The autoderivatization of cyclophosphamide and its metabolite 4-keto cyclophosphamide during capillary gas chromatography

The selectivity of a capillary gas chromatographic assay for the antineoplastic and immunosuppressive agent cyclophosphamide (CPA) towards one of its naturally occurring metabolites, i.e. 4-keto cyclophosphamide (4-keto CPA), has been studied. Mass spectrometry studies revealed that a cyclization product of 4-keto CPA can be formed during the same chromatographic conditions under which CPA has been determined. However, the produced amount is relatively small (less than 10%) in comparison with the percentage produced from CPA. Furthermore, both cyclization products, formed by a loss of HCI and intra alkylation of the parent compounds, can be well separated under proper chromatographic conditions