This book covers the essentials of gas chromatography (GC), including the theory, method development, quality assurance and validation, troubleshooting, and new developments in the field. The emphasis is on the application of GC in a range of relevant forensic applications, including those related to drugs, toxicology, food and flavors, fire, paint, the environment, and explosives. Individual case studies of applications are focused on specific sample preparation techniques. Each sample preparation technique is discussed with respect to its theory, instrumentation, solvent selection, and function. Techniques include solid phase extraction, solid phase microextraction, solvent extraction, purge and trap, thermal desorption, and pyrolysis.