Mass spectrometry of chlorambucil, its degradation products, and its metabolite in biological samples.

A sensitive and specific method for the determination of chlorambucil and its metabolite in biological fluids is reported. The method is based on selected-ion monitoring detection following simple extraction of the parent compound, its metabolite, and an internal standard (chlorambucil-d8) from plasma and urine samples. The precision (reproducibility) of the method was 94.3 +/- 1.3% with 200 ng of chlorambucil added to 1 ml of plasma. Chlorambucil degradation or alkylation of plasma proteins was minimal with plasma incubated at 24 degrees for 4 hr. However, chlorambucil recovery decreased to 56% after plasma incubation at 37 degrees for 4 hr. Three chlorambucil degradation products in ethyl acetate solution were found, and their structures were studied by mass spectrometry.