Voltammetric and amperometric determination of selected dinitronaphthalenes using single crystal silver amalgam based sensors

Abstract

Modern voltammetric techniques, combined with the quasi-cylindrical single crystal silver amalgam electrode (CAgAE) tested, were used for determination of selected environmental pollutants, 1,3-dinitronaphthalene, 1,5-dinitronaphthalene and 1,8-dinitronaphthalene. The optimum conditions were found for the determination of selected dinitronaphthalenes (DNNs) using direct current voltammetry and differential pulse voltammetry. The procedures were applied to determination of these analytes in model samples of tap water. The 1,3-, 1,5- and 1,8-DNN were determined by differential pulse voltammetry (DPV) with limits of quantification 1.0, 1.0 and 0.3μmoll−1 in concentration range up to 100μmoll−1 in Britton–Robinson buffer and methanol mixture (1:1) with final pH 8.2, 12.3 and 8.2, respectively. The 1,3-, 1,5- and 1,8-DNN were then determined by DPV with limits of quantification 0.4, 0.5 and 0.4μmoll−1 in model samples of tap water conditioned by Britton–Robinson buffer (9:1) pH 7.0, 12.0 and 7.0, respectively, in presence of 0.001moll−1 Na2EDTA. Adsorptive stripping differential pulse voltammetry was unsuccessfully tested in an attempt to obtain lower limits of quantification. The processes occurring during the DNNs reduction at the CAgAE were also investigated by cyclic voltammetry. A single crystal of the silver amalgam was then used to design a cylindrical flow-through detector which was utilized for amperometric detection of selected DNNs in a mixture, after their separation by conventional HPLC. The optimum separation and detection conditions for the DNNs at the cylindrical flow-through detector were found. The DNNs were separated using column with reverse phase C-18, ammonium acetate pH 4.7–methanol (27:73) as mobile phase at flow rate 1.5mlmin−1 and detected by the cylindrical detector at potential −1.2V with limit of detection 1μmoll−1 within concentration range up to 100μmoll−1. Single-crystal silver amalgam was found to be a suitable alternative for “toxic” mercury in voltammetric measurements and a convenient electrode material for designing a new amperometric detector.