How are PCBs in transformer oil detected using laboratory analysis?

PCBs are detected by collecting representative oil samples in clean containers, then extracting and analyzing them in a certified lab. The most common method uses gas chromatography with sensitive detectors to separate and quantify PCB congeners or Aroclor mixtures. Results are reported as concentration, usually in mg per kg or ppm. Quality controls include blanks, calibration standards, and duplicate runs. The outcome determines regulatory classification and required handling and disposal procedures.