The lower detection limit and the selectivity behavior of anion-selective electrodes (ISEs) are improved by using optimized inner solutions and membrane compositions. With a membrane based on the recently described ionophore mercuracarborand-3, a detection limit of 2 x 10(-9) M has been achieved for iodide. Nevertheless, the improvements are less pronounced than in the case of cation ISEs. This is mainly due to the fact that so far no anion ISE is known with the extremely high selectivities of cation ISEs. If the membrane does not contain an ionophore, leaching of the ion exchanger from the membrane into the sample is also a relevant limiting factor except for ion exchangers of very high lipophilicity.
"Ion-selective electrodes (ISEs) are a particular breed of electrochemical sensor, which convert the activity of a given analyte in solution into a voltage potential. ISEs employ polymer gels based mainly on poly(vinylchloride) (PVC) and PMMA [61,62], for the selective detection of important environmental and biological analytes at levels as low as nanomolar concentrations in some cases [63,64]. As PVC and PMMA exhibit high glass transitions, organic plasticizers are used to produce flexible transparent polymer membranes. "
[Show abstract][Hide abstract] ABSTRACT: This overview aims to summarize the existing potential of “Ionogels” as a platform to develop stimuli responsive materials. Ionogels are a class of materials that contain an Ionic Liquid (IL) confined within a polymer matrix. Recently defined as “a solid interconnected network spreading throughout a liquid phase”, the ionogel therefore combines the properties of both its solid and liquid components. ILs are low melting salts that exist as liquids composed entirely of cations and anions at or around 100 °C. Important physical properties of these liquids such as viscosity, density, melting point and conductivity can be altered to suit a purpose by choice of the cation/anion. Here we provide an overview to highlight the literature thus far, detailing the encapsulation of IL and responsive materials within these polymeric structures. Exciting applications in the areas of optical and electrochemical sensing, solid state electrolytes and actuating materials shall be discussed.
"Recently, electrodes based on derivatives of vitamin B 12 or on transition metal complexes of porphyrin, phthalocyanine, metallocenes, and Schiff base (Schulthess et al. 1985; Stepanek at al. 1986; Chaniotakis et al. 1988; Daunert and Bachas 1989; Huser et al. 1990; Daunert et al. 1991; Rothmaier and Simon 1993; Gao et al. 1994; Yuan et al. 1993; Shamsipur et al. 2003; Ganjali et al. 2003) have been reported as typical examples of nonconventional carriers with potential response characteristics apparently deviating from the Hofmeister sequence. Due to the outstanding work of the groups of Pretsch, Bakker, Bühlmann, and Meyerhoff, who reported many important theoretical and experimental works with the crucial achievement of improving the low detection limit near nanomolar concentrations, the field of ion-selective electrodes has expanded, especially in the last decades (Bakker et al. 1997; Mi et al. 1999; Malon et al. 2003; Radu et al. 2003). In view of the gradually understood importance of a lipophilic ionic additive (so-called ionic sites) in membrane cocktails, to potentiometric responses of membrane electrodes, the direct incorporation of lipophilic ionic additives into polymer membranes has become a fairly standard practice for anion-selective electrodes, in order to improve the selectivity of the studied electrodes towards the target anion and the response slopes, as well as to provide information of possible response mechanism of the chosen ionophore (Bakker et al. 1994; Steinle et al. 1998; Steinle et al. 2000; Schaller et al. 1994). "
[Show abstract][Hide abstract] ABSTRACT: Three kinds of transition metal chelates of unsymmetrical tetradentate Schiff base, o‐hydroxybenzophenone‐1,2‐diaminobenzene‐pyrrole‐2‐carbaldehyde(H2L), were synthesized to prepare anion‐selective electrodes and their anion response characteristics were investigated. The results show that the performances of the electrodes are considerably influenced by the nature of the central metals. The proposed electrode with the Cu(II)‐chelate and cationic additive demonstrated an anti‐Hofmeister selectivity sequence with a good selectivity towards thiocyanate in the following order: Thiocyanate>iodide>salicylate>perchlorate>bromide>nitrite>chloride>acetate>fluoride>nitrate>sulfite>sulfate. The electrode had an excellent linear response to thiocyanate from 3.4×10 to 1.0×10 M in phosphate buffer solution at pH 5.0 with a slope of −58.7 mV per decade, a detection limit of 1.6×10 M, and a fast response time within 5 s over the entire concentration series. Spectroscopic techniques and AC impedance were used to investigate the response mechanism to thiocyanate of the membrane doped with Cu(II)‐chelate. The preliminary application of the electrode for determination of thiocyanate in wastewater and urine samples is reported.
[Show abstract][Hide abstract] ABSTRACT: A triiodide-selective electrode based on copper (II)-Schiff base complex as a membrane carrier is proposed. The electrode
was prepared by incorporating the carrier into a plasticized polyvinylchloride (PVC) membrane and was directly coated on the
surface of a graphite electrode. The obtained electrode showed a near Nernstian slope of 57.0 ± 0.4 mV/decade to I
ions over an activity range of 1.0 × 10−5−1.0 × 10−1 M with a limit of detection of 4.8 × 10−6 M. The response time of the electrode was fast (5 s) and the electrode could be used for about 2 months without considerable
divergence in response. The potentiometric selectivity coefficients were evaluated and displayed anti-Hofmeister behavior.
The electrode was used as an indicator electrode in the potentiometric titration of the triiodide ion and in the determination
of ascorbic acid in vitamin C tablets.
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