Since its infancy in the late 1960s and early 1970s, the use of high perfor­ mance liquid chromatography (HPLC, or LC as it is increasingly becom­ ing known) has expanded rapidly. Today, it is a highly popular analytical technique which is extensively used in many fields of activity. Not surpris­ ingly, it has been the inspiration for much scientific literature, including a significant number of books. These books have taken various forms, such as practical handbooks, modified short-term manuals, reports on selected topics, theoretical treatises and even attempts at comprehensive works. In almost every way, HPLC may be regarded as a mature technique. However, there is one sense in which it is still developing. Only recently has its importance been acknowledged by accepting it as a subject worthy of inclusion in undergraduate science courses. The aim of this book is therefore to support the newly acquired status of HPLC by providing a presentation of the technique primarily aimed at undergraduate students on courses containing a significant component of analytical science. The intention has been to come up with a different slant to that already avail­ able, characterised by an emphasis on understanding. Why is HPLC so useful? When should it be used? What is the reason for certain practices? Most importantly, how does HPLC work? The responsibility to deliver a thorough coverage of theory has not been shirked.