In this study, the detection protocols for the individual, selective, and simultaneous determination of ibuprofen (IBP) and diclofenac (DCF) in aqueous solutions have been developed using HKUST-1 metal-organic framework-carbon nanofiber composite (HKUST-CNF) electrode. The morphological and electrical characterization of modified composite electrode prepared by film casting was studied by scanning electronic microscopy and four-point-probe methods. The electrochemical characterization of the electrode by cyclic voltammetry (CV) was considered the reference basis for the optimization of the operating conditions for chronoamperometry (CA) and multiple-pulsed amperometry (MPA). This electrode exhibited the possibility to selectively detect IBP and DCF by simple switching the detection potential using CA. However, the MPA operated under optimum working conditions of four potential levels selected based on CV shape in relation to the potential value, pulse time, and potential level number, and order allowed the selective/simultaneous detection of IBP and DCF characterized by the enhanced detection performance. For this application, the HKUST-CNF electrode exhibited a good stability and reproducibility of the results was achieved.
This study aimed to develop the detection protocol for the quantitative determination of salicylic acid (SA) in water. A carbon nanotubes-epoxy composite (CNTE) electrode was tested for the development of the SA detection protocol. The electrochemical behaviour of SA on a CNTE electrode has been studied using the cyclic voltammetry (CV) technique. Also, the study of pH effect by CV showed that no significant effect was found. Differential-pulsed voltammetry (DPV) and square-wave voltammetry (SWV) techniques were employed for the optimization of the detection protocol. The optimized SWV technique application assumes the step potential of 0.005 V, the modulation amplitude of 0.05 V and the frequency of 50 Hz. In order to use this detection protocol for the in-field detection application, the possibility of using this composite electrode in real surface water without adding the supporting electrolyte has been tested. The same electroanalytical parameters for SA detection in real surface water and tap water were achieved without any interference, which denotes the microelectrode array behaviour of the composite electrode. This behaviour confers a great potential of this composite electrode for in-field direct detection of salicylic acid and also, for the indirect detection of acetylsalicylic acid from surface water.
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