Key factors for capillary electrophoresis of amino acids with indirect ultraviolet detection were investigated. Buffer compositions and additives were found to be influential as expected, while buffer PH was shown to be particularly critical to tile separation and detection. The effect of PH also depended on the electrophoretic mode used. Ways to obtain recurring and selective separations were suggested. Key factors for capillary electrophoresis of amino acids with indirect ultraviolet detection were investigated. Buffer compositions and additives were found to be influential as expected, while buffer PH was shown to be particularly critical to tile separation and detection. The effect of PH also depended on the electrophoretic mode used. Ways to obtain recurring and selective separations were suggested.