Search results for "ionic strength."
showing 10 items of 196 documents
Methylone determination in oral fluid using microextraction by packed sorbent coupled to ion mobility spectrometry
2020
Abstract A methodology based on microextraction by packed sorbent (MEPS) followed by ion mobility spectrometry (IMS) has been developed for the simple and automated determination of methylone in oral fluids. MEPS was carried out using a 100 µL eVol® XR hand-held automated analytical syringe filled with octadecyl silica sorbent. The effect of main experimental parameters of MEPS such as sample pH and ionic strength, number of aspirating/dispensing cycles, and elution solvent was studied to obtain a quantitative extraction of methylone. Oral fluid samples were spiked with methylone at different concentration levels from 50 to 400 µg L−1 and analyzed by the proposed MEPS-IMS procedure, giving …
A novel peat-based biosorbent for the removal of phosphate from synthetic and real wastewater and possible utilization of spent sorbent in land appli…
2015
AbstractRemoval of potentially harmful phosphorus compounds from wastewater by adsorption onto biosorbents is a cost-effective alternative to the conventional treatment methods. Raw peat and peat modified with iron(III) hydroxy ions were used in this study to remove phosphate ions from synthetic solution and household wastewater. Interaction of iron(III) ions with carboxylic groups of peat occurred during peat modification, which was confirmed by the FTIR technique. The effect of the initial phosphate concentration, pH, contact time, temperature, and ionic strength was studied in batch experiments. It was found that the sorption capacity increased with the increasing temperature, i.e. the m…
Biochar from byproduct to high value added material – A new adsorbent for toxic metal ions removal from aqueous solutions
2018
Abstract An activated biochar coming from pyrolysis of dead Posidonia oceanica residues has been tested as adsorbent material for Cd2+, Pb2+ and Cu2+ ions. The biomass, the activated and the non activated biochars were previously characterized by using several instrumental techniques. The pH of metal ion solution in kinetic and thermodynamic adsorption experiments was fixed at 5 whilst, the dependence on ionic medium, ionic strength and temperature have been evaluated carrying out batch experiments at different experimental conditions. Differential Pulse Anodic Stripping Voltammetry and Inductively Coupled Plasma Optical Emission Spectroscopy have been used to measure the metal ion concentr…
FUNCTIONALIZED HALLOYSITE NANOTUBES FOR ENHANCED REMOVAL OF Hg2+ IONS FROM AQUEOUS SOLUTIONS
2021
AbstractWater is essential for humans, animals, and plants; pollutants, usually derived from anthropogenic activities, can have a serious effect on its quality. Heavy metals are significant pollutants and are often highly toxic to living organisms, even at very low concentrations. Among the numerous removal techniques proposed, adsorption onto suitable adsorbent materials is considered to be one of the most promising. The objective of the current study was to determine the effectiveness of halloysite nanotubes (HNT) functionalized with organic amino or thiol groups as adsorbent materials to decontaminate polluted waters, using the removal of Hg2+ ions, one of the most dangerous heavy metals…
Protonation constants and association of polycarboxylic ligands with the major components of seawater
2000
Apparent protonation constants, log βjH*, of 11 carboxylic acids were determined potentiometrically ([H+]-glass electrode) in artificial seawater containing six of the major components (Na+, K+, Mg2+, Ca2+, Cl-, and SO42-) at different salinities: S (‰) = 5, 15, 25, 35, 45. Values of log βjH* were fitted by the simple polynomial equation log βjH* = log TβjH + a1S1/2 + a2S + a3S3/2 (log TβjH = protonation constants at infinite dilution; a1, a2, a3 = empirical parameters), for mono-, di-, and tricarboxylates. For carboxylic anions with charge < −3, a better fit was obtained using the equation log βjH* = log TβjH + b1I + b0z* log(1 + b2I) (b0, b1, b2 = empirical parameters, z* = square sum of…
Interaction of the Dioxouranium(VI) Ion with Aspartate and Glutamate in NaCl(aq) at Different Ionic Strengths
2005
The formation of complexes species of the dioxouranium(VI) ion with aspartic and glutamic acids was studied in the pH range of 3 to 6 at 25 °C by potentiometric measurements (H+−glass electrode). R...
Macromolecules in ordered media: 4. Poly(2-vinyl pyridine)-liposome association induced by electrostatic interactions
1997
Abstract We have investigated the interaction between vesicles based on dimyristoyl phosphatidic acid (DMPA) and a polymer, such as poly(2-vinyl pyridine) (P2VPy), on the basis of both partition and binding models. The resulting association curves are non monotonous being three regions clearly evidenced. The electrostatic and steric origin of the attractive or repulsive interactions are analyzed as a function of pH, ionic strength and temperature using the fluorescence spectroscopy technique. We emphasize the importance of differentiating the ideal definition of the binding constant from the theoretically evaluated including the activity coefficient, γ, to take into account shifts from the …
Protein-lipid interactions at the air-water interface.
2010
International audience; Protein−lipid interactions play an important role in a variety of fields, for example in pharmaceutical research, biosensing, or food science. However, the underlying fundamental processes that govern the interplay of lipids and proteins are often very complex and are therefore studied using model systems. Here, Langmuir monolayers were used to probe the interaction of a model protein with lipid films at the air−water interface. The protein β-lactoglobulin (βlg) is the major component in bovine milk serum, where it coexists with the milk fat globular membrane. During homogenization of milk, βlg adsorbs to the interface of lipid fat globules and stabilizes the oil-in-…
Different Dissolution Media Lead to Different Crystal Structures of Talinolol with Impact on Its Dissolution and Solubility
2003
During the performance of dissolution tests with immediate and controlled-release talinolol tablets it was detected that the type of the buffer used as dissolution medium had a strong influence on the solubility and the dissolution behavior of the drug. It was proven that talinolol appeared in different crystal structures with strongly differing solubilities when pure water, acetate, or phosphate buffers were employed as dissolution media. The resulting crystal structures were characterized by means of light microscopy, differential scanning calorimetry, and X-ray powder diffraction. All methods were adjuvant to detect changes in talinolol crystal structures. The different solubility and di…
Conformation of a chain polyelectrolyte in solution with low molecular weight salt: small angle neutron scattering measurements
1986
Small angle neutron scattering measurements have been carried out on the tetramethylammonium salt of the polystyrenesulfonic acid withDP w =310 and 1060 in water solution with tetramethylammonium chloride with ionic strength between 0.02 M and 1.0 M. The scattering curves in the scattering vector range 0.05 nm−1≤Q≤1.8nm−1 have been fitted using the form factor of a worm-like chain of finite thickness. The conformational parameters mean square radius of gyration, statistic chain element, mass per unit length and mean square radius of the cross-section have been determined experimentally and used for describing the conformation of the coils. By these molecular weights and ionic strengths, exc…