Organic Solvent Content Research Articles

Degradation and Detoxification of Chlorophenols with Different Structure by LAC-4 Laccase Purified from White-Rot Fungus Ganoderma lucidum.

A laccase named LAC-4 was purified from Ganoderma lucidum. Firstly, the enzymatic properties of purified LAC-4 laccase, and the degradation of three chlorophenol pollutants 2,6-dichlorophenol (2,6-DCP), 2,3,6-trichlorophenol (2,3,6-TCP) and 3-chlorophenol (3-CP) by LAC-4 were systematically studied. LAC-4 had a strong ability for 2,6-DCP and 2,3,6-TCP degradation. The degradation ability of LAC-4 to 3-CP was significantly lower than that of 2,6-DCP and 2,3,6-TCP. LAC-4 also had a good degradation effect on the chlorophenol mixture (2,6-DCP + 2,3,6-TCP). The results of kinetics of degradation of chlorophenols by LAC-4 suggested that the affinity of LAC-4 for 2,6-DCP was higher than 2,3,6-TCP. The catalytic efficiency and the catalytic rate of LAC-4 on 2,6-DCP were also significantly higher than 2,3,6-TCP. During degradation of 2,6-DCP and 2,3,6-TCP, LAC-4 had a strong tolerance for high concentrations of different metal salts (such as MnSO4, ZnSO4, Na2SO4, MgSO4, CuSO4, K2SO4) and organic solvents (such as ethylene glycol and glycerol). Next, detoxification of chlorophenols by LAC-4 was also systematically explored. LAC-4 treatment had a strong detoxification ability and a good detoxification effect on the phytotoxicity of individual chlorophenols (2,6-DCP, 2,3,6-TCP) and chlorophenol mixtures (2,6-DCP + 2,3,6-TCP). The phytotoxicities of 2,6-DCP, 2,3,6-TCP and chlorophenol mixtures (2,6-DCP + 2,3,6-TCP) treated with LAC-4 were considerably reduced or eliminated. Finally, we focused on the degradation mechanisms and pathways of 2,6-DCP and 2,3,6-TCP degradation by LAC-4. The putative transformation pathway of 2,6-DCP and 2,3,6-TCP catalyzed by laccase was revealed for the first time. The free radicals formed by LAC-4 oxidation of 2,6-DCP and 2,3,6-TCP produced dimers through polymerization. LAC-4 catalyzed the polymerization of 2,6-DCP and 2,3,6-TCP, forming dimer products. LAC-4 catalyzed 2,6-DCP into two main products: 2,6-dichloro-4-(2,6-dichlorophenoxy) phenol and 3,3′,5,5′-tetrachloro-4,4′-dihydroxybiphenyl. LAC-4 catalyzed 2,3,6-TCP into two main products: 2,3,6-trichloro-4-(2,3,6-trichlorophenoxy) phenol and 2,2′,3,3′,5,5′-hexachloro-[1,1′-biphenyl]-4,4′-diol.

Creation of Cross-Linked Crystals With Intermolecular Disulfide Bonds Connecting Symmetry-Related Molecules Allows Retention of Tertiary Structure in Different Solvent Conditions.

Protein crystals are generally fragile and sensitive to subtle changes such as pH, ionic strength, and/or temperature in their crystallization mother liquor. Here, using T4 phage lysozyme as a model protein, the three-dimensional rigidification of protein crystals was conducted by introducing disulfide cross-links between neighboring molecules in the crystal. The effect of cross-linking on the stability of the crystals was evaluated by microscopic observation and X-ray diffraction. When soaking the obtained cross-linked crystals into a precipitant-free solution, the crystals held their shape without dissolution and diffracted to approximately 1.1 Å resolution, comparable to that of the non-cross-linked crystals. Such cross-linked crystals maintained their diffraction even when immersed in other solutions with pH values from 4 to 10, indicating that the disulfide cross-linking made the packing contacts enforced and resulted in some mechanical strength in response to changes in the preservation conditions. Furthermore, the cross-linked crystals gained stability to permit soaking into solutions containing high concentrations of organic solvents. The results suggest the possibility of obtaining protein crystals for effective drug screening by introducing appropriate cross-linked disulfide bonds.

Formulation and optimization of polymeric agglomerates of Bosentan monohydrate by crystallo-co-agglomeration technique

BackgroundThe polymeric spherical agglomerate of Bosentan monohydrate was prepared by crystallo-co-agglomeration technique, for enhancing the micrometric properties and solubility of the drug. The agglomerates were developed using two distinct solvents, DCM as a good solvent and bridging liquid and water as a weak solvent, respectively. Hydrophilic polymer like HPMC K100M is used as a hardening agent which gives mechanical strength to the agglomerates, and PEG6000 is used as a wetting agent. Other excipients like talc which was used as a size enhancer, and PVA was used as an emulsifier agent. The formulation was optimized by Box–Behnken design. The concentration of talc and PEG6000, as well as rotation speed, was considered as independent variables. The particle size, angle of repose, and % drug content were used as dependent variables to investigate the effect of independent variables on dependent variables. The spherical crystal agglomerates were subjected to various physicochemical evaluations.ResultsThe results revealed that as the concentration of talc and PEG6000 increases, the sphericity and particle size of the agglomerates increase, and at a low agitation, speed agglomerates become more spherical and coarser, which is confirmed by FESEM. The characterization like FTIR confirms no interaction with excipients, while XRPD confirms the polymorphic changes, and gas chromatography (GC) confirms the concentration of residual organic solvents in PDE limits. The optimized formulation of SAs showed a good angle of repose which is 30.33 ± 0.35, and the % cumulative drug release at 20 min was 94.14 ± 0.628%. Finally, the FDTs of the optimized batch were prepared.ConclusionsThe comparison of the in vitro release study of pure drugs with agglomerates and fast dispersible tablets of agglomerates confirms the solubility improvement. Finally, it can be concluded that the polymorphic crystal agglomerates enhance the solubility and micrometric properties of Bosentan monohydrate.

Newly synthesized methionine aminopeptidase 2 inhibitor hinders tumor growth.

Methionine aminopeptidase 2 (MetAp2) inhibition has been recognized as a promising approach for suppressing angiogenesis and cancer progression. Small molecule fumagillol derivatives with adamantane side groups were synthesized and evaluated for MetAp2 inhibition activity, and a lead molecule with superior abilities to inhibit the enzymatic activity of MetAp2 was identified. The compound, referred to as AD-3281, effectively suppressed proliferation of cancer and endothelial cells and impaired tube formation of endothelial cells in vitro. When administered systemically, AD-3281 was well tolerated and led to a significant suppression of human melanoma and mammary tumor xenografts grown in mice. The activity in vivo was associated with reduced angiogenesis and tumor proliferation as detected histologically. In order to develop a formulation that can solubilize AD-3281 with a minimal content of organic solvents, biodegradable nanoparticles comprised of poly-lactic-co-glycolic acid (PLGA) were fabricated and characterized. Compared with the free compound, AD-3281-loaded nanoparticles showed an advantageous cellular availability and uptake, leading to higher activity in cells and better transport in three-dimensional (3D) cultures. Taken together, we introduce a novel MetAp2 inhibitor with high anti-cancer activity and a stable nano-formulation with a high potential for future clinical translation.

Application of organic gas steam-liquid extraction system for extraction and separation of uranium from water samples as a new efficient method

Abstract In this study, for the first time the organic gas steam-liquid extraction (OGS-LE) method is used as a simple, efficient and scalable to industrial application technique for the extraction and separation of uranium (VI) from aqueous samples. OGS-LE is done by a special handmade extraction cell. In this method, the organic solvent vapor produced in the evaporator unit is introduced into the aqueous sample by using nitrogen as a carrier gas. By inserting the vapor bubbles of the organic solvent into the aqueous sample, the organic solvent dissolves in water and the organic solvent concentration in water reaches supersaturation. During this process, equilibrium occurs between the dissolved organic solvent and the insoluble organic solvent, and it is collected on top of the aqueous phase. Uranium has been extracted with cyanex 272 and tetrabutylammonium bromide (TBAB) as extractant into n-heptane from the alkaline aqueous media by the OGS-LE method. Cyanex 272 and TBAB were used as the complexing ligand and the ion pairing reagent, respectively. The mechanism of extraction was proposed depending on the deprotonating of cyanex 272 and ionic interaction with the quaternary ammonium bases. Face Central Composite Design (FCCD) was used to evaluate the effect of various factors. Under the optimized conditions, uranium extraction could be completed in a single stage with the extraction efficiency of more than 90% from an aqueous solution containing alkali, alkaline Earth and transition metal ions. The precision, obtained by performing five replicates under the optimized conditions, was 90.12% ± 0.75% (percentage of extraction ± RSD).

Chromatographic properties of hydrogenated microdiamond synthesized by high pressure and high temperature

Adsorption and chromatographic properties of oxidized and hydrogenated ‘high pressure and high temperature’ synthesised diamond (HPHT) are studied using high-performance liquid chromatography. The retention factors of organic cation (benzyltributylammonium chloride), weak base (aniline), weak acid (benzoic acid), strong acid (benzenesulfonic acid), hydrophobic toluene, and hydrophilic uracil are obtained at varied pH, organic solvent content, and ionic strength of mobile phase. Both adsorbents exhibited moderate polarity with a mixed-mode retention mechanism with a combination of electrostatic, hydrophobic and hydrophilic interactions. Unexpectedly, hydrogenated HPHT revealed significant anion-exchange properties under acidic conditions and cation-exchange properties under alkaline conditions, while only cation-exchange selectivity was noted for oxidized HPHT across the enntire pH range. The retention factors obtained for a set of model compounds including n-alkyl-, polymethyl-, nitro- and halogenated benzenes correlated well with their hydrophobicity (logP) values. The thermal stability of the adsorbent and immutability of retention mechanisms involved was confirmed by linear van't Hoff plots for the investigated compounds.

Determination of diazepam in human plasma by developed and validated a high-performance liquid chromatographic ultraviolet method

Background and Aims: Diazepam is accepted as a safer drug to medicate in many serious cases, acting as an anticonvulsant, an anxiolytic and a treatment for many types of poisoning. Monitoring it is important in achieving successful treatment and reducing the risk of toxic effects. In this study, it is aimed to develop and validate a sensitive, repeatable, and reliable method based on high-performance liquid chromatographic analysis for the determination in human plasma. Methods: Separation was carried out using a reverse-phase C18 column (4.0 mm x 150 mm, 3 μm) at 30 °C. The solution was prepared with a 10 mM phosphate buffer and acetonitrile (1:1, v/v) was employed as a mobile phase at the isocratic flow with 0.5 mL/min rate. Quantification was applied at 230 nm. A solid-phase extraction method was established and optimized, which was then used in the preparation of the plasma (0.5 mL) samples to the analysis. Results: The method was found to be linear (r2 = 0.9805) between 100 and 1200 ng/mL. The analysis run was ≤12 min. Intraday and inter-day accuracy were found between -5.78 and 5.93 and precision was ≤1.82%. The limit of detection and quantification were calculated as 20.42 and 61.86 ng/mL, respectively. Recovery was found between the range of 95.12% and 106.83%. The method was determined to be robust according to changes in UV, mobile phase organic solvent content, mobile phase pH, column temperature, and operator. Conclusion: This simple, sensitive and reliable method is suggested for accredited-reference laboratories working on the therapeutic drug monitorization and/or overdose-toxicological quantified analysis of diazepam in human plasma.

Method development and optimization for measuring chymotrypsin and chymotrypsin inhibitor activities.

Protease inhibitors of protein nature are rich in seeds of legume crops. There are two common types: Kunitz inhibitor, which mainly inhibits trypsin, and Bowman-Birk inhibitor, which inhibits both trypsin and chymotrypsin. Historically, trypsin inhibitor activity in legume products has been of primary interest for measurement. However, as plant proteins are increasingly used for food or feed in recent years, there is a growing interest in monitoring chymotrypsin inhibitor activity (CIA) in these products as well. Reported methods for CIA assay vary greatly and are incompletely described. No standardized or official method is available. The present study focused on developing a robust method for accurately measuring CIA, using N-benzoyl-L-tyrosine p-nitroanilide (BTpNA) as a substrate. Since BTpNA is not water soluble, a water-miscible organic solvent must be present. After investigating the effects of several factors, such as absorption spectra, organic solvent type and concentration, substrate and enzyme concentrations, inhibitor levels (which affected % chymotrypsin inhibition), the sequence of adding reagents, extractant and extraction time, and so forth, an optimized method for CIA measurement was finally developed. It features dimethylformamide as the organic solvent, the enzyme-last sequence, 5ml total assay volume, and calculation of the inhibitor activity based on 40% chymotrypsin inhibition. The method can also be slightly modified for measuring chymotrypsin activity. The robust performance of the method was verified by measuring 11 assorted protein products, paving a way for standardization. PRACTICAL APPLICATION: With an increasing use of plant proteins, there is an urgent need to measure chymotrypsin inhibitor activity in various protein products with accuracy. After thoroughly investigating several factors, an optimized method for measuring chymotrypsin inhibitor activity in various protein products was developed. The proposed method is sensitive and robust, providing a basis for standardization. It can also be used for measuring chymotrypsin activity.

Phenolic and flavonoid compounds extraction from Calophyllum inophyllum leaves

Calophyllum inophyllum has been known as a part of the mangrove forest area. This species is distributed primarily in the coastal regions of Indonesia and Africa. It is rich in bioactive compounds and has been used as a traditional medication. This work employed a single replicate of the one-factor-at-a-time experiment method to investigate optimum conditions, which resulted in the highest TPC. The three factors studied were organic solvent type (acetone, ethanol, and methanol), organic solvent concentration in water (50–100%, v/v), and extraction temperature (30–60 °C). The extraction was conducted with the percolation method. The result shows that organic solvent type, organic solvent concentration in water, and extraction temperature significantly affect the TPC, TFC, and the yield of crude extract obtained. The highest TPC (289.12 mg GAE/g of the residue of C. inophyllum leaves) was achieved with 80% methanol in water at 30 °C for 48 h. Under this condition, TFC value of 410.4 mg QE/g of the residue of C. inophyllum leaves, the yield of 2.41%, and IC50 value of 0.054 µg/mL were achieved. Moreover, bis (2-ethylhexyl) phthalate was firstly detected in the extract.

Phenolics, proteins, antioxidant activity and GC – MS analysis of Artocarpus heterophyllus Lam seeds

Artocarpus heterophyllus seeds are available in larger quantity and are good source for many phytochemicals. The seeds are rich in proteins and low in fat content. The present study was carried out to analyse the phenolics, proteins and antioxidant activity of A. heterophyllus seeds. Different aqueous solvents such as acetate buffer pH 5.0, phosphate buffer pH 7.0, tris buffer pH 8.5, different concentration of sodium hydroxide (0.05M, 0.1M, 0.2M, 0.3M, 0.4M, 0.5M), sodium chloride, water and organic solvents like ethanol, methanol and acetone were used for extraction. Sodium hydroxide (0.1M) showed maximum extraction efficiency. Among the organic solvents, ethanol showed maximum phytochemical extraction. Different concentrations of ethanol (20%, 40%, 60%, 80%) containing 0.1M NaOH were also used for extraction and maximum extraction was found in 40% ethanol containing 0.1M NaOH. GC – MS analysis was carried to identify various bioactive compounds present in the extracts (hexane, ethyl acetate, methanol and water) of the seeds.

Anthropogenic Contamination of the Atoyac River, México

The Atoyac River that crosses Puebla-Tlaxcala in Mexico shows a severe state of contamination, however, this situation has been scarcely studied. The objective of this work was to evaluate the pollutants in the Atoyac River (physicochemical parameters, heavy metals and volatile solvents) in three areas that comprise the state of Puebla and Tlaxcala from samples collected in August 2019. The study areas were San Cristóbal Tepetlaxco Puebla (Zone 1), San Martín Texmelucan Puebla (Zone 2) and Villa Alta Tlaxcala (Zone 3). The results of the determination of the physicochemical parameters (Temperature, pH, Conductivity, Turbidity, COD, BOD5 and DO), heavy metals and volatile organic solvents reveal that Zone 1 represents the least contaminated area while Zone 3 has a critical contamination due to the presence of physicochemical values and concentrations of heavy metals and organic solvents that exceed the limits allowed by the Official Mexican Standards. Therefore, our results suggest that the Atoyac River is affected in a heterogeneous way. Observing the increase in pollution dramatically and progressively. Hence, it is urgent to generate information that serves as evidence to make recommendations to curb excessive industrial and municipal pollution, which can cause problems for the environment and health of the population.

Разработка методики определения содержания остаточных органических растворителей в новой фармацевтической субстанции кислоты 3-(1H-бензимидазол-2-ил)-1,2,2-триметилциклопентан-карбоновой

Objective. Organic solvents, which often have toxic and/or carcinogenic properties, are used at all stages of the production of pharmaceutical substances - synthesis, isolation and purification - and are not completely removed after the completion of the technological process. The presence of even extremely small amounts of such compounds in medicines can be dangerous for patients. The article presents the results of the development of a method for determining the content of residual organic solvents (ROS) - ethanol, toluene and dimethylformamide - in a new active pharmaceutical ingredient (API) 3-(1H-benzimidazol-2-yl)-1,2,2-trimethylcyclopentane-carboxylic acid by gas chromatography. Materials and methods. Static vapor phase analysis was used to identify and to quantify residual organic solvents. It was determined by the internal standard method using a Shimadzu GC-2014ATF/SPL gas chromatograph with an AOC-6000Plus autosampler; PID detection. Isobutyl alcohol was used as an internal standard. Results. The developed method was used to determine the content of residual organic solvents in the validation series of the new pharmaceutical substance 3-(1H-benzimidazol-2-yl)-1,2,2-trimethylcyclopentane-carboxylic acid. The method was validated in accordance with the requirements of the State Pharmacopoeia of the Russian Federation. Conclusion. The developed method is suitable for further use in quality control in the production of 3-(1H-benzimidazol-2-yl)-1,2,2-trimethylcyclopentane-carboxylic acid.

Non-destructive measurement technique for water content in organic solvents based on a thermal approach.

The water content of organic solvents is one of the crucial properties that affect the quality of the products and the efficiency of the manufacturing processes. The established water determination methods such as Karl Fischer titration and gas chromatography require skilled operators, specific reagents, and prolonged measurement time. Thus, they are not suitable for both on-line and in-line applications. In this study, we aim to develop a real-time and low-cost device with reliable accuracy. The proposed device based on a newly developed thermal approach could non-destructively detect the water content in multiple organic solvents at low concentrations with high accuracy and without the use of any specific reagent. Experiments were performed for the determination of water content in organic solvents such as methanol, ethanol, and isopropanol. The results show that the proposed device is feasible for the water content determination in methanol, ethanol, and isopropanol at 0–1% w/w. A Bland–Altman plot to illustrate the differences in measurements between the proposed device and coulometric Karl Fischer titration shows that most of the measurements lie within the limits of agreement where 95% of the differences between the two methods are expected to fall in the range of −0.13% and 0.09%.

Continuous kilogram-scale process for the synthesis strategy of 1,3,5-trimethyl-2-nitrobenzene in microreactor

1,3,5-trimethyl-2-nitrobenzene is a valuable synthetic intermediate with essential applications in the dyes industry. Because of poor micro-mixing and the large consumption of waste acid using the traditional reactor, the content of impurity and the yield of 1,3,5-trimethyl-2-nitrobenzene are not stable. Therefore, a continuous kilogram-scale process for the synthesis strategy of 1,3,5-trimethyl-2-nitrobenzene in microreactor was reported in this paper. Two microreactors and three pumps quickly assemble the microflow system. Mesitylene was first mixed with nitric acid and then combined with sulfuric acid under-designed experimental parameters. The effects of process parameters in the three synthetic strategies, including an organic solvent, temperature, molar ratio, flow rate, and sulfuric acid content, were systemically investigated. Based on the results of process parameter optimization, the production of 1,3,5-trimethyl-2-nitrobenzene at the kilogram level was achieved in a microreactor with two microreactors in series. Compared with the traditional batch reactor, sulfuric acid consumption was decreased by 7.6 times, and the reaction time was reduced from 4h to 60s. Compared with the synthesis methods reported in the literature, the two-step synthesis method proposed in this paper has better advantages in terms of reaction time, product purity, and conversion rate. It provides a new synthetic strategy for the industrial production of aromatic compounds by nitration reaction.

Assessing target engagement using proteome-wide solvent shift assays.

Recent advances in mass spectrometry (MS) have enabled quantitative proteomics to become a powerful tool in the field of drug discovery, especially when applied toward proteome-wide target engagement studies. Similar to temperature gradients, increasing concentrations of organic solvents stimulate unfolding and precipitation of the cellular proteome. This property can be influenced by physical association with ligands and other molecules, making individual proteins more or less susceptible to solvent-induced denaturation. Herein, we report the development of proteome-wide solvent shift assays by combining the principles of solvent-induced precipitation (Zhang et al., 2020) with modern quantitative proteomics. Using this approach, we developed solvent proteome profiling (SPP), which is capable of establishing target engagement through analysis of SPP denaturation curves. We readily identified the specific targets of compounds with known mechanisms of action. As a further efficiency boost, we applied the concept of area under the curve analysis to develop solvent proteome integral solubility alteration (solvent-PISA) and demonstrate that this approach can serve as a reliable surrogate for SPP. We propose that by combining SPP with alternative methods, like thermal proteome profiling, it will be possible to increase the absolute number of high-quality melting curves that are attainable by either approach individually, thereby increasing the fraction of the proteome that can be screened for evidence of ligand binding.

Optimized protocols for assessing libraries of poorly soluble sortase A inhibitors for antibacterial activity against medically-relevant bacteria, toxicity and enzyme inhibition

Increasing antimicrobial resistance is a major global health concern. Conventional antibiotics apply selection pressures, which promote the accumulation of resistant microbes. Anti-virulence strategies, in contrast, are less potent antimicrobials, but are less likely to select for resistance, can be combined with existing antibiotics to improve their activity, and in some cases can overcome antimicrobial resistance towards other antimicrobials. Sortase A inhibitors (SrtAIs) represent an exciting example of this class; however, many reported examples demonstrate poor water solubility, which complicates their biological assessment and activity. This includes reports that use antimicrobial concentrations of organic solvents or conditions that fail to solubilise these compounds for minimal inhibitory concentration (MIC) assessments. Herein, we report the first study to optimise screening processes for a library of prospective SrtAIs (trans-chalcone (TC), berberine (BR), curcumin (CUR), and quercetin (QC)), including comparative assessment of the effects of various co-solvent concentrations, along with comparative assessment of their antimicrobial activities against multiple disease relevant bacterial strains (methicillin-sensitive and resistant S. aureus, E. coli, and P. aeruginosa), inhibition of the sortase A enzyme, and toxicity towards mammalian cells (HEK-293), using these optimised conditions. Optimal solubility with minimal effect on bacterial viability was observed in the presence of 5% (v/v) dimethyl sulfoxide (DMSO)-Mueller-Hinton Broth. Three antimicrobial susceptibility tests (broth microdilution, agar dilution, and disk diffusion) were assessed for their ability to accurately determine minimal inhibitory concentration (MIC) data for each SrtAI. Broth microdilution and agar dilution were both effective; however, the broth microdilution assay required the addition of a colorimetric metabolic indicator (resazurin) to enable simple and reliable MIC determination due to the development of precipitants over time. In contrast, disk diffusion did not provide reliable zone of inhibition data. Identical MIC data was observed with methicillin-sensitive and -resistant S. aureus (MRSA; ATCC43300), with lower potency activity against E. coli and P. aeruginosa. Under these conditions, TC and CUR demonstrated significant toxicity towards human embryonic kidney (HEK-293) cells, with QC showing less toxicity and BR limited-to-no toxicity at its MIC. Overall, the findings of this work provide optimised processes, which will prove useful for the study of other poorly soluble antimicrobial agents and SrtAIs. The obtained data suggests that BR should be considered in preference to the other SrtAIs for the development of new antimicrobial formulations, based on its superior antimicrobial and SrtA inhibition potency, and greatly reduced toxicity.

Fluoride Ion-Selective Electrode for Organic Solutions.

Fluoride ions are used in battery electrolytes in fluoride shuttle batteries. Since organic solvents are used in battery electrolytes, there is a growing demand to develop appropriate methods for quantifying fluoride ion concentration in organic solvents. In this study, a fluoride ion-selective electrode (ISE) for organic solutions is proposed as an electrode of the second kind. A Ag|AgF electrode was made via the anodization of a silver wire in propylene carbonate (PC) containing dissolved fluoride ions. The resultant electrode exhibits a stable linear response of the open circuit potential to the logarithm of the fluoride ion concentration in PC solutions over a range of 10-4-10-2 mol dm-3. The lower and upper limits of the linear response were interpreted in terms of the solubility and the formation of a silver fluoride complex. The use of this electrode of the second kind is suitable for the analysis of fluoride ions in organic solutions and is a promising concept for the development of ISEs for the detection of ions in organic solutions under highly restrictive conditions.

Design and optimization of sensitive analytical spectrophotometric method for micro determination of copper(II) from e-waste by using of novel chromogenic extractant

In this article, a novel spectrophotometric reagent 1-(pyrimidine)-4, 4, 6-trimethyl-1,4-dihydropyrimidine-2-thiol [PTPT] has been synthesized for liquid–liquid extraction and spectrophotometric determination of copper(II). The as-synthesized ligand has been selectively forms stable complex with copper(II) in basic medium (pH 9.0), in presence of mild pyridine the extraction and color stability has found to be synergistically enhanced. The equilibrium time is 10 min for effective extraction of copper(II) from organic phase and absorbance of colored organic complex in carbon tetrachloride is measured spectrophotometrically at λmax 615 nm against reagent blank. The ternary complex of Cu(II)-PTPT-Py having molar ratio 1:2:2 (M:L:Py) showed green colored complex. The main factors influencing the achievement of synergistic extraction; i.e. pH, ligand concentration, type and volume of the dispersive organic solvents, equilibrium time, synergent concentration and foreign ions were investigated.The Beer’s law was obeyed in the concentration range 1–20 μg mL−1 of copper(II) and optimum concentration range is evaluated by Ringbom’s plot and it is found that 2.5–25 μg mL−1. In presence of pyridine, molar absorptivity and Sandell’s sensitivity of copper(II)-PTPT complex is 2.80 × 103 L mol−1 cm−1 and 0.226 μg cm−2, respectively and in absence of pyridine, molar absorptivity and Sandell’s sensitivity of copper(II)-PTPT complex is 1.35 × 103 L mol−1 cm−1 and 0.469 μg cm−2, respectively. The stoichiometry of the copper(II)-PTPT-pyridine complex was calculated by slope ratio method, mole ratio method and Job’s method of continuous variation and it has been found as 1:2:2. No significant effects of potentially interfering species i.e. cations and anions were observed. The optimized method was applied for the determination of copper(II) in binary, synthetic mixtures and successfully applied for determination of copper(II) from e-waste samples. The standard deviation (R.S.D.) is 0.11% for n = 5 repetition. The reliability of the developed method is confirmed by comparison of experimental results with atomic absorption spectrophotometer.

Ion exchange removal and resin regeneration to treat per- and polyfluoroalkyl ether acids and other emerging PFAS in drinking water

Ion exchange (IX) is a promising technology to remove legacy anionic per- and polyfluoroalkyl substances (PFAS) from water. As increasing numbers of per- and polyfluoroalkyl ether acids (PFEA) and other emerging PFAS were detected in the environment, it is necessary to understand how well IX resins remove these emerging PFAS for drinking water treatment. In this study, nine commercially available IX resins were tested to treat a drinking water source spiked with 40 legacy and emerging PFAS at 600 ng/L, including PFEA, perfluoroalkyl carboxylic and sulfonic acids, fluorotelomer sulfonic acids, perfluoroalkane sulfonamides, perfluoroalkane sulfonamidoacetic acids, and zwitterionic species. With limited contact time (15 min), PFAS properties such as the fluorinated chain length, charge, and functional groups all affected PFAS adsorption to resins. However, the impact of PFAS properties on PFAS removal became less pronounced when the contact time increased beyond 2 h, while the resin polymer matrix became the critical factor for PFAS removal. All five tested polystyrene-divinylbenzene (PS-DVB) resins achieved more than 90% removal in 24 h of 35 PFAS compounds, while polymethacrylate and polyacrylic resins achieved >90% removal for less than half of the compounds. Regenerating PS-DVB resin was investigated using different salt species, regenerant pH, brine concentrations, and methanol contents. Sodium chloride and ammonium chloride were found the best brines for regenerating the tested resins. Increasing brine concentrations enhanced the regeneration efficiency, especially for short-chain PFAS. Using simple salt regenerants, up to 94% of selected short-chain PFAS was released from resins designed for general water treatment, but no meaningful regeneration was achieved for long-chain PFAS or PFAS-specific resins when the organic solvent content was less than 20%.

Thermostable lipases and their dynamics of improved enzymatic properties.

Thermal stability is one of the most desirable characteristics in the search for novel lipases. The search for thermophilic microorganisms for synthesising functional enzyme biocatalysts with the ability to withstand high temperature, and capacity to maintain their native state in extreme conditions opens up new opportunities for their biotechnological applications. Thermophilic organisms are one of the most favoured organisms, whose distinctive characteristics are extremely related to their cellular constituent particularly biologically active proteins. Modifications on the enzyme structure are critical in optimizing the stability of enzyme to thermophilic conditions. Thermostable lipases are one of the most favourable enzymes used in food industries, pharmaceutical field, and actively been studied as potential biocatalyst in biodiesel production and other biotechnology application. Particularly, there is a trade-off between the use of enzymes in high concentration of organic solvents and product generation. Enhancement of the enzyme stability needs to be achieved for them to maintain their enzymatic activity regardless the environment. Various approaches on protein modification applied since decades ago conveyed a better understanding on how to improve the enzymatic properties in thermophilic bacteria. In fact, preliminary approach using advanced computational analysis is practically conducted before any modification is being performed experimentally. Apart from that, isolation of novel extremozymes from various microorganisms are offering great frontier in explaining the crucial native interaction within the molecules which could help in protein engineering. In this review, the thermostability prospect of lipases and the utility of protein engineering insights into achieving functional industrial usefulness at their high temperature habitat are highlighted. Similarly, the underlying thermodynamic and structural basis that defines the forces that stabilize these thermostable lipase is discussed. KEY POINTS: • The dynamics of lipases contributes to their non-covalent interactions and structural stability. • Thermostability can be enhanced by well-established genetic tools for improved kinetic efficiency. • Molecular dynamics greatly provides structure-function insights on thermodynamics of lipase.