Atmospheric pressure ionization tandem mass spectra of protonated timolol

✍ Scribed by Qin, Xue-Zhi

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 338 KB
• Volume: 34
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199901)34:1<51::aid-jms759>3.0.co;2-a

✦ Synopsis

Structural identiÐcation of drugs by tandem mass spectrometry (MS/MS) is interesting, important and challenging. In this study, atmospheric pressure ionization (API) MS/MS was applied to probe the structure of timolol, a typical b-adrenergic receptor-blocking agent (b-blocker). The characteristic MS/MS features of this drug were analyzed in detail. The results should be signiÐcant for other b-blockers with similar structures (namely, the group sandwiched between the aromatic and ethanolamine groups). Furthermore, timolol is a multi-ÈOCH 2 È functional organic compound, containing amine, ether and alcohol functional groups. The API-MS/MS study is interesting from the point of view of the gas-phase chemistry of these groups in a multifunctional compound. The results revealed that under the collision-induced dissociation conditions used for the MS/MS study, protonated timolol undergoes heterolytic, charge-induced cleavages of the amine nitrogen-carbon and ether oxygen-carbon bonds. The mechanism of the cleavages was elucidated by comparing the tandem mass spectra of timolol with those of deuterated timolol. This comparison clearly indicated that ion-neutral complexes are intermediates in the cleavages.