LC–APCI–MS Simultaneous Determination of Barbital, Amobarbital, Phenobarbital and Secobarbital in Human Plasma

A sensitive and simple liquid chromatography–atmospheric pressure chemical ionization–mass spectrometry (LC–APCI–MS) method was developed and validated for determination of barbital, amobarbital, phenobarbital and secobarbital in human plasma. Barbiturate drugs extracted from plasma samples using ethyl ether and separation were carried out on an Agilent Zorbax SB-C18 column (2.1 mm × 150 mm, 5 μm) at 30 °C, acetonitrile–water used as mobile phase with gradient elution. APCI source was applied and operated in negative ion mode, and selective ion monitoring mode used to quantify barbiturate drugs. The method showed excellent intra-assay and inter-assay precision (relative standard deviation and bias <15%) for quality control samples spiked at concentrations of 10, 400 and 1,600 ng mL−1 and the r2 > 0.99 over the range were investigated (10–2,000 ng mL−1). Lower limits of quantification were estimated to be 10 ng mL−1. This method is simple and sensitive for quantitation of barbiturate drugs in plasma, suitable for use in the clinical and forensic medical laboratory.