Highly sensitive high-performance liquid chromatography/selective reaction monitoring mass spectrometry method for the determination of cyclophosphamide and ifosfamide in urine of health care workers exposed to antineoplastic agents

In recent years, the potential for exposure of health care workers to antineoplastic agents has led to the establishment of more restrictive government and professional standards and procedures for handling cytotoxic drugs. Therefore, the detection of low exposure levels is a new and important aim of biological monitoring. In the present paper we report an assay for the simultaneous determination of cyclophosphamide (CP) and ifosfamide (IF) in urine, using electrospray ionization liquid chromatography/tandem mass spectrometry with selective reaction monitoring (HPLC/SRM-MS). A rapid sample preparation procedure uses a solid-phase extraction stage with C18 columns. The urine assay is linear over the range 0.02 to 0.4 microg/L, with lower limits of quantification (LLOQs) of 0.02 and 0.04 microg/L for CP and IF. The accuracy and precision have been carried out through the validation study. The intra-day precision, expressed as relative standard deviation (RSD), is found to be always less than 14.7% for both analytes. The overall precision, assessed on three different days, is less than 15.0%. The recovery of ozaxaphosphorines ranges from 83.5% (CP) to 88.5% (IF) with a RSD always less than 14.6%. The uncertainty of the overall method was also evaluated, to identify possible sources of error. The combined uncertainty was less than 25% over all the days of the validation study. This method is selective and sensitive enough to determine trace levels of CP and IF in a range of urine concentrations relevant to performing low exposure assessment.