The presence of chlorinated hydrocarbons such as trichloroethylene [CAS 79-01-6] and tetrachloroethylene [CAS 127-18-4] in marine fuels, including gas oil, can lead to accelerated corrosion to fuel pumps, valves and, ultimately, catastrophic engine failures. The two chlorinated compounds mentioned previously are used extensively as highly effective degreasers of metal parts in the automotive and other metal-working industries. The presence of these compounds in marine fuels can arise from cross-contamination of blending fuels with cutter stocks of unregulated quality, or illegal disposal of chemical waste in fuel. A practical gas chromatographic approach has been successfully developed for the accurate measurement of these compounds using a five-port planar microfluidic device configured as a Deans switch for multidimensional gas chromatography (MDGC) with a flame ionization detector (FID).