Development and validation of an improved liquid chromatography–mass spectrometry method for the determination of pemetrexed in human plasma

An improved liquid chromatography–mass spectrometry method for the determination of pemetrexed in human plasma was developed and validated using a simple quadrupole LC–MS and a new SPE cartridge (Plexa® Bond Elut). The analysis was achieved with a C18 analytical column using a mobile phase consisting of formic acid/acetonitrile and isocratic flow for 7 min. The linear ranges (r2 > 0.99) were found from 5 to 5000 ng/mL. The lower limit of detection was 2.5 ng/mL. Within-day and between-day precisions were less than 7.2% and inaccuracy did not exceed 2.8%. This new method is suitable to support pharmacokinetic studies and drug monitoring.