Diastereomeric clusters of general formula [MAB2]+ and [MA2B]+ (M = Li(I), Na(I), Ag(I), Ni(II)-H, or Cu(II)-H; A = (R)-(-)- and (S)-(+)-(1-aminopropyl)phosphonic acid; B = (1R)-(-)- and (1S)-(+)-(1-aminohexyl)phosphonic acid) have been readily generated in the electrospray ionization (ESI) source of a triple-quadrupole mass spectrometer and their collision-induced dissociation (CID) investigated. CID of diastereomeric complexes, e.g. [MAS(BS)2] + and [MAR(BS)2]+, leads to fragmentation patterns characterized by Rhomo = [MA SBS]+/[M(BS)2] + and Rhetero = [MARBS] +/[M(BS)2]+ abundance ratios, which depend upon the relative stability of the diastereomeric [MASB S]+ and [MARBS]+ complexes in the gas phase. The chiral resolution factor Rchiral = Rhomo/Rhetero is found to depend not only on the nature of the M ion but also on that of the fragmenting species, whether [MAB 2]+ or [MA2B]+. The origin of this behavior is discussed. Copyright © 2005 John Wiley & Sons, Ltd.

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