Acetonitrile Solvent Research Articles

Preparation of a novel poly-(di-ionic liquid)/BDD-modified electrode for the detection of tetrachloro-p-benzoquinone

During the COVID-19 pandemic, the release of toxic disinfection by-products (DBPs) has increased due to the intensive, large-scale use of disinfectants. Halogenated benzoquinones (HBQs) are among the most toxic DBPs, but there is no rapid, convenient, and economical detection method. In this study, a novel PDIL/BDD-modified electrode was prepared in a mixed solvent of dimethyl sulfoxide (DMSO) and acetonitrile (ACN) by electrochemical polymerization with a di-ionic ionic liquid containing alkenyl groups as the monomer. The electrochemical behavior of tetra-chloro-p-benzoquinone (TCBQ) on the modified electrode was studied. By studying the cyclic voltammetry behavior of TCBQ on the PDIL/BDD electrode, it was concluded that the electrode reactions of TCBQ included the reduction of TCBQ to TCBQH2 (C1) and the reduction of bis-quinhydrone imidazole π-π type charge transfer complex to TCBQH2 (C2). By studying the SWV responses of TCBQ in the concentration range of 1–100 ng/L on the PDIL/BDD electrode, it was found that the reduction peak current (Ipa) had a linear relationship with the concentration. The electrochemical SWV technique was used to detect the concentration of trace TCBQ in water and is expected to be used for the detection of other HBQs in drinking water and swimming pool water.

Accelerating SN2 nucleophilic fluorination of primary alkyl bromide using an 18-crown-6 and fluorinated bulky alcohol phase transfer system

A new phase transfer system for nucleophilic fluorination of alkyl halides with potassium fluoride, based on the combination of 18-crown-6 and the bulky fluorinated alcohol 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, was found to be very effective. A primary alkyl bromide was fluorinated in 24 h of reaction time with a mild temperature of 82 °C using acetonitrile solvent, obtaining 80% yield and only a trace of elimination product. The rational choice of this alcohol was based on a free energy profile of a reaction model including the solubilization of the KF salt and on the theoretical calculations of the stability of the KF(18-crown-6)(alcohol) complexes. The fluorinated bulky alcohol leads to a substantial increase in the concentration of KF complexed with 18-crown-6, which compensates for the decreased reactivity of the solubilized complex. The present study shows the importance of the modulation of the hydrogen bonding strength to obtain the rate acceleration effect.

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.

RP-HPLC Method Development and Validation for Simultaneous Estimation of Rutin and Quercetin in Morus alba L. leaf extract

Mulberry, which pertains to the Moraceae family and the genus Morus,has been used in medicine for ages because of its chemical composition and pharmacological action. The plant is recognized in traditional Chinese medicine for its antiphlogistic, diuretic, expectorant, and antidiabetic characteristics. The mulberry leaf is high in flavonoids, which have a variety of biological functions, including antioxidant potential. Quercetin, isoquercetin, rutin, isoquercitrin, quercitrin, luteolin, chlorogenic acid, and other flavonoids can be found in their leaves. The major constituents of total flavones in mulberry leaf extract are rutin and quercetin. The goal of the RP-HPLC approach was to design and validate a method for identifying these elements. HPLC (Shimadzu Technologies LC series) with UV-visible detector at 259nm and C18 column (250mm 4.6mm, 5µm particle size) was used to achieve chromatographic separation (Phenomenex Luna). Solvents (acetonitrile and 0.1 percent v/v solution of glacial acetic acid) were used in the isocratic elution mode. The run time was 10 minutes. The column temperature was 37 degrees Celsius with sample insertion volume 20µl and the flow velocity was 1ml/min. For quercetin and rutin, the devised method produced strong linearity, high accuracy, high precision, high repeatability, high robustness, and high ruggedness. For quercetin and rutin, the LOD and LOQs values were determined to be within acceptable levels.

Covalent Grafting of Eosin Y to the Giant Keplerate {Mo132} through an Organosilicon Linker in Homogeneous Regime

The template effect of giant polyoxometalates (POM) shows promising results towards the supramolecular design of hybrid materials suitable for photocatalytic reactions. Here, we demonstrate a novel synthetic approach for covalently grafting the xanthene dye eosin Y (EY) to the nanoscale Keplerate POM {Mo132} via an organosilicon linker (3-aminopropyltrimethoxysilane, APTMS) in a homogeneous regime. Using a phase transfer agent, tetrabutylammonium bromide, we solubilize the Keplerate POM modified with six {Si(CH2)3NH2} groups, {Mo132}@Si6, in a series of organic solvents—acetonitrile, acetone, tetrahydrofuran, and dichloromethane—to perform post-functionalization by using an NHS-ester of EY. Both IR and Raman spectroscopy affirm the preservation of the POM’s structure and showcase an amide bond formation between POM and EY in the obtained conjugate {Mo132}@Si6@EY@TBA. Grafting’s success is observed through significant downfield shifting of EY’s aromatic protons’ signals on the 1H NMR spectrum as compared to the spectra of EY and EY-NHS. The current synthetic approach enables us to exercise precise control of the stoichiometry in the POM-dye conjugates—1:1 for the POM-EY system—as confirmed by elemental analysis. Comprehensive photophysical analysis of {Mo132}@Si6@EY@TBA by means of UV-Vis and steady-state and time-resolved fluorescence measurements points to an existing strong interaction between molecular orbitals of EY and {Mo132}, leading to a photoinduced electron transfer, partial fluorescence quenching, and elongation of the excited state’s lifetime. These findings demonstrate that using APTMS as an organosilicon linker in tandem with the Keplerate POM as a nanoscale template can be readily applied as a routine synthetic procedure for grafting various organic dyes or other organic molecules bearing a carboxylic group in their structure to the giant POM surface in a variety of aprotic organic solvents.

Imidazolium-functionalized liquid ferrocene derivative positive material enables robust cycling stability of non-aqueous redox flow battery

The non-aqueous redox flow battery (NARFB) is a very promising technology for the grid-scale energy storage; however, its wide application is seriously limited by the cycling stability. Here, we designed a ferrocene derivative by imidazole-functionalization and grafting an oligoether chain, 1-ferrocenylmethyl-3-(2-(2-(2-methoxyethoxy)ethoxy)ethyl) imidazolium-bis(trifluoromethylsulfonyl)imide (FcMITEGTFSI). The imidazolium cationic group induces a positive shift in the redox potential of the ferrocene core whilst ensuring the stability of the active species; the flexible oligoether side chain renders the molecule a liquid at room temperature (25 °C) and miscible with acetonitrile solvent. The flow battery shows robust cycling stability, with an overall discharge capacity retention of ≈95.5% after 200 cycles, corresponding to a capacity retention of ≈99.98% per cycle at 25 mA cm−2 with 0.1 M electrolyte.

Determination of L-Glutamine Solubility in 12 Pure Solvent Systems from 283.15 to 323.15 K

The mole fraction solubility of L-glutamine in 12 pure solvents (methanol, n-propanol, sec-butanol, 2-butanone, ethanol, acetonitrile, n-butanol, ethyl acetate, n-pentanol, water, n-hexane, and isobutanol) was determined by the static gravimetric method at a temperature range of 283.15–323.15 K under a pressure of 98.8 kPa. The equilibrium solid phase of L-glutamine in the solvent systems was characterized by powder X-ray diffraction analysis. The solubility in the 12 monosolvents was found to increase with absolute temperature. The maximum and minimum values were in water and ethyl acetate, respectively. The empirical solvent polarity parameters (ET(30)), cohesive energy density, and hydrogen bond donor/acceptor (HBD/HBA) tendencies were employed to analyze the solubility behavior and solvent effects. The solubility data were fitted using the modified Apelblat model and the Yaws model, at the same time, the model parameters and data deviation values were calculated. These two solubility models were evaluated using the Akaike Information Criteria and Akaike weights. The results showed that the modified Apelblat model had better correlation results. The solubility data could be used in the preparation and optimization of L-glutamine crystallization processes.

Observations into the reactivity, docking, DFT, and MD simulations of fludarabine and clofarabine in various solvents

Fludarabine (FA) and Clofarabine (FCA) two novel drugs are studied experimentally and theoretically. The solvation free energies of FA and FCA molecules have been calculated using water, ethanol, Dimethylsulfoxide, and acetonitrile solvent. Various protic and aprotic solvents are used to evaluate the absorption properties. Fourier Transform Infrared, FT-Raman and Nuclear magnetic resonance spectroscopy are used to characterize structural features of fludarabine and clofarabine. On the studied molecules, Density Functional theory (DFT) was performed to find various chemical and electronic characteristics. Molecular docking analysis employed optimized geometrical structures. Dual Fukui functions, dual local softness, and philicity were studied and discussed in extensive detail. The crystal structures of leukaemia virus protease, 2B7F, 4G0U, and 6ZTD were used to test fludarabine and clofarabine. Out of the three PDBs, 4G0U gives high binding affinity with FCA/FA during docking analysis and hence MD simulations are performed for further investigation to find the interactions and stability.

HPLC-UV Analysis of Chrysophanol in Senna occidentalis Extract Obtained by Using the RSM-Optimized Ultrasonic Extraction Process

In this experiment, chrysophanol analysis in Senna occidentalis (aerial parts) extract obtained by optimizing ultrasound-assisted extraction (UAE) variables (temperature, time, and liquid-to-solid ratio) using response surface methodology (RSM) was performed by employing the HPLC-UV method. For UAE process optimization, a highly significant quadratic model (p < 0.001) was projected to attain maximum chrysophanol yield. The extraction temperature, time, and liquid-to-solid ratio for the best UAE method were determined to be 49.3 °C, 57.7 min, and 18.7 mL/g, respectively. The optimized extract was subjected to a chrysophanol analysis utilizing HPLC-UV (fitted with a Pinnacle C18 column), and a gradient mobile phase composed of 0.5% formic acid (solvent A), acetonitrile (solvent B), methanol (solvent C), at a flow rate of 1.0 mL/min, and an optimum wavelength of 279 nm, respectively. It furnished a compact and intense peak of chrysophanol at Rt = 23.809 min. The experimental value (20.47 mg/g) of chrysophanol obtained was close to the predicted value (19.32 mg/g), indicating that they agreed under the optimized extraction condition. UAE also displayed remarkable improvement in chrysophanol extraction compared with the conventional solvent extraction (CSE) method. Hence, our improved ultrasonic extraction process showed a potential use for effective chrysophanol extraction from commercial herbal supplements comprising the Senna species.

Evaluation of treatment methods for spiking deoxynivalenol (DON) in single corn kernels

Current research on deoxynivalenol (DON), a trichothecene secondary metabolite produced by the Fusarium species in corn grains, relies on the time-consuming field inoculation of Fusarium species with unpredictable and low recovery rates of DON in grains. The objective of this study was to evaluate three methods: soaking whole grains, soaking cracked grains, and injection in three solvents (distilled water, methanol, and acetonitrile) at three toxin concentration levels (1, 5, and 10 µg/g) for facilitating DON absorption in corn grains. The effectiveness of each treatment method and the performance of each solvent in aiding DON absorption were analysed and compared with the recovery rates of DON in the treated corn grains. The treatment methods, solvent, and DON concentration in solvent had significant effect on the recovery rate of DON in treated kernels. Injecting whole grains showed the highest recovery rates of DON (60%–108%) followed by soaking cracked grains (10%–87%) and whole grain (10%–72%) treatment methods. Distilled water showed the highest recovery rates in both soaking (53%–87%) and injection (74%–105%) treatment methods followed by methanol (18%–68% for soaking; 66%–103% for injection) and acetonitrile (10%–36% for soaking; 61%–108% for injection). Water dispersed the arrangement of starch granules but caused no changes in their surface morphology. Methanol and acetonitrile showed disruptive effects on the surface morphology of starch granules.

Controlling the electrocatalytic activities of conducting polymer thin films toward suitability as cost-effective counter electrodes of dye-sensitized solar cells

Role dopant anions and solvents in electropolymerized conducting polymers (CPs) on controlling the morphology of thin films and electrocatalytic activities to judge their suitability as low-cost counter electrodes (CE) of dye-sensitized solar cells ( DSSCs) was systematically investigated. Amongst various CPs such as polyaniline (PANI), polypyrrole (PPy), and PEDOT with sodium dodecyl sulfate (SDS) as a dopant, PEDOT was found to exhibit the best photovoltaic performance with a photoconversion efficiency (PCE) of 6.99 %. This was attributed to the best electrocatalytic activity due to the smallest ΔEp, most minor R1, and nano-morphology-assisted high surface area, as confirmed by CV, EIS, and FE-SEM investigations. Using PEDOT as CP, the nature of dopants such as SDS, TFSI, and ClO4 has also been found to control the electrocatalytic activities and the morphology of the fabricated thin films affecting overall photovoltaic performance DSSCs. Amongst the various CP-based CE fabricated using different dopants and solvents, PEDOT:TFSI thin films prepared in acetonitrile solvent and used as CE exhibited not only the best electrocatalytic activity as CE but also demonstrated the best photovoltaic performance with PCE of 7.0 %, which almost similar to that of DSSC utilizing Pt as CE with PCE of 7.1 %. Therefore, it was concluded that the nature of CP and dopant ions were vital factors in governing the electrocatalytic activities of the thin films to ensure their suitability as CE for optimal functioning and controlling the DSSC performance.

Development of the spectrophotometric method for the determination of rosuvastatin in tablets by using bromophenol blue

The aim of the work was to develop a spectrophotometric method for the determination of rosuvastatin in tablets based on the reaction with BPB in compliance with the principles of «green» chemistry.
 Material and methods. Analytical equipment: two-beam UV-visible spectrophotometer Shimadzu model -UV 1800 (Japan), software UV-Probe 2.62, electronic laboratory balance RAD WAG AS 200/C. The following APIs, dosage forms, reagents and solvents were used in work: pharmacopoeial standard sample (CRS) of rosuvastatin calcium (Sigma-Aldrich, (≥ 98 %, HPLC)), BCG (Sigma-Aldrich, (≥ 98 %, HPLC)), "Rosuvastatin" tablets 10 mg, 15 mg, 20 mg, methanol (Honeywell, (≥ 99.9 %, GC)), ethanol (Honeywell, (≥ 99.9 %, GC)), chloroform (Honeywell, (≥ 99.9 %, GC)), acetonitrile (Honeywell, (≥ 99.9 %, GC)), and ethyl acetate (Honeywell, (≥ 99.7 %, GC)).
 Results and discussion. A spectrophotometric method for determining rosuvastatin by reaction with BPB in an acetonitrile solution using the absorption maximum at a wavelength of 595 nm has been developed. Stoichiometric ratios of reactive components were established, which were 1:1. The developed method for the quantitative determination of rosuvastatin was validated following the requirements of the SPhU. The analytical method was linear in the 7.99-23.97 μmol/L concentration range. The LOD and LOQ values were calculated to be 0.77 µmol/L and 2.36 µmol/L. According to the «greenness» pictogram of the analytical method using the AGREE method, the score was 0.77, indicating that the proposed spectrophotometric method for determining rosuvastatin was developed in compliance with the principles of «green» chemistry.
 Conclusions. An eco-friendly spectrophotometric method has been developed to quantitatively determine rosuvastatin in tablets based on the reaction with BPB. The appropriate sulfophthalein dye (BPB) and its concentration (4.00 x 10-4), the optimal eco-friendly solvent (acetonitrile), and the appropriate wavelength (595 nm) were chosen, and the sensitivity of the reaction was calculated. The analytical method was validated, and its possibility for use in the pharmaceutical analysis was shown

Solvent Polarity and Framework Hydrophobicity of Hf-BEA Zeolites Influence Aldol Addition Rates in Organic Media

Solvent identity and pore polarity are known to influence Lewis acidic catalysis in zeolite pores for a variety of liquid-phase chemistries. We investigated how these parameters alter the rates of self-aldol addition of ethyl pyruvate (EP), a model biomass-derived compound, over hydrophobic and hydrophilic Hf-BEA zeolites in both toluene and acetonitrile solvents. Aldol addition rates are of first order across the entire EP activity range (0.02–0.4) for all four systems, consistent with the nucleophilic attack by the enolate as the rate-determining step and a single adsorbed EP as the most abundant reactive intermediate. Apparent first-order rate constants span 2 orders of magnitude across the four systems; at 363 K, the highest rates were observed over hydrophobic Hf-BEA-F in toluene (kapp = 0.36 (mmol) (mmol closed Hf)−1 (s)−1), while the lowest rates were observed in hydrophilic Hf-BEA-OH in an acetonitrile solvent (kapp = 0.0026 (mmol) (mmol closed Hf)−1 (s)−1). Apparent reaction enthalpies and entropies for each system, estimated using non-ideal transition-state theory, revealed that despite the substantial rate constant variation across the four systems, apparent enthalpies for Hf-BEA-F in both solvents and Hf-BEA-OH in acetonitrile were within the error of each other (∼70 kJ mol–1). Reactions performed using Hf-BEA-OH with toluene featured a higher apparent enthalpic barrier of 83.8 kJ mol–1. The differences between the systems are attributed to hydrogen-bonding interactions between the EP molecules and polar silanol nests during catalysis in toluene using Hf-BEA-OH, which hinder EP adsorption to the active site in the hydrophilic framework. These hydrogen-bonding interactions are not present when acetonitrile is used as the solvent, as acetonitrile itself binds to and blocks silanol groups. Equilibrium EP absorption measurements indicate that while both toluene and acetonitrile are present in pores during catalysis, neither solvent forms a tight solvation shell around EP in the pores that must be disrupted prior to EP adsorption. These findings show that aldol addition kinetics are not significantly modified by solvent polarity in hydrophobic frameworks beyond site-blocking effects; however, silanol nests in hydrophilic frameworks significantly alter substrate adsorption to the active site.

Synthesis, photophysical, voltammetric, and DFT studies of 4-aminochalones

Aminochalcones, with a D-A-D architecture, were synthesized using Claisen-Schmidt condensation. The compounds were characterized by FTIR, melting point, HRMS, 1H, and 13C NMR spectroscopy and analyzed for UV–visible and fluorescence in different solvents (chloroform, acetonitrile, and methanol). All compounds showed absorption in the range of 330–420 nm and emission in the range of 400–550 nm. Both absorption and emission spectra exhibit bathochromic shifts from non-polar to polar solvents due to intramolecular charge transfer (ICT) interaction. Compounds 17 and 18 displayed mega Stokes shift (Δλ = 116–130 nm) in polar solvents giving these compounds a higher fluorescent character. Furthermore, HOMO-LUMO energy levels of compounds 17 and 18, evaluated through cyclic voltammetry, were found to be −5.10, −5.15, and −2.56, −2.99 respectively with band gap energy values 2.54–2.61 eV. The DFT and TD-DFT computations at the B3LYP functional along with a 6-31G(d,p) basis set for a comprehensive study of spectral data, molecular orbitals (HOMO, LUMO) analysis, and electrostatic potential (MEP) surfaces are also presented. The Computational studies support the experimental findings. The findings hint towards the optoelectronic efficiency of 17 and 18, and their potential for further optimization and use in optoelectronic devices.

SYNTHESIS, CHARACTERIZATION OF COPPER(II) COMPLEX WITH TETRADENTATE N2O2 AND POTENTIAL CONTRIBUTION AS PROMISING ANTIBACTERIAL STUDIES

A square planar Schiff base complex, Cu(H2L) namely N,N’-bis(4-methyl-α-salicylidene)propane-1,3-diaminecopper(II) through the condensation reaction of ligand with copper(II) acetate in the molar ratio of 1:1 in acetonitrile solvent was successfully synthesized. The obtained complex was characterized using, elemental analysis of carbon, hydrogen and nitrogen (CHN), Fourier Transform Infrared spectroscopy (FTIR) and electronic spectra of ultraviolet-visible (UV-vis) spectroscopy. FTIR confirmed the coordinates the metal ion to form mononuclear complex via tetradentate (ONNO) atoms of the phenolic group and azomethine group, respectively. The antibacterial studies of H2L and its Cu(H2L) were determined by screening the compounds against selected various Gram (+) and Gram (-) bacterial strains such as Staphylococcus epidermidis, Bacillus subtilis, Staphylococcus aureus, Vibrio cholera, Enterobacter cloacae and Escherichia coli. Indeed, preliminary results exhibited Cu(H2L) more active than the free ligand and displayed promising antibacterial activity, while no effect has been observed on strains for H2L.

Solubility and Polymorphism of a HOF Monomer N1,N3,N5-Tris(pyridin-4-yl)benzene-1,3,5-tricarboxamide in 12 Neat Solvents at Temperatures from 283.15 to 323.15 K

A gravimetric method is adopted to measure the solid–liquid equilibrium of N1,N3,N5-tris(pyridin-4-yl)benzene-1,3,5-tricarboxamide (TPBTC), a hydrogen-bonded organic framework (HOF) monomer in different solvents (methanol, dichloromethane, isopropanol, n-hexane, acetone, ethanol, 2-butanone, n-butanol, acetonitrile, water, ethyl acetate, and n-propanol). The experiment is carried out at atmospheric pressure, and the experimental temperatures range from 283.15 to 323.15 K. The powder X-ray diffraction analysis was performed on the equilibrium solid-phase characterization of TPBTC in different solvents, and the solid form of solute in equilibrium with different solvents was a mixture of three kinds of crystalline forms and an amorphous form. In the 12 monosolvents, the solubility increased with absolute temperature, and the following order was obtained: 2-butanone > isopropanol > n-propanol > n-butanol > ethyl acetate > acetonitrile > methanol > ethanol > dichloromethane > n-hexane > acetone > water. In the studied temperature range, the maximum and minimum values were recorded for 2-butanone (0.6753 × 10–3 mol/mol at 323.15 K) and water (0.004650 × 10–3 mol/mol at 283.15 K), respectively. The solubility behavior and solvent effects in various solvents were first investigated by the hydrogen bond acceptor tendencies as the main factor then interpreted by solvent polarity, cohesive energy density, and steric effect for some exceptions. In addition, the solid–liquid equilibrium data of TPBTC were correlated with the Yaws model and the Apelblat model. Furthermore, the two thermodynamic models were evaluated using the Akaike Information Criterion and Akaike weights. It can be observed that the Yaws model was more appropriate than the Apelblat model.

Tuning the Polarity of Dinitrile-Based Electrolyte Solutions for CO2 Electroreduction on Copper Catalysts

The development of carbon dioxide electrochemical reduction (CO2ER) has mainly focused on aqueous electrolytes. However, the low solubility of apolar CO2 in polar water negatively impacts the electrochemical process, especially mass transport. Organic-based electrolytes, such as methanol, acetonitrile, and dimethylformamide, have been explored as an alternative due to increased CO2 solubility. Yet, insights into other organic electrolytes are scarce. Dinitrile solvents have decreased polarity in comparison to the mononitrile solvent acetonitrile and thus can potentially further increase CO2 solubility and advance the reaction’s performance. Herein, the novelty of dinitrile-based electrolytes for the application of CO2ER is explored. Acetonitrile, adiponitrile, and sebaconitrile were used to study the effects of a secondary nitrile group addition and the length of the aliphatic, nonpolar chain on salt solubility, electrolyte conductivity, and CO2 solubility. Electrochemical effects were evaluated through cyclic voltammetry (CV) and chronoamperometry (CA) measurements with copper (Cu) and copper oxide (CuO) commercial nanoparticle catalysts. DFT calculations were employed to further explore the CO2 interactions with the selected solvents. Finally, it was found that tuning the polarity of the nitrile solvent results in a profound effect on the physiochemical properties of the electrolyte solutions, markedly CO2 solubility and the CO2ER.

Study on electrochemical reduction mechanism of p-nitrophenylacetic acid prepared by electrocarboxylation

The direct carboxylation of organic halides under CO2 atmosphere by electrochemical reduction is an effective way to realize the value utilization of waste (CO2), and has great potential in green organic synthesis. P-nitrophenylacetic acid is a chemical raw material in great demand, which can be used not only in medicine and other organic synthesis intermediates but also in biochemical research. In this paper, the electrochemical reduction mechanism of p-nitrobenzyl bromide (PNBB) in N2 and CO2 atmosphere was investigated by cyclic voltammetry (CV), in-situ FT-IR spectroelectrochemistry, and bulk electrolysis experiments. Under N2 conditions, the electrochemical behavior of PNBB in aprotic acetonitrile solvent is a 1-electron irreversible transfer process. However, in the presence of CO2, it is a completely irreversible 2-electron transfer process. The electrolytic products were analyzed by 1H NMR, 13C NMR and MS. The results showed that the electrolytic products were 1,2-bis(4-nitrophenyl) ethane and p-nitrophenylacetic acid under N2 and CO2 conditions, respectively. The successful preparation of p-nitrophenylacetic acid provides more possibilities for the “green” synthesis of helpful chemical products from organic halides.

Novel Liquid Chromatography–Tandem Mass Spectrometry Method for Analysis of 102 Pesticides and Five Mycotoxins Regulated by the State of Colorado in Dried Hemp

A novel liquid chromatography–tandem mass spectrometry (LC–MS/MS) method with a dual electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) source was developed for analyzing 102 pesticides and five mycotoxins that are regulated by the state of Colorado in hemp. The limit of quantitation (LOQ) of the 102 pesticides and five mycotoxins met Colorado state action limit requirements for these analytes in a hemp matrix. For this study, 88 out of 102 pesticides and all five mycotoxins were analyzed using LC–MS/MS with an ESI source, whereas the remaining 14 pesticides were determined using LC–MS/MS with an APCI source. A simple, fast, green, and cheap acetonitrile solvent extraction method was used to extract the pesticides and mycotoxins from the hemp matrix with good extraction efficiency in the range of 80–120%. A hemp matrix is challenging and causes matrix effects such as ion suppression or enhancement. We optimized the LC method and added 30 internal standards to reduce and compensate for these matrix effects to obtain method accuracy in the range of 70–120%. The ionization mechanism of nonpolar pesticides (normally analyzed by gas chromatography–tandem mass spectrometry [GC–MS/MS]) with an APCI ion source was elucidated.

Molecular Characterization of Ochratoxin a Producing Indigenous Aspergillus Strains from Poultry Feed in Pakistan

Ochratoxin A (OTA) is nephrocarcinogenic and immunosuppressive toxin and OTA producing molds contaminate the food crops. Isolation and identification of ochratoxin producing fungi was carried out from poultry feed samples (n=120) followed by preliminary confirmation through macroscopic and microscopic characteristics. Purified fungal isolates identified as Aspergillus 1842(91.68%) followed by Penicillium 91 (4.53%), Mucor 52 (2.58), Alternaria 7 (0.35%), Cladosporium 6 (0.29%), Fusarium 4 (0.199%) and un-identified (07). OTA production was confirmed through thin layer chromatography (TLC) followed by high performance liquid chromatography (HPLC). Only 41 isolates (2.22%) out of 1842 Aspergillus isolates were able to produce toxin. At genetic level, characterization was performed through polymerase chain reaction (PCR) using species specific gene primers. From 41 isolates 27, 9 and 5 were characterized as Aspergillus terreus, Aspergillus parasiticus, and Aspergillus ochraceus respectively. Physical and chemical factors were optimized for OTA production. Under the effect of 37 °C temperature and 7.5 pH of Sabouraud dextrose broth (SDB) medium, higher toxin (969.45±.03 µg/mL) production was observed from ASPO-6 isolate. ASPO-4 isolate produce higher toxin amount in SDB medium with supplementation of maize 5%, wheat 1% and rice 3%. OTA stability was determined by adjusting standard concentration of 100 µg/mL in organic solvents (chloroform, acetonitrile and methanol) and organic solids. Least percentage log reduction in OTA concentration and stability of OTA was observed in opaque vials with chloroform and sucrose and transparent vials with sucrose after 6 months. OTA can be used as indigenous standard for identification of OTA from field samples.