Behavior of a Polypyrrole Solid Contact pH-Selective Electrode Based on Tertiary Amine Ionophores Containing Different Alkyl Chain Lengths between Nitrogen and aPhenyl Group

Abstract

There have been huge developments in ion selective electrode (ISE) research over the past 40 years. Nevertheless, the traditional barrel configuration 1 was proved to be cumbersome for some applications.Thus attempts were made for miniaturization, which brought about some new sensing systems, called wire-type electrodes (WTEs), such as the solid contact electrodes (SCEs) 2,3 and coated wire electrodes (CWEs). 4 In WTEs, a total elimination of the internal filling solution provides new advantages. Simplicity of design, lower costs, mechanical flexibility, the possibility of miniaturization and microfabrication have widened the applications for wiretype electrodes in the fields of medicine and biotechnology. Especially, in SCEs, after polymerization, this polymer-coated metal electrodes are dipped into in a PVC cocktail membrane solution until a bead is formed. These electrodes based on the electropolymerization method of amino derivatives onto the metal surface 5 produced very good results, such as stabilization of the base potential, reproducibility, best selectivities, wide response ranges and fast response time.Because electroconductive polymers, such as polyaniline and polypyrrole, show well-documented electronic/ionic conductivity, 6 many researchers have utilized them as an electron conducting polymer layer having anionic dopants. 7 Thus, in this study we used an electoconductive polypyrrole layer which could act as a solid contact between a pH-selective PVC membrane containing the ion carrier and a metal contact.In recent years, there have been several reports on a hydrogen ion-selective electrode and ionophores. 8 Most of these electrodes were based on PVC membranes containing tertiary amine compounds. 9 In these tertiary alkyl amine compound ionophores, the representative hydrogen ion ionophore was tridodecylamine, which showed good selectivity and the slopes of the EMF responses. However, because measurements were limited to the dynamic range of pH 4.5 -11.0, to measure a greater alkaline pH range, other ionophores had to be studied. The former researchers reported that as the pKa value of the ionophores in a membrane increased, the response range of electrodes containing the tertiary amine ionophores widened. 10Also in our lab, we recently reported that tribenzylamine ionophore 11 yielded a wider applicable pH range and a better selectivity coefficient than any other trialkylamine ionophore, including tridodecylamine. 12 In the present work we used a tertiary amine ionophore including a phenyl ring, like a tribenzylamine, and intended to produce an all-solid contact potentiometric sensor for hydrogen ion based on polypyrrole, which was covered with a plastic PVC membrane including these ionophores. We synthesized a tris(2-phenylethyl)amine ionophore and a tris(3-phenylpropyl)amine ionophore, which were compared with the result of a tribenzylamine ionophore. We also wanted to prove that the response ranges are affected (shifted dynamic range to the alkali range) as the alkyl chain length between the n...

Potentiometric Ion Sensors

“…Polypyrrole doped with tetraphenylborate was used as a solid contact in K + -ISEs in order to have well-defined ion transfer between the conducting polymer and the ion-selective plasticized poly(vinyl chloride) (PVC)-based membrane . Polypyrrole doped with different anions was also employed as a solid contact in pH electrodes based on polymer membranes containing tertiary amine ionophores …”

A solid-contact Pb2+-selective polymeric membrane electrode with Nafion-doped poly(pyrrole) as ion-to-electron transducer

“…For example, PPy doped with calcium complexing ligand Tiron was applied as solid contact for the construction of all-solid-state ISEs, e.g., calciumselective electrode [15]. Pandey et al [16] [17]. Nafion has been widely used as cation exchanger and applied to fabricate different kinds of chemically modified electrodes.…”

Construction of a Solid Contact Polymeric Membrane Electrode for pH Measurements in Acidic Media

“…The potentiometric selectivity coefficients were determined by the fixed interference method (FIM) 38,39 at 1.0 × 10 −2 M concentration of the interfering species which was chosen as the common concentration in the previous reported H + -selective electrodes. [4][5][6][7] The resulting se- lectivity coefficients obtained for the proposed solid contact H + -ion selective electrode were listed in Table III. From the data given in Table III, it is revealed that the selectivity coefficients are of the order of 10 −3 or smaller which indicate that these ions cause negligible interference on the functioning of the proposed SCE.…”

“…So, non-glass pH electrodes have been studied by many researchers. [2][3][4][5][6][7] These reported non-glass electrodes were solid or liquid membrane electrodes based on neutral carriers that exhibited a number of advantages, including low electric resistance, safe handling, capability of miniaturization, wide applicable pH range, suitable selectivity and promising applications in some aggressive media. Some of these reported ionophorebased hydrogen selective electrodes had selectivity coefficients which were absolutely comparable with those of glass electrode.…”