Anion selective optical sensing with metalloporphyrin-doped polymeric films

Abstract

Metalloporphyrins [Mn(III) and In(III)] are investigated as active polymer fihn components in the design of reversible anion-selective optical sensors. The optical measurements are made by casting thin plasticiied polymer films (PVC, polyurethane, etc.) containing the given metalloporphyrhts on glass plates. When bathed in aqueous test solutions, the optical response of such fihns is based upon the selective extraction of anions by metalloporphyrins into the organic membrane phase. Changes in optical absorbance occur via either of two mechanisms. For fihns based on Mn(II1) tetraphenylporphyrins, the porphyrin itself can serve simultaneously as the ionophore and chromophore for the detection of iodide ions. In this instance, direct ligation of iodide as an axial ligand of the central Mn(II1) results in a change in the molar absorptivity of the soret band of the porphyrin. In the case of In(II1) octaethylporphyrin, the incorporation of an appropriate pH-indicator dye along with the metalloporphyrin is required to achieve films with optical selectivity toward nitrite and chloride. The analytical characteristics of these porphyrin-based fihns with respect to anion response time, dynamic measurement range, and reproducibility, are discussed.

Luminescent lanthanide sensors for pH, pO2 and selected anions

“…Alternatively, 'collisional' deactivation of the singlet and triplet excited states -for example by halide anions and triplet O 2 -may be involved. Such processes have frequently been harnessed in the design of classical fluorescent sensors and are used in the measurement of intracellular chloride concentrations with substituted quinolines [29] and of pO 2 (e.g. using Ru(bpy) 3 2 + [30] or Pd/Pt porphyrins [31]) in a variety of thin film applications.…”

“…The fluorescence of N-alkylated quinolinium, acridinium and phenanthridinium ions is quenched by halide anions in aqueous media [29]. This phenomenon has been applied to the development of assays for the chloride ion in biological media [32].…”

Responses of Metalloporphyrin‐Based Ion‐Selective Electrodes to pH

“…The central metal ions exhibit a wide range of anion selectivities, depending on the "hard and soft acids and bases" principle. For example, Al(III) complexes show a high selectivity to F À [1][2][3], while In(III) complexes to Cl À [4][5][6][7][8][9]. With a view to enhancing the selectivity, reducing the electric resistance, elongating the life time, and ensuring the theoretical response, lipophilic anions were added at some molar fractions to the complex as in other charged carriers [10,11].…”

“…The ISEs based on metalloporphyrins, in the absence of a sample anion, showed a linear potential response to pH over a wide range; (carrier, pH range, potential slope): ([Mn(tpp)Cl], 3.5-10, 52) [18]; ([Sn(tpp)Cl 2 ], 3.5-10, 40) [19]; ([Co(tpp)(NO 2 )], 4-10, 40) [20]; ([MoO(tpp)(OEt)], 1.5-11, 57) [21]; ([In(oep)Cl], 2.5-4, 59) [4]; ([Cr(tpp)Cl], 6-9.5, 49) [22]; (In(HEPEAC)Cl), 7.5-10, 46) [15]; ([TiO- (tpp)], 2-11, 44) [23]; ([VO (tpp)], [4][5][6][7][8][9][10][11]48) [23]; ([Hf-(tpp)Cl 2 ], 7-12, 52) [23]; ([Zr(tpp)(OH) 2 ], 2-13, 43) [23,24, H 2 tpp: tetraphenylporphin, H 2 oep: octaethylporphin, HEPEAC: a porphyrin covalently attached to a polymer]. The pH adjustment of a sample solution is thus usually essential for the potentiometric determination of an anion, although the pH response is diminished in the presence of the sample anion [25][26][27][28][29][30].…”

Efficient Ion-Pair Extraction of Potassium Chloride from Aqueous Phase into Nitrobenzene Containing Dicyclohexyl-18-crown-6 as Cation Binder and Diphenylthiourea as Anion Binder

“…[16][17][18] If the anion recognition is performed by solvent extraction, the function of these anion receptors would be applicable to various separation and sensing systems such as membrane transport and optode analysis. [19][20][21][22][23][24] To prove this feasibility, we report herein an efficient synergistic effect of a thiourea receptor for an ion-pair extraction of potassium salts by dicyclohexyl-18-crown-6 (DC18C6) through hydrogen-bonding interaction. DC18C6 is well known as a specific binder for potassium cation.…”