Development of ion-selective electrodes for antipyrine and its derivatives as potential tool for environmental water monitoring

Abstract

In this work, a set of ion-selective electrodes for the detection of antipyrine and some of its structurally closely related derivatives is developed. These novel potentiometric sensors rely on metallocarborane, cobalt bis(dicarbollide) anion ([3,3′-Co(1,2-C2B9H11)2]−) complexes with the protonated antipyrine derivative as active recognition element. All complexes were characterized, embedded in a PVC membrane, and coated on top of commercial and self-fabricated electrodes. All systems were in-depth evaluated and optimized with focus on their analytical performance, leading to a set of electrodes for antipyrine, 4-aminoantipyrine and 4-(acetamido)antipyrine, which showed a near Nernstian slope (55–57 mV/dec) in the range of 10−5 to 10−2 mol/L and a limit of detection in the μM range. To lower the detection limit and to enable environmental stream water pollution monitoring, we implemented a solid-phase extraction step which could be used to achieve a pre-concentration of a factor >300 (recovery rates: 81–84%) and to lower the detection limit from the μM to the nM range. The combination of our new and highly selective electrodes with this SPE step enables the possibility to monitor antipyrine derivatives simultaneously in either an environmental surrounding or in pharmaceutical formulations. The combination of metallocarborane based ISEs with an SPE pre-concentration step and the in-depth evaluation of the closely related derivatives finally provides a set of valuable tools as well as new insights into their selectivity and real-life applicability.