Sulfonamides as ionophores for ion-selective electrodes. IV. New secondary sulfonamide podands and cryptands

New compounds — podands and cryptands with two secondary sulfonamide groups —have been synthesized and are described. They were tested as ionophores for guanidinium ions in PVC-membrane electrodes with bis (2-ethylhexyl)sebacate (DOS) as plasticizer.     

Phosphoryl Containing Podands as Carriers in Plasticized Membrane Electrodes Selective to Quaternary Ammonium Surfactants

Open chain polyethers with phosphoryl-containing terminal groups have been studied as carriers in plasticized membrane electrodes that are selective towards cationic surfactants. Host–guest complexation has also been studied by means of batch extraction and bulk membrane transport experiments. For the various guests, the bulk membrane (chloroform) transport rate decreases in the series tetraalkyl ammonium > alkyl pyridinium > alkyl ammonium, while the series of solvent extraction efficiency is exactly opposite; an explanation for this behaviour is proposed. The performance of electrode membranes follows the series for bulk membrane transport. Among the ISE membranes of various composition, one containing the longest (seven oxygen atoms) podand, o-nitrophenyl octyl ether (plasticizer), and sodium tetraphenyl borate (anionic additive) performs the best. The slope of the electrode function equals 58.5 mV/decade, the detection limit for dodecyltrimethylammonium is 3.2 × 10^-6 M. ISE response time is 5–10 s, the working pH range is 2–11 and lifetime is at least 6 months. The electrode selectivity is significantly better than that of conventional ion-association and crown ether based electrodes.     

Sulfonamides as ionophores for ion-selective electrodes. II. Macrocyclic ligands containing two sulfonamide groups as ionophores

Ten macrocyclic compounds (1–10), each containing two sulfonamide groups have been incorporated into PVC membrane electrodes as ionophores. Their selectivity towards alkali and alkaline earth metal cations has been studied and compared to selectivities found in cation transport experiments.     

Structural Selectivity of Calix[m]pyrroles[n]furans (m + n = 4) as Ionophores in Ag(I) Ion-Selective Electrodes

A series of octamethylcalix[m]pyrroles[n]furans (m + n = 4), such astrans-octamethylcalix[2]pyrroles[2]furans L ₁ ),cis-octamethylcalix[2]pyrroles[2]furans (L ₂ ) and octamethylcalix[1]pyrrole[3]furans (L ₃ ) have been studied as sensors in liquid membrane ion-selective electrodes for Ag(I) ion. The electrode based on L ₁ , trans-N₂O₂ porphyrinogen, gave the best results with a wide working concentration range of 1.0 × 10^-1 - 1.0 × 10^5.6 M and a Nernstian slope of 57.0 mV/decade. This electrode exhibited a fast response time of 30 s and high selectivity over a number of mono-, di- and tri-valent cations, with only Tl(I) and Hg(II) ion interferences. The effect of anion excluders on the performance of the membrane electrodes has been also studied. The electrode based on L ₁ showed no significant potential changes in the range 2.5 < pH < 7.5. The crystalstructure of L ₃ , NO₃ porphyrinogen, was determined by single crystal X-ray analysis. The crystallographic analysis of L ₃ reveals that its structure is a saddle-shaped 1,3-alternate conformation with enough space to accommodate Ag(I) in the three dimensional cavity.     

Ion-Selective Electrodes for the Determination of Antimony and Thallium Based on Water-Insoluble Basic Dye Salts

Abstract

Hexachloroantimonate(V) and tetrachlorothallate(III) salts of Sevron Red L (C.I. Basic Red 17), Sevron Red GL (C.I. 11,085), Flavinduline O (C.I. 50,000) and Phenazinduline O have been applied in liquid-state ion-selective electrodes for the determination of antimony and thallium. The slope of potential versus pM graphs approach full Nernstian response in the range 10 M (Sb) and 10^?6 M (T1) to 10^?2 M. An unusual feature of the electrodes is their response to antimony(III) as well as to antimony(V).     

Urea Biosensors Based on PVC Membrane Ion-Selective Electrodes

Abstract

This paper presents a general method of enzyme immobilization at the surface of ion selective membranes. Covalent binding of enzymes directly on the electrode surface is a very effective method that results in stable enzymatic membranes. As an example the construction of enzymatic sensors for urea determination based on ammonium and hydrogen carbonate ion selective electrodes is presented. The optimum working conditions for these biosensors were found. Bioelectrodes based on an ammonium sensor show very good analytical parameters: dynamic stability - over 2 months without decrease of sensitivity, response time - shorter then 20 s. high sensitivity, determination range from 0.3 to 70 mM. In the contrast to the ammonium ion based biosensors, those constructed on the basis of anion selective electrodes have worse analytical parameters. It is mainly due to poor selectivity and instability of an applied ion selective electrode. In spite of this, both types of urea biosensors were used for measurements in the differential potentiometry mode. The application of such system increased the sensitivity of urea determination.     

A New Neutral Carrier for Silver Ions Based on a Bis(Thiothiazole) Derivative and its Evaluation in Membrane Electrodes

Membrane electrodes based on 2,2-dithiobis(benzothiazole), DTBBT, as a neutral carrier for silver ions are described. Silver-selective membrane electrodes formulated with 2wt% DTBBT ionophore and 50mol% TFPB in an FPNPE plasticized poly (vinyl chloride) exhibited near-Nernstian responses towards silver ions (60.3±0.5mVdecade^–1) over a wide silver ion activity range of 0.83µM to 94mM. Increasing the amount of anionic sites, TFPB, to 100 or 150mol% (relative to the DTBBT weight) resulted in super-Nernstian responses toward silver ions. Membrane electrodes prepared using a low dielectric constant plasticizer, however, exhibited sub-Nernstian responses. Polymer membrane electrodes with optimal composition (i.e., 2wt% DTBBT, 50mol% TFPB in FPNPE plasticized poly(vinyl chloride)) exhibited high potentiometric selectivity towards silver ions over alkali, alkaline earth, transition metal ions, as well as heavy metal ions such as Hg²⁺ and Pb²⁺. A good correlation was found between the potentiometric selectivity coefficients and the change in the UV-visible spectra of the ionophore upon exposure to different metal ions. The overall performance of the silver-selective membrane electrodes based on DTBBT ionophore, which is available at low cost, was found to be comparable to the performance of silver electrodes prepared with Fluka silver ionophore-IV. A DTBBT-based silver electrode was used as an indicator electrode for titrations of silver ions using standard sodium chloride solutions. Sharp inflections occur at the end point, and the data obtained showed 99.4% recovery with a standard deviation of 0.7% (n=3). In addition, the applicability of the DTBBT-based silver-selective electrode is illustrated by measuring the silver concentrations in natural water spiked with silver nitrate and by analyzing the silver in electroplating wastewater samples. The results obtained utilizing a DTBBT-based silver electrode showed very good agreement with the standard methods of analysis.     

Aluminum(III) Porphyrins as Ionophores for Fluoride Selective Polymeric Membrane Electrodes

Aluminum(III) porphyrins are examined as potential fluoride selective ionophores in polymeric membrane type ion‐selective electrodes. Membranes formulated with Al(III) tetraphenyl (TPP) or octaethyl (OEP) porphyrins are shown to exhibit enhanced potentiometric selectivity for fluoride over more lipophilic anions, including perchlorate and thiocyanate. However, such membrane electrodes display undesirable super‐Nernstian behavior, with concomitant slow response and recovery times. By employing a sterically hindered Al(III) picket fence porphyrin (PFP) complex as the membrane active species, fully reversible and Nernstian response toward fluoride is achieved. This finding suggests that the super‐Nernstian behavior observed with the nonpicket fence metalloporphyrins is due to the formation of aggregate porphyrin species (likely dimers) within the membrane phase. The steric hindrance of the PFP ligand structure eliminates such chemistry, thus leading to theoretical response slopes toward fluoride. Addition of lipophilic anionic sites into the organic membranes enhances response and selectivity, indicating that the Al(III) porphyrin ionophores function as charged carrier type ionophores. Optimized membranes formulated with Al(III)‐PFP in an o‐nitrophenyloctyl ether plasticized PVC film exhibit fast response to fluoride down to 40 μM, with very high selectivity over SCN^?, ClO₄^?, Cl^?, Br^? and NO₃^? (k^pot<10^?3 for all anions tested). With further refinements in the membrane chemistry, it is anticipated that Al(III) porphyrin‐based membrane electrodes can exhibit potentiometric fluoride response and selectivity that approaches that of the classical solid‐state LaF₃ crystal‐based fluoride sensor.     

Synthesis of Tetra-N-substituted 1,10-dioxa-4,7,13,16- tetraazacyclooctadecanes and their Application as Lead (II) Selective Electrodes. X-ray Crystal Structure of 4,7,13,16-tetrathenoyl-1,10- dioxa-4,7,13,16-tetraazacyclooctadecane

Tetra-N-substituted 1,10-dioxa-4,7,13,16-tetraazacyclooctadecanes (tetraazacrown ethers) (1-5) have been synthesised. Each compound was incorporated in a PVC membrane that provided the basis for a lead-selective potentiometric electrode. The electrode based on the 4,7,13,16-tetrathenoyl-1,10-dioxa-4,7,13,16- tetraazacyclooctadecane (5) ionophore bearing four thenoyl functional subunits exhibited excellent lead (II) ion selectivity with only Ag+ and Hg2+ significantly interfering. The crystal structure of this host (5) has been determined by single crystal X-ray analysis. Crystal data. C32H36N4O6S4, M 700.9, monoclinic, space group P21/c, a, 10.315(4), b, 13.635(2), c, 14.357(6)Å, 124.63(2)°, V 1661.6(9)Å3, Dc 1.40 g cm-3, Z 2, Cu 29.90 cm-1. Final residuals R, Rw were 0.054, 0.082 for the observed data.     

Potentiometry with Solid Electrodes Based on Oxide Bronzes of Vanadium and Tungsten

A mathematical model is presented and the possibility of analytic application of electrodes of vanadium and tungsten oxide bronzes for the ion-selective determination of concentrations of oxygen-containing vanadium(5+) and tungsten(6+) ions in aqueous solutions 10^–5 to 10^–2 M at controlled pH is established.     

Polymeric ISE for Hydrogen Sulfite Based on Bis‐Urea Calix[4]diquinones as Neutral Lipophilic Ionophores

A new PVC membrane electrode for HSO₃^? anion based on bis‐urea calix[4]diquinones I–VI as neutral ionophores is prepared. Of the various membranes prepared, the membrane based on calix[4]diquinone III exhibits a linear stable response over a wide concentration range (6.0×10^?5?1.0×10^?2) with a slope of ?51.5 mV/decade and a detection limit of 2.2×10^?6 M. With the exception of HSO₃^? anion, the remainder of the anions responds based on their hydrophobicity. The membrane revealed improved selectivity coefficients for HSO₃^? over a wide variety of other anions, and the comparable selectivity for the HSO₃^?selective membranes is iodide anion.     

PVC膜离子选择电极检测下限的优化

价格低廉、携带方便、适用浓度宽、操作简单快捷、能耗低的离子选择电极在医院、分析实验室、野外等领域得到了越来越广泛的应用。尽管如此,由于PVC膜中存在的离子流严重破坏了更低检测下限的获取,限制了离子选择电极的进一步发展。因此,本文从减小甚至消除PVC膜中存在的离子流角度出发,系统论述了优化PVC膜离子选择电极检测下限的原理和优良策略,根据收集归纳的大量数据定量阐述传感膜组成的优化、电极组装和调制、应用旋转电极以及电流极化处理等对检测下限的优化提升作用,进一步总结出各种方法的改善规律,分析它们的优势和面临的问题。提出在PVC铸膜液中要突破传统配方,减小增塑剂和离子交换剂用量,以抑制传感膜两侧的离子流,同时外加电流补偿处理等也是降低电极检测下限的有效方法,对检测下限的改善最好的可降低5个数量级。这一总结为PVC膜离子选择电极的高性能化明确了研究方向。     

Etilefrine Plastic Membrane Electrodes Based on Individual and Mixed Ion-exchangers of Etilefrinium Phosphotungstate and Tetraphenylborate.

Abstract

Etilefrine hydrochloride (EfCl) selective PVC membrane electrodes based on Etilefrinium phosphotungstate (I), Etilefrinium tetraphenylborate (II) and a mixture of both (III) were prepared, The electrodes exhibited near Nernstian response over the concentration ranges 5.0 × 10^?6 - 1.0 × 10^?1, 6.3 × 10^?6 - 1.0 × 10^?1 and 6.3 × 10^?5 - 1.0 × 10^?1 M EfCl for electrodes I, II and III, respectively. The working pH ranges of electrodes I, II and III were 10 - 8.0, 10 - 7.5 and 10 - 7.5 and their isothermal coefficients were 0.00150, 0.00088 and 0.00072 V/°C, respectively. The electrodes showed good selectivity to EfCl with respect to many inorganic cations, sugars and amino acids. The standard additions method was used to determine EfCl in pure solutions and in pharmaceutical preparations.     

Ion-selective electrodes for determination of phenylalanine based on uranyl complexes of phosphoryl-containing podands

The possibility of phenylalanine determination using membrane ion-selective electrodes based on uranyl complexes with phosphoryl-containing podands was shown. The variation of the procedure of membrane preparation (either entrapping the preliminarily synthesized uranyl-podand complex in the membrane phase or conditioning of the podand-containing membrane in the uranyl solution) was found to have practically no effect on the electrode properties. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1729–1732, October, 2000.     

Study on Hydrogen Ion-Selective Solid Contact Electrodes Based on Decamethylcyclopentasiloxane

Hydrogen ion-selective solid contact electrode based on decamethylcyclopentasiloxane (DMCS) as ionophore was fabricated. The membrane solution was prepared by mixing DMCS, polyvinyl chloride (PVC), potassium tetrakis p-chlorophenyl borate (KTpClPB) and various plasticizers. The best performance was obtained with the sensor based on NPOE (o-nitrophenyl octyl ether) and the conducting polymer layer of poly(pyrrole), doped with NaClO₄. The electrode exhibited Nernstian-response in the range of pH 1.9–9.8 with a slope of 57.6 ± 0.2 mV per decade and fast response time within 15 s. This electrode showed good selectivity and was successfully used as an indicator electrode in the potentiometric titration.     

New Macrocyclic Diamides as Neutral Ionophores for Highly Selective and Sensitive PVC‐Membrane Electrodes for Be2+ Ion

Five recently synthesized macrocyclic diamides were investigated to characterize their ability as beryllium ion carriers in potentiometric PVC‐membrane electrodes. The electrodes based on 1,15‐diaza‐3,4;12,13‐dibenzo‐5,8,11‐trioxabicyclo[13,2,2] heptadecane‐2,14‐dione exhibited a Nernstian response for Be²⁺ ion over wide concentration ranges (from 3.0×10^?6 to 3.0×10^?2 M for polymeric membrane electrode, PME, and from 5.0×10^?7 to 2.0×10^?2 M for coated glassy carbon electrode, CGCE) and very low detection limits (2.0 ×10^?6 M for PME and 4.0×10^?7 M for (CGCE). The electrodes possess low resistances, fast responses, satisfactory reproducibilities and, most importantly, good selectivities relative to a variety of other common cations. The potentiometric response of the electrodes is independent of pH of test solution in the pH range of 4.0–7.5. The proposed sensors were used to determine beryllium ion in water samples.     

Sodium Ion Selective Electrodes Based on Lipophilic 16-Crown-5 Derivatives

Abstract

Six kinds of lipopholic 16-crown-5 derivatives possessing double side-chains were synthesized. The Na⁺-selectivities were examined with poly(vinyl chloride) (PVC) matrix-membrane electrodes using these crown compounds. It is an effective way for obtaining high Na⁺-selectivity by introducing a bulky side-chain such as a benzyloxymethyl group into the 16-crown-5. The electrodes based on 16-crown-5 derivatives having both a methyl or ethyl group and a benzyloxymethyl group at the pivot carbon (C-15) (3 or 4, see Figure 1) exhibited excellent Na⁺-selectivity over K⁺ (log k _Na.x = -2.65 and -2.75 for 3 and 4, respectively).     

Ionic Liquid Solvent Based on Cyclic Guanidinium Cation for Nucleophilic Displacement Reactions

The nucleophilic displacement reaction of n-bromooctane and potassium iodide in ionic liquid based on cyclic guanidinium cation(2) was investigated. The kinetic reasuh shows that the rate of the reaction is enhanced in ionic liquid (2). The same reaction in [bmim][PF6] (1)(where bmim=1-butyl-3-methylimidazolium) was also studied. It was found that as a reaction medium ionic liquid (2) is better than (1) for nucelophilic displacement reactions.     

Nitrogen-Bearing Organic Compounds as Carriers for Lead Ion-Selective Electrodes with Excellent Response

Bis-Schiff base, pyridyl carboxamide, acylhydroxylamine, and phenylhydrazone, acting as sensing agents in ionophore-doped membranes of lead-ion selective electrodes with excellent response characteristics, are systematically summarized according to the latest literatures and our latest researches. The relationship between the response characteristics of the lead (II) ion-selective electrode assembled by the carriers and their molecular structures is also elaborated. It is noteworthy that the selectivity of the electrode towards lead ions over other cations is closely related to the molecular structure of the carrier. The presence of cyano group would largely improve the lower detection limit whether it is introduced into the carrier or membrane matrix. The sensing mechanism should be emphasized in order to find out the direction for developing high performance carriers.     

Synthetic Ionophores. Part 17. Synthesis of Ether-Amine-Amide Based m-Cyclophanes: A Search for Pb2+ Selective Ionophores

m-Cyclophanes 3, 4, and 5 possessing two ether oxygen, two amide, one NH and a -system, an optimal combination of ligating sites for selective Pb²⁺ binding, have been synthesized by condensations of diethylenetriamine, 3,3-diaminodipropylamine and 1,3-diaminopropane with 1,3-bis(ethoxycarbonylmethoxy) benzene (6) formed by the PTC reaction of resorcinol and ethyl chloroacetate. Ionophores 3-5 induced cation extraction/transport could not be studied due to their insolubility in CHCl₃/CH₂Cl₂ and solubility in water, but ¹³CNMR titrations of 4 with metal ions point to its binding preferences for Ag⁺ and Pb²⁺ over alkali/alkaline earth cations.