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Multi-walled carbon nanotube (MWCNT)-grafted 2, 6-bis[2-(amino methyl)phenol]pyridine (BAPP) synthetic ligands were effectively used as novel ion carriers in the structure of carbon paste electrodes (CPEs) for simultaneous trace-level assessment of Hg(II) and Cu(II) by potentiometry. Utilising pyridine-based Cu(II) and Hg(II) complexing agents and MWCNTs as signal boosters has reasonably eventuated in an acceptable sensitivity and selectivity over Cu(II) and Hg(II) target ions in the presence of some interfering species. The working linear range, limit of detection, and Nernstian slope of the sensor were recorded as follows, respectively, Hg(II): 4.0 × 10−9 to 3.0 × 10−4 mol L−1, 2.0 × 10−9 mol L−1 and 43.2 (±0.4) mVdecade‒1 (n = 5) and Cu(II): 4.0 × 10−9 to 2.2 × 10−2 mol L−1, 7.9 × 10−10 mol L−1 and 29.8 (±0.5) mVdecade‒1 (n = 5). The working pH range of 3.0‒4.5 and 4.0‒7.0 and dynamic response time of 7.0 s and 5.0 s were evaluated for the Hg(II) and Cu(II) sensors, respectively. The modified sensors also displayed an acceptable reproducibility, response repeatability and useful lifetime over around 45 days. Eventually, the practical utility of the chemically modified sensors was confirmed by trace-level potentiometric monitoring of mercury and copper ion quantities in some environmental, industrial and biological aqueous samples. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of copaiba oleoresin (CO) as a substitute for sodium lasalocid on the carcass characteristics and meat quality of feedlot lambs fed a high-concentrate diet. Twenty-four Pantaneiro lambs, aged 152 days and weighing an initial body weight of 21.2 ± 3.9 kg, were distributed in a randomised block design with three treatments and eight replications. The treatments correspond to the additive supplements: LAS (22.5 mg of sodium lasalocid/kg of diet); CO-0.5 (0.5 mL of CO/animal/day); CO-1.0 (1.0 mL of CO/animal/day). The doses of CO were administered to the animals orally with the aid of a graduated syringe. Lambs supplemented with LAS had higher hot carcass weight, cold carcass weight, cold carcass yield, and degree of fattening compared to CO-0.5, while CO-1.0 did not differ from LAS. It can be concluded that daily ingestion of CO up to 1.0 mL/lamb did not negatively affect carcass characteristics when compared to LAS supplementation. However, lower ingestion (0.5 mL/day) can reduce the carcass weight and carcass yield. Although CO supplementation minimally affected the meat quality and FA profiles, both doses reduced crude protein content in meat. [ABSTRACT FROM AUTHOR]

In this study, a series of new chelating copolymers containing 20% azomethine groups, poly(N-vinylpyrrolidone-co-vinylsalicylideneimine) (poly[VP-co-VSalI]), poly(N-vinylpyrrolidone-co-vinylpicolinideneimine) (poly[VP-co-VPicI]), poly(N-vinylpyrrolidone-co-vinylpyridoxylideneimine) (poly[VP-co-VPyrI]) with M = 63000 Da and their vanadium(IV) complexes – poly(VP-co-VSalI)-VO, poly(VP-co-VPicI)-VO, poly(VP-co-VPyrI)-VO, were designed and synthesized. These are intended for the delivery and pH-dependent release of vanadium species in the intestine environment. The chelating polymers were obtained from poly(N-vinylpyrrolidone-co-N-vinylamine) (poly[VP-VAm]) by polymer-analogous transformations with the corresponding aldehydes. The vanadium content, determined by ICP-AES and spectrophotometric methods, was 5.36%, 4.99%, and 9.1% of the dry mass for poly(VP-co-VSalI)-VO, poly(VP-co-VPyrI)-VO, and poly(VP-co-VPicI)-VO, respectively. XPS data confirmed that only vanadium(IV) is presented in the complexes. All complexes demonstrated a pH-dependent release of low molecular weight vanadium species, making them promising candidates for the development of vanadium-containing systems for oral administration. These systems protect the main vanadium content in the stomach but can release biologically active ions in the intestine. [ABSTRACT FROM AUTHOR]

Depending upon charge and chemical affinity, interplay between resistances of membrane (Rmem) and membrane–solution interface (Rmem) may lead to preferential transport of an ion. Here, intermittent in-situ electrochemical impedance spectroscopy (EIS) was done during electrodriven transport (radiotracer based) to analyze the transport selectivity of Cs+ over Na+ in different membranes. Preference of the membranes for Cs+ was reflected in the time-dependent Nyquist plots itself. Bode plot analysis also indicated dominant Cs+ transport in terms of phase and frequency shift in crown ether (DB21C7) based membrane. In Cs+ selective polymer incluion membranes, irrespective of carrier, Rmem contributed majorly to overall resistance. However, time dependence of Rmem/Rmem was carrier as well as ion dependent. Interestingly, for nonselective ionic carrier, Rmem/Rmem was majorly close to 1 and a reverese transport order than previous membranes were obtained. A higher Na+ transport (than Cs+ ) was also obtained for DB21C7 loaded Nafion, where, due to ion templating effect, Rmem was the governing factor. EIS spectral nature of a mixed feed solution follows that of the most preferred ion, thus suggesting that EIS can be used to study prospective real-life systems and can be used as a significant tool in designing ion-selective membranes. [ABSTRACT FROM AUTHOR]

The co-precipitation technique is frequently employed for the separation and enrichment of trace elements. The aim of this technique is to separate the analytes from the matrix with the help of the precipitating ion and the carrier ion without the need for a solid phase and/or liquid phase solvent. A separation-preconcentration method based on the co-precipitation of ziram (zinc bis (dimethyldithiocarbamate) in vegetable samples using magnesium hydroxide was developed prior to its indirect determination by flame atomic absorption spectrometry (FAAS). Zinc levels in ziram were determined by FAAS. The ziram concentration was calculated using the stoichiometric relationship between zinc and ziram. The analytical parameters including hydroxide ion concentration, Mg (II) as the carrier element, and model solution volumes were optimized. In addition, possible interferences were investigated. The preconcentration factor was calculated to be 60. The limit of detection (LOD) and relative standard deviation were 35 μg L−1 and 3.9%. The presented method was successfully applied to the analysis of water and vegetable samples. [ABSTRACT FROM AUTHOR]

Solid-state Pb(II) ion selective electrodes were developed, which are based on 3,3-disubstituted 1-acylthioureas as ionophores and use PVC membranes. 1-Benzoyl, 1-(2-furoyl), 3,3-diethyl and 3,3-diphenyl were the substituent groups on the thioureide core. The analytical parameters for the constructed electrodes were studied. The electrodes based on 3,3-diethyl substituted thiourea derivatives showed better analytical response to Pb(II) ions with suitable sensitivity and an average lifetime of more than 30 days. Cu(II), Hg(II) and Ag(I) ions were interfering species during Pb(II) detection. Scanning electron microscopy and atomic force microscopy micrographs of the activated sensing membranes revealed morphological changes, which have been associated with the performance of the sensors. The studies have suggested that the detection of few large size particles or aggregates at the membrane surface are responsible for inadequate functioning of the prepared electrodes. This pattern was mainly observed for the sensing membranes based on 3,3-diphenyl groups as substituents and is related to unfavorable steric and electronic factors. Furthermore, X-ray photoelectron spectroscopy profiles S2p and Pb4f supported chemically the analytical response displayed for the four membrane systems. The X-ray photoelectron spectroscopy results combined with scanning electron microscopy and atomic force microscopy studies shed light on the working mechanism of the studied electrodes. [ABSTRACT FROM AUTHOR]

In today's world, increasing technological demand and decreasing tenor of cobalt on the earth make the selective extraction and the recycling of cobalt processes indispensable. The study is to highlight both experimental optimization and artificial neural network (ANN) modeling of cobalt separation and transport performances through PVC-based ionic polymer inclusion membrane (IPIM) considering different molecular structure room temperature ionic liquids (RTILs) derivatives as an ion carrier. Some sophisticated investigations on PVC-based IPIMs have been done by changing membrane compositions. Also, the membranes were characterized in different aspects and techniques like SEM-EDX, AFM, contact angle measurement, etc. In optimum conditions, the initial mass transfer coefficient (Ji) of cobalt was found about 2,44x10−6 mols−1m−2 by the longest alkyl chain substituted ionic liquid (RTIL4) and also found that the selectivity of the process was found very well for cobalt in the presence of the other metal ions, especially toward nickel and cadmium. ANN modeling has been performed on the effective parameter analysis that was performed on the experimental results. As a result of ANN analysis, the most effective parameters were determined as RTIL type and operation time have higher modeling sensitivity. The promising results show experimentally optimized and ANN modeled process has a cost-effective, environmentally-friendly potential for cobalt separation and transport. Room temperature ionic liquids having different molecular structures in polymer inclusion membranes (PIMs) were effectively used for cobalt transport and separation. The process has considerable durability and reusability for long-term operations both cobalt separation and cobalt transport. A good coherence between experimental results and artificial neural networks (ANN) modeling was observed to create two-dimensional transport and separation effectiveness of cobalt. The best effective parameters on the cobalt transport and separation were found as RTIL type and operating time according to ANN modeling. [ABSTRACT FROM AUTHOR]

Tetracyclines and polyether ionophores are veterinary drugs frequently used in animals reared for food production. Despite the benefits, residues can be harmful for human health if levels are higher than those considered safe. The aim of this study was to evaluate, by LC-MS/MS, tetracyclines residues in pasteurised milk samples marketed in São Paulo state, Brazil and estimate the exposure of the adult/adolescent/children population. Within the eight antibiotics monitored two were detected, tetracycline and 4-epitetracycline, found in 22.5% and 12.5% of the samples, respectively. Since the same samples had been previously tested for polyether ionophore residues, risk assessment based on dietary exposure to tetracyclines when considered individually and in combination with the ionophores was performed. The daily intakes were below the acceptable daily intake (ADI) for tetracycline. Considering the levels of monensin reported in a previous study, the combined exposure with tetracycline and 4-epi-tetracycline also indicated low potential health concerns. [ABSTRACT FROM AUTHOR]

Solid-state Pb2+-ion selective electrodes (Pb2+-ISEs) based on liquid membranes using three 1-aroyl-3,3-dimethylthioureas as ionophores were developed. The receptors differ structurally in the aromatic ring of the 1-aroyl group and have been labeled as FDM, BDM, and TDM. The analytical performance of the constructed electrodes was studied by determining the calibration parameters. The electrodes showed Nernstian behavior with average sensitivities of 30.1, 31.5 and 26.6 mV/dec, as well as average lifetimes of 100, 60 and 7 days, respectively. Cd2+ and Cu2+ cations were interfering toward Pb2+ ions detection. The sensing membranes were studied by SEM-EDS and the results have suggested the formation of aggregates through time related to complex species Pb2+-aroylthioureas. Additionally, quantum chemical calculations were carried out at the B3LYP/6-311G(d,p) level of theory to compute the geometry, frontier molecular orbital energies and global reactivity parameters of the aroylthioureas in tributyl phosphate (TBP) as solvent mediator. Correlation studies between the receptor's quantum chemical parameters and the experimental analytical response of the Pb2+-ISEs were addressed in order to clarify the differences observed in the analytical response of the constructed electrodes. The results support the chemical model of interaction between thioureas and Pb2+ ions through orbital control involving vacant d-orbitals of the metal ion and electrons from the HOMO of the organic molecule. [ABSTRACT FROM AUTHOR]

Ionophore coccidiostats are widely used in the UK broiler sector at present but their future use has been questioned. A review of published and technical literature has been undertaken to assess the likely impacts of removing ionophore coccidiostats from UK broiler production. Expert opinion from two poultry veterinarians has been used to establish the probable approach and interventions that would be needed in a 'no-ionophore' programme and the likely impacts. Comparisons have been made between 'standard' and 'no-ionophore' programmes, covering farm production costs and environmental impacts. Key performance assumptions for the 'no-ionophore' programme include one extra day of growing time to achieve target average liveweight of 2.26 kg and a five point increase in feed conversion ratio (FCR) from 1.58 to 1.63. Any increase in mortality is considered marginal if other interventions are adopted and therefore this study has assumed no differences. Veterinary opinion considers that a reduction in stocking density of 4 kg of liveweight per square metre would be needed to maintain good health in a 'no-ionophore' programme; a 2-day increase in house turnaround time between flocks is also recommended. Changes to feed specifications would be expected, together with the use of a coccidiosis vaccine. Based on stated assumptions, farm production costs are calculated to be 5.7% higher for the 'no-ionophore' programme than a standard programme. Optimistic and pessimistic scenarios indicate cost increases ranging between 3.3% and 10.8%. The 'no-ionophore' programme was also found to result in a 3.9% increase in greenhouse gas emissions per bird and to require 3.3% more land to grow crops for poultry feed. Increased production cycle length and reduced stocking density in the 'no-ionophore' programme would mean that a 19% increase in UK broiler growing space is required, to maintain current chicken meat output levels. [ABSTRACT FROM AUTHOR]

Roseophilin is an alkaloid structurally related to prodiginines. The intriguing pharmacological properties of these derivatives have prompted us to prepare synthetic compounds 1–3 inspired by their structure and to explore their transmembrane anion transport activity. The methoxyfuran heterocycle impacts the anionophoric activity of the compounds as a result of the reduced hydrogen-bonding ability and electrostatic repulsions between the oxygen in the furan ring and the anions. The position of the furan was also found to be crucial for determining their anion transport activity. Overall, replacement of the characteristic methoxypyrrole moiety of prodiginines and tambjamines by the methoxyfuran found in roseophilin is detrimental to their ability as anion carriers, suggesting that the biological activity of roseophilin is likely not related to their potential activity as anion carriers. Compound 2, bearing a furan ring attached to a dipyrromethene moiety, was found to be the most active anion carrier. [ABSTRACT FROM AUTHOR]

In this study, the experiments were performed to evaluate the Cr(VI) removal efficiency by transport across the polymer inclusion membrane with calixresorcin[4]arene derivative as ion carrier. The several influence factors such as carrier concentration, the amount of plasticizer in the membrane as well the effect of acid type and its concentration in source phase and the membrane stability were investigated. It was found that the immobilized calixresorcin[4]arene derivative in membranes effectively extracted chromium from acidic media. Under optimized conditions, the Cr(VI) removal efficiency was 98.4%. [ABSTRACT FROM AUTHOR]

This work shows application of Cyphos IL 104 (trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate) as the extractant and the ion carrier of Ce(III) and La(III) from aqueous solutions through polymer inclusion membranes (PIM). These membranes were used for separation of Ce(III) from solution containing La(III), Cu(II), Co(II) and Ni(II). The best results of the separation process were obtained for PIM containing: 20.0 wt.% CTA, 55.0 wt.% NPOE and 25.0 wt.% Cyphos IL 104 at pH 3.8 into 1 M H2SO4. The separation coefficients were found in order of SCe/La < SCe/Cu < SCe/Co < SCe/Ni. [ABSTRACT FROM AUTHOR]

An analytical method was developed and validated for the determination of three polyether ionophores (monensin, lasalocid, and salinomycin) in 60 samples of Brazilian Minas Frescal cheese by UHPLC-MS/MS. Linearity ranged from 1 to 8 μg kg−1 for monensin and salinomycin, and from 0.50 to 4 μg kg−1 for lasalocid. Limits of detection and quantitation were 0.50 μg kg−1 and 1 μg kg−1, respectively, for both monensin and salinomycin, and 0.25 μg kg−1 and 0.50 μg kg−1, respectively, for lasalocid. Recoveries were between 69% and 84% with coefficients of variation up to 16.28% for repeatability and 13.79% for intermediate precision. A total of 60 samples of Minas Frescal cheese were analysed and only monensin residues were found. Monensin was detected in 55% of the samples and quantified in 5 of them at mean levels varying from 1.00 to 1.73 μg kg−1. The proposed method demonstrated the suitability for monitoring these substances in cheese. [ABSTRACT FROM AUTHOR]

In this article, we describe the design, synthesis and transmembrane ion transport properties of a small library of molecular membrane-spanning ionophores based on dimer-forming cyclic peptide scaffolds decorated with flexible pendants. Thanks to the modular synthetic approach, it is possible to obtain a variety of α,γ-cyclic peptides with different internal diameters as well as a number of pendant groups that are perpendicularly projected from the peptide backbone. These groups are incorporated by a copper-catalysed cycloaddition between azide-modified oligo-ethylene glycol-based tentacles of different lengths and properties and cyclic peptides bearing a different number of propargyl groups attached at the amide skeleton. This methodology allowed the preparation of different 'spanners' and the identification of new artificial transporters that can rectify transmembranal pH gradients with EC50 values in the medium μM range. [ABSTRACT FROM AUTHOR]

An ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) based multiclass multi-residue method for the simultaneous analysis of 5 polyether ionophores, 4 tetracycline and 10 sulfonamides in animal and aquaculture fish tissues was developed and validated. Sample extraction and clean-up were based on a modified QuEChERS method. The method was validated using an in-house validation based on performance characteristics modified from Commission Decision 2002/657/EC. Both matrix effect and uncertainties associated with sample preparation and instrumental analysis were minimised by the use of matrix-matched calibrations. Recoveries of analytes were generally satisfactory and typically fell between 80% and 113%. The repeatability and intermediate reproducibility measured as relative standard deviations were in most cases less than 15% (n = 63). The decision limit (CCα) and detection capability (CCβ) ranged from 110.7 to 125.8 and 121.5 to 151.7 µg kg−1 for tetracyclines, 113.4 to 118.3 and 116.8 to 126.5 µg kg−1 for sulfonamides and 50.8 to 52.4 and 51.5 to 55.6 µg kg−1 for polyether ionophores, respectively. The method displayed its fitness for purpose through satisfactory results obtained in international proficiency testing schemes. The method was applied to animal and aquaculture fish tissues obtained from different sources in South Africa. Polyether ionophores were predominantly detected in samples in the range 4.26–290.10 µg/kg. Oxytetracycline was found in one porcine liver sample; however, none of the targeted analytes were present above the detection limit in the aquaculture samples. [ABSTRACT FROM AUTHOR]

Cyclic peptides are a large class of natural compounds which attracted a great deal of attention, especially as potential amphi-ionophores. Herein, a theoretical study on the stability of new cystine-based tricyclopeptide (TCP) stereoisomers in achiral media in the presence of Li+, Na+, K+, F−, Cl−, and Br− ions was performed at the M06-2X/6-311++G(d,p) level of theory in both gas and aqueous phases. The nature of the intermolecular interaction between TCPs and ions were studied by natural bond orbital analysis (NBO) and the quantum theory of atoms in molecules (QTAIM) methods in gas phase. According to the size of the ions and configuration of TCPs, the location of ions (within or above the TCPs) and the types of formed intermolecular interactions are different. The results revealed that the free TCP7 and TCP8 enantiomers in gas phase and also TCP1 and TCP2 enantiomers in aqueous phase are the most stable structures among all TCPs. Moreover, the calculated energies of the optimised complexes containing the same ion show different stability order as compared to the free TCPs. [ABSTRACT FROM AUTHOR]

Fertilization problems are the major problems that may be faced in 30-55% of the patients during an intracytoplasmic sperm injection (ICSI) cycle. A successful oocyte activation depends on factors related to both sperm and oocyte, and one of the important factors that mediates the process is Ca2+ concentration within the oocyte. Artificial oocyte activation (AOA) is a method used for fertilization problems that commonly involve the usage of Ca2+ ionophores and is usually used in problems such as total fertilization failure (TFF) and globozoospermia. The aim of the present study was to investigate possible effects of AOA for different groups of patients with fertilization failure. Four groups of patients (previous TFF, low oocyte number, severe sperm quality, and frozen sperm (FS) group) that underwent ICSI with AOA were included in the study. All groups had similar control groups with same indications except TFF, where AOA was not performed. Fertilization rates were significantly higher in the TFF group than those observed in other AOA groups. Fertilization rates and quality of embryos observed in the remaining AOA groups were higher than those of the controls, which were statistically insignificant. Prgenancy rates were higher in all AOA groups compared to the controls, although the differences were significant in FS group only. Quality of embryos and pregnancy rates were lower in the TFF group compared to the remaining AOA groups indicating possible concomitant problems. Fertilization rates, quality of embryos and pregnancy rates seemed to be increased in all indication groups suggesting that not only TFF patients but also a wide variety of patients with different indications may benefit from AOA. Abbreviations: ICSI: Intracytoplasmic sperm injection; ARTs: Assisted reproductive techniques; Ca: Calcium; AOA: Artificial oocyte activation; TFF: Total fertilization failures; OAT: Oligoasthenoteratozoospemia; IVF: In vitro fertilization; SOAT: Severe OAT; LON: Low ooctye number; FS: Frozen sperm; hCG: human chorionic gonadotrophin; PVP: polyvinylpyrrolidone; HSA: human serum albumin [ABSTRACT FROM AUTHOR]

This work aimed to optimise a new nanoemulsion (NE) formulation loaded with Amphotericin B (AmB) and to evaluate itsin vivoantileishmanial activity andin vitrohaemolytic toxicity. The influence of gradual increases in pressure, using a high-pressure homogeniser, was evaluated. The NE was characterised for droplet size, polydispersity index, zeta potential and encapsulation efficiency (EE). For antileishmanial activity studies, AmB-NE was administered intravenously in mice infected byLeishmania infantum chagasi,which causes Visceral Leishmaniasis (VL). When the NE was submitted to gradual increases in pressure, the PI values and droplet size decreased. The droplet size (∼145 nm) was lower than that obtained in previous studies. The zeta potential was negative and the EE was almost 100%. The haemolytic toxicity, evaluated on human red blood cells, for AmB-loaded NE was lower than that observed for the conventional AmB (C-AmB). C-AmB at 2 mg/kg was very toxic. In contrast, administration of the AmB-loaded NE, at same dose, did not result in any sign of acute toxicity, promoting a significant reduction in parasite burden as compared to the C-AmB. These findings suggest that this new AmB-loaded NE constitutes an attractive alternative for the treatment of VL due to improved efficacy and lower toxicity. [ABSTRACT FROM PUBLISHER]

A number of calix[4]arene-based molecules were designed incorporating amide moiety with variation in conformation, rigidity at the binding sites and steric crowding at the upper rim to investigate the anion sensing property of this series of ionophores. These compounds were synthesised and characterised, molecular structures of two of the compounds were established by single-crystal X-ray study. Anion binding property of these ionophores, investigated with the aid of1H NMR and UV–vis spectroscopy, revealed that three (1–3) out of four ionophores strongly interact with F−, in addition, ionophore2interacts with CN−and, ionophore3interacts with CH3COO−andand ionophore4does not interact with any anions. NMR titration was carried out to determine binding constant with strongly interacting anions. Crystal structure analysis revealed that strong intramolecularinteraction in4prevented the anions to interact with the N–H protons of the amide moiety. Interestingly,2with F−and CN−exhibits sharp colour change in acetonitrile–chloroform. Apparently, conformation of the calix moiety, flexibility of the binding sites and intramolecular H-bonding played critical role towards determination of selectivity. Computational study was performed to investigate the interaction site(s) and also to corroborate some of the experimental results. Anion binding study of functionalised calix[4]arenes revealed that conformation, flexibility and intramolecular interaction in calix moiety play critical role to determine ion selectivity. One of the receptors performs as sensitive colorimetric sensor for F−and CN−, computational study also corroborates most of the experimental results. [ABSTRACT FROM PUBLISHER]

Selective solvent extraction (SSX) of Cr(VI) and recovery was evaluated by using a homologous series of symmetric imidazolium bromide salts (SIMs) having various alkyl chain length. Therefore, propyl, pentyl, hexyl, octyl, and decyl substituted SIMs were used as an ion carrier. The executive parameters affecting both extraction and stripping conditions were investigated for optimization. Finally, a direct correlation was observed a between increasing alkyl chain length and selective Cr(VI) extraction from acidic solutions containing Cr(VI), Fe(III), Co(II), Cd(II), Ni(II). This relationship was reversed in the stripping conditions. Optimal extraction and stripping were obtained for SIM5 and SIM2 as 97.49% and 70.00%, respectively. [ABSTRACT FROM AUTHOR]

Four new ion-selective electrodes (ISEs), based onN,N′-bis(salicylaldehyde)-p-phenylene diamine (SPD) as ionophore, are constructed for the determination of copper(II) ion. The modified carbon paste (MCPEs; electrodes I and II) and modified screen-printed sensors (MSPEs; electrodes III and IV) exhibit good potentiometric response for Cu(II) over a wide concentration range of 1.0 × 10−6 – 1.0 × 10−2 mol L−1for electrodes (I and II) and 4.8 × 10−7–1.0 × 10−2 mol L−1for electrodes (III and IV) with a detection limit of 1.0 × 10−6 mol L−1for electrodes (I and II) and 4.8 × 10−7 mol L−1for electrodes (III and IV), respectively. The slopes of the calibration graphs are 29.62 ± 0.9 and 30.12 ± 0.7 mV decade−1for electrode (I) (tricresylphosphate (TCP) plasticizer) and electrode (II) (o-nitrophenyloctylethero-NPOE plasticizer), respectively. Also, the MSPEs showed good potentiometric slopes of 29.91 ± 0.5 and 30.70 ± 0.3 mV decade−1for electrode (III) (TCP plasticizer) and electrode (IV) (o-NPOE plasticizer), respectively. The electrodes showed stable and reproducible potentials over a period of 60, 88, 120, and 145 days at the pH range from 3 to 7 for electrodes (II), (III), and (IV) and pH range from 3 to 6 for electrode (I). This method was successfully applied for potentiometric determination of Cu(II) in tap water, river, and formation water samples in addition to pharmaceutical preparation. The results obtained agree with those obtained with the atomic absorption spectrometry (AAS). [ABSTRACT FROM PUBLISHER]

The synthesis and structure of thiacalix[4]monocrowns in1,3-alternateconfiguration substituted by terpyridyl fragments on the lower rim are being discussed. It has been shown that the number of oxyethylene units in oligoethylene glycol chain affects the distribution of the yields of the cross-linking products leading to either thiacalix[4]monocrowns or bisthiacalix[4]arenes. Their complexation ability towards alkali metal and lanthanide ions has been studied using liquid extraction and MALDI TOF MS, in addition to luminescent properties of ligands and their lanthanide complexes. The NMR titration data discovered the participation of both crown ether and terpyridyl fragment in the coordination of lanthanide cations. The fluorescent titration showed the nonlinear emission response to the amount of lanthanide ions. [ABSTRACT FROM AUTHOR]

This article describes a versatile application of 25,27-bis-N-(N,N-diethyl-2-aminoethyl)carbonylmethoxy-26,28-dihydroxycalix[4]arene (4) as an ionophore for the preparation of perchlorate ion-selective electrode. The electrode exhibits a Nernstian response over the perchlorate concentration range of 1.0×10−9– 1.0×10−1M with a slope of 59.24 ± 0.5 mV per decade of the concentration. The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot is 3.04×10−9M. The electrode shows good selectivity toward perchlorate with respect to many common anions. The response time of the sensor was 5–10 s and it has maximum life time of 2 months in the acidic pH. The electrode was used to determine perchlorate in real water samples. The interaction of the ionophore with perchlorate ions is also demonstrated by UV–vis spectroscopy. [ABSTRACT FROM PUBLISHER]

The synthesis and characterisation ofp-t-butylcalix[4]arene functionalised at the lower rim with four tetrazole moieties is reported. The macrocycle is found to be a poorer ionophore for lanthanoid cations than the bis-tetrazole–substituted analogue. Solution-phase photophysical studies strongly suggested that the cations interacted only weakly with the calixarene ligand. A mixed sodium/triethylammonium salt of the calixarene ligand was crystallised in the presence of lanthanoid cations and structurally characterised. Strong intramolecular interactions are hypothesised to be the cause of the observed behaviour. [ABSTRACT FROM AUTHOR]

The emergingFusariummycotoxins enniatins (ENNs) have diverse biological properties, mainly due to their ionophoric activity, and represent a potential risk to human and animal health since they are commonly found in food and feed.In vivotoxicity studies are scarce and limited to the major mycotoxins. Until now, any method for the simultaneous analysis of these compounds in plasma, serum and feces from rat has been reported. A method for the extraction and determination of ENNs A, A1, B and B1 from Wistar rat samples by liquid chromatography tandem mass spectrometry has been developed. The method was successfully validated with satisfactory recoveries (70–106%), good intraday (<10%) and interday (<20%) precision, expressed as relative standard deviation, and good linearity between limits of quantitation (LOQ) and 100 times LOQ. Limits of detection (LOD) and LOQ were ≤1 and ≤10 ng/ml, respectively. The validated method was applied for the analysis of biological Wistar rat samples that were administered a mixture of ENNs containing 1.19, 2.16, 1.03 and 1.41 mg/kg body weight of ENN A, A1, B and B1, respectively. Blood, urine and feces samples collected every 2 h during the 8-h duration of the experiment were analyzed. The administered dose of the mixture of ENNs did not cause observable adverse effects on the animals. ENNs concentrations detected in serum and urine were below LOQs. The four ENNs were detected in feces reaching the maximum concentration at 6 h after administration. [ABSTRACT FROM AUTHOR]

A pyrene-appended ratiometric fluorescent chemosensorLbased on a synthetic approach of insulating the fluorophore from the ionophore by a specific molecular spacer has been synthesised and characterised. The fluorescence spectra changes ofLsuggested that the chemosensor can detect heavy and transition metal (HTM) ions ratiometrically and with variable sensitivity according to the substituents present.1H NMR titration experiments indicated that the three triazole ligands prefer binding with Hg2+, Pb2+and Zn2+, resulting in a conformational change that produces monomer emission of the pyrene accompanied by the excimer quenching. However, the addition of Fe3+, which may be accommodated by the cavity ofL, makes the pyrene units move closer to each other, and a discernible increase in the emission intensity of the static excimer is observed. Therefore, it is believed that the ditopic scaffold of the calix[3]arene as a specific molecular spacer here plays an important role in the blocking of the heavy atom effect of HTM ions by insulating the fluorophore from the ionophore given the long distance between the metal cation and the pyrene moiety. [ABSTRACT FROM PUBLISHER]

Methoxychlor, an organochlorine insecticide developed to replace DDT (dichlorodiphenyltrichloroethane), has been reported to induce mast cell degranulation and to enhance IgE-mediated allergic responses. However, the mechanisms underlying these effects are not clear. To clarify potential mechanisms, the effects of methoxychlor on degranulation of mast cells were examined. Degranulation responses were evaluated using RBL-2H3 cells and mouse bone marrow-derived mast cells with either the antigen-induced or calcium ionophore-induced stimulation. Phosphorylation of enzymes related to signaling events associated with mast cell degranulation was analyzed by immunoblotting. Effects on vascular permeability in the passive cutaneous anaphylaxis reaction were evaluated following oral administration of methoxychlor to BALB/c mice. The results indicated that methoxychlor caused increased mast cell degranulation in the presence of antigen, whereas it had no effect on calcium ionophore-induced degranulation of RBL-2H3 cells. Immunoblot analyses demonstrated that the phosphorylation level of phosphoinositide 3-kinase (which plays a central role in mast cell signaling) was increased by methoxychlor during antigen-induced degranulation. In addition, methoxychlor activated the signaling pathway via the high-affinity IgE receptor by inducing phosphorylation of Syk and PLCγ1/2, which transfer the signal for degranulation downstream. Lastly, oral administration of methoxychlor exhibited a tendency to promote vascular permeability in passive cutaneous anaphylaxis model mice. Taken together, the results here suggested that methoxychlor enhanced degranulation through Fc&varepsilon;RI-mediated signaling and promoted allergenic symptoms involved in mast cell degranulation. [ABSTRACT FROM AUTHOR]

To test the hypothesis that a fall in cellular ATP following stimulation of endothelial cells with thrombin is secondary to a decrease in NAD levels caused by poly(ADP-Ribose)polymerase (PARP), we measured the levels of NAD and ATP in endothelial cells after treatment with thrombin, the Ca++-ionophore A23187, or hydrogen peroxide (H2O2), and compared the effects of inhibitors of PARP, NAD synthesis, and ADP-ribose breakdown on these responses. Neither thrombin nor A23187 caused a reduction in endothelial NAD levels and A23187 affected ATP levels independently of NAD levels or PARP activity. H2O2induced lowering of NAD caused modest lowering of ATP but marked additional ATP-lowering, independent of PARP and NAD, was also demonstrated. We conclude that in endothelial cells ATP levels are largely independent of NAD and PARP, which do not play a role in thrombin or Ca++-ionophore-mediated lowering of ATP. H2O2caused ATP lowering through a similar mechanism as thrombin and A23187 but, additionally, caused a further ATP lowering through its intense stimulation of PARP and marked lowering of NAD. [ABSTRACT FROM PUBLISHER]

Facilitated transport of Ni(ll) ions across a supported liquid membrane (SLM) by dithiophosphonates dissolved in methanol as carrier has been investigated. In this work, the SLMs were composed of ionic ligands ammonium-O-ethyl (4-methoxyphenyl) dithiophosphonate (LI), ammonium-O-propyl (4-methoxyphenyl) dithiophosphonate (L2), ammonium-O-isopropyl (4-methoxyphenyl) dithiophosphonate (L3), and ammonium-O-butyl (4-methoxyphenyl) dithiophosphonate (L4) as the carriers. Polyvinylidene fluoride (PVDF) hydrophobic microporous membrane was used as support. The experiments were carried out at various operating conditions such as feed phase pH, receiver phase concentration, carrier concentration in the membrane phase, different valence metal ion, and SLM stability. The morphology of SLMs was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), andfourier transform infrared spectroscopy (FTIR). The SEM, AFM, ami FTIR images, comparing the PVDF membrane support to SLMs, indicate that the surface morphologies of the membranes are different. The flux values (J) and recovery factors (RF) of Ni(II) ions were obtained at optimum pH 2. Similar flux results were obtained for all SLMs at optimum condition and in a period of 8 h. Increase in carrier concentration inside the membrane enhances Ni(II) concentration with its maximum value at 4.0 x 10-1 mol/L carrier. [ABSTRACT FROM AUTHOR]

On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Eu3+(aq) + 3A−(aq) +1(nb) ⇆1·Eu3+(nb) + 3A‑(nb) occurring in the two-phase water–nitrobenzene system (A−= CF3SO−3;1= lithium ionophore VIII; aq = aqueous phase, nb = nitrobenzene phase) was determined as logKex(1·Eu3+, 3A‑) = 2.5 ± 0.1. Furthermore, the extremely high stability constant of the1·Eu3+complex in nitrobenzene saturated with water was calculated: log βnb(1·Eu3+) = 15.6 ± 0.1. Finally, by using DFT calculations, the most probable structure of the cationic complex species1·Eu3+was derived. In the resulting complex, the ‘central’ cation Eu3+is bound by six very strong bond interactions to the corresponding six oxygen atoms of the parent ligand1. It is evident that this exceptionally effective receptor1for the Eu3+cation could be considered as a potential extraction agent for nuclear waste treatment. [ABSTRACT FROM AUTHOR]

Semduramicin is an ionophore coccidiostat used in the poultry industry as a feed additive. Cross-contamination of feeds for non-target animals with semduramicin is unavoidable. However, it is not known whether undesirable residues of semduramicin may occur in food after cross-contaminated feed is administered to animals. The aim of the work was to determine the levels of semduramicin in hen eggs (yolks and albumen) and tissues (liver, muscle, spleen, gizzard, ovarian yolks and ovaries) after administration of feed contaminated with 0.27 mg kg−1of this coccidiostat. The residues were determined using LC-MS/MS. The distribution pattern confirmed the high lipophilicity of semduramicin. Residues were found mainly in egg yolks (28.8 µg kg−1), ovarian yolks (19.5 µg kg−1) and liver (2.57 µg kg−1), while hens’ muscle was free from semduramicin (LOD = 0.1 µg kg−1). Among edible tissues, the maximum level (2 µg kg−1) was exceeded only in the liver. [ABSTRACT FROM PUBLISHER]

Separation of nickel(II) and cadmium(II) ions from sulphate solution with use of supported liquid membranes (SLM) has been studied. Di(2-ethylhexyl)phosphoric acid (D2EHPA) dissolved in kerosene was used as the ion carrier. Obtained data were compared with data from polymer inclusion membranes (PIM) experiments. It was shown that use of SLM membranes enables separation of Ni(II) and Cd(II) ions. Experimental results data show that faster transport and higher recovery factor values were obtained for supported liquid membranes. [ABSTRACT FROM PUBLISHER]

This report describes a successful pregnancy and delivery following oocyte activation with strontium chloride (SrCl2) in couples with repeated complete fertilization failure or low fertilization rates even after calcium ionophore treatment. Eight infertile couples who showed complete fertilization failure or low fertilization rates after conventional intracytoplasmic sperm injection (ICSI) and calcium ionophore treatment. When the results of fertilization were not satisfactory in the cycles, the oocytes were artificially activated by SrCl2 for the next attempts. Oocyte activation with SrCl2 significantly increased the fertilization rates, when compared with conventional ICSI or calcium ionophore treatment (61.7% vs. 20.0% or 25.3%, respectively). There was significant increase in the proportions of good-quality cleaved embryos (50.0% vs. 0% or 12.5%, respectively). The rate of surplus embryos that developed to blastocyst stage increased in SrCl2-treated oocytes, when compared with that in ICSI with or without calcium ionophore treatment (25.7% vs. 0% or 9.1%, respectively). Five successful pregnancies were attained after oocyte activation with SrCl2, of which eight healthy children were born. Physical and mental development of the children were normal from birth to 60 months. These results suggest that SrCl2 in treatment should be considered as an effective method for artificial oocyte activation (AOA) to improve fertilization rates and embryo quality in cases with complete fertilization failure or low fertilization rates after calcium ionophore treatment. [ABSTRACT FROM AUTHOR]

A multi-residue analytical methodology has been established for the determination of the four ionophores: lasalocid, monensin, salinomycin and narasin in aqueous environmental matrices, using nigericin as internal standard. The samples were filtrated prior to solid phase extraction. All compounds were measured using liquid chromatography coupled to tandem mass spectrometry applying electro spray ionisation. The absolute recoveries ranged from 92 to 110% (relative standard deviation: 2–14%) for spiked river water. The final method allowed for detection of ionophores down to a few ng/L in natural water bodies with LOQs for the entire methodology being 40, 49, 67, and 14 ng/L for lasalocid, monensin, salinomycin, and narasin, respectively. [ABSTRACT FROM AUTHOR]

In this paper, methods were developed to measure coccidiostats in bovine milk, duck muscle and non-avian species. The methods were validated to the maximum levels and MRLs laid down in European Union legislation. A simple sample preparation procedure was developed for the isolation of coccidiostat residues from bovine, ovine, equine, porcine and duck muscle tissue, based on solvent extraction with acetonitrile and concentration. An alternative method had to be developed for milk samples based on the QuEChERS sample preparation approach because of the high water content in this matrix. Milk samples were adjusted to basic pH with sodium hydroxide and extracted by using a slurry of acetonitrile, MgSO4and NaCl. Purified sample extracts were subsequently analysed by using UHPLC-MS/MS in a 13.2-min chromatographic run. It was found that the use of rapid polarity switching enabled both negatively and positively charged ions to be analysed from a single injection. By using this approach, solvent usage was reduced significantly and sample throughput improved. The method was validated for the analysis of 20 coccidiostats (arprinocid, clopidol, decoquinate, diclazuril, diaveridine, ethopabate, halofuginone, laidlomycin, lasalocid, maduramicin, monensin, narasin, nequinate, nicarbazin, robenidine, salinomycin, semduramicin, toltrazuril, toltrazuril sulphoxide and toltrazuril sulphone) in muscle and milk. The method is quantitative for toltrazurils, but it cannot be used for confirmation because only the precursor ion is monitored. Accuracy values for muscle ranged from 80% to 125%, while CCα ranged from 2.2 µg kg−1for clopidol to 122 µg kg−1for toltrazuril sulphoxide. Bovine milk accuracy ranged from 84% to 120% for all analytes except maduramicin, semduramicin and salinomycin, for which the values were higher. CCα values achieved ranged from 1.1 µg kg−1for arprinocid, nequinate and lasalocid to 27 µg kg−1for toltrazuril. [ABSTRACT FROM PUBLISHER]

A novel ion selective carbon paste electrode for Cd2+ions based on 2,2′-thio-bis[4-methyl(2-amino phenoxy) phenyl ether] (TBMAPPE) as an ionophore was prepared. The carbon paste was made based on a new nano-composite including multi-walled carbon nanotubes (MWCNTs), nanosilica and room-temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). The constructed nano-composite electrode showed better sensitivity, selectivity, response time, response stability and lifetime in comparison with typical Cd2+carbon paste sensor for the successful determination of Cd2+ions in water and in waste water samples. The best performance for nano-composite sensor was obtained with an electrode composition of 18% TBMAPPE, 20% BMIM-PF6, 48% graphite powder, 10% MWCNT and 4% nanosilica. The new electrode exhibited a Nernstian response (29.95 ± 0.10 mV decade−1) toward Cd2+ions in the range of 3.0 × 10−8to 1.0 × 10−1 mol L−1with a detection limit of 7.5 × 10−9 mol L−1. The potentiometric response of prepared sensor was independent of the pH of test solution in the pH range 3.0 to 5.5. It had a quick response with a response time of about 6 s. The proposed electrode showed fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions. [ABSTRACT FROM PUBLISHER]

Selective recognition of alkali and alkaline earth metal ion pairs viz.Li+, Na+, K+, Mg2+and Ca2+is of great biological importance. Design and synthesis of ionophores and receptor molecules capable of selectively binding and transporting substrates (neutral and ionic) are based on molecular recognition and used to develop membrane separation systems. This has potential applications in analytical, environmental, and biomimetic chemistry. We have designed and synthesized new series of anthraquinone derived single and double armed ionophores. Supermolecules have been isolated with these synthetic podands as host and metal ions as guest. Interaction has been confirmed by melting point (m.p.), infrared red (IR), and proton nuclear magnetic resonance (1H NMR) spectral analysis and cyclic voltammetric studies. Further, the liquid liquid extraction, bulk liquid membrane (BLM) transport, and supported liquid membrane (SLM) transport studies using polytetrafloroethylene membrane, cellulose nitrate membrane, onion membrane and egg shell membrane, have been done to find out the selectivity of these ionophores for various metal ions. Among the two liquid membrane systems used SLMs is more efficient than BLMs. It is found that double armed and bridged ionophores (A3to A8) show better extraction ability than single armed ionophores (A1, A2) and ionophore A3is calcium selective. [ABSTRACT FROM PUBLISHER]

Three new thiazolobenzocrown (TBC) ethers conjugated with picolinic acid, benzoic acid and pyridylmethyl were synthesised and their binding properties towards amino acids were assessed by1H NMR titration and isothermal titration calorimety (ITC). The TBC-picolinic acid conjugate (4) showed a pronounced selectivity towards GABA by the1H NMR titration, and the association constant for GABA had the largest value determined by ITC. The association constant of4for GABA was about 19 times higher than that of glycine. [ABSTRACT FROM PUBLISHER]

The importance of calixarene nanobaskets in drug development and controlling their toxicity comes back to their ability to encapsulate the drug species and biological compounds. New complexes show improved physical characteristics, such as more solubility in water and enhanced chemical properties, including less toxicity in biological systems. Moreover, the covalent bonding, inclusion encapsulation, and induction activities of calixarenes lead to improving the activity of drug molecules. This review article deals with the importance of calixarene-based drugs and illustrates their potentials in drug development and toxicity control. The main aim and novelty of this study was to introduce the role and the action of calixarene scaffolds and their conjugated upper and lower rims as well as their binding mechanism in biomedical systems. The main aspects of this approach are classified in four categories and are discussed according to the results of recent researches. [ABSTRACT FROM AUTHOR]

Veterinary anticoccidials, biochemically known as ionophores, are widely used in poultry feed at therapeutic levels to treat Coccidiosis and at sub-therapeutic levels for growth- promotion. Commonly used ionophores in the US poultry industry are monensin, salinomycin, lasalocid and narasin. There is an increasing concern regarding the persistence of these anticoccidials in the environment. However, little attention has been directed to methods development for quantitatively measuring ionophores in complex environmental matrices such as poultry litters that are land applied. Here, we describe a rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS)-based method developed for simultaneous quantification of monensin, lasalocid, salinomycin, and narasin in aged poultry litter samples. Results show significant level of monensin (97.8 ± 3.2 μg kg−1), lasalocid (19.2 ± 6.6 μg kg−1), salinomycin (70 ± 2.7 μg kg−1) and narasin (57.3 ± 2.6 μg kg−1) in poultry litter stored for over three years at < 5°C. Our findings indicate that even after several years of unmanaged storage of poultry litter, ionophores may continue to persist in this matrix, raising the possibility of prolonged release into the environment. [ABSTRACT FROM PUBLISHER]

A new chemically modified carbon paste electrode is fabricated to determine lead ion concentration in its trace level in aqueous media with differential pulse voltammetry (DPV). The best performance is obtained by the carbon paste electrode composition including 20% of dithiodibezoic acid (DDA), 80% of high purity graphite powder and 60 µL of colloidal gold nanoparticle (AuNP) solution. The proposed electrode has a wide linear calibration response from 1 × 10−9 to 6 × 10−5 M with a detection limit of 6.6 × 10−10 M, at pH 3.5. Seven replicate determination of 5 × 10−8 M of lead ion concentration gives a relative standard deviation of 3.33%. The modified sensor is applied to determine lead contents in some environmental and biological Samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine whether dehydroleucodine, xanthatin and 3-benzyloxymethyl-5 H-furan-2-one inhibit the activation of human leukemic LAD2 mast cells induced by compound 48/80 or the calcium ionophore A23187. LAD2 cells were preincubated in the presence of test drugs and then challenged with the secretagogues. This study provides the first evidence in favor of the view that dehydroleucodine and xanthatin inhibit the degranulation of LAD2 cells, thus acting as human mast cell stabilizers. These molecules could be effective in the treatment of human diseases associated with inappropriate mast cell activation. [ABSTRACT FROM AUTHOR]

Detection of acetylcholine (ACh+) with high sensitivity and selectivity in the presence of interfering ions including choline (Ch+) poses a significant analytical challenge. A cucurbit[6]uril derivative, (allyloxy)12CB[6], forms a stable 1:1 inclusion complex with ACh+ but does not interact significantly with Ch+ in solution. Based on this result, we prepared ion-selective electrodes (ISEs) for ACh+ using (allyloxy)12CB[6] as an ionophore. The (allyloxy)12CB[6]-based ISEs detect ACh+ with unprecedentedly high selectivity over Ch+ as well as other interfering ions such as dopamine, NH4 [ABSTRACT FROM AUTHOR]

The antibiotic valinomycin is a potassium-selective ionophore, which increases the transport of potassium ions across cell membranes and thereby causes damage to bacteria cells. Valinomycin has been extensively studied as an ionophore for cations. We report for the first time the direct binding of anions to valinomycin using electrospray ionisation mass spectrometry and 1H nuclear magnetic resonance (NMR) spectroscopy. The binding selectivity for halide ions is found to be in the order Cl− >Br− ∼F− ≫I−  based on electrospray ionisation mass spectrometry experiments in methanol. 1H NMR studies in acetone-d 6 and CD3CN reveal the binding selectivity of Cl− >Br− ≫F− ∼I− . NMR studies and density functional theory (DFT) calculations support a bracelet-like structure for the binding of a chloride ion to valinomycin. Association constants of 531 ± 45 M− 1 and 57 ± 2 M− 1 were obtained via NMR titrations in acetone-d 6 for chloride and bromide ions, respectively. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Bifunctional combination of carbon nanotubes and ionophore is introduced for anodic stripping analysis of lead (Pb2+). Carbon nanotubes are employed to improve the detection sensitivity due to their excellent electrical conductivity and strong adsorption ability. An ionophore is utilized for its excellent selectivity toward Pb2+. The proposed carbon nanotubes/ionophore modified electrode shows improved sensitivity and selectivity for Pb2+. Low detection limit (1 nM), wide linear range (5 nM-8 µM) and excellent selectivity over other metal ions (Cd2+, Cu2+, and Hg2+) was obtained. The practical application has been carried out for determination of Pb2+ in real water samples. [ABSTRACT FROM AUTHOR]

The structural features of two series of 1-furoylthioureas 3-monosubstituted (Series 1) and 3,3-disubstituted (Series 2) 1-furoylthioureas and their CdCl2 complexes are discussed. The coordination strength through the sulfur atom is determined by the ligand structure. In Series 1 ligands, the carbonyl group and the proton on N2 are engaged in a strong hydrogen bond interaction. This leads to an 'S'-shaped conformation type of the C=O and C=S groups where these donor sites reach a maximum separation. In the absence of that hydrogen bridge in 3,3-disubstituted derivatives, the C=O and C=S groups can adopt a 'U'-shaped conformation type. This feature is also observed for two novel crystal structures of 1-(2-furoyl)-3-(2-hydroxyethyl)thiourea and 1-furoyl-3-ethyl-3-phenylthiourea, as determined by X-ray diffractometry and reported here. Emphasis is placed on the relationship between structural features of these ligands and their behavior as cadmium ionophores in potentiometric and amperometric sensors. [image omitted] [ABSTRACT FROM AUTHOR]

This work deals with the evaluation of different thiacalix[4]arene derivatives included in polymeric PVC membranes for the optical sensing of metallic cations. Two ligands have been studied: thiacalix[4]arene (ligand 4) and its p-tert-butyl-derivative (ligand 2). Membranes including ligand 4 were tested for different metals and better results were obtained for Cd2+, Ag+, and Pb2+. In the case of films incorporating the neutral ionophore, ligand 2, a pH sensitive dye (ETH 2439), and an anionic additive were also added. A selective response to Ag+ was achieved in acetate buffer at pH 5. [ABSTRACT FROM AUTHOR]