Hexane Solubles Research Articles

Thermodynamic consideration of dissolution and distribution behavior of carvedilol in pharmaceutical significant media

The key physico-chemical properties for pharmaceutical design as solubility and distribution coefficients of cardiovascular carvedilol (CVD) in modeling solvents and biphasic systems were determined using the classic shake flask method in the temperature range (293.15–313.15) K. The drug solubility in 1-octanol and hexane was measured at first time. The equilibrium mole fraction solubility of CVD at reference temperature was changed in following order: 1-octanol (2.79∙10-3) > hexane (4.56∙10-6) > buffer pH 2.0 (3.39∙10-6) > buffer pH 7.4 (1.53∙10-7). Solubility pH-profile was characterized a weak solubility in acidic media and very poor solubility in neutral. The experimental lipophilic values logDO/B (1.83 and 2.36 at buffer solution pH 2.0 and 7.4, respectively) were shown the excellent penetration power into both the circulatory system and the entire intestinal tract. The temperature dependences of the CVD distribution coefficients in 1-octanol/buffer and hexane/buffer two-phase systems at pH two values (2.0 and 7.4) were considered from the thermodynamic view point. Thermodynamic functions of solubility and transfer processes were calculated and analyzed. Thermophysical parameters of the compound were used for estimation of the ideal solubility and activity coefficients. Moreover partial excess thermodynamic functions of CVD dissolution in saturated solutions, demonstrating the positive deviation real solvents from ideality, are also evaluated in detail. The data obtained will be in demand both for the creation of conceptually new dosage forms of carvedilol with improved bioavailability, and for constructing structure–property correlations in a number of structure-like compounds.

Stability of Δ<sup>9</sup>- and Δ<sup>8</sup>-tetrahydrocannabinol acetate in e-liquid during storage period (Second report)

We examined the stability of Δ9-tetrahydrocannabinol acetate (Δ9-THC-OAc) and Δ8-tetrahydrocannabinol acetate (Δ8-THC-OAc) in e-liquid products. Eight samples were heated at 30℃ for 28 days and one of them was heated at 70℃ for 2, 4, 8, 10, and 15 days. Residual ratios of Δ9-THC-OAc and Δ8-THC-OAc were evaluated by gas chromatography with flame ion detection and their degradation products were examined by gas chromatography/mass spectrometry (GC/MS). Some samples were tested for solubility in hexane and were submitted to GC/MS analysis to detect propylene glycol and glycerol. After a 28-day incubation at 30℃, Δ9-THC-OAc was slightly decomposed (residual ratio: 84.5–94.2%) but Δ8-THC-OAc was almost stable (residual ratio: 95.2–108.9%). Heating at 70℃ decomposed not only Δ9-THC-OAc but also Δ8-THC-OAc. The decomposition proceeded rapidly in the initial 2 days then slowly until 15 days later. The degradation products, four putative one-oxygen-atom adducts and cannabinol, were detected but deacetylated products (Δ9-tetrahydrocannabinol and Δ8-tetrahydrocannabinol) were not detected. All the samples tested were completely dissolved in hexane differently from propylene glycol and glycerol. Propylene glycol and glycerol were not detected from the samples completely dissolved in hexane. This study indicated that deacetylation of Δ9-THC-OAc and Δ8-THC-OAc did not proceed when the sample did not contain propylene glycol and glycerol.

Continuous separation and recovery of high viscosity oil from oil-in-water emulsion through nondispersive solvent extraction using hydrophobic nanofibrous poly(vinylidene fluoride) membrane

Membrane separation has been considered as a promising technology for oily wastewater treatment. However, membrane fouling significantly limited its practical applications especially for oils with high viscosity and concentration. In this study, we propose membrane based nondispersive solvent extraction for continuous separation and recovery oils with high viscosity and concentration from oil-in-water emulsion. In this process, oil-in-water emulsion and extraction solution (hexane) was separated by a porous hydrophobic poly (vinylidene fluoride) (PVDF) nanofibrous membrane and flowed on each side of the membrane. The strong affinity of PVDF membrane and high solubility of hexane towards oil (e.g., lubricant oil) endowed continuous transfer of oil from emulsion side to hexane side. Different from conventional physical sieving, fouling enhanced transfer of lubricant oil in this process. Lubricant oil flux was up to about 336 g/m2 when 1% lubricant oil-in-water emulsion was used and increased to 935 g/m2 in case of 10%. Moreover, lubricant oil can be easily recovered through hexane evaporation both in low (17oC) and relative high temperature (67oC). Water content of recovered oil (0.10 ± 0.02%) was almost the same as original samples (0.11 ± 0.02%). Strategy proposed in the current study offers an effective way for treating oil-in-water emulsion with high viscosity and concentration.

Extraction of Rice Bran Oil Using CO2-Expanded Hexane in the Two-Phase Region

The performance of CO2-expanded hexane in the vapor-liquid two-phase region was examined to extract phosphorus-free bio-oil from rice bran. Previously, it was found that in the uniform liquid phase region, it is difficult to maintain the phosphorus concentration at a stable and low level when the CO2 mole fraction changed slightly. To overcome this issue, the dependences of the phosphorus and free fatty acid concentrations, the oil solubility, and the oil yield on the CO2 mole fraction in the CO2-expanded hexane were measured at 25 °C, 5.1–5.2 MPa, and at a CO2 mole fraction of 0.88–0.94 in the two-phase region. Thus, a relatively constant phosphorus concentration of <10 ppm was maintained in the extracted oil, which was ~1/50 of that in the oil extracted by hexane, thereby satisfying the European unified standard for biodiesel fuel. Furthermore, a high oil yield exceeding that of hexane extraction was maintained over all CO2 mole fractions. Moreover, the oil solubility in the CO2-expanded hexane decreased linearly with the CO2 mole fraction, and so this factor represented the oil-dissolving power of the extractant more accurately than the oil yield used previously. The free fatty acid concentration was 83% of that extracted by hexane.

Extraction and characterization of Argentine red shrimp (Pleoticus muelleri) phospholipids as raw material for liposome production

Phospholipids rich in omega-3 fatty acids from Argentine red shrimp waste were explored as a source to produce food-grade liposomes. Partially purified phospholipids (PL-AS), hexane-soluble (HxSE) and acetone-soluble (Ac-SE) lipid co-extracts, were characterized in terms of extraction yield (2.0%, 1.46% and 4.51%, respectively), chemical composition (fatty acids, tocopherols, sterols, astaxanthin) and thermal stability. Based on lipid fractionation, PL-AS presented 85% phospholipids, while neutral lipids were mostly present in HxSE (75%) and free FA in AcSE (34%), the latter suggesting significant fat hydrolysis. Palmitic, oleic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids predominated in the phospholipid fraction of PL-AS, mainly constituted by phosphatidylcholine (PC) (96%). The most abundant phospholipid was identified at m/z 760.59, composed of PC, with C16:0/C18:1 as the most probable FA combination. Unilamellar spherical liposomes were successfully made of PL-AS (≈140 nm, 0.248 PDI, −68.5 mV ζ potential), showing high stability for 28 days at 4 °C.

Thermodynamic insight in dissolution, distribution and permeation processes for some benzimidazoles in biologically relevant solvents

Pharmacologically important physicochemical properties were determined for carbendazim, albendazole and fenbendazole. Solubility in buffers (pH 2.0 and pH 7.4), hexane, and octanol was measured by the shake flask method between 293.15 and 313.15 K. All compounds were shown to be poor soluble in pH 7.4 and hexane; better solubility in octanol was revealed. A pronounced effect of pH on the solubility was detected. The Hansen solubility parameters showed the consistency with the experimental data. The thermodynamic functions of dissolution and transfer processes demonstrated low driving forces of the transition of carbendazim from buffer pH 7.4 to hexane and from buffer pH 2.0 to octanol, and albendazole from buffer pH 2.0 to hexane. The distribution of the studied compounds in octanol/buffer pH 2.0 and hexane/buffer pH 2.0 systems demonstrated the compliance with the transferring thermodynamics. Permeability coefficients indicated the influence of molecule charge state and size on the transition through the Permeapad™.

Study of the Molecular-Weight Distribution of Binder Pitches for Carbon Blocks

The present study aimed to identify the required characteristics of binder pitches in the filler-binder mixing process to effectively manufacture graphite blocks. To this end, a binder pitch was separated into pitch fractions of varying molecular-weight segments. The role and effectiveness of each pitch fraction were then analyzed with respect to their molecular-weight distribution. As a result, the optimal molecular-weight distribution was determined. More specifically, a coal-tar pitch was separated into solvent-soluble and solvent-insoluble fractions. The molecular-weight distribution was determined according to this classification, and the characteristics of each pitch fraction were examined. The pitch separation process was conducted using three solvents: hexane, toluene, and quinoline. The resulting pitch was separated into the following pitch fractions: hexane-soluble (HS), hexane-insoluble-toluene-soluble (HI-TS), toluene-insoluble-quinoline-soluble (TI-QS), and quinoline-insoluble (QI). Fourier transform infrared (FT-IR) spectrum, matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), and softening point of each pitch fraction were measured. Also, pitch samples were refabricated while varying the mixing ratio of these pitch fractions, and carbon blocks were then prepared using them. The compressive strength and porosity of these blocks were measured and compared. The P154_B pitch with a high content of TI-QS was used to fabricate a green block. Due to the high viscosity of the binder used, the fluidity was not sufficiently high, and thus, the green block made of this pitch had relatively low strength. The other blocks had similar levels of strength. After the carbonization process, the carbon block with a high content of HS (P352_B-C) and the carbon block with the HS content removed (P073_B-C) showed lower compressive strength than their respective green-block counterparts (P352_B and P073_B). However, their strength was higher compared to those of the other carbon blocks. In the case of carbon block P073_B-C, the HS content was completely removed, and thus, the content of TI-QS (β-resin) was relatively high. Accordingly, this carbon block ended up with large amounts of components that had high coking values (CVs), and this contributed to limiting the formation of pores. Therefore, the compressive strength of this carbon block was high. In the case of the carbon block with a high content of HS (P352_B-C), a suitable level of viscosity was achieved because the HS components ensured high fluidity. As a result, blocks with higher density and compressive strength could be fabricated. The major findings of the present study confirm that producing carbon blocks with high mechanical properties requires binder pitches with a balanced combination of suitable viscosity to ensure sufficiently high fluidity and a proper level of CV to effectively suppress the formation of pores in the mixing and molding process.

New antifungal compound: Solubility thermodynamics and partitioning processes in biologically relevant solvents

A novel potential antifungal compound of 1,2,4-triazole class - ((5Z)-5-[(4-chlorophenyl)methylidene]-3-(2-{4-[2-(2,5-difluorophenyl)-2-hydroxy-3-(1,2,4-triazol-1-yl)propyl]piperazin-1-yl}-2-oxoethyl)-1,3-thiazolidine-2,4-dione) (L-173) - has been synthesized and characterized. Some pharmacologically relevant physicochemical properties have been determined for the first time. Solubility in buffer solutions (pH 1.2, 2.0, and 7.4), ethanol, hexane, and octanol was measured by the shake flask method in the temperature range of 293.15–313.15 K. L-173 was shown to be poor soluble in buffer solutions and hexane, at the same time, better solubility in alcohols was revealed. The Van't Hoff and Apelblat equations gave good correlations when used for modeling the experimental solubility results. The solubility evaluation in different solvents with the help of Hansen solubility parameters and the atomic group contribution approach of Hoftyzer and Van Krevelen showed the consistency with the experimental data and revealed good potential adsorption of the investigated drug. The thermodynamic parameters of solubility and transfer processes were calculated and discussed in view of solute-solvent interactions. The ∆logD parameter determined from the distribution experiment clearly demonstrated the preference of lipophilic delivery pathways for L-173 in the biologic media.

Composition, production, physicochemical properties and applications of lecithin obtained from rice (Oryza sativa L.) - A review

Rice bran oil is a rich source of lecithin and has many beneficial effects on human health. Apart from phospholipids (1-2%), different nutrients like ?-oryzanol, ferulic acid, phytosterols and vitamin B are also present in rice bran oil. These impart emulsifying property, anti-spattering property etc. and therefore, serve as potential nutritional food and nutraceutical. This review describes the composition, production, physicochemical properties, separation of individual phospholipids from rice bran lecithin and its applications in food industry. It is difficult to handle as compared to soyabean lecithin due to the problem of wax entrapment during the isolation of gums. It is characterised on the basis of physicochemical properties viz. solubility in acetone and hexane, colour, peroxide value, moisture content and acid value. Rice bran lecithin can serve as an excellent substitute to the available lecithins as it is non-GM and its nutritional and fatty acid composition imparts many properties which help it to find applications in the food industry. Future work must focus on proper processing of rice bran oil so that the lecithin obtained during processing is of high quality so that it can pave a way in the food sector.

Solubility and vapor pressure data of bioactive 6-(acetylamino)-N-(5-ethyl-1,3,4-thiadiazol-2-yl) hexanamide

This paper presents new experimental data on some key physicochemical properties of original bioactive 6-(acetylamino)-N-(5-ethyl-1,3,4-thiadiazol-2-yl) hexanamide (AETH). Thermal analysis of the compound under study has been carried out using differential scanning calorimetry and thermogravimetric techniques. AETH solubility data in five pharmaceutically relevant solvents in the temperature range from 288.15 to 318.15 K have been obtained by the classic saturation shake-flask method. The bioactive compound has poor solubility in hexane and buffer solutions, while it is slightly soluble in selected alcohols. The experimental solubility results have been correlated by means of modified Apelblat and van’t Hoff equations. The selected thermodynamic models produced acceptable results. The Hansen solubility parameters and their components for AETH and solvents have been evaluated by using the van Krevelen–Hoftyzer atomic group contribution method. The ideal solubility and the solution activity coefficient at equilibrium in the selected solvents have been quantified based on experimental values of melting enthalpy and temperature. All the investigated solutions exhibit a positive deviation from ideality with the maximal solubility in alcohols. The equilibrium vapor pressure of the compound studied has been determined as a function of temperature in the range of 433.15–454.15 K by the transpiration method. The standard thermodynamic parameters of AETH sublimation have been calculated. It has been concluded that the high crystal lattice energy value equal to 131.5 kJ/mol is the dominant factor determining the poor solubility of the bioactive compound.

Effectivity of Phenol during Solvent Extraction of a South African Bituminous Coal under Mild Conditions

Solvent extraction of a South African bituminous coal was carried out under mild conditions (<400 °C) with a holding time of 20 min and an initial nitrogen (N2) pressure of 6 MPa. Thermal degradation of coal with phenol results in the depolymerization of the coal, yielding coal-derived liquids and insoluble residues. The effectiveness of phenol for solvent extraction of coal within the temperature range of 300–360 °C was investigated, with a focus on the quality of the coal-derived liquids. It was found that an increase in temperature from 300 °C to 360 °C resulted in an increase in the conversion and yields of both oil and gas, and a reduction in the intermediate components (preasphaltenes + asphaltenes, PAAs). The conversion and extraction yields of hexane-soluble (HS) oils were 49.5% (daf) and 26.3% (daf), respectively (daf = dry ash-free), for thermal depolymerization reactions at 360 °C. It seems that the extraction process dissolves molecular fragments of the coal, because the infrared spectra of the coal and the extraction products are similar. The SimDis results of the coal-derived liquids (300–360 °C) indicated that the samples consisted of light vacuum gas oil (23–31 wt %), distillate fuel oil (16–30 wt %), heavy vacuum gas oil (18–34 wt %), and residual oil (3–16 wt %). These results show the potential of phenol as a solvent to extract South African bituminous coal at mild temperatures for value-added liquid fuels and add to the general knowledge of the potential utilization of the Permian-aged South African bituminous coals.

Solubility and distribution of bicycle derivatives of 1,3-selenazine in pharmaceutically relevant media by saturation shake-flask method

Three biologically active selenium bicyclic compounds – N-aryl-(3-seleno-azabicyclo[3.3.1]non-2-ylidene)amines were synthesized. The effect of the substances structure on their protolytic properties was investigated. The substance solubility in hexane and pharmaceutically relevant buffer solutions (pH 2.0 and pH 7.4) was measured in the temperature range of 293.15–313.15K by the saturation shake-flask method. Temperature dependences of the distribution coefficients of the compounds in the two-phase systems “organic solvent (octanol, hexane)/buffer solution” were obtained. Thermodynamic parameters of distribution process were calculated.

Physico-chemical characterization antituberculosis thioacetazone: Vapor pressure, solubility and lipophilicity

Vapor pressure of thioacetazone (TAZ) has been determined in the temperature range of 404.15–429.15K by the transpiration method. The obtained data were used to calculate the standard molar enthalpy of sublimation that was found to be 164.1kJ/mol at T=298.15K. The drug solubility was measured at seven temperatures from 288.15 to 318.15K in modeling solvents: octanol, hexane and aqueous buffers pH 2.0 and 7.4 by the saturation shake-flask method by using spectrophotometric analysis. It has been found that TAZ has poor solubility in hexane and buffer solutions and limited solubility in octanol. The experimental data were well correlated by van’t Hoff and modified Apelblat equations. A temperature dependence of TAZ partition coefficient in the octanol/buffer pH 7.4 system has been derived. The partition coefficient value in this system (logP=1.82) refers to the optimal interval for oral absorption drugs. The thermodynamic parameters of sublimation, solubility, solvation and transfer have been determined based on experimental data. The dominant effect of enthalpy and entropy contributions to the Gibbs energy of the investigated processes has been revealed.

Influence of Nonionic Surfactants on Fungal and Bacterial Degradation of Hexane

Batch solubility and microcosm studies were conducted to examine the role of nonionic surfactants (Brij 30, Brij 35, Triton X‐100, and Tween 80) on fungal and bacterial degradation of hexane, a model volatile organic compound with a high Henry's law constant. The apparent solubility of gas phase hexane was not observed as a linear correlation in respect to surfactant concentration due to the insufficient mass transfer at the gas–liquid interface. The hexane partitioning to micellar phase was related to the unique structure of surfactants with different lengths of hydrophobic alkyl or hydrophilic polyoxyethylene chains. Microcosm test results revealed that most tested surfactants below critical micelle concentration (CMC) improved the fungal and bacterial growth, but surfactants at high concentration (5 CMC) adversely affected biodegradation kinetics. The observed low hexane removal was possibly attributed to the toxicity of surfactants at elevated concentration, the preferential utilization of a surfactant as substrate, and the partitioning of hexane into micellar phase. The results from this study suggest that low concentrations of Brij 30 and Tween 80 are favorable to enhance both the solubility and bioavailability of hexane with fungi as working consortium, while Brij 30 and Triton X‐100 below their CMC hold promising potential for bacterial degradation of hexane without having significant biodegradation of the surfactant.

Solubility of Hexane in Aqueous Solutions of Methyldiethanolamine

This paper presents new experimental solubility data of hexane in aqueous amine solutions. A set of simple thermodynamics equilibrium cells were used to measure the solubility of hydrocarbons in aqueous amine systems in the range 298 K to 333 K. Analyses of aqueous liquid samples are performed using a gas chromatograph. It was observed that hexane solubility in methyldiethanolamine (MDEA) solutions increased with increasing temperature. Also, increasing amine concentration in the test solution increased the solubility of hexane. A simple model is developed in order to represent the activity coefficient of hexane in the aqueous MDEA solution in the range of 40 wt % to 50 wt % MDEA.

Diffusion of di(2-ethylhexyl)phthalate in PVC quantified by ATR-IR spectroscopy

Di(2-ethylhexyl) phthalate (DEHP) is a commonly employed plasticizer for poly(vinyl chloride) (PVC). Diffusion of di(2-ethylhexyl) phthalate (DEHP) takes place when plasticized PVC is immersed in hexane. Rather than determining DEHP concentration in the immersion solvent, an IR window for PVC from 1500 to 1900 cm−1 enabled direct measurement of HADD (hexane assisted DEHP diffusion) using ATR-IR by monitoring the DEHP carbonyl absorption at 1715 cm−1. The present study employed PVC containing 45% plasticizer (PVC-45, tygon tubing). A fast diffusion process was observed for short times (<30 s) while a slower diffusion process occurred at longer immersion times (30 s < t < 6 min). A synergistic increase in mesosurface Tg toward that of PVC coupled with low solubility of hexane in PVC accounts for decreased DEHP diffusion rates (10−12–10−13 cm2 s−1) for immersion times > 30 s. Analysis by XPS shows the outermost surface is PVC free of plasticizer after 6 min immersion. After an induction period, back diffusion coefficients Db were estimated from peak areas during a subsequent fast recovery period (10−14–10−15 cm2 sec−1). A model is proposed for the induction period associated with re-plasticization that involves a change from a mesosurface glass to a gel like solid.

Dissociation Constants and Solubilities of Dalbergin and Nordalbergin in Different Solvents

The dissociation constants (pKa) of dalbergin and nordalbergin were measured at 298.2 K using ultraviolet (UV) spectroscopy method. The solubilities of dalbergin and nordalbergin in water, methanol, propanone, ethyl ethanoate, trichloromethane, and hexane have been determined by the UV spectrophotometric method from 283.2 to 308.2 K at atmospheric pressure. The experimental solubility values were correlated with a modified Apelblat equation, λh model, and ideal model. The pKa value of dalbergin is 8.91 ± 0.12, and the pKa1 and pKa2 values of nordalbergin are 7.31 ± 0.29 and 9.79 ± 0.39, respectively. The solubilities of dalbergin and nordalbergin in six solvents increase with an increase in temperature. The solubility order of dalbergin in six pure solvents was trichloromethane > propanone > ethyl ethanoate > methanol > hexane > water, whereas that of nordalbergin was propanone > methanol > ethyl ethanoate > trichloromethane > water > hexane. A comparison of the solubility of dalbergin with that of nordalbergin shows that the 7-methoxyl moiety of dalbergin leads to a significantly higher solubility in trichloromethane and hexane, a little higher solubility in ethyl ethanoate, an approximately equal solubility in propanone, and a little lower solubility in methanol and water (exception 283.2 K). For dalbergin, the modified Apelblat equation shows the best correlation for all solvents, and for nordalbergin, correlation results by three models are similar.

Coating of graphite anode with coal tar pitch as an effective precursor for enhancing the rate performance in Li-ion batteries: Effects of composition and softening points of coal tar pitch

Effects of compositions and softening points of coal tar pitches (CTPs) on the electrochemical performances especially for first cycle Coulombic efficiency and rate performance, of the amorphous carbon coating on the graphite surface were closely examined. CTPs with higher softening points could afford the better homogeneous amorphous carbon coating on the graphite surface, resulting in the better enhancing rate performance of graphite anode without decreasing the first cycle Coulombic efficiency. CTP with almost complete absence of hexane soluble (HS) fraction always showed the good enhancing effect of the rate performance. HS fraction of CTP, which is a reason for inducing surface defects on the coated carbon, hindered the enhancing effect of electrochemical performances. CTP derived amorphous carbon coating could effectively decrease charge transfer resistance on the graphite electrode–electrolyte interface.

Hydrovisbreaking of vacuum residue from Russian Export Blend: influence of brown coal, light cycle oil, or naphtha addition

AbstractDemand for high-value petroleum products is increasing and crude oils and their distillation products are becoming heavier. The thermal cracking of a vacuum residue (VR) from REB (Russian Export Blend) crude oil was carried out in an autoclave. LCO (light cycle oil), naphtha, and brown coal (BC) were added with the aim of studying their effect on the final products composition. The elemental analysis (%C, %N, %H, %S) was performed and dynamic viscosity, density, GC of gases (“Refinery Gas Analysis”), solubility in hexane and toluene, and simulated distillation were examined in raw materials, gaseous, and liquid products. As anticipated, due to its high aromatics content, the addition of LCO proved the best option, obtaining the highest yield of lighter liquids. The naphtha addition resulted in a slight increment of heavier products in the gaseous phase and higher yields to solids. The literature does not contain any extensive studies of the addition of BC to VR in the hydrovisbreaking process. The addition of BC resulted in an increment in the yield of the gaseous product and assumed the highest relative total consumption of hydrogen during the reaction.

Facile synthesis of a genuinely alkane-soluble but isolable lithium hydride transfer reagent.

1-Lithio-2-butyl-1,2-dihydropyridines, typically formed as intermediates in the nucleophilic substitution (addition/elimination) of pyridine with (n- or t-)butyl lithium, have been isolated and comprehensively characterized. The linear substituted isomer is polymeric while the branched substituted isomer is a cyclotrimer. The lower oligomerization of the latter complex confers exceptional hexane solubility making it an excellent lithium hydride source in non-polar, aliphatic media. A Me6TREN stabilized monomer of the t-butyl complex represents the first 1,2-dihydropyridyllithium complex to be characterized crystallographically.