| High performance liquid chromatography (HPLC) is one of the most useful and popular separation techniques. Stationary phases or column packings are key factors in promoting the development of HPLC. Zirconia is very suitable for HPLC as an alternative to silica due to its excellent chemical stability, mechanical stability and thermal stability. There are large numbers of Lewis sites on zirconia surface. It is easy to get a useful stationary phase by modified zirconia with Lewis bases (L-base), which had been proved by some commercial products and patents. Although zirconia material is very stable at wide range of pH values and under very high pressure, the zirconia stationary phases modified with L-bases is not very stable; and more, acidic solutes such as phenols and carboxylic acids give the chromatographic peaks tailed on these kind of stationary phase, or even cannot be eluted. So before any L-bases modified zirconia stationary phases become more useful and more popular stationary phases, these questions must be resolved. In this dissertation, attempts had been done by modified zirconia with multi-dentate L-bases, we hope that the multi-dentate L-base should increase the stability of zirconia-based stationary phases and decrease the amount of the Lewis acid sites on the surface of zirconia. The major contents studied are as follows:1. The application of zirconia as HPLC stationary phase is reviewed; the methods of modification are introduced in detail.2 A new zirconia-based stationary phase was prepared for the first time by modification with dodecylamine-N,N-dimethylenephosphonic acid (DDPA). DDPA adsorbs on zirconia only with one phosphonate group. The stationary phase (DPZ) has not only long alkyl groups, but also amino and free phosphonate groups. The chromatographic property of the stationary phase is strongly influenced by the polar groups. The high selectivity and excellent resolution for PAHs, amines and phenols were obtained, a great improvement also achieved for separation of benzoic acids.IV3. Chromatographic performances of DPZ were investigated under various conditions by using disubstituted benzene isomers as probe. Despite the lower surface coverage of the DPZ than silica-based reversed phase packings, the disubstituted benzene positional isomers with polar group (-NH2, -OH, -NOi) exhibit the greater capacity factors on DPZ. The high separation selectivity and excellent resolution were obtained due to the mixed-mode retention mechanism provided by various groups, especially the inner polar groups of the stationary phase.4. Separations of sulfonamides, nucleosides and bases were also systematically investigated. The hydrophobic interaction is the major factor for the retention of these solutes, pH values of the mobile phase also exhibit the significant influences on the capacity factors and separation selectivity of the solutes, because pH values of mobile phase change the species not only of the polar solutes, but also the polar groups of stationary phase.5. Various di-dentate L-bases which have the structure similar to DDPA were synthesized, including dodecylamine-N,N-dimethylenephosphonic acid (DDPA or RNPP); dodecylamine-N-acetic acid-N-methylenephosphonic acid (RNCP); dodecylamine-N,N-diacetic acid (RNCC), dodecencylsuccinic acid (RCC), and their modified zirconia-based stationary phase was prepared. The adsorption mode, stability and chromatographic performance (especially the separations of acidic solutes) were studied in detail on zirconia stationary phase modified with these di-dentate L-bases. The adsorption modes were confirmed by FTIR and color reaction: RNPP, RNCP and RNCC adsorb on zirconia with only one Lewis basic group and another Lewis basic group shield the Lewis acid sites on zirconia due to the chelating effect. Quiet differently, RCC has no chelating effect with zirconia, so it adsorbs on zirconia with both carboxylic groups, which enhance the stability of stationary phase modified.6. A new zirconia-based stationary phase(BPZ) was prepared by modi...
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