Fourier transform infrared (FT-IR) spectrometry to detect additives and contaminants in insulating oils

Over the past ten years, the development of IR has evolved dramatically with the development of analog to digital converters, signal treatment, dedicated computers, etc. This paper shows that FT-IR is useful for the detection of additives or undesirable impurities at low content (<100 ppm) without preliminary extraction by using a spectra accumulation technique combined with a spectra subtraction technique in conjunction with a collection of pure compound spectra as a database. The detection limit in comparison to classical IR analysis is reduced by approximately a factor of seven by an improvement of the signal-to-noise ratio.