The knowledge base of chromatography continued to expand throughout the 1990s owing to its many applications to problems of contemporary interest in industry, life and environmental sciences. Organizing this information into a single text for a diverse group of scientists has become increasingly difficult. The present book stemmed from the desire to revise Chromatography Today, written by the same author with Salwa K. Poole, and published in 1991. This title is considered to be one of the definitive texts on chromatography. It was soon realized however, that a simple revision would not provide the desired result of a contemporary picture of the practice of chromatography at the turn of the century. The only workable solution was to start afresh, maintaining the same general philosophy and concept for Chromatography Today where possible, while creating essentially a new book. The format of the new book is modular, with extensive cross-references to permit rapid location of related material using different separation concepts. Important features are extensive tabulation of essential data for performing separations and an extensive bibliography to the most recent literature. This title is intended as a suitable text for graduate level courses in the separation sciences and as a self-study guide for professional chromatographers wishing to refresh their background in this rapidly expanding field. The Essence of Chromatography presents a comprehensive survey of modern chromatography and is an effective replacement for Chromatography Today.