Mixture Of N-hexane Research Articles

Determination of Diniconazole in Agricultural Products, Livestock and Marine Products by LC-MS/MS.

An LC-MS/MS method for the determination of diniconazole in agricultural products, livestock and marine products was developed. Diniconazole in agricultural products was extracted with acetone. The extract was concentrated and partitioned with n-hexane and 10% sodium chloride solution. Agricultural products such as grains and beans were defatted using n-hexane-acetonitrile. Livestock and marine products were extracted with a mixture of acetone and n-hexane, and the organic layer was evaporated to dryness. The residue was defatted using n-hexane-acetonitrile. Cleanup was carried out using a Florisil cartridge column and a graphitized carbon cartridge column for these samples. The LC separation was carried out on an Inertsil ODS-3 column with a linear gradient of 0.1% formic acid and acetonitrile containing 0.1% formic acid. MS was carried out in the positive ion electrospray ionization mode. The calibration curve was linear between 0.00125 to 0.00750 mg/L. Average recoveries (n=5) of diniconazole from 16 kinds of agricultural products, livestock and marine products fortified at the MRLs (0.01 ppm) were 88.3-108%, and the relative standard deviations were 0.5-5.1%. The limits of quantitation were 0.01 mg/kg.

Enantioseparation of racemic aminoglutethimide using asynchronous simulated moving bed chromatography

The separation of aminoglutethimide enantiomers by the continuous multicolumn chromatographic processes were investigated experimentally and theoretically, where the columns were packed with cellulose tris 3,5-dimethylphenyl-carbamate stationary phase (brand name Chiralcel OD) and mobile phase was a mixture of n-hexane and ethanol with monoethanolamine additive. The continuous enantioseparation processes included a synchronous shifting process (SMB) and an asynchronous shifting process (VARICOL), which allowed reducing the column number (here from six-column SMB to five-column VARICOL process). Transport-dispersive model with the consideration of both intraparticle mass transfer resistance and axial dispersion was adopted to design and optimize the operation conditions for the separation of aminoglutethimide enantiomers by SMB process and VARICOL process. According to the optimized operation conditions, experiments were carried out on VARICOL-Micro unit using five-column VARICOL process with 1/1.5/1.5/1 configuration and six-column SMB process with 1/2/2/1 configuration. Products of R-aminoglutethimide (R-AG) enantiomer and S-aminoglutethimide (S-AG) enantiomer with more than 99.0% purity were obtained continuously from extract stream and raffinate stream, respectively. Furthermore, the experiemntal data obtained from five-column VARICOL process were compared with that from six-column SMB process, the feasibility and efficiency for the separation of guaifenesin enantiomers by VARICOL processes were evaluated.

Composition of Asarum heterotropoides var. mandshuricum radix oil from different extraction methods and activities against human body odor-producing bacteria

In this study, oils from Asarum heterotropoides were extracted by traditional solvent extraction and supercritical CO2 (SC-CO2) extraction methods and their antioxidant activities along with antimicrobial and inhibitory activities against five human body odor-producing bacteria (Staphylococcus epidermidis, Propionibacterium freudenreichii, Micrococcus luteus, Corynebacterium jeikeium, and Corynebacterium xerosis) were evaluated. The oil was found to contain 15 components, among which the most abundant component was methyl eugenol (37.6%), which was identified at every condition studied in different extraction methods. The oil extracted with n-hexane and ethanol mixture exhibited a strong antioxidant activity (92% ± 2%) and the highest ABTS and 2,2-diphenyl-1-picrylhydrazyl scavenging activities (89% ± 0.2%). The highest amounts of total phenolic content and total flavonoid content were 23.1±0.4 mg/g and 4.9±0.1 mg/g, respectively, in the traditional method. In the SC-CO2 method performed at 200 bar/50°C using ethanol as an entrainer, the highest inhibition zone was recorded against all the aforementioned bacteria. In particular, strong antibacterial activity (38±2 mm) was found against M. luteus. The minimum inhibitory concentration (MIC) for the oil against bacteria ranged from 10.1±0.1 μg/mL to 46±2 μg/mL. The lowest MIC was found against M. luteus. Methyl eugenol was found to be one of the major compounds working against human body odor-producing bacteria.

Development of dynamic headspace-liquid phase microextraction method performed in a home-made extraction vessel for extraction and preconcentration of 1,4-dioxane from shampoo

In the present study, a new, simple, rapid, and environmentally friendly headspace-liquid phase microextraction method followed by gas chromatography–flame ionization detection has been developed for the extraction/preconcentration and determination of 1,4-dioxane from shampoo. The developed procedure is performed in a home-made extraction vessel, connected to a glass vial containing sample and extraction solvent. In this method, an aliquot weight of shampoo is mixed with a binary mixture of n-hexane and dichloromethane (50:50, v/v) as the extractant and the target analyte is extracted during a liquid–liquid extraction procedure. Then a home-made extraction vessel containing a few microliters of a collection/extraction solvent is contacted to a glass vial containing the organic phase obtained from the previous step. By heating 1,4-dioxane is vaporized and enriched in a μL volume of the collection/extraction solvent. Then an aliquot volume of the collected phase is injected into the separation system. The effect of several factors which may influence performance of the method, including kind and volume of the extraction solvents used in both steps, extraction temperature, extraction time, and salt addition were evaluated. Under the optimum extraction conditions, limits of detection and quantification for the target analyte were obtained 0.52 and 1.73 μg kg−1, respectively. Enrichment factor and extraction recovery were 333 and 89 %, respectively. The method precision was evaluated at a concentration of 25 μg kg−1 and relative standard deviation was less than 6.9 % for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method has been successfully applied in analysis of 1,4-dioxane in different shampoo samples.

PVTx properties of the binary 1-propanol + n-hexane mixtures in the critical and supercritical regions

PρTx relationship of the binary 1-propanol+n-hexane mixture were measured. Measurements were concentrated in the immediate vicinity of the critical and supercritical regions in order to closely observe the features of the mixture critical curve behavior (critical phenomena in the 1-propanol+n-hexane mixture) and other derived thermodynamic properties. The measurements have been made over the temperature range from (403 to 573) K for liquid and vapor isochores between (92 and 564) kg·m−3 up to 61MPa using a high-temperature and high-pressure constant-volume piezometer. The combined expanded uncertainty of the density, ρ, pressure, P, temperature, T, and concentration, x, measurements at the 95% confidence level with a coverage factor of k=2 is estimated to be 0.15%, (0.02 to 0.05) %, 10mK, and 0.01 mole %, respectively. The critical curve data (TC−x), (PC−x), and (ρC−x), were extracted from the measured PρTx data. The extracted critical curve and direct measured P−x data along the critical isochore-isotherm were used to estimate the value of the Krichevskii parameter for the mixture when 1-propanol is solvent at the critical state. The measured PρTx data were used to calculate excess and partial molar volumes of n-hexane near the critical point of pure 1-propanol. The isomorphic thermodynamic behavior of the mixture have been studied on the bases of critical curve data and the critical amplitudes of the pure solvent (1-propanol).

Determination and Distribution of Polycyclic Aromatic Hydrocarbons in Rivers, Sediments and Wastewater Effluents in Vhembe District, South Africa.

Polycyclic aromatic hydrocarbons are very toxic and persistent environmental contaminants. This study was undertaken to assess the concentrations and possible sources of 16 PAHs (Polycyclic aromatic hydrocarbons) classified by the United State Environmental Protection Agency as priority pollutants in water and sediments of the Mvudi and Nzhelele Rivers. Effluents from Thohoyandou wastewater treatment plant and Siloam waste stabilization ponds were also investigated. Diagnostic ratios were used to evaluate the possible sources of PAHs. PAHs in the water samples were extracted using 1:1 dichloromethane and n-hexane mixtures, while those in the sediment samples were extracted with 1:1 acetone and dichloromethane using an ultrasonication method. The extracts were purified using an SPE technique and reconstituted in n-hexane before analyses with a gas chromatograph time of flight—mass spectrometer. The results obtained indicate the prevalence of high molecular weight PAHs in all the samples. PAHs concentrations in water and sediment samples from all the sampling sites were in the range of 13.174–26.382 mg/L and 27.10–55.93 mg/kg, respectively. Combustion of biomass was identified as the major possible source of PAHs. Effluents from wastewater treatment facilities were also considered as major anthropogenic contributions to the levels of PAHs found in both river water and sediments. Mvudi and Nzhelele Rivers show moderate to high contamination level of PAHs.

Global phase behaviour in methane plus n-alkanes binary mixtures

The methane plus linear alkanes series is one of the simpler and most common type of mixtures presented in the industry and its accurate representation is paramount because of the diversity of its applications. From a theoretical perspective, its structural simplicity due to the low degree of synergy and the absence of short-range dispersive forces suggests that a good model should represent these systems with acceptable accuracy. Based on these ideas and the relatively regular behaviour of n-alkanes, these systems have become particularly suitable for trial calculation in convoluted models, in order to verify their capabilities in both quantitative and qualitative predictions. In this contribution, the soft-SAFT equation of state is used for the construction of the serial prediction domain global phase diagram (spd-GPD) of the methane plus linear alkanes series. The main goal is to address the capability of the equation of state to predict the global behaviour of the binary mixtures until methane plus n-decane, with special emphasis in accurately reproducing the mechanism and topology of mixtures. All systems shown here are predicted with quantitative accuracy, including a complete description of their taxonomy. The information obtained from the equation of state allows the validation of some predictions of the spd-GPD in the absence of experimental data. Following this analysis, the double retrograde behaviour lies between the methane plus propane and methane plus n-butane systems, while the tricritical transition of the series is found between the methane plus n-pentane and methane plus n-hexane mixtures. Also, the presence of the molar density inversion phenomenon is predicted to begin between the methane plus n-hexane and methane plus n-heptane systems, while no signals of mass density inversions are found on these mixtures.

Deposition of Cu/a-C:H Nanocomposite Films

In the present study is shown a novel vacuum-based technique that enables production of hard polymeric nanocomposite coatings with metal (Cu) nanoparticles. This method is based on the use of gas aggregation source (GAS) of Cu nanoparticles and plasma-enhanced chemical vapour deposition of a-C:H matrix that was deposited in a mixture of Ar and n-hexane on the substrates placed on the powered RF electrode. This approach makes it possible to control independently both the properties of the matrix by variation of the applied RF power and the amount of incorporated Cu nanoparticles that may be adjusted by operational parameters of the GAS. Characterisation of the films in terms of their chemical composition, morphology, optical and mechanical properties is described here alongside with description of Cu nanoparticles production using GAS with variable aggregation length.

Analysis of Organophosphate Esters in Sediment Samples Using Gas Chromatography-Tandem Mass Spectrometry

Abstract An efficient extraction and purification method coupled to gas chromatography-tandem mass spectrometry (GC-MS/MS) with electron impact (EI) was developed to determine eight organophosphate esters (OPEs) in sediment samples. OPEs were extracted from the sediments through vortex oscillation for 1 min and ultrasonic extraction using 20 mL of n-hexane and acetone mixture (1:1, V/V) for 10 min, followed by purification by Florisil solid phase extraction (SPE) column and quantitative determination by GC-MS/MS. The result showed that this pretreatment method was simple and less solvent consumption. At three spiked levels of 10, 20 and 50 μg L−1, the recovery of OPEs (except TEP) was between 80% and 120%, and the limits of detection for OPEs were 0.31 to 64.51 ng L−1, showing a good precision and accuracy in the determination of OPEs in sediment.

Ultrasonic Study of Binary Liquid Mixture of n-Hexane and Acetic Acid

Ultrasonic Study of Binary Liquid Mixture of n-Hexane and Acetic Acid

Enhanced removal of VOCs from aquifers during air sparging using thickeners and surfactants: Bench-scale experiments

The effects of controlled air flow paths during air sparging on the removal of volatile organic compounds were examined in this study using a two-dimensional bench-scale physical model. An aqueous solution of sodium carboxymethylcellulose (SCMC), which is a thickener, was used to increase the resistance of water to displacement by injected air in a region around the targeted zone. At the same time, an aqueous solution of sodium dodecylbenzene sulfonate (SDBS), which is a surfactant, was used to reduce the air entry pressure to enhance the air flow through the targeted region. Trichloroethene (TCE), dissolved in water, was used to represent an aqueous phase volatile organic compound (VOC). A binary mixture of perchloroethene (PCE) and n-hexane was also used as a nonaqeous phase liquid (NAPL). Controlled air flow through the source zone, achieved by emplacing a high viscosity aqueous solution into a region surrounding the TCE-impacted zone, resulted in increased TCE removal from 23.0% (control) to 38.2% during a 2.5h period. When the air flow was focused on the targeted source zone of aqueous phase TCE (by decreasing the surface tension within the source zone and its vicinity by 28dyn/cm, no SCMC applied), the mass removal of TCE was enhanced to 41.3% during the same time period. With SCMC and SDBS applied simultaneously around and beneath a NAPL source zone, respectively, the NAPL components were found to be removed more effectively over a period of 8.2h than the sparging experiment with no additives applied; 84.6% of PCE and 94.0% of n-hexane were removed for the controlled air flow path experiments (with both SCMC and SDBS applied) compared to 52.7% (PCE) and 74.0% (n-hexane) removal for the control experiment (no additives applied). Based on the experimental observations made in this study, applying a viscous aqueous solution around the source zone and a surfactant solution in and near the source zone, the air flow was focused through the targeted contaminant zone, enhancing the removal of VOCs from either an aqueous phase or a NAPL phase.

Determination of sulfonamides in beeswax by liquid chromatography coupled to tandem mass spectrometry.

The manuscript presents the development of a new method for the quantification of 16 sulfonamides in beeswax. Different sample preparation techniques were tested and modified to maximise the recovery of the target analytes and minimise the amount of coeluted impurities under conditions that provide reproducible results. The proposed method consisted of melting and dilution of beeswax in a mixture of n-hexane and isopropanol followed by extraction with 2% acetic acid. The extract was cleaned up by solid-phase extraction using strong cation exchange phase. Determination of the sulfonamides was achieved by liquid chromatography coupled to tandem mass spectrometry with the use of a pentafluorophenyl analytical column and applying a gradient elution with acetonitrile and 0.01% acetic acid as mobile phases. The limits of detection and limits of quantification ranged from 1 to 2μg/kg and from 2 to 5μg/kg, respectively. The recoveries varied between 65.2% and 117.8% while coefficient of variation of the method was less than 24.2% under intermediate precision conditions. Finally, the method was applied to the analysis of real samples of beeswax from beekeepers and commercial foundations manufacturers.

Application of Sustainable Integrated Process Design and Control for Four Distillation Column Systems

The objective of this paper is to present the application of sustainable integrated process design and control methodology for distillation columns systems. The sustainable integrated process design and control methodology is developed and able to find the optimal solution for a single distillation column to ensure the design is more cost efficient, controllable and sustainable to meet the product quality. The sustainable integrated process design and control problem for a distillation column system is typically formulated as a mathematical programming (optimization with constraints) problem, and solved by decomposing it to six sequential hierarchical sub-problems: (i) pre-analysis, (ii) design analysis, (iii) controller design analysis, (iv) sustainability analysis, (v) detailed economics analysis and (vi) final selection and verification. In the pre-analysis sub-problem, the concept of driving force is used to locate the optimal design-control-sustainable solution targets, which are defined at the maximum point of the driving force diagram. The sustainability analysis sub-problem was analysed by using the three-dimensional sustainability index. The results through separation of n-Pentane, n-Hexane, n-Heptane, n-Octane and n-Decane mixtures with four distillation column systems shows the methodology is capable to find the optimal solution for multiple distillation column systems that satisfies design, control and sustainability criteria in a simple and efficient way.

Tuning the predictive capacity of the PAMPA-BBB model

Due to its robustness and versatility, several variations of the blood–brain barrier specific parallel artificial membrane permeability assay (PAMPA-BBB) have been reported in the central nervous system (CNS) drug discovery practice. In this study, the impact of the main assay parameters on the predictive power of PAMPA-BBB was thoroughly investigated with 27, passively BBB-transported drug molecules with in vivo logBB data. The single and combined effects of the following variables were systematically studied and optimized: incubation time and temperature (4 vs. 18h, RT vs. 37°C), type of the read-out (UV-reader vs. HPLC), solvent composition (n-dodecane/n-hexane), lipid concentration (0–10w/v % PBLE), cholesterol content (0–1.66w/v %), and thickness of the lipid membrane, and the DMSO cosolvent content (5–20v/v %), respectively. Based on our results, solvent-driven and lipid-driven mechanisms of diffusion were identified in different assay conditions. Moreover, the analysis of membrane retention (MR%; the mole fraction of solute “lost” to the membrane) data obtained at various membrane compositions (volume of solvent and concentration of phospholipids) revealed the compound-specific nature of this parameter. The optimized conditions for the PAMPA-BBB were the following: 4h incubation at 37°C, detection by HPLC-DAD, iso-pH conditions (pH=7.4) with 5v/v % DMSO content in buffer solutions, and PBLE (10w/v %; without cholesterol) as membrane dissolved in the mixture of n-hexane:n-dodecane 3:1.

Coordination-Driven Self-Assembly of Carbazole-Based Metallodendrimers with Generation-Dependent Aggregation-Induced Emission Behavior.

A new family of 120° carbazole-based dendritic donors D1-D3 have been successfully designed and synthesized, from which a series of novel supramolecular carbazole-based metallodendrimers with well-defined shapes and sizes were successfully prepared by [2+2] and [3+3] coordination-driven self-assembly. The structures of newly designed rhomboidal and hexagonal metallodendrimers were characterized by multinuclear NMR ((1) H and (31) P) spectroscopy, ESI-TOF mass spectrometry, FTIR spectroscopy, and the PM6 semiempirical molecular orbital method. The fluorescence emission behavior of ligands D1-D3, rhomboidal metallodendrimers R1-R3, and hexagonal metallodendrimers H1-H3 in mixtures of dichloromethane and n-hexane with different n-hexane fractions were investigated. The results indicated that D1-D3 featured typical aggregation-induced emission (AIE) properties. However, different from ligands D1-D3, metallodendrimers R1-R3 and H1-H3 presented interesting generation-dependent AIE properties. Furthermore, evidence for the aggregation of these metallodendrimers was confirmed by a detailed investigation of dynamic light-scattering, Tyndall effect, and SEM. This research not only provides a highly efficient strategy for constructing carbazole-based dendrimers with well-defined shapes and sizes, but also presents a new family of carbazole-based dendritic ligands and rhomboidal and hexagonal metallodendrimers with interesting AIE properties.

Removal of VOCs at trace concentration levels from humid air by Microwave Swing Adsorption, kinetics and proper sorbent selection

Microwave Swing Adsorption, MWSA, is already established as an alternative way of heating and regenerating solids efficiently in adsorption operations. When zeolites are used for MWSA applications it becomes necessary to tailor the zeolite properties towards microwave heating while at the same time aiming to obtain the highest adsorption capacity and selectivity. These objectives may in some cases be contradictory. In this paper the adsorption of binary mixtures of n-hexane (500ppm) and water (15,000ppm) in air, together with the regeneration of the sorbents using microwaves is studied for three commercial, faujasite Y type zeolites: NaY, HY and DAY. In the Henry regime for adsorption of low concentrations of n-hexane, the Na exchanged zeolite shows the higher affinity for the n-hexane. However, when the binary mixtures are considered DAY zeolite, with higher Si/Al ratio, is more selective towards the adsorption of the alkane. During microwave heating of zeolites, the water adsorbed, the mobile cations of the zeolite framework and the hydroxyl groups on the surface of the zeolite contribute to the absorption of microwave energy. Both heating and desorption are considerably faster using MW, compared to conventional heating. The DAY zeolite with a Si/Al=40 has been found excellent candidate material for MWSA of n-hexane in binary mixtures with water, since it combines good adsorption capacity and efficient interaction with microwaves.

Semicontinuous Distillation of Quaternary Mixtures Using One Distillation Column and Two Integrated Middle Vessels

A novel semicontinuous system for the separation of quaternary liquid mixtures is presented in this work. This semicontinuous system is a process intensification technique that uses one distillation column and two integrated middle vessels to achieve a separation which would traditionally be carried out using three continuous distillation columns. The system is a theoretical extension of the conventional ternary semicontinuous process, which has been repeatedly demonstrated to be profitable at intermediate flow rates when compared to continuous systems. Dynamic simulation results are used to demonstrate feasibility and performance of the system for three examples: a mixture of n-hexane, n-heptane, n-octane, and n-nonane, a mixture of benzene, toluene, ethyl-benzene, and o-xylene, and a mixture of six alcohols and water. The results show that this new technique can achieve separation objectives while staying within safe operating limits. The semicontinuous system for the first example is compared to a conventional continuous system and is shown to be more profitable for low to intermediate production rates.

Design of a Flow Calorimeter for Hydrocarbon Fuel at Temperatures from (330 to 900) K and Pressures up to 6.0 MPa

The isobaric specific heat capacity of a kerosene type hydrocarbon fuel was measured online using a flow calorimeter, which was based on the energy conservation theory. The test temperatures covered from (330 to 900) K and operating pressures changed from (1.96 to 4.93) MPa. The isobaric specific heat capacity data have an expanded relative uncertainty of 2.54 % with a coverage factor of 2. The reliability and accuracy of the flow calorimeter measurement was verified by the water, n-hexane, and binary mixtures of n-heptane + n-octane and methanol + acetone, respectively. Finally, the isobaric specific heat capacities of a type of endothermic hydrocarbon fuel were measured and Cp–T diagrams were plotted at sub- and supercritical pressure.

A rapid and sensitive LC-MS/MS method for evaluation of the absolute oral bioavailability of a novel c-Met tyrosine kinase inhibitor QBH-196 in rats.

A sensitive, selective and high-throughput UPLC-MS/MS method was developed and validated for the determination of a novel c-Met tyrosine kinase inhibitor, QBH-196, in rat plasma. QBH-196 and its analog BH357 (IS) were extracted from rat plasma using a mixture of dichloromethane and N-hexane (2:3, v/v). The chromatographic separation was carried out on Phenomenex C18 column (50 × 2.1 mm, 2.6 µm particle size) with a gradient mobile phase of methanol (A) and water containing 0.05% formic acid (B) at a flow rate of 0.2 mL/min. The assay was performed by positive electrospray ionization in multiple reaction monitoring mode using transitions of m/z 622.68 → 140.41 for QBH-196 and m/z 591.19 →126.21 for the IS, respectively. Good linearity was obtained over the concentration range of 8.0-4000 ng/mL (r(2) > 0.99) for QBH-196 and the lower limit of quantification was 8.0 ng/mL in rat plasma. Validations of the method, including its sensitivity, extraction recovery, matrix effect, intra- and inter-day precision, accuracy and stability, were all within acceptable limits. The established method was successfully applied to determine absolute oral bioavailability of QBH-196 in rats for the first time. The mean oral absolute bioavailability of QBH-196 was found to be about 40.8% and the elimination half-life was 40.0 ± 13.1 h. This result suggested that QBH-196 exhibits good oral absorption in vivo, which is very important for the further development of QBH-196 as a new oral anticancer drug.

Isolation and Characterization of Scopoletin from The Bark of fagraea ceilanica thumb and Antioxidants Tests

Have done the isolation scopoletin compound from the bark of fagraea ceilanica Thunb by maceration method using n-hexane, ethyl acetate and methanol. Column chromatography with silica gel used for the isolation of the ethyl acetate extract fraction with a mixture of n-hexane and ethyl acetate as the mobile phase in the SGP (step Gradient Polarity). This way produces a dark yellow crystals (26 mg) with a melting point = 205-207 ° C. TLC (Thin Layer Chromatography) were eluted using a mixture of n-hexane: ethyl acetate (7: 3) gives (Rf 0.42). Based on the UV spectrum, shift reagents, IR spectrum and melting point of this compound compared with standard scopoletin showed that the isolated compounds are the same compound or isolated compound is scopoletin. The results of antioxidant test with DPPH of isolated compounds as weak antioxidants with IC 50 = 358.71 mg / L.