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 x 10(-8) to 0.1 mug ml(-1) for herring sperm DNA and 2.0 x 10(-6) to 0.2 mug ml(-1) for calf thymus DNA with 3sigma detection limits of 8.3 x 10(-9) mug ml(-1) for herring sperm DNA and 3.5 x 10(-7) mug ml(-1) for calf thymus DNA, respectively. The relative standard deviation for 1.0 x 10(-4) mug ml(-1) herring sperm DNA was 0.99% and 2.0 x 10(-3) mug 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. (C) 2003 Elsevier B.V. All rights reserved.