2,4—二氨基—5—取代苄基嘧啶类质谱研究

报道了8个2,4-二氨基-5-取代苄基嘧啶衍生物的电子轰击质谱及碰撞活化解离和质量分析离子动能谱.该谱提供了化合物醚键及2,4-二氨基-5-取代苄基嘧啶环的主要碎裂途径,总结了一些裂解规律,将有助于这类化合物的结构推断。     

Isomer differentiation and structural characterization of penem β-lactam antibiotics by mass-analyzed ion kinetic energy spectrometry

A number of clinically significant penem β-lactams, both free acids and sodium salts, were investigated by mass-analyzed ion kinetic energy spectrometry (MIKES) following fast atom bombardment (FAB) ionization. The collisionally activated dissociation (CAD) products of [M + H] ⁺ and [M + Na]⁺ ions are described. Carbon dioxide loss was observed for some of the free acids, whereas a daughter ion generated by β-lactam ring cleavage was characteristic of the sodiated species. Other fragments included successive cleavages and rearrangements of the substituent side-chain, permitting complete characterization of these chains. The fragmentation pattern for both protonated and sodiated species were more clearly established by CAD MIKES than by normal FAB mass spectral analyses. A notable feature of this technique was its ability to differentiate between pairs of regioisomeric penems on the basis of their fragmentation patterns. These compounds could not be differentiated in the usual mass spectra.     

Collisionally induced dissociation mass spectrometric studies of perfluorinated 1H-heptane,tert-butanol, 2-butyltetrahydrofuran and isopropyl bromobutyl ether

High-energy collision-activated dissociation in connection with mass-analyzed ion kinetic energy spectrometry (CAD/MIKES) was employed to probe the structures of some ions generated by methane chemical ionization (CI) and negative ion chemical ionization (NICI) of the title compounds. CAD/MIKES results show that the [M ? H]^? ion of lH-perfluorobeptane and the [O(CF₂)₄Br]^? ion of perfluoroisopropylbromobutyl ether are stable. The methane CI of these fluorocarbons also showed that the expulsion of HF molecules appears to be a major driving force for further fragmentations.     

苯二酚异构体双电荷离子和单电荷离子的动能谱研究

本文利用质量分析离子动能谱(MIKES)、碰撞诱导解离(CID)技术和电子捕获诱导解离(ECID)技术, 研究了邻、间、对苯二酚分子在电子轰击质谱(EIMS)中产生的双电荷离子[C6H6O2]^2^+, [C6H4O]^2^+和单电荷离子[C6H6O2]^+。根据测定的电荷分离反应动能释放值T和由此计算出的两电荷间距R, 推测出过渡态的结构。有趣的是, 可利用单电荷离子[C6H6O2]^+的MIKES/CID谱区分苯二酚异构体。     

冠醚稀土络合物的快原子轰击质谱

本文报道十余个冠醚稀土络合物的快原子轰击质谱(FABMS)。通过分析FABMS的特征及亚稳离子分解讨论了溶液中的反应和络合性质。     

Determination of the isomeric composition of an ionic mixture using collision cross-sections

A theory has been developed for the determination of the isomeric composition of an ionic mixture. The probability theory describing the collisionally activated decomposition (CAD) which was developed previously provided a general foundation for the present theory. Quantification was based on the cross-sections for the collisional production of daughter ions as observed in the mass-analysed ion kinetic energy Spectrometry (MIKES). Experimental details for the implementation of the theory have also been developed. The method has been applied to the case of C₂H₄O^+· generated from butane-l,3-diol, which is known to be a mixture of more than one isomeric structure. The results seem to be far superior to those based on previous methods, as evidenced by the excellent internal consistency.     

Electron ionisation mass spectral analysis and fragmentation pathways for some thiophosphorylic p-carboxybenzene sulfonamides

The work presents the 70 eV electron impact mass spectra of some thiophosphorylic p-carboxybenzene sulfonamides, and proposes rationalisation of their fragmentation pathways. Accurate mass measurements of the fragment ions, and metastable ion analyses performed in the MIKES mode, were used to elucidate the most abundant ion compositions and to elucidate the fragmentation patterns of these pharmacologically interesting compounds.     

一些双电荷离子的气相碎裂反应

借助质量分析离子动能谱和串联质谱研究了由电子轰击产生的双电荷离子的单分子亚稳碎裂及碰撞诱导分解过程,讨论了两种实验方法导致的差别因素.此外,根据质量分析离子动能谱提供的双电荷离子电荷分离反应的动能释放值计算了两电荷中心间距的最小值,以判别按不同电荷分离方式碎裂的双电荷离子的过渡态结构.     

不饱和脂环氮杂冠醚的合成和结构表征

采用相转移催化反应合成了两个不饱和脂环氮杂冠醚。利用红外光谱、核磁共振谱、质谱测定了他们的结构。特别是利用高分辨质谱、碰撞诱导裂解、质量分析离子动能谱对它们的质谱特性进行了深入研究,提出了可能的碎裂途径。 由于两个化合物的结构类似,所以它们的质谱有相同之处,但环大小和取代基不同,也有明显的差别。     

双电荷离子[C12H12N2O]2+和[C12H12N2S]2+的气相单分子分解反应研究

The unimolecular dissociation reactions of doubly charged ions were reported,which resulted from a tandem mass spectrometer and a reversed geometry double focusing mass spectrometer by electron impact.Mass analyzed ion kinetic energy spectrometry(MIKES) was used to obtain the kinetic energy releases in charge separation reactions of doubly charged ions.The intercharge distances between the two charges at transition states can be calculated from the kinetic energy releases.Transition structures of unimolecular dissociation reactions were infered from MIKES and MS/MS.     

双电荷离子［C_（12）H_（12）N_2O］~（2＋）和［C_（12）H_（12

双电荷离子［Ｃ_（１２）Ｈ_（１２）Ｎ_２Ｏ］~（２＋）和［Ｃ_（１２）Ｈ_（１２）Ｎ_２Ｓ］~（２＋）的气相单分子分解反应研究任达，贾维平，李智立，刘淑莹（中国科学院长春应用化学研究所，长春，１３００２２）关键词双电荷离子，质量分析离子动能谱，串联质谱，４...     

Kinetic energy release of protonated methanol clusters using the low-temperature fast-atom bombardment: experiment and theory combined

Low-temperature fast-atom bombardment was found to be an excellent method for generating large protonated methanol clusters, (CH(3)OH)(n)H(+) (n = 2 to 15). Metastable dissociations of these clusters, involving elimination of one methanol molecule, were studied using mass-analyzed ion kinetic energy spectra (MIKES). From metastable peak profiles kinetic energy release (KER) distributions were obtained, even for clusters as large as (CH(3)OH)(15)H(+). The results were analyzed by a simple thermal model, by the finite heat bath theory (FHBT) and by the RRKM-based MassKinetics algorithm. The KER distribution was shown to correspond to a three-dimensional translational energy distribution, implying statistical energy partitioning in the transition state. The mean KER values and transition state temperatures were found to increase with cluster size, reaching 25 meV and approximately 210 K for large clusters (n = 10).     

Mass spectrometric study of gamma-aryl-alpha,-gamma-diethoxy-alpha, beta-butenolides

Electron impact mass spectra of eight of the title compounds are reported. Abundant fragment ions were produced under electron impact (EI) conditions and, with one exception, the ($?hbox?ArC??equiv$ O) ions were the base peaks. The EI fragmentation mechanisms of two representative compounds were studied with the aid of high-resolution and mass-analyzed ion kinetic energy spectrometry (MIKES) data. The M(+) ions fragment to give both an odd-electron ion and an even-electron fragment ion. Two H-atom rearrangements proceeding via four-membered ring intermediates and three losses of CO through i- and alpha-fragmentations were observed under EI. On comparing fragmentations under EI conditions with those under FAB conditions for two of the compounds, the fragmentation mechanisms were reasonably similar, with additional fragmentations rationalized in terms of the ionization proton being located on the oxygen atom of the beta-ethoxy group.     

Origin of the tailing signal on the low-energy side of the main beam in mass-analyzed ion kinetic energy spectra

The tailing signal on the low-energy side of the precursor ion signal observed during fast atom bombardment (FAB) mass-analyzed ion kinetic energy spectrometric (MIKES) analyses is due largely to ions of higher m/z value than the chosen precursor. The majority of these ions are independent, unfragmented species that emerge from the ion source with less than the full amount of kinetic energy predicted by the source potential. The tailing precursor ion signal observed under helium collision-activated decomposition conditions is too short to account for the protracted MIKES tail (as judged from mass-to-charge ratio-deconvoluted MIKES analyses performed on a BEqQ hybrid instrument), and a tailing precursor signal is not observed under unimolecular decomposition conditions. Measurements of the mass-to-charge ratios of the ionic species comprising the MIKES tail demonstrated that ions higher in mass-to-charge ratio than the chosen precursor are present throughout the tail, with the mass-to-charge ratio increasing as kinetic energy decreases. These ions possess the same momentum as the chosen precursor, and thus were formed prior to the magnetic field. The existence of intact, source-formed [M + H]⁺ ions with reduced kinetic energy was demonstrated through several types of tandem mass spectrometric experiments. These [M + H]⁺ ions with reduced kinetic energy do not appear to have undergone collisional deceleration, because they do not possess increased internal energy (as judged by observation of their fragmentation patterns). The kinetic energy profiles of unfragmented FAB-desorbed ions were determined and found to exhibit a tailing character similar in appearance to that of the MIKES tail. The population of ions emerging from the source under FAB conditions thus incorporates the characteristics necessary to account for the MIKES tail, namely, the presence of ions of a mass-to-charge ratio higher than the chosen precursor (due to matrix and other background ions), which possess reduced kinetic energy such that their momentum is identical to that of the selected precursor. These ions may arise via desolvation and declustering processes in the acceleration region of the ion source, or via FAB or chemical ionization processes in regions removed from the FAB target.     

气相二茂铁双电荷离子的动能谱研究

The unimolecular charge separation reactions of the doubly charged ions FeC_(10)H_(10)~(2+)、FeC_(10)H_9~(2+)、FeC_(10)H_8~(2+) produced in the ion source by electron impact from ferrocene have been studied using Mass analyzed Ion Kinetic Energy Spectrometry (MIKES) technique. From the values of the kinetic energy releases (T), the intercharge distances (R) of the exploding doubly charged ions in their transition structures have been estimated and some structural informations about the transition states can be obtained. The collision induced reactions of the FeC_(10)H_(10)~(2+) ion with Ar have been studied using MIKES, we postulate a new type of continuing reaction which may be "collisional charge separation induced dissociation".     

氯代甲苯双电荷离子的单分子解离反应研究

研究了在70 eV电子轰击电离条件下，氯代甲苯及氯化苄产生的双电荷离子[C_7H_7Cl]~(2＋)、[C_7H_6Cl]~(2＋·)和[C_7H_5Cl]~(2＋)为母体的两种类型单分子解离反应．主要讨论了亚稳双电荷离子的异构化反应、失H解高的“偶电子规则”以及单分子电荷分离过渡态的结构．     

Structural distinction among inositol phosphate isomers using high-energy and low-energy collisional-activated dissociation tandem mass spectrometry with electrospray ionization

Electrospray (ESI) collisional-activated dissociation (CAD) tandem mass spectrometric methods for the structural characterization of inositol phosphates (InsPs) using both quadrupole and sector mass spectrometers are described. Under low-energy CAD, the [M + H](+) ions of the positional isomers of inositol phosphates, including inositol mono-, bis- and trisphosphates, yield distinguishable product-ion spectra, which are readily applicable for isomer differentiation. In contrast, the product-ion spectra arising from high-energy CAD (2 keV collision energy, floating at 50%) tandem sector mass spectrometry are less applicable for isomer identification. The differences in the product-ion spectrum profiles among the aforementioned InsP isomers become more substantial and differentiation of positional isomers can be achieved when the collison energy is reduced to 1 keV (floating at 75%). These results demonstrate that the applied collision energies play a pivotal role in the fragmentations upon CAD. The product-ion spectra are similar among the positional isomers of inositol tetrakisphosphates and of inositol pentakisphosphates. Thus, isomeric distinction for these two inositol polyphosphate classes could not be established by the tandem mass spectrometric methods that have achieved such distinctions for the less highly phosphorylated inositol phosphate classes. Under both high- and low-energy CAD, the protonated molecular species of all InsPs undergo similar fragmentation pathways, which are dominated by the consecutive losses of H(2)O, HPO(3) and H(3)PO(4).     

Collision-activated dissociation mass spectra of crown ethers,perfluorinated crown ethers and related macrocycles

The collision-activated dissociation (CAD) mass spectra for a series of crown ethers, perfluoro crown ethers, cryptands and several dicyclohexano substituted crown ethers are reported. The CAD spectra were acquired with a triple quadrupole mass spectrometer, and in some cases spectra were recorded as a function of collision energy. In general, the protonated crown ethers dissociate via a series of losses of C₂H₄O units. The perfluoro crown ethers dissociate predominantly via losses of C₂F₄O units. The dicyclohexano ethers fragment in analogous ways in conjunction with cleavage of the cyclohexano rings. CAD spectra are also reported for acyclic ether systems.     

烷基苯磺酸盐的电喷雾离子化质谱和碰撞活化解离质谱－质谱分析

用正,负电喷雾电离（ESI）并结合碰撞活化解离（CAD）质谱法对烷基苯磺酸盐（ABS）进行鉴定,无论正,负离子化过程中均不出现快原子轰击质谱常见的碎片峰,由于没有复杂碎片峰的干扰,ESI－MS对分析ABS试样大为有利,正离子ESI－MS对支化ABS鉴定的灵敏度远低于负离子ESI－MS,用CAD－MS对ESI－ME谱各主要峰进行了归属,线型与支化ABS相对含量可以用负离子ESI－MS求出,负离子化ESI－MS是快速,有效和可靠的鉴定,ABS的方法。     

On the use of scans at a constant ratio of B/E for studying decompositions of peptide metal(II)-ion complexes formed by electrospray ionization

The use of sector mass spectrometers to study metastable ion decompositions of peptide metal-ion complexes formed by electrospray ionization is discussed. Products that are formed by charge-separation reactions are characterized by large kinetic energy release distributions. This causes scans at a constant B/E to give incorrect product ion abundances and possibly incorrect mass assignments. Two instrumental methods exist that can be used either to detect the ions or to estimate relative ion abundances: a floated collision cell or mass-analyzed ion kinetic energy spectrometry (MIKES) scans. The floated collision cell, by virtue of an altered B/E scan law, however, discriminates against important metastable ion reactions that occur outside the cell. MIKES scans provide a clearer estimate of product ions that arise by metastable ion charge-separation reactions. Problems with pseudotandem (first field-free region) experiments are also discussed.