Mixture Of N-hexane Research Articles

Energy conserving effects of dividing wall column

The energy-conserving performance of dividing wall column (DWC) is discussed in this paper. The heat transfer through the dividing wall is considered and the results are compared with that of common heat insulation dividing wall column (HIDWC). Based on the thermodynamic analysis of heat transfer dividing wall column (HTDWC) and HIDWC, both computer simulation and experiments are employed to analyze the energy-conserving situation. Mixtures of n-hexane, n-heptane and n-octane are chosen as the example for separation. The results show that the energy consumption of HTDWC is 50.3% less than that of conventional distillation column, while it is 46.4% less than that of HIDWC. It indicates that DWC is efficient on separating three-component mixtures and HTDWC can save more energy than HIDWC. Thus it is necessary to consider the heat transfer while applying DWC to industry.

Viscosity measurement and modeling for mixtures of Athabasca bitumen/hexane

Abstract Unconventional oils are very viscous and immobile at reservoir conditions; hence, recovery techniques that are used in conventional reserves are not applicable and practical for heavy oil and bitumen resources. Thus, addition of heat or solvent is required to reduce viscosity of these fluids for both recovery from reservoir and transportation. Thus, in this study, the viscosity of Athabasca bitumen and n-hexane mixtures was measured at different temperatures, pressures, and solvent weight fractions. The results indicated a huge reduction in viscosity of bitumen by increasing the temperature and/or dissolving the solvent. The viscosity of the mixtures showed a curvilinear trend with respect to the solvent weight fraction and temperature. The impact of pressure on the mixture viscosity is more pronounced at lower solvent weight fractions and lower temperatures. The evaluation of different models for mixture viscosity indicated that the power law and Cragoe׳s models represent the viscosity data over wide range of operating conditions better than other models.

Measurement, correlation and prediction of isothermal vapor–liquid equilibria of different systems containing vegetable oils

Thermodynamic properties, in particular vapor–liquid equilibrium (VLE) data, are required for the development of reliable predictive models for systems with fatty compounds. Isothermal VLE data have been measured for mixtures of methanol, ethanol, or n-hexane with refined vegetable oils (soybean, sunflower and rapeseed) at 348.15K and 373.15K using a computer-driven static apparatus. The oils were characterized in terms of their fatty acid and corresponding triacylglycerol (TAG) compositions. For the mixtures containing vegetable oils and n-hexane a negative deviation from Raoult’s law was observed and a homogeneous behavior (no miscibility gap) was found, while the mixtures with alcohols exhibited positive deviation from ideal behavior and, in some cases, limited miscibility. On the basis of the composition of the studied vegetable oils, their relative van der Waals volume and surface area parameters were estimated by the Bondi method and their vapor pressure by a group contribution method developed by Ceriani and Meirelles [1]. The experimental VLE data were correlated together with available excess enthalpies (HE) and activity coefficients at infinite dilution (γi∞) data using the UNIQUAC model. For the fitting process the refined vegetable oil was treated as a single triacylglycerol (pseudo-component) which has the corresponding degree of unsaturation, number of carbon atoms and molar mass of the original oil composition. The overall-average errors (AAE) using UNIQUAC model are 4.46% for VLE, 7.07% for γi∞ and 5.80% for HE The experimental data were also compared with the predicted results using mod. UNIFAC (Dortmund) and an extension of this method proposed for triacylglycerols in a previous work was also tested.

Metabolomics study of Saw palmetto extracts based on 1H NMR spectroscopy

Preparations containing Saw palmetto extracts are used in traditional medicine to treat benign prostatic hyperplasia. According to the European and the American Pharmacopoeias, the extract is obtained from comminuted Saw palmetto berries by a suitable extracting procedure using ethanol or supercritical carbon dioxide or a mixture of n-hexane and methylpentanes. In the present study an approach to metabolomics profiling using nuclear magnetic resonance (NMR) has been used as a finger-printing tool to assess the overall composition of the extracts. The phytochemical analysis coupled with principal component analysis (PCA) showed the same composition of the Saw palmetto extracts obtained with carbon dioxide and hexane with minor not significant differences for extracts obtained with ethanol. In fact these differences are anyhow lower than the batch-to-batch variability ascribable to the natural-occurring variability in the Saw palmetto fruits' phytochemical composition. The fingerprinting analysis combined with chemometric method, is a technique, which would provide a tool to comprehensively assess the quality control of Saw palmetto extracts.

Evaluation of permeation of macauba oil and n-hexane mixtures through polymeric commercial membranes subjected to different pre-treatments

Macauba is a Brazilian palm tree with high edible oil productivity and of great interest to many applications. In the oil extraction process, solvent recovery is one point of major concern, due to its high energy consumption and oil quality losses. Those drawbacks can be partially overcome by integration of membrane technology to the usual solvent distillation step. The present work tested four ultrafiltration (UF) and one nanofiltration (NF) membrane (Microdyn-Nadir) on the solvent recovery of synthetic mixtures of macauba oil and n-hexane. Membranes were pre-treated before use with different solvents in specific time lengths, according to preliminary studies. The membrane performance was evaluated by permeate flux and oil retention. Macauba (pulp and kernel) oil was evaluated by determinations of acidity, peroxide value and fatty acid profile. Membranes showed usual flux behaviour, compatible with other studies concerning oil/solvent mixtures permeation, although its values were quite above the expected. Best results for retention (>30%) are related to the membranes with lower molar mass cut-off (MMCO), and the best balance between permeate flux and oil retention was found for the NF membrane (12.4gm−2h−1, 34.7%).

Fatty Acid Characteristics of Isochrysis galbana Lipids Extracted Using a Microwave-Assisted Method

Lipids were extracted from Isochrysis galbana using a microwave-assisted method accompanied by various types of organic solvents. The effects of organic solvent type and microwave input energy on the fatty acid characteristics of the extracted lipids and their biodiesel product were investigated. Variations in the characteristics of the lipids extracted using a combination of n-hexane and iso-propanol solvents in both emulsion and direct mixtures were also compared. The experimental results showed that greater quantities of Isochrysis galbana lipids, and fatty acid methyl esters transesterified from those lipids, were extracted when using microwave irradiation with an organic solvent mixture of n-hexane and isopropanol in a 2:1 volumetric ratio than when using either n-hexane or isopropanol as the sole solvent. A greater quantity of Isochrysis galbana lipids was extracted when an emulsion of isopropanol solvent evenly dispersed in the continuous phase of n-hexane solvent was used than when a direct mixture of the two solvents was used. In addition, the quantity of lipids extracted from the dried Isochrysis galbana powder with the assistance of microwave irradiation was 9.08 wt% greater than when using traditional Soxhlet extraction without microwave irradiation.

Determination of explosion limits – Criterion for ignition under non-atmospheric conditions

Many industrial processes are run at non-atmospheric conditions (elevated temperatures and pressures, other oxidizers than air). To judge whether and if yes to what extent explosive gas(vapor)/air mixtures will occur or may be generated during malfunction it is necessary to know the safety characteristic data at the respective conditions. Safety characteristic data like explosion limits, are depending on pressure, temperature and the oxidizer. Most of the determination methods are standardized for ambient conditions. In order to obtain determination methods for non-atmospheric conditions, particularly for higher initial pressures, reliable ignition criteria were investigated. Ignition tests at the explosion limits were carried out for mixtures of methane, propane, n-butane, n-hexane, hydrogen, ammonia and acetone in air at initial pressures up to 20 bar. The tests have been evaluated according to different ignition criteria: visual flame propagation, temperature and pressure rising. It could be shown that flame propagation and occasionally self-sustained combustion for several seconds occurred together with remarkable temperature rise, although the pressure rise was below 3%. The results showed that the combination of a pressure rise criterion of 2% and a temperature rise criterion of 100 K seems to be a suitable ignition criterion for the determination of explosion limits and limiting oxidizer concentration at higher initial pressures and elevated temperatures. The tests were carried out within the framework of a R&D project founded by the German Ministry of Economics and Technology.

Level of Organochlorine Pesticides Residue in Fish, Water and Sediment in Biu Dam (Reservoir) Borno State Nigeria

The health risks posed by organochlorine compounds to the total environment have continued to elicit concern among researchers in developing countries worldwide. Hence, this study focused on investigating the levels of Organochlorine pesticides residues in water sediment and fish samples in Biu dam reservoir. The pesticides residues in the fish and sediment samples were extracted by soxhlet extraction process using a mixture of n-hexane and acetone while w ater sample was extracted using dichloromethane liquid- liquid extraction method. The extracts were cleaned and analysed using a gas chromatograph mass spectrometer (GCMS) equipped with electron capture detector. Endrin, aldrin, dieldrin, endosulfan I, endosulfan II, alpha BHC and heptachlor were detected in the study area. While chlordane, methoxychlor, other isomers of BHC, DDT and its degradation products were not detected in all the samples analysed. Endrin had the highest value

Treatment of Dynamic Mixture of n-Hexane, Benzene, and Methanol and Fungi Community Characterization in an Integrated Scheme of Cyclic Adsorption/Desorption Beds and Trickle Bed Air Biofilter

This study investigates the effect of volatile organic compound (VOC) feed fluctuations on trickle bed air biofilters (TBABs) and the ability of a two-bed adsorption/desorption unit in dampening fluctuations. A mixture of n-hexane, benzene, and methanol with concentration ratios of 1:3:6.6 was fed to two parallel TBABs. To simulate feed fluctuations, four different square waves were applied. The total VOC loading rates (LRs) varied from 28.4 to 107.3 g/m3 h. The average concentration of VOCs applied to both TBABs was within allowable limits as determined in an earlier study. One TBAB was preceded by a two-bed cyclic adsorption/desorption unit (integrated unit), while the other TBAB (control unit) was directly subjected to the high and low peaks. n-Hexane elimination in the integrated unit was steady, and stable performance was obtained (75%-89%) based on the LRs, whereas the control unit showed erratic performance. The other two VOCs were mostly removed.

Organochlorine Pesticides and Polychlorinated Biphenyls in Atmospheric Particles Collected in Zagreb, Croatia

We studied the occurrence and levels of hexachlorobenzene, alpha-, beta-, and gamma-hexachlorocyclohexane, 4, 4'-DDT, 4, 4'-DDE, 4, 4'-DDD, and 17 PCBs (six indicator and eleven other toxicologically significant congeners) in PM10 and/or PM2.5 particle fractions collected between 2000 and 2003 and in 2010 at a site in the northern residential part of Zagreb, Croatia. Twenty-four-hour particle samples were collected on glass or quartz microfibre filters from approximately 100 m3 of ambient air per filter. Filters with particles collected over seven consecutive days were combined for ultrasonic extraction with 1:1 acetone:n-hexane mixture followed by capillary gas chromatography with electron capture detection. In the monitored periods, the mass concentrations of organochlorine compounds in atmospheric particles were characteristic of global environmental pollution and showed a decreasing trend. Local input was observed only for gamma-hexachlorocyclohexane. There were no pronounced seasonal variations in the mass fraction levels of any pesticide or PCB in airborne particles. A decreasing trend in the mass concentrations of some compounds with higher air temperatures was mostly related to the lower particle concentrations in warmer seasons and, consequently, to less particle-bound organochlorine compounds in the atmosphere.

Isolation, characterization and x-ray structure determination of the schiff base ligand: 5-methyl-2-phenyl-4-[phenyl-(4-phenyl-thiazol-2-ylamino)-methylene]-2,4-dihydro-pyrazol-3-one

The structure of the amine tautomer of the new Schiff base derived from 4-benzoyl-5-methyl-2-phenyl-2,4-dihydro-pyrazol- 3-one (2) and 4-phenyl-thiazol-2-ylamine (3) was confirmed by means of single crystal X-ray diffraction. The title compound (4) was synthesized and crystals were grown from a mixture of dichloromethane and n-hexane (1:3). Single crystal X-ray diffraction analysis show that the structure is primarily stabilized by strong intramolecular N3–H3A···O1 hydrogen bonds [N3–H3A = 0.883(19) A, H3A···O1=1.925(18) A, N3···O1=2.6901(13) A, with an angle for N3–H3A···O1=144.1(17) °] and this leads to the formation of a pseudo nine-membered hydrogen bonded pattern. Elemental analysis, FTIR andNMRanalyses have been employed to characterize the crystal. KEYWORDS Pyrazolone, thiazole, Schiff base, tautomer, X-ray structure. PDF and Supp files attached

Development of Determination Method of Ipfencarbazone in Agricultural Products, Livestock Products and Seafood by LC-MS/MS

A method for the determination of ipfencarbazone in agricultural products, livestock products and seafood by LC-MS/MS was developed. Agricultural samples were extracted with acetone. An aliquot of crude extract was partitioned with n-hexane and sat. sodium chloride solution. Clean-up was performed using GC/PSA and C18 cartridges. In the case of livestock products and seafood, samples were extracted with a mixture of acetone and n-hexane, and the organic layer was collected. After acetonitrile-hexane partitioning, the extract was cleaned up using PAS and C18 cartridges. The gradient LC separation was performed on a C18 column with acetonitrile-water containing acetic acid as a mobile phase, and MS with positive ion electrospray ionization was used for detection. The average recoveries (n=5) of ipfencarbazone from 16 kinds of agricultural products, livestock products and seafood spiked at the MRLs or at the uniform limits (0.01 ppm) were 73-101%, and the relative standard deviations were 1.3-5.1%. The limit of quantitation of the developed method was 0.01 mg/kg for ipfencarbazone.

High Throughput LC-MS/MS Method for Simultaneous Estimation of 9-Cis- Retinoic Acid and its Metabolite 4-Oxo-9-Cis-Retinoic Acid in Human Plasma and its Application to a Bioequivalence Study

A liquid chromatography mass-spectrometric method is described for the simultaneous estimation of 9-cisretinoic acid and 4-oxo-9-cis-retinoic acid in human plasma using 13-cis-retinoic acid-d5 as an internal standard. Chromatographic separation of these retinoids was achieved on Chromolith Performance RP18 (100 × 4.6 mm) column using binary flow program of two mobile phase. 9-cis-retinoic acid and 4-oxo-9-cis-retinoic acid were extracted from human plasma by liquid-liquid extraction with a mixture of ethyl acetate, n-hexane and iso propyl alcohol (30:65:5, v/v/v). Quantification was achieved by monitoring transitions of m/z 299.4→255.2 for 9-cisretinoic acid, m/z 313.4→269.3 for 4-oxo-9-cis-retinoic acid and 304.4→260.2 for isotretinoin-d5 in multiple reaction monitoring, using turbo ion source in negative polarity. The linearity was established over a dynamic range of 2.85- 450.51 ng/mL and 2.33-180.57 ng/mL for 9-cis-retinoic acid and 4-oxo-9-cis-retinoic acid, respectively. At the lower limit of quantification level, the intra-and inter-day precision values of 9-cis-retinoic acid were within 5.9% and 6.0%, respectively, whereas that of 4-oxo-9-cis-retinoic acid were within 13.8% and 11.3%, respectively. The method was successfully applied for the simultaneous estimation of 9-cis-retinoic acid and 4-oxo-9-cis-retinoic acid in healthy volunteers, after oral administration of 30 mg alitretinoin capsule for bioequivalence study.

Development of a Stability-Indicating Stereoselective Method for Quantification of the Enantiomer in the Drug Substance and Pharmaceutical Dosage Form of Rosuvastatin Calcium by an Enhanced Approach.

A novel, simple, precise, and stability-indicating stereoselective method was developed and validated for the accurate quantification of the enantiomer in the drug substance and pharmaceutical dosage forms of Rosuvastatin Calcium. The method is capable of quantifying the enantiomer in the presence of other related substances. The chromatographic separation was achieved with an immobilized cellulose stationary phase (Chiralpak IB) 250 mm x 4.6 mm x 5.0 μm particle size column with a mobile phase containing a mixture of n-hexane, dichloromethane, 2-propanol, and trifluoroacetic acid in the ratio 82:10:8:0.2 (v/v/v/v). The eluted compounds were monitored at 243 nm and the run time was 18 min. Multivariate analysis and statistical tools were used to develop this highly robust method in a short span of time. The stability-indicating power of the method was established by subjecting Rosuvastatin Calcium to the stress conditions (forced degradation) of acid, base, oxidative, thermal, humidity, and photolytic degradation. Major degradation products were identified and found to be well-resolved from the enantiomer peak, proving the stability-indicating power of the method. The developed method was validated as per International Conference on Harmonization (ICH) guidelines with respect to specificity, limit of detection and limit of quantification, precision, linearity, accuracy, and robustness. The method exhibited consistent, high-quality recoveries (100 ± 10%) with a high precision for the enantiomer. Linear regression analysis revealed an excellent correlation between the peak responses and concentrations (r2 value of 0.9977) for the enantiomer. The method is sensitive enough to quantify the enantiomer above 0.04% and detect the enantiomer above 0.015% in Rosuvastatin Calcium. The stability tests were also performed on the drug substances as per ICH norms.

Liquid–Gas Phase Equilibria of Hydrocarbons in Water + n-Pentane and Water + n-Hexane Mixtures

The pVT-properties of water + n-pentane and water + n-hexane mixtures in temperature intervals from 305 to 542 K and pressures up to 15 MPa were measured in a constant-volume piezometer. The line of phase equilibrium hydrocarbon–vapor with water and their critical parameters were determined. Critical temperatures and pressures are constant and close to 0.9 mol fraction of water, remaining the same as for the upper critical end-point, while the densities increase. All critical parameters decrease above 0.93 mol fraction of water. The common three-phase lines for measured systems are presented.

Simultaneous determination of valsartan and hydrochlorothiazide in a tablet dosage form by liquid chromatography

A selective, rapid and accurate liquid chromatographic method is described for the simultaneous determination of valsartan (VAT) and hydrochlorothiazide (HTZ) in a solid dosage form. The chromatographic separation of two drugs were achieved on Lichrosphere CN column 250 mm × 4.0 mm,5 µm, Merck-India. The mobile phase consisting mixture of methanol, isopropyl alcohol and n-hexane in the ratio of 50:25:25 v/v was delivered at a flow rate of 1.0 ml/min. Detection was performed at 265 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range 40 to120 µg/ml for VAT and 6 to 18 µg/ml for HTZ, respectively. Seperation of VAT and HTZ were achieved in 5 min along with possible degradants. The proposed method can be used for the quantitative analysis of VAT and HTZ in formulation product. Key words: Valsartan, hydrochlorothiazide, liquid chromatography.

Simultaneous determination of rosuvastatin and amlodipine in human plasma using tandem mass spectrometry: Application to disposition kinetics

The liquid chromatography–tandem mass spectrometric assay method for the simultaneous determination of rosuvastatin and amlodipine in human plasma using deuterated analogs as internal standards has been developed and validated. The analytes were extracted from 100μL aliquots of human plasma via liquid–liquid extraction using a mixture of ethyl acetate and n-hexane (80:20, v/v) as an extraction solvent. The optimized mobile phase was composed of 0.1% formic acid in 5mM ammonium acetate, methanol, and acetonitrile (20:20:60, v/v/v) and delivered at a flow rate of 0.75mL/min. The calibration curve obtained was linear (R2⩾0.999) over the concentration range of 0.52–51.77ng/mL for rosuvastatin and 0.10–10.07ng/mL for amlodipine. A sample turnover rate of less than 2.5min makes it an attractive procedure in high-throughput bioanalysis of rosuvastatin and amlodipine. The present method was found to be applicable to clinical studies and the results were authenticated by incurred sample reanalysis.

Crystal structure of bis-{μ-2-[(di-methyl-amino)-meth-yl]ferrocene-seleno-lato}bis[chlorido-palladium(II)

The dinuclear title compound, [PdCl{Se[(C5H5)Fe(C5H3)2CH2N(CH3)2]}]2 was obtained by the reaction of [PdCl2(NCPh)2] with 2-[(N,N′-di­methyl­amino)­meth­yl]ferro­cene­seleno­late and the crystals for the structure determination were grown from a mixture of THF and n-hexane. Both PdII atoms are coordinated by the bridging Se atoms and by the amino N atoms of the bidentate 2-[(N,N′-di­methyl­amino)­meth­yl]ferrocene­seleno­late ligand, as well as by Cl atoms, and show a distorted square-planar coordination. The angle between the Pd—Se—Se planes of the two Pd atoms is 149.31 (3)°. Weak Cl⋯H hydrogen bonds link the binuclear complexes into a three-dimensional network.

Multiresidue analysis of 30 organochlorine pesticides in milk and milk powder by gel permeation chromatography-solid phase extraction-gas chromatography-tandem mass spectrometry

A method for simultaneous determination of the 30 organochlorine pesticides (OCP) in milk and milk powder samples has been developed. Prior to the gas chromatography-tandem mass spectrometric analysis, the residual OCP in samples were extracted with n-hexane and acetone mixture (1/1, vol/vol) and cleaned up by gel permeation chromatography and solid phase extraction. Selected reaction monitoring mode was used for gas chromatography-tandem mass spectrometric data acquisition to identify and quantify the OCP. To avoid the matrix effects, matrix-matched calibration solutions ranging from 2 to 50 ng/mL were used to record the calibration curve. Limits of quantification of all OCP were 0.8μg/kg. With the exception of endrin, limits of quantification are significantly lower than maximum residue limits set by the European Union and China. The average recoveries were in the range of 70.1 to 114.7% at 3 spiked concentration levels (0.8, 2.0, and 10.0μg/kg) with residual standard deviation lower than 12.9%. The developed method was successfully applied to analyze the OCP in commercial milk products.

Biodegradation of a Ternary Mixture of Hydrophobic and Hydrophilic VOCs in Trickle Bed Air Biofilters

The main objective of this study was to evaluate the degradation of a ternary mixture of n-hexane, benzene, and methanol fed to two Trickle Bed Air Biofilters (TBABs) designated as “A” and “B”. Both TBABs were loaded with pelletized diatomaceous earth support media and run at an empty bed residence time (EBRT) of 120 s. TBABs “A” and “B” were operated at pH 4 and fed with n-hexane:benzene:methanol (CH:CB:CM) concentrations ratios of 1:3:10 and 1:3:6.6, respectively under different loading rates. The influent total loading rates varied from 39.2 to 117.7 g/m3h and from 32 to 96.4 g/m3h for TBABs “A” and “B”, respectively. In both TBABs, methanol and benzene were the most eliminated volatile organic compounds (VOCs), while the removal of n-hexane was controlled by the VOCs ratios. Higher removal efficiencies were obtained for the VOCs ratio of 1:3:6.6 corresponding to a total VOCs load of 96.4 g/m3h. The addition of VOCs mixture to the TBABs resulted in change of the fungi community within the TBABs as compared to the fungi community when the TBABs were previously receiving only n-hexane as a sole substrate.