In new electrical insulating oil, this test method provides a quantitative measure of the amounts of 2,6-ditertiary-butyl para-cresol and 2,6-ditertiary-butyl phenol that have been added to the oil. In a used oil, the test measures the amount of these inhibitors remaining in the oil. This test method is suitable for manufacturing control, specification acceptance, and service evaluation.

This test method is used to separate, identify, and quantify the inhibitors with minimal interference and matrix effects.

This test method has also been used successfully to determine the inhibitor concentrations in other insulating liquids such as esters and high-temperature hydrocarbons.

1.1 This test method covers the determination by gas chromatography of 2,6-ditertiary-butyl para-cresol and 2,6-ditertiary-butyl phenol in new and used insulating liquids at concentrations up to 0.5 %. It includes the determination in Type I and II insulating mineral oils as specified in Specification D 3487, but has also been used to measure these inhibitors in other insulating liquids, such as esters and high fire-point hydrocarbons.

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.