[Determination of deoxyribonucleic acids at nanograms levels with toluidine blue by a resonance light-scattering method].

Resonance light scattering (RLS) spectra of toluidine blue (TB) with DNA was studied. The RLS of TB was greatly enhanced by DNA in the range of pH 10-11. A RLS peak at 350 nm was found, and the enhanced intensity of RLS at this wavelength was proportional to the concentration of DNA. The linear range of the calibration curve was 0-900 ng x mL(-1) with the detection limit of 6.75 ng x mL(-1) for the ctDNA, and for fsDNA the linear range was 0-900 ng x mL(-1) with the detection limit of 2.99 ng x mL(-1). Precision at 500 ng x mL(-1) for the two nucleic acids was 3.7% and 5.6%, respectively. Four synthetic samples were determined satisfactorily.