Solvent Mixture Of Acetonitrile Research Articles

Simultaneous determination of picroside I and picroside II in dietary supplements by high performance liquid chromatography with PDA detector

Picroside I and picroside II are two compounds found in the Picrorhiza Kurroa plant, which have anti-cirrhosis, antioxidant, anti-inflammatory, fever, and asthma effects, etc. They are included in the ingredients of many dietary supplement products that help protect the liver and bile, prevent oxidation, etc. Therefore, determining the content of these two active ingredients in dietary supplements is necessary to evaluate product quality. In this study, highperformance liquid chromatography (HPLC-PDA) was used to simultaneously determine picroside I and picroside II in dietary supplements. The analytes in the samples were extracted with methanol for 60 min using a horizontal shaking technique. The extract was then filtered and determined by the HPLC–PDA method with the following conditions: C18 Column (250 mm x 4.6 mm; 5 µm) and a corresponding pre-column (3.9 mm x 5 mm; 5 µm), the mobile phase consists of a solvent mixture of acetonitrile and water according to the gradient program, detection wavelength 265 nm. The method has good specificity, the calibration curve of picroside I and picroside II has a linear coefficient R2 > 0.9999 and the repeatability and recovery meet the AOAC requirements. The method limits of detection (MDL) for these two substances were 4.3 mg/kg and 3.2 mg/kg, respectively. The method was applied to simultaneously determine picroside I and picroside II in 30 different dietary supplement products. The results detected analytes in 3 samples positive with picroside I and picroside II concentrations ranging from 98.8 to 148 mg/kg.

Study on the mechanistic classes of fluorescence quenching of tryptanthrin-malononitrile adduct by aniline

Mechanistic studies of the fluorescence quenching of 2-(2-chloro-12-oxoindolo[2,1-b]quinazolin-6(12H)-ylidene)malononitrile (2CTMA) with aniline, using solvent mixtures of acetonitrile and 1,4-dioxane at room temperature, by steady-state and time-resolved methods is reported here. It was confirmed that, with the use of the sphere of action static quenching model and finite sink approximation model, that the bimolecular quenching reactions are due to the presence of both dynamic and static quenching processes.

First-Principles Modeling of Preferential Solvation in Mixed-Modifier Differential Mobility Spectrometry.

Differential mobility spectrometry (DMS) separates ions based on mobility differences between high and low electric field conditions. To enhance resolution, solvents such as water and acetonitrile are often used to modify the collision environment and take advantage of differing dynamic clustering behavior between analytes that coelute in hard-sphere environments (e.g., N2). When binary solvent mixtures are used to modify the DMS environment, one solvent can have a dominant influence over the other with respect to ion trajectories. For example, for quinoline derivatives, a 9:1 water:acetonitrile solvent mixture exhibited identical behavior to an environment containing only acetonitrile as a modifier. It was hypothesized that this effect arises due to the significantly different binding strengths of the two solvents. Here, we utilize a first-principles model of DMS to study analytes in single and binary solvent mixtures and explore the effects governing the dominance of one solvent over the other. Computed DMS dispersion curves of quinoline derivatives are in excellent agreement with those measured experimentally. For mixed-modifier environments, the predicted cluster populations show a clear preferential solvation of ions with the stronger binding solvent. The influence of ion-solvent binding energies, solvent concentration, and solvent molecule size is discussed in the context of the observed DMS behavior. This work can guide the usage of binary solvent mixtures for improving ion separations in cases where compounds coelute in pure N2 and in single-solvent modifier environments. Moreover, our results indicate that binary solvent mixtures can be used to create a relative scale for solvent binding energies.

Effect of solution acidity on cytochrome c conformations of alternating current electrospray ionization mass spectrometry

AbstractThis paper reports notable observations regarding the ion charge states of thermally stable cytochrome c, generated using an alternating current (AC) electrospray ionization (ESI) device. An AC ESI sprayer entrains low‐mobility ions to accumulate at the meniscus cone tip prior to the ejection of detached aerosols to produce analyte ions. Therefore, as the solvent acidity varies, protein ions entrained in the AC cone tip are found to change conformation less significantly compared with those in the direct current (DC) cone. We acquired the AC ESI mass spectra of cytochrome c at pH range from 2 to 4. Unlike the DC ESI mass spectra showing clear conformation changes due to denaturing, the AC spectra indicated that only partial denaturing occurs even at extremely acidic pH 2. More native cytochrome c in lower charge states therefore remained. Moreover, with a solvent mixture of aqueous buffer and acetonitrile (70:30), partially denatured cytochrome c was still preserved at pH 2 by using AC ESI. Completely denatured proteins are observed at pH 2 by using DC ESI.

Liquid–liquid phase separation and crystallization of aspirin polymorphs from a water–acetonitrile mixed solvent medium through a swift cooling process

Screening of form-I and form-II polymorphs of the pharmaceutical solid aspirin in the vicinity of liquid–liquid phase separation in water–acetonitrile solvent mixtures through a novel swift cooling crystallization process is successfully attained.

Investigation of the Fluorescence Turn-off Mechanism, Genome, Molecular Docking In Silico and In Vitro Studies of 2-Acetyl-3H-benzo[f]chromen-3-one.

The present study harnesses fluorescence quenching between a nonfluorescent aniline and fluorophore 2-acetyl-3H-benzo[f]chromen-3-one [2AHBC] in binary solvent mixtures of acetonitrile and 1,4-dioxane at room temperature and explores the fluorophore as an antimicrobial material. Our findings throw light on the key performance of organic molecules in the medicinal and pharmaceutical fields, which are considered as the most leading drives in therapeutic applications. In view of that, fluorescence quenching data have been interpreted by various quenching models. This demonstrates that the sphere of action holds very well in the present work and also confirms the presence of static quenching reactions. Additionally, the fluorophore was first investigated for druglike activity with the help of in silico tools, and then it was investigated for antimicrobial activity through bioinformatics tools, which has shown promising insights.

Evaporation and Rheology Chart the Processability Map for Centrifugal Force Spinning

We show that poly(ethylene oxide) (PEO) solutions formulated using solvent mixtures of acetonitrile (AcN) and water can be centrifugally spun into fibers. We find that spinnability and fiber morpho...

Insight into molecular interactions and solvation properties of methylammonium perchlorate in acetonitrile-dimethylsulfoxide binary mixtures: Compressibility, viscometric and dissolution thermodynamic studies

Densities (ρ), ultrasonic velocities (u) and viscosities (ƞ) of Methylammonium perchlorate (CH3NH3ClO4) in binary solvent mixtures of Acetonitrile (AN) and Dimethylsulfoxide (DMSO) containing 0.0, 0.20, 0.40, 0.60, 0.80 and 1.0 ​mol fraction of DMSO at various temperatures ranging from 298K–328K at atmospheric pressure, have been measured. From the experimental data important parameters, namely, apparent molal volume (VΦ), isentropic compressibility (Ks), limiting apparent molal isentropic compressibility (Kos,ɸ), A and B-viscosity coefficients from Jones-Dole equation, B/Vɸo values and viscous flow related thermodynamic properties have been derived. Interpretation of the obtained thermodynamic parameters was done with regards to solute-solvent and solute-solute interactions and structure breaking and making potential of the solutes in solution. To evaluate the extent of preferential solvation, Kos,ɸ values and B-coefficients for the electrolytes have been further split up into the contribution of individual ion (Kos,ɸ± and B± values) by reference electrolyte method.

“Doing More with Less”: Ni(II)@ORMOSIL, a Novel Sol-Gel Pre-Catalyst for the Reduction of Nitrobenzene

Reduction of nitrobenzene with NaBH4 using zero-valent iron nanoparticles (ZVI-NPs) and NiCl2∙6H2O incorporated in organically modified hybrid silica matrices as ZVI@ORMOSIL and Ni(II)@ORMOSIL catalysts is proposed as a remediation strategy. Ni(II)@ORMOSIL is prepared by ion-exchanging H+ of the ORMOSIL matrix with NiII. Ni(II)@ORMOSIL is a pre-catalyst that undergoes reduction by NaBH4 by an in-situ reaction and promotes nitrobenzene reduction by the unconsumed NaBH4, leading to sparing use of the catalyst. Ni(II)@ORMOSIL undergoes color change from green to black in this process, returning to a green hue after washing and drying. Nitrobenzene reductions were examined in aqueous acetonitrile solvent mixtures, and the reduction cascade produced the reaction end-products with catalytic implications. Plausible mechanisms of ZVI@ORMOSIL and Ni(II)@ORMOSIL catalyzed reductions of nitrobenzene are discussed. This work is the first to report M(II)@ORMOSIL pre-catalysts for in-situ reduction of nitrobenzene, and expands the scope of the ORMOSIL series of catalysts for the reduction of polluting compounds. This approach enables the development of catalysts that use very low concentrations of transition metal cations.

Effect of Organic Solvents on the Structure and Activity of a Minimal Lipase.

Lipases are ubiquitously used in chemo-enzymatic synthesis and industrial applications. Nevertheless, the modulation of the activity of lipases by organic solvents still is not fully understood at the molecular level. We systematically investigated the activity and structure of lipase A from Bacillus subtilis in binary water-organic solvent mixtures of dimethyl sulfoxide (DMSO), acetonitrile (ACN), and isopropyl alcohol (IPA) using activity assays, fluorescence spectroscopy, molecular dynamics (MD) simulations, and FRET/MD analysis. The enzymatic activity strongly depended on the type and amount of organic solvent in the reaction media. Whereas IPA and ACN reduced the activity of the enzyme, small concentrations of DMSO led to lipase activation via an uncompetitive mechanism. DMSO molecules did not directly interfere with the binding of the substrate in the active site, contrary to what is known for other solvents and enzymes. We propose that the His156-Asp133 interaction, the binding of organic molecules to the active site, and the water accessibility of the substrate are key factors modulating the catalytic activity. Furthermore, we rationalized the role of solvent descriptors on the regulation of enzymatic activity in mixtures with low concentrations of the organic molecule, with prospective implications for the optimization of biocatalytic processes via solvent tuning.

Intermolecular Interactions at the Silica-Liquid Interface Modulate the Fermi Resonance Coupling in Surface Methanol.

The buried solid/liquid interface between hydrophilic fused silica and binary solvent mixtures of acetonitrile (MeCN) and methanol (MeOH) was studied with vibrational sum-frequency generation (vSFG) spectroscopy. Our data showed that at high relative concentrations of methanol, the Fermi resonance peak in the vSFG spectrum is greatly suppressed, and it progressively gains intensity as methanol is diluted with perdeuterated acetonitrile. This phenomenon is quantified by the Fermi resonance coupling coefficient, W, extracted using a two-level model, as well as the experimental intensity ratio, R, of the methyl Fermi resonance band to that of the symmetric stretch. At a 1.0 MeOH mole fraction, W and R values were 10 ± 10 cm-1 and 0.01 ± 0.02, respectively, whereas at a 0.1 mole fraction, W and R increased to 46 ± 4 cm-1 and 0.43 ± 0.16, respectively. This indicates that solvation with acetonitrile effectively tunes the Fermi coupling of methanol vibrations at the silica/liquid interface.

Quality by Design Approach to Develop Stability Indicating Method to Quantify Related Substances and Degradation Products of Sacubitril by High Performance Liquid Chromatography.

Sacubitril (SBT) is a neprilysin inhibitor, approved by food and drug administration (FDA) in 2015, under the FDA's priority review process. In this work, we report the validated stability indicating method of SBT by employing quality by design (QbD) principles related to analytical method development, capable in separation of 11 impurities. Chromatographic separation was performed on an ascentis phenyl hexyl column using 10mM KH2PO4 as a mobile phase-A and the pH adjusted to 2.1. Methanol: acetonitrile (70:30v/v) solvent mixture was employed as the mobile phase-B in a gradient mode of elution at a flow rate 0.8mL/min at 30°C. The column effluents were monitored by a photo diode array detector set at a wavelength of maximum absorption 254nm noted for all the impurities and furthermore for SBT. This method was remarked to be accurate in the range from 92 to 116%, precise with relative standard deviation 0.9% for SBT (0.8mg/mL) and 1.0 to 2.1% for its related impurities (0.0005mg/mL) also linear with correlation coefficient r≥0.9989. The limits of quantification for all impurities were 0.05% with respect to sample concentration 0.8mg/mL. The developed method revealed a good method operable design range for the experimental chromatographic conditions. Forced degradation of SBT carried under acidic, basic and oxidative stressed conditions manifested that the method is stability indicating.

Novel ruthenium(ii) and (iii) carborane complexes with diphosphine ligands and their application in radical polymerization

Ruthenium(ii) and (iii) carborane complexes containing XantPhos as a ligand were synthesized for the first time. It was shown that the reaction of the known complex exo-5,6,10-[Cl(Ph3P)2Ru]-5,6,10-(µ-H)3-10-H-nido-7,8-C2B9H8 with a 10% molar excess of XantPhos in benzene at 80 °C leads to a new closo-ruthenacarborane 3-Cl-3,3-[x2-XantPhos]-closo-3,1,2-RuC2B9H11, which can be easily converted to the corresponding acetonitrile complex 3-CH3CN-3,3-[x2-XantPhos]-closo-3,1,2-RuC2B9H11 by the reaction with isopropylamine in a dichloromethane—acetonitrile solvent mixture at 40 °C. These compounds, as well as previously synthesized ruthenium(ii) carborane complexes, were used as a basis for new catalyst systems allowing to conduct controlled radical polymerization at high rates even at low catalyst loading. The specific features of methyl methacrylate polymerization under the action of the indicated catalyst systems were considered and the mechanism of the process was investigated.

Simultaneous estimation of amlodipine besylate, Rosuvastatin calcium and Fimasartan potassium trihydrate combination used in the treatment of hypertension using LC method

The proposed sensitive, precise, and accurate reverse phase-liquid chromatography (RP-LC) method is used for simultaneous estimation Amlodipine besylate, Rosuvastatin calcium and Fimasartan potassium trihydrate in bulk and synthetic mixture which is under phase 3 trial. An accurate and cost effective isocratic approach is employed by using Phenomenex C-18 column (250 mm × 4.6 mm, 5 μm). A method was developed and validated by focusing on ICH Q2 (R1) guideline parameters, efficient separation of all three drugs were obtained by optimised solvent mixture of acetonitrile and 0.02 M potassium dihydrogen phosphate buffer (49:51, v/v) pH 3.0 adjusted with 1% O—phosphoric acid used as mobile phase, flow rate was maintained 1 ml/min and analysis was carried out by using PDA detector at common wavelength 242 nm. The linearity ranges were found to be 1–7 μg/mL for Amlodipine besylate with correlation coefficient (r2) 0.9966, 2–12 μg/mL for Rosuvastatin calcium with correlation coefficient (r2) 0.9998 and 6–36 μg/mL for Fimasartan potassium trihydrate with correlation coefficient (r2) 0.9990, respectively. The proposed LC method has potential qualitative as well as quantitative applications for simultaneous estimation of Amlodipine besylate, Rosuvastatin calcium and Fimasartan potassium trihydrate in bulk and synthetic mixture.

Fluorescence spectroscopic studies on preferential solvation and bimolecular quenching reactions of Quinolin-8-ol in binary solvent mixtures

On account of the importance towards solvent mixtures in practical chemistry, binary solvent mixtures of acetonitrile (AN) and 1, 4-dioxane (DX) are used to study fluorescence behavior of this organic compound namely Quinolin-8-ol (QO). At the outset, preferential solvation is examined in AN-DX for this QO, in order to understand specific and nonspecific interactions. Further Suppan’s dielectric enrichment model is implemented to identify the non-ideality and dielectric enrichment in AN-DX for preferential solvation. Bimolecular quenching reaction studies of Quinolin-8-ol have been carried out in mixtures of AN-DX to study the effect of dielectric constants and viscosity at room temperature. The quenching process is studied in all solvent mixtures by Steady state and Transient state method. Quenching is characterized by Stern-Volmer (S-V) plots having downward curvature. Interestingly, for moderate quenching concentration, downward curvature has been observed for the title molecule. The inter and intra molecular hydrogen bonding has profound role in the formation of different conformers in QO. Further, modified S-V equation is applied to analyze the fluorescence quenching reactions of QO molecule.

Simultaneous and Trace Level Determination of Six Potential Impurities by UPLC-ESI-MS/MS in Antiarrhythmic Drug: Dronedarone Hydrochloride

Development and validation of six potential impurities by ultra performance liquid chromatography electro spray ionization tandem mass (UPLC-ESI-MS/MS) method for dronedarone hydrochloride drug was accomplished coherent with ICH guidelines. Successful chromatographic separation of dronedarone with its six impurities was attained by using gradient elution mode on RP-UPLC column using three pump mode system of 0.1 % formic acid in water as mobile phase A, methanol as the mobile phase B and solvent mixture of methanol, acetonitrile and water in the ratio of 65:30:5 v/v/v as the mobile phase C. Chromatographic conditions were set as 0.3 mL min-1 flow rate at the column temperature of 45 °C with the injection volume 2 μL. Briefly, the method enabled quantitation of six impurities with high accuracy (recovery > 90 %) and precision (% RSD < 5.0),within the ranges of 0.18-2.82 μg g-1. The regression (r) for each impurity over a range was > 0.99. The detection limit and quantitation limit of impurities were set at 0.09 and 0.18 μg g-1, respectively. The performed validation tests proved the suitability of the method for its intended purposes.

Effect of preferential solvation and bimolecular quenching reactions on 3OCE in acetonitrile and 1,4-dioxane binary mixtures by optical absorption and fluorescence studies.

Fluorescence quenching and preferential solvation of a coumarin derivative, namely 3-[2-oxo-2-(2-oxo-2H-chromen-3-yl)-ethylidene]-1,3-dihydro-indol-2-one (3OCE), with aniline used as a quencher in solvent mixtures of acetonitrile (AN) and 1,4-dioxane (DX) was carried out at steady state. Suppan's theory of dielectric enrichment was used to understand the nonideality and dielectric enrichment in AN-DX solvent mixtures. The effect of viscosity and dielectric constant variation at room temperature were analyzed. Quenching was characterized using Stern-Volmer plots with an upward curvature. It was found that 3OCE underwent combined static and dynamic quenching that was evident from the quenching rate parameters.

Bioethanol production from agarophyte red seaweed, Gelidium elegans, using a novel sample preparation method for analysing bioethanol content by gas chromatography.

In this study, Gelidium elegans is investigated for ethanol production. A combination of factors including different temperatures, acid concentration and incubation time was evaluated to determine the suitable saccharification conditions. The combination of 2.5% (w/v) H2SO4 at 120°C for 40min was selected for hydrolysis of the seaweed biomass, followed by purification, and fermentation to yield ethanol. The galactose and glucose were dominant reducing sugars in the G. elegans hydrolysate and under optimum condition of dilute acid hydrolysis, 39.42% of reducing sugars was produced and fermentation resulted in ethanol concentration of 13.27 ± 0.47g/L. A modified method was evaluated for sample preparation for gas chromatography (GC) analysis of the ethanol content. A solvent mixture of acetonitrile and iso-butanol precipitated dissolved organic residues and reduced water content in GC samples at least by 90%. Results showed that this method could be successfully used for bioethanol production from seaweed.

Long-Lived Photoexcited State of a Mn(IV)-Oxo Complex Binding Scandium Ions That is Capable of Hydroxylating Benzene.

Photoexcitation of a MnIV-oxo complex binding scandium ions ([(Bn-TPEN)MnIV(O)]2+-(Sc(OTf)3)2) in a solvent mixture of trifluoroethanol and acetonitrile (v/v = 1:1) resulted in formation of the long-lived photoexcited state, which can hydroxylate benzene to phenol. The photohydroxylation of benzene by [(Bn-TPEN)MnIV(O)]2+-(Sc(OTf)3)2 was made possible by electron transfer from benzene to the long-lived 2 E excited state of [(Bn-TPEN)MnIV(O)]2+-(Sc(OTf)3)2 to produce a benzene radical cation, which reacted with water as revealed by laser-induced transient absorption measurements.

Preparation and characterization of electrically semi-conductive polyfuran-coated poly(ethylene terephthalate) fibers

One of the most important textile materials, poly(ethylene terephthalate) (PET) fiber, was coated with a semi-conductive polyfuran (PFu) by in situ oxidative polymerization using FeCl3 oxidant in solvent mixture of acetonitrile–chloroform. The effects of polymerization conditions such as volume ratios of acetonitrile/chloroform, monomer concentration, and oxidant/monomer mol ratio were investigated on PFu content (%) of the composites. It was observed that pretreatment of PET in dichloromethane increased PFu content and its coating continuity before polymerization. The highest PFu content (12.0%) was obtained using FeCl3/furan mol ratios of 3.5 in acetonitrile/chloroform mixture (5/1). The density values of the composites with different PFu contents were measured. Composite fibers were also subjected to doping processes with HCl and I2 vapors, separately, and it was observed that the surface resistivity of PFu/PET (1012 Ω/cm2) reached to 53 Ω/cm2 after doping with I2. The structural, thermal, and morphological characterization was performed with FTIR, XRD, TGA, and SEM, respectively.