Mono- and diiodocyclophosphamide as possible internal standards for cyclophosphamide quantification: characterization by ion trap multi-stage mass spectrometry and effects of iodine-chlorine substitution on the fragmentation pattern

Hospital personnel involved in antineoplastic drug preparation and administration to patients are exposed to large amounts of these drugs. Labour legislation indicates the necessity of planning monitoring strategies aimed at prevention and/or reduction of drug exposure. Monitoring strategies consist in quantitative determinations of indicators, present in environmental and biological matrices. Among the antineoplastic drugs widely used, cyclophosphamide (CP) has been identified as a suitable indicator of potential exposure to mixtures of antineoplastic drugs. Many literature methods literature for quantitative analysis of CP involve either liquid or gas chromatography with mass spectrometry, both of which require use of a suitable internal standard. The present work focuses on the synthesis of mono- and di-iodocyclophosphamide (CPI and CPI2) to be used as internal standard. These compounds were analyzed by GC/EI-MS/MS and LC/ESI-MSn using ion trap mass spectrometry. The product ion mass spectra are interpreted in terms of proposed structures of fragment ions. Iodine-chlorine substitution resulted in a weakening of the carbon-halogen bond with a noteworthy influence on the ion fragmentation processes. The propopsed suitability of CPI and CPI2 as internal standards was based on similarities to CP as regards ionization and fragmentation processes. The results obtained suggest that CPI could be used as internal standard for CP quantification by LC/ESI-MS/MS, and CPI2 for GC/EI-MS/MS analyses.