Flow injection analysis with diamond thin-film detectors

The viability of using polycrystalline, boron-doped diamond thin-film electrodes for the amperometric detection of ferrocyanide, ferricyanide, ethylamine, and ethylenediamine has been investigated for the first time. These redox reactions were studied by,cyclic voltammetry, hydrodynamic voltammetry, and now injection analysis with electrochemical detection (FIA-EC) at films without any prior surface pretreatment. The diamond films, 1-5 mu m thick, were grown on conducting Si substrates ata dopant level of similar to 10(19) boron atoms/cm(3). The detector performance was evaluated as a function of the linear dynamic range, sensitivity, limit of detection, response variability, and response stability. The results indicate that diamond films produce analytically useful responses for all these analytes in both the scanning and constant; potential modes, Noteworthy are the observations that boron-doped diamond (i) can be used as a substrate for the detection of both oxidation and reduction reactions (e.g., ferro-and ferricyanide) and (ii) can support the oxidation of-ethylamine and ethylenediamine, mechanisms that involve the anodic transfer of oxygen from H2O. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy film characterization data are discussed along with the electrochemical results.