Simultaneous determination of amodiaquine and its active metabolite in human blood by ion-pair liquid chromatography–tandem mass spectrometry

A sensitive and selective ion-pair liquid chromatography–tandem mass spectrometric method (IP-LC–MS/MS) for the simultaneous determination of amodiaquine (AQ) and its active metabolite, N-desethylamodiaquine (AQm), in human blood has been developed and validated. Pentafluoropropionic acid (PFPA) was applied as ion-pairing reagent in reversed-phase chromatographic separation. The effects of PFPA concentrations and the volume fraction of acetonitrile in the mobile phase on the retention of analytes were investigated on a Venusil MP-C18 column, and the mobile phase was finally optimized as acetonitrile:water (23:77, v/v) with 0.0667% PFPA in the aqueous phase. The results proved that PFPA as an ion-pairing reagent could provide desirable chromatographic performance in the IP-LC–MS/MS determination of 4-aminoquinoline compounds. Blood samples were protein precipitated with acetonitrile using hydroxychloroquine (OHCQ) as the internal standard. The detection was carried out in multiple reaction monitoring (MRM) mode via positive atmospheric pressure chemical ionization (APCI) interface. The lower limits of quantification were established at 0.150 and 1.50 ng/mL for AQ and AQm, respectively. The validated IP-LC–MS/MS method was applied to a clinical pharmacokinetic study of AQ and AQm in human blood after an oral administration of 600 mg AQ hydrochloride (459 mg base).