Highly sensitive determination of doxorubicin and daunorubicin based on their effect on the resonance light scattering signals of the ethidium-DNA complex

We have developed a resonance light scattering (RLS) quenching assay for the highly sensitive determination of doxorubicin (DOX) and daunorubicin (DAU). It is based on the reduction of the intensity of the shoulder of the RLS spectra at 443 nm. The intensity of the RLS of the ethidium-DNA system decrease linearly on addition of trace quantities of DOX or DAU within the concentration range of 0.008 to 12.0 mu g mL(-1) for DOX, and of 0.010 to 21.0 mu g mL(-1) for DAU. The detection limits are 3.0 and 5.0 ng mL(-1), respectively. The assay was successfully applied to the determination of DAU in synthetic and serum samples. Compared to the reported methods for anthracyclines, this assay displays higher sensitivity, lower detection limits, and a wider linear range.