Polychlorinated biphenyls (PCBs) were broadly applied worldwide as electrical insulators in transformers and power capacitors, due to their high dielectric constant and non-flammability. They were often added to mineral oils used as dielectric fluids, which are nowadays classified as hazardous waste. Indeed, the Stockholm Convention aims to eliminate the use of equipment with PCB content greater than 0.005 weight-% (= 50 ppm) by 2025. Accurate identification and quantification of small traces of PCBs contained in mineral oil thus represent a great analytical challenge. In order to achieve this goal, a simple, cost-effective and fast chromatographic process was developed to separate PCBs from mineral oil, allowing to obtain reliable data to determine the concentration of PCBs, down to 2-3 ppm. Experimental and analytical methods such as thin layer chromatography, column chromatography as well as gas chromatography coupled with mass spectroscopy (GC-MS) were applied to acquire a high-level of qualitative and quantitative determination of PCBs in transformer mineral oils.