A new, high-throughput high- Performance liquid chromatographic/mass spectrometric assay for therapeutic level monitoring of digoxin in human plasma

Abstract

A new, high-throughput HPLC/MS assay for the quantification of digoxin in human plasma was developed and validated. The separation was performed on a Zorbax SB-C18 column under isocratic conditions using a 55 + 45 (v/v) mixture of methanol and 0.1% (v/v) formic acid in 10 μM sodium acetate as the mobile phase at 45°C with a flow rate of 1 mL/min. The detection of digoxin was performed in the selected ion monitoring mode (mlz 803.5). The human plasma samples (0.2 mL) were deproteinized with 7% perchloric acid in water, and aliquots of 20 μL from supernatants obtained after centrifugation were directly injected into the chromatographic system. The method showed good linearity (r > 0.9926), precision (CV > 18.9%), and accuracy (bias > 5.6%) over the range of 0.5-50 ng/mL plasma. The lower LOQ was 0.5 ng/mL, and the recovery was between 92 and 106%. The method is not expensive, it needs a minimum time for plasma sample preparation, and it has a run time of 2.3 min for instrument analysis (the retention time of digoxin was 1.9 min). The developed and validated high-throughput method is very simple, rapid, and efficient, with wide applications in clinical level monitoring, pharmacokinetics, and bioequivalence studies.