Applicability of a Sol–Gel Derived CeO2–TiO2 Thin Film Electrode as an Amperometric Sensor in Flow Injection

Abstract

A sol–gel derived CeO ₂ –TiO ₂ (CTO) thin film, deposited on a glass substrate with an electrically conductive layer of indium tin oxide (ITO), was investigated with regard to its potential use for amperometric detection in flow injection (FI), using a thin layer cell set-up. Cyclic voltammetry was employed for basic studies on the electrochemical behaviour of the CTO film in aqueous LiOH solutions under batch and continuous flow conditions. The dependence of the amperometric response of the CTO film on experimental parameters under FI conditions, such as flow rate of the carrier, operating potential and injection volume, was investigated with LiOH and LiCl. The amperometric signal was linearly dependent on the Li ⁺ concentration over the range 4.0 × 10 ^{- 4} –4.0 × 10 ^{- 3} mol l ^{- 1} . For a concentration of 10 ^{- 3} mol l ^{- 1} Li ⁺ , the RSD of eight consecutive measurements was 5.7% and was comparable to that of conductivity detection (4.7%). Comparison of amperometric with conductometric detection of Li ⁺ , Na ⁺ , K ⁺ , NH ₄ ⁺ and tetraethylammonium ions, in the presence of different counter ions, indicated that the results of both detection modes correlate well.