Rapid and Specific Determination of Contaminants, By-Products, and Additives in Insulating Mineral Oils with Tandem Mass Spectrometry

Insulating oils are often considered the life blood of electrical devices such as transformers. Proper functioning of these devices is essential for uninterrupted electrical power over long periods, often stretching into decades. To ensure longevity of insulating oils and improve certain characteristics additives are often added to the oils. On the other hand, the presence of contaminants can deteriorate the performance of the oils and can cause extensive damage to the electrical devices. To ensure optimal operation of electrical devices, additive and contaminant levels should be periodically monitored. Because of the complex chemical composition of insulating mineral oils, the determination of additives and contaminants is a difficult and often laborious task. However, the task can be made manageable with the use of current state-of-the art analytical instrumentation. This article demonstrates the use of electrospray ionization–mass spectrometry for rapid and specific determination of widely used metal deactivators Irgamet 30 and Irgamet 39. The article also presents specific quantitative determination of a highly corrosive sulfur compound dibenzyl disulfide and its principle nonsulfur by-product bibenzyl with gas chromatography and tandem mass spectrometry (GC–MS-MS).