Electrochemiluminescent labels for applications in fully aqueous solutions at oxide-covered aluminium electrodes Original Research Article

Oxide-covered aluminium electrodes as well as other tunnel emission electrodes allow various label molecules having very different redox and optical properties to be excited cathodically. Low detection limits are obtained and the linear calibration concentration range of the labels spans 5 or 6 orders of magnitude. The lowest detection limits are obtained with Tb(III) chelates which can be detected down to picomolar levels in aqueous solution using time-resolved measurement techniques. Luminophores, such as, 9-fluorenylmethyl chloroformate, derivatives of fluorescein and its analogues, aromatic lanthanide(III) chelates, various coumarins and porphyrins can be used as labels emitting in different spectral regions. The extraordinary analytical power of the tunnel emission electrodes lies in the possibility of simultaneously exciting several different labels emitting either in the UV, visible or NIR range and luminescence lifetimes varying from the ns to the ms range. Therefore, wavelength or time discrimination or their combination can be exploited in separation of the electrochemiluminescence signals from different labels.