The determination of Ifosfamide in human blood serum using LC/MS

A rapid method has been developed for the determination of the antitumor drug Ifosfamide 3-(2-chloroethyl)-2-(2-chloroethylamino)tetrahydro-2H-1,2,3-oxazaphosphorine-2-oxide in serum based on continuous flow fast atom bombardment (CFFAB) mass spectrometry interfaced to chromatography on a very short reversed-phase HPLC column without use of an internal standard. The detection limits under optimized conditions are in full scan mode 35 ng/mL and with selected ion recording 1.5 ng/mL serum. Since this approach does not allow to detect the most relevant metabolites of the drug, a study has been carried out using electrospray instead of CFFAB MS without changing the chromatographic conditions. Since in electrospray MS no background ions interfere with the analytes, the detection of some of the metabolites becomes feasible. Spectra indicating the possibilities of that combination are given here as well.