RETENTION OF NEUTRAL SOLUTES IN CAPILLARY ELECTROCHROMATOGRAPHY

The retention mechanisms of neutral solutes were compared between elec trically driven chromatography and pressure driven chromatography. The entropies of solute transfer from a mobile phase to a stationary phas e were more negative in electrically driven chromatography than in pre ssure driven liquid chromatography. These differences can be attribute d, in part, to the generation of heat which occurs during electro-driv en chromatography and which causes significant differences between the set and the actual column temperature. Retention factors in electroch romatography are affected significantly by changes in electric field s trength. These variations can be minimized by performing the experimen ts at elevated column temperatures. For example, when the column tempe rature was increased from 293 K to 333 K,the RSD for pentachlorobenzen e was lowered from 7.3 % to 4.3 %. In addition the analysis time was s hortened by approximately 45 %. Due to the critical effect of temperat ure on separation in electrochromatography, it is imperative that the column temperature be kept constant and measured accurately.