Preparation And Characterization Of Alumina And Modified Alumina Stationary Phase For High-Performance Liquid Chromatograph

Metal Oxides, especially zirconia and alumina have been found to be complementary column packing materials of silica for High ?Performance Liquid Chromatograph,both of them even showing some advantages of physico hemical properties over silica. However their applicabilities are often limited by the poor pore structure of zirconia and the difficulty of modifying alumina surface. The purposes of our studies are to improve the pore structure of zirconia and to make the modification of alumina easy and effective. The main researchs and conclusions in this thesis are as follows: (i)Zirconialurnina particles were prepared by the sol-gel process. Most physical properties of them such as pore structure, particle size and specific surface area were studied. The particles were then modified with 13-aminoethyl phosphoric acid and served as a new stationary phase. whose chromatographic performance was evaluated by using ethanol ?oyelohexane, chloroform ? oyclohexane as mobile phase. The distinctive chromatographic behaviors of some aromatic compouds on the modified columm of Zr02-A1203 and the columm of Zr02-A1203 indicated that it was practable for Zr02-A1203 to be modified with f3- aminoethylphosphoric acid. Basic compounds such as pyridine~ aniline and derivatives of them had symmetrical peaks, with poorly shaped peaks of phenols and polyeyclic aromatie hydrocarbons (PAHs) absorbed poorly on the modified stationary phase. The logk of some derivatives of aniline had a good linear relationship with the content of eluent in the mobile phase. (ii) The particles of alumina were prepared by acid erosion. The chromatographic performance of the column were investigated with PAHs. acidic compounds and basic compounds as solutes. Acidic compounds were absorbed strongly on the column, parts of them having irreversible absorption on the stationary phase; basic compounds had reasonable retention with symmetrical peaks; PAHs were eluted with little absorption. All above investigations showed that there were Bronsted acid sites and Lewis acid sites on the surface of alumina. (iii) Taking advantage of Lewis acid sites on the surface of alumina, we modified the columm of alumina with a Lewis base of minoethylphosphoric acid. The chromatographic performance of the modified column was evaluated under binary eluents and compared with that of the column of alumina. The results showed that the lewis acid sites on the surface of alumina were entirely covered with minoethylphosphoric acid. Acidic compounds could be eluted yet with poorly symmetrical peaks. The retention behaviors of PAHs have difference from ones on the column of alumina; The seperating factors of some compunds were also improved greatly. (iv) We succeed in preparating the column of alumina modified with P- cyclodextrine, and studied the retention behaviors of aromatic compounds on the a-CD-modified column. The comparision of the n-CD-modified column with the aminoacid-modified one confirmed the existence of inclusion equilibrium between yclodextrine and sample molecules. The capacity factors of the sample generally incresed by virtue of the specific interaction between j3- cyclodextrine and sample molecules. The effects of the substituents and their relative postion on the aromatic rings and the mobile phase were examined, some enanitiomers were seperated suceessfully. Key words: Zirconia-alumina,alumina,β-a...