Water confined in nanoscopic pores is essential in determining the energetics of many physical and chemical systems. Herein, we report a recently discovered unconventional, reversible chemical reaction driven by water quantities in nanopores. The reduction of the number of water molecules present in the pore space promotes the hydrolysis of CO32? to HCO3? and OH?. This phenomenon led to a nano‐structured CO2 sorbent that binds CO2 spontaneously in ambient air when the surrounding is dry, while releasing it when exposed to moisture. The underlying mechanism is elucidated theoretically by computational modeling and verified by experiments. The free energy of CO32? hydrolysis in nanopores reduces with a decrease of water availability. This promotes the formation of OH?, which has a high affinity to CO2. The effect is not limited to carbonate/bicarbonate, but is extendable to a series of ions. Humidity‐driven sorption opens a new approach to gas separation technology. 相似文献
Secondary ion mass spectrometry (SIMS) has inherent features of high sensitivity, great dynamic range, and capability to provide spatially resolved chemical information making it well suited for trace and microanalysis of diverse materials. The various SIMS methods used to derive the boron distribution in hepatoma cells, to investigate the intcr-iayer reactions in multi-layer ceramic structural materials, and to evaluate the effects of fabrication on microstructural and functional properties in semiconductor devices, are presented to illustrate possible roles of SIMS in microanalysis. 相似文献
Ion isolation in a linear ion trap is demonstrated using dual resonance frequencies, which are applied simultaneously. One frequency is used to eject ions of a broad m/z range higher in m/z than the target ion, and the second frequency is set to eject a range of ions lower in m/z. The combination of the two thus results in ion isolation. Despite the simplicity of the method, even ions of low intensity may be isolated since signal attenuation is less than an order of magnitude in most cases. The performance of dual frequency isolation is demonstrated by isolating individual isotopes of brominated compounds.
The pressing aim of this work is to prevent an error from proliferating. In arecent paper, a new procedure for calculating the junction potentials has beenpresented, whose purported goal is to allow individual ion activities and activitycoefficients to be identified using the appropriate ISEs. As convincing and usefulas this procedure may seem, it is, however, fallacious. The present analysisconsiders the results obtained when applying the procedure to typical friendlycases liable to precise thermodynamic–mathematical treatments. It is shown thatthe individual ion activities found are a mere artifact of the initial settings and,therefore, change accordingly. The implications raised from the values of suchindividual ion activities and, in particular, those concerned with the modifiedHydration Theory, are, in turn, devoid of any real experimental validation. 相似文献
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
Collision induced dissociation (CID) is one of the most established techniques for tandem mass spectrometry analysis. The CID of mass selected ion could be realized by ion resonance excitation with a digital rectangular waveform. The method is simple, and highly efficient CID result could be obtained by optimizing the experimental parameters, such as digital waveform voltage, frequency, and q value. In this work, the relationship between ion trapping waveform voltage and frequency at preselected q value, the relationship between waveform frequency and the q value at certain ion trapping voltage for optimum CID efficiency were investigated. Experiment results showed that the max CID efficiency of precursor reserpine ions can be obtained at different trapping waveform voltage and frequency when q and β are different. Based on systematic experimental analysis, the optimum experimental conditions for high CID efficiency can be calculated at any selected β or q. By using digital ion trap technology, the CID process and efficient fragmentation of parent ions can be realized by simply changing the trapping waveform amplitude, frequency, and the β values in the digital ion trap mass spectrometry. The technology and method are simple. It has potential use in ion trap mass spectrometry.
The acyl substitution reactions between 1-hydroxy-7-aza-benzotriazole (HOAt)/1-hydroxy-benzotriazole (HOBt) ester reagents and nucleophilic side chains on peptides have been demonstrated in the gas phase via ion/ion reactions. The HOAt/HOBt ester reagents were synthesized in solution and ionized via negative nano-electrospray ionization. The anionic reagents were then reacted with doubly protonated model peptides containing amines, guanidines, and imidazoles in the gas phase. The complexes formed in the reaction cell were further probed with ion trap collision induced dissociation (CID) yielding either a covalently modified analyte ion or a proton transfer product ion. The covalent reaction yield of HOAt/HOBt ester reagents was demonstrated to be higher than the yield with N-hydroxysuccinimide (NHS) ester reagents over a range of equivalent conditions. Density functional theory (DFT) calculations were performed with a primary amine model system for both triazole-ester and NHS-ester reactants, which indicated a lower transition state barrier for the former reagent, consistent with experiments. The work herein demonstrates that the triazole-ester reagents are more reactive, and therefore less selective, than the analogous NHS-ester reagent. As a consequence, the triazole-ester reagents are the first to show efficient reactivity with unprotonated histidine residues in the gas phase. For all nucleophilic sites and all reagents, covalent reactions are favored under long time, low amplitude activation conditions. This work presents a novel class of reagents capable of gas-phase conjugation to nucleophilic sites in analyte ions via ion/ion chemistry.
Infrared multiphoton photodissociation (IRMPD) in a quadrupole ion trap is not selective for a parent ion. Product ions are
decreased in abundance by continuous sequential dissociation and may be lost below the low mass cut-off. The IRMPD process
is made selective by resonantly exciting trapped ions into an axially offset laser path. Product ions form and collisionally
relax out of the laser path to accumulate in the center of the trap. The technique, termed selective broadband (SB) IRMPD,
limits sequential dissociation to preserve first generation product ion abundance. The abundances of larger product ions are
maximized by completely dissociating the parent ion, but continuous sequential dissociation does not form small product ions
below the low mass cut-off associated with conventional IRMPD. Smaller product ions are further increased in abundance in
another tandem mass spectrum by performing sequential stages of SB-IRMPD, adjusting the trapping rf amplitude to dissociate
larger product ions at the same qz range. Thermal assistance is used to perform SB-IRMPD at higher bath gas pressures for increased sensitivity. 相似文献