A commercial vegetable oil-based polyol for rigid polyurethane foams has been characterized by liquid chromatography-electrospray ionization-quadrupole ion trap mass spectrometry (LC-ESI-QIT-MS). The absolute molecular weight (MW5960) was measured by gel permeation chromatography (GPC) equipped with both refractive index (RI) detector and static laser light-scattering detector (SLSD), which allowed further analysis by LC-MS. The oligo-polyol mixture was first separated in two elutes and then investigated by a deep multistage mass spectrometry (MSn) study and completed using NMR. The major constituents identified were regioisomers of propoxylated sucrose (nPO56-12), and the related esters of C16:0, C18:1, and C18:2 fatty acids had a mass ratio of 6:3:1. A comparison of fatty acids composition between the sample and palm oil demonstrated that the sample was initially prepared from the mixture of sucrose and palm oil by direct propoxylation. The MS n fragmentation studies validated the structure of propoxylated sucrose and the related fatty acids derivatives. (C) 2016 Wiley Periodicals, Inc.