Selective electrodes for [PF6]- and [BF4]- anions based on the associates formed by ionic liquid and cationic dyes

The feasibility of the newly synthesized ionic associates L1 and L2 formed by ionic liquid [C(4)mim][PF6] and cationic dyes (malachite green and methylene blue) has been tested as a novel ionophore for the preparation of anion-selective polymeric membrane electrodes. The electrode exhibits Nernstian response and enhanced potentiometric selectivity towards [PF6](-) compared to many other anions. The influence of some experimental parameters such as membrane composition, nature of plasticizer and amount of additive on the potential response of the [PF6](-) sensor are investigated. Under the optimized conditions, the response slopes of the membrane electrodes towards [PF6](-) are 59.7 +/- 0.5 and 58.1 +/- 0.5 mV/decade based on ionophore L1 and L2, respectively, in 1.0 x 10(-5)-1.0 x 10(-1) or 1.0 x 10(-6)-1.0 x 10(-1) mol/L concentration range. Interestingly, the optimized electrodes based on ionophores L1 and 12 also exhibit Nernstian response characteristics (60.3 +/- 0.5 and 56.0 +/- 0.5 mV/decade) for tetrafluoroborate anion [BF4](-) in a wide concentration range. Thus, the proposed sensor has been used for the determination of [PF6](-) and [BF4](-) in aqueous ionic liquids samples and the solubility of the [PF6](-) and [BF4](-) based ionic liquids in water. The satisfactory results are obtained. (c) 2012 Elsevier B.V. All rights reserved.