This paper describes a novel method in which solvent microextraction（SME） is followed by on-line back-extraction-field amplified sample injection（OLBE-FASI） in capillary zone electrophoresis（CZE）.The water-immiscible solution sample, sealed with water plug in the sample vial,was used for direct electroinjection. The water plug with moderate content of organic solvent,low-conductivity,and the presence of a small（amount） of H+ provided the highest sensitivity for analyzing positively chargeable compounds,such as cocaine and thebaine.The linear range was 0.040—4,0.040—2 μg/mL,with the square of the correlation coefficient(r2)>0.997,respectively.Detection limits were in the range of 5—10 ng/mL.
