MOLAR-MASS DETERMINATION OF OLIGOMERIC ETHYLENE-OXIDE ADDUCTS USING SUPERCRITICAL-FLUID CHROMATOGRAPHY AND MATRIX-ASSISTED LASER DESORPTION-IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY

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.