ABSTRACT
Lilach Yishai-Aviram and Eli Grushka Department of Inorganic and Analytical Chemistry, The Hebrew University, Jerusalem, Israel
I. INTRODUCTION 274
II. THE PRINCIPLE OF DYNAMIC COATING 276
III. COLUMN CHARACTERIZATION 279
IV. POSITIVELY CHARGED POLYELECTROLYTES
AS STATIONARY PHASES 282
A. Coating Procedures 282
B. Properties of the Phases and Retention
Mechanism 284
C. Applications 289
V. NEGATIVELY CHARGED POLYELECTROLYTES
AS STATIONARY PHASES 289
A. Coating Procedures 289
B. Properties of the Phases and Retention
Mechanism 291
C. Applications 297
VI. COMPLEX POLYELECTROLYTE LAYERING 298
REFERENCES 298
Chemicallymodified silicas are used ubiquitously as stationary phase
support in liquid chromatography (LC). In spite of alternative column
packing, such as zirconia, alumina, titania, etc., silica continues to be
the most commonly used packing material in modern LC. The main
advantages of silica are its high level of mechanical strength, uni-
formity in terms of size and surface area, and purity. These qualities
permit the formation of efficient packed beds that remain stable under
high operating pressures for long periods of time [1]. The surface of
silica consists of various kinds of silanols and siloxane bonds [2,3].
The siloxane (Si-O-Si) sites are hydrophobic and contribute little or
nothing to the retention of polar solutes. However, the hydrophobic
nature of the siloxane bond makes it possible to observe some
retention of nonpolar solutes [4]. On the other hand, the silanol
groups, which can be hydrated by adsorption of water, are polar
and are considered to provide strong adsorption sites [3,5,6]. Basic
analytes can interact strongly with the acidic silanols.
