DETERMINATION OF ARTESUNATE AND DIHYDROQINGHAOSU IN HUMAN PLASMA BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY WITH REDUCTIVE MODE ELECTROCHEMICAL DETECTION

A reductive HPLC-EC method using Model 310 polarographic detector (EG&G PARC) for the determination of artesunate and its active derivative dihydroqinghaosu in human plasma has been established. The whole HPLC system is shown in fig 1 and stainless steel tubing was used throughout from mobile phase to electrolytic cell. The procedure is as follows: transfer 0.20 to 1.0 ml of plasma into a 14 ml glass centrifuge tube, add one drop of glacial acetic acid and 10 ml of ethyl ether-dichloromethane (5: 4, V/V), shake for 10 minutes and centrifuge for 5 minutes at 3000 r/min. Transfer the organic phase into another centrifuge tube as completely as possible and evaporate to dryness under N₂ stream at about 35℃. Keep the tube containing the residue in a refrigerator and reconstitute the residue with about 50 μ1 methanol before assay, Load the reconstituted solution into the injection loop followed with about 30 μI of water to wash the tube and then inject the two solutions in the loop into the chromatograph using the following conditions: column, 15×0.46 cm packed with ODS (YWG-C₁₈H₃₇, made in China); mobile phase, MeOH—0.03M(NH₄)₂SO₄—glacial HAc=55: 45: 0.1 (V/V) which must be deaerated by purging pure N₂ gas under reflux all the time; flow rate, 3.0 ml/min. The Model 310 detector was controlled by Model 174 polarographic analyzer (EG&G PARC) operated in sampled DC mode with a fixed potential of -0.24 V(vs Ag/AgCl); operate mode, static mercury drop electrode; drop time, 2 second; drop size, middle.This method is selective, sensitive and has a good linearity. The absolute recoveries of artesunate and dihydroqinghaosu were found to be above 90% in general with CV values of less than 9%. This method is suitable for the study of pharmacokinetics of these two antimalarial drugs.