N-in-one determination of retention factors for drugs by immobilized artificial membrane chromatography coupled to atmospheric pressure chemical ionization mass spectrometry.

Immobilized artificial membrane (IAM) chromatography is widely used in drug discovery for ranking the absorption properties of drug candidates. In this work an IAM chromatography method using atmospheric pressure chemical ionization mass spectrometric detection (IAM/APCI-MS) was developed for the determination of log k(IAM) values for a mixture of compounds (9-in-one). Values were calculated from isocratic runs (0, 10, 20, 30, 35% acetonitrile) in both positive and negative modes. Good correlation (r(2) = 0.97) was achieved for n-in-one results obtained with ammonium acetate buffer and mass spectrometry, compared with the traditional method involving single compound analysis with phosphate buffered saline and an ultraviolet detector. A gradient elution method providing fast determination of relative log k(IAM) values in a single IAM/APCI-MS run was demonstrated for the same compounds.