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Analysis of Motor Oils Using Thermal Desorption-Gas Chromatography-Mass Spectrometry


Santford V. Overton and John J. Manura, Scientific Instrument Services, Inc., Ringoes, NJ

Poster Number - 1112

Motor oils contain a wide variety of volatile organics and the identification and quantification of these compounds are of significant importance to the oil industry. Analytical techniques are needed to identify and quantitate volatile organic compounds (VOC's) present in oils so that these techniques can be incorporated into troubleshooting problems that may arise as well as be used in a quality control program to ensure product purity. In addition, more sensitive techniques are needed to profile and identify VOC's in motor oils so that they can be used in forensic identification. In this study, a new technique entitled "Direct Thermal Extraction" using a thermal desorption apparatus attached to the injection port of a GC/MS system permits the direct thermal extraction of volatile and semi-volatile organics directly from small sample sizes (mg) without the need for solvent extraction or other sample preparation.

The samples are ballistically heated and together with the carrier gas flow through the samples the volatiles are outgassed into the injection port and onto the front of the GC column for subsequent analysis via the GC and/or GC/MS. The "Direct Thermal Extraction" technique offers several unique advantages over the dynamic headspace technique including greater sensitivity and the detection of a wider range of volatile organics including higher molecular weight compounds and has been found to be more sensitive by a factor of at least 1000 as compared to the dynamic headspace technique. The volatile organics present in the motor oils were quantified using matrix spiked deuterated standards. This technique can be easily incorporated into a troubleshooting technique to detect problems in various commercial motor oils, to compare competing manufacturers products, as well as implementation into a quality control program.