This paper describes the synthesis and application of a novel ferrocene (Fc) label that can be efficiently attached to oligonucleotides. We demonstrate how pulse electrochemical methods can be used to measure very low concentrations of ferrocene label and, importantly, show good electroanalytical discrimination between a labelled oligonucleotide and an enzyme digested labelled oligonucleotide, in which the ferrocene label nucleotide conjugate has been released. Real time in situ analysis gives a much greater understanding of the process. Potential applications include the detection of specific nucleic acid sequences and measurement of nuclease activity.