Polymeric membrane electrodes with improved fluoride selectivity and lifetime based on Zr(IV)- and Al(III)-tetraphenylporphyrin derivatives

Abstract

Novel aluminum(III)-and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride selective ionophores for preparing polymer membrane-based ion-selective electrodes (ISEs). The influence of t-butyl-or dichloro-phenyl ring substituents as well as the nature of the metal ion center (Al(III) vs. Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called "sandwich membrane" method. All of the metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing membrane are discussed. It is shown that membrane electrodes formulated with the metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the metalloporphyrins can function as either charged or neutral carriers within the organic membrane phase. In contrast to previously reported fluoride-selective polymeric membrane electrodes based on metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade −1 ) as well as rapid (t < 80s) and fully reversible potentiometric fluoride responses are observed. Moreover, use of aluminum (III)-t-butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional life-time.

Metalloporphyrin-based acetate-selective electrodes as detectors for enzymatic acetylcholine determination in flow-injection analysis system

“…1). Latter compound, when tested as fluoride-selective ionophore, was found to display some preferable response parameters, including fast and Nernstian response towards F − anions, with relatively long lifetime of 2 months [31].…”

Classification of amino acids and oligopeptides with the use of multi-mode chemical images obtained with ion selective electrode array

“…5,10,15,20-Tetrakis(4-t-butylphenyl)porphyrin was purchased from Frontier Scientific (Logan, UT, USA). Zirconium (IV) complex of this porphyrin (Zr[t-BTPP]) was obtained by metallation of this compounds with ZrCl 4 in benzonitrile (190 • C for 24 h) [15].…”

Responses of Metalloporphyrin‐Based Ion‐Selective Electrodes to pH

“…The addition, however, induces the formation of cationic dimers [12,13], which may interfere with reliable potentiometry. The merits and demerits of this reaction were discussed [14], and the countermeasure, such as the use of picket fence-porphyrins and the immobilization of the carrier onto a polymer network, have been proposed [12,[15][16][17].…”