Recent evolution of flow-modulation comprehensive gas chromatography within the context of mass spectrometry hyphenation
Comprehensive two-dimensional gas chromatography (GC×GC) is now a well-established multidimensional GC method, it being introduced nearly 25 years ago (1). In GC×GC, a device named modulator enables the continuous and sequential transfer of “heart-cuts” from a primary to a secondary column. Separations in the second dimension (2D) are usually very rapid, normally less than 10 s. GC×GC data are visualized in a two-dimension (2D) format, with peaks characterized by an ellipse shape, and by first and second-dimension retention times. If desired, more details on GC×GC basic theory can be found in the literature (2).
The modulators used in GC×GC experiments can be classified into two main groups, namely thermal (normally cryogenic) or flow-based systems. Cryogenic modulators are by far the most commonly used, even though they remain an expensive choice. For such a reason, the low hardware and operational costs of flow modulation (FM) makes such an option an attractive one. One of the main reported disadvantages of FM has been the generation of excessively-high gas flows
(> 20 mL min-1), with ...