New Copper(II) Ion-Selective Membrane Electrode Based on Erythromycin Ethyl Succinate as a Neutral Ionophore

Abstract

The potentiometric response characteristics of a new copper(II) ion-selective PVC membrane electrode based on erythromycin ethyl succinate (EES) as ionophore were investigated. The electrode exhibited a Nernstian response to Cu²⁺ ions over the activity range of 1.5 × 10^?2 to 2.0 × 10^?6 mol L^?1 with a limit of detection of 6.3 × 10^?7 mol L^?1. Stable potentials were obtained in the pH range of 5.5–6.5. The potentiometric selectivity coefficients were calculated by using fixed interference method and revealed no important interferences except for Ag⁺. This electrode was successfully applied as an indicator electrode in determination of copper ions in real water samples.     

苯乙烯三嗪衍生物的合成及在重金属离子识别中的应用

合成了2,4-二(2-噻吩乙烯基)-6-(4'-N,N-二甲氨基苯乙烯基)-1,3,5-均三嗪(2)并鉴定了其结构。在乙腈-水混合介质中,化合物2在355和416nm处呈现双吸收峰,加入Cu²⁺,Hg²⁺ 和Fe³⁺ 后,均在520nm附近形成新的吸收峰。化合物2与Cu²⁺、Hg²⁺ 和Fe³⁺ 均形成1:1型配合物,其结合常数分别为1.9×10⁵L·mol^-1,6.6×10³L·mol^-1,2.7×10³L·mol^-1。对照化合物4与金属离子的光谱响应与化合物2相似,仅吸收峰的位置不同。因此,可认为化合物2和4中三嗪环中的N和噻吩环中的S与Cu²⁺、Hg²⁺ 和Fe³⁺ 共同配位形成了稳定的金属配合物。     

A new lawsone azo-dye for optical sensing of Fe3+ and Cu2+ and their DFT study

A new lawsone-based azo-dye 2-hydroxy-3-((pyridin-2-ylmethyl)diazenyl)naphthalene-1,4-dione (1) was synthesized and applied for sensing of metal ions. Receptor 1 showed selective fluorescent and colorimetric response for the detection of Cu²⁺ and Fe³⁺ over other tested metal ions. The fluorescence intensity of 1 was significantly quenched allowing detection of Fe³⁺ and Cu²⁺ down to 0.61 and 6.06 μM, respectively. The binding has been established by fluorescence spectroscopic method. Receptor 1 provided a 1?:?1 binding scaffold for recognition of Fe³⁺ and Cu²⁺ ions with the association constant of 3.33 × 10⁶ and 3.33 × 10⁵ M^?1, respectively. The B3LYP/6-31G/LANL2DZ method was employed for the optimization of 1 and 1·Fe³⁺ and 1·Cu²⁺.     

Highly sensitive and selective determination of Hg2+ by using 3-((2-(1H-benzo[d]imidazol-2-yl)phenylimino)methyl)benzene-1,2-diol as fluorescent chemosensor and its application in real water sample

A new receptor 3-((2-(1H-benzo[d]imidazol-2-yl)phenylimino)methyl)benzene-1,2-diol (1) was synthesised and developed as a highly selective fluorescent chemosensor for the detection of Hg²⁺ in semi-aqueous media. The fluorescence of receptor 1 was dramatically and selectively quenched on complexation with Hg²⁺ ion with the detection limit down to 0.20 μM. The developed sensor was successfully applied for the determination of Hg²⁺ content in water samples. Density Functional Theory (DFT) calculations were performed to study the mechanistic behaviour behind the binding of Hg²⁺ with receptor 1.     

13C, 15N and 113Cd NMR and Molecular Orbital Studies of Novel Bile Acid N-(2-aminoethyl)amides and Their Cd2+-complexes

Lithocholic acid N-(2-aminoethyl)amide (1) and deoxycholic acid N-(2-aminoethyl)amide(2) have been prepared and characterized by¹H, ¹³C and ¹⁵N NMR. The accurate molecular masses of 1 and 2 have been determined by ESI MS. The formation of the Cd²⁺-complexes (1+Cd and 2+Cd) in CD₃OD solution have been detected by ¹H,¹³C, ¹⁵N and ¹¹³Cd NMR. The ¹³C NMR chemical shift assignments of 1 and 2 and their Cd²⁺-complexes are based on DEPT-135 and z-GS ¹H,¹³C HMQC experiments as well as comparison with the assignments of the related structures. The ¹⁵N NMR chemical shiftassignments of the ligands and theirCd²⁺-complexes are based on z-GS¹H,¹⁵N HMBC experiments. ¹³C NMR chemical shift differences between 1and its 1:1 Cd²⁺-complex based on ab initiocalculations at Hartree-Fock SCI-PCM level using3-21G(d) basis set are in agreement with theexperimental shift changes observed onCd²⁺-complexation.     

Copper Incorporated [Me2(15)dieneN4] Macrocyclic Complex for Fabrication of PVC based Membrane Electrode for Copper

Copper (II) complex of 2,4-dimethyl-1,5,9,12-tetraazacyclopentadeca-1,4-diene, [Me₂(15)dieneN₄] was synthesized and used in the fabrication of Cu²⁺ – selective ISE membrane in PVC matrix. The membrane having Cu(II) macrocyclic complex as electroactive material along with sodium tetraphenyl borate (NaTPB) as anion discriminator. Dibutyl phthalate (DBP) as plasticizer in poly(vinyl chloride) (PVC) matrix was prepared for the determination of Cu²⁺. The best performance was observed by the membrane having Cu(II) complex–PVC–NaTPB–DBP with composition 1:5:1:3. The sensor worked well over a concentration range 1.12 × 10⁻⁶ M–1.0 × 10⁻¹ M between pH 2.1–6.2 and a fast response time 10±2 s and a lifetime of 6 months. Their performance in partially non-aqueous medium was found satisfactory. Electrodes exhibited excellent selectivity for Cu²⁺ ion over other mono-, di-, trivalent cations. It can also be used as indicator electrode in the potentiometric titration of Cu²⁺ against EDTA as well as in the determination of Cu²⁺ in real samples.     

Determination of ferrous and ferric iron in aqueous biological solutions

A solvent extraction method was employed to determine ferrous and ferric iron in aqueous samples. Fe³⁺ is selectively extracted into the organic phase (n-heptane) using HDEHP (bis(2-ethylhexyl) hydrogen phosphate) and is then stripped using a strong acid. After separation, both oxidation states and the total iron content were determined directly by ICP-MS analysis. This extraction method was refined to allow determination of both iron oxidation states in the presence of strong complexing ligands, such as citrate, NTA and EDTA. The accuracy of the method was verified by crosschecking using a refinement of the ferrozine assay. Presented results demonstrate the ability of the extraction method to work in a microbiological system in the presence of strong chelating agents following the bioreduction of Fe³⁺ by the Shewanella alga BrY. Based on the results we report, a robust approach was defined to separately analyze Fe³⁺ and Fe²⁺ under a wide range of potential scenarios in subsurface environments where radionuclide/metal contamination may coexist with strongly complexing organic contaminants.     

Complexing tendencies of UO 22+ and Th4+ in their mixed ligand complexes with aminopolycarboxylates and resorcinol or its derivatives

Formation contants (log K _MAL ^MA ) of mixed ligand complexes MAL, where M = UO ₂ ²⁺ or Th⁴⁺, A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, and L = resorcinol (res), 2-methyl resorcinol (2-Me-res), 5-methyl resorcinol (5-Me-res) or 4-chloro resorcinol (4-Cl-res), have been determined pH-metrically by the Irving-Rossotti approach at 25°C and at an ionic strength,I = 0.2(moldm⁻³KNO₃). The observed stability sequences are IMDA > NTA > HEDTA > EDTA > CDTA > DTPA, and 4-Cl-res > 5-Me-res > 2-Me-res > res with respect to primary and secondary ligands, respectively. Th⁴⁺ forms more stable mixed complexes than UO ₂ ²⁺ . The A ΔlogK values are negative due mainly to the charge repulsion involved in the complexation MA + L⇋MAL.     

A multichannel thiacalix[4]arene-based fluorescent chemosensor for Zn2+, F− ions and imaging of living cells

Abstract

The fluorescent sensor (3) based on the 1,3-alternate conformation of the thiacalix[4]arene bearing the coumarin fluorophore, appended via an imino group, has been synthesised. Sensing properties were evaluated in terms of a colorimetric and fluorescence sensor for Zn²⁺ and F^?. High selectivity and excellent sensitivity were exhibited, and ‘off-on’ optical behaviour in different media was observed. All changes were visible to the naked eye, whilst the presence of the Zn²⁺ and F^? induces fluorescence enhancement and the formation of a 1:1 complex with 3. In addition, 3 exhibits low cytotoxicity and good cell permeability and can readily be employed for assessing the change of intracellular levels of Zn²⁺ and F^?.     

Cobalt(II)-selective membrane sensor based on a [Me2(13)dieneN4] macrocyclic cobalt complex

A new poly(vinyl chloride)-based membrane was fabricated with the cobalt(II) complex of 2,4-dimethyl-1,5,8,11-tetraazacyclotrideca-1,4-diene [Me₂(13)dieneN₄] as an ion carrier. The membrane composition was Co²⁺ complex/PVC/NaTPB/DBP 15:50:15:20 (w/w). The sensor exhibited a Nernstian response for Co²⁺ ions over a wide concentration range (7.94×10⁻⁶–1.0×10⁻¹ M) at pH 2.5–7.0, a response time of 10 s, and it could be used for 3 months without any significant divergence in potential. The proposed membrane sensor exhibited good selectivity for Co²⁺ over a wide variety of other metal ions and in mixtures containing up to 25% (v/v) non-aqueous content. The sensor was successfully used as an indicator electrode in the potentiometric titration of Co²⁺ with EDTA and the direct determination of Co²⁺ in real samples.     

A biacylhydrazone-based chemosensor for fluorescence ‘turn-on’ detection of Al3+ with high selectivity and sensitivity

A simple Al³⁺ fluorescent chemosensor (1) based on diacylhydrazone has been designed and synthesized by the condensation reaction of 2-hydroxy naphthaldehyde and metaphthalic hydrazide. The chemosensor 1 displays a specific and sensitive response to Al³⁺ over other cations in DMSO solution. Upon the addition of DMSO solution of Al³⁺, the sensor 1 shows an immediate fluorescence ‘turn-on’ response and emitting strong blue emission with visible color change from colorless to green. The fluorescence quantum yield enhanced from 7.24% to 48.68%. Meanwhile, the fluorescence and UV absorption spectra detection limits of the chemosensor 1 for Al³⁺ were 2.0 × 10^?7 M and 5.6 × 10^?7 M respectively, indicating the high sensitivity of 1 to Al³⁺. Furthermore, test strips based on 1 were fabricated, which could be used as a convenient test kit for the detection of Al³⁺ and an efficient Al³⁺ controlled fluorescent security display materials.     

Naphthalene and pyrrole substituted guanidine in selective sensing of Cu2+, Hg2+, Pb2+ and CN− ions under different conditions

Naphthalene and pyrrole substituted guanidine 1 has been designed and synthesised. Compound 1 efficiently distinguishes Cu²⁺, Hg²⁺ and Pb²⁺ ions by exhibiting different responses in fluorescence. While compound 1 exhibited turn-on emission selectively in the presence of Hg²⁺ and Pb²⁺ ions in CH₃CN and CH₃CN–H₂O (1:1, v/v), respectively, it showed decrease in emission upon interaction with Cu²⁺ ion in CH₃CN. Furthermore, the Cu-1 ensemble has been established as a potential probe for selective detection of CN^? ion over a series of other anions involving colour change (in ordinary light: colourless to light yellow and under UV light: colourless to sky blue). Theoretical insight has been invoked to understand the mode of metal–ligand interaction.     

Novel potentiometric sensor for the trace-level determination of Zn2+ based on a new nanographene/ion imprinted polymer composite

In this research, a new strategy for construction of a development potentiometric carbon paste Zn²⁺-ion selective electrode based on a novel nano-sensing layer is suggested. The proposed nano-sensing layer was prepared with the addition of a synthesised Zn²⁺-ion imprinted polymer nanoparticles ‘as an efficient sensing agent’ into the carbon paste matrix consisting of graphite powder, nanographene-composite ‘graphene nanosheets decorated with silver nanoparticles’ and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ‘ an ionic liquid ’, as the conducting binder. Under the optimised experimental conditions, the suggested nanographene-composite potentiometric sensor presented a low detection limit of 1.93 × 10^?1 μg L^?1 and a linear analytical range from 2.62 × 10^?1 to 6.54 × 10⁵ μg L^?1 with an excellent Nernstian slope of 29.80 mV decade^?1. The proposed zinc selective sensor was successfully applied for the highly sensitive determination of trace amounts of Zn²⁺ in environmental and biological samples with satisfactory results.     

Perimedine-linked rhodamine dye in visual sensing of Al3+, Fe3+ and Fe2+ ions in aqueous organic medium under different experimental conditions

ABSTRACT

Perimedine labelled rhodamine dye 1 has been designed and synthesised. Metal ion binding studies of 1 have been performed in CH₃CN/H₂O (3:1, v/v, 10 mM Tris-HCl buffer, pH = 6.90). Compound 1 senses multiple metal ions such as Al³⁺, Fe³⁺ and Fe²⁺ by exhibiting turn on fluorescence and colour change (colourless to pink) under different experimental conditions. Concentration variation distinguishes Al³⁺ from Fe³⁺ ion. At low concentration (c = 1 x 10^?4 M), only Al³⁺ ion can exhibit turn on fluorescence with sharp colour change. Sensing of Fe²⁺ ion through turn on fluorescence and colour change has been possible via in situ oxidation by following Fenton’s reaction.     

Electrochemical Determination of Copper(II) in Water Samples Using a Novel Ion-Selective Electrode Based on a Graphite Oxide–Imprinted Polymer Composite

A novel copper(II)-selective electrode based on graphite oxide/imprinted polymer composite was developed for the electrochemical monitoring of copper(II) (Cu²⁺) ions. The electrode exhibited highly selective potentiometric response to Cu²⁺ with respect to common alkaline, alkaline earth and heavy metal cations. The composite composition studies indicated that the most suitable composite composition performing the most promising potentiometric properties was 20.0% ionophore (Cu²⁺-ion imprinted polymer), 10.0% paraffin oil, 5.0% multiwalled carbon nanotubes, and 65.0% graphite oxide. The fabricated electrode exhibited a linear response to Cu²⁺ over the concentration range of 1.0?×?10^??6–1.0?×?10^??1?M (correlation coefficient of 0.9998) with a sensitivity of 26.1?±?0.9?mV decade^??1. The detection limit of the fabricated electrode was determined to be 4.0?×?10^??7?M. The electrode worked well in the pH range of 4.0–8.0. The electrode had stable, reversible and fast potentiometric response (3?s). In addition, the electrode had a lifetime of more than 1 year. The analytical applications of the proposed electrode were performed using as an indicator electrode for the potentiometric titration of Cu²⁺ with ethylene diamine tetraacetic acid solution and for the determination of Cu²⁺ of spiked river, dam, and tap water samples. The obtained results for potentiometric titration and water samples were satisfactory.     

Excellent Ag+ selective receptors: Syntheses and complexation properties of novel biscalix[4]arene with benzalazine groups

By reacting mono-substituted or 1,3-bi-substituted [2-(p-formylphenyloxy)ethyloxy]-p-tert-butylcalix[4]arene (3 or 4) with hydrazine hydrate in ‘1+2’ or ‘2+2’ condensation mode, novel benzalazine-bridging biscalix[4]arenes 5 and 7 were conveniently obtained in the yields of 76 and 81%, respectively. Condensation of compound 4 and salicylide hydrazone gave a novel calix[4]arene benzalazine derivative 6 in the yield of 85%. The structures and conformations of all new compounds were characterised by elemental analyses, ESI-MS, ¹H NMR and ¹H–¹H COSY techniques. Biscalix[4]arene 7 adopts a symmetrical cone conformation with tube cavity. The liquid–liquid extraction experiment showed that all new hosts possessed excellent complexation abilities towards soft metal cations. Compound 7 exhibited high complexation selectivity towards Ag⁺. The Ag⁺/Na⁺ and Ag⁺/Hg²⁺ extraction percentages of host 7 were as high as 73.1 and 54.9, respectively. The UV–vis spectra complexation experiments revealed that the complexation constant of receptor 7 with Ag⁺ was 1.9 × 10⁵ M^? 1 and the 1:1 stoichiometry of receptor 7–Ag⁺ complex was formed. The ¹H NMR spectra complexation experiments suggested that Ag⁺ was bound in a cavity composed of two benzalazine groups on bridging chains.     

A novel turn-on fluorescent probe for Hg2+ detection based on rhodamine B spirolactam derivative

ABSTRACT

In this work, a new turn-on fluorescent probe 1 for Hg²⁺ ions detection based on rhodamine B spirolactam was reported. Among tested metal ions, probe 1 shows high selectivity towards Hg²⁺ in the the mixture solution of methanol and 0.02 M HEPES buffer (V/V = 9:1, pH = 7.2). No absorption and emission band of probe 1 was observed in the range from 450 to 700 nm. While only addition of Hg²⁺ to probe 1 could lead to appearance of a new absorption band centered at 553 nm and a fluorescence emission band around 577 nm upon excitation at 520 nm. Moreover, it exhibits excellent linear relationship (R² = 0.9993) between fluorescence intensity at 577 nm and the concentration of Hg²⁺ from 1.6 to 32 μM. The sensing mechanism was proven to be spirolactam ring open induced by Hg²⁺ through ¹H NMR, MS, absorption and fluorescence spectra. In addition, probe 1 could detect Hg²⁺ in real water samples and on filter paper, which demonstrates its application in environment science.     

Study on Metronidazole Acid-Base Behavior and Speciation with Ca2+ for Potential Applications in Natural Waters

Metronidazole (MNZ) is an antibiotic widely used for the treatment of various infectious diseases and as an effective pesticide agent for the cultivation of chickens and fish. Its high resistance to purification processes and biological activity has led to the classification of MNZ as an emerging contaminant. A speciation study, aimed to define the acid-base properties of MNZ and its interaction with Ca²⁺, commonly present in natural waters, is reported. The protonation constants of MNZ, as well as the formation constant value of Ca²⁺-MNZ species, were obtained by potentiometric titrations in an aqueous solution, using NaCl as background salt at different ionic strengths (0.15, 0.5, 1 mol L⁻¹) and temperature (15, 25 and 37 °C) conditions. The acid-base behavior and the complexation with Ca²⁺ were also investigated by ¹H NMR and UV-Vis titrations, with results in very good agreement with the potentiometric ones. The dependence of the formation constants on the ionic strength and temperature was also determined. The sequestering ability of MNZ towards Ca²⁺ was defined by the empirical parameter pL_0.5 at different pH and temperature values. The speciation of MNZ simulating sea water conditions was calculated.     

Metal Chelates of Cerium (III), Thorium(IV) and Dioxouranium(VI) with Some Heterocyclic AZO Dyes; Potentiometric and Spectrophotometric Studies

ABSTRACT

The stepwise formation constants of Ce³⁺, Th⁴⁺ and UO₂ ²⁺ complexes with four azo compounds based on I-phenyl-2, 3-dimethylpyrazoline-5-one nucleus namely; 4-phenylazo- (2-hydroxy, 5-x) 1-pheny1-2, 3-dimethy1-pyrazoline-5-one, where x= H (1), OH (II), COOH (III) and NH₂ (IV) have been determined potentiometrically at different temperatures and ionic strengths in 30% (v/v) ethanol-water solutions, then the thermodynamic parameters are calculated.

Negatives values of both ∠H and ∠G are obtained indicating the exothermic and spontaneous nature of complexation reactions, whereas positive values of ∠S show that entropy consideration favour complex formation. The study at different ionic strengths shows that an increase in the latter causes a decrese in the pK values. The azo compounds are also tested as new reagents for the spectrophotometric determination of Ce³⁺, Th4⁺ and UO₂ ²⁺ ions in synthetic and natural solutions by extensive investigation of the optimum conditions favoring the formation of colored complexes.     

Supramolecular chemosensor for selective detection of iron in aqueous medium

We have successfully developed a ‘turn-on’ colorimetric chemosensor for Fe³⁺ based on 1,10-phenanthroline. An amide derivative of 1,10-phenanthroline 4 was developed for the selective recognition of Fe³⁺ over Co²⁺, Cr³⁺, Cu²⁺, Mn²⁺, Ni²⁺, Ag⁺ and Zn²⁺ and could measure Fe³⁺ concentration in the range of 15–210 μM by UV–vis spectroscopy. Moreover, the addition of Fe³⁺ to a colourless solution of 4 turned its colour to light pink, indicating that 4 is capable of detecting Fe³⁺ by the naked eye. Compound 4 exhibits a major absorption band centred at 268 which shifted to 278 nm after addition of Fe³⁺, and a shoulder band around 514 nm was also observed. The complexation of Fe³⁺ with 4 was analysed at a different pH and favourable binding was observed at pH 6.2.