Multiplexed dual first-dimension comprehensive two-dimensional gas chromatography-mass spectrometry with contra-directional thermal modulation.

•A comprehensive two-dimensional GC approach with multiplexed dual first-dimension columns is introduced.•Dual first-dimension columns are multiplexed using a contra-directional thermal modulation.•The approach uses one injector, three columns and one detector.•Two sets of linear retention indices are collected to support MS identification of separated compounds.