Ionspray ionization and tandem mass spectrometry of Li+ or NH4+ coordinated 1 : 1 gamma-cyclodextrin/12-crown-4-ether double macrocyclic inclusion complex

Ionspray mass spectrometry (MS) of a water-acetonitrile solution of 1:1 gam ma-cyclodextrin (gamma CD)/12-crown-4 ether (12-C-4) double macrocyclic inc lusion complex added with LiBr and ammonium acetate allowed the detection o f 1:1:1 gamma CD/12-C-4/Li+ or NH4+ gaseous associations, which were charac terized by tandem-MS experiments performed with a triple quadrupole analyse r. The low energy collision-induced dissociation (CID) products were both g amma CD and 12-C-4 cationated with Li+ or NH4+, respectively. The CID of 1: 1:1 gamma CD/12-C-4/NH4+ also yielded protonated gamma CD and 12-C-4. Li+ o r NH4+ cationated gamma CD were more abundant than the corresponding cation ated 12-C-4. These results suggested preferential cationization of gamma CD at the external hydrophilic surface with respect to 12-C-4 cation inclusio n within the 1:1 double macrocyclic complex for entropy and steric hindranc e reasons. Nevertheless, the 12-C-4 cationization did yet even occur to a s ignificant extent, thus providing support for the surviving capability of a cationated gaseous CD host-guest complex with the charge located within th e host cavity. (Int J Mass Spectrom 193 (1999) L1-L6) (C) 1999 Elsevier Sci ence B.V.