A device for the rapid qualitative or quantitative assay of entities having a biological activity

The invention relates to a novel assay for the deter­mination of entities having biological activity and to a device for carrying out such determinations. The assay is a very sensitive one and quantities in the picogram per millimeter range can be determined. The assay is based on chrono-coulometric measurements with sequential measurements of a plurality of samples being carried out with the aid of a multiplexer, in combination with a potentiostat, there being provided suitable electrodes and means for applying a predeter­mined voltage. One of the electrodes is advantageously a glassy carbon electrode, carbon felt or cloth or carbon paper. Amongst biologically active entities there are antibodies/antigens; hormones/receptors ; nuclotides/ nucleotide probes, one of the members of such a pair being immobilized on an electrode surface, being tagged with an enzyme providing a signal in coulo­metric measurements.