Complexometric Titration Research Articles

Selective Extraction and Determination of Scandium in Industrial Waste (Matte) by the Complexometric Method

In this article, selective extraction and complexometric titration of scandium waste (waste matte) are investigated. Waste matte contains various ions of elements As, Pb, Sb, K, Hg, Fe, Ca, Au, Cd, Na, Si that interfere with the determination of scandium. In a moderately acidic medium, scandium ions form a mixed complex with diantipyrylmethane in the presence of iodide ions, which is well soluble in chloroform. Under these conditions, lanthanides as well as As, Pb, Sb, K, Hg, Fe, Ca, Au, Cd, Na do not form compounds soluble in chloroform and do not interfere with the determination of scandium. Scandium is reextracted with an ammonia solution of EDTA and the determination is completed complexometrically.

Potentiometric determination of Pb2+ ions using hybrid assembly of zinc oxide@polyaniline nanocomposites

ABSTRACT Over the recent years, the detection and determination of level of pollutant in environment have become indispensable. This allows for the adoption of various methods to evade the pollution caused by these toxicant entities. This has enhanced the interest of researchers to develop sustainable sensors to determine the trace level concentration of harmful target species. Although the list of these pollutants is undoubtedly too long, toxic metal ions, like Pb2+ ions beyond certain limit, can severely endanger the whole ecosystem. Therefore, the present study is dedicated toward the development of Pb2+ ion-selective electrode based on the membrane of zinc oxide/polyaniline nanocomposites. Nanocomposite assembly was synthesized using in-situ chemical oxidative polymerization method and characterized using spectroscopic techniques, such as energy‐dispersive spectroscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, etc. The proposed potentiometric sensor exhibits excellent selectivity toward Pb2+ ions with detection limit of 2.239 × 10−6 M, Nernstian slope of 23.31 ± 2.5 mV decade−1 and a wide linear concentration range of 1.0 × 10−5 M to 1.0 × 10−1 M. Moreover, the designed Pb2+ ion-selective electrode was successfully examined for its practical applicability in Pb2+−EDTA complexometric titration as well as potentiometric determination of concentration of Pb2+ ions in real-life samples.

The effect of methylene blue on water hardness and antibacterial activity and the environment

This research was carried out to compare complexometric titration methods for the determination of water hardness in the presence of two colored indicators. The complexometric titration with EDTA method has evolved from the typical method of determining water hardness rates used in various references in several countries. Our objective is to make a comparison between Methylene Blue (MB) and Eriochrome black T (EBT) used as color indicators to determine the hardness in drinking water as a function of the flow. Several chemical – physic were used to determine the maximum absorbance of the two dyes UV-visible, identification of functional groups by infrared spectroscopy (FT-IR), supported by the effect of concentration conductivity, pH and turbidity and density. Test results to determine water hydrometric title (TH) in the presence of two colored indicators indicated that the equivalent volume values (Veq) are doubled for the BM indicator compared to the EBT indicator however with impressive TH values in two different intervals between 10 < TH< 20 and 30 < TH < 50. This shows that the colored indicator Methylene Blue has important differences. An antibacterial activity is observed on the dye by the disk method on four bacteria in the agar culture medium, from which it can be said that there is sensitivity to antimicrobial agents against methylene blue.

Americium co-precipitation with calcium oxalate

Relevance. The fact that the literature does not contain any data not only on crystallization coefficients, but also on the nature of the co-precipitation of americium (III) with calcium oxalate. The co-precipitation reaction of americium with calcium oxalate is used to concentrate trace amounts of americium due to calcium oxalate low solubility and adsorption capacity. In this relation, the study of co-precipitation of trace amounts of americium with calcium oxalate, as well as the study of the isolation of trace amounts of americium using a calcium carrier and its subsequent separation from the carrier, is of unconditional interest. Aim. Investigation of americium co-precipitation with the solid sorbent – calcium oxalate, description of the equilibrium of the sorption isotherm using Langmuir and Freundlich models. Methods. When studying the establishment of co-precipitation of americium with a carrier – calcium oxalate, the qualification of the chemical reagents used met the requirements of the grade not lower than r.g. The isotope americium-241 was used in the work, the composition of the solid phase of the carrier – calcium oxalate – corresponded to the formula CaC2O4·H2O. The concentration of americium (III) cations in the initial solution and in the filtrate was determined by gamma-spectrometric method using the SCS-07P spectrometric complex, the amount of calcium – by complexometric titration with murexide as an indicator, and the concentration of oxalate ion – by permanganatometric method. Results. It was found that the co-precipitation of americium (III) nitrate solutions with calcium oxalate is largely due to adsorption of the micro-component – americium (III) – on the surface of the existing or newly formed precipitate of the macro-component calcium oxalate. It is determined that the Langmuir equation model adequately describes sorption, since the processing of experimental data by the least squares method showed that in coordinates C/A=f(C) the sorption isotherm is described by the equation of a straight line with a high correlation coefficient of more than 0.95.

In English

Purifying aqueous solutions from radioactive contamination is an extremely relevant scientific topic today. Many organic and inorganic adsorbents can be recommended for the adsorption of heavy metal ions and radionuclides from aqueous solutions, or as carriers for storage and disposal of radioactive waste. Since radionuclides are sources of ionizing radiation, the radiation resistance of the adsorbent is an important characteristic. These studies aim to investigate the titanium silicate behavior and its adsorption properties' changes or their invariability in the field of intense β-radiation. Experimental techniques describe the synthesis of titanium silicate adsorbent by sol-gel method and the study of its adsorption capacity toward Ba2+ cations. The adsorption of Ba2+ cations was investigated under batch conditions with neutral pH of the solution. Initial and residual concentrations of Ba2+ cations were controlled by direct complexometric titration with Na-EDTA with Eriochrom Black T as an indicator. The study of the radiation resistance of the adsorbent to high-energy β-radiation was performed using a 90Sr-90Y β- - source “Sirius” installed in the Microtron Laboratory of the Uzhhorod National University. The distance from the source to the adsorbent samples was 20 cm. The flux of electrons at this distance was 108 el/cm2‧per second. The maximum energy of beta particles was 0.456 MeV for 90Sr and 2.28 MeV for 90Y. The maximum duration of exposure was 21 days, which corresponds to 1310 Gy. Raman spectroscopy of irradiated and nonirradiated samples of TiSi was performed using a Raman spectrometer XploRA PLUS installed in the Center for Collective Use of Scientific Equipment “Laboratory of Experimental and Applied Physics” of Uzhhorod National University. Results consist of kinetic of Ba2+ adsorption by titanium silicate and irradiated titanium silicate; isotherm of Ba2+ adsorption and Raman spectrum of nonirradiated, irradiated titanium silicate (TiSi) and TiSi after Ba2+ adsorption. Results showed that the value of the maximal adsorption was 140.5±9.2 mg/g (6.55 %) under a confidence level of 95 %. The adsorption values of barium ions by irradiated and non-irradiated titanium silicate coincide. This indicates that the adsorption properties of this adsorbent do not change under the influence of such a radiation dose. The Raman spectra of irradiated and non-irradiated titanium silicate coincide, while they do not identify free radicals, or ionic formations, which would indicate a change in the properties of the adsorbent under the influence of beta radiation. It can be argued that this adsorbent is radiation-resistant to beta-radioactivity, with a radiation dose of 1310 Gy. The main conclusion of the present work is that the studied sample of titanium silicate is radiation-resistant. It can withstand a radiation dose of 1310 Gy without changing its adsorption properties. Titanium silicate can be used for the adsorption of strontium radionuclides, it can be a carrier for the disposal of radioactive waste.

Deciphering groundwater pollution in the Lower Anayari Catchment: insights from using δ2H, δ18O, PMF, and APCS-MLR receptor model.

This research provides a comprehensive analysis of groundwater pollution in the Lower Anayari Catchment (LAC) through δ2H and δ18O isotopic analysis, along with positive matrix factorization (PMF) and PCS-MLR receptor models. Forty groundwater samples were collected from hand-dug wells and equipped boreholes across the LAC. Flame photometry for Na+ and K+, complexometric titration for Ca2+, ion chromatography for Cl-, F-, NO3-, SO42-, and PO43-, and atomic absorption spectrometry for Mg2+, Fe, Pb, Cd, As, and Ni were analytical techniques/instruments employed. In regard to cations, Na+ has the highest average concentration of 63.0 mg/L, while Mg2+ has the lowest at 2.58 mg/L. Concerning the anions and nutrients, Cl- has the highest mean concentration of 18.7 mg/L, and Fl- has the lowest at 0.50 mg/L. Metalloids were detected in trace amount with Fe displaying the highest mean concentration of 0.077 mg/L whereas Cd and As recorded lowest (0.001 mg/L). The average values for groundwater δ18O and δ2H were - 3.64‰ and - 20.7‰, respectively; the average values for rainwater isotopic composition were - 3.41‰ for δ18O and - 17.4‰ for δ2H. It is believed that natural geological features, particularly biotite granitoid and volcanic flow/subvolcanic rocks from the Birimian Supergroup, significantly influence groundwater mineralisation. Additionally, the impact of anthropogenic activities on water quality, with urban development and agricultural practices, may be attributed to increasing levels of certain contaminants such as Fe, Ni, NO3-, and PO43-. This research contributes to the broader field of hydrological study and provides practical implications for managing and conserving water resources in similar contexts. The innovative combination of isotopic and statistical analyses sets a new standard for future studies in groundwater quality assessment, emphasising the need for comprehensive approaches that consider both geological characteristics and human impacts for sustainable water resource management.

Clay peptization and clay swelling inhibition in the presence of carbonic acid, bicarbonate and carbonate ions and calcium ions

Relevance. The need to ensure the integrity of the wellbore, composed of clay rocks, and the stability of drilling fluid when drilling in conditions of carbon dioxide and bicarbonate aggression. Aim. To determine experimentally the effect of carbonic acid, bicarbonate and carbonate ions on clay depending on the presence of calcium ions in the dispersion medium. Objects. Water contaminated with carbonic acid, bicarbonate and carbonate ions with different equivalent concentrations of calcium ions. Methods. Inhibitory and peptizing properties of the objects of study in relation to the clay rock were studied by the method of clay swelling when it was in the water under study (on the Zhigacha-Yarov device); methods of chemical analysis (complexometric and acid-base titration) and potentiometry were used to control water composition and properties. Results. The peptizing and inhibiting properties of drilling fluid depend significantly on the form of carbonic acid present in the dispersion medium and the equivalent content of calcium ions (Ca2+). It was found that carbonic acid (H2CO3) contributes to clay inhibition (coagulation), bicarbonate ions (HCO3–) and carbonate ions (CO32–) – clay peptization. Calcium ions (Ca2+) do not have an inhibitory effect in the presence of carbonic acid (H2CO3) – hydrogen ions (H+) displace exchangeable cations from the interlayer space of clays and, due to their small diameter, independently inhibit clay swelling. In the presence of bicarbonate ions (HCO3–), calcium ions (Ca2+) also do not have an inhibitory effect – bicarbonate ions (HCO3–), being in a dispersion medium, draw calcium ions (Ca2+) from the clay surface, increasing the thickness of the electrical double layer. In the presence of carbonate ions (CO32–) the calcium ions (Ca2+) precipitate and effectively prevent clay peptization only in the presence of hydroxide ions (OH–). The authors proved experimentally that calcium ions (Ca2+) in the presence of hydroxide ions (OH–) have a better inhibitory ability than hydrogen ions (H+) of dissociated carbonic acid (H2CO3). A mechanism was proposed for inhibiting the swelling of clays by calcium ions (Ca2+) in the presence of hydroxide ions (OH-), based on the adsorption of the hydrated calcium ion (Ca2+) on a silica tetrahedral sheet due to the preliminary protonation of its oxygen atoms by water molecules. The conditions required for clay effective peptization are formulated: [CO32–]≥0; [OH–]>0, [Ca2+]=0, pH>11.5; for clay swelling inhibition: [CO32–]=0; [OH–]>0, [Ca2+]>0 and pH>11.5.

Addressing the Environmental Concerns: Statistical Approach for Mg2+ and Mn2+ Mitigation in Water System Sustainability in Indonesia

This research aimed to determine the most effective adsorbent for reducing Mg2+ and Mn2+ levels in residential water near the oil and gas industry in the Tambun area, Bekasi, Indonesia. Bentonite was tested with varying temperature conditions. The study further compared activated charcoal and bentonite as potential adsorbents, examining their efficacy under different contact times (10, 20, and 30 minutes). Thus, sampling followed the SNI 6989.57:2008 method for surface water sampling, with bentonite conditioning and activation as initial steps. Next, the adsorption experiments utilized a separating funnel, varying the contact time between adsorbent and sample. Hence, the filtrates were analyzed quantitatively for Mn2+ using atomic absorption spectroscopy and for Mg2+ through complexometric titration.

A novel pH-sensitive method for the quantification of Ca2+ ions by complexometric titration with Na3HEDTA.

A simple and accurate complexometric titration has been developed by the reaction between Ca2+ ions (pH 7) and Na3HEDTA (pH 11) solutions. Formation of a Ca-EDTA complex and release of H+ ions in the system were traced by a decrease in the pH. At the equivalence point of the titration, a sharp increase in the pH was observed. Looking at the working pH range (pH 6.2-7.5) of this method, another complexometric titration method has been developed by using bromothymol blue as a pH sensitive indicator. This is the first report of a complexometric titration by using an acid base indicator.

Improvement of heat transfer and fouling retardation performance of heat exchanger using green functionalized graphene nanoplatelets additives

BackgroundCalcium carbonate (CaCO3) is one of the main fouling elements of the crystallization fouling that causes critical problems in the operation of industrial heat exchangers. This study presents the retardation of CaCO3 Fouling, and heat transfer enhancement of a tube heat exchanger immersed in a CaCO3 rich solution containing clove treated graphene nano platelets (C-GNP) additives as suspension. MethodsThermo-physical properties of water-based C-GNP additives nanofluid were tested before running the experiment. Experimental investigation was conducted to assess the C-GNP additives performance in the enhancement of heat transfer and reduction of fouling deposition. For the retardation of fouling experiments, the hard water or super saturated fouling solution of 300 ± 20 mgL−1 was prepared. To maintain the hard water concentration until the end of the experiments, a complexometric titration was adopted to monitor the CaCO3 concentration at every 6 h. interval. The FESEM was utilized for the investigation of the morphology of CaCO3 deposition on the heat exchanger surface. Significant findingsThe results of this study demonstrate that the addition of C-GNP enhanced the heat transfer and reduced the foulant deposition without any effect of corrosion. The results also revealed the inverse relationship between the additive concentration and the fouling resistance. The outcomes of this study also support the achievement of United Nation sustainable development goal (SDG) target 7.3.

Use of Ipomoea involucrata B. flower as metallochromic indicator for complexometric titrations

The present work highlights the use of Ipomoea involucrate B. flower extract as a complexometric indicator in complex formation between the EDTA and the following metal solutions (Cu2,+ Ba2,+ Hg2+, Fe3+, and Bi3+). Ipomoea involucrate is a species of the Ipomoea genus, belonging to the family Convolvulaceae. This natural indicator was extracted in 2M HCl at 100 0C for 30-40 minutes, cooled and the extract filtered and extracted with ethyl acetate and the pigment extracted with amyl alcohol which was separated and concentrated over a water bath. The flower extract was screened for its use as an metallochromic indicator at different pHs in metal solutions of Cu2,+ Ba2,+ Hg2+, Fe3+, and Bi3+.This natural indicator from the results obtained gave sharp intense color change at the equivalence point of complex formation between the metals and the EDTA at both acidic and alkaline pHs in the metal solution of Cu2+ and Fe3+ and that with different amount of EDTA used in the titration, which increased as the pH value increased, while the ipomoea indicator gave sharp intense color change at the equivalence point of complex formation between the metals and the EDTA at alkaline pHs in the metal solution of Ba2+, Hg2+ and Bi3+ at pH > 10. Natural flower indicators could take the place of the synthetic metallochromic indicators currently used in conventional laboratories because these flower extracts have excellent performance with sharp and intense color change in end points during the complexometric titrations and simple, cost-effective and environmentally friendly extraction methods.

Sustainable nanohybrid of CaO with rGO for efficient photocatalytic removal of wastewater pollutants

The prominent water pollutants, Safranin (SF) and Eriochrome Black T (EBT) dye extensively used in plastic, leather, complexometric titrations, and textile industries, cause severe toxic impacts on the environment and human health. So, for their elimination, a cost-effective and sustainable hybrid of calcium oxide with reduced graphene oxide (rGO@CaO) was employed, synthesized using waste egg shells (precursor of calcium oxide), and thermal reduction of graphene oxide produced via modified Hummer's method. The sharp PXRD peaks confirmed the crystalline nature of the nanocomposite's pure and deformed spherical nanoparticles (20–40 nm). The removal of dyes was subsequently studied using the rGO@CaO nanocomposite (5–25 mg) at specific reaction conditions investigated (pollutant: 10–50 mgL-1, pH: 3–11, dark–sunlight). Under UV irradiation, the rGO@CaO nanocomposite demonstrated maximal degradation (SF: 97 % and EBT: 93 %) with 10 mg of catalytic dose at the initial dye concentration (10 mgL-1). The efficient photocatalytic efficacy of the rGO@CaO nanocomposite was supported by its small size, large surface area (48.06 m2g−1), higher negative zeta potential (-31.5 mV), and smaller bandgap (2.0 eV). Scavenger analysis revealed that holes, O2, and OH radicals play a crucial role in breaking the complex structure of SF and EBT. After degradation, safer metabolites developed, which was verified by LC-MS analysis. In conclusion, hybrid rGO@CaO nanocomposite is an efficient catalyst for industrial applications with broad potential due to its stability, higher charge separation, cost-effectiveness, and increased reusability (n = 8).

Development of a highly efficient gadolinium(III) potentiometric sensor using two aza-crown ether-based multiple diglycolamides (DGAs)

The present investigation deals with the development of two polyvinyl chloride- (PVC) based potentiometric sensors for gadolinium(III) ion with two multiple diglycolamide (DGA) ligands with the DGA moieties tethered onto aza-crown ethers as ionophores, 2-nitrophenyl octyl ether (NPOE) as the plasticizer and sodium tetraphenylborate (NaTPB) as ionic additive. The ionophores are a tripodal DGA ligand containing a triaza-9-crown-3 core (LI) and a tetrapodal DGA ligand with a tetraaza-12-crown-4 as the scaffold (LII). The polymer inclusion membranes (PIMs) were tested for gadolinium ion detection in a mildly acidic solution (pH 3.0 ± 0.1). The PIM containing an optimized composition of 7.8% LI, 29.6% PVC, 60.5% NPOE, 2.1% NaTPB exhibited a linear response behaviour from 7.2 × 10−7 to 4.9 × 10−3 M Gd3+ with a slope of 19.8 ± 0.4 mV/decade and a limit of detection (LOD) of 6.0 × 10−7 M. The sensor showed fast response time (<20 s) and a lifetime of at least two months. It exhibited good tolerance to monovalent/divalent interfering ions and moderate to poor tolerance to trivalent ions. The effect of temperature on the selectivity coefficient of Gd3+ over La3+ was determined which indicated a decreasing trend with temperature. The concentration of Gd3+ in the inner filling solution (IFS) had a significant effect on the sensor sensitivity and on the detection limit. The other sensor containing LII performs poorly as a potentiometric sensor. The physical characterization of the membranes was done using thermogravimetry (TGA), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and photoluminesce (PL) spectroscopy. A PL study was performed using Eu3+ as a surrogate probe for Gd3+ as the latter ion does not show luminescence properties. The PL spectra suggest the presence of a single analyte ion species in the membrane. The sensor containing LI can be used as an indicator electrode for the potentiometric titration of Gd3+ which indicated a recovery of 94.6 ± 4.3% of Gd3+ for triplicate measurements and the results match well with the complexometric titration result using xylenol orange as a colorimetric indicator for the endpoint detection.

Adsorption of yttrium by the sodium-modified titanium dioxide: Kinetic, equilibrium studies and investigation of Na-TiO2 radiation resistance

The adsorption of yttrium cations from an aqueous solution of YCl3 by sodium-modified titanium dioxide (Na-TiO2) was investigated. The Na-TiO2 was obtained by impregnating Na+ cations into the surface layer of TiO2 nanoparticles. The synthesis of nanoparticle TiO2 was performed by a liquid-phase sol–gel method, using the aqua complex of [Ti(OH2)6]3+‧3Cl− as a precursor. Nanoheterostructured Na-TiO2 is an anatase modification of TiO2. The amount of incorporated sodium cations on the TiO2 surface is about 6%. The surface area of Na-TiO2 is 239 m2‧g−1; the volume of mesopores is 0.098 cm3‧g−1; that of micropores is 0.054 cm3‧g−1. Yttrium ion adsorption was investigated under batch conditions. Complexometric titration and mas-spectrometric analysis determined the initial and equilibrium concentration of yttrium. The radiation resistance of Na-TiO2 to the influence of beta irradiation was investigated as well. For this purpose, the radiation of β−-particles of the 90Sr-90Y source “Sirius” was used. The flux of β− – particles was 2.1 ‧ 108 electrons/sm2‧s; the maximal energy of incident electrons was 2.28 MeV. It was shown that the investigated adsorbent has a high adsorption capacity toward yttrium cations. The maximum adsorption is about 259 mg/g. The adsorption kinetic is fit well with the kinetic model based on the pseudo-second-order equation. The equilibrium adsorption of yttrium cations is described by Freundlich's theory with high reliability. The adsorbent is resistant to the influence of β− – irradiation. This is manifested in the invariance of its adsorption capacity toward yttrium cations after irradiation. Na-TiO2 is a promising material for the adsorption of yttrium and Rare Earth elements and can be used as the basis for the 90Y isotopic generator.

Separation, characterization, and antiviral activity of colloidal phase state of Maxing Shigan Decoction

This study focused on the separation, characterization, content determination, and antiviral efficacy research on colloidal particles with different sizes in Maxing Shigan Decoction(MXSG). The mixed colloidal phase of MXSG was initially separated into small colloidal particle segment(S), medium colloidal particle segment(M), and big colloidal particle segment(B) using ultrafiltration. Further fine separation was performed using size-exclusion chromatography. Dynamic light scattering(DLS) and transmission electron microscopy(TEM) were employed to characterize the size and morphology of the separated colloidal particles. UPLC-MS/MS was used to determine the content of ephedrine, amygdalin, glycyrrhizic acid, and the EDTA complexometric titration was used to measure the calcium(Ca~(2+)) content in different colloidal phases. Finally, a respiratory syncytial virus(RSV) infection mouse model was established using intranasal administration. The experimental groups included a blank group, a model group, a ribavirin group, an MXSG group, an S group, an M group, and a B group. Oral administration was given for treatment, and pathological changes in mouse lung tissue and organ indices were evaluated. The results of the study showed that the distribution of ephedrine, amygdalin, glycyrrhizic acid, and Ca~(2+) content was not uniform among different colloidal segments. Among them, the B segment had the highest proportions of the three components, except for Ca~(2+), accounting for 46.35%, 53.72%, and 92.36%, respectively. Size-exclusion chromatography separated colloidal particles with uniform morphology in the size range of 100-500 nm. Compared to the S and M segments, the B segment showed an increased lung index inhibition rate(38.31%), spleen index, and thymus index in RSV-infected mice, and it improved the infiltration of inflammatory cells and lung injury in the lung tissue of mice. The complex components in MXSG form colloidal particles of various sizes and morphologies through heating, and small-molecule active components such as ephedrine, amygdalin, glycyrrhizic acid, and Ca~(2+) participate in the assembly to varying degrees. The main material basis for the antiviral effect of MXSG is the colloidal particles with certain particle sizes formed by the assembly of active components during the heating process.

Ionophore-Based Nanosphere Emulsion Incorporating Ion-Exchanger for Picogram Potentiometric Determination of HCV Drug (Daclatasvir) in Pharmaceutical Formulations and Body Fluids

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.

Study on the effect and mechanism of NaOH on the modification of fluorapatite: A new method of preparing fluor-hydroxyapatite

Fluorapatite (FA) and fluor-hydroxyapatite (FHA) have good biocompatibility to substitute for human hard tissue, whereas FA has more cytotoxic and genotoxic effects than FHA. In this study, a new method named nitric acid dissolution-recrystallization was proposed to achieve the modification of FA, and NaOH was used to introduce OH- into FA to prepare FHA in the recrystallization process. The effect and mechanism of NaOH/pH value on the modification of FA were investigated using XRD analysis, SEM detection, EDTA complexometric titration, and FT-IR measurements. XRD and SEM analyses indicated that the synthesized FHA at the pH value of 8.00 had the highest crystallinity and the largest crystal size, reaching 38.10 nm, and the crystal was in the form of short rods with a length of about 1 μm. It was found that the content of the F element in the synthesized FHA decreased as the pH value of the reaction system increased. When the pH value reached 8.00, the content of F was 0.60%, and the values of x and (2-x) in FHA [Ca10(PO4)6Fx(OH)2-x] were 0.16 and 1.84, respectively. FT-IR analysis further confirmed that the content of OH- in FHA obtained at the pH value of 8.00 was noticeably higher than that obtained at the pH value of 4.46. This work could provide a new prospect for utilizing FA to prepare FHA and be of great significance.

Reevaluation for UV photolysis of Fe(III) inducing tetracycline abatement: Overlooked significance of complexation-assistance in environmental fates of antibiotics

Interaction of antibiotics with metal ions in aquatic environments, commonly occurring to form complexes, may affect the migration, transformation and reactivity of residual antibiotics. This study demonstrates the photolysis of Fe(III) by UV irradiation at pH 3.5, as an advanced oxidation process, to produce •OH for the abatement of a common broad-spectrum antibiotic compound, tetracycline (TET). The dimethylamino (-N(CH3)2) and hydroxyl (-OH) groups of TET were determined as the binding sites for the complexation with Fe(III) via a series of novel characterization approaches. The complexation stoichiometry of Fe(III)-TET complexation, including the complexation ratio, constants and percentages, was determined via a complexometric titration based on the UV differential spectroscopy. The complexation constant was determined to be 21,240 ± 1745 L·mol−1 under the designed conditions. Complexation of TET with Fe(III) enhanced its degradation in the UV/Fe(III) process, through the promotion of the •OH generation by inhibiting hydrolysis-precipitation process of Fe(III) and enhancing Fe(III)/Fe(II) cycle and the acceleration of mass transfer between •OH and TET. This finding provides new insights into the role of complexation in the fate of residual antibiotics in the UV/Fe(III) process. The reduced overall ecotoxicity during the TET abatement, evaluated by the toxicity variation through ECOSAR program, provides the UV/Fe(III) process with a theoretical feasibility for water decontamination in actual applications.

Magnetic in situ determination of surface coordination motifs by utilizing the degree of particle agglomeration

Most analytical techniques used to study the surface chemical properties of superparamagnetic iron oxide nanoparticles (SPIONs) are barely suitable for in situ investigations in liquids, where SPIONs are mostly applied for hyperthermia therapy, diagnostic biosensing, magnetic particle imaging or water purification. Magnetic particle spectroscopy (MPS) can resolve changes in magnetic interactions of SPIONs within seconds at ambient conditions. Herein, we show that by adding mono- and divalent cations to citric acid capped SPIONs, the degree of agglomeration can be utilized to study the selectivity of cations towards surface coordination motifs via MPS. A favored chelate agent, like ethylenediaminetetraacetic acid (EDTA) for divalent cations, removes cations from coordination sites on the SPION surface and causes redispersion of agglomerates. The magnetic determination thereof represents what we call a “magnetically indicated complexometric titration”. The relevance of agglomerate sizes for the MPS signal response is studied on a model system of SPIONs and the surfactant cetrimonium bromide (CTAB). Analytical ultracentrifugation (AUC) and cryogenic transmission electron microscopy (cryo-TEM) reveal that large micron-sized agglomerates are required to significantly change the MPS signal response. With this work, a fast and easy-to-use characterization method to determine surface coordination motifs of magnetic nanoparticles in optically dense media is demonstrated.

Synthesis, Spectral Characterization and Potential Fluorescent Properties of Three Lanthanide(III) Ions Complexes with Nalidixic Acid.

Three new solid lanthanide complexes with nalidixic acid (HNal) with the stoichiometry [Ln(Nal)3]·5·.5H2O (Ln=Tb, Dy and Ho) were synthesized applying the green synthesis method from the aqueous solutions without the organic solvent addition and fully characterized by the elemental analysis, XRF, complexometric titration, gravimetric analysis, molar conductivity and solubility measurements, powder X-Ray diffraction, UV-Vis and infrared (FT-IR) spectroscopies. Moreover, the luminescent properties of the Tb(III), Dy(III), and Ho(III) complexes in the solid state and in the solutions were investigated. On the basis of the detailed spectral analysis, it was concluded that the nalidixate ligands bind to the lanthanide ions by the bidentate carboxylate and carbonyl groups while water molecules belong to the outer coordination sphere. At the excitation of UV light, the complexes exhibited characteristic emission of central lanthanide ions, the intensity of which depends significantly on the excitation wavelength and/or the solvent. Thus, the application of nalidixic acid (apart from biological activity) for the synthesis of luminescent lanthanide complexes was confirmed which can find potential applications in the field of photonic devices and/or bioimaging agents.