The first part of the review contrasts the main drawbacks of silica-based packings such as their relative thermal and chemical instability with excellent stability of metal oxides. The paper concerns mainly ZrO2, TiO2 and Al2O3. Methods of preparation of spherical particles for HPLC are described. Surface chemistry of the oxides is, however, very different from that of silica. Ability of the oxides to ion- and ligand exchange is discussed from a chromatographic point of view.
See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.N O V E M B E R 1 , 2 0 0 1 / A N A LY T I C A L C H E M I S T R Y 5 9 9 A hirty-eight new reversed-phase (RP) columns with various stationary phases were introduced at Pittcon 2001-a stark contrast to the early days of HPLC when, to paraphrase Henry Ford, you could get any kind of column you liked as long as it was an octadecyltrichlorosilane (ODS) modified-silica column (1). Currently, stationary phases for HPLC range from the large family of RPs, including those based on the chemical inertness of zirconia (ZrO 2 ), to highly selective, nearly specific, bioaffinity phases.With an emphasis on RPs, technology is aimed at improving column durability under adverse conditions (especially high pH), column-to-column and batch-to-batch reproducibility, peak tailing toward cationic (basic) analytes, unique selectivities, and speed. Columns are also designed for specific areas, such as LC/MS, and for specific improvements, such as minimal solvent consumption. Recently introduced polar-embedded phases that provide unique selectivity and can be used in highly aqueous media have become particularly popular.Many new phases have emerged from research directed at producing more durable materials, understanding and minimizing silanol-analyte interactions, and addressing the need for more selective separations in all modes of LC (2-5). Another important trend has been the development of spe cifi cally nonporous silica and zirconia particles and shorter and wider column geometries for faster analysis times (6).Most new phase development work focuses on silica-based materials; however, silica's inherent instability at pH > 7-8 and higher dissolution rates at elevated temperatures significantly limit the range of aqueous media conditions. Stabilized silicas, hybrid inorganic-organic particles, and novel support materials-synthetic organic polymers, alumina, and other metal oxides-have been designed to overcome these shortcomings (7-9).
Peter W. CarrUniversity of Minnesota Z Zi ir rc co on ni ia a S St ta at ti io on na ar ry y P Ph ha as se es s f fo or r E Ex xt tr re em me e S Se ep pa ar ra at ti io on ns s
This review explores the usefulness of zirconia‐based materials in separations in biotechnology. The physical and chemical properties of zirconia are discussed briefly to familiarize the reader with the advantages of zirconia. The use of native zirconia is then examined, with a study of the Lewis acid/base chemistry that defines chromatography with zirconia. Modification of the zirconia surface with small molecules is then discussed. Finally, polymer‐coated zirconia materials are examined. Examples of separations using these various materials are shown. The advantages and disadvantages of each of these materials are presented.
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