Search

In a recent study, we have used phage display screening to identify peptide motifs with strong and selective affinity to bind to the surfaces of gypsum, an inorganic mineral of high abundance in geo(bio)chemical environments and large‐scale industrial use for construction purposes. The goal of the present work was to investigate the influence of such engineered peptides on the formation of gypsum crystals under different conditions. To establish a holistic picture, the previously discovered multi‐stage mineralization pathway of gypsum was scrutinized in detail by a combination of complementary characterization techniques, including potentiometric titration and cryogenic transmission electron microscopy. The results provide clear evidence that the added peptide interferes with practically all precursor and intermediate species on the way from dissolved ions to solid crystals. Key to this multifunctional behavior is the self‐assembly of the peptides to filamentous colloidal aggregates in the presence of calcium ions, which depends on peptide molecular weight and related changes in secondary structure formation. Overall, the findings made in this work highlight the potential of biotechnological selection techniques for the design of advanced concepts for crystallization control, including supramolecular peptide self‐assembly as a principle known from natural biomineralization and of utmost value for bioinspired material science. [ABSTRACT FROM AUTHOR]

A simple fabrication route for an all-solid-state carbon paste Cu(II)-selective potentiometric sensor on the basis of composite sensing layer consisting of PbS microparticles, graphite (G), multi-walled carbon nanotube, and paraffin oil has been propounded. Optimization studies for sensing composite layer signified that the composite contained 10 mg PbS, 10 mg MWCNT, 60 mg G, and 20 mg PO exposed the most promising potentiometric performance properties. The sensor displayed a stable and selective linear response to Cu(II) ions in the concentration range of 1.0 × 10−6–1.0 × 10−2 M (R2 = 0.9992) with an average potential change of 30.2 mV/decade. Detection limit, response time, and life-span of the sensor were determined as 5.0 × 10−7 M, 15 s, and 3 weeks, respectively. The fabricated sensor was successfully used in practical applications, serving as an indicator electrode to determine the end-point of Cu(II) titrations and to measure Cu(II) content in Cu(II)-spiked tap water samples. [ABSTRACT FROM AUTHOR]

Abstract A modified carbon paste sensor based on N,N′-(((ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(pyridine-2-amine; BPA Schiff base as Cr(III) selective carrier was fabricated and studied in this work. The proposed sensor homogenization and mechanism of action was studied by infra-red (IR) and scanning electron microscope (SEM) with energy dispersive X-ray (EDX) tools. The sensor covered 1.0 × 10−7–1.0 × 10–1 mol L−1 linear range and a detection limit of 7.22 × 10–8 mol L−1 for Cr(III) with 20.17 ± 0.13 mV decade−1 Nernstian slope. 5 s was the response time of the prepared sensor and it was reproducible and stable for 3 months. The working pH range was 3.3–6.0 and it also works well to determine Cr(III) ion in presence of water miscible solvents up to 12.5% content of the methanol and 17.5% of ethanol. The electrode’s selectivity was studied using separate and mixed solution methods for selectivity coefficients determination and the sensor showed good selectivity relative to a variety of metal ions (selectivity coefficients = 1.01 × 10−5–8.57 × 10−3). In addition, the practical analysis value of the sensor was demonstrated by measurement of Cr(III) quantitatively in mineral water, supplement and also as an indicator electrode in Cr(III) against EDTA potentiometric titration with good reproducibility (RSDs of 0.91–2.15%).

A modified carbon paste sensor based on N,N′-(((ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(pyridine-2-amine; BPA Schiff base as Cr(III) selective carrier was fabricated and studied in this work. The proposed sensor homogenization and mechanism of action was studied by infra-red (IR) and scanning electron microscope (SEM) with energy dispersive X-ray (EDX) tools. The sensor covered 1.0 × 10−7–1.0 × 10–1 mol L−1 linear range and a detection limit of 7.22 × 10–8 mol L−1 for Cr(III) with 20.17 ± 0.13 mV decade−1 Nernstian slope. 5 s was the response time of the prepared sensor and it was reproducible and stable for 3 months. The working pH range was 3.3–6.0 and it also works well to determine Cr(III) ion in presence of water miscible solvents up to 12.5% content of the methanol and 17.5% of ethanol. The electrode's selectivity was studied using separate and mixed solution methods for selectivity coefficients determination and the sensor showed good selectivity relative to a variety of metal ions (selectivity coefficients = 1.01 × 10−5–8.57 × 10−3). In addition, the practical analysis value of the sensor was demonstrated by measurement of Cr(III) quantitatively in mineral water, supplement and also as an indicator electrode in Cr(III) against EDTA potentiometric titration with good reproducibility (RSDs of 0.91–2.15%). [ABSTRACT FROM AUTHOR]

Chitosan is a biopolymer that can be subjected to a variety of chemical modifications to generate new materials. The properties of modified chitosan are affected by its degree of deacetylation (DDA), which corresponds to the percentage of D-glucosamine monomers in its polymeric structure. Potentiometric titration is amongst the simplest, most readily available, and most cost-effective methods of determining the DDA. However, this method often suffers from a lack of precision, especially for modified chitosan resins. This is in large part because the equation used to calculate the DDA does not consider the molecular weight of the chemically modified monomeric units. In this paper, we introduce a new equation that is especially suited for modified chitosan bearing three different types of monomers. To test this equation, we prepared naphthalene-chitosan resins and subjected them to potentiometric titration. Our results show that our new equation, which is truer to the real structure of the polymeric chains, gives higher DDA values than those of the routinely used equations. These results show that the traditional equations underestimate the DDA of modified chitosan resins. [ABSTRACT FROM AUTHOR]

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this study was to synthesize a series of unnatural fatty acid derivatives, which have been identified as possessing distinctive properties and potential as new drug candidates. In light of the aforementioned considerations, it is imperative that the physicochemical profiles of these derivatives and their analogues be evaluated prior to the commencement of clinical trials, with a view to ascertaining their pharmacokinetic properties. In order to gain a deeper understanding of this phenomenon, a series of experimental and theoretical studies have been conducted. The pKaexp values of these derivatives were determined for the first time by potentiometric titration. These derivatives, and in particular compounds C-E, display satisfactory physicochemical properties and medicinal chemistry. As a consequence of the related prediction studies, it was observed that the molecules A1-B violated the Lipinski rule by only one criterion, whereas the compounds C-E did not violate it at all. With the exception of compounds A1-A3, compounds B-E exhibit good oral bioavailability. All compounds demonstrated acceptable toxicity profiles, although further in vivo and in vitro laboratory studies are recommended to provide more detailed insights. Furthermore, all molecules were identified as bioactive protease and enzyme inhibitors. [ABSTRACT FROM AUTHOR]

Potentiometric titration in a fast and simultaneously high-resolution modality was proposed for the identification and quantification of protolytic groups of variable strength at the surface of primary soil particles. The method is implemented by titrimetric data processing as multicomponent spectra (pKa spectrotitrimetry). Due to the high resolution, the error of acidity-constant assessment (3–5%) is lower, compared to existing approaches; due to the fast titration, the effect of soil hydrolysis is minimized. The soil profiles for acidic Retisols (podzolic soils)—under a spruce crown and in the intercrown space—were studied. These soils, which have similar bulk properties and genesis but developed under different plant covers, were distinguished by pKa spectral features at 4–5; 5.5–6.5; 6.5–8.5; 7.5–8.5; and 9–10, as well as total group concentrations. Differences in acidic and basic-group distribution (carboxyl groups, amorphous aluminosilicates, carbonate species, amino groups, soluble (poly)phenolic compounds, phospholipids) and Al and Fe complex compounds within the same soil profiles and between two Retisols were found and quantified. The acidity constants and group concentrations found by pKa spectrotitrimetry were compared with conventional soil-composition indicators (total organic carbon, oxalate-soluble Fe and Al, and phosphorus), using principal component analysis. The main correlations are between the concentrations of oxalate-soluble Al and groups with pKa values of 5.0–6.5 and 8.5; oxalate-soluble Fe and pKa values of 9.0–10.0; and P2O5 and pKa values of 4.0–6.0 and 6.5–8.5. The method provides a set of major acidity values without a priori information on a soil sample and can be used for screening and identifying similar soils. [ABSTRACT FROM AUTHOR]

Cyclopeptides hold significant relevance in various fields of science and medicine, due to their unique structural properties and diverse biological activities. Cyclic peptides, characterized by intrinsically higher conformational order, exhibit remarkable stability and resistance to proteolytic degradation, making them attractive candidates for developing targeted drug delivery systems. The aim of this work is to elucidate the unique coordination properties of the multi‐His cyclic peptide with c(HDHKHPHHKHHP) sequence (HDCP – heterodomain cyclopeptide). This peptide, indeed, is able to form homo‐ and hetero‐dinuclear complexes in a wide pH range, being thus a good chelator for Cu(II) ions. Herein, we present the results of a combined study, involving potentiometric, spectroscopic (UV–Vis, CD, and EPR), and computational investigations, on its coordination properties. To better understand the interaction pattern with Cu(II) metal ions, two other peptides, each one bearing only one of the two binding domains of HDCP are also considered in this study: c(HDHKHPGGKGGP) = CP1, c(GKGGKPHHKHHP) = CP2, which share sequence fragments of HDCP and allow separate investigations of its coordination domains. [ABSTRACT FROM AUTHOR]

Schematic diagram of the whole process for detecting sulfur-containing components in lithium-sulfur batteries, including graded leaching, efficient oxidation and precise quantitative detection. [Display omitted] • A highly effective approach for the graded leaching and precise quantitative detection techniques of sulfur-containing components within Li-S batteries has been successfully developed. The total detection rate of this method for sulfur-containing components in Li-S batteries exceeds 99 %. • Clarify that the presence of lithium polysulfide in the electrolyte after discharge is the main factor for restricting the full utilization of Li-S batteries' capacity, and propose targeted improvement measures. • This study offers a considerably refined and comprehensive methodology for the capacity fading and failure mechanisms assessment of high-energy-density Li-S batteries. Lithium-sulfur (Li-S) batteries are a strong contender for the new-generation battery system to meet the growing energy demand due to their significantly high energy density (2600 Wh/kg) and cost-effectiveness. However, the practical operating conditions yield an initial capacity of less than 80 % of the theoretical capacity, resulting in a limited lifespan and hindering broader application. What's worse, current mechanism, especially the evolution process of sulfides for the initial capacity degradation is not clear due to the practical difficulties of effective separation and detection of sulfur-containing components. Herein, we have developed an instrumental analysis method enabling graded leaching and quantitative determination of sulfur-containing components. This technology achieves a detection precision surpassing 99.11 %, addressing the inherent deficiency in calculating sulfur-containing components using the decrement method. Applying this method reveals that the presence of lithium polysulfides in the electrolyte (26.34 wt%) after discharging is the primary factor causing insufficient capacity utilization in Li-S batteries. This work not only demonstrates the unique behavior of Li-S batteries at high sulfur loading but also provides a systematic evaluation method to guide further research on high-energy-density batteries, and provides theoretical and technical support to promote the development of high-energy, long-life Li-S batteries. [ABSTRACT FROM AUTHOR]

The suitability of various nitrogen, sulfur, oxygen, and phosphorus compounds as complexing agents in a silver electrolyte was examined by using potentiometric titration under practical conditions. The setup consisted of three electrodes to measure the pH and the activity of the silver ions simultaneously. Different ratios of silver to complexing agent from 1:10 to 1:1 at a constant ionic strength of 0.2 mol/L were investigated. The type of the complexes and their corresponding critical stability constants were evaluated by fitting the measured data using a self-developed algorithm. The pH and Nernst potential curve were calculated for the assumed complexes based on the law of mass action to find the best approximation. The correct definition of the occurring species is challenging and can lead to significant changes in the calculation of stability constants. For this reason, the measured silver potential curves were primarily used for the rating of the complexing agents. An evaluation of the measurements shows that the donor atom of the complexing agent and its ligand field strongly affected the stability and type of the complexes. Only a few complexing agents were found to be suitable for use in the cyanide-free silver electrolyte. [ABSTRACT FROM AUTHOR]

Objective: The determination of pKa values holds paramount importance in the field of medicinal chemistry, serving as a critical parameter for understanding the ionization behavior of pharmaceutical compounds. This study employs potentiometric titration as a precise method to elucidate the pKa values of diverse molecules. The experimental methodology involved a carefully controlled titration setup, utilizing a pH meter to monitor the titration curve and identify inflection points corresponding to the dissociation of acidic or basic functional groups. Methods: Potentiometric titration was conducted using a standardized protocol. Each compound was titrated with a titrant solution of known concentration, and pH measurements were recorded throughout the titration process. The titration curves were analyzed to determine the pKa values of the compounds based on the points of inflection. Results: The potentiometric titration method successfully provided accurate and reproducible pKa values for the studied compounds. The pKa values for the active ingredients Diclofenac, Clavunate potassium, and Levetiracetam are 3.31, 3.53, and 11.3, respectively. Compounds with pKa values below 7 are unlikely to be significantly protonated at physiological pH, which is approximately 7.4. Conclusion: The study underscores the critical role of pKa values in guiding medicinal chemistry efforts. The potentiometric titration method proved to be an effective tool for determining these constants, contributing essential data for rational drug design. The correlation between pKa values and pharmacokinetic properties emphasizes the relevance of this approach in optimizing drug candidates for enhanced therapeutic outcomes. [ABSTRACT FROM AUTHOR]

The authors propose a way of determining the solubility product (SP) of poorly soluble copper(II) salts by minimizing the functional discrepancy between experimental and calculated curves of precipitation potentiometric titration with a copper indicator electrode. The procedure is based on the solubility product being a parameter of the calculation curve, and the minimum of the discrepancy functional is observed in the immediate vicinity of the true SP value. The values of the solubility product of coppe(II) oxalate and tartrate in water at temperatures of 21–22°C are determined. [ABSTRACT FROM AUTHOR]

Copyright of China Synthetic Fiber Industry is the property of Sinopec Baling Petrochemical Company and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The pKa values of propanolamine hydrochloride (PAMH) and poly(allylamine hydrochloride) (PAAMH) in concentrated solutions were determined by both Fourier transform infrared spectroscopy (FT-IR) titration and classical potentiometric (POT) titration and compared. Starting with the respective fully protonated forms PAMH and PAAMH and increasing the pH value by sodium hydroxide addition in situ attenuated total reflection FT-IR (ATR FT-IR) spectra on PAMH and PAAMH solutions show the variation of diagnostic infrared (IR) bands. From the decrease of the most intense δ(NH3+) band the dissociation process of the NH3+ groups could be followed. Thereby, from the respective normalized band area A the dissociation degree αIR of the ammonium groups could be determined. Plotting pH versus αIR and fitting this curve by a modified Henderson–Hasselbalch function pH = pKa + B log (αIR/1 – αIR) the parameters pKa and cooperativity factor B were obtained. pKa values from FT-IR titration were qualitatively in line with respective pKa values from POT titration. Quantitative systematic pKa deviations between polyelectrolyte (PEL) and respective monoelectrolyte and the tentative effects of PEL molecular weight, ambient ionic strength, and titration concept (FT-IR and POT) are discussed based on classical models of weak PEL. Graphical abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

Abstract Three smart carbon paste electrodes were fabricated to quantify dorzolamide hydrochloride DRZ, including conventional carbon paste I, modified carbon paste embedding Silica II, and modified carbon paste embedding β-cyclodextrin III. This study is based on the insertion of DRZ with phosphomolybdic acid to create an electroactive moiety dorzolamide-phosphomolybdate ion exchanger using a solvent mediator dibutyl phthalate. The three constructed carbon paste electrodes displayed Nernstian responses and linear concentration ranges with lower detection limits. The vital performance of the created electrodes was verified in relation to various parameters. The electrodes enhance the selective determination of DRZ in the presence of inorganic ions, a co-formulated drug in the dosage form timolol maleate, and the excipient benzalkonium chloride. The modified carbon paste electrode including Silica was utilized to detect DRZ in ophthalmic eye drop form utilizing the direct calibration curve and potentiometric titration methods. Satisfactory findings were achieved by comparing them to other reported methods.

The dissociation constants of Schiff bases, (E)-1-[(2,4-dichlorophenylimino)methyl]naphthalen-2-ol, (E)-1-[(2-chloro-4-nitrophenylimino)methyl]naphthalen-2-ol, (E)-1-[(2,4-dimethoxyphenylimino)methyl]naphthalen-2-ol, and their stability constants with the copper(II) metal ion were determined potentiometrically. The experimental conditions were arranged to achieve coordination in aqueous-ethanol solutions [ethyl alcohol (30%) and water (70%) at 25.0±0.1°C and a constant ionic strength of 0.1 mol/dm3 NaCl]. It was detected that each ligand has two dissociation constants, which are associated to the protonated imine nitrogen and the hydroxyl group. The dissociation constants of these ligands and their stability constants of Cu(II) complexes were computed and discussed in relation to their structural configuration, substituents and basicity. The difference in basicity or acidity of these Schiff base ligands were explained in terms of the inductive effect, resonance and steric effect. Keto-enol tautomerism was discussed in the context of hydrogen bonding, basicity of the imine group and hydrogen acidity of the hydroxyl group; a zwitterionic tautomer might develop as well. The chemical species existing in the solution at experimental conditions used were presented with speciation diagrams. The SUPERQUAD program was used to compute dissociation and stability constants as well as the speciation diagrams. The aims of this study was to determine potentiometrically the dissociation constants of the Schiff base ligands used and the stability constants of their complexes with Cu(II). [ABSTRACT FROM AUTHOR]

The purpose of this experiment was to study the effect of oryzanol on determination of acid value in forage rice bran oil. Four forage rice bran oil from market or extracted by forage rice bran were selected and content of ooryzanol in oil were determination by HPLC method. Three method, thymol phthalein indicator, Alkali Blue 6B indicator and potentiometric titration, were used to determine acid value in forage rice bran oil. The treatment group were selected edible rice bran oil and forage soybean oil. Then, different quantitative ooryzanol were added to the forage rice bran oil and blank Solvent. The acid value of these oid were determined by thymol phthalein indicato and potentiometric titration individually. The results showed that: ① Alkali Blue 6B indicator was un applicable on determination of acid value in forage rice bran oil. ② The apparent acid value by thymol phthalein indicator titration was the content of oryzanol increased linearly with the content of oryzanol increasing. ③ The content of oryzanol had no significant influence on the acid value by potentiometric titration. ④ Oryzanol would caused a second jump around pH 12 during potential titration. ⑤ The volume of the titrated liquid was significantly linear with the content of oryzanol in both methods. ⑥ Using the solvent with the same content of oryzanol as a blank control, the acid valence determined by thymol phthalein indicator method was no different from the potential titration method. ⑦ The precision of potential titration was higher than that of thymol phthalein indicator. In sum‐ mary, potential titration should be preferred for determination of acid value in forage rice bran oil, and thymol phthalein indicator requires a solvent containing the same content of oryzanol as a blank control. [ABSTRACT FROM AUTHOR]

Chitosan is a linear biopolymer composed of D-glucosamine and N-acetylglucosamine units. The percentage of D-glucosamine in the polymeric chain can vary from one sample to another and is expressed as the degree of deacetylation (DDA). Since this parameter has an impact on many properties, its determination is often critical, and potentiometric titration is a common analytical technique to measure the DDA. Cross-linking with glutaraldehyde is one of the most explored modifications of chitosan; however, the determination of the DDA for the resulting reticulated chitosan resins can be challenging. In this paper, we report a new, rapid, and efficient method to determine the DDA of glutaraldehyde-cross-linked chitosan resins via HPLC. This method relies on the use of 2,4-dinitrophenylhydrazine (DNPH) as a derivatizing agent to measure the level of reticulation of the polymer (LR) after the reticulation step. In this study, we prepare three calibration curves (with an R2 value over 0.92) for three series of reticulated polymers covering a large range of reticulation levels to demonstrate that a correlation can be established between the LR established via HPLC and the DDA obtained via titration. The polymers are derived from three different chitosan starting materials. These standard calibration curves are now used on a routine basis in our lab, and the HPLC method has allowed us to change our DDA analysis time from 20 h to 5 min. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] This study presents a comprehensive community data-driven surface complexation modeling framework for simulating potentiometric titration of mineral surfaces. Compiled community data for ferrihydrite, goethite, hematite, and magnetite are fit to produce representative protolysis constants that can reproduce potentiometric titration data collected from multiple literature sources. Using this framework, the impact of surface complexation model type and surface site density (SSD) on the fit quality and protolysis constants can be readily evaluated. For example, the non-electrostatic model yielded a poor data fit compared to diffuse double layer model and constant capacitance models due to the absence of known surface charge effects. Regardless of the choice of iron oxide mineral, pK a1 decreased with increasing SSD while the opposite tendency was observed for pK a2. This newly developed framework demonstrates a method to reconcile community data-wide potentiometric titration data using Findable, Accessible, Interoperable, Reusable data principles to produce mineral protolysis constants that improve robustness of surface complexation models for applications in metal sorption and reactive transport modeling. The framework is readily expandable (as community data increase) and extensible (as the number of minerals increase). The framework provides a path forward for developing self-consistent, comprehensive, and updateable surface complexation databases for surface complexation and reactive transport modeling. [ABSTRACT FROM AUTHOR]

This work concerns the electrochemical behaviors of La3+ on W electrodes in the LiCl-KCl-LaCl3 molten salt at 723-813 K. The results show that La3+ is reduced at about -2.04 V(vs. Ag/AgCl) on inert W electrode, which is a one-step three-electron transfer process. The redox potential, Gibbs free energy and activity coefficient of La3+/La are calculated by open circuit chronopotentiometry on W electrode in LiCl-KCl-LaCl3 molten salt. Potentiometric titration was used to study the reaction of lanthanum chloride with oxide ions. The titration curve shows that the precipitate of oxide is LaOCl. According to the experimental apparent electrode potential, activity coefficient and relevant thermodynamic data, the phase diagram of La-O stability was drawn. The stable phase diagram of E-pO2- shows that LaOCl is the most stable compound in the range of higher O2- concentration at 723 K.

Chitosan is a biopolymer that can be subjected to a variety of chemical modifications to generate new materials. The properties of modified chitosan are affected by its degree of deacetylation (DDA), which corresponds to the percentage of D-glucosamine monomers in its polymeric structure. Potentiometric titration is amongst the simplest, most readily available, and most cost-effective methods of determining the DDA. However, this method often suffers from a lack of precision, especially for modified chitosan resins. This is in large part because the equation used to calculate the DDA does not consider the molecular weight of the chemically modified monomeric units. In this paper, we introduce a new equation that is especially suited for modified chitosan bearing three different types of monomers. To test this equation, we prepared naphthalene–chitosan resins and subjected them to potentiometric titration. Our results show that our new equation, which is truer to the real structure of the polymeric chains, gives higher DDA values than those of the routinely used equations. These results show that the traditional equations underestimate the DDA of modified chitosan resins.

Potentiometric titration in a fast and simultaneously high-resolution modality was proposed for the identification and quantification of protolytic groups of variable strength at the surface of primary soil particles. The method is implemented by titrimetric data processing as multicomponent spectra (pKa spectrotitrimetry). Due to the high resolution, the error of acidity-constant assessment (3–5%) is lower, compared to existing approaches; due to the fast titration, the effect of soil hydrolysis is minimized. The soil profiles for acidic Retisols (podzolic soils)—under a spruce crown and in the intercrown space—were studied. These soils, which have similar bulk properties and genesis but developed under different plant covers, were distinguished by pKa spectral features at 4–5; 5.5–6.5; 6.5–8.5; 7.5–8.5; and 9–10, as well as total group concentrations. Differences in acidic and basic-group distribution (carboxyl groups, amorphous aluminosilicates, carbonate species, amino groups, soluble (poly)phenolic compounds, phospholipids) and Al and Fe complex compounds within the same soil profiles and between two Retisols were found and quantified. The acidity constants and group concentrations found by pKa spectrotitrimetry were compared with conventional soil-composition indicators (total organic carbon, oxalate-soluble Fe and Al, and phosphorus), using principal component analysis. The main correlations are between the concentrations of oxalate-soluble Al and groups with pKa values of 5.0–6.5 and 8.5; oxalate-soluble Fe and pKa values of 9.0–10.0; and P2O5 and pKa values of 4.0–6.0 and 6.5–8.5. The method provides a set of major acidity values without a priori information on a soil sample and can be used for screening and identifying similar soils.

Three smart carbon paste electrodes were fabricated to quantify dorzolamide hydrochloride DRZ, including conventional carbon paste I, modified carbon paste embedding Silica II, and modified carbon paste embedding β-cyclodextrin III. This study is based on the insertion of DRZ with phosphomolybdic acid to create an electroactive moiety dorzolamide-phosphomolybdate ion exchanger using a solvent mediator dibutyl phthalate. The three constructed carbon paste electrodes displayed Nernstian responses and linear concentration ranges with lower detection limits. The vital performance of the created electrodes was verified in relation to various parameters. The electrodes enhance the selective determination of DRZ in the presence of inorganic ions, a co-formulated drug in the dosage form timolol maleate, and the excipient benzalkonium chloride. The modified carbon paste electrode including Silica was utilized to detect DRZ in ophthalmic eye drop form utilizing the direct calibration curve and potentiometric titration methods. Satisfactory findings were achieved by comparing them to other reported methods. [ABSTRACT FROM AUTHOR]

Humic substances—humic acid, hymatomelanic acid, humus acid, and fulvic acid—have been isolated from lignite mined in the Tisulsky deposit of Kansk-Achinsk Basin. The samples obtained are characterized by means of technical and elemental analysis. The content of functional groups is determined by potentiometric titration. For all the acids, the content of carboxyl and hydroxyl groups in the humic substances may be ranked as follows: Ar–OH > Ar–COOH > Alk–COOH. [ABSTRACT FROM AUTHOR]

The potentiometric titration of a carbonate mixture or an acetate solution is a common experiment in analytical laboratories. Typically, a glass electrode combined with a calomel or Ag/AgCl reference electrode is used to locate the equivalence points in neutralization titrations. The dissociation constants of weak acids and bases can be calculated from the pH at the half‐neutralization point. Recently, a new commercial product for measuring pH has been developed. This novel acid–base detection strip is a single‐use sensor that requires neither storage in a preservation liquid nor calibration prior to use. This study examined its suitability for the continuous monitoring of pH changes in potentiometric titrations of carbonate mixtures, acetate solutions, or ammonia solutions. There were no significant differences in the concentrations of solutions tested using a glass electrode and a pH test strip. The pKa, pKb, and pH values determined using the two systems differed by less than 5%. The results confirmed that the pH strips are suitable for continuously monitoring pH changes during neutralization titrations. However, the strips can only be used once. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Diaryliodonium salts are used in organic chemistry, materials science and pharmaceutical chemistry. For the quantitative analysis of diaryliodonium salts, only instrumentally demanding techniques requiring highly skilled operators are available. Surprisingly, no titration method taking advantage of the oxidising ability of diaryliodonium is available in the literature. In the present work, a titration method for the determination of diaryliodonium salts is presented. It is based on the reaction of diaryliodonium species with ascorbic acid, whose excess is subsequently determined by means of iodometric potentiometric titration. Application of the protocol to various diaryliodonium salts revealed the scope and limitations of the method. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Numerous research has investigated the effects of blast furnace slag as a cementitious or substitute cementing material on the characteristics of concrete. Blast furnace slag cement (BFSC) shows promise in the concrete permeability domain, where this extra cementing ingredient enhances the chloride attack resistance of concrete. Four mixtures of BFSC concrete made with 0.5, and 0.6 water-to-cement ratios (w/c) were studied. The effect of using an air-entraining agent (AEA) and a change in the surface of tested samples (top, bottom, and side) on the chloride penetration and its diffusion coefficient has been investigated. The properties of fresh and hardened concrete were determined. This research has its novelty for the first time, where the chloride contents were determined through specimens' top, bottom, and side surfaces using potentiometric titration. The results indicated that the air-entraining agent and w/c ratio had inversely affected the invested concrete properties. The measured total and soluble chloride content at a depth of 20∼30 mm is less than the limits of the corrosion threshold for the three studied surfaces. Also, changes in the w/c ratio, cement content, and AEA affect the diffusion coefficient.

For amphoteric ß-lactam antibiotics, the acid dissociation constant (pKa) is a fundamental parameter to characterize physicochemical and biochemical properties of antibiotics and to predict persistence and removal of drugs. pKa of piperacillin (PIP) is determined by potentiometric titration with a glass electrode. Electrospray ionization mass spectrometry (ESI-MS) is creatively applied to verify the reasonable pKa value at every dissociation step. Two microscopic pKa values (3.37 ± 0.06 and 8.96 ± 0.10) are identified and attributed to the direct dissociation of the carboxylic acid functional group and one secondary amide group, respectively. Different from other ß-lactam antibiotics, PIP presents a dissociation pattern where direct dissociation is involved instead of protonation dissociation. Moreover, the degradation tendency of PIP in an alkaline solution may alter the dissociation pattern or dismiss the corresponding pKa of the amphoteric ß-lactam antibiotics. This work offers a reliable determination of the acid dissociation constant of PIP and a clear interpretation of the effect of stability of antibiotics on the dissociation process.

A new stoichiometric FTIR Base Number (BN) method of significant utility and analytical benefit to the tribology sector has been developed, providing ASTM D4739‐comparable BN results in lieu of titration in a fraction of the time. Thirty‐six new/in‐service oils analysed by both methods were linearly related with a between‐method accuracy of ~±1.0 BN and a within‐FTIR method reproducibility of ~±0.50 BN. Acid pKa differences and the comparative similarity of the FTIR results to HCl titration are discussed, including analytical benefits. It provides a rapid means of producing quality ASTM‐comparable results, taking ~1 min/sample for spectral analysis versus 30–40 min for potentiometric titration. Method protocols are best suited to an open architecture FTIR accessory but can be readily adapted to flow cell equipped FTIRs. As structured, ASTM‐like results are obtained rapidly with a major analytical environmental/maintenance footprint reduction, being ideally suited for in‐service lubricant or research labs analysing 20–50 samples/day. [ABSTRACT FROM AUTHOR]

The effect of ultrasonic treatment on the properties of highly paraffinic oil, its sediments, and raffinates was studied. The oil was processed in an ultrasonic field (field intensity, 18 W/cm2; frequency, 22 kHz; and time, 10 min), and sedimentation was carried out at an ambient temperature of 30°C; the coldfinger temperature was 5°C. The viscosity–temperature parameters of oil were determined using a HAAKE Viscotester iQ rotational viscometer. The microstructure of the sediments was studied using an AXIOLAB.A1 microscope. The concentrations of weak and strong acids in oil, raffinates, and sediments isolated from highly paraffinic oil were determined using a potentiometric titration method. [ABSTRACT FROM AUTHOR]

Calcium and manganese are common ions that pollute drinking water and, therefore, ingestion may seriously harm human health. However, despite its importance, few studies into the synergistic removal of calcium and manganese have been reported. Calcium and manganese have similar chemical properties and, consequently, can be removed by co-crystallization, as the exact crystalline phase formed by this process and the process rate depend on the pH, the dissolved oxygen (DO) content, and the concentrations of the component ions. In this work, we experimentally studied the co-crystallization of Mn and Ca using an automatic potentiometric titrator. We found that the concentration of Mn2+ can be reduced from 3.0 to <0.1 mg/L by the co-crystallization of Mn and Ca at pH 10.5 and a DO content of 8.5 mg/L. In addition, the crystallizations of Ca and Mn are mutually inhibitory; the crystallization process of Mn is obviously divided into two stages: crystal nucleation and crystal growth. Increasing the pH, decreasing the DO content, and decreasing the Mn ion concentration increase the rate of CaCO3 crystallization, whereas the opposite changes increase the rate of Mn crystallization. Furthermore, Mn–Ca co-crystallization leads to the formation of various substances, including single crystals (CaCO3/MnCO3), mixed crystals (CaMnCO3), and Mn oxides (MnxOy/Mn(OH)O). Our findings regarding the effects, precipitation rates, and precipitation mechanisms of Mn–Ca co-crystallization serve as an important guide for the optimization and control of Mn–Ca co-crystallization processes. [ABSTRACT FROM AUTHOR]

A potentiometric investigation has been carried out to disclose the coordination properties of Dacarbazine, 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (abbreviated DTIC) with particular transition metal ions (Zn2+, Cu2+, Ni2+ and Co2+). The coordination of DTIC with these metal ions results in several complexes emerging in solution. The aim of this work is to determine the protonation constants of the DTIC and to show the extent of its coordination with (Zn2+, Cu2+, Ni2+ and Co2+), in other words, establish the stability of the complexes formed between the DTIC and these metal ions by the determination of their stability constants. Experimental environments were organized to attain the coordination and measurements in aqueous solutions at 25±0.1 °C and an ionic background of 0.1 mol dm-3 NaCl. The HYPERQUAD computer program was used to determine both the protonation and stability constants for the ligand and metal-ligand complexes respectively. DTIC has five protonation constants that can be obtained under experimental conditions used; 10.54, 20.15, 26.99, 32.02 and 36.01. The results are interpreted in terms of the basicity of the donor atoms and structural composition of the ligand. All the complexes produced in the solution are exhibited in speciation diagrams. [ABSTRACT FROM AUTHOR]

Chitosan is a linear biopolymer composed of D-glucosamine and N-acetylglucosamine units. The percentage of D-glucosamine in the polymeric chain can vary from one sample to another and is expressed as the degree of deacetylation (DDA). Since this parameter has an impact on many properties, its determination is often critical, and potentiometric titration is a common analytical technique to measure the DDA. Cross-linking with glutaraldehyde is one of the most explored modifications of chitosan; however, the determination of the DDA for the resulting reticulated chitosan resins can be challenging. In this paper, we report a new, rapid, and efficient method to determine the DDA of glutaraldehyde-cross-linked chitosan resins via HPLC. This method relies on the use of 2,4-dinitrophenylhydrazine (DNPH) as a derivatizing agent to measure the level of reticulation of the polymer (LR) after the reticulation step. In this study, we prepare three calibration curves (with an R2 value over 0.92) for three series of reticulated polymers covering a large range of reticulation levels to demonstrate that a correlation can be established between the LR established via HPLC and the DDA obtained via titration. The polymers are derived from three different chitosan starting materials. These standard calibration curves are now used on a routine basis in our lab, and the HPLC method has allowed us to change our DDA analysis time from 20 h to 5 min.

A rapid method for the determination of free acids in chloropalladium acid solution was developed by using an automatic potentiometric titration and composite glass electrode. The results show that the automatic potentiometric titration can accurately distinguish the end points of the reaction of free acid with sodium hydroxide and chloropalladium acid with sodium hydroxide, the maximum jump point of the first step EP1 is the target end point. The recovery of hydrochloric acid is between 85% and 110%, and the relative standard deviation (RSD) is less than 2%. The method is intuitionistic, rapid and accurate. It is suitable for the determination of free acid in chloropalladium acid solution. [ABSTRACT FROM AUTHOR]

Herein, we developed a new pencil graphite ion-selective electrode strategy for the broadly used erectile dysfunction medication, sildenafil citrate (SC, vitamin V), for its automated potentiometry and potentiometric titration profiling in marketed tablets and human urine samples. The method was based on ion-pair complexation between SC and sodium tetraphenylborate (Na-TPB) or phosphotungstic acid (PTA), embedded into a pencil-fabricated graphite sensor electrode coated with poly(vinyl chloride, PVC) matrix, which is pre-plasticized with two different pre-studied plasticizers. The modern fabricated electrodes have a proven fast near-Nernstian response for SC over the concentration range of 1.0 × 10−6 to 1.0 × 10−2 and 1.0 × 10−5 to 1.0 × 10−2 M, with LODs of 6.5 × 10−7 and 5.5 × 10−6 over a pH 3–6 for (SC-TPB)- and (SC-PTA)-based membrane sensors, of O-nitrophenyl octyl ether (O-NPOE) and dioctyl phthalate (DOP), respectively. The selectivity coefficients for different interferents, including many inorganic cations, sugars, and/or nitrogenous compounds, were tested and confirmed. Applications of the proposed method were conducted on the determination of SC in its tablets and urine samples under the proper conditions. The percent recovery values were compared with those obtained by an official method and showed an RSD ≤ 0.3% (n = 5). [ABSTRACT FROM AUTHOR]

Dissociation constants of 2-furancarboxylic and 2-furylacrylic acids and stability constants of their complexes with Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Ho3+, Er3+, and Yb3+ ions were determined in aqueous ethanol solution (5 : 1 by volume) by pH-potentiometric titration. It was found that the complex formation occurs in the pH range of 3.0–6.5, the stability constants of complex compounds increasing with increasing values of the protonation constant of the ligands. Solid complex compounds with 2-furancarboxylic and 2-furylacrylic acids of the compositions (С5Н3О3)3Ln·nH2O and (С7Н5О3)3Ln·nH2O (n = 2–4), respectively, have been synthesized. According to IR spectra, Ln3+ ions are coordinated to acids bidentately by the carboxyl groups. The range of thermal stability of the complex compounds has been determined by the TG/DTG/DSC methods. Spectral-luminescent properties of the complex compounds of 2-furancarboxylic acid with Eu3+ and Tb3+ ions have been studied. [ABSTRACT FROM AUTHOR]

Although bioreduction induced by microorganisms has been considered to play an important role in the chemical and migration behaviors of uranium in nature, the accurate determination of tetravalent uranium reduced by microorganisms is still difficult to achieve. In this work, potentiometric titration via K2Cr2O7 was used to quantitatively determine the microorganism reduced tetravalent uranium (U(IV)) for the first time. By evaluating the influence of microorganism substance content on the titration of U(IV), the appropriate determination range of U(IV) and biomass was confirmed, and U(IV) induced by bioreduction in three microorganisms was determined. With this method, U(IV) of more than 0.12 mg in microorganisms can be quantitatively measured with an accuracy of 2.2% and a precision of 1.3%, which has been established with the premise that the pretreatment biomass and quantity of U(IV) are in an appropriate range. Compared with the estimated values via the changes in hexavalent uranium (U(VI)) concentration in the bioreduction system, the results obtained by this method can more accurately reflect the quantity of U(IV) in microorganisms. This work can help us to better understand the bioreduction behavior of uranium in the environment. [ABSTRACT FROM AUTHOR]

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.

The contents of soap and organic acid in emulsion polymerized styrene-butadiene rubber determined by indicator titration and potentiometric titration in ISO 7781 were compared. The differences between the determination principles and results of the two methods were compared, and the accuracy of the results was investigated by standard addition experiment. The results showed that the results of potentiometric titration and indicator method were consistent. When testing the soap content in emulsion polymerized styrene-butadiene rubber, the indicator method was greatly affected by amine antioxidant and filling oil. But the potentiometric titration method was less affected by amine antioxidant and was not affected by filling oil, so the determination result was more accurate.

Devising a low-cost and effective strategy to reduce Cd contamination of brown rice is critical to achieve the safe production of rice grain for human consumption. Accordingly, here field experiments were conducted at two sites to evaluate the effects of applying humic acid (HA) to foliage twice, at the booting and full heading stage, on diminishing the translocation of cadmium (Cd) into rice grains. Besides measuring the Cd subcellular distribution in the flag leaf and the polysaccharide composition of the cell wall, the latter’s types and concentrations of functional groups were quantitatively analyzed by potentiometric titration and fitted by a surface complexation model. The results demonstrated that applying HA to leaves not only increased the rice yield but also reduced the Cd concentration in brown rice by 35.48–39.74% when using an application rate of just 600 g/ha. The HA treatment augmented Cd fixation in flag leaves, reduced the Cd translocation to rachis and brown rice, and increased the subcellular distribution of Cd in flag leaf cell wall. Furthermore, the Cd concentration in the pectin and hemicellulose 1 of cell wall increased by 33.00% and 25.73%, respectively. Besides those effects, foliar spraying of HA induced a greater abundance of carboxyl, hydroxyl, and amino groups on the cell wall, allowing for more sites to be involved in the binding of Cd, thereby promoting the immobilization of Cd in the flag leaf, and ultimately reducing the remobilization of Cd into the grain. Thus, foliage application of HA may offer a promising and cost-effective tactic for the remediation and continued use of Cd-contaminated paddy soils. Capsule: Foliage application of humic acid promoted the deposition of Cd in the cell wall of rice flag leaf, thereby enhancing the immobilization of Cd and ultimately reducing the remobilization of Cd into the grain

The study of lube oil is useful in scheduled maintenance activity, determining the oil replacement time for engines, to increase the engine life and ensure the maximum performance. Investigation of engine oil can reduce maintenance cost and promises higher design efficiency. Experiments were carried out on a mono cylinder compression ignition engine fueled with diesel-ethanol blended, which is operated at a constant rated speed of 1500 rpm for 100 hours. The lube oil samples were subjected to wear metal tests, chemical and physical tests. The quantity of wear metal in the engine oil was observed using the atomic absorption spectrometer. The total base number and total acid number were measured by the titration method according to ASTM code ASTM D6654 and ASTM2896, respectively. The viscosity was determined using the Stab Viscometer, SVM3000, by the ASTM D445 method at 40oC temperature. Iron and copper concertation was increased with an increase in usage time. However, TBN decreased, and TAN increased with the usage time. Viscosity and density decrease with the increase in usage time. The lube oil shows that the engine can be operated for an extended time with the same lube oil since all the measured parameters are within the limit.