Fast atom bombardment mass spectrometric and tandem mass spectrometric investigation in thioglycerol on protonated non-covalent associations of Beta-cyclodextrin with 2-acetyl, 2-propionyl-1-pyrroline and 5-acetyl-2,3-dihydro-1,4-thiazine, roast smelling odorants in food. Role of the matrix

[object Object]2-Acetyl-1-pyrroline (1), 2-propionyl-1-pyrroline (2) and 5-acetyl-2,3-dihydro-1,4-thiazine (3), roast smelling odorants in food, form stable inclusion compounds with ?-cyclodextrin. Fast atom bombardment (FAB) mass spectra of such complexes in thioglycerol showed abundant [G+Hs+Mx+H]+ ions, where G=guest (1, 2 or 3), Hs=host (?-cyclodextrin) and Mx=one molecule of matrix, consistent with protonated non-covalent three-component adducts, and nearly negligible 1:1 associations of the type [G+Hs+H]+. Collision-activated decomposition (CAD) experiments indicated that [G+Hs+Mx+H]+ are made of neutral ?-cyclodextrin and protonated 1:1 guest-matrix adducts. The nature of these latter adducts was investigated by FAB mass spectrometric experiments on 1, 2 and 3 in thioglycerol without ?-cyclodextrin. In all cases the most intense signals are due to [G+Mx+H]+ and [G+H]+, with a small contribution of [G+Mx-H2O+H]+ to the total ion current. CAD experiments on [G+Mx+H]+ afforded protonated guest molecules as the base peak, consistent with the decomposition of protonated non-covalent 1:1 guest-matrix associations, possibly mediated by an intermolecular hydrogen bond. According to these data, there is a significant contribution of non-covalent three-component associations to [G+Hs+Mx+H]+ complexes, although the possibility of the formation of covalent guest-matrix adducts is not ruled out definitely, as discussed in the text. © 1997 by John Wiley & Sons, Ltd.