Aqueous Acetonitrile Solution Research Articles

Probing Isolated Water Molecules in Aqueous Acetonitrile Solutions Using Oxygen K-Edge X-ray Absorption Spectroscopy.

Oxygen K-edge X-ray absorption spectroscopy (XAS) of an aqueous acetonitrile solution exhibited a sharp peak at approximately 537 eV, which was similar to that of water vapor and was not observed in liquid water. The inner-shell spectra of isolated water molecules and water clusters of different sizes surrounded by acetonitrile molecules were obtained by extracting these water structures from the liquid structures of aqueous acetonitrile solutions, as calculated using molecular dynamics simulations. The sharp peak profiles of the O K-edge XAS spectra were derived not from water clusters but from isolated water molecules surrounded by acetonitrile molecules. The present study proposes that isolated water molecules are easily formed in aqueous acetonitrile solutions and that the electronic structures of the isolated water molecules can be analyzed using O K-edge XAS spectra, which separates the contributions of small water clusters.

Magnetic molecularly imprinted polymers are used to selectively extract cephalosporins from milk samples and analyze by LC-MS/MS

Cephalosporins were extracted from milk samples by using magnetic molecularly imprinted polymers (MMIP). To characterize the physical properties of MMIP, an experiment was conducted involving both static and dynamic adsorption. Samples were analyzed with LC-MS/MS to identify cephalosporin residues. The quantitative technique employed was the use of an isotope as an internal standard. Analysis was conducted using an Ascentis C8 column with a mobile phase consisting of a 0.1 % aqueous solution of formic acid and acetonitrile. The determination coefficients varied between 0.9945 and 0.9995, as indicated by the linear equations. Cephalosporins exhibited a diverse spectrum of recovery rates, varying between 80.7 % and 118.3 %, accompanied by a range of relative standard deviations spanning from 3.8 % to 13.5 %. The detection limits for 9 kinds of cephalosporins in milk samples varied from 1 μg kg−1 to 20 μg kg−1, while the quantification limits ranged from 3 μg kg−1 to 60 μg kg−1. The successful implementation of the validated technique has been applied to detect 9 different kinds of cephalosporins in real milk products.

Synthesis, structural characterization and antitumor activities of manganese and cobalt isothiocyanate complexes with 2,2’-bipyridine

[Mn(SCN)2(2,2′-bipy)2] (1) and [Co(SCN)2(2,2′-bipy)2] (2) were synthesized at ambient temperature by adding aqueous solutions of manganese(II) or cobalt(II) chloride hydrate to aqueous acetonitrile solutions of 2,2′-bipyridine (2,2′-bipy) and potassium thiocyanate. Elemental analyses, FT-IR and UV–vis spectra were used to characterize 1 and 2. Single crystal X-ray diffraction was used to analyze the crystal structures of 1 and 2, revealing that the two are structurally similar. The molecular structures of 1 and 2 consist of Mn or Co ion chelated by two molecules of 2,2′-bipy through four nitrogen atoms and two NCS anions, giving distorted octahedral geometries. The isothiocyanate group is not bridging, instead, two ligands coordinate in a cis arrangement to the manganese or cobalt center by their nitrogen atoms while the sulfur atoms are free. Through hydrogen bonding and π–π stacking interactions, the discrete units of 1 and 2 extend to 3D supramolecular networks with flower and fishbone-like structures. The luminescence behavior of 2,2′-bipy, 1 and 2 were investigated. On HepG2 (liver) and MCF-7 (breast) cancer cells, the anticancer effects of 1 and 2 were evaluated. The activity of 1 and 2 on MCF-7 is more significant than that of HepG2. The IC50 of 1 was lower in HepG2 and MCF-7 cells than for 2.

Are Hansen solubility parameters relevant in predicting the post-treatment effect on polyamide-based TFC membranes?

This study investigates the impact of solvent post-treatment on polyamide-based thin film composite (TFC) membranes, specifically examining the effect on commercial nanofiltration (NF) and reverse osmosis (RO) membranes. Na2SO4 rejection and increase in pure water permeance (PWP) were considered as the output parameters. The disparity in Hansen solubility parameters (HSP) between the post-treatment solution and the polyamide layer of the TFC membrane, denoted by Ra, is well adapted to understand the enhancement in water permeance through the membranes upon treatment. Aqueous solutions of dimethylformamide with a Ra value of 4, acetonitrile with a Ra value of 8.3, and ethanol with a Ra value of 12.7 were used as the post-treatment solutions. Our experimental design, based on the Box-Behnken design of Response Surface Methodology, incorporates variables such as the concentration of the solvent in the solution (% v/v), Ra value, and treatment time (s). Our findings demonstrate that the effect of post-treatment on the TFC membranes is not governed by the Ra value. Notably, while the post-treatment with the aqueous solution of acetonitrile, 80% v/v for 30 s, had considerable effects on NF membranes (124.5% enhancement in PWP; reduction of 3.5% in Na2SO4 rejection), its impact on RO membranes was negligible. Several factors explain this discrepancy, including the limitations of the HSP model for composite polymers, the inaccuracy of the PWP or salt rejection as a swelling indicator, variations in the HSP values of the polyamide layers for different membranes, and possible modifications in the interface between the support membrane and the polyamide layer. In summary, our study provides insights into the complex interactions between solvents and composite membranes, indicating that HSP alone is not a decisive factor in predicting post-treatment effects on polyamide-based TFC membranes.

Reusable Cu‐Poly(4‐vinylpyridine‐co‐ethylbenzene) Complex as Catalyst for Chan‐Lam C−N Cross Coupling

AbstractA novel heterogeneous polymer supported catalyst Cu‐PVPEVB has been developed by complexation of CuI in the matrix of the polymer poly(4‐vinylpyridine‐co‐ethylvinylbenzene). Characterization of the catalyst using different spectroscopic techniques revealed that the copper metal is bound through the pyridine substructure of the polymer. The versatility of the catalyst was established by utilizing it for Chan‐Lam coupling reactions in an eco‐friendly solvent methanol. High yields of C−N cross coupled products are obtained within a short time in presence of K2CO3 and 10 weight % of the catalyst having 13.6 weight % of copper. The catalyst could be recovered after carrying out the reaction by simple filtration and reused. Additionally, among a variety of N‐functionalized products synthesized during this study, an N‐phenyl isatin derivative was found to be promising candidate as a fluorescent probe for detection of the Hg2+ ion in aqueous acetonitrile solution.

The Preferential Solvation of Methyl Red in Various Binary Aqueous Solutions: Solvatochromism, Preferential Solvation Parameters, Microheterogeneity of Solvents and Polarity Scale.

The solvatochromic characteristics of methyl red were examined in several aqueous solutions from pure water, with methanol, ethanol, propanol, acetonitrile, and dioxane. In order to explain the preferred solvation of the probe azo dye in the binary mixed solvents, the solvent exchange model of Bosch and Roses was used to evaluate the association between the empirical solvent polarity scale (ET) values of MR and solvent composition. Non-linear solvatochromism of methyl red was noted in all aqueous mixtures containing methanol, ethanol, propanol, acetonitrile, and dioxane. In addition to calculating the local mole fraction of each solvent composition in the cybotactic area of the probe, the impact of the solvating shell composition on the preferential solvation of the solute dye was examined in terms of both solvent-solvent and solute-solvent interactions. The local mole fraction of each solvent composition in the cybotactic region of the probe was also calculated. The results indicated that the MR solvation shell was thoroughly saturated with the solvent complex S12 in the following order: dioxane > ethanol > methanol > acetonitrile > propanol. Data from the binary systems were analyzed with KAT parameters using a multi-model; in aqueous methanol and ethanol solutions, the hydrogen acidity was more responsible for the spectral shift, whereas in aqueous acetonitrile and dioxane solutions, the basicity has a greater influence.

Novel biologically active paddlewheel-like palladium thiocyanate complex catalyzed cyanation of alkyl bromide utilizing Q-tube system: A green perspective

A novel paddlewheel-like complex of [Pd(SCN)2(3-Acpy)2], (1) was produced at ambient temperature by adding an aqueous solution of palladium chloride to an aqueous acetonitrile solution of 3-acetylpyridine (3-Acpy) and potassium thiocyanate. Elemental analysis, Fourier-transform infrared (FT-IR), ultraviolet–visible (UV–vis), and nuclear magnetic resonance (NMR) spectroscopic methods were used to characterize complex 1 comprehensively. Single crystal X-ray diffraction was used to analyze the crystal structure of complex 1. The palladium atom is bonded to two 3-Acpy ligands and two thiocyanates groups in trans mode giving square planer geometry in complex 1. The discrete units of paddlewheel-like complex 1 through hydrogen bonding extend to form a 3D supramolecular network structure. The synthesized and characterized new palladium complex 1 was utilized as a precatalyst for the cyanation of alkyl bromide using potassium ferrocyanide as a benign cyanide source reagent. The suggested catalytic test reaction under high-pressure conditions via a Q-tube system in green solvent cyclopentyl methyl ether introduced high yields and a short reaction time. Moreover, the cytotoxic activity of complex 1 was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against HePG-2 of liver cancer and MCF7 of breast cancer cell lines. According to the findings, complex 1 has significant strong activity against the cancer cell lines HePG-2 and MCF-7. Additionally, the luminescence spectra of complex 1 were investigated.

Rapid determination of 87 prohibited ingredients in cosmetics by ultra performance liquid chromatography-tandem mass spectrometry

The methods of detecting numerous prohibited components are not included in the Technical Specifications for Cosmetic Safety (2015 Edition). Recently, owing to its high speed, sensitivity, and anti-interference properties, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) became the preferred method of detecting banned substances in cosmetics. In this study, a UPLC-MS/MS method was developed for use in determining 87 prohibited ingredients in cosmetics, including 33 sex hormones, 20 anti-infective drugs, 15 antihistamines, 7 coumarins, 4 sedative-hypnotic drugs, 4 antipyretic and analgesic drugs, 2 allergenic fragrances, and 2 drugs with vasoconstriction effects. The main factors affecting the response, recovery, and sensitivity of the method, such as the type of extraction solvent, extraction time, ratio of the mobile phases, and MS conditions, were optimized during sample pretreatment and instrumental analysis. Accordingly, approximately 0.2 g of the toner or cream sample was dispersed in 2 mL acetonitrile in a 10 mL colorimetric tube. After diluting to 10 mL with 50% acetonitrile aqueous solution, the sample was ultrasonically extracted for 20 min and centrifuged, and the mixture was then filtered through a 0.22 μm membrane. Approximately 0.2 g of the oil sample was dispersed in 2 mL n-hexane in a 15 mL polypropylene centrifuge tube and extracted twice with 3 mL 70% acetonitrile aqueous solution. The extracts were transferred into a 10 mL colorimetric tube and diluted to 10 mL with 50% acetonitrile aqueous solution, and the mixture was then filtered through a 0.22 μm membrane. The samples were separated using a CORTECS C18 column (150 mm×2.1 mm, 2.7 μm), employing a gradient elution program with acetonitrile and 0.1% formic acid aqueous solution as the mobile phases. The flow rate, column temperature, and injection volume were respectively set at 0.3 mL/min, 40 ℃, and 2 μL. The 87 compounds were monitored in multiple reaction monitoring (MRM) mode with electrospray ionization (ESI) under positive and negative conditions. Matrix-matched external standard calibration was used for quantification, and the analysis was completed within 33 min. The prohibited compounds exhibited good linear relationships, with r values of >0.99, and the limits of detection (LODs) and quantification (LOQs) for the 87 compounds were 0.07-0.38 and 0.21-1.15 μg/g, respectively. Three types of cosmetic matrices were selected to verify the recovery and precision of the method at LOQ, 2 LOQ, and 10 LOQ levels. The average recoveries of the 87 prohibited compounds were in the range of 81.7%-115.4%, and the relative standard deviations (RSDs, n=6) were 0.4%-9.9%. The reliability of the developed method was demonstrated by applying it to 349 commercial cosmetics obtained from the market, and 8 positive samples were identified. The positive components included trimethoprim, terbinafine, naphazoline, 7-methoxycoumarin, and 7-methylcoumarin. The established method displays the advantages of simple operation and rapidness and a high sensitivity and good recovery. And, this method provides technical support for rapid risk screening and the revision of national standards for cosmetics.

Determination of 145 pharmaceuticals and personal care products in eleven categories in water by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants frequently detected in aquatic environments at trace levels. These chemicals have diverse structures and physicochemical properties and includes pharmaceuticals like antibiotics, antihypertensive drugs, antiviral drugs, and psychotropic drugs that are widely used in large quantities worldwide. Considering the large number of pharmaceuticals currently in usage, it is crucial to establish a priority list of PPCPs that should be monitored and/or treated first. An accurate understanding of the occurrence and levels of PPCPs in aquatic environments is essential for providing objective materials for monitoring these emerging contaminants. Therefore, accurate, efficient, sensitive, and high-throughput screening techniques need to be established for determining and quantifying PPCPs. This study developed a method for the determination of 145 PPCPs (grouped into eleven categories: antibiotics, antihypertensive drugs, antidiabetic drugs, antiviral drugs, β-receptor agonists, nitroimidazoles, H2 receptor antagonists, psychotropic drugs, hypolipidemic drugs, non-steroidal anti-inflammatory drugs, and others) in water. The method was based on large volume direct injection without sample enrichment and cleanup and used ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS). Water samples were collected and filtered through a 0.22-μm regenerated cellulose (RC) filter membrane. Subsequently, Na2EDTA was added to the samples to adjust their pH to 6.0-8.0. Internal standards were mixed with the solutions, and because of the addition of Na2EDTA, the interference of metal ions could be eliminated in the determination of compounds, especially for tetracycline and quinolone antibiotics. Among the six filter membranes tested in this study (PES, PFTE-Q, PFTE, MCE, GHP, and RC), RC filter membranes were screened for water sample filtration. The UHPLC-MS/MS parameters were optimized by comparing the results of various mobile phases, as well as by establishing the best instrumental conditions. The 145 PPCPs were separated using an Phenomenex Kinetex C18 column (50 mm×3 mm, 2.6 μm) via gradient elution. The mobile phases were 0.1% (v/v) formic acid aqueous solution containing 5 mmol/L ammonium formate and acetonitrile for positive ion modes, 5 mmol/L aqueous solutions of ammonium formate and acetonitrile for negative ion modes. The samples were quantified using the scheduled multiple reaction monitoring (scheduled-MRM) mode with electrospray ionization in positive and negative ion modes. A standard internal calibration procedure was used to calculate contents of sample. The established method was systematically verified, and it demonstrated a good linear relationship. The average recoveries of the 145 PPCPs at the three spiked levels were in the range of 80.4%-128% with relative standard deviations (RSDs, n=6) of 0.6%-15.6%. The method detection limits (MDLs) ranged from 0.015 to 5.515 ng/L. Finally, the optimization method was applied to analyze the 145 PPCPs in 11 surface water samples and 6 drinking water samples. Overall, 93 (64%) out of the 145 analytes were detected. The total contents of the PPCPs in surface water samples ranged from 276.9 to 2705.7 ng/L. The detection frequencies of antidiabetic, antiviral, and psychotropic drugs were 100%. The total contents of the PPCPs in drinking water samples ranged from 140.5 to 211.5 ng/L, and antibiotics, antidiabetic drugs, and antiviral drugs comprised the largest proportion of analytes (by mass concentration) in drinking water samples. Our method exhibited high analytical speed and high sensitivity. It is thus suitable for the trace analysis and determination of the 145 PPCPs in environmental water and showed improved detection efficiency for PPCPs in water, indicating that it has a high potential for practical applications. This study can extend technical support for further pollution-level analysis of PPCPs in water and provide an objective basis for environmental management.

Development of a dispersive liquid-liquid microextraction method for the determination of plastic additives in seawater.

A method using dispersive liquid-liquid microextraction (DLLME) prior to high performance liquid chromatography-diode array detection (HPLC-DAD) was developed to determine seven additives from the plastics industry (butylated hydroxytoluene, diisodecyl phthalate, irgafos 168, lawsone, quercetin, triclosan and vitamin E) in seawater samples. These compounds can reach seawater due to direct discharge from wastewater treatment plants and leaching from plastics and microplastics. The extraction was performed using 25 mL of seawater, 500 μL of 1-octanol (extraction solvent) and a stirring step instead of dispersive solvent. Additive concentrations were determined by LC-DAD on a C18 column with a mobile phase of acetonitrile and phosphoric acid aqueous solution (pH 3.5) by gradient elution. The analytical recoveries ranged from 82 to 93% for all compounds, except for lawsone (60%). Repeatability and intermediate precision were adequate with RSD < calculated values following the Horwitz equation at the concentration levels evaluated (0.06 and 0.24 mg L-1). All additives exhibited linear matrix calibration curves (R2 > 0.99). Detection limits ranged from 0.009 to 0.028 mg L-1 and quantification limits ranged from 0.027 to 0.084 mg L-1. Finally, the application of the method to real samples verified the method as accurate and applicable to seawater.

Determination of furosine in liquid milk by high performance liquid chromatography-quadrupole time-of-flight mass spectrometry

Furosine is often used both domestically and internationally as an indicator of the degree of heating to evaluate milk quality. However, in actual detection, the complexity of the milk matrix may lead to the inaccurate quantification of furosine in liquid milk. Therefore, in this study, an efficient and accurate method based on high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF/MS) was established to determine furosine in liquid milk. A 2.00 mL milk sample was hydrolyzed with 5 mL 12.00 mol/L hydrochloric acid solution and 1 mL water at 110 ℃ for 12 h. After hydrolysis, vortex-mixing and filtration were performed. The filtrate was diluted six times with 6.00 g/L ammonium acetate solution and then analyzed. Gradient elution was performed with 0.20% formic acid aqueous solution and acetonitrile solution as mobile phases, followed by chromatographic separation on an AQ-C18 column (150 mm×3.5 mm, 5 μm). The data were collected by Q-TOF/MS with an electrospray ionization source operated in positive-ion mode. The accuracy of the quantification of furosine in milk was assessed by investigating the effects of the hydrochloric acid concentration (0.30, 1.25, and 3.00 mol/L) in the furosine solution on the MS response. The results showed that high hydrochloric acid concentrations inhibited the response signals. A good linear relationship was obtained in the mass concentration range of 0.05-2.00 mg/L, with a correlation coefficient (r) of 0.994. The limit of detection of the method was 0.50 mg/100 g, which meets the requirements of actual sample detection. The average recoveries of furosine ranged from 79.9% to 119.7% at three spiked levels of 1.52, 3.03, and 15.17 mg/100 g, with relative standard deviations of 1.4%-2.6%. The method was applied to detect 303 samples from 101 batches of pasteurized milk sold in the market, and the contents of furosine in these samples ranged from 5.1 to 11.9 mg/100 g. The proposed method is characterized with high efficiency, recovery, sensitivity, and accuracy. Thus, it can be used for the determination of large quantities of samples and provides technical support for the continuous promotion of the high-quality development of the whole dairy industry chain.

A single 8-hydroxyquinoline-appended bile acid fluorescent probe obtained by click chemistry for solvent-dependent and distinguishable sensing of zinc(II) and cadmium(II).

Construction of fluorescent probes for zinc ion (Zn2+ ) and cadmium ion (Cd2+ ) is significant for the safety of humans. However, the discriminating recognition of Zn2+ and Cd2+ by a single probe remains challenging owing to their similar properties. Herein, a novel deoxycholic acid derivative containing 8-hydroxyquinoline fluorophore has been facilely synthesized through click chemistry to form a clamp-like probe. Using its perfect bonding cavity from 1,2,3-triazole and quinoline, this molecule showed favorable solvent-dependent fluorescent responses and distinguished Zn2+ and Cd2+ in different solvents. In ethanol aqueous solution, it displayed good selectivity and ratiometric fluorescence to Zn2+ with 30 nm spectroscopic red-shifts. In acetonitrile aqueous solution, it exhibited good selectivity and ratiometric fluorescence to Cd2+ with 18 nm spectroscopic red-shifts. Moreover, the unique microstructural features of the probe in assembly were used to reflect its recognition processes. Due to its merits of low detection limit and instant response time, the probe was utilized for sensing Zn2+ and Cd2+ in water, beer and urine with high accuracy. Meanwhile, this probe served as a handy tool and was employed to obtain inexpensive test strips for the prompt and semiqualitative analysis of Zn2+ and Cd2+ with the naked eye.

Determination of nine organic amine compounds in CO2 absorption liquid by hydrophilic interaction liquid chromatography-electrostatic field orbitrap high resolution mass spectrometry

Carbon dioxide (CO2) absorption and capture is an effective measure to achieve the "dual carbon" goal of carbon peak and carbon neutrality in China. Organic amine compounds are widely used in the industrial separation and recovery of CO2. Thus, the establishment of analytical methods for organic amine compounds is of great significance for the research and development of carbon capture and storage (CCS) technology and carbon capture, utilization and storage (CCUS) technology. In this study, a method was developed for the determination of nine organic amine compounds in CO2 absorption liquid by hydrophilic interaction liquid chromatography (HILIC)-electrostatic field orbitrap high resolution mass spectrometry. The sample was diluted with water and filtered through a 0.22 μm nylon membrane before sampling and analysis. An Accucore HILIC column (100 mm×2.1 mm, 2.6 μm) was used for separation at 30 ℃. Gradient elution was conducted using 90% acetonitrile aqueous solution containing 5 mmol/L ammonium formate and 0.1% formic acid as mobile phase A and 10% acetonitrile aqueous solution containing 5 mmol/L ammonium formate and 0.1% formic acid as mobile phase B. Determination was performed using an electrospray ion source (ESI) in the positive ion mode. The quantitative analysis was carried out by standard addition method. The chromatographic retention performance of different chromatographic columns and the influence of different mobile phases on the separation of the organic amine compounds were compared, and the method was validated. The results showed that the linear ranges of the nine organic amine compounds were 0.04-25000 ng/mL with the linear correlation coefficients (R2) greater than 0.9910. The limits of detection (LODs) of the method were in the range of 0.0004-0.0080 ng/mL, and the limits of quantification (LOQs) of the method were in the range of 0.0035-0.0400 ng/mL. The average recoveries of the method ranged from 85.30% to 104.26% with relative standard deviations (RSDs) of 0.04%-7.95% at the spiked levels of 1, 1.5 and 3 times sample concentration. The established method was applied to detect the absorption waste liquid of a cement plant, and nine organic amine compounds could be effectively detected. The stability of the actual sample was tested, and the RSDs were 0.10%-6.35% in 48 h at 4 ℃. The method is sensitive, rapid and accurate for the determination of the nine organic amine compounds in industrial waste water. It can provide reference for the detection of organic amine compounds, and provide strong technical support for the research and industrial application of CO2 capture technology.

Resolution by diastereomeric salts: Access to both enantiomers of racemic acid using the same enantiomer of resolving base.

Racemic carboxylic acid, a Diels-Alder cycloadduct derived from 5-bromo-3-phenyl-α-pyrone and acrylate dienophile, was resolved into enantiomers by diastereomeric salt crystallization. Quinidine was used as a sole resolving base. The salt of (+)-acid crystallized from aqueous acetonitrile solution. Once this salt was separated by filtration, quinidine salt with (-)-acid crystallized from mother liquor. As a result, both enantiomers of Diels-Alder cycloadduct were isolated in high enantiomeric purity.

Rapid confirmation method of food poisoning caused by Bacillus cereus cereulide in rice and flour products

To develop a method for rapid determination of Bacillus cereus cereulide in rice and flour products by ultra-performance liquid chromatography-tandem mass spectrometry, providing emergency measures for food poisoning caused by cereulide. Single rice and flour samples were extracted with acetonitrile aqueous solution, salting out, after centrifuged and filmed, the organic phase was directly determined. The complex matrix samples fried rice and noodles were extracted with acetonitrile aqueous solution, cleaned up with HLB column, a ACQUITY UPLC Peptide BEH C_(18) 300Å column(2.1 mm×100 mm, 1.7 μm)was used for liquid chromatography separation, multiple reaction monitoring(MRM) mode was used for detection in electrospray ionization with positive ion mode, and quantified by the solvent standard curve method. At the spiked level of 0.5, 1.0 and 5.0 μg/kg, the recoveries of cereulide in negative steamed rice, steamed bread and noodles samples were 87.4%-98.3%, and the relative standard deviations were 1.4%-4.2%. At the spiking levels of 1.0, 2.0 and 5.0 μg/kg, the recoveries of cereulide in the negative samples such as fried steamed rice and fried noodles were 89.5%-99.3% with the relative standard deviations of 1.1%-7.5%(n=6). The detection limit of cereulide was 0.2-0.3 μg/kg, and the quantification limit was 0.5-1.0 μg/kg. The established method was applied to the detection of the actual samples causing food poisoning in a certain place in Beijing. The content of cereulide in poisoned food samples was 1287-7398 μg/kg, the content of cereulide in two raw materials cold noodles was 0.4 and 9.4 μg/kg. The method is simple, rapid, high sensitivity and accurate, and can realize the rapid treatment of food poisoning caused by cereulide.

Structures and catalytic properties of Cu(II) complex with chelating fluorinated ligands

Structure of Cu(II) complex with chelating fluorinated ligands were studied at 298 K and 90 K using CW X-band electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT). Spin-Hamiltonian and structural parameters have been determined and the latter were compared with the X-ray data showing good similarity. A phase transition occurred at 360 K in solid crystalline sample was observed by EPR and discussed. Qualitative kinetic analysis of the catalytic behavior of Cu(II) complex upon H2O2 decomposition in acetonitrile-aqueous solutions at 313 K was studied using EPR and UV–visible spectroscopy.

Determination of Oseltamivir in Human Plasma by HPLC-MS/MS.

A procedure for the determination of oseltamivir in human plasma by high-performance liquid chromatography( tandem mass spectrometry (HPLC-MS/MS) was proposed and validated. Arapid and easy-to-use method of liquid(liquid extraction with ethyl acetate using venlafaxine as an internal standard was used during sample preparation. The addition of benzoic acid to aqueous acetonitrile solutions of the analyte was shown to prevent its oxidative degradation. The detection limit and limit of quantitation were 0.08 and 0.30 ng/mL, respectively; the calibration range, 0.3-200 ng/mL (R 2 = 0.9937); the total analysis time, 3.2 min. The within- and between-run accuracy ranged from 97 to 105%. The precision was <10%. The proposed procedure was characterized by selective determination of the analyte, the absence of significant matrix effects, the ability to dilute samples with high analyte concentrations, and satisfactory extraction recovery (≥89%). The analyte was stable when stored in plasma samples (4 h at room temperature, 31 d at (80°C, after three freeze(thaw cycles) and extracts under autosampler storage conditions (24 h at 15°C). The procedure was successfully used for oseltamivir quantitation in actual plasma samples from healthy volunteers obtained during a bioequivalence study of the new generic drug.

A colorimetric and turn-on fluorescent sensor for rapid and selective detection of Fe3+ ion based on azo compound of 4-((4-(dimethylamino) phenyl)diazenyl)-N-(pyridin-2-yl)benzamide

A new colorimetric and turn-on fluorescent sensor based on an azo compound of 4-((4-(dimethylamino) phenyl) diazenyl)-N-(pyridin-2-yl)benzamide dye (L) was designed, synthesized and investigated. The structure of L was characterized by FT-IR, 1HNMR, 13CNMR and elemental analysis. The binding structures and sensing mechanisms of L toward iron were investigated using the various spectroscopic studies and theoretical calculations. Sensor exhibited highly selective and sensitive detection toward Fe3+ in acetonitrile aqueous solution. Compared to other metal cations, in case of iron, the color change from yellow to red was visible by the naked eye and a selective enhancement of fluorescence as well. The Job's method confirmed the formation of complex between L and Fe3+ with 1:1 binding stoichiometry. Furthermore, the detection limit (1.3 nM) for Fe3+ was much lower than that recommended by EPA (Environmental Protection Agency) for drinking water (5.37 µM). The theoretical calculations confirmed the coordination between nitrogen atom of pyridine and the oxygen atom of the carbonyl (C=O) group of L with Fe3+.

Equilibrium solubility and modeling of Glibenclamide in cosolvent mixtures of Methanol, n-Propanol, Isopropanol, and Acetonitrile + Water

Equilibrium solubility of glibenclamide (GCM) in aqueous solutions of methanol, n-propanol, isopropanol, and acetonitrile were studied by static technique at temperatures ranging from 288.15 K to 323.15 K under p = 101.3 kPa. When the composition of cosolvent was constant in the four mixed solvents, GCM solubility increased with the rising temperature. When the temperature was fixed, the GCM mole fraction solubility showed positive dependence on the increasing mass fraction of methanol in methanol + water mixture. While in solutions of n-propanol + water, isopropanol + water, and acetonitrile + water, it first increased as the mass fraction of cosolvent (w) added, at around w = 0.9, the solubility reached a maximum value and then it descended. Thermodynamic models like Jouyban−Acree model, modified Apelblat−Jouyban−Acree model, and CNIBS/R-K model were taken to correlate the equilibrium mole fraction solubility of GCM in four solvent mixtures. The maximum RAD and the RMSD values calculated by the CNIBS/R-K model were found in the mixture of methanol + water and didn’t exceeded 7.4 × 10−2 and 1.48 × 10−5, respectively. However, the maximum RAD values obtained by the Jouyban−Acree and modified Apelblat−Jouyban−Acree model were found in the mixture of acetonitrile + water and didn’t exceeded 5.57 × 10−2 and 5.55 × 10−2, respectively. The RMSD all didn’t exceeded 2.54 × 10−5. Hence, the Jouyban−Acree model and modified Apelblat−Jouyban−Acree model are shown to be superior to the CNIBS/R-K model in this work. The experimental data and model parameters obtained will be helpful for the preparation and purification of GCM.

Rapid screening of 14 antibacterial drugs in anti-acne cosmetics using ion mobility spectrometry coupled with solid-phase extraction

The main methods currently used to detect illegally added chemicals in cosmetics include thin-layer chromatography, high performance liquid chromatography (HPLC), gas chromatography (GC), and liquid chromatography-mass spectrometry (LC-MS). Compared with other analytical techniques, these methods have the advantages of high sensitivity, specificity, and accuracy, all of which are required in practical detection work. However, they also present a number of limitations, such as long analysis times and requirements for skilled operators and strictly controlled laboratory environments. Supervision, a growing trend in market surveillance, requires rapid and effective methods to screen illegally added chemicals. The suspected samples are sealed for some time and then sent to the laboratory for further testing. Ion mobility spectrometry (IMS) is a new type of trace gas separation technology that was developed in recent years. The principle behind IMS is the separation and characterization of chemical species based on differences in the migration speed of their gas-phase ions under an electric field. As this technology has the advantages of miniaturization, easy operation, and quick responses, it is widely used in food and drug quality testing, as well as other related fields. However, it is rarely used in cosmetic detection, likely because the cosmetics matrix is highly complex, which can interfere with ion determination. Thus, optimizing the pretreatment process of cosmetics for IMS is important. In this work, solid-phase extraction (SPE) is combined with IMS to establish a method for the rapid screening of 14 antibacterial drugs in anti-acne cosmetics. The IMS detection parameters, sample extraction conditions, and SPE clean-up conditions (SPE column, type of leachate, type and volume of eluent) were studied and optimized in detail. The sample was extracted with 80%(v/v) acetonitrile aqueous solution (containing 0.2% (mass fraction) trichloroacetic acid), loaded onto an activated Oasis® MCX SPE column, leached with 3.0 mL of methanol, and eluted with 1.0 mL of 2% ammonia methanol solution. The eluate was then directly injected into the IMS instrument. The IMS parameters were as follows: positive ion source voltage=2200 V, transfer tube voltage=8000 V, inlet temperature=180 ℃, transfer tube temperature=180 ℃, ion gate voltage=50 V, gate voltage pulse width=85 μs, and migration gas flow rate=1.2 L/min. The migration times for the 14 antibacterial drugs ranged from 11 to 17 ms, and the detection limits for the target compounds ranged from 0.2 to 1.2 μg/g. Owing to the narrow linear range of IMS, a quantitative method employing HPLC was also established to optimize the SPE pretreatment step and verify the positive samples. Chromatographic separation was conducted on a Phenomenex Luna C18 column (250 mm×4.6 mm, 5 μm), with a column flow rate of 1.0 mL/min and gradient elution with mobile phases A (0.01 mol/L potassium dihydrogen phosphate adjusted to pH 4.0 with phosphoric acid) and B (acetonitrile). The column temperature was set to 35 ℃, and the injection volume was fixed at 5 μL. A total of 25 cosmetics samples were screened, and one positive sample was found to be consistent with the results of HPLC. The proposed method is fast, simple, and efficient, and it can be used for the rapid screening of the 14 antibacterial drugs in anti-acne cosmetics. Pretreatment can significantly reduce the influence of the cosmetic matrices on the determination results, improve instrument sensitivity, and effectively decrease the occurrence rate of false positives and negatives. The technique developed in this work can improve the efficiency of screening for illegally added chemicals and expand the applications of IMS for detecting various chemicals in complex matrices, such as cosmetics.