Mercury ion‐selective polymeric membrane electrodes based on substituted diaza crown ethers

Abstract

The potentiometric selectivities of membranes based on new N,N'-substituted 4,13-diaza-18-crown-6 ethers were determined under different internal filling electrolytes and conditioning time of the membranes. The preference of Hg2+ over other divalent cations was observed for compounds bearing 2-methylquinolyl or 2-methylquinolyl-1-oxide groups. The membrane electrodes with ionophores 1 and 2 exhibited a linear response in the activity range 10-5-10-3 M Hg(NO&. IilrTRODUCTIONThe past two decades of so-called supramolecular cheniistry have witnessed many interesting syntheses of the ionophores useful in the membrane ion-selective electrodes, or ISFET-transistors. The need for environmental pollution monitoring prompted development of lipophilic thiacrown ether derivatives as heaq-metal ionselective ionophores [ 1-21, We have recently demonstrated the synthesis of the two diaza-crown ethers incorporating 2-quinolylmethyl and 2-quinolylmethyl-1-oxide units, which possess preference Hg"-selectivity over other divalent cations by means of PVC-membrane technique [ 3 ] .This article shows Hg(I1)-response of the PVC membrane electrodes based on substituted diaza-crown ethers, and their potentiometric selectivities under various measurement conditions. EXPERIMEWM ChemicalsAll of the metal salts employed here were analytical grade and were purchased from POCh Gliwice, Poland. Standard solutions (0.1 M) of metal salts in redistilled water were prepared; working solutions were prepared as required by suitable dilution with redistilled water. Membrane PreparationThe composition of the membrane was 1% m/m ionophore, 30% m/m PVC, 70 mol-% KTp-CIPB (with respect to the ionophore), and 68-69% m/m o-NPOE as plasticizer. The membrane preparation was described earlier [4].The electrodes were left overnight in conditioning solution, e.g., redistilled water, aqueous solutions of KCl, CuCl,, or HgCI,. Two electrodes were prepared for each composition of membrane. Emf Measurements

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

“…Potentiometric mercury-selective membrane sensors based on the use of DTNB and TCZ as neutral ionophores, dioctylphthalate (DOP) as a plasticizer, NaTPB as an anionic excluder and PVC as a polymeric matrix show fast, stable, reproducible and selective response characteristics toward Hg 10 -2 mol l -1 ), [14][15][16]20,21 provide lower detection limit (5.0 × 10 -6 mol l -1 ), 16,21 show fast response (∼10 s) and exhibit better selectivity than those previously reported Hg 2+ sensors. Applications to the determination of mercury in hazardous wastes are demonstrated; the results compare favorably with data obtained with cold vapor atomic absorption spectrometry.…”

“…Applications to the determination of mercury in hazardous wastes are demonstrated; the results compare favorably with data obtained with cold vapor atomic absorption spectrometry. Silver ions, which seriously interfere with many suggested sensors, 9,10,16,20,21 have little influence on the response of the proposed sensors and the effect of lead ions can be avoided by addition of sulfate ions prior to analysis. …”

“…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.…”

“…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. The sensors exhibit high sensitivity, long term stability, and reasonable selectivity for Hg 2+ ions over many common metal ions and can be successfully used for accurate determination of mercury contents of some hazardous wastes.…”

Potentiometric Response of a Neutral-carrier-based Membrane to Aqueous Mercury in Cl−-rich Media

“…Crown ether functionalized compounds were considered to be representative ionophores, 4,5 and Schiff bases, 6 thioureas, 7 thiols, 8 and calixarene derivatives 9,10 were also tested for ISEs. Although these previous neutral-carrier-based ISEs were successful with respect to the selective detection of mercury ions, specifically Hg 2+ , it should also be noted that most of the studies were conducted under conditions where nitrate (NO3 -) was the predominant anionic species.…”