Two　convenient,　effective,　and　reproducible　methods　using　microemulsion　electrokinetic　chromatography　(MEEKC)-normal　stacking　mode　(NSM)　and　reversed　electrode　polarity　stacking　mode　(REPSM)　were　developed　for　the　on-line　sample　stacking　of　phthalate　esters　(PAEs).　REPSM　coupled　with　MEEKC　increased　the　sensitivity　of　937　5　to　7　143　times　for　four　PAEs　compared　to　the　conventional　MEEKC.　The　separating　conditions　in　the　MEEKC　method　were　studied,　and　many　factors　influencing　the　two　sample　stacking　processes　were　investigated　in　detail.　The　optimum　sample　matrices　for　the　two　stacking　methods　were　as　follows:　30　mmol/L　sodium　cholate　(SC)　and　30　0　mmol/L　borate　(pH　8　5).　Additionally,　sample　injections　as　large　as　3　45　kPa　×40　s　and　3　45　kPa　×90　s　were　applied　for　NSM-MEEKC　and　REPSMMEEKC,　respectively.　The　linear　relationship　and　reproducibility　were　also　examined.　Under　the　optimum　conditions,　the　detection　limits　(S/N　=3)　of　the　PAEs　were　in　the　ranges　of　0　021　-0　33　mg/L　and　0　7　-　4　μg/L　for　NSM-MEEKC　and　REPSM-MEEKC,　respectively.　The　proposed　REPSM-MEEKC　has　been　successfully　applied　to　determine　PAEs　in　plastic-packaging　bags,　and　the　spiked　recoveries　were　in　the　range　of　89　1%　-105　6%　with　satisfactory　results.