Abstract: A ligand in a sample can be assayed using electrochemical apparatus containing a working electrode and components comprising:(a) the sample,(b) a specific binding partner to the ligand, or a specific binding partner to the ligand and selected from ligand analogues and specific binding partners, and(c) an electron-source or electron-acceptor; at least one of components (b) being labelled with an electron-transfer mediator capable of aiding the transfer of electrons between the electron-source or electron-acceptor and the working electrode by accepting electrons from the electron-source and donating them to the working electrode, or accepting the electrons from the electrode and donating them to the electron-acceptor.

Abstract: In its broadest aspect, the present invention provides a method of assaying a ligand in a sample which comprises contacting the sample with a predetermined quantity of a specific binding partner to the ligand, said specific binding partner being immobilized on the effective gate electrode of a field effect transistor, and determining whether (and, if desired, the extent to which) an appropriate transistor characteristic is changed as a result of complex formation between the ligand and the specific binding partner.

Abstract: A cap for a container in which immunoassays are performed includes a liquid absorbing material accessible to liquid in the container.