Assay of Nucleic Acids at the Water/Tetrachloromethane Interface with Cetyltrimethylammonium Bromide by Total Internal Reflected Resonance Light Scattering

In this contribution, nucleic acids, including calf thymus DNA (ctDNA), fish sperm DNA (fsDNA), and yeast RNA (yRNA), have been determined with good selectivity and sensitivity at the water/tetrachloromethane (H2O/CCl4) interface by a total internal reflected resonance light scattering (TIR-RLS) technique. Under optimal conditions, amphiphilic complexes produced by nucleic acids and cetyltrimethylammonium bromide (CTMAB) are absorbed at the H2O/CCl4 interface, resulting in a good separation of nucleic acids from the coexisting foreign substances in the aqueous phase and enrichment of nucleic acids at the interface. All of these induce significantly enhanced TIR-RLS signals with the maximum peak located at 370.0 nm at the interface. It was found that the enhanced TIR-RLS intensity is in good proportion to the concentration of nucleic acids in the range of 0.06-2.5, 0.015-3.5, and 0.046-3.5 (mu)g mL^-1 for ctDND, fsDNA, and yRNA, respectively, and their limits of detection (3(sigma)) are 6.0 ng mL^-1, 1.5 ng mL^-1 and 4.6 ng mL^-1 correspondingly. Artificial samples with complicated and highly interfering backgrounds were analyzed satisfactorily.