Complexation Constants Research Articles

Metal Complexes in Biology and Medicine: The System Cadmium (II)/ Iron (II)/ Zinc (II)- α- Aminobutyric Acid

Metal ions play an important role in biological systems. The importance of metal ions to essential functions of living systems and for wellbeing of living organisms is well known. Complexation reactions of α– aminobutyric acid with cadmium (II), iron (II) and zinc (II) have been studied in solution phase using paper ionophoretic technique. The present method is based upon the migration of a spot of metal ion on a paper strip at different pH values of background electrolyte containing 0.01M α -aminobutyric acid. A graph of pH against mobility was used to obtained information in the binary complexes and to calculate its stability constants. The logarithm stability constants of ML and ML2 complexes of α -aminobutyric acid were found to be (4.01 ± 0.02; 2.72 ± 0.01), (3.73 ± 0.03; 2.65 ± 0.09), (4.45 ± 0.02; 2.80 ± 0.03) for cadmium (II), iron (II) and zinc (II) complexes, respectively at ionic strength 0.1 molL-1 and a temperature of 35º C. Metal based drugs bioactivity can be increase by metal chelation, which in turn increase their absorbance and stability. Metal complexes can offer their action such as anti-inflammatory, anti-diabetic, antimicrobial, anticancer and ant thyroid compounds.

Rotation of a Tricomi–Gaussian beam and its focusing characteristics through a thin lens system

The rotation behaviors of an asymmetric Tricomi–Gaussian beam (aTGB) propagating in free space and through a thin lens system are mainly investigated. The focusing characteristics of TGB with symmetric and asymmetric modes propagating through a thin lens system are also presented. Influences of complex constants α and β, the topological charge n, and the lens focal length f on the field distributions of TGB are studied thoroughly. The results indicate that when a symmetric TGB propagates through a thin lens system, a perfect vortex beam could be generated at the lens focal plane. TGB undergoes two focusing processes through the thin lens system, and the peak intensities at two focal planes, the rotation, and the focal characteristics of TGB can be manipulated by α,β,n, and f. Moreover, f has more significant effects on the focal depths of two foci and the self-focusing focal length than α,β, and n.

The fully reduced terminal oxidase bd-I isolated from Escherichia coli binds cyanide

Cytochrome bd-I from Escherichia coli belongs to the superfamily of prokaryotic bd-type oxygen reductases. It contains three hemes, b558, b595 and d, and couples oxidation of quinol by dioxygen with the generation of a proton-motive force. The enzyme exhibits resistance to various stressors and is considered as a target protein for next-generation antimicrobials. By using electronic absorption and MCD spectroscopy, this work shows that cyanide binds to heme d2+ in the isolated fully reduced cytochrome bd-I. Cyanide-induced difference absorption spectra display changes near the heme d2+ α-band, a minimum at 633 nm and a maximum around 600 nm, and a W-shaped response in the Soret region. Apparent dissociation constant (Kd) of the cyanide complex of heme d2+ is ∼0.052 M. Kinetics of cyanide binding is monophasic, indicating the presence of a single ligand binding site in the enzyme. Consistently, MCD data show that cyanide binds to heme d2+ but not to b5582+ or b5952+. This agrees with the published structural data that the enzyme's active site is not a di-heme site. The observed rate of binding (kobs) increases as the concentration of cyanide is increased, giving a second-order rate constant (kon) of ∼0.1 M−1 s−1.

Sorption of U(VI) on MX-80 bentonite, illite, shale and limestone in Na–Ca–Cl saline solutions

Uranium (U) has been identified as an element of interest for the safety assessment of a deep geological repository for used nuclear fuel. In this study, the sorption of U(VI) was studied in Na–Ca–Cl solutions at ionic strengths = 0.1–6 mol/kgw (m) in a CO2 free environment at pHm (molal H+ concentration where pHm = −log mH+) = 4–9 for MX-80 bentonite, illite and Queenston shale and at pHm = 5–9 for limestone. U(VI) sorption on MX-80 bentonite increased with pHm from pHm = 4 to 6, then decreased with pHm until pHm = 7, and then increased again with pHm to pHm = 9. U(VI) sorption on illite increased with pHm reaching a maximum at pHm = 7, and then decreased with further increases in pHm. The sorption behavior of U(VI) on shale was similar to that of illite, but the extent of decrease in the sorption coefficient (Rd) value with pHm was slightly more pronounced for the shale than observed for sorption on illite at pHm > 7. U(VI) sorption on limestone increased with pHm up to pHm = 8 and then seemed to be constant at pHm = 8–9. U(VI) sorption on all four solids was independent of ionic strength (0.1–6.0 m). The 2 site protolysis non-electrostatic surface complexation and cation exchange model successfully simulated the sorption of U(VI) onto MX-80 and illite, and the optimized values of surface complexation constants were estimated.

Colorimetric Fluorescence of a 2,4,5‐Triaryl Imidazole‐Based Sensor for the Selective Detection of Iron

AbstractTwo imidazole‐based color‐changing fluorescent probes 4‐(4,5‐bis(4‐chlorophenyl)‐1H‐imidazol‐2‐yl)‐N, N‐diphenylaniline (CIN) and 4‐(4,5‐di(furan‐2‐yl)‐1H‐imidazol‐2‐yl)‐N, N‐diphenylaniline (FIN) were synthesized and characterized. The new probes CIN and FIN exhibit excellent selectivity and sensitivity towards Fe3+ with relatively low detection limits (0.26 μM and 0.10 μM) and strong anti‐interference properties. Both the probes CIN and FIN complex 1 : 1 with Fe3+ ion, and the complexation constants were 1.165×105 M−1 (CIN) and 1.899×105 M−1 (FIN), respectively. Moreover, CIN and FIN could be recycled by EDTA and could effectively monitor Fe3+ ions at pH 4–10, which ensures the sensor‘s potential for detecting Fe3+ in actual aqueous solutions. The probes were further applied to the detection of Fe3+ in the actual reaction of Fe2+ oxidation, and the filter paper and the probe solution are combined to make an indicator to detect Fe3+ more conveniently and quickly.

NCS-catalyzed synthesis of 2,4,5-triaryl-1H-imidazole and its selective detection of iron ions

In this study, an efficient synthesis of 2,4,5-trisubstituted imidazoles was developed via cyclocondensation starting from o-dione, substituted aromatic aldehyde and ammonium acetate using catalyst NCS, and was characterized by HR-MS, FT-IR, 1H and 13C NMR spectroscopy. A novel fluorescence sensor 4-(1H-phenanthro[9,10-d]imidazol-2-yl)-N, N-diphenylaniline (3bd) was discovered for the detection of Fe3+ ions. The probe 3bd exhibited strong blue radiation in solution. In the presence of Fe3+ ions, a significant fluorescence change of blue light to green light was observed in the EtOH/H2O (4/1, v/v) solution of 3bd (Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Mn2+, Pb2+, Sr2+, Zn2+). The limits of detection of probe 3bd for Fe3+ ions was calculated to be as low as 0.70 μM, and it had excellent anti-interference ability. The probe 3bd complexed with Fe3+ ions at 1:1, and the complexation constant was 3.93 × 104 M−1. The probe 3bd realized the detection of Fe2+ oxidation to Fe3+, and the pH showed fine stability in the environment between 4.0–7.0, which ensured its potential application prospects. It also showed good reversibility upon addition of EDTA. Furthermore, the viability of 3bd to Fe3+ had practical application in live cell imaging.

A novel fluorescent probe based on naphthimide for detecting Zn2+ and its application in plant imaging and cell imaging

The fluorescent probe NXZ was synthesized by introducing –OH at position 1, 8-naphthalimide 4-position and benzimidazole unit at 3-position. The Stokes shift (λem − λex) of NXZ can up to 148 nm, when Zn2+ was added to the probe solution, NXZ can quickly form the complex NXZ-Zn2+ with Zn2+ in a ratio of 1: 1 within 55 s, and then quench the fluorescence intensity by 4.4 times. The complexation constant of NXZ and Zn2+ was 1.2 × 104 M−1, and the detection limit for Zn2+ was 40.3 nM, which is much lower than the maximum Zn2+ content (76 µM) stipulated in the World Health Organization (WHO). Exploring the practical application of the probe NXZ found that NXZ can be used for the quantitative detection of Zn2+ in actual water samples and qualitatively detect Zn2+ in bean sprouts samples and Hela cells. In addition, NXZ can also be made into Zn2+ test paper.

Mn loading on montmorillonite surfaces for Cd stabilization: Insights from density functional theory calculations and surface complexation modeling

The latest works have been devoted to the stabilization mensuration for heavy metals and indicate that clay minerals can promote Cd(II) precipitation by favoring the retention of Mn(II). The assessment however has been tempered due to lacking the information about the molecular-level surface complexation structure and Cd nucleation process on clay surfaces. In this study, microscopic mechanisms for adsorption and stabilization of Cd at montmorillonite interfaces with or without Mn loading were leveraged by combining surface complexation model (SCM) evaluations and density functional theory (DFT) calculations. Mn(II) substitution resulted in increases in surface acidity equilibrium constant (pKa) by about 1 unit and complexation constant (lgK(SOCd+)) of Cd(II) by about 0.15 units at clay surface, and Mn(II) adion can provide extra active sites (i.e., OH− groups) for complexing Cd(II) via hydrolysis. DFT calculations revealed Mn(II) and Cd(II) adions bind on base surfaces by isomorphic substitutions through weak long-range interactions, whereas on edge surfaces by surface complexation with strong but short-range connections. Adsorption energy calculations and electrostatic distribution showed heterogenous nucleation with subsequent cations on clay surfaces was thermodynamically favored, the stabilization process underwent the steps of the adsorption-hydrolysis-precipitation. The derived results provide a quantitative basis for understanding the precipitation and heterogenous nucleation of cations on clay surfaces in surficial environments.

Chelate extraction of metal ions in aqueous/chloroform system based on molecular crowding environment

Abstract In this study, we propose a novel concept for the solvent extraction of metal ions (Co, Zn, and Pb) by mimicking a molecular crowding environment using dextran (Dex). The metal ions were extracted from the aqueous phase into the organic phase (chloroform) in the presence of 8-hydroxyquinoline (HQ). The extraction constant of the metal complex (Kex) increased with increasing Dex concentration (CDex) for all metal ions. When examining the dependence of CDex on the four equilibrium constants (distribution coefficient of HQ, acid dissociation of HQ, complexation constant of metal complex (β), and distribution coefficient of the metal complex) that contribute to Kex, only β increased with CDex. This suggests that an increase in, β, a parameter reflecting the molecular crowding effect, results in an increase in Kex. The increase in β was analyzed based on volume exclusion and osmotic pressure effects. The analytical model effectively explained the enhanced the complexation due to the increase in β and volume exclusion, whereas the osmotic pressure suppressed β. Consequently, we unveiled the effect of molecular crowding on the solvent extraction of metal ions for the first time.

A joint experimental and theoretical investigation of the binding mechanism between zein and folic acid in an ethanol–water solution

ABSTRACT The aim of the present study was to determine the binding mechanisms between zein and folic acid in an ethanol – water solution. Fluorescence spectroscopy demonstrated that folic acid quenched the fluorescence intensity of zein by both dynamic and static fluorescence quenching mechanisms, with static quenching playing a prominent role. The binding constants (Ka) of the zein-folic acid complex at 292, 302, and 312 K were evaluated to be 5.97 × 105, 3.00 × 105 and 1.54 × 105 L/mol, respectively. The process of folic acid binding zein was driven by ∆H0 = –51.24 kJ/mol, ∆S0 = –64.90 J/mol•K. Van der Waals forces and hydrogen bonding primarily governed the formation of the zein-folic acid complex. Confirmation of the complex formation was obtained via UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy, which also revealed alterations in the secondary structure of zein upon binding to folic acid. Measurements of particle size and zeta potential demonstrated an enhancement in the stability of the complex system. Scanning electron microscopy and transmission electron microscopy showed the complex to possess a spherical morphology, with significant changes in the zein’s morphology following its binding to folic acid. Additionally, zein increased the photostability of folic acid against UV light radiation. Molecular docking and molecular dynamics simulations were used to investigate the binding mechanisms involved further, and the results effectively elucidated the observed experimental phenomena. This research establishes a significant theoretical foundation for the utilization of zein as a system for delivering and safeguarding folic acid.

Antiprotozoal Pt(II) Complexes as Luminophores Bearing Monodentate P/As/Sb-Based Donors: An X-ray Diffractometric, Photoluminescence, and 121Sb-Mössbauer Spectroscopic Study with TD-DFT-Guided Interpretation and Predictive Extrapolation toward Bi.

In this study, it is demonstrated that the radiative rate constant of phosphorescent metal complexes can be substantially enhanced using monodentate ancillary ligands containing heavy donor atoms. Thus, the chlorido coligand from a Pt(II) complex bearing a monoanionic tridentate C^N*N luminophore ([PtLCl]) was replaced by triphenylphosphane (PPh3) and its heavier pnictogen congeners (i.e., PnPh3 to yield [PtL(PnPh3)]). Due to the high tridentate-ligand-centered character of the excited states, the P-related radiative rate is rather low while showing a significant boost upon replacement of the P donor by heavier As- and Sb-based units. The syntheses of the three complexes containing PPh3, AsPh3, and SbPh3 were completed by unambiguous characterization of the clean products using exact mass spectrometry, X-ray diffractometry, bidimensional NMR, and 121Sb-Mössbauer spectroscopy (for [PtL(SbPh3)]) as well as steady state and time-resolved photoluminescence spectroscopies. Hence, it was shown that the hybridization defects of the Vth main-group atoms can be overcome by complexation with the Pt center. Notably, the enhancement of the radiative rate constants mediated by heavier coligands was achieved without significantly influencing the character of the excited states. A rationalization of the results was achieved by TD-DFT. Even though the Bi-based homologue was not accessible due to phenylation side reactions, the experimental data allowed a reasonable extrapolation of the structural features whereas the hybridization defects and the excited state properties related to the Bi-species and its phosphorescence rate can be predicted by theory. The three complexes showed an interesting antiprotozoal activity, which was unexpectedly notorious for the P-containing complex. This work could pave the road toward new efficient materials for optoelectronics and novel antiparasitic drugs.

A versatile method for exploring the magnetooptical properties of polar saturated and unsaturated ferromagnetic metallic thin films

Polar unsaturated ferromagnetic thin films are promising for low-power and high-speed nonvolatile resistive and optical memories. Here we measure the magnetooptical (MO) response of polar unsaturated Co90Fe10 and Co40Fe40B20 thin films in the spectral range from 400 nm to 1000 nm using vector MO generalized ellipsometry (VMOGE) in an out-of-plane applied magnetic field of ±0.4 T where magnetization of the ferromagnetic (FM) thin film is not saturated. Using magnetooptical simulation software (MagOpS®), we extract the complex MO coupling constant ( Q ) of the polar unsaturated FM thin films from difference spectra of VMOGE data recorded in a polar configuration at Hz = +0.4 T and Hz = −0.4 T. The presented approach opens a path to determine Q of both polar saturated and polar unsaturated FM thin films for simulating the MO properties of application-relevant optical memory multilayer structures.

A micro-fabricated potentiometric platform with application in a COVID-19 drug quantification and the determination of its binding affinity to a supramolecular host

Recent applications in host–guest chemistry include advanced sensing technologies, drug formulations, and drug delivery. Quantification of host–guest binding constants is significant to the continued optimization of their use. Binding constants offer valuable information about the stability and affinity of the formedcomplex that is essential to both drug formulations and delivery. In this study a novel green, portable, disposable, and cost-efficient microfabricated potentiometric sensor is introduced and successfully applied to determine the concentration of remdesivir (RMD), a COVID-19 drug, and its binding affinity to the supramolecular host sulfobutylether-β-cyclodextrin (SBEβCD) as a compatible solubilizing agent; to overcome the low water solubility of RMD which presents a significant challenge in its intravenous administration. The sensor incorporates multi-walled carbon nanotubes to improve stability and detection limits. To reduce interference effects and enhance the selectivity of the sensor for RMD, 4-tert-butyl-calix[8]arene was employed as an ionophore. A Nernstian potentiometric response for RMD over a concentration range of 1.0 × 10−3 to 1.0 × 10−6 M with a slope of 58.2 ± 0.9 mV decade−1 and a detection limit of 0.23 µM were achieved. The binding constant of the RMD-SBEβCD complex was determined to be 9.76 × 103 M−1. The proposed sensor was shown to be effective for drug quantification and measurements of binding affinities, providing valuable insights into the physicochemical properties of target drugs.

Metal Complexes in Biology and Medicine the System Cadmium (II) / Iron (II) /Zinc (II) - Proline

Metal ions are fundamental elements for the maintenance of the life span’ s of the humans, animals and plants. In coordination compound studies, a knowledge of the magnitude of the stability constants of complexes is necessary for preliminary quantitative treatment. Present work described method that involves the use of paper electrophoretic technique for the study of the equilibria in binary complex systems in solution. This method is based on the movement of a spot of metal ion in an electric field at various pHs of the background electrolyte. A plot of overall mobility of metal / complex ion versus pH was used to obtain information on the formation of binary complexes and to calculate their stability constants. The stability constant of the ML and ML2 complexes of cadmium (II) – proline,iron(II) – proline and zinc(II) – proline, have been found to be (4.61 ± 0.01; 3.04 ± 0.03), (4.21 ± 0.01; 2.89 ± 0.09) and (4.98 ± 0.02; 2.44 ± 0.05) (logarithm constant values), respectively at 35 ºC and ionic strength 0.1 mol L-1. The first and second stability constants follow the order zinc (II) >cadmium (II) > iron (II). Metal complexes can offer their action such as anti-inflammatory, antidiabetic, antimicrobial, anticancer and ant thyroid compounds. Metal based drugs bioactivity can be increase by metal chelation, which in turn increase their absorbance and stability.

Heterocyclic fluorescent Schiff base chemosensors for the detection of Fe(III) and Cu(II) ions.

Two new Schiff bases were synthesized from 1-(2,4-dihydroxyphenyl)ethanone and pyridine derivatives. Both compounds were characterized using infrared, UV-Vis., 1H NMR, 13C NMR and mass spectral studies. Density functional theory (DFT) calculations were performed for both the Schiff bases with 6-31G(d, p) as the basis set. Vibrational frequencies calculated using the theoretical method were in good agreement with the experimental values. Both the Schiff bases were highly fluorescent in nature. The cation-recognizing profile of the compounds was investigated in aqueous methanol medium. The Schiff base 4-(1-(pyridin-4-ylimino)ethyl)benzene-1,3-diol (PYEB) was found to interact with Fe(III) and Cu(II) ions, whereas the Schiff base 4,4'-((pyridine-2,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (PDEB) was found to detect Cu(II) ions. The mechanism of recognition was established as combined excited state intramolecular proton transfer (ESIPT)-chelation-enhanced fluorescence (CHEF) effect and chelation-enhanced quenching (CHEQ) process for the detection of Fe(III) and Cu(II) ions, respectively. The stability constant of the metal complexes formed during the sensing process was determined. The limit of detection for Fe(III) and Cu(II) ions with respect to Schiff base PYEB was found to be 1.64 ×10-6 and 2.16 ×10-7M, respectively. With respect to Schiff base PDEB, the limit of detection for Cu(II) ion was found to be 4.54 ×10-4M. The Cu(II) ion sensing property of the Schiff base PDEB was applied in bioimaging studies for the detection of HeLa cells.

Exploration of the Tungsten(VI) complex of hydroxamic acid's RNA binding affinity, histone deacetylase inhibitory activity, and antioxidant activity

Ribonucleic acid (RNA) is a versatile molecule, thus the opportunity to target RNA is abundant. Hence, the current exploration deals with the interaction of a metal complex of hydroxamic acid with t-RNA, along with HDAC8 inhibition activity and antioxidant activity. Binding characteristics of complex 1, Bis(N-phenylbenzohydroxamato)Tungsten(VI), which is represented as [N-PBHA-W(VI)] with Torula yeast RNA (t-RNA) were investigated by using several types of spectroscopic techniques, measurements of viscosity, and computational study through molecular docking. The intrinsic binding constant, Kb was evaluated for complex 1 which shows changes in the shift of absorption spectra, and the intensity of spectra also varies. From fluorescence measurement, the binding constant of complex 1 towards t-RNA is 6.64 ± 0.05 × 105 M−1. Stern-Volmer quenching constant was calculated. Two displacement method sare performed by using the fluorescence spectroscopic technique which discloses a groove mode of binding. The groove mode of binding is also uncovered by viscosity measurement, which was observed by increasing the complex 1 concentration. An electrochemical investigation was carried out by using cyclic voltammetry. A circular dichroism study was also employed, which further suggests a strong binding occurred between the metal complex used and t-RNA. The docked postures of t-RNA with complex 1 expose the strong interactions which suggest a minor groove mode of binding. All the experimental evidence indicates that the interaction of complex 1 with t-RNA is a minor groove mode of binding which complements the molecular docking results. In-silico studies of HDAC8 inhibition activity of complex 1 reveal that the inhibition takes place mainly by hydrophobic interaction. DPPH–radical scavenging method employed for the antioxidant activity.

Metal Complexes in Biology and Medicine: The System Cadmium ((II))/ Iron ((II))/ Zinc ((II)) - α - Aminobutenoic Acid

Metal ions play an important role in biological system. The importance of metal ions to essential functions of living systems and for wellbeing of living organisms is well known. Metal ions are fundamental elements for the maintenance of life spans of the human, animals, and plants. Recent advances in inorganic chemistry have made possible formation of number of transition metal complexes with organic ligand of interest, which can be used as therapeutic agent. In coordination compounds studies, knowledge of the stability constants of complexes is necessary for preliminary quantitative treatment. The present technique involving the use of paper electrophoresis is described for the study of equilibria in binary complex systems in solution. The method is based on the movement of a spot of a metal ion in an electric field at various pH’s of background electrolyte. A graph of pH versus mobility was used to obtained information in the binary complexes and to calculate its stability constants. Using this method , the stability constants of binary complexes metal (II) – α – aminobutenoic acid have been determined to be ( 3.78 ± 0.01, 2.48 ± 0.03 ); ( 3.27 ± 0.04, 2.33 ± 0.07 ); and (4.45 ± 0.02, 2.66 ± 0.05); (logarithm stability constant values) for cadmium (II), iron (II) and zinc (II) complexes, respectively, at ionic strength 0.01 Mol / L and a temperature of 35º C.

Prediction of Cr(VI) and As(V) adsorption on goethite using hybrid surface complexation-machine learning model

This study aimed to develop surface complexation modeling-machine learning (SCM-ML) hybrid model for chromate and arsenate adsorption on goethite. The feasibility of two SCM-ML hybrid modeling approaches was investigated. Firstly, we attempted to utilize ML algorithms and establish the parameter model, to link factors influencing the adsorption amount of oxyanions with optimized surface complexation constants. However, the results revealed the optimized chromate or arsenate surface complexation constants might fall into local extrema, making it unable to establish a reasonable mapping relationship between adsorption conditions and surface complexation constants by ML algorithms. In contrast, species-informed models were successfully obtained, by incorporating the surface species information calculated from the unoptimized SCM with the adsorption condition as input features. Compared with the optimized SCM, the species-informed model could make more accurate predictions on pH edges, isotherms, and kinetic data for various input conditions (for chromate: root mean square error (RMSE) on test set = 5.90 %; for arsenate: RMSE on test set = 4.84 %). Furthermore, the utilization of the interpretable formula based on Local Interpretable Model-Agnostic Explanations (LIME) enabled the species-informed model to provide surface species information like SCM. The species-informed SCM-ML hybrid modeling method proposed in this study has great practicality and application potential, and is expected to become a new paradigm in surface adsorption model.

Experimental investigation on nontoxic solvents for separation of vanillic acid

AbstractBACKGROUNDVanillic acid, an aromatic carboxylic acid and a derivative of vanillin, is used as an additive in consumer goods for its aroma. Previously, most vanillic acid was produced through a petrochemical route, but as a consequence of stringent environmental policies, it is now produced by the biotransformation of ferulic acid. Vanillic acid is also found in the wastewater streams of paper‐pulp industries and olive‐oil mills. So, recovering vanillic acid from fermentation broth, either during bioproduction or from a wastewater stream, while minimizing toxicity, is a difficult task. In order to reduce the toxicity substantially, bio‐based solvents such as sunflower, mustard and rice bran oils were employed as diluents along with tri‐n‐butyl phosphate (TBP) as extractant in order to recover vanillic acid by reactive extraction.RESULTSThe extraction performance was elucidated using terms such as distribution ratio, extraction efficiency, loading ratio and equilibrium complexation constant for different extractant–diluent combinations. The highest extraction efficiency and distribution ratio for the different solvents were in the following order: TBP + sunflower‐oil (72.02%–92.47%; 2.57–12.29) > TBP + rice bran‐oil (65.56%–90.55%; 1.90–9.58) > TBP + mustard‐oil(64.03%–89.87%; 1.78–8.87). The theoretical number of stages was determined as 4 to achieve a targeted extraction efficiency of 90%; these predictions were borne out experimentally.CONCLUSIONIn this study, vanillic acid was recovered from the aqueous phase using tri‐n‐butyl phosphate in sustainable, environmentally friendly, bio‐based solvents such as rice bran oil, sunflower oil and mustard oil. © 2024 Society of Chemical Industry (SCI).

Identification and application of Cr(VI) based on 2-amino-5-substituted-1,3,4-thiadiazole molecular probes

With the modernization of industry, increasingly serious water pollution has become a global environmental pollution problem. Cr (Ⅵ) is the most common water pollutant and is applied to aluminum plating, paint production leather tanning, etc. Cr (Ⅵ) is a kind of aspiration and swallowed poison, that can enter the body through the digestive tract, respiratory, and skin mucous membrane, and may occur after skin contact dermatitis, or allergic phenomena, such as redness, itching, tingling, etc. In view of the harm of Cr (Ⅵ) to the human body, it is an urgent problem to develop a probe that can simultaneously detect two kinds of Cr (Ⅵ) in the environment. Herein, a novel green synthetic 2-amino-5-substituent-1,3, 4-thiadiazole was synthesized. The synthesized 2-amino-5-methyl-1,3, 4-thiadiazole (Probe M) was used as a molecular probe to selectively recognize Cr2O72− and CrO42−, and then the anti-interference detection and quantitative test of Cr2O72− and CrO42− were carried out. The binding ratios of Probe M with Cr2O72− and CrO42− were 1:1 and 2:1, respectively. The complexation constants were 5.8617 × 105 M−1 and 9.328 × 105 M−1, respectively, and the detection limits were 1.3334 × 10−7 M and 1.3046 × 10−7M, respectively. In this paper, 2-amino-5-substituted-1,3,4-thiadiazole was used as a probe to detect Cr (VI) for the first time, also carried on the dipstick experiment observed with the increase of concentration, the color of the paper changed from colorless to yellow, can be used in the “naked eye” identification, the method can be more convenient and quick detection of Cr (VI) solution.