Spectrofluorimetric determination of 2-chloro-2'-deoxyadenosine (cladribine) in human plasma by photochemical reaction and chloroacetaldehyde derivatization.

A quantitative fluorescence assay for 2-chloro-2'-deoxyadenosine (cladribine, leustatin, 2-CdA) in human plasma is described. The drug was isolated from plasma by ethyl acetate extraction and derivatized by a two-step procedure in which 2'-deoxyisoguanosine (2'-diG) was first prepared by UV irradiation of 2-CdA and was then treated with chloroacetaldehyde to form the fluorescent derivative, 1,N6-etheno-2'-deoxyisoguanosine. Fluorescence intensity of the solutions was measured using an excitation wavelength of 275 nm and emission of 397 nm. The analytical measuring range of the method extends from about 1 microgram/l to at least 100 micrograms/l.