The increasing number of applications for fast atom bombardment (FAB) mass spectrometry has seen a corresponding increase in the use of different matrix compounds. This review discusses briefly the use of matrix compounds in general and the use of cosolvents and/or additives with glycerol that assist in producing superior FAB mass spectra than when glycerol is used on its own. The main part of the review deals with alternative matrix compounds to glycerol including thioglycerol, polyethyleneglycols, triethanolamine, diamylphenol, crown ethers and various miscellaneous matrix compounds.
Using mono-, di-, tri-and tetrasaccharides, nucleosides, bile acids, riboflavin, gibberellin A3, aminoglycosides, flavanoid and cardenolide glycosides, the sodium salt of riboflavin phosphate and the quaternary ammonium drug propantheline bromide, the performance of a new moving belt interface for liquid chromatography mass spectrometry has been evaluated. It is shown to be superior to previous interfaces of this type in its ability to provide relative molecular mass information from thermally labile low volatility compounds. The spectra obtained are similar to those obtained by desorption chemical ionization.
The new technique of fast atom bombardment mass spectrometry has been applied to the investigation of a series of penicillins as free acids or as alkali metal salts. In all cases both positive and negative ion pseudomolecular species are observed giving molecular weight information. Additionally, significant fragmentation is observed in both the positive and negative ion spectra, which gives considerable structural information.
The technique of fast atom bombardment mass spectrometry has been shown to be capable of producing molecular weight and useful fragmentation information from a selection of penicilloic acids. In addition, the technique has been shown to give similar information on alkali metal salts of penicilloic acids.Penicilloic acids are the major degradation products of penicillins and are formed by alkaline hydrolysis of the ji-lactam ring as shown in Scheme 1. Further degradation can occur and penicilloic acids can readily be decarboxylated under acidic conditions to give rise to the corresponding penilloic acids.The preparation of penicilloic acids from the corresponding penicillins has been described in detail by MUNRO and co-workers1).We have previously reported in detail on the fast atom bombardment mass spectra of penicillin free acids and alkali metal salts2,3). With all the penicillins reported and many others studied since those reports, molecular weight and useful fragmentation information has been obtained from the fast atom bombardment mass spectra.There is very little published mass spectral data on penicilloic acids. MITSCHER and co-workers' have reported the isobutane chemical ionization mass spectra of benzylpenicilloic acid dimethyl ester and phenoxymethylpenicilloic acid dimethyl ester. In the spectra of both of these compounds the protonated molecular ion was the base peak in the spectrum with major fragmentation ions being restricted to the thiazolidine cation at m/z 174. No mass spectra on free penicilloic acids or penicilloic acid alkali metal salts have been published.
ExperimentalMass spectra were obtained using a VG Analytical ZAB reverse geometry mass spectrometer fitted with an Ion Tech Fast Atom Bombardment gun. The fast atom beam was of xenon atoms.Samples were prepared by dissolving the penicilloic acid in methanol and then mixing the solution with glycerol on the target. Stable ion currents were produced for several minutes and in a number of cases both positive and negative ion spectra were recorded from the same sample loading.Scheme 1. Degradation of penicillin to penicilloic and penilloic acids.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.