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The Influence of Pump Oil Purity on Roughing Pumps


Santford Overton and John Manura

Pump oils contain a wide variety of volatile organics and the breakdown of these compounds can affect the life of a rough pump and is a major concern to mass spectrometer users. Analytical techniques are needed to identify and quantitate volatile organics 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 techinques are needed to profile and identify VOC's in pump oils so that they can be used to ensure the life of the pump. Headspace GC analysis, cryofocusing techniques, and high- resolution GC have previously been used for the analysis of commercial oils. Static headspace techniques are limited in their detection and identification of many organic volatiles and especially the semi-volatile organics. The purpose of this investigation is to develop an analytical technique that could detect and identify a wide range of volatile and semi-volatile organic compounds in pump oils over time. For this study, volatile organic compounds are purged from oil samples followed by trapping on Tenax® TA adsorbent resin using a dynamic purge and trap technique (P&T). The adsorbent traps are ballistically heated and together with the carrier gas flow through the samples the volatiles are outgassed into the GC injection port and onto the front of the GC column for subsequent analysis by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The volatile organics present in the pump oils are quantified using matrix spiked deuterated standards. The P&T technique permits the analysis of a wider range of both volatile and sem-volatile organic compounds and is more sensitive as compared to the static headspace technique.

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