DNA-Modified electrodes. Part 5. Electrochemical behavior of Co2+ at DNA-modified gold electrodes in the presence of 2,2 '-bipyridyl

The electrochemical behavior of Co2+, whose response is abnormally enhanced at DNA-modified gold electrodes in the presence of 2,2'-bipyridyl, was fou nd. After it forms an adduct with Co2+, excess 2,2'-bipyridyl can enhance t he electrochemical response of this adduct at DNA-modified gold electrodes by synergism. ssDNA-modified gold electrodes that are highly sensitive to C o2+ were utilized to determine trace Co2+ in the presence of 2;2'-bipyridyl by cyclic voltammetry. It was found that the peak currents for cobalt incr ease linearly over the concentration range of 1.0x10(-7)-1.1x10(-6) mol/l w ith a detection limit of 4.0x10(-8) mol/l. For seven preconcentration/volta mmetric detection/renewal cyclic experiments with 1.0x10(-7) mol/l and 1.0x 10(-6) mol/l Co2+ solutions, relative standard deviations of 2.7% and 1.9% were found, respectively, indicating that the DNA-modified gold electrodes were stable and repeatable.