Adsorptive transfer stripping voltammetry: determination of nanogram quantities of DNA immobilized at the electrode surface.

In adsorptive transfer stripping voltammetry (AdTSV), DNA is first adsorbed at the electrode, the electrode is washed and transferred (with the adsorbed layer) in the medium not containing DNA, and voltammetric analysis is performed in this medium. Adsorption can be performed from a drop of DNA solution, which makes it possible to reduce the volume of the analyzed sample by two orders of magnitude as compared to that of conventional voltammetry. With the hanging mercury drop electrode the limit of detection of single-stranded DNA is below 0.1 micrograms/ml; thus if the adsorption is performed from a 10-microliter drop of DNA solution subnanogram quantities of single-stranded DNA are sufficient for the analysis. In AdTSV the behavior of single- and double-stranded DNAs markedly differ from each other in a manner similar to that in the conventional voltammetric or polarographic analysis; AdTSV can thus be used in DNA structure analysis. In AdTSV the DNA transport and its adsorption at the electrode are separated from the electrode process; due to this fact it is possible (a) to perform the voltammetric analysis of DNA from media not suitable for voltammetric analysis of the conventional type, (b) to study the interaction of immobilized DNA with other substances in solution without the results of the voltammetric analysis being influenced by DNA interactions in the bulk of solution, and (c) to exploit the differences of adsorbability of DNA and other substances in order to separate them on the electrode.