This topic has been selected from the book, "Analytical Chemistry", written by G. D. Christian and others. Topic: Gas Chromatography. Learning points are: Gas chromatograph. GC columns- packed, capillary. Stationary phase polar to nonpolar. GC detectors. Temperature programming. Quantitative measurement-internal standards. Headspace analysis, thermal desorption, purging, and trapping. Small columns for fast separations. 2-D gas chromatography.