Phenothalein deoxyribonucleic acid(DNA) cetyltrimethyl ammonium bromide(CTMAB) system has been studied by resonance light scattering(RLS). In Tris HCl buffer solution(pH=9 30), phenothalein and DNA react with CTMAB to form large particles of ion association complex, which results in significant enhancement of RLS intensity. The spectral characteristics of RLS, the effective factors and optimum conditions of the reaction have been investigated. Under optimum conditions, the enhanced RLS intensity was proportional to the concentration of DNA in the range of 0 04 to 0 8 mg/L for fish sperm DNA( fsDNA ) and 0 03 to 2 5 mg/L for calf thymus DNA(ctDNA). The detection limits were 12 0 μg/L and 17 0 μg/L for fsDNA and ctDNA, respectively.
