An Ion-Selective Electrode for Acetate Based on a Urea-Functionalized Porphyrin as a Hydrogen-Bonding Ionophore

Abstract

An ion-selective electrode for acetate based on (α,α,α,α)-5,10,15,20-tetrakis[2-(4-fluorophenylureylene)phenyl]porphyrin as an ionophore that has no metal center and forms hydrogen bonds to the analyte is described. At pH 7.0 (0.1 M HEPES-NaOH buffer), the electrode based on this ionophore and cationic sites (50 mol % relative to the ionophore) responds to acetate in a linear range from 1.58 × 10(-)(4) to 1.58 × 10(-)(2) M with a slope of -54.8 ± 0.8 mV/decade and a detection limit of (3.06 ± 1.15) × 10(-)(5) M. Selectivity coefficients determined with the separate solution method (SSM) indicate that interferences of hydrophobic inorganic anions are relatively small (log[Formula: see text] (SSM): NO(3)(-), +0.68; SCN(-), +0.60; NO(2)(-), +0.22; I(-), +0.20; ClO(4)(-), +0.12; Br(-), -0.13). Responses to anions that are good hydrogen bond acceptors, i.e., Cl(-), HSO(3)(-), and HCO(3)(-), were Nernstian and were weaker than the response to acetate (log[Formula: see text] (SSM): -0.54, -0.56, and -1.34, respectively). Negligibly small responses were observed for very hydrophilic anions, i.e., F(-), SO(4)(2)(-), and H(2)PO(4)(-)/HPO(4)(2)(-). While aliphatic carboxylates such as formate, propanoate, pyruvate, and lactate gave Nernstian responses similar to acetate, interferences of salicylate and benzoate were considerably decreased in comparison with electrodes based on cationic sites only. Concentrations of acetic acid in vinegar samples were determined by direct potentiometry and agreed with values determined by a standard enzymatic method.

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.…”

Thiocyanate Ion-selective PVC Membrane Electrode Based on N,N′-Ethylene-bis(4-methylsalicylidineiminato)nickel(II)

“…34 Table 4 lists the linear range, detection limit, slope, response time and selectivity coefficients of some of other thiocyanateselective electrodes against the proposed thiocyanate-selective electrode for comparative purposes. 25,[35][36][37][38] As can be seen from the table, the selectivity coefficients obtained for the proposed electrode are superior to those reported for other SCN --selective electrodes listed in Table 4.…”

Potentiometric response and mechanism of anionic recognition of heterocalixarene-based ion selective electrodes

“…ISEs are also of obvious interest because they can help translate the chemistry of new substrate binding systems into tools that can be used to recognize selectively various targeted species in the presence of potentially interfering analytes. In the specific case of anion recognition, this approach has been explored extensively by Umezawa, Meyerhoff, Simon, Reinhoudt, Schmidtchen and others using a range of receptors including bis-guanidinium [1][2], porphyrins [3], protonated polyamines [4][5][6][7], and protonated sapphyrins [8][9][10], as well as a variety of Lewis acidic systems such as calixarenes [11][12][13][14][15], uranylsalenophenes [16][17], metalloporphyrins [18][19][20][21][22], metallocenes [23], other organometallic derivatives [24][25][26], and fluorinated compounds [27].…”