Chapter 11 - Introduction - Page 407

     One of the main challenges of separation scientists, in general, is to unravel the chemical profiles of complex, naturally occurring samples. Among the analytical techniques, gas chromatography (GC) is one of the most widely employed for such a purpose. GC was invented >60 years ago, and since then a considerable degree of progress has been made (James and Martin, 1952). The introduction of comprehensive two-dimensional GC (GC x GC) in 1991 by Liu and Phillips represents one of the most important steps toward the increase of separation power. In GC x GC experiments, the separation process is carried out on two columns of different selectivity. An interface, defined as the modulator, is located between the two capillaries, and generates a separation peak capacity, which is roughly equal to the product of the two peak capacities (peak capacity can be defined as “the number of peaks that can be potentially located in the one or two dimensional space, with a specific resolution value”) in each dimension. Comprehensive GC can be considered as an extension of conventional heartcut multidimensional GC, which involves the separation of specific fractions on two different columns with similar lengths. A comprehensive GC separation is obtained when all the components from the first dimension (1D), usually a conventional column (e.g., 25-30 m x 0.25 mm ID x 0.25 um), are reanalyzed on the second dimension (2D), commonly a short microbore capillary segment (e.g., 1-2 m x 0.10 mm ID x 0.10 um). 2D analyses are carried out in a rapid manner, with a duration equal to what is defined as the modulation period (typically in the 4-8 s range). In this chapter, GC x GC fundamentals will be discussed, along with the main applications in the lipid analysis field.