Generation of gold nanostructures at the surface of platinum electrode by electrodeposition for ECL detection for CE

In this paper, we report a sensitive method for ECL detection for CE based on generation of gold nanostructures at the surface of Pt electrode by electrodeposition. Difenidol hydrochloride was used as a model analyte. With the increase of electrodeposition amount, the morphology of gold nanostructures changed from discrete nanoflowers to dense nanoparticle array. Interestingly, the variation of deposition amount also greatly affected the ECL intensity of difenidol. The ECL intensity increased remarkably with deposition amount and reached the maximum value at the deposition amount of 7.0×10−8C; further increasing the deposition amount, however, caused the ECL intensity to decrease. Other conditions, including applied potential, injection time and voltage, buffer pH, were also optimized in detail. Under the optimized conditions, the linear response range of difenidol is from 1.0×10−8 to 5.0×10−5 M, and the detection limit was 4.0×10−9 M (S/N=3). The RSDs of ECL intensity and migration time were 2.0 and 1.6%, respectively (n=5, at 7.5 μM difenidol). Compared with using bare electrode, the detection sensitivity was significantly improved by ca. two orders of magnitude. Notably, the nanogold was prepared at the surface of electrode and no nanogold was added to the electrophoretic buffer or detection cell, thus causing no interference to the separation. Finally, the proposed method was successfully applied to the analysis of difenidol in tablets and urine samples. With high sensitivity and good reproducibility, this method provides a promising platform for the determination of pharmaceuticals that have a tertiary amine group such as difenidol.