Resonance double frequency light scattering of the morin–nucleic acid–cetyltrimethylammonium bromide system and its analytical application Original Research Article

Resonance double frequency light scattering (RDFLS) of the morin–nucleic acid–cetyltrimethylammonium bromide system and its analytical application have been studied. In hexamethylene tetramine (HMTA) buffer (pH 7.30), morin and nucleic acid react with CTMAB to form large particles of ion-association complex, which result in significant enhancement of RDFLS intensity. The spectral characteristics of RDFLS, the effective factors and optimum conditions of the reaction have been investigated. After the addition of morin to the CTMAB–DNA system, the Zeta potential (ζ) of DNA increases, which is due to the formation of a new ion-association complex. Mechanistic studies showed that the enhanced RDFLS comes from the aggregation of morin on nucleic acid in CTMAB micelles. Under the optimum conditions, the enhanced RDFLS intensity is proportional to the concentration of nucleic acid in the range 2.5×10−8 to 5.0×10−6 g ml−1 for calf thymus DNA (ctDNA), 2.5×10−8 to 5.0×10−6 g ml−1 for salmon sperm DNA (ssDNA) and 2.5×10−8 to 2.0×10−6 g ml−1 for yeast RNA (yRNA). The detection limits (S/N=3) are 16.7, 27.0 and 23.4 ng ml−1 for ctDNA, ssDNA and yRNA, respectively. Synthetic samples were analysed satisfactorily.