Simultaneous determination of lopinavir, saquinavir and ritonavirin in human plasma using liquid chromatography – ion trap mass spectrometry

Background: Lopinavir, saquinavir, and ritonavir are viral protease inhibitors (PIs) developed for and widely used in the therapy of human immunodeficiency virus (HIV)-related disease. These compounds are also active in vitro against the pathogens causing tuberculosis, malaria and coronavirus infections. PIs have been regarded as a platform for the design of inhibitors targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-encoded proteases. This study aimed to develop a liquid chromatography/mass spectrometry (LC/MS) procedure for accurate simultaneous determination of concentrations of these three PIs in the plasma. Methods: Samples of human plasma were protein precipitated with 0.3 M zinc sulfate in a water/methanol solution (30:70, v/v). The extracts were analyzed with reversed-phase chromatography coupled with the electrospray ionization (ESI) source of the ion trap mass detector operating in mEass spectrometry (MS) and tandem mass spectrometry (MS/MS) modes. Results: Calibration curves demonstrated good linearity from 0.01 to 10 µg/mL and acceptable reproducibilities and recoveries. Conclusions: The described procedure proves that a very basic ion-trap LC/MS system could be applied for selective, rapid, and precise determination of antiviral protease inhibitors.