mineral oil analysis using gas chromatographyThis blog post covers a really interesting gas chromatography (GC) method development that came about as a result of a customer request from Brazil. As a signatory of the Kyoto Protocol, Brazil needs to initially reduce the amount of polychlorinated Biphenyls (PCBs) (U.S. EPA page) in the mineral insulating oils used in electrical transformers and capacitors, and then completely eliminate the use of PCBs in the insulating oils in 30 years! As a result, not only is the determination of PCBs in transformer oil now mandatory in Brazil, but the total PCB concentration now must be below 50 ppm for the oil to be transported or sold.

Customer requirements for this new method included increasing the level of automation to reduce contamination and lab personnel exposure to the harmful chemicals, improve sample traceability, and improved reporting; a reduction in the number of consumables and glassware used for sample clean-up; and, a reduction in the number of expensive standards used. By the way, as the state of San Paulo in Brazil alone has at least 200,000 transformers, one can understand the method requirements.

The new GC method described in Poster Note 10327, Method Development for a Simple and Reliable Determination of PCBs in Mineral Insulating Oil by SPME-GC-ECD, (downloadable PDF) uses one of our latest GC systems (Thermo Scientific TRACE 1300 Series Gas Chromatograph) equipped with an autosampler (Thermo Scientific TriPlus RSH Autosampler), a Electron Capture Detector (ECD) module (Thermo Scientific Instant Connect ECD Module), and a GC injector module (Thermo Scientific Instant Connect Injector Module). Advantages of the system set up are included.

Four sample preparation methods are compared: automated SPME, manual SPME, Solid-Phase Extraction (SPE) with a Florisil cartridge, and SPE with sulfoxide. The results indicate that SPME and sulfoxide provided much higher accuracy, SPME can be used to improve process and method consistency, and it enables the scaling-down of volumes.

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Method precision was confirmed by testing 29 oil samples and 2 standards over 7 consecutive days. Note that the proposed method is able to determine the total PCB content in new transformer oils, as well as in old, oxidized oils.

This application joins a growing number of chromatography applications including sample preparation for POPs analysis on this blog that you might be interested in viewing.

Do let us know if you have questions on this application by using the Comments box below. Our application chemists will be pleased to hear from you.