Self-assembled iridium(III) complex microspheres on the carbon paste electrode surface for signal enhanced amperometric determination of H2O2 in color cream developers

In this work, a simple strategy of carbon paste electrode (CPE) modification with previously synthesized iridium(III) complex i.e. [Ir(3m-ppy)(2)(dppm)Cl] (3m-ppy = 3-methyl-2-phenylpyridine, dppm = bis (diphenylphosphino)methane) was elaborated together with first application of [Ir(3m-ppy)(2)(dppm)Cl] as working electrode component for H2O2 amperometric determination. The electrode with iridium(III) complex (Ir/CPE) was prepared in one step using optimized drop coating procedure. The characterization of Ir/CPE by scanning electron microscopy in combination with energy dispersive spectrometry confirmed the presence of densely populated Ir(III) complex based microspherical particles self-assembled on the electrode surface. Comparative cyclic voltammetric responses of the Ir/CPE and pristine CPE in phosphate (pH 7.50) and acetate (pH 4.50) buffer solution proved that in both supporting electrolytes in the case of the modified electrode one irreversible oxidation peak is present with maximum close to 1.2 V vs. SCE. Comparative measurements were performed with both electrodes in the presence of H2O2 target analyze, and it was found that after appropriate electrochemical activation at 1.20 V, during 60 min, the Ir complex containing electrode is a promising sensor for analytical purposes offering the possibility for the analysis of H2O2 at working potentials in anodic range from 0.30 to 0.60 V and in cathodic range from -0.05 to -0.30 V in phosphate buffer pH 7.50 (0.1 M) as supporting electrolyte. The optimized amperometric protocol which included stirred solution, electrochemical activation of the electrode and working potential as 0.60 V vs. SCE showed acceptable linearity of the calibration curve for the investigated H2O2 concentration range from 51.5 to 508.2 mu M, and with evaluated LOQ as 8.8 mu M. Additionally, this electrode exhibited good stability and reproducibility with relative standard deviation lower than 3%. The optimized and simple amperometric method was successfully applied for determination of H2O2 content in commercially available color cream developers and obtained results were in a good agreement with declared values by the producers indicating the reliability of prepared H2O2 sensor.

Automated summary

In this study, a carbon paste electrode was modified with a previously synthesized iridium(III) complex and used as a working electrode for H2O2 amperometric determination. The modified electrode showed promising results for the analysis of H2O2, with a wide working potential range and good stability. The optimized amperometric method demonstrated good linearity and was successfully applied for the determination of H2O2 content in commercially available color cream developers.