Chromatography is the most widely used separation technique in chemical laboratories, where it is used in analysis, isolation and purification, and it is commonly used in the chemical process industry as a component of small and large-scale production. In terms of scale, at one extreme minute quantities of less than a nanogram are separated and identified during analysis, while at the other, hundreds of kilograms of material per hour are processed into refined products. Today chromatography is used by many different scientific disciplines--and just as the technique has fostered advances in research, the advances have broadened and sharpened the chromatographer's capabilities and range of applications. For example, a medicinal chemist who makes a new drug must purify it from unwanted and possibly toxic byproducts that were made in a chemical synthesis. An environmental researcher may need to use the method to measure the levels of hazardous chlorohydrocarbons in the tissues of Great Lakes fish to assess whether they are safe for human consumption. The numerous applications of chromatography drive researchers to develop systems that will separate mixtures better, detect smaller amounts of material in a sample, and do it in a shorter amount of time.