Regenerable sensor based on tris(4,7'-diphenyl-1,10-phenanthroline)ruthenium (II) for anodic and cathodic...

Tris(4,7'-diphenyl-1,10-phenanthroline) ruthenium (II) dichloride [Ru(dpp)₃²⁺] was used for the first time to construct a regenerable electrochemiluminescence (ECL) sensor. The Ru(dpp)₃²⁺-modified carbon paste electrode (CPE) showed several unique features in comparison with commonly studied Ru(bpy)₃²⁺-modified electrodes. On the one hand, a quite reversible reduction peak was observed at -0.96 V where no obvious hydrogen evolution occured, enabling the sensitive detection of S₂O₈^2-. Moreover, our proposed S₂O₈^2- sensor showed a good linear range from 3 × 10^-9 to 3 × 10^-4 M with a detection limit of 2 nM, indicating higher sensitivity for the same analyte than previously reported ECL methods by about two orders of magnitude. On the other hand, the Ru(dpp)₃²⁺-modified electrode showed an irreversible oxidation peak because electrogenerated Ru(dpp)₃³⁺ is very reactive in aqueous solutions, while Ru(bpy)₃²⁺-modified electrode showed a reversible oxidation peak. Moreover, the present sensor showed a good linear range from 10^-7 M to 10^-3 M for oxalate with a detection limit of 60 nM. It detected oxalate in urine samples with nice recoveries. The regenerable ECL sensor presented good characteristics, such as low cost, simple fabrication procedure and fast response time. The Ru(dpp)₃²⁺ based regenerable sensor is an attractive alternative to Ru(bpy)₃²⁺-based regenerable sensor, as it can be used for both anodic and cathodic ECL analysis with high sensitivity in aqueous media.