Thermogravimetry (TG) was employed to understand the interactions between ionic liquids (ILs) and biomass components. The thermal decomposition profiles of several biomass samples with IL pretreatment at different temperatures were studied by TG. Samples of Avicel (PH101), xylan from beechwood and alkaline lignin as well as switchgrass and corn stover were pretreated using 1-butyl-3-methylimidazolium acetate ([C4mim][OAc]) at temperatures of 50-130 degrees C for 6 h. Analysis of TG data provided insight into the mode of degradation of xylan and lignin in [C4mim][OAc]. Pretreated Avicel samples exhibited higher decomposition temperatures due to transformation from cellulose I into cellulose II, while samples of switchgrass and corn stover showed an improved thermal stability as a result of removal of minerals by [C4mim][OAc]. More intensive pretreatment produced decreased thermal resistance due to degradation of biomass components and decrystallization. (C) 2013 Elsevier Ltd. All rights reserved.