A high-performance liquid chromatography electrospray ionization

mass spectrometry method is developed and validated for the simultaneous quantitation of three major phenolic acids including 1,5-dicaffeoylquinic acid (1,5-DCQA), 3,4-dicaffeoylquinic acid (3,4DCQA), and 3,5-dicaffeoylquinic acid (3,5-DCQA) in rat plasma. All analytes and internal standard (bergeninum) are extracted from plasma samples by liquid–liquid extraction with isopropanol. The chromatographic separation is accomplished on a stainless-steel column with a gradient 0.1% formic acid–acetonitrile solution as mobile phase at a flow rate of 0.2 mL/min with an operating temperature of 40°C. The selected ion monitoring is performed at m/z 515.2 for 1,5-DCQA, 3,4-DCQA, and 3,5-DCQA, and m/z 327 for the internal standard bergeninum. Linear detection responses are obtained at a concentration range from 0.020 to 5.0 μg/mL for 1,5DCQA, and 0.039 to 10.0 μg/mL for 3,4-DCQA and 3,5-DCQA. The lower limits of quantitation for 1,5-DCQA, 3,4-DCQA, and 3,5DCQA are 20, 39, and 39 ng/mL, respectively. The intraand interday precisions (RSD%) are within 11.0%, and the deviations of the assay accuracies are within ± 12.0% for all analytes. The recoveries are greater than 84.0%. All analytes are proved to be stable during the sample preparation and analytic procedures. The method is successfully applied to the pharmacokinetic study of 1,5-DCQA, 3,4DCQA, and 3,5-DCQA following an intravenous dose of 10 mL/kg mailuoning injection to rats.