GCxGC is one of the fastest growing areas in analytical chemistry. The level of detail it can provide cannot be equaled by any other chromatographic technique. It employs two columns in series, separated by a modulator. The role of the modulator is to collect fractions from the first column (often called the primary column, first dimension column, or 1° column) and focus them onto the second column (often called the secondary column, second dimension column, or 2° column). Primary columns tend to be 30 m x 0.25 mm I.D., whereas 1-2 m x 0.10 mm I.D. is common for secondary columns. Common detectors, including MS, can be used.
One key to the successful operation of GCxGC is that the two columns must have orthogonal selectivity, that is, they must utilize different retention mechanisms. The more different (more orthogonal), the better the overall performance will be. Two strategies can be used for GCxGC column selection to achieve orthogonal selectivity.
