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 des orption-ionization time-of-flight mass spectrometry [MALDI-MS (TOF)] a re suitable, mutually complementary methods for characterizing oligome ric ethylene oxide adducts. While SFC is successfully applicable in th e low-molecular-size range up to molar masses of ca. 1000 g/mol, MALDI -MS facilitates proper differentiation also in higher molar mass range s. In the lower molar mass ranges down to approximately degree of poly merization n = 6, the problem of discrimination arises when MALDI-MS i s applied; this problem is reduced considerably through the addition o f lithium chloride instead of sodium or potassium ions, a measure whic h also eases identification of the molar peak. Provided that the ethyl ene oxide chain is known, it is also possible to definitely determine substituents in the molecule (e.g., alkyl or arylalkyl chains). By-pro ducts, which may arise, for example, when water is split off during th e reaction or during storage, can be detected.