Search results for "Potentiometric"
showing 10 items of 157 documents
Polyaza and azaoxa macrocyclic receptors functionalised with fluorescent subunits; Hg2+ selective signalling
2000
A polyazacycloalkane containing naphthyl groups, 1,4,8,11-tetrakis(naphthylmethyl)-1,4,8,11-tetraazacyclotetradecane (L1), and the azaoxa cycloalkane receptors containing anthracenyl groups, 7,13-bis(anthracenylmethyl)-1,4,10-trioxa-7,13-diazacyclopentadecane (L2) and 10-anthracenylmethyl-1,4,7-trioxa-10-azacyclododecane (L3), have been synthesized and their activity as fluorescent chemosensors studied towards the metal cations Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ in THF–water (70∶30 v/v, 0.1 mol dm−3 tetrabutylammonium perchlorate, 25 °C) for L1 and 1,4-dioxane–water (70∶30 v/v, 0.1 mol dm−3 potassium nitrate, 25 °C) for L2 and L3. The crystal structure of the complex [Cd(L1)(Cl)][PF6] has been…
Study of the coordination of ortho-tyrosine and trans-4-hydroxyproline with aluminum(III) and iron(III)
2018
Abstract The coordination of amino acids ortho-tyrosine (o-Tyr, 1) and trans-4-hydroxyproline (HPro, 2) with the biologically important trivalent metal ions Al(III) and Fe(III) in aqueous solution was investigated by 1H and 13C high resolution NMR, Laser Desorption Mass Spectrometry (LD-MS), and MS/MS experiments. Potentiometric measurements were also carried out in 0.16 M NaCl, 37 °C, by varying the pH between 2.0 and 3.5. NMR spectra recorded on aqueous solutions of amino acids 1 or 2 in the presence of the appropriate trivalent metal chloride suggested that binding of Al(III) and Fe(III) involved the COOH and NH2 functional groups of ligands, while their phenolic and alcoholic groups whi…
Validation of a method for the determination of boron in ceramic materials by X-ray fluorescence spectrometry
2000
Abstract A method is proposed for boron determination in ceramic materials, boracic raw materials and ceramics frits of different compositions by wavelength dispersive X-ray fluorescence technique. The instrumental conditions were studied and the sample preparation procedures were optimized. The reference method used was the potentiometric titration of mannitol–boric complex acid and the technique was optimized for the determination of B 2 O 3 in each of the materials used. The samples for XRF determination were obtained as pellets and as glass discs. For the pellets different binders were studied, such as mannitol and cellullose for the samples of raw materials, and polyvinylpirrolidone an…
Solid proton conductors as room-temperature gas sensors
1993
Ammonia-exchanged ceramic samples of beta alumina have been obtained from plasma-dispersed powders. The ionic conductivity is slightly affected by ion exchange, but the surface conductivity for the amonia-exchanged sample drastically changes in the presence of the water and ammonia vapours. The ammonia-doped xerogel of antimonic acid hydrate in the form of a thick film has been tested as a potentiometric ammonia sensor.
PAA-PAMPS Copolymers as an Efficient Tool to Control CaCO3 Scale Formation
2013
Scale formation, the deposition of certain minerals such as CaCO3, MgCO3, and CaSO4 center dot 2H(2)O in industrial facilities and household devices, leads to reduced efficiency or severe damage. Therefore, incrustation is a major problem in everyday life. In recent years, double hydrophilic block copolymers (DHBCs) have been the focus of interest in academia with regard to their antiscaling potential. In this work, we synthesized well-defined blocklike PAA-PAMPS copolymers consisting of acrylic acid (AA) and 2-acrylamido-2-methyl-propane sulfonate (AMPS) units in a one-step reaction by RAFT polymerization. The derived copolymers had dispersities of 1.3 and below. The copolymers have then b…
The solution behavior of dopamine in the presence of mono and divalent cations: A thermodynamic investigation in different experimental conditions
2021
The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop-)] with methylmercury(II) (CH3Hg+), magnesium(II), calcium(II), and tin(II) were studied in NaCl(aq) at different ionic strengths and temperatures. Different speciation models were obtained, mainly characterized by mononuclear species. Only for Sn2+ we observed the formation of binuclear complexes (M2L2 and M2LOH (charge omitted for simplicity)
Antibiotic as Ligand. Coordinating Behavior of the Cephalexin Towards Zn(II) and Cd(II) Ions
1987
The complex formation equilibria of Zn(II) and Cd(II) with cephalexin have been studied through potentiometric titrations. Experimental data were analyzed using the least squares computer program SUPERQUAD. The stability constants were 1g beta ZnCEX+ = 2.40, 1g beta Zn(CEX)(OH) = -4.54, 1g beta CdCEX+ = 2.18, and 1g beta Cd(CEX)(OH) = -5.18 (I = 0.1 M NaNO3), CEX complexes of formulae Zn(CEX)2(3)H2O and Cd(CEX)(OH)H2O have been synthesized and characterized by elemental analysis, IR spectra, conductivity measurements, and electronic and NMR spectra. The thermal behavior of the synthesized compounds were studied by TGA and DTA. We conclude that the metal ion interacts with the amido group of…
A simple helical macrocyclic polyazapyridinophane as a stereoselective receptor of biologically important dicarboxylates under physiological conditio…
2007
The interaction of a synthetic enantiopure azamacrocyclic receptor (L) with biologically important chiral dicarboxylates (A, 1-7) has been studied by means of potentiometric titrations in 0.15 M NaCl aqueous solution in a wide pH range. This macrocycle forms strong complexes of the type [HnLA](n-2) (with n = 0-5). As a general trend, the binding is much tighter at basic or neutral pH than in acidic medium. Interestingly, nonprotected excitatory amino acids (Asp and Glu) are strongly bound even at acidic pH. Regarding selectivity, the receptor showed stereoselective binding toward those substrates bearing an H-bonding donor at Calpha, being S-selective in most of the cases, except for glutam…
Coordination Diversity in Mono- and Oligonuclear Copper(II) Complexes of Pyridine-2-Hydroxamic and Pyridine-2,6-Dihydroxamic Acids
2013
Solution and solid state studies on Cu(II) complexes of pyridine-2-hydroxamic acid (HPicHA) and pyridine-2,6-dihydroxamic acid (H2PyDHA) were carried out. The use of methanol/water solvent allowed us to investigate the Cu(II)-HPicHA equilibria under homogeneous conditions between pH 1 and 11. In agreement with ESI-MS indication, the potentiometric data fitted very well with the model usually reported for copper(II) complexes of α-aminohydroxamate complexes ([CuL](+), [Cu5(LH-1)4](2+), [CuL2], [CuL2H-1](-)), however with much higher stability of the 12-MC-4 species. A series of copper(II) complexes has been isolated in the solid state and characterized by a variety of spectroscopic methods, …
(Trifluoromethoxy)Phenylboronic Acids: Structures, Properties, and Antibacterial Activity.
2021
Three isomers of (trifluoromethoxy)phenylboronic acids were studied in the context of their physicochemical, structural, antimicrobial and spectroscopic properties. They were characterized by 1H, 13C, 11B and 19F NMR spectroscopy. The acidity of all the isomers was evaluated by both spectrophotometric and potentiometric titrations. The introduction of the -OCF3 group influences the acidity, depending, however, on the position of a substituent, with the ortho isomer being the least acidic. Molecular and crystal structures of ortho and para isomers were determined by the single crystal XRD method. Hydrogen bonded dimers are the basic structural motives of the investigated molecules in the sol…