Determination of furanic compounds in insulating oil by high performance liquid chromatography/mass spectrometry using atmospheric pressure chemical ionization

Abstract

A method has been developed to determine furanic compounds in insulating oil matrix using liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization. The examined samples were provided from model experiments and also from several high voltage functioning transformers. To increase sensitivity of the method six furanic compounds (determined by model experiments) were quantified by selected ion monitoring, and quantitation was based on the marker peaks. Oil samples were prepared using solid phase extraction. The results are suitable for evaluation of model experiments and also to solve problems of calibration. From extracts of oil samples taken from functioning transformers cellulose depolymerization products have been identified, and their amounts were found to be valuable in assessing the condition of the transformer (fault diagnosis). # 1998 John Wiley & Sons, Ltd. Received 12 June 1998; Revised 4 August 1998; Accepted 5 August 1998Determination of furanic compounds originating from the thermal depolymerization of cellulose constitutes an important problem in many application fields. For example, in the case of electrical insulation, the quantity and variety of these substances are used to assess performance of insulation in electrical devices. In most cases paper is immersed in insulating oil, which therefore will contain the decomposition products, mainly furan derivatives, and these are monitored in the oil sample. Cellulose degradation is a complex process which is accelerated by the combined effects of temperature and the presence of water and oxygen, which are all available in the environment of transformers. Model experiments suggest that the most important degradation compounds are: 2-furaldehyde, 5-hydroxymethylfuraldehyde, 2-furfuryl-alcohol, 2-acetylfuran, 5-methyl-2-furaldehyde, and 3-furoic acid methyl ester.