Mercury(II) Ion-Selective Electrodes Based on p-tert-Butyl Calix[4]crowns with Imine Units

Abstract

Due to the toxic nature of mercury, many methods have been developed for its detection and treatment in various chemical systems. Of these, potentiometric detection based on two types of ion-selective electrodes is described in the literature for the detection of mercury ions. 1,2 One is a solid-state mercury(II) sulfide electrode; 1 the other is a liquid-membrane electrode, 3 which is one of the most important types of chemical sensors. Liquid-membrane electrodes, prepared with a poly(vinyl chloride) immobilized carrier, are easy to implement, inexpensive and reliable. [4][5][6][7] These electrodes show good stability, a relatively fast response time and a wide dynamic range. Many organic and inorganic compounds have been investigated as sensing agents in producing ISEs. 8-11Dithiazone, 12 1,4-dithia-12-crown-4, 13 hexathia-18-crown-6-tetrone, 14 and 2-mercaptobenzimidazole 15 have been reported in the literature as Hg 2+-PVC-based membrane electrodes having a good Nernstian response and a high ion selectivity.Calixarenes, due to their suitable complexation characteristics with cations, have been used as neutral ionophores in ionselective electrodes. [16][17][18][19] Calixarene tetraesters and related derivatives have been used as sensing agents in sodium-sensors for the chemical analysis of sodium in body fluids. 19,20 Structural modifications of the calix and the binding sites and a variation in the cavity size have been mainly responsible for the use of calixarenes as selective sensing agents for ions other than sodium. [21][22][23][24][25][26][27] Calixarenes with soft donor atoms as binding sites have also been reported as ion-selective electrodes for heavymetal ions (silver, copper, lead). [28][29][30] Recently, silver and cesium ion-selective electrodes have been reported by our group. [24][25][26][27] Continuing efforts in the same direction, the present paper deals with a mercury(II) ion-selective electrode based on the p-tert-butyl calix[4]crown derivative with imine units as an ionophore (Scheme 1). The electrode exhibits a good response for mercury(II) ions over a concentration range of 5.0 × 10 -5 -1.0 × 10 -1 M with a near-Nernstian slope of 27.3 mV per decade. The electrode shows high selectivity for mercury(II) ions over most of the alkali, alkaline-earth and transition metal ions (Na + , ExperimentalIonophore p-tert-Butyl calix[4]crowns with imine units used as an ionophore in this work was synthesized in our laboratory. Synthesis of the ionophore involved the formation of an aldehyde by generating a phenoxide ion, followed by an attack on the bromides to give dialdehyde, which was then condensed with the calixamine to give a [1+1] Schiff base product (Scheme 1). Other reagentsAll of the reagents used were of analytical-reagent grade. High-molecular-weight poly(vinyl chloride) (PVC), bis(2-ethylhexyl)sebacate (DOS), bis(2-ethylhexyl)phthalate (DOP), bis(2-ethylhexyl)adipate (DOA), tri-n-butylphosphate (TBP), 1-decanol, and especially dried tetrahydrofuran were used as received from Fluka. Sodiu...

New Polymeric Membrane Electrode for Clarithromycin Determination

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Effect of π Electrons on the Detection of Silver Ions by Ion-selective Electrodes Containing Tripodal Broom Molecules as an Ionophore

“…For example, ionophores containing nitrogen or sulfur atoms, which are soft ligands according to the "hard and soft acids and bases" theory, have been utilized to prepare ion-selective electrodes because of their high affinity for soft metals, such as silver, thallium and mercury ions, and so on. [1][2][3][4][5][6][7] However, ionophores containing nitrogen or sulfur atoms tend to be influenced by the pH. Moreover, the strong affinity of nitrogen and sulfur atoms for soft metal ions at the interface of membranes causes low selectivity, slow response, and weak sensitivity.…”

Mercury(II) Ion-Selective Polymeric Membrane Sensors for Analysis of Mercury in Hazardous Wastes

“…Many sensing agents have been described, including calixarene derivatives containing thiazole azo group, 11 salicylaldehyde thiosemicarbazone, 12 Schiff's bases, 13 ethyl-2-benzoyl-2-phenylcarbamoyl acetate, 14 2-mercapto-benzothiazole or hexathiacyclooctadecane, 15 dibenzodiazathia-18-crown-6 dione, 16 substituted aza crown ionophores, 17 hexathia-18-crown-6 tetrone, 18 1,3-diphenylthiourea, 19 tetrathia-diazacyclotetradeca-2,9-diene, 20 substituted diaza crown ethers, 21 and p-tert-butyl calix-4-crowns with imine units. 22 Most of these sensors, however, exhibit interference from Pb 2+ , 15,17 Ag + , 11,12,15,17,21,22 NH4 + , Na + and K + , 12,15 Cu 2+ and Zn 2+ . 21 The present work describes two Hg 2+ ion sensors incorporating 5,5′-dithio-bis(2-nitrobenzoic acid) (DTNB) and tricyclazole (TCZ) as electroactive materials dispersed in PVC matrix membranes.…”