Page 4 - Subyek Encyclopedia - Encyclopedia of Separation Science

FOREWORD vii

Foreword

Separation science was Rrst recognized as a distinct area of physical and analytical chemistry in the 1960s. The
term was Rrst coined, I believe, by the late J. Calvin Giddings, Research Professor at the University of Utah.
Calvin Giddings recognized that the same basic physical principles governed a wide range of separation
techniques, and that much could be learnt by applying our understanding of one such technique to others. This
was especially true for his Rrst loves, chromatography and electrophoresis and latterly Reld Sow fractionation.
Of course there are many separation techniques other than chromatography, many with a history at least as
long, or indeed longer, than that of chromatography: distillation, crystallization, centrifugation, extraction,
Sotation and particle separation, spring to mind. Other separation techniques have emerged more recently:
afRnity separations, membrane separations and mass spectrometry. Most people, a few years ago, would
not have classed mass spectrometry as a separation technique at all. However, with modern ionization
methods, which minimize fragmentation, mixtures of compounds can Rrst of all be separated and then each
component identiRed through fragmentation by secondary ion-molecule collisions and further mass spectro-
metry. With the scale of mass spectrometry now matching that of microseparation methods such as capillary
electrophoresis and capillary electrochromatography, combinations of orthogonal methods can now provide
extremely powerful separation and identiRcation platforms for characterizing complex mixtures.
Basically, all separation techniques rely on thermodynamic differences between components to dis-
criminate one component from another, while kinetic factors determine the speed at which separation can be
achieved. This applies most obviously to distillation, chromatography and electrophoresis, but is also obvious
in most of the other techniques; even particle size separation by sieving can be classiRed in this way. The
thermodynamic aspect is, of course, trivial being represented by the different sizes of the particles, as
indeed it is for the size exclusion chromatography of polymers. However, the kinetic aspects are far from
trivial. Anyone who has tried to sieve particles will have asked the question: is it better to Rll the sieve nearly to
the top and sieve for a long time, or is it better to dribble the material slowly into the sieve and just remove the
heavies from time to time? One might further ask: how does one devise a continuous sieving process where
large particles emerge from one port of the equipment, and small ones emerge from the other port? And how
does one optimize throughput and minimize unit cost?
The publication of this Encyclopedia of Separation Science is a landmark for this area of science at the start
of the third millennium. It will undoubtedly be of enormous value to practitioners of separation science
looking for an overview and for guidance as to which method to select for a new problem, as well as to those
who are at an early stage, simply dipping their toes into the waters, and trying to Rnd out just what it is all
about. Most important of all, by providing a comprehensive picture, it advances the whole Reld of separation
science and stimulates further work on its development and application. The publishers, their editors and their
authors are to be congratulated on a splendid effort.

John H. Knox
Edinburgh
8 March 2000