The mass spectra of some (polypyridyl)ruthenium(Il) complexes of the type [Ru,L(bpy),](PF,), (L = 2,2':6,2"-terpyridine ( x = I ), 3,3':5,3"-bis(dimethylene)-2,2':6,2"-terpyridine ( x = l), 5,6,9,10,1 l,12,l5,16-octahydrocycloota[ 1",2":5,6;4",3":5',6']dipyrido[2,3-b:2',3'-b]di[ 1 ,IO]phenanthroline ( x = 1, 2), and N,N'-dimethylene-2,2'-biimidazole ( x = I; bpy = 2,2'-bipyridine) have been investigated by using fast atom bombardment tandem mass spectrometry. The low-energy collision-induced dissociation (CID) spcctra provide confirmation of the structures and details about fragmentations of the complexes. The observed decomposition pathways involve losses of intact ligands, PF; counterions, simple bond cleavages, fluoride transfers from the PF; counterion to thc Ru(1l) center with loss of PF5, and reductive eliminations of HF. The fluoride-transfer reaction can be used to determine thc coordination of the chelating ligands in the parent complex. IntroductionR u t h e n i u m complexes containing 2,2'-bipyridine (bpy) ligands and related analogues have been the subject of recent investigations.'-3 These compounds have promise for the conversion of solar power into electrical and chemical en erg^.^-^ A variety of ruthenium complexes with ligands consisting of polyaza cavityshaped macrocycles have been synthesized with the intent of inducing unusual metal complex chemistry and optimizing photocatalytic efficien~y.~-'~ Various analyses of Ru( 11) complexes with plypyridine ligands have been reported. Others have investigated the resonance Raman spectra of various reduction products of tris(bipyridy1)-r u t h e n i u m ( l I ) . l 4 Mass spectrometric techniques for t h e characterization of involatile, intractable organometallic complexes have been successfully developed, such as field desorption (FD) mass s p e c t r~m e t r y , l~-~~ electrohydrodynamic mass spectrometry ( E H MS),'* laser desorption mass spectrometry (LDMS),I9 secondary ion mass spectrometry (SIMS),20y21 and fast atom bomb a r d m e n t ( F A B ) mass ~p e c t r o m e t r y . I~.~~-~~ In general, singly charged ions are produced by using these techniques. However, t h e observation of doubly charged ions from coordination compounds containing multiply charged cationic metal centers has been reported. Cook and co-workers have reported forming [ R u ( bpy)J2+ and [ Fe(bpy),]*+ using electrohydrodynamic mass s p e c t r o m e t r y ( E H M S ) . 1 8 Doubly charged ions, including [Ru-( bpy),12+, from coordination compounds have also been observed in FAB mass ~p e c t r a .~~?~~ In addition, t h e mass spectra of coordination complexes have been compared with their properties in ~o l u t i o n . '~~'~ The FAB process can be an energetic ionization
Mass spectrometry is combined with liquid chromatography (LC/MS) and mass spectrometry (MS/MS) to identify ampicillin and two known metabolites--ampicillin penicilloic acid and ampicillin piperazine-2,5-dione--in human urine samples. Identifications were based on the fact that the metabolites or degradation products contain a substructure of ampicillin. In addition, two previously unidentified components in human urine samples were detected, corresponding to newly discovered metabolites or degradation products of ampicillin. Different chromatographic retention times in the LC mass spectra indicated two different compounds. However, the tandem mass spectra of these two components were similar, suggesting that they are stereoisomers. The use of LC/MS and MS/MS confirmed that the unknown components are the (3S,5R) and (3S,5S) epimers of ampicillin penilloic acid. Further study showed that only one of the components was eliminated from the body; the other arises from interconversion to the epimer in a urine sample. It is speculated that the component produced in vivo is the (3S,5R) epimer of ampicillin penilloic acid.
The fragmentation of two penicillins, ampicillin and amoxicillin, and their principal metabolites has been studied by a combination of liquid chromatography/thermospray mass spectrometry and tandem mass spectrometry. A high-resolution tandem mass spectrometer was used to obtain chemical ionization, fast-atom bombardment, and collision-induced dissociation mass spectra. Structural information and fragmentation mechanisms have been deduced from ions in the mass and collision spectra. This knowledge is useful in the analysis and identification of metabolites of ampicillin and related drugs in human body fluids.
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