Interaction of cetyltrimethylammonium bromide with nucleic acids and determination of nucleic acids at nanogram levels based on the measurement of light scattering Original Research Article

After the addition of cetyltrimethylammonium bromide to DNA, the ζ of DNA increased and changed from −70.2 to +21.6 mV, and the absorbance at 260.0 nm increased. This indicates that DNA is partly denatured and a large new ion association complex formed. The formation of the new associate can result in very strong light scattering at 414.0 nm, which is in proportion to the concentration of nucleic acids in the range 2.5×10−8 to 2.0×10−5 g ml−1 for calf thymus (ct)DNA, 2.5×10−8 to 2.0×10−5 g ml−1 for fish sperm (fs)DNA, and 5.0×10−8 to 5.0×10−5 g ml−1 for yeast (y)RNA. The detection limits (3σ) are 8.3, 2.4, and 23.4 ng ml−1, respectively. Synthetic samples were determined satisfactorily.