are kinetically slow with 3.3 and 6.5 % collision efficiency. Reactions between hydrated OH anions and nitric oxides were not observed in the present experiment and are most likely thermodynamically hindered. In contrast, both hydrated anions are reactive toward HNO3 through proton transfer from nitric acid, yielding hydrated NO3. Although HNO3 is efficiently picked-up by the water clusters, forming (HNO3)0–2(H2O)mNO3 clusters, the overall kinetics of nitrate formation are slow and correspond to an efficiency below 10 %. Combination of the measured reaction thermochemistry with literature values in thermochemical cycles yields ΔHf(O(aq.))=48±42 kJ mol−1 and ΔHf(NO2(aq.))=−125±63 kJ mol−1.  相似文献   

15.
The effects of CO complexation on highly exothermic vanadium oxidation reactions is evaluated. We study the chemiluminescent (CL) reaction products formed when vanadium vapor entrained in Ar or CO is oxidized by O3 or NO2. The multiple collision V+Ar+O3→VO*(C 4Σ, 4Φ, 2X)+Ar+O2 reactive encounter yields two previously unreported VO excited states, whereas the V+Ar+NO2→VO*+Ar+NO reactive encounter populates states up to and including VO* C 4Σ. The multiple collision V+nCO+O3 reactive encounter would appear to form a VOCO excited state complex, emitting in the region 420–560 nm, via the formation and oxidation of V(CO)2 viz. V(CO)2+O3→VOCO*+CO+O2 and a relaxed VO excited state emitter via V+nCO+O3→VO*+nCO+O2 where the VO excited state excitation is mediated by V–CO complexation. In complement, the much less exothermic V–NO2 encounter displays an emission which, in concert with previous studies of CO complexation, suggests the formation of a VO(CO)2 excited state complex viz. V(CO)2+NO2→VO(CO)2*+NO. The experiments characterizing CL are complemented by comparative laser-induced fluorescence studies of the VO X 4Σ–CO and Ar interactions and their influence on the VO C 4Σ–X 4Σ laser-induced excitation spectrum. These studies, in conjunction with further attempts to excite LIF in the 420–560 nm region, suggest that the observed complex emissions result primarily from VO excited state interactions. Complementary time-of-flight mass spectroscopy of vanadium and vanadium-oxide–carbonyl complex formation demonstrates the formation of V(CO), V(CO)2, V2(CO), and VOCO, the latter three of which demonstrate clear metastable-ion dissociation peaks for the processes VOCO+→V++CO2, V(CO)2+→V++2CO, and V2(CO)+→V2++CO, suggesting that these vanadium complexes when formed in a reaction-based environment may be photodissociated with light in the visible and ultraviolet regions.  相似文献   

16.
Summary The kinetics of the reaction between nitrous acid and gold(III) in an HCl medium was studied. The reaction was first order with respect to [AuIII] and [HNO2]·H+ and Cl- ions inhibit the rate and alkali metal ions have specific effects on the rate. The reaction appears to involve different gold(III) species, viz. AuCl inf4 sup– , AuCl3(OH2) and AuCl3(OH), which undergo a two-equivalent reduction to gold(I) leading to the formation of NO inf2 sup&#x002B; which under-goes rapid hydrolysis to give nitric acid.  相似文献   

17.
The potential energy surface for the reaction of the CF3O radicals with CO was investigated. The geometries and vibrational frequencies of the reactants, transition states, intermediates, and products were calculated at the UB3LYP/6-311+G(2d,p), UB3LYP/6-311+G(3df,2p) and UMP2/6-311+G(2d,p) levels of theory. The energies were improved by using the G2M(CC2) and G3B3 methods. The calculation suggests the reaction proceeds via either the fluorine abstraction of CF3O by CO to produce FCO + CF2O with a high energy barrier or the barrierless association of the reactants to form the trans-CF3OCO intermediate. The trans-CF3OCO is predicted to undergo subsequent isomerization to cis-CF3OCO or dissociate directly to the products FCO + CF2O and CF3 + CO2. The collisional stabilization of trans-CF3OCO is dominant at room temperature, while trans-CF3OCO isomerizing to cis-CF3OCO followed by dissociating to CF3 + CO2 is accessible when temperature rises. The reason for only trans-CF3OCO without cis-CF3OCO observable in Ashen’s experiment [S.V. Ahsen, J. Hufen, H. Willner, J.S. Francisco, Chem. Eur. J. 8 (2002) 1189] is cis-CF3OCO can be produced only via the isomerization of trans-CF3OCO, and its yield is inappreciable at a low experimental temperature. The enthalpies of formation for the two conformations of CF3OCO have been deduced: (trans-CF3OCO) = −196.25 kcal mol−1, (trans-CF3OCO) = −197.46 kcal mol−1, (cis-CF3OCO) = −193.64 kcal mol−1, and (cis-CF3OCO) = −194.90 kcal mol−1.  相似文献   

18.
Freshly deposited discharge-produced tetrafluoroethylene films were ion-etched with either helium, neon, argon, oxygen or hydrogen. The ions C+, CF+, CF2+ and CF3+ comprised most of the positive ions in rare gas discharges, with CF+ always dominant. Sputtered fragments containing two or more carbon atoms were rare. These findings are compatible with the ion-etching of a highly crosslinked polymer film. Residual background gases were contributed to 1–3% of the total ion flux even though their actual partial pressures were very low. The concentration of neutral species corresponding to the ions observed was less than one part in ten thousand of the etching gas. With pure hydrogen, very little etching occurred and the degree of ionization relative to the rare gases was low. The principal reaction was the abstraction of fluorine from the polymer to give hydrogen fluoride and a more highly crosslinked film. Oxygen containing discharges produced the largest total yield of all the systems studied and the most evidence of chemical attack on the polymer. The ions observed were CO+, CO2+, COF+, COF2+ as well as C+, CF+, CF2+ and CF3+. Thus oxygen etches the polymer by preferentially attacking the carbon-carbon framework.  相似文献   

19.
Photodissolution tests of UO2 sintered pellets were carried out in 3M nitric acid solution and at about 50 °C under UV irradiation. The light source was a Hg-lamp emitting a light of 254nm wavelength. In the products, chemicals such as H2O2 and NO2 ion were detected during photodissolution of the UO2 sintered pellets. Based on this result, a new dissolution mechanism of UO2 in nitric acid solution by photochemical reaction was suggested in this study.  相似文献   

20.
Sorption behaviour of monovalent Rb+, Tl+ and Ag+ is studied on chromium fericyanide gel. Log Kd vs log concentration plots show that Rb+ and Tl+ are sorbed through ion exchange mechanism in a higher concentration range of ammonium nitrate or nitric acid, whereas the adsorption of Ag+ is irreversible. It was found possible to elute Rb+ and Tl+ on the columns of this gel by 4 mol dm−3 NH4NO3 and 10 mol dm−3 HNO3, respectively. Binary separations of Rb+ and Tl+ from a number of other metal ions were achieved as other ions were found practically unadsorbed on these columns and were eluted with water of pH 2–3. Achieved separations are of radioanalytical and analytical importance.  相似文献   

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