A crude mixture of randomly methylated beta-cyclodextrin (RAME-beta-CD) has been fractionated by chromatographic column to evaluate the influence of the methylation degree on activity and selectivity of a rhodium/tris(m-sulfonatophenyl)phosphane trisodium salt (TPPTS) catalytic system in hydroformylation of 1-decene. Each sample of methylated beta-cyclodextrin (beta-CD) was carefully analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and electrospray ionization mass spectrometry (ESI-MS). The catalytic activity was found to gradually increase with the number of methyl groups on the methylated beta-CD whereas the chemoselectivity and regioselectivity remained unchanged. (C) 2009 Elsevier B.V. All rights reserved.