A Chloride Ion-Selective Solvent Polymeric Membrane Electrode Based on a Hydrogen Bond Forming Ionophore

Abstract

A chloride-selective solvent polymeric membrane electrode based on a neutral hydrogen bond forming ionophore, poly(vinyl chloride) (PVC), the plasticizer 2-nitrophenyl octyl ether (o-NPOE), and cationic sites (50 mol %, relative to the ionophore) is described. At pH 7.0 (HEPES buffer), this electrode responds to chloride in a linear range from 10-5 to 10-2 M with a slope of (−54.0 ± 1.0) mV/decade and a detection limit of (6.5 ± 3.0) × 10-6 M. As compared to conventional anion-exchanger electrodes, the interference of SCN-, Br-, NO3 -, I-, and even salicylate is considerably reduced, as shown by the selectivity coefficients determined with the matched potential method (MPM) in the chloride concentration range 10-2.34−10-2.04 M (log (MPM): Sal-, +1.8; SCN-, +1.6; NO3 -, +0.7; I-, +0.5; Br-, +0.4). Because the discrimination of the more hydrophilic anions SO4 2-, HSO3 -/SO3 2-, OAc-, HCO3 -, and H2PO4 -/HPO4 2- is too large for a determination of accurate selectivity coefficients in this high chloride concentration range, corresponding values for the range 10-5.00−10-4.70 M Cl- have been determined (log (MPM): SO4 2-, −1.2; HSO3 -/SO3 2-, −2.0; OAc-, −2.3; HCO3 -, −2.6; H2PO4 -/HPO4 2-, < −3.5), showing here, too, a good selectivity for Cl-. The chloride ion concentration in certified control horse serum was determined by the standard addition method as 102.1 mM with a coefficient of variation of 0.42% (n = 6). This result is in excellent agreement with the certified value of 102.3 mM, as determined by coulometry, and demonstrates the applicability of this sensor for measurements in biological samples. The selectivity upon storage of the electrode in buffer solution for 4 weeks decreases but is still considerably better than that for a freshly prepared anion-exchanger electrode.

Biogenic Amine-Sensitive Membrane Electrodes Using the Hydrogen Bond-Forming Ability of Solvent Mediators

“…[2][3][4][5][6][7][8][9][10][11][12] Thus, we used an experimental kit having a porous membrane filter, which was infiltrated with the solvent mediator.…”

“…[1][2][3][4][5][6][7] Typical examples are the use of hydrogen-bonding ionophores with urea or thiourea units, which were successfully used to produce anion-selective electrodes, including those to nucleotides, Cl -, SO4 2-and acetate. [2][3][4][5] Hydrogen-bonding solvent mediators, such as tris (2-ethylhexyl) phosphate and tricresyl phosphate, have also been used to construct organic ammonium ion-selective electrodes, [8][9][10][11] through the interaction between NH3 + groups of organic ammonium ions and the negatively polarized oxygen atoms in the P=O groups of phosphate esters. 7 In the process of screening various phosphate and thiophosphate esters, we found that prothiofos ((O-(2,4-dichlorophenyl) O-ethyl S-propyl phosphorodithioate, see Fig.…”

Application of Gold Nanoparticles to Spectrophotometric Sensing of Hydrophilic Anions Based on Molecular Recognition by Urea Derivative

“…Thus, a variety of these artificial host molecules with specific hydrogenbonding ability have been reported for sensing hydrophilic anions. [1][2][3][7][8][9][10][11][12][13][14] As mentioned above, anion recognition under aqueous conditions, and therefore effective sensing systems of hydrophilic anions, are still challenging to study. This difficulty in anion sensing can be ascribed to the low charge density, geometrical variety, and high hydration energy of anions.…”

Anion Sensing by a Thiourea Based Chromoionophore via Hydrogen Bonding

“…In contrast, only a few chromoionophores have been reported for the colorimetric determination of anions in solution. [4][5][6][7] In design and fabrication of new anion receptors for applications in aprotic media [8][9][10][11] , the (thio)urea group as hydrogen bond donor has recently drawn much interest as a functional group for neutral receptors to recognize mono-and dicarboxylate anions, halide anions, sulfate, as well as dihydrogenphosphate etc. 6c,9-17 Wilcox et al 17 have recently shown substituent effects in arylthiourea upon binding with a zwitterionic sulfonic acid in chloroform.…”