Metalloporphyrins in fast atom bombardment mass spectrometry: implications for processes occurring in the liquid matrix

Abstract

The use of fast atom bombardment mass spectrometry is investigated as a technique to study a series of porphyrins (H{sub 2}P) and metalloporphyrins (MetP). Rates of demetalation and the redox chemistry of such compounds as well as complex inter- and intramolecular electron-transfer processes are examined. Comparison of the solution chemistry of metalloporphyrins with their behavior in FABMS lead to an understanding of various aspects of the physicochemical events occurring in the FAB matrix. By using FAB matrices with different electronic or acidic properties it is demonstrated that demetalation can occur either by proton displacement or one-electron reduction of the metal. It is also shown that demetalation by protons in FABMS correlates with stability index (S{sub i}) and that the (H{sup +}) in the FAB matrix is {approximately} 2 {times} 10{sup {minus}4} M.