Determination of four water-soluble compounds in Salvia miltiorrhiza Bunge by high-performance liquid chromatography with a coulometric electrode array system

A method has been developed to determine the four water-soluble components—Danshensu (I), protocatechuic acid (II), protocatechuic aldehyde (III) and salvianolic acid B (IV) in Chinese medicine plant Salvia miltiorrhiza Bunge using high-performance liquid chromatography with a coulometric electrode array detection (HPLC–CEAD) system. Heat reflux extraction was used to pretreat the sample. This analysis was carried on a column of Hypersil C18 (250 mm × 4.6 mm, 5 μm) with a mobile phase of sodium acetate (pH 2.5, 50 mM) and acetonitrile in gradient mode. An ESA electrochemical detector monitored the four compounds. Potentials of four electrodes in series were set at 100, 150, 200 and 250 mV, respectively. Optimization of the pH of mobile phase and the proportion of acetonitrile were also performed. Calibration curve showed good linearity with correlation coefficients (r) more than 0.9937. Average recoveries of the four compounds were more than 92% and relative standard deviations were less than 6.6%. This method appeared to be stable, sensitive and reproducible for determination of the four water-soluble compounds in Chinese medicine plant S. miltiorrhiza Bunge.