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1.
We have studied the behavior of isomers and analogues by traveling wave ion mobility mass spectrometry (TWIM‐MS) using drift‐gases with varying masses and polarizabilities. Despite the reduced length of the cell (18 cm), a pair of constitutional isomers, N‐butylaniline and para‐butylaniline, with theoretical collision cross‐section values in helium (ΩHe) differing by as little as 1.2 Å2 (1.5%) but possessing contrasting charge distribution, showed baseline peak‐to‐peak resolution (Rp‐p) for their protonated molecules, using carbon dioxide (CO2), nitrous oxide (N2O) and ethene (C2H4) as the TWIM drift‐gas. Near baseline Rp‐p was also obtained in CO2 for a group of protonated haloanilines (para‐chloroaniline, para‐bromoaniline and para‐iodoaniline) which display contrasting masses and theoretical ΩHe, which differ by as much as 15.7 Å2 (19.5%) but similar charge distributions. The deprotonated isomeric pair of trans‐oleic acid and cis‐oleic acid possessing nearly identical theoretical ΩHe and ΩN2 as well as similar charge distributions, remained unresolved. Interestingly, an inversion of drift‐times were observed for the 1,3‐dialkylimidazolium ions when comparing He, N2 and N2O. Using density functional theory as a means of examining the ions electronic structure, and He and N2‐based trajectory method algorithm, we discuss the effect of the long‐range charge induced dipole attractive and short‐range Van der Waals forces involved in the TWIM separation in drift‐gases of differing polarizabilities. We therefore propose that examining the electronic structure of the ions under investigation may potentially indicate whether the use of more polarizable drift‐gases could improve separation and the overall success of TWIM‐MS analysis. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

2.
Traveling wave ion mobility mass spectrometry (TWIM‐MS) is shown to be able to separate and characterize several isomeric forms of diterpene glycosides stevioside (Stv) and rebaudioside A (RebA) that are cationized by Na+ and K+ at different sites. Determination and characterization of these coexisting isomeric species, herein termed catiomers, arising from cationization at different and highly competitive coordinating sites, is particularly challenging for glycosides. To achieve this goal, the advantage of using CO2 as a more massive and polarizable drift gas, over N2, was demonstrated. Post‐TWIM‐MS/MS experiments were used to confirm the separation. Optimization of the possible geometries and cross‐sectional calculations for mobility peak assignments were also performed. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

3.
Ion mobility coupled with mass spectrometry provides a fast and repeatable method to separate catechin epimers by previous complexation with selected chiral modifiers and transition metals. Several combinations with chiral ligands such as D‐ and L‐amino acids and/or additional metal cations, chiral crown ethers, tartaric acid and heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin were screened for their ability to affect the separation efficiency. The clusters having the form of [2M + D‐amino acid + Cu2+ ? 3H]? (M stands for (?)‐epicatechin or (+)‐catechin) showed improvement in stereodifferentiation between two epimeric catechins in comparison to the analysis of pure epimers, where no separation was observed or the separation was hampered by the formation of mixed dimer complexes. Among various examined D‐amino acids only those possessing hydrophobic side chains induced the improvement of separation efficiency. The best peak‐to‐peak resolution (Rp–p) was determined to be 0.71 for [2M + D‐Leucine + Cu2+ ? 3H]? clusters. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

4.
《Electroanalysis》2017,29(4):965-974
A novel non‐enzymatic carbohydrates sensor which was an indium tin oxide (ITO) glass electrode modified by nickel and copper nanoparticles (Cu/Ni/ITO) was developed by an electrochemical method. The crystallinity, morphology, electrochemical measurements and amperometric response of the as‐prepared ITO modified electrode were examined by the X‐ray diffraction (XRD), scanning electron microscopic (SEM), cyclic voltammetry (CV) and chronoamperometry, respectively. The Cu/Ni/ITO electrode had better electroactivity for glucose oxidation than that obtained using Cu/ITO, Ni/ITO, and Ni/Cu/ITO. The logistic regression equation, Ipa = (A 1A 2)/[1 + (Cglucose /x 0)p ] + A 2, was used to fit the calibration curves of glucose aqueous solution concentrations and responsive current intensity. In research of other saccharides, such as fructose, lactose, sucrose, and maltose, which were detected by the Cu/Ni/ITO electrode, it was obvious that the Cu/Ni/ITO electrode was more sensitive to monosaccharides than disaccharides. Monosaccharides and disaccharides can be detected because the saccharides themselves had aldehyde group or be isomerized to an isomer having an aldehyde group in alkaline environment, and then aldehyde group produced carboxylic acid in the catalytic oxidation of the electrode, which lead to the change of electrode surface conductivity and the appearance of oxidation peak, and the alkaline environment further promotes the above reaction.  相似文献   

5.
Summary: The separation of H2/CO2 is technologically important to produce the next generation fuel source, hydrogen, from synthesis gas. However, the separation efficiency achieved by polymeric membranes is usually very low because of both unfavourable diffusivity selectivity and solubility selectivity between H2 and CO2. A series of novel diamino‐modified polyimides has been discovered to enhance the separation capability of polyimide membranes especially for H2 and CO2 separation. Both pure gas and mixed gas tests have been conducted. The ideal H2/CO2 selectivity in pure gas tests is 101, which is far superior to other polymeric membranes and is well above the Robeson's upper‐bound curve. Mixed gas tests show an ideal selectivity of 42 for the propane‐1,3‐diamine‐modified polyimide. The lower selectivity is a result of the sorption competition between H2 and the highly condensable CO2 molecules. However, both pure gas and mixed gas data are better than other polymeric membranes and above the Robeson's upper‐bound curve. It is evident that the proposed modification methods can alter the physicochemical structure of polyimide membranes with superior separation performance for H2 and CO2 separation.

Both pure gas and mixed gas separation properties of H2/CO2 for membranes derived from 6FDA‐durene with respect to the upper‐bound curve.  相似文献   


6.
High frequency observations of the stable isotopic composition of CO2 effluxes from soil have been sparse due in part to measurement challenges. We have developed an open‐system method that utilizes a flow‐through chamber coupled to a tunable diode laser (TDL) to quantify the rate of soil CO2 efflux and its δ13C and δ18O values (δ13CR and δ18OR, respectively). We tested the method first in the laboratory using an artificial soil test column and then in a semi‐arid woodland. We found that the CO2 efflux rates of 1.2 to 7.3 µmol m?2 s?1 measured by the chamber‐TDL system were similar to measurements made using the chamber and an infrared gas analyzer (IRGA) (R2 = 0.99) and compared well with efflux rates generated from the soil test column (R2 = 0.94). Measured δ13C and δ18O values of CO2 efflux using the chamber‐TDL system at 2 min intervals were not significantly different from source air values across all efflux rates after accounting for diffusive enrichment. Field measurements during drought demonstrated a strong dependency of CO2 efflux and isotopic composition on soil water content. Addition of water to the soil beneath the chamber resulted in average changes of +6.9 µmol m?2 s?1, ?5.0‰, and ?55.0‰ for soil CO2 efflux, δ13CR and δ18OR, respectively. All three variables initiated responses within 2 min of water addition, with peak responses observed within 10 min for isotopes and 20 min for efflux. The observed δ18OR was more enriched than predicted from temperature‐dependent H2O‐CO2 equilibration theory, similar to other recent observations of δ18OR from dry soils (Wingate L, Seibt U, Maseyk K, Ogee J, Almeida P, Yakir D, Pereira JS, Mencuccini M. Global Change Biol. 2008; 14: 2178). The soil chamber coupled with the TDL was found to be an effective method for capturing soil CO2 efflux and its stable isotope composition at high temporal frequency. Published in 2010 by John Wiley & Sons, Ltd.  相似文献   

7.
ZIF‐8 membrane has the potential for CO2/CH4 separation based on size exclusion. But if traditionally prepared by solvothermal methods, it shows only negligible selectivity due to the linker mobility. Here, ≈500 nm‐thin hybrid ZIF‐7x‐8 membranes with suppressed linker mobility and narrowed window aperture are prepared by a fast current‐driven synthesis (FCDS) within 20 min. The in situ electric field during FCDS allows the formation of stiffened ZIF‐8_Cm as parent skeleton and the mixed‐linker strategy is applied to narrow the aperture size simultaneously. The ZIF‐722‐8 membrane shows significantly sharpened molecular sieving for CO2/CH4 with a separation factor above 25, which soared tenfold compared with other unmodified ZIF‐8 membranes. Additionally, the membrane shows exceptional separation performance for H2/CH4 and CO2/N2, with separation factors of 71 and 20, respectively. After 180 h temperature swing operation, it still maintains the excellent separation performance.  相似文献   

8.
A new porous organic polymer, SNU‐C1 , incorporating two different CO2‐attracting groups, namely, carboxy and triazole groups, has been synthesized. By activating SNU‐C1 with two different methods, vacuum drying and supercritical‐CO2 treatment, the guest‐free phases, SNU‐C1‐va and SNU‐C1‐sca , respectively, were obtained. Brunauer–Emmett–Teller (BET) surface areas of SNU‐C1‐va and SNU‐C1‐sca are 595 and 830 m2g?1, respectively, as estimated by the N2‐adsorption isotherms at 77 K. At 298 K and 1 atm, SNU‐C1‐va and SNU‐C1‐sca show high CO2 uptakes, 2.31 mmol g?1 and 3.14 mmol g?1, respectively, the high level being due to the presence of abundant polar groups (carboxy and triazole) exposed on the pore surfaces. Five separation parameters for flue gas and landfill gas in vacuum‐swing adsorption were calculated from single‐component gas‐sorption isotherms by using the ideal adsorbed solution theory (IAST). The data reveal excellent CO2‐separation abilities of SNU‐C1‐va and SNU‐C1‐sca , namely high CO2‐uptake capacity, high selectivity, and high regenerability. The gas‐cycling experiments for the materials and the water‐treated samples, experiments that involved treating the samples with a CO2‐N2 gas mixture (15:85, v/v) followed by a pure N2 purge, further verified the high regenerability and water stability. The results suggest that these materials have great potential applications in CO2 separation.  相似文献   

9.
A flexible two‐fold interpenetrated indium metal‐organic framework InOF‐23 , featuring one‐dimensional micro‐sized channels decorated by exposed N groups, was successfully synthesized. Interestingly, InOF‐23 displays unique dynamic responses to different gases (N2, Ar, and CO2) at low and room temperatures, which indicates that it can be a good candidate for gas adsorption and separation. Furthermore, the high efficiency detection for p‐nitroaniline (pNA) makes InOF‐23 a potential chemosensor for nitroaromatic explosives.  相似文献   

10.
Two new bridged alkoxysilanes, bis(triethoxysilylalkyl)‐N,N′‐oxalylureas (alkyl = methyl or n‐propyl), bearing a highly rigid and polar oxalylurea unit in the bridges, were employed as precursors of bridged silica membranes. The gas and water separation performance of the membranes prepared from the precursors using the sol–gel process was investigated. Interestingly, the membrane properties depended on the alkyl chain length. The membrane containing methylene units (alkyl = methyl) was porous and rather hydrophilic but the other with longer propylene units (alkyl = n‐propyl) was non‐porous and more hydrophobic. High H2/SF6 gas permeance ratios of 3100 and 1700, and NaCl rejections of 89 and 85% for 2000 ppm aqueous NaCl were obtained using the membranes containing methyl and n‐propyl, respectively. The membrane with alkyl = methyl also showed a high CO2/N2 permeance ratio of 20.6 at 50°C. These results indicate the potential applications of the membranes as gas and water separation materials. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

11.
Multilayer thin films of poly(ethylene oxide) (PEO) and poly(methacrylic acid) (PMAA), deposited via layer‐by‐layer (LbL) assembly from aqueous solutions, are investigated for CO2/N2 separation. Eight and ten bilayer (217 and 389 nm thick, respectively) PEO/PMAA thin films deposited on a 25 μm polystyrene substrate exhibit CO2/N2 selectivities of 142 and 136, respectively. These are the highest reported to‐date for this gas pair separation using a homogeneous polymer film. While further work remains to improve CO2 permeability, these results indicate the potential of LbL assemblies as standalone CO2 separation membranes for low‐flux/high‐purity applications, or as part of a composite and/or mixed‐matrix membrane for high‐flux applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1730–1737  相似文献   

12.
The high energy footprint of commodity gas purification and increasing demand for gases require new approaches to gas separation. Kinetic separation of gas mixtures through molecular sieving can enable separation by molecular size or shape exclusion. Physisorbents must exhibit the right pore diameter to enable separation, but the 0.3–0.4 nm range relevant to small gas molecules is hard to control. Herein, dehydration of the ultramicroporous metal–organic framework Ca‐trimesate, Ca(HBTC)?H2O (H3BTC=trimesic acid), bnn‐1‐Ca‐H2O, affords a narrow pore variant, Ca(HBTC), bnn‐1‐Ca. Whereas bnn‐1‐Ca‐H2O (pore diameter 0.34 nm) exhibits ultra‐high CO2/N2, CO2/CH4, and C2H2/C2H4 binary selectivity, bnn‐1‐Ca (pore diameter 0.31 nm) offers ideal selectivity for H2/CO2 and H2/N2 under cryogenic conditions. Ca‐trimesate, the first physisorbent to exhibit H2 sieving under cryogenic conditions, could be a prototype for a general approach to exert precise control over pore diameter in physisorbents.  相似文献   

13.
Summary: Carbon molecular‐sieve membranes (CMSMs) have shown great potential for gas separation. They exhibit high selectivity by permitting effective size‐ and shape‐separation between gas molecules of similar molecular dimensions. Hence, the control of their pore size is very important. While previous studies have focused on the conditions of pyrolysis and its effect on CMSM properties, a novel approach is reported here whereby the precursor polymer is chemically modified prior to pyrolysis and the resultant CMSM was investigated for its gas separation properties. Pyrolysis of chemically crosslinked and uncrosslinked Matrimid® resulted in a change in d‐spacing from 5.6 to 3.6 and 3.7 Å, respectively. The crosslinked CMSM also exhibited greater ordering in its packing. The Matrimid‐derived CMSMs exhibited excellent separation properties for CO2/CH4.

Mechanism of chemical crosslinking modification.  相似文献   


14.
Hydride complexes Mo,W(CO)(NO)H(mer‐etpip) (iPr2PCH2CH2)2PPh=etpip) ( 2 a,b(syn) , syn and anti of NO and Ph(etpip) orientions) were prepared and probed in imine hydrogenations together with co‐catalytic [H(Et2O)2][B(C6F5)4] (140 °C, 60 bar H2). 2 a,b(syn) were obtained via reduction of syn/anti‐Mo,W(NO)Cl3(mer‐etpip) and syn,anti‐Mo,W(NO)(CO)Cl(mer‐etpip). [H(Et2O)2][B(C6F5)4] in THF converted the hydrides into THF complexes syn‐[Mo,W(NO)(CO)(etpip)(THF)][B(C6F5)4]. Combinations of the p‐substituents of aryl imines p‐R1C6H4CH=N‐p‐C6H4R2 (R1,R2=H,F,Cl,OMe,α‐Np) were hydrogenated to amines (maximum initial TOFs of 1960 h?1 ( 2 a(syn) ) and 740 h?1 ( 2 b(syn) ) for N‐(4‐methoxybenzylidene)aniline). An ‘ionic hydrogenation’ mechanism based on linear Hammett plots (ρ=?10.5, p‐substitution on the C‐side and ρ=0.86, p‐substitution on the N‐side), iminium intermediates, linear P(H2) dependence, and DKIE=1.38 is proposed. Heterolytic splitting of H2 followed by ‘proton before hydride’ transfers are the steps in the ionic mechanism where H2 ligand addition is rate limiting.  相似文献   

15.
Metal‐organic frameworks (MOFs)‐based membranes have shown great potentials as applications in gas separation. In this work, a uniform membrane based on 2D MOF Ni3(HITP)2 (HITP=2,3,6,7,10,11‐hexaaminotriphenylene) was fabricated on ordered macroporous AAO via the filtration method. To fabricate the membrane, we obtained the Ni3(HITP)2 nanosheets as building blocks via a soft‐physical exfoliation method successfully that were confirmed by AFM and TEM. We also studied the H2, CO2 and N2 adsorption isotherms of Ni3(HITP)2 powder at room temperature, which shows Ni3(HITP)2 has high heats of adsorption for CO2 and high selectivity of CO2 over N2. Gas permeation tests indicate that the Ni3(HITP)2 membrane shows high permeance and selectivity of CO2 over N2, as well as good selectivity of H2 over N2. The ideal separation factors of CO2/N2 and H2/N2 from sing‐gas permeances are 13.6 and 7.8 respectively, with CO2 permeance of 3.15×10?6 mol?m?2?s?1?Pa?1. The membrane also showed good stability, durability and reproducibility, which are of potential interest for practical applications in the CO2 separations.  相似文献   

16.
Ion mobility spectrometry (IMS) separates ions while they travel through a buffer gas under the influence of an electrical field. The separation is affected by mass and charge but most particularly by shape (collision cross section). When coupled to MS, IMS-MS offers therefore a powerful tool for structural elucidation and isomer separation. Systematic studies aimed to compare and quantitate the effects of structural changes on drift time such as length and ramification of carbon chain, unsaturation, geometrical isomerism (cis/trans isomers for instance), cyclization and ring size are, however, scarce. Herein we used traveling wave ion mobility mass spectrometry (TWIM-MS) to systematically evaluate the relationship between structure and drift time. For that, a series of deprotonated carboxylic acids were used as model ions with a carboxylate “charge tag” for gas phase MS manipulation. Carboxylic acids showed a near linear correlation between the increase of carbon number and the increase of collision cross section (CCS). The number of double bonds changes slightly the CCS of unsaturated acids. No differences in drift time and no significant differences in CCS of cis- and trans-double bond of oleic and elaidic acids were observed. Cyclization considerably reduces the CCS. In cyclic carboxylic acids, the increase of double bonds and aromatization significantly reduces the CCS and the drift times. The use of a more polarizable drift gas, CO2, improved in some cases the separation, as for biomarker isomers of steranoic acids. The β-isomer (cis-decaline) has smaller CCS and therefore displayed lower drift time compared to the α-isomer (trans-decaline). Structural changes revealed by calculations were correlated with trends in drift times.  相似文献   

17.
Four novel organotin complexes of two types—[R2Sn(o‐SC6H4CO2)]6 (R=Me, 1 ?H2O; nBu, 2 ) and {[R2Sn(m‐CO2C6H4S)R2Sn(m‐SC6H4CO2)SnR2]O}2 (R=Me, 3 ; nBu, 4 )—have been prepared by treatment of o‐ or m‐mercaptobenzoic acid and the corresponding R2SnCl2 (R=Me, nBu) with sodium ethoxide in ethanol (95 %). All the complexes were characterized by elemental analysis, FT‐IR and NMR (1H, 13C, 119Sn) spectroscopy, TGA, and X‐ray crystallography diffraction analysis. The molecular structure analyses reveal that both 1 and 2 are hexanuclear macrocycles with hydrophobic “pseudo‐cage” structures, while 3 and 4 are hexanuclear macrocycles with double‐cavity structures. Furthermore, the supramolecular structure analyses show that looser and more intriguing supramolecular infrastructures were also found in complexes 1 – 4 , which exist either as one‐dimensional chains of rings or as two‐dimensional networks assembled from the organometallic subunits through intermolecular C? H???S weak hydrogen bonds (WHBs) and π–π interactions.  相似文献   

18.
Cross‐linked polymers of intrinsic microporosity (PIM)s for gas separation membranes, were prepared by a nitrene reaction from a representative PIM in the presence of two different diazide cross‐linkers. The reaction temperature was optimized using TGA. The homogenous membranes were cast from THF solutions of different ratios of PIM to azides. The resulting cross‐linked structures of the PIMs membranes were formed at 175 °C after 7.5 h and confirmed by TGA, XPS, FT‐IR spectroscopy and gel content analysis. These resulting cross‐linked polymeric membranes showed excellent gas separation performance and can be used for O2/N2 and CO2/N2 gas pairs, as well as for condensable gases, such as CO2/CH4, propylene/propane separation. Most importantly, and differently from typical gas separation membranes derived from glassy polymers, the crosslinked PIMs showed no obvious CO2 plasticization up to 20 atm pressure of pure CO2 and CO2/CH4 mixtures.

  相似文献   


19.
Mixed‐matrix membranes (MMMs) of Matrimid® and polyaniline/clay (PC) are investigated for CO2/CH4 separation and CO2‐induced plasticization. PC particles are synthesized through in‐situ polymerization of aniline in the presence of organophilic clay and then incorporated into Matrimid by solution casting method. Chemical structure and morphology of PC powder and fabricated membranes are analyzed by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry/thermogravimetric analysis (DSC/TGA) and scanning electron microscopy (SEM). The XRD spectra of PC particles show the exfoliation of silicate layers throughout the polyaniline (PAni) matrix, and SEM images indicate flower‐petal morphology for PC particles. The permeability values of CO2 and CH4 increase 30–35% by incorporation of 10 wt% PC without any significant drop in selectivity. PC particles with flower‐petal morphology plays an important role in increasing the gas permeability values of both gases while Matrimid is the only phase that controls CO2/CH4 selectivity. The plasticization pressure was increased to 30 bar by incorporation of 10 wt% PC in the Matrimid matrix. CO2 permeability and pplast improved 35% and 200%, respectively, resulting in 300% enhancement in the capacity of MMM in the purification of natural gas with a selectivity of about 40. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
Dicopper dicarboxylates [(R3P)mCuXCu(PR3)m] ( 5a , X = O2CCO2, R = Ph, m = 2; 5b , X = O2CCO2, R = nBu, m = 3) were prepared by treatment of [Cu2O] ( 1a ) with HO2CCO2H ( 2a ) in presence of PR3 ( 4a , R = Ph; 4b , R = nBu). A further synthesis approach to mono‐ and dicopper dicarboxylates is given using an electrolysis cell equipped with Cu electrodes and charged with acids H2X and phosphanes R3P. Without addition of a base mononuclear [(nBu3P)mCuXH] ( 6a , m = 3, XH = O2CCO2H, 6b , m = 3, XH = O2CCH2CO2H, 6c , m = 3, XH = O2CCH2CH2CO2H, 6d , m = 2, XH = O2C‐2‐C5H4N‐6‐CO2H) was formed, whereas in presence of NEt3 ( 3 ), the dicopper systems [(R3P)mCuXCu(PR3)m] ( 5a , X = O2CCO2, R = Ph, m = 2; 5b , X = O2CCO2, R = nBu, m = 3; 5c , X = O2CCH2CO2, R = nBu, m = 3; 5d , X = O2CCH2CH2CO2, R = nBu, m = 3; 5e , X = O2C‐2‐C5H4N‐6‐CO2, R = nBu, m = 3) were produced. When 6a reacted with [(tmeda)Zn(nBu)2] ( 7 ), trimetallic [(tmeda)Zn((nBu3P)3CuO2CCO2)2] ( 8 ) was accessible. In this heterobimetallic complex the Zn(tmeda) unit spans two CuO2CCO2 entities. The molecular structures of 5a , 6a and 6d in the solid state were determined by single X‐ray structure analysis. Complexes 5a and 6a are monomers, whereas 6d creates in the solid state a linear open chain coordination polymer by hydrogen bridge formation. Characteristic for 6d is the somewhat distorted trigonal bipyrimidal arrangement around the copper atom with the nBu3P ligands in axial and the C5H3NCO2H oxygen and nitrogen atoms in equatorial positions. In 5a the oxalate connectivity binds in a μ‐1,2,3,4 fashion being part of a planar Cu2(oxalate) core. TG studies of several mono‐ and dicopper dicarboxylates were carried out. Release of the PR3 ligands is recognized and the remaining Cu‐(di)carboxylate unit decomposes to afford elemental copper and CO2. The deposition of copper onto pieces of PVD‐Cu oxidized silicon wafers by applying the spin‐coating process and using 5c and 5d as precursors is discussed.  相似文献   

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