•Binary mixtures of DBN with AcOH are strongly exothermic and highly non-ideal.•Superbase character of DBN, known in aqueous solution, is retained in the non-aqueous mixtures.•The partial molar ...excess enthalpy xAcOHHAcOHE dominates HE.•AcOH reacts with AcO− anionsto form diacetatohydrogenate(I) anions, H(OAc )2−.
Isothermal titration calorimetry (ITC) experiments were performed for investigation of binary mixtures comprised of the Brønsted superbase DBN with hydrogen ethanoate (AcOH). The heat of mixing (HE) profile was recorded at (343.15 ± 0.1) K and fitted with a 5-parameter Redlich-Kister (RK) polynomial. RK fit parameters were subsequently used to quantify partial molar heats of mixing, xiHiE, for each component i. ITC-based complexometric titration data for the binary mixtures were recorded separately in methyl isobutyl ketone (mibk) and dodecane, to investigate the energetics of non-random clustering phenomena. Variable temperature 1H-NMR in combination with ATR-FTIR spectroscopic analyses were employed in parallel for elucidation and verification of liquid state ion speciation. These investigations reveal a strongly non-ideal system, and indicate “superbase” character of DBN is preserved for specific compositions where stoichiometric ionic liquids (ILs) form. Available ion speciation has been found to include DBN-H+, AcO− as well as μ2-hydrogen-bridged, hydrogen-bonded homoassociate anions, of the type H(OAc)2−, with double liquid salt formation characterising various compositions based on spectroscopic determinations.
A new windows-based, user friendly program (ProMCC) for (i) the determination of metal complexation parameters (ligand concentration (L) and conditional stability constants (K′)) and for (ii) ...theoretical simulation of metal complexometric titration, assuming discrete ligand model, is developed. Although primarily intended for treatment of experimental data obtained either by anodic stripping voltammetry (ASV) or competitive ligand exchange adsorptive cathodic stripping voltammetry (CLE-AdCSV), it could manage titration-type data of other techniques (e.g. ISE, sorption isotherm). Currently, the program is capable to process (fit and/or simulate) titration data up to three discrete ligand classes. Procedure for adjustment of “true” analytical sensitivity incorporated in ProMCC was found to provide reasonably good estimates of sensitivity either for one-ligand or two-ligand system. The particular feature of ProMCC is that it incorporates two complementary fitting methodologies: (1) a non-linear fitting of conventional linearized transformations (e.g. Ružić/Van Den Berg, Langmuir/Gerringa) and (2) a “complete complexation model” — a matrix based optimization of mass balance equations. Comparison test of different non-linear fitting modes and titration types revealed that a slight underestimation of ligand concentration and overestimation of conditional stability constant may occur if titration is performed in logarithmic mode, mainly due to unfavorable noise distribution. An advantage of implemented “complete complexation model” fitting mode is that it allows simultaneous analysis of titrations obtained at multiple detection windows as unified dataset (multi-detection window approach), providing complexation parameters for up to three ligand classes. A new alternative “RAL-approach” in analyzing complexometric titrations obtained at multiple detection windows for copper–salicylaldoxime (Cu–SA) system is suggested. It assumes that the analytical sensitivity is changing along the titration curve respecting the true speciation of Cu–SA in sample. An adapted empirical equation for calculation of relative intensity (RAL) is proposed. Flexibility in adjusting parameters, immediate graphical feedback and visualizations make ProMCC handy for treatment of large set of experimental data, and a tool for research in refinement of the methods of metal complexing capacity determination which is continuously improving.
•A new user-friendly tool for analysis of complexometric titration data is developed.•Non-linear and “complete complexation model” fitting modes were incorporated.•An efficient method for correction of true sensitivity was validated.•Simultaneous analysis of multiple analytical windows (CLE-AdCSV) as unified dataset.•An alternative “RAL-approach” for Cu–SA system is proposed.
Reactions in the Na
2
MoO
4
–ZrOCl
2
–ErCl
3
–H
2
O system at 20°C were studied by the method of residual concentrations. The insoluble substance formed in this system was investigated by ...physicochemical methods (XRD, IR spectroscopy, thermal analysis).
Controlled dispersion as generated in flow injection analysis (FIA) essentially permits an infinite variety of known compositional gradients. Using this unique advantage of FIA, the stability ...constants of metal complexation are calculated by injecting an aliquot of metal solution into the flow of ligand solution in a single-line manifold. While the ligand dilution is negligible, the concentration gradient of injected metal ion can be calculated from the dispersion pattern which is calibrated previously using a dye solution. To show the simplicity, versatility and ease of instrumental setup over approaches based on the classical titration, the method was applied to determine stability constants of murexide with several metal ions. The SQUAD computer program was used for fitting the predefined complexation model to the spectral-mole ratio data. The proper selection of the chemical model was verified by the determination of the number of absorbing species by using a singular value decomposition of each data set. The stability constants obtained for murexide and metals including Cu2+,Cd2+, Pb2+, Ca2+ and Co2+ are 4.35, 4.27, 4.50, 2.55 and 2.57, respectively. The formation constants determined here are in good agreement with those previously reported and with those obtained from conventional batch titrations. The main advantage over the classical batch titration method is that by utilizing just one injection per sample, the proposed method reduces experimental error by reducing the experimental steps needed to obtain the required spectral-mole ratio data. The details of the proposed method are discussed.
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•A new continuous flow titration for metal complexation is developed.•Dispersion pattern is calibrated using controlled dispersion in FIA.•The spectral-mole ratio data obtained by just two injections into flow per sample.•The suggested method has been applied for complexation study of murexide-transition metals ions.•PCA is used for determination of number of light absorbing species.
X-ray diffractograms of lathanide cation exchanged benonites.
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•REE-exchanged bentonites were prepared from Ca-bentonite by ion exchange.•The La3+-, Ce3+-, and Gd3+-bentonite, the ...sorbed ion amount was higher than the CEC.•In case of lanthanum-bentonite, the rare earth quantity is as high as 136% of CEC.•The iron(III) content of lanthanum bentonite is less than that of the original Ca-bentonite.
The interaction between Lanthanides (Ln)- ions and Ca-bentonite and the structural changes accompanying were studied. Ln-exchanged bentonites were prepared from Ca-bentonite (Istenmezeje, Hungary) by ion exchange in three consecutive washings with lanthanide solutions. Scanning Eletronmicroscopy Energy Dispersive X-ray spectroscopy (SEM-EDX) studies showed even distribution of Lns and other components of bentonite. The natural bentonite and the lanthnide exchanged bentonites were characterized by X-ray diffraction (XRD), which revealed the same mineral composition, and the increase of the basal spacing of montmorillonite from 1.465 (Ca2+) to 1.577nm (REE3+). The d001 basal spacing of lanthanide montmorillonite increases as the ion radius of the lanthanide cation increases. The Fe3+, and Lns3+ amount on the bentonite were determined by X-ray-fluorescence spectrometry (XRF) elemental analysis. The amount of exchanged Lns were determined by washing the Ln-bentonite with 1M ammonium-acetate, and measuring the amount of Ln released, using inductively coupled plasma optical emission spectrometry (ICP-OES). In most Ln-bentonites, the quantity of the exchanged Ln ions was about 80–90% of the cation exchange capacity (CEC) of the bentonite. In case of some lanthanides bentonite (La3+, Ce3+, and Gd3+), however, the sorbed quantity of lanthanum ions was higher than the cation exchange capacity. In case of lanthanum-bentonite, the lanthanide quantity is as high as 136% of CEC. Moreover, the iron(III) content of lanthanum bentonite is less than that of the original Ca-bentonite. Mössbauer spectra of the La-, Ce-, and Gd-exchanged samples at 78K revealed an unexpected magnetically split component that was absent from the Ca-bentonite. This component may belong to interlayer Fe. This iron can be released from the octahedral positions crystal lattice.
Soil monitoring and research often requires a comparison of laboratory data generated by diverse instruments and in different laboratories to demonstrate the reliability and accuracy of the results. ...The outcomes of this work highlight a performance comparison among different analytical methods for the determination of calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), in soil. Five soil samples were used for analytical methods comparison, corresponding to an argentine agricultural soil interlaboratory, and four soil samples from the Pampa region of Argentina were used for analytical application of the instrumental methods. The results obtained with flame atomic absorption and emission spectrometry (FAAS-FAES) and microwave-induced plasma optical emission spectrometry (MIP OES) were compared to those obtained by conventional analytical methods as complexometric titration and flame photometry. As there were no significant differences between classical methods with instrumental ones, FAAS-FAES and MIP OES were validated following criteria based on international guidelines. Accuracy, precision, linearity, limits of detection and quantification, sensitivity, analytical sensitivity, and working range were evaluated. The results established the satisfactory performance of FAAS-FAES and MIP OES for exchangeable cations. MIP OES is an efficient alternative to FAAS-FAES, with wide linear dynamic range, which is advantageous concerning to the concentrations in which these exchangeable cations are found in soils, avoiding sample dilutions. The most remarkable advantage of MIP OES is the low running costs as it does not use flammable and toxic gases. Due to its benefits MIP OES could be recommended as the main analytical method for exchangeable cations determination.
Daclatasvir dihydrochloride (DAC) is a drug used to treat hepatitis C virus (HCV) infection. In this study, an ionophore-based nanosphere emulsion was made of tricresyl phosphate (TCP) as the oil ...phase that is dispersed in water using Pluronic F-127 as an emulsifying agent. The nanospheres, consisting of the oil phase TCP, were doped with sodium tetraphenyl borate (Na-TPB) as a cation-exchanger and dibenzo-18-Crown-6 (DB18C6) as an ionophore (chelating agent) for DAC. The nanosphere emulsion was employed as a titrant in the complexometric titration of DAC (the analyte), and the DAC-selective electrode (ISE) was used as an indicator electrode to detect the endpoint. In the sample solution, DAC2+ ions diffused into the emulsified nanospheres, replaced Na+ from the ion exchanger (Na-TPB), and bonded to the ionophore (DB18C6). The DAC-selective nanospheres were successfully utilized to determine DAC in various samples, including standard solutions, commercial tablets (Daclavirocyrl®), serum, and urine. The method exhibited a linear dynamic range of 81.18 µg/mL to 81.18 pg/mL (10−4 to 10−10 M), achieved high recovery values ranging from 99.4% to 106.5%, and displayed excellent selectivity over similar interfering species (sofosbuvir and ledipasvir). The proposed method offers a new approach to determine the drug species (neutral, anionic, and cationic) without the requirement of water-soluble ligands or pH control.
A simple, low-cost and portable field test kit based on colorimetry with detection by naked eye was developed for determination of magnesium content in natural rubber latex (NRL). The miniaturized ...complexometric titration between Mg2+ and EDTA without any masking agent was a key reaction in this development, which was designed according to the concept of green chemistry by reduction of waste generation and chemical and time consumption. The system enabled quantification of magnesium content in NRL at low concentration with the detection limit being <50 mg L−1, small sample volume uptake (0.18 g, sampling by a small spoon) and use of <1.5 mL reagent volume which was >70 times less than that applied in the conventional method. Moreover, with the presence of potential interference ions, greater selectivity towards magnesium was observed. Furthermore, the reagents used in our developed test kit were stable for >6 months at room temperature. The results obtained on real samples were in agreement with those obtained from the conventional complexometric titration (ISO 17403: 2014(E)) method. The proposed technique provides a low-cost, rapid, simple, selective and on-site analysis of magnesium content in NRL.
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