Before the advent of gas chromatography (GC) in 1952, fractional distillation was the most widely used analytical method based on volatilization of samples. Extremely refined distillation techniques had been developed, especially in the petroleum industry, but these had several important limitations. The power of separating compounds of closely similar boiling points was inadequate; the methods usually required large samples and were quite inappropriate for even the milligram range; minor components of mixtures were not readily detected, and thermal decomposition of samples was a frequent problem.