Flow-injection chemiluminescence assay for ultra-trace determination of DNA using rhodamine B–Ce(IV)-DNA ternary system in sulfuric acid media

A novel flow-injection chemiluminescence method for the determination of DNA at ultra-trace level has been established. In 0.8 M sulfuric acid media, the chemiluminescence of the rhodamine B–cerium (IV) or Ce(IV) system is enhanced by DNA, activated previously by imidazole–HCl buffer solution (pH 7.0). The enhanced intensity of chemiluminescence is in proportion to log DNA concentration 1.0×10^-8 to 0.1 (mu)g ml^-1 for herring sperm DNA and 2.0×10^-6 to 0.2 (mu)g ml^-1 for calf thymus DNA with 3(sigma) detection limits of 8.3×10^-9 (mu)g ml^-1 for herring sperm DNA and 3.5×10^-7 (mu)g ml^-1 for calf thymus DNA, respectively. The relative standard deviation for 1.0×10^-4 (mu)g ml^-1 herring sperm DNA was 0.99% and 2.0×10^-3 (mu)g ml^-1 for calf thymus DNA was 1.1% (n=11). Using the optimized system, DNA contents in six synthetic samples has been determined with recoveries of 99.5–109.0%. The possible mechanism has also been studied in this paper.