暗霉素的快原子轰击(FAB)质谱

快原子轰击(fast atom bombardment,简称 FAR)质谱是八十年代开发的质谱新技术.这种在室温条件下用具有一定能量的中性原子轰击样品进行离子化的技术特别适用予热稳定性差、难挥发、强极性样品的分析.我们用 FAB 对七个暗霉素(nebramycin)抗生素组分进行结构测定,获得了较满意的结果.暗霉素属氨基糖苷类抗生素.我们从我国土壤中分离的菌株发酵液中提取暗霉素复合物及其水解产物,并分离和鉴定了七个单一组分.这七个化合物(1～7)的结构如下:     

Fast atom bombardment mass spectra of telluronium salts

The fast atom bombardment (FAB) mass spectra of telluronium salts were studied. The spectra exhibit the intact cation (C⁺) and cluster ions ([M + C]⁺). The principal fragment ions in the FAB mass spectra of telluronium salts are [RTe]⁺, [R₂Te]⁺˙, [R₂Te − H]⁺, [RTeR′]⁺˙, and [RTeR′ + H]⁺. When the anion was [BPh₄]⁻, interesting cluster ions such as [M + C − BPh₃]⁺ appeared.     

Fast atom bombardment mass spectra of iodonium salts

Positive-ion fast atom bombardment mass spectra and linked-scan tandem mass spectra were measured for aromatic iodonium salts. The mass spectra usually contain the intact cation of the iodonium salt as the base peak, fragment ions of lower abundance resulting from simple cleavages or rearrangements, and a characteristic loss of atomic iodine. High-level semi-empirical calculations suggest that an obtuse ring? I⁺? ring angle facilitates loss of atomic iodine through concomitant ring? to? ring bond formation.     

Fast atom bombardment mass spectra of monosulphonated merocyanine dyestuffs

The FAB mass spectra of four sulphonated merocyanine dyes are investigated. Negative ion spectra are superior to those in the positive ion mode. The special structure of merocyanines with an acidic group at one end of the molecule and a basic group at the other leads to significantly different fragmentation pathways for positive and negative ions.     

Fast atom bombardment mass spectra of O-isopropyl oligodeoxyribonucleotide triesters

The positive and negative fast atom bombardment (FAB) mass spectra of representative dimeric O-isopropyl oligodeoxyribonucleotide triesters were recorded and examined. Features found to be shared among the FAB mass spectra of these compounds yielded important information regarding molecular weight, nucleobase composition and nucleotide sequence.     

Fast atom bombardment mass spectra of involatile sulphonated azo dyestuffs

Fast atom bombardment mass spectra of a range of involatile mono and disazo sulphonated dyestuffs are presented. Excellent spectra are obtained for dyestuffs containing up to five sulphonate groups. The fragmentations are discussed with special reference to the ions formed by cleavage of the azo linkage. The negative ion spectra are shown to be superior to those obtained in the positive ion mode.     

Fast atom bombardment mass spectra of isobaric/isomeric phosphonium salts

The positive ion fast atom bombardment mass spectra of isobaric/isomeric aryl phosphonium salts typically contain abundant intact cations, which can be used to establish the cationic molecular weight, characteristic ions that can be used to delineate structural subgroups, and fragment ions corresponding to losses of small neutral molecules. Several of the fragmentation pathways were elucidated by parent ion and daughter ion tandem mass spectrometry experiments. Dependence of the fragmentation reactions on functional group substitution suggests that fast atom bombardment mass spectrometry is an excellent method for the differentiation of isobaric/isomeric phosphonium salts used in synthetic organic and industrial catalytic processes.     

Fast atom bombardment and secondary ion mass spectra of thiamine hydrochloride

The ratio of the fragment ions at m/z 122 and m/z 123 in the positive ion fast atom bombardment or secondary ion mass spectra of thiamine hydrochloride varies with sample preparation and experimental conditions. For all mass spectra that contained significant abundances of matrix (S) ions [S + H]⁺, the fragment at m/z 123 is the more abundant of the two ions. If [S + H]⁺ ions are not observed in the mass spectrum under the conditions selected, the ion at m/z 122 is more abundant. This correlation suggests that hydrogen transfer to the fragment ion occurs in the gas phase, with the composition of the ion-solvent cluster ions in the selvedge region being the key factor. The ratio of the fragment ions at m/z 123 and m/z 122 is thus an indicator of the extent of protonation in the selvedge, the region immediately above the solvent surface created by primary particle bombardment.     

Fast atom bombardment mass spectra of some alkylammonium 4-toluenesulfonate salts

The fast atom bombardment positive ion mass spectra of low molecular weight alkylammonium 4-toluenesulfonate salts are dominated by cluster ions of the type [(AB)_nA]⁺ or [(AB)_nH]⁺, where A is a cation, B an anion, n an integer from 0 to 4. With one exception the base peak is the cation A⁺.     

Fast atom bombardment mass spectra of keto acid and keto ester phosphoranes

Positive-ion fast atom bombardment mass spectra of 13 keto acid and keto ester phosphoranes were examined. All compounds gave a protonated molecular ion and characteristic peaks at m/z 303, 279, 262 and 201.     

Fast atom bombardment mass spectrometry of pertechnetate

Negative Ion Fast Atom Bombardment Mass Spectrometry is conducted on potassium pertechnetate evaporated onto a copper probe. The mass spectra of pertechnetate /TcO ₄ ^– / reveal the presence of mononuclear and polynuclear technetium oxo species which form general series Tc_nO _n+1 ^– ,...Tc_nO_n+4 with n=1 to 5. The polynuclear species are believed to be formed via gas phase reactions.     

Fast atom bombardment mass spectrometry of polyglycols

Fast atom bombardment mass spectrometry (FAB-MS) has rapidly become established, after its introduction two years ago, as a method of choice for mass spectral analysis of higher molecular weight polar organic chemicals. In industrial analysis, the technique has been found to be a very effective method for analyzing numerous classes of polar polymeric chemicals, including rubber and plastic additives, organometallics, and polar polymers. Normally applied in conjunction with field desorption (FD-MS), FAB-MS is used to determine chemical structures for both pure compounds and oligomeric mixtures. Fast atom bombardment results for poly(ethylene glycol) and poly(propylene glycol) show that, while oligomer quasimolecular ion distributions give a rough indication of relative oligomer abundances, the data are not quantitative in comparison with that previously described for FD-MS (or electrohydrodynamic ionization, EH-MS) analysis. More specifically, lower mass oligomer intensities tend to be too high in FAB-MS due to fragmentation reactions.     

Fast atom bombardment mass spectrometry of salts

The positive and negative fast atom bombrdment spectra of two groups of simple salts have been recorded. The structures of the major ionic species of eight chlorides and five, complex anion, sodium salts have been interpreted and tabulated.