Liquid chromatography–electrospray ionisation mass spectrometry method for the determination of escitalopram in human plasma and its application in bioequivalence study

A novel liquid chromatographic–electrospray ionisation mass spectrometric (LC–ESI-MS) method has been developed for the determination of escitalopram, an antidepressant in human plasma using paroxetine as internal standard. The method involved liquid–liquid extraction of the analyte from human plasma with a mixture of diethyl ether and dichloromethane (70:30, v/v). The chromatographic separation was achieved within 7.0 min by using 2.0 mM ammonium acetate (pH 5.0)–acetonitrile (54:46, v/v) as mobile phase and a ODS YMC™ AQ 150 mm × 4.6 mm analytical column; the flow-rate was 1.0 ml/min. Ion signals m/z 325.0 and 330.0 for escitalopram and internal standard, were measured in the positive mode. A detailed validation of the method was performed as per USFDA guidelines and the standard curves were found to be linear in the range of 1.0–200 ng/ml with a mean correlation coefficient more than 0.99. The absolute recovery was more than 75% for both escitalopram and internal standard. The method was simple, sensitive, precise, accurate and was successfully applied to the bioequivalence study of escitalopram in healthy, male, human subjects.