Molar mass determination of oligomeric ethylene oxide adducts using supercritical fluid chromatography and matrix-assisted laser desorption—ionization time-of-flight mass spectrometry

Abstract Supercritical fluid chromatography (SFC) and matrix-assisted laser desorption—ionization time-of-flight mass spectrometry [MALDI-MS (TOF)] are suitable, mutually complementary methods for characterizing oligomeric ethylene oxide adducts. While SFC is successfully applicable in the low-molecular-size range up to molar masses of ca. 1000 g/mol, MALDI-MS facilitates proper differentiation also in higher molar mass ranges. In the lower molar mass ranges down to approximately degree of polymerization n = 6, the problem of discrimination arises when MALDI-MS is applied; this problem is reduced considerably through the addition of lithium chloride instead of sodium or potassium ions, a measure which also eases identification of the molar peak. Provided that the ethylene oxide chain is known, it is also possible to definitely determine substituents in the molecule ( e.g. , alkyl or arylalkyl chains). By-products, which may arise, for example, when water is split off during the reaction or during storage, can be detected.