Fluorescence determination of microconcentrations of chlorambucil after photoactivation

A fluorescence assay is described which measures the alkylating activity of chlorambucil or its isocyanate derivative after photoactivation in the presence of dimethyl sulfoxide. This assay has a lower limit of sensitivity of 100 ng/mL and RSD of less than 10% for chlorambucil. The method requires less than 5 micrograms of alkylating agent and the fluorophore produced is stable for at least 24 h.