Optical absorption, fluorescence, and quantitative <sup>13</sup>C NMR spectroscopy have been used to study the degradation of mineral gearbox oil. Samples of used oil were collected from field service. Measured absorption, fluorescence, and quantitative <sup>13</sup>C NMR spectra of used oils show characteristic changes from the spectra of a fresh oil sample. A clearly observable, ~20-nm blueshift of the fluorescence emission occurs during the early stages of oil use and correlates with changes in intensity of some specific <sup>13</sup>C NMR resonance lines. These changes correlate with oil age because of the connection between the blueshift and breaking of the larger conjugated hydrocarbons of oil as a result of use.
© 2004 Optical Society of America
(120.4290) Instrumentation, measurement, and metrology : Nondestructive testing
(120.4630) Instrumentation, measurement, and metrology : Optical inspection
(300.1030) Spectroscopy : Absorption
(300.6280) Spectroscopy : Spectroscopy, fluorescence and luminescence
Jarmo Vanhanen, Marcus Rinkiö, Jukka Aumanen, Jouko Korppi-Tommola, Erkki Kolehmainen, Tuula Kerkkänen, and Päivi Törmä, "Characterization of Used Mineral Oil Condition by Spectroscopic Techniques," Appl. Opt. 43, 4718-4722 (2004)