An analysis of 2,6-di-tert-butyl-p-cresol in insulating oils by high-performance liquid chromatography

The presence of antioxidant is the key factor in controlling the oxidation of an insulating oil. Any monitoring program set up to keep track of its concentration could result in substantial savings by prolonging the oil service life and slowing down the transformer aging process. This paper describes a method for measuring the amount of the antioxidant 2,6-di-tert-butyl-para-cresol (DBPC) in new or service-aged insulating oils by high-performance liquid chromatography (HPLC) using a Hamilton PRP-1 column (10 μm) and an ultraviolet detector (283 nm). The mobile phase is a mixture of acetonitrile-water (97.5/2.5, v/v) with a flow rate of 1 cm³/min. The byproducts from DBPC, oil oxidation and oil components, whose retention time in HPLC is identical to that of DBPC, were eliminated by filtering the oil on a Sep-Pak Classic silica cartridge. The proposed method has a detection limit of 2.0 ppm and a precision better than 1.7%