Sensitive HPLC–APCI–MS method for the determination of cyclovirobuxine D in human plasma

A sensitive high performance liquid chromatography–atmospheric pressure chemical ionisation–mass spectrometry (HPLC–APCI–MS) assay for determination of cyclovirobuxine D (CVB-D) in human plasma using mirtazapine as internal standard (I.S.) was established. After adjustment to a basic pH with sodium hydroxide, plasma was extracted by ethyl acetate and separated by high performance liquid chromatography (HPLC) on a reversed-phase C18 column with a mobile phase of 30 mM ammonium acetate buffer solution containing 1% formic acid–methanol (48:52, v/v). CVB-D was determined with atmospheric pressure chemical ionisation–mass spectrometry (APCI–MS). HPLC–APCI–MS was performed in the selected-ion monitoring (SIM) mode using target ions at [M + H]+ m/z 403.4 for CVB-D and [M + H]+ m/z 266.2 for I.S. Calibration curves were linear over the range 10.11–4044 pg/ml. The lower limit of quantification was 10.11 pg/ml. The intra- and inter-run variability values were less than 9.5 and 12.4%, respectively. The mean plasma extraction recovery of CVB-D was in the range of 85.3–92.8%. The method was successfully applied to determine the plasma concentrations of CVB-D in Chinese volunteers.