ELECTROCHEMILUMINESCENCE OXALIC-ACID SENSOR HAVING A PLATINUM-ELECTRODE COATED WITH CHITOSAN MODIFIED WITH A RUTHENIUM(II) COMPLEX

An electrochemiluminescence (ECL) sensor having a Pt electrode coated with a tris(2,2'-bipyridine)ruthenium (II)(Ru(II) complex)-modified ch itosan responded to oxalic acid more strongly than to several other su bstrates. The ECL response intensity to oxalic acid was reproducible w ithin 5% (RSD) on 10 repeated runs. A calibration curve for oxalic aci d gave a straight line in the concentration range of 0.1 to 10 mM (cor relation coefficient, 0.997) and the detection limit (S/N = 3) was est imated to be 3 x 10(-5) M. Interestingly, the response to trimethylami ne was 39 times as weak as that obtained with a bare Pt electrode in a n aqueous solution where the Ru(II) complex coexisted. The appearance of the high selectivity can be explained partly on the basis of the el ectrostatic repulsion of the chitosan membrane having a positive charg e with trimethylamine, as being supported by cyclic voltammetry. (C) 1 998 Elsevier Science Ltd. All rights reserved.