Column packings zirconia

Figure 18-6. UPLC chromatography of benzodiazepines on a 14.5-cm x 50- xm column packed with l- xm polybutadiene-encapsulated non-porous zirconia particles. Eluent pH 7 buffer-acetonitrile 68 22 at 100°C. Peaks 1, uracil 2, clorazepate 3, fluni-trozepam 4, clonazepam 5, chlordiazepoxide 6, oxazepam 7, clorazepate 8, diazepam. (Reproduced from reference 53, with permission from Elsevier.)...

Columns packed with porous, polymeric particles such as divinylbenzene cross-linked polystyrene, substimted methacrylates, and polyvinyl alcohols can also be used for HPLC method development " as can modified alumina and zirconia stationary phases. ... 

Zhang, Q.H. Feng, Y.Q. Yan, L. Da, S.L. Wang, Z.H. Retention behavior of solutes on liquid chromatographic column packed with dynamically modified zirconia. Chin. J. Chromatogr. 1999, 17, 229-231. 

Fig. 5 Chromatograms obtained on four mixed oxide packing materials. Solute 1 = benzene 2 = dimethyl phthalate 3 = pyridine. Column packing material (a) silica-zirconia (b) silica-alumina (c) silica-titania (d) silica-magnesia (e) silica gel. Mobile phase, -hexane containing 1% methanol flow rate, 1 mL/min column temperature, ambient detection, UV 254 nm. (From Ref. [1].)...

Retention behavior of solutes on liquid chromatographic column packed with dynamically modified zirconia. Chin. 

Porous zirconia particles coated with polybutadiene make a reversed-phase HPLC column packing that offers both excellent pressure stability and chemical inertness throughout the entire pH range. Because of the complex surface chemistry of zirconia, mobile phase additives such as phosphate or fluoride are added to facilitate the separa-... 

Another approach to increase HPLC speed is the use of higher temperatures. The viscosity of a typical mobile phase used in reversed-phase separation decreases as the column temperature is increased. This allows an HPLC system to operate at a higher flow rate without suffering too much from increased back pressure. Zirconia-based packing materials provide excellent physical and chemical stability. They have been used successfully for high-throughput bioanalysis at elevated temperatures.9... 

This chapter deals with the properties of high-pressure liquid chromatography columns. It is divided into two sections column physics and column chemistry. In the section on column physics, we discuss the properties that influence column performance, such as particle size, column length and column diameter, together with the effect of instrumentation on the quality of a separation. In the section on column chemistry, we examine in depth the surfaces of modern packings, as well as the newer developments such as zirconia-hased packings, hybrid packings or monoliths. We have also included a short section on... 

The stability of zirconia and zirconia-based packings also allows the use of these columns at an elevated temperature. The key advantage of this is the reduction in analysis time due to the reduction in the viscosity of the mobile phase. In addition, the much broader temperature range also permits a fine-tuning of the selectivity of a separation compared with silica-based packings. 

FIGURE 9.1 Chromatograms showing the effect of temperature on the separation of aUcylphenones. Experimental conditions mobile phase A, 30% ACN (v/v) and flow rate is 4mL/min at 25°C mobile phase B, 25% ACN (v/v) and flow rate is 15mL/min at 150°C. Peaks 1, acetophenone 2, octanophenone 3, decanophenone 4, dodecanophenone 5, tetradecanophenone. Column 50x4.6 mm packed with 2.5 pm polystyrene coated zirconia. (Reprinted from Yan, B. et al.. Anal. Chem., 72, 1253, 2000. Copyright 2000, American Chemical Society. With permission.)... 

A few applications have employed conventional packed columns, although recent developments in new thermally stable stationary-phase materials have generated a renewed interest and the temperature stability of the different stationary-phase materials has been reviewed by Claessens and van Straten [43]. The new materials have included stable metal oxide materials, based on zirconia (Figures 18-4 and 18-5) and titania [44, 45] and hybrid phases combining silica and methylene or ethyl bridges [46]. These have been applied in a number of applications to pharmaceutical compounds (Table 18-1). 

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