AccuTOF-DART analysis of motor oils
DART can characterize additives in lubricating oils directly without sample preparation. The additives generally produce a strong signal without interference from the base oil. However, complementary information about nonpolar components of the base oil can be obtained by O2 ─• attachment chemical ionization, a simple analysis that can be easily and rapidly carried out with changing any hardware on the AccuTOF-DART mass spectrometer system.
All mass spectra were acquired with a JEOL AccuTOF-DART mass spectrometer equipped with a DARTSVP ion source. Additives in motor oil were analyzed by dipping the sealed end of a melting point tube into each oil sample and suspending the tube in the DART gas stream. The DART was operated in positive-ion mode with helium DART gas and a gas heater temperature of 400°C. The mass spectrometer parameters were: RF ion guide voltage: 600V, ring lens = orifice 2 = 5V, orifice 1 = 20V.