Buffer Solvent Research Articles

Laccase-Catalyzed Cycloaddition (LaCCA) Reaction: An Efficient Green Approach for Synthesizing Mono- and Bis-(1,4-Disubstituted-1,2,3-Triazoles) via Click Chemistry—In Silico Molecular Docking and Druglikeness Assessment

Background: Mono- and bis-(1,4-disubstituted-1,2,3-triazoles) were synthesized via a laccase-catalyzed reaction using Trametes versicolor. This methodology offers a convenient and efficient approach to triazole synthesis under mild conditions, achieving modest to good yields. Additionally, molecular docking studies were performed using PDB IDs 2W9S (antibacterial) and 3KHM (antifungal) to evaluate biological activities. The results of drug-likeness analysis further corroborated the findings from experimental biological evaluations. Methods: This study focuses on developing an eco-friendly method for synthesizing novel 1,2,3- triazole derivatives using a green catalyst. A co-solvent buffer and organic solvent facilitate the reaction, which performs well with various substrates, including substituted benzenes (-ortho, -meta & para-mono & bis-(2-propynyloxy), sodium azide, and aryl halides. Laccase enzymes from Trametes versicolor are used, leveraging naturally occurring copper metals instead of external transition metals, bound through histidine, methionine, and cysteine linkages. This method represents a sustainable approach to organic transformations. Result: New scaffolds of mono- and bis-(1,4-disubstituted-1,2,3-triazoles) were synthesized using eco-friendly green buffer solvents and laccase catalysis with aryl halides, sodium azide, and acetylene derivatives. Molecular docking studies revealed that the binding affinities of the synthesized compounds (1-14) show promising interactions with antibacterial and antifungal proteins. All others except for compounds 6, 7, 8, 12, and 13, meet Lipinski’s criteria, making them potential therapeutic candidates. Conclusion: In conclusion, this methodology is valuable for developing antibacterial and antifungal agents in medicinal chemistry. Additionally, microwave-assisted synthesis of (2-propenyloxy)benzene derivatives significantly reduced reaction times from hours to minutes. The approach is environmentally friendly and practical, particularly for handling flammable organic azides and hazardous solvents, making it both efficient and safer.

Capillary electrophoresis separations with Betaine:Urea, a deep eutectic solvent as the separation medium

BackgroundCapillary electrophoresis (CE) is a highly versatile separation technique widely used in analytical chemistry. Traditionally, CE can be categorized as either aqueous or non-aqueous systems based on the buffer solvents employed. For decades, non-aqueous CE has been predominantly associated with the use of organic solvents, a perception deeply ingrained in the scientific community. However, growing concerns about the health and environmental impacts of these solvents, driven by the principles of green chemistry, have prompted a reevaluation of their use. In response to these concerns, our group recently introduced a deep eutectic solvent (DES), specifically Proline:Urea, as an innovative and eco-friendly separation medium for CE. This approach not only enhances the sustainability of CE separations but also offers a new perspective for the development of innovative CE separation media. ResultsBuilding on our previous work, here we report the use of the second DES, Betaine:Urea (BU), as a new separation medium that offers further improved performance for CE applications. The DES was systematically characterized, with key physical properties relevant to CE separations, such as thermal properties, viscosity, dielectric constant, Joule heating effect, and UV transmittance, being thoroughly examined. Using a complex sample of 10 structurally similar naphthalene derivatives, we demonstrated the efficiency of BU in capillary zone electrophoresis (CZE) for separating analytes with varying charges (including cations, neutrals, and anions) and sizes. Additionally, we established the first micellar electrokinetic chromatography (MEKC) system in this DES using sodium dodecyl sulfate (SDS) as the surfactant. This system successfully resolved 6 structurally similar neutrals that could not be separated by conventional aqueous SDS-MEKC, highlighting the versatility of this DES-type separation medium. Furthermore, BU showed several advantages over the previously reported DES, Proline:Urea, particularly in terms of stability, viscosity, and Joule heating effects. SignificanceThis study holds the potential to challenge the traditional notion that “CE separation media are merely categorized into aqueous and organic solvents”. Given that DESs are “designer” solvents with highly tunable properties and environmentally friendly characteristics, the introduction of BU as a viable alternative to traditional solvents not only expands the media available for CE separations, but also offers a more efficient and potentially more sustainable option for specific analyses.

The series of L-lysine-derived gelators-modified multifunctional chromatography stationary phase for separation of chiral and achiral compounds

In this study, using chiral L-lysine as the molecular skeleton, three kinds of L-lysine-derived gelators (GBLB, GBLF and GFLF) were synthesized and then bonded to the surface of silica matrix (5 μm) by amide condensation to prepare a series of multifunctional chromatography stationary phases (GBLB-SiO2, GBLF-SiO2, and GFLF-SiO2) were prepared. The L-lysine-derived gelators not only possess chiral recognition ability, but also can spontaneously form oriented and ordered network structures in liquid medium through the interaction of non-covalent bonding forces such as hydrogen bonding, π-π stacking, and van der Waals forces. The comprehensive effect of multiple weak interaction sites enhances the molecular recognition ability and further improves the separation diversity of different types of compounds on stationary phases. The separation and evaluation of chiral compounds showed that benzoin, 1-phenyl-ethanol, 1-phenyl-propanol and 6-hydroxyflavanone could be separated in normal phase mode (NPLC). The separation of different types of non-chiral compounds, such as sulfonamides, nucleosides, nucleobases, polycyclic aromatic hydrocarbons (PAHs), anilines, and aromatic acids, were achieved in hydrophilic interaction/reversed-phase/ion-exchange mode (HILIC/RPLC/IEC), and the separation of polarized compounds could be performed under the condition of ultrapure water as the mobile phase, which has the typical retention characteristics of per aqueous liquid chromatography (PALC). The effects of organic solvent content, temperature, pH value, and buffer salt concentration on the retention and separation performance of the column were investigated. Comparison of the three prepared columns showed that the separation performance (such as aromatic selectivity) could be improved by increasing the types of functional groups on the surface of the stationary phase and the number of aromatic groups. In a word, the prepared stationary phase have multiple retention properties, can simultaneously separate chiral compounds and various types of achiral compounds. This work provides an idea for developing multifunctional liquid chromatography stationary phase materials, and further expands the application of gelators in separation science.

Fluorescence based methodology with greenness consideration for concurrent estimation of anti-allergic medication; application to dosage form

A green, sensitive and rapid spectrofluorimetric method for quantitative assay of an anti-allergic medication composed of montelukast and fexofenadine mixture in raw materials and dosage form was developed. The method was based on measuring the synchronous fluorimetric peak without interference, pre-separation or pre-extraction procedures. Montelukast was analyzed at 360 nm while fexofenadine was measured at 263 nm using Δλ = 20 nm for both drugs using ethanol as diluting solvent and acetate buffer of pH 4. The assay was rectilinear over the concentration range of 1.0–10.0 μg/mL for fexofenadine and 0.1–0.6 μg/mL for montelukast. The method was full validated according to ICH guidelines. The applicability of the method enables the assay of both drugs in raw materials, synthetic mixture as well as combined tablets. Moreover, the greenness of the method was assessed using different methods including; analytical eco-scale, GAPI and AGREE. All of these methods confirm that the proposed method is an eco-friendly method.

Green Analytical HPLC Method Development of Acyclovir Loaded Floating Raft Formulation in Spiked Rabbit Plasma

Objective: The need of this investigation is to design eco-friendly, sensitive, and precise bioanalytical high-performance liquid chromatography (HPLC) techniques that leverage green analytical tools such as green analytical procedure index (GAPI), analytical eco scale (AES), and analytical greenness metric (AGREE) to analyze ACV-spiked rabbit plasma and ACV-loaded floating raft formulation (FRF) because The literature survey revealed insufficient data for the HPLC approach to FRF. Method: Methods involving plasma spikes mirroring the in-vivo models provide insights into potential real-life scenarios and the functionality of floating raft formulations loaded with ACV. The Design Expert tool optimized critical process parameters and identified significant factors influencing the chromatographic technique. Results: The CCD was used to optimize the flow rate (0.6 mL/min) and buffer solvent ratio (99:1) for separation. The C18 column (250 X 4.6 mm) was utilized to achieve the elution of ACV. The developed method was thoroughly validated through ICH guidelines. The ACV, lower limit of detection (LLoD), and lower limit of quantitation (LLoQ) retention times were established at 2.3 minutes, 15, and 20 ng/mL, respectively. Discussion: In summary, the study demonstrated the exceptional performance sensitivity, specificity, and robustness of the bioanalytical method. The method proved highly effective in quantifying ACV in plasma samples in terms of revalidatability, transferability, reproducibility, and the product development cycle. The developed method proves that using both design of experiments (DoE) and green analytical chemistry together creates a valid, eco-friendly, and reliable way to analyze the making of an ACV-loaded floating raft formulation.

Unveiling mechanisms in Cu2O-catalyzed electroreduction of CO2 through theoretical resolution using periodic boundary and saturation cluster models

The imperative need to reduce atmospheric CO2 to mitigate global warming and advance sustainable energy systems has driven extensive research. Copper oxide (Cu2O) has emerged as a promising catalyst for electroreduction of CO2, yet its catalytic mechanism remains debated. This study employs a theoretical approach to delve into the intricate details of CO2 electroreduction catalyzed by Cu2O. Utilizing both periodic boundary and saturation cluster models, we explore various reaction pathways, successfully identifying key transition states and intermediates with each model. A comprehensive analysis and comparison of results from both models are conducted. To enhance understanding, we develop a method simulating the impact of an electric field, employed to probe the ongoing reaction. Additionally, we consider the solid–liquid interface by introducing solvent molecules and buffer ions into our analysis. This comprehensive theoretical investigation aims to elucidate the mechanism governing the electroreduction of CO2 catalyzed by Cu2O and analogous semiconductor oxides, providing valuable insights into this critical process.

A Multi-step High-Performance Liquid Chromatography (HPLC) Technique for the Extraction and Purification of Medical-Grade Cyclosporine A

Cyclosporine A (CsA), a potent immunosuppressive drug, is used to treat autoimmune diseases and prevent organ transplant recipients from rejecting their new organs. Maintaining CsA's uniformity and purity is essential to maintaining its therapeutic efficacy and safety. Impurities and contaminants in CsA formulations can exacerbate side effects and patient toxicity. Purification processes can improve the safety profile of the drug and reduce the likelihood of adverse effects by eliminating impurities. Using High-performance liquid chromatography (HPLC) methods, CsA has been isolated and refined from crude in recent years. However, after the procedure, the CsA purity was not at its best. To solve this issue, this work employs a multi-step HPLC method to increase purity levels to above 95%. When exploring the HPLC detection conditions of CsA, we found that the method from the Chinese pharmacopoeia: acetonitrile-water-tert-butyl methyl ether-phosphoric acid (430 : 520 : 50 : 1) was a better mobile phase solution, our further research, including the substitution of tert-butyl methyl ether with other buffer solvents, showed no significant improvement. At the same time, we established that the key factor affecting its separation was temperature. When the temperature is lower than 70 ℃, the HPLC separation effect worsens, the retention time increases, and the peak width becomes longer. Finally, the utilization of acetonitrile-water-tert-butyl methyl ether-phosphoric acid (430 : 520 : 50 : 1) as the mobile phase with a column temperature of 70 °C, petroleum ether: acetic acid Ethyl ester (70 : 30) as the mobile phase, and filling the φ 40 mm × 500 mm chromatography column using a 40~60 μm silica gel so that a 10 : 1 height-to-diameter ratio of the packed part is obtained, under normal temperature conditions, resulted in an average cyclosporine A yield of 80.1%. The corresponding average purity was 97.2%, of which the first isolation yield was 82.3%, and the purity was 98.1%.

Capillary electrophoresis separations with deep eutectic solvents as greener separation media: A proof-of-concept study

Capillary electrophoresis (CE) has conventionally been classified into aqueous and non-aqueous categories based on the types of buffer solvents employed. Traditionally, non-aqueous CE has always been associated with the use of organic solvents, which are considered hazardous to health and environmentally detrimental. In this work, we introduce deep eutectic solvents (DESs) as CE separation media for the first time, presenting a novel and environmentally friendly approach to CE separations. The DES employed consists of proline and urea (Proline:Urea, PU), both of which are naturally occurring compounds that are readily available, cost-effective, and environmentally benign. Various fundamental aspects of the DES-type CE media were investigated, including thermal property, viscosity, electroconductivity, Joule heating effect, and compatibility with detectors. A simulated complex mixture of ten naphthalene-based compounds with varied charges and sizes was separated using the DES-based medium in capillary zone electrophoresis (CZE) mode. Moreover, we also established a DES-based micellar electrokinetic chromatography (MEKC) system utilizing Tween-20 as the surfactant. Six structurally similar naphthalene derivatives (isomers) that couldn't be resolved by CZE were effectively separated due to their strong hydrophobic interaction with Tween-20 micelles within the DES medium. Given that DESs are “designer” solvents with highly tunable properties and environmentally friendly characteristics, this study demonstrates the potential of employing DESs as an alternative to organic solvents for greener CE separations.

A Cyanoalkyl Silicone GC Stationary-Phase Polymer as an Extractant for Dispersive Liquid–Liquid Microextraction

In this work, three cyanoalkyl silicone GC stationary-phase polymers, namely OV-105, OV-225, and OV-275, were investigated as potential extractants for dispersive liquid–liquid microextraction (DLLME). The OV-225 polymer (cyanopropylmethyl-phenylmethylsilicone) exhibited the cleanest chromatographic background and was extensively studied. The proposed polymer was tested through the DLLME of four non-steroidal anti-inflammatory drugs from aqueous samples, followed by HPLC separation with UV detection at 230 nm. To achieve the maximum enrichment, the experimental conditions that influence the DLLME process were optimized using one-factor-at-a-time and design-of-experiment (DoE) approaches. The extraction variables (polymer mass, dispersive solvent volume, buffer pH, and mixing time) were screened by implementing a two-level full factorial design (FFD). Significant variables were fine-tuned using response surface methodology based on a face-centered central composite design (CCD). The optimum conditions were 10 mg of polymer (extraction medium); 50 µL of tetrahydrofuran (dispersive solvent); 100 µL of phosphate buffer pH 2.75 ([PO43−] = 100 mM); and 3 min of vortex mixing. The addition of salt had a minimal effect on the enrichment factors. In the optimum conditions, enrichment factors up to 46 were achieved using 1.5 mL samples. Calibration curves exhibited correlation coefficients > 0.999 using 4-pentylbenzoic acid as an internal standard. The limits of quantitation were 5 ng/mL for naproxen, 10 ng/mL for diflunisal, 25 ng/mL for indomethacin, and 75 ng/mL for ibuprofen. The analysis of spiked tap water samples showed adequate relative recoveries and precision. In conclusion, the proposed polymer (OV-225) is a potential greener alternative to traditional organic extractants used in DLLME.

Structural stability of DNA origami nanostructures in organic solvents.

DNA origami nanostructures have attracted significant attention as an innovative tool in a variety of research areas, spanning from nanophotonics to bottom-up nanofabrication. However, the use of DNA origami is often restricted by their rather limited structural stability in application-specific conditions. The structural integrity of DNA origami is known to be superstructure-dependent, and the integrity is influenced by various external factors, for example cation concentration, temperature, and presence of nucleases. Given the necessity to functionalize DNA origami also with non-water-soluble entities, it is important to acquire knowledge of the structural stability of DNA origami in various organic solvents. Therefore, we herein systematically investigate the post-folding DNA origami stability in a variety of polar, water-miscible solvents, including acetone, ethanol, DMF, and DMSO. Our results suggest that the structural integrity of DNA origami in organic solvents is both superstructure-dependent and dependent on the properties of the organic solvent. In addition, DNA origami are generally more resistant to added organic solvents in folding buffer compared to that in deionized water. DNA origami stability can be maintained in up to 25-40% DMF or DMSO and up to 70-90% acetone or ethanol, with the highest overall stability observed in acetone. By rationally selecting both the DNA origami design and the solvent, the DNA origami stability can be maintained in high concentrations of organic solvents, which paves the way for more extensive use of non-water-soluble compounds for DNA origami functionalization and complexation.

Development, Optimization, and Validation of a RP-HPLC Method with PDA Detection for the Concurrent Quantification of Emtricitabine, Tenofovir Alafenamide, and Dolutegravir in Both Bulk and Pharmaceutical Dosage Forms

A simple, quick, precise and accurate HPLC (reverse phase) approach has been designed and optimized using a chemometric tool to estimate dolutegravir, emtricitabine and tenofovir alafenamide, respectively. A design of central composite was used to optimize the response surface. As a result of trial and error, the parameters such as rate of solvent flow, buffer pH, and methanol concentration in the solvent system were determined. System responsiveness was estimated using the optimization process’s capacity factor, resolution, and retention time. The separation was achieved by using a solvent system containing 58.90% methanol and 41.10 triethylamine buffer (4.56 pH) at the rate of flow of 0.8 mL per minute on a phenomenex carbon (18) column (150.4 4.6 mm; I.D., 5) under optimal conditions. The duration of retention for emtricitabine was 2.91 minutes, for tenofovir alafenamide it was 6.114 minutes; and for dolutegravir it was 8.824 minutes. A correlation coefficient of 0.9998, 0.9997, and 0.9999 was determined for emtricitabine’s calibration curves from 40 to 200 g/mL, tenofovir alafenamide’s from 5 to 25 g/mL, and emtricitabine’s from 10 to 50 g/mL, respectively. This approach was effective in estimating the simultaneous doses of medications in commercial combination forms

Chronoamperometry-induced transmittance changes approach to detect aqueous sodium ion solutions using tungsten oxide thin films

A simple, inexpensive method to detect sodium ions from aqueous solutions is reported in this paper. The method of detection based on transmittance changes observed in tungsten oxide films on.Tungsten oxide is deposited on ITO glass substrate by continuous electrodeposition method from Peroxo Tungstic Acid precursor. Chronoamperometry at a cathodic potential of −1V was performed on the sample in different concentrations (10 mM-150 mM) of NaCl solutions prepared in TRIS buffer solvent. UV–VIS-NIR transmittance in NaCl solutions was measured for the sample before and after chronoamperometry, and the corresponding transmittance changes (ΔT) were recorded. Due to the formation of tungsten bronze, the transmittance of the sample decreases during chronoamperometry. It was observed that the transmittance change increases with the NaCl concentration, and in the NIR wavelength range, the transmittance change observed was maximum. The sensor has a linear response in the range of 10 to 150 mM Na+ and excellent selectivity towards N+ as compared to interfering ions K+ and Ca2+. Its straightforward design, higher response, and selectivity make sodium detection in food sectors and health monitoring possible.

Impact of double headed geminis on leucine and ninhydrin reaction in buffer solvent

Herein, the rates of the study on title reaction were determined in double headed micellar medium varying various constituents by applying UV–vis single beam spectroscopy. The rate constant, kψ, is more in geminis compared to CTAB and follows the first- and fractional order of paths in Leu and ninhydrin (nin), respectively. The impact of double headed geminis on the reaction of Leu and nin study was elucidated in a buffer system. An excellent development in rate led by gemini surfactants is noted and discussed in the text. This observation is interpreted successfully by employing a pseudo-phase model of micellar activity. To acquire the data of cmc, conductivities of surfactant and their system with added reactants were measured on a Systronics conductivity meter at 303 K and 343 K. In our present case, the evaluated cmc values are in excellent matching with the data observed, previously. Based on our current observations and cognizance, an appropriate reaction mechanism is provided.

Green micellar spectrofluorimetric determination of α-mangostin found in herbal products as antioxidant and other biological activities beneficial to human health.

Pharmaceutical product quality control (QC) needs quick, sensitive and economical procedures to deliver high throughput at low cost, which is the key factor considered by such economic facilities. To lessen the risky effects of research laboratories, researchers must take into account the ecological impacts. α-Mangostin (MAG) exhibit anti-inflammatory, antioxidant, anticancer, anti-allergic, antibacterial, antifungal, antiviral and antimalarial activities. Based on the spectrofluorimetric approach, a novel straightforward, sensitive and environmentally friendly method for MAG determination was developed and validated. Many variables were investigated to improve MAG native fluorescence, including solvent type, buffers, pH and additional surfactants. The best MAG fluorescence sensitivity was found in Britton-Robinson buffer (pH4) at 450 nm after irradiation at 350 nm in the concentration range of 5-50 ng ml-1 . The technique was successfully used to determine the presence of MAG in both its approved dose forms and in samples of spiked human plasma, as per FDA standards for validation. According to their evaluation on two recent greenness criteria (GAPI [Green Analytical Procedure Index] and AGREE [Analytical GREEnness]), the suggested approach has been shown to be environmentally beneficial because it normally uses biodegradable chemicals in solvent-free aqueous phases.

Iodination of Eugenol Using Chloramine T as Oxidator

The activity of Eugenol in diagnosing and treating cancers has been investigated. This study aims to synthesise a Eugenol derivative by reacting it with iodide in buffer solvents at pH 5.8, 7 and 8 with chloramine T at 40 mg, 50 mg and 60 mg. The derivatives were further purified by liquidliquid extraction with aquabidest (double purified distilled water) as the polar phase and chloroform as the organic phase. The extraction was monitored with Thin Layer Chromatography (TLC) and purified with PTLC. The characterisation was done using UV and IR spectrophotometers. The product's organoleptic properties showed that it is a colourless liquid with a chloroform odour. The optimal conditions for the synthesis are pH 8 with 40 mg of chloramine T. The product showed a UV signal at ????????????????263.1 nm and the FTIR spectrum of C-I at 534.28 cm-1. In addition, the C-O band was observed at 1230.58 cm-1 and 1303.88 cm-1. The aromatic C = C at 1452.4 cm-1, 1500.62 cm-1 and 1527.62 cm-1, while C = C of an aliphatic alkene band at 1597.06 cm-1. The C-H band was observed at 3259.7 3 cm-1, while the free OH gave a signal at 3356.14 cm-1. Substituted Eugenol compounds can be derived with iodide at an optimum pH of 8 and chloramine T at 40 mg.

Optimization of Tacrolimus Loaded Reconstituted Nanoparticles by QbD Method

The aim of the present study is to implement QbD approach for development and optimization of Tacrolimus Loaded Reconstituted Nanoparticles. Tacrolimus-loaded nanoparticles were prepared by using Kollisolve PEG 300, Kolliphor ELP, Citrate buffer solution and Tween 80. The aqueous medium was added drop by drop into the organic phase at continuous stirring on a magnetic stirrer for half an hour. The solution then homogenized at high pressure that reduced particle size. Drying was done by using Low Endotoxin Lactose Monohydrate as a carrier. The final reconstituted powder stored in a closed container and assessed for zeta potential, drug loading, FT-IR Studies, Particle Size Analysis, SEM, X-Ray Diffraction, DSC etc. Optimization was performed by using Design Expert 8 software, 3 Level Factorial design was selected from Response Surface Design. The drug was found to be 98.65% w/w by assay. The particle size was found to be in the range of 263nm - 500nm. Tacrolimus powder shows O-H stretching vibration at 3374.91cm−1, C = O stretching vibrations at 1733.38 cm−1, and C = C stretching vibration at 1631.55 cm−1, C–O (ester) stretching vibration at 1248.11 cm−1. Tacrolimus nanoparticles were optimized by QbD method, Methanol: Phosphate Buffer (80:20) solvent phase was used having pH 6. The maximum wavelength of Tacrolimus was found to be 293nm. The desirability value of that optimized method was found to be 1. Tacrolimus Loaded Reconstituted Nanoparticles leads to enhanced solubility and we can conclude that an increase in pH was responsible for increment in absorbance and thus showed the direct relationship between them.

Influence of twin-headed gemini micellar system on the study of methionine amino acid with ninhydrin in buffer solution.

The influence of double-headed gemini was examined in the present study by studying the amino acid methionine mixed with ninhydrin in CH3COOH-CH3COONa buffer solvent. The absorbance was monitored at fixed time intervals with UV-vis spectroscopy. An impact typical of surfactants was observed on the ninhydrin-methionine reaction and explained by a pseudo-phase model of micelles. The effect of different temperatures (343 to 363 K) was also determined. Based on data showing the impact of temperature on kψ , several relevant thermodynamic quantities, ΔH #, ΔS #, and E a, were calculated using linear least-squares regression. In addition, the influence of the other reaction ingredients on the reaction, that is, pH and the concentration of ninhydrin and methionine, was studied. The CMC (critical micelle concentration) of pure geminis and the surfactant system with methionine and ninhydrin was evaluated at two temperatures, i.e. at 303 K and 353 K by conductivity measurements. The CMC values of pure gemini surfactants evaluated in the existing case at 303 K are concordant with the results stated before. Moreover, other parameters, including rates and binding constants, were calculated.

Zirconium-based MOF nanocrystals confined on amphoteric halloysite nanotubes for promoting the catalytic hydrolysis of an organophosphorus nerve agent simulant.

Exploiting efficient and practical catalysts for hydrolyzing organophosphorus nerve agents is significant and highly desirable. Herein, a new class of self-detoxifying composites, namely, halloysite nanotubes@NU-912 (HNTs@NU-912), HNTs@NU-912-I and HNTs@UiO-66-NH2, is constructed by in situ synthesis of hexanuclear zirconium cluster-based metal-organic frameworks (Zr-MOFs) NU-912, NU-912-I and UiO-66-NH2, respectively, with HNTs, which are natural nanotubular materials consisting of Si-O-Si tetrahedral sheets on the outer surface and Al-OH octahedral sheets on the inner surface. The results show that crystalline Zr-MOFs uniformly cover the outer surface of HNTs and the particle size of Zr-MOFs is greatly reduced to less than 50 nm. Furthermore, HNTs@NU-912, HNTs@NU-912-I and HNTs@UiO-66-NH2 display much higher catalytic efficiency for the hydrolysis of dimethyl-4-nitrophenyl phosphate (DMNP) than the corresponding Zr-MOFs both in an aqueous N-ethylmorpholine (NEM) buffer solution and under ambient conditions. Specifically, HNTs@NU-912-I shows a turnover frequency (TOF) of 0.315 s-1 in aqueous buffer solution, placing it among the best Zr-MOF-based heterogeneous catalysts for the hydrolysis of DMNP. The composites show high stability, and more importantly, can replace the buffer solvent and control the pH to a certain degree by virtue of its acidic Si-O-Si sheets and alkaline Al-OH sheets. This work provides a certain reference for the subsequent development of personal protective equipment.

Determination of Saturated Ketoconazole Solubility Using Spectrophotometry Uv-Vis Method

Ketoconazole is a weakly basic drug that has lower solubility at higher pH. Determination of solubility of ketoconazole in the base solution is not easy due to the poor solubility. The simple, low cost, efficient, accurate spectrophotometry methods in UV/VIS region have been developed for the determination of ketoconazole. The wavelengths were selected at 230 nm using solvent buffer phosphate pH 6.8. The Beers’ law was obeyed in the concentration range 5-50 ppm. According to ICH guidelines the parameters such as linearity, accuracy, precision, the limit of detection, and the limit of quantification were studied. The regression equation of calibration curve was found to be y=0.0448x-0.13. All concentrations were linear, with the absorbance having a correlation coefficient 0.9994. The accuracy was found between 93.84-95.95%. The % Relative Standard Deviation (RSD) of Ketoconazole was found to be 0.112-1.237 for intraday and 0.008-0.792 for interday precision. The result of the limit of detection (LOD) for ketoconazole was 0.988 that could be reliably detected and the limit of quantification (LoQ) for ketoconazole was 3.294 ppm. The result of ketoconazole solubility was 21.044±0.759 ppm that indicating ketoconazole was a poorly soluble drug in the intestine. The proposed methods could be applied to the determination solublity ketoconazole in buffer phosphate pH 6.8 with good accuracy, good precise, and simple.

Development of native mass spectrometry with nanoelectrospray ionization coupled to size exclusion chromatography for proteins.

Native mass spectrometry (MS) is an analytical technique used to determine the molecular mass of protein complexes without cross-linking. Size exclusion chromatography (SEC) coupled with native MS using conventional electrospray ionization (ESI) has been reported to allow online buffer exchange. To detect a wide variety of protein complexes without a collapse in the ionization process, it is important to build an online system that enables robust analysis with a low flow rate. We created an online native MS system equipped with nanoESI connected to the SEC component (online SEC/nanoESI system) and optimized several parameters for SEC separation and ionization. The constructed system was used to measure a solution consisting of a protein mixture of various molecular masses (10-300 kDa) to verify characteristics such as the measurable molecular mass range, reproducibility, and online buffer exchange. The optimal flow rates for SEC separation and nanoESI analysis using this system were 200 and 1μL/min, respectively. This system was able to analyze proteins in the ranges of 10-300 and 20-300 kDa for protein samples in ammonium acetate and nonvolatile buffer, respectively. Furthermore, the results of consecutive measurements showed that the relative standard deviations of the retention times and observed masses for each protein were sufficiently small. We created an online SEC/nanoESI system and evaluated its utility for the analysis of various proteins in conventional measurement solvent and nonvolatile buffer. As a result, the structural stability and resolution of the proteins were found to be sufficient when using online buffer exchange. Therefore, this online SEC/nanoESI system would be a useful technique for obtaining mass spectra of various proteins automatically with good resolution, simply by loading samples into an autosampler.