A novel, rapid, and simple capillary electrophoresis (CE) method has been developed for the determination of antimalarial artemisinin by on-line treatment with alkaline. By on-line reaction, artemisinin was automatically and reproducibly converted to the strongly UV-absorbing compound, Q292, by treating it with 0.20 mol/L NaOH solution for 3 min at 40degreesC. Analysis was carried out in less than 12 min after conversion of artemisinin in a flow injection (FI) system that was coupled to CE equipment via a split-flow interface cell, and a sampling frequency of 8 h(-1) is achievable. The on-line conversion method has been applied to the determination of artemisin n in the traditional Chinese herbal drug Artemisia annua L., and the results are satisfactory.