Electrochemiluminescent labels for applications in fully aqueous solutionsat oxide-covered aluminium electrodes

Oxide-covered aluminium electrodes as well as other tunnel emission electro des allow various label molecules having very different redox and optical p roperties to be excited cathodically. Low detection limits are obtained and the linear calibration concentration range of the labels spans 5 or 6 orde rs of magnitude. The lowest detection limits are obtained with Tb(III) chel ates which can be detected down to picomolar levels in aqueous solution usi ng time-resolved measurement techniques. Luminophores, such as, 9-fluorenyl methyl chloroformate, derivatives of fluorescein and its analogues, aromati c lanthanide(III) chelates, various coumarins and porphyrins can be used as labels emitting in different spectral regions. The extraordinary analytica l power of the tunnel emission electrodes lies in the possibility of simult aneously exciting several different labels emitting either in the UV, visib le or MR range and luminescence lifetimes varying from the ns to the ms ran ge. Therefore, wavelength or time discrimination or their combination can b e exploited in separation of the electrochemiluminescence signals from diff erent labels. (C) 1999 Elsevier Science B.V. All rights reserved.