Simple and multi-configurational flow-cell detector for UV–vis spectroelectrochemical measurements in commercial instruments

An original, simple and sensitive flow-detector for quantitative determination by electrochemical, UV–vis absorption or spectro-electrochemical techniques has been developed. It allows variable configurations for use in a number of analytical situations besides the possibility to use different types of electrodes and materials. The dimensions and format of the detector are suitable for fitting in a standard cell holder for macro cuvettes in commercial UV–vis spectrometers. The sensor has been verified as an optical detector measuring absorbance at 420 nm, due to ferricyanide, with a linear relationship for molar concentrations of between 10−5 and 10−3, with dispersions in the measurements of less than 1%. As an electrochemical detector, two different working electrodes, one made with a stainless steel (SS) pipe and another based on an indium tin oxide (ITO) layer, have been tested by measuring the current due to the oxidation of ferrocyanide while a constant potential is applied. The best results were obtained using the ITO layer because the SS electrode produces distorted chromatographic signals. Lastly, it was tested as a spectro-electrochemical sensor for both electrodes following absorbance at 420 nm of the ferricyanide electro-generated in the detector from the oxidation of injected ferrocyanide. Here, the best results were obtained using the SS electrode with a linear behaviour ranging from 1.2 × 10−4 M to 5 × 10−3 M and dispersions of 5.4% in terms of % RSD.