A balanced density slurry-packing apparatus was developed and used to pack sixteen HPLC columns having different lengths and internal diameters with 10 µm Lichrosorb Sl-100. The evaluation of these columns led to several conclusions: the column efficiency, expressed in plates per meter, is a function of the ratio of column internal diameter to column length and increases as this ratio increases; a new definition for preparative efficiency, Time Yield Factor (TYF), is proposed. This factor differentiates among HPLC columns with different lengths and internal diameters using samples of the same volume and concentration; the column that showed the highest TYF value was used for the preparative separation and identification of three positional isomers of high molecular weight (634): 3,4-di(p-bromophenyl)-1,2,5-triphenylcyclo-2,4-pentadien-1-methyl ether; 2,3-di(p-bromophenyl )-1,4,5-triphenylcyclo-2,4-pentadien-1-methyl ether; and 1,2-di(p-bromophenyl )-3,4,5-triphenylcyclo-2,4-pentadien-1-methyl ether, obtained in the synthesis work. / Ph. D.