GCxGC uses 2D imaging as we have two ‘dimensions’ of separation during the chromatographic process. Analytes are separated over time as is traditional, but using a second polar column each time the separated fraction is then split further into the various aliphatic and aromatic species.
The 2D image here is a Diesel and Mineral Oil Standard. The peaks split in the horizontal direction over the 26-minute run time but there is a second axis of separation as those peaks are further spread out based on the nature of the species present.
Along the back of the ‘box’ there is a single white trace which is the equivalent of the more traditional Total TPH trace; essentially a sum of all the various species present.