Methanol-water System Research Articles

Characterization of a well-resolved acyclic methanol(water)5 heterohexamer in the solid state

Abstract A novel (CH3OH)(H2O)5 binary cluster is trapped in a photoluminescent silver(I) coordination polymeric host, [Ag2(bpp)2(H2O)(ssa)·4H2O·CH3OH]n (1, bpp = 1,3-bis(4-pyridyl)propane, H2ssa = 5-sulfosalicylic acid). The heterohexamer can be viewed as either a D5 water pentamer with a dangling methanol molecule or a combination of D4 tetrameric water and methanol–water heterodimer. This well-resolved heterohexamer may behave as a useful model helping us to further understand phase behavior of binary methanol–water system. The luminescent behavior of 1 was also discussed.

Organic Salt Effect of Tetramethylammonium Bicarbonate on the Vapor–Liquid Equilibrium of the Methanol–Water System

The effect of organic salt tetramethylammonium bicarbonate (TMAC) at salt mole fractions from 0 to 0.159 on the vapor–liquid equilibrium (VLE) of the binary methanol–water system has been experimentally investigated at 101.32 kPa using a modified Rose equilibrium still. The experimental data were correlated by Ohe's preferential solvation model and the Tan–Wilson model, and the average deviations of the vapor-phase mole fraction of this salt-containing methanol–water system are 0.011 and 0.017, respectively. The average deviations of temperature are 1.24 K for Tan's model.

A Hand‐held Fiber‐optic Implement for the Site‐specific Delivery of Photosensitizer and Singlet Oxygen

We have constructed a fiber optic device that internally flows triplet oxygen and externally produces singlet oxygen, causing a reaction at the (Z)-1,2-dialkoxyethene spacer group, freeing a pheophorbide sensitizer upon the fragmentation of a reactive dioxetane intermediate. The device can be operated and sensitizer photorelease observed using absorption and fluorescence spectroscopy. We demonstrate the preference of sensitizer photorelease when the probe tip is in contact with octanol or lipophilic media. A first-order photocleavage rate constant of 1.13 h(-1) was measured in octanol where dye desorption was not accompanied by readsorption. When the probe tip contacts aqueous solution, the photorelease was inefficient because most of the dye adsorbed on the probe tip, even after the covalent ethene spacer bonds have been broken. The observed stability of the free sensitizer in lipophilic media is reasonable even though it is a pyropheophorbide-a derivative that carries a p-formylbenzylic alcohol substituent at the carboxylic acid group. In octanol or lipid systems, we found that the dye was not susceptible to hydrolysis to pyropheophorbide-a, otherwise a pH effect was observed in a binary methanol-water system (9:1) at pH below 2 or above 8.

Synthesis of Y2O3:Eu phosphor with various particles morphologies by solvothermal reaction in methanol-water system

A methanol–water mixed solvent was used as a reaction medium for the synthesis of Eu3+-doped Y2O3 (Y2O3:Eu) phosphor. Y2O3:Eu was prepared under solvothermal conditions at 150–300°C for 3–24 h using a solution of water and methanol as the reaction medium followed by heat treatment at 1000°C for 2 h. The phase composition and optical properties of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence spectroscopy. The powders obtained were composed of plate-like particles, spindle-like particles, and whisker particles and were different for samples prepared under supercritical, subcritical, and normal conditions of methanol. With the reaction temperature increasing, the particle size became smaller, in particular, the particles were ∼500 nm in size at 300°C under supercritical condition of methanol. After calcination at 1000°C for 2 h, the obtained powders retained the initial shape. The emission peaks of the fluorescence were assigned to the f–f transitions of the Eu3+ and exhibited red emission. The fluorescence intensities and internal quantum efficiency exhibited various values dependence on the morphology of the obtained particles.

Novel molecularly imprinted polymer using 1-(α-methyl acrylate)-3-methylimidazolium bromide as functional monomer for simultaneous extraction and determination of water-soluble acid dyes in wastewater and soft drink by solid phase extraction and high performance liquid chromatography

Novel water-compatible molecularly imprinted polymers were synthesized in methanol–water systems with Tratarzine as template and 1-(α-methyl acrylate)-3-methylimidazolium bromide (1-MA-3MI-Br) as functional monomer, which has π–π hydrophobic, hydrogen-bonding and electrostatic interactions with template molecule. 1-MA-3MI-Br molecularly imprinted polymers (1-MA-3MI-Br-MIPs) were used as selective sorbents for the solid-phase extraction (SPE) of water-soluble acid dyes from wastewater and soft drink. The good linearity of the method was obtained in a range of 5.0–2000 μg/L with the correlation coefficient of >0.999. The detection limits were in a range of 0.13–0.51 μg/L for the water-soluble acid dyes in wastewater and 0.095–0.84 μg/L for those in soft drink. The mean recoveries for the acid dyes are from 89.1% to 101.0% in spiked wastewater and 91.0–101.3% in spiked soft drink. Compared with strongly anion exchange solid phase extraction (SAX-SPE), mixture anion exchange solid phase extraction (MAX-SPE), and 1-MA-3MI-Br non-imprinted solid phase extraction (1-MA-3MI-Br-NISPE), almost all of the matrix interferences were removed by 1-MA-3MI-Br-MISPE, exhibiting higher selectivity, recovery and enrichment ability for the acid dyes and better baselines in the results of HPLC analysis.

THE ROLE OF METHANOL IN THE CRYSTALLIZATION OF TITAN'S PRIMORDIAL OCEAN

A key parameter that controls the crystallization of primordial oceans in large icy moons is the presence of anti-freeze compounds, which may have maintained primordial oceans over the age of the solar system. Here we investigate the influence of methanol, a possible anti-freeze candidate, on the crystallization of Titan's primordial ocean. Using a thermodynamic model of the solar nebula and assuming a plausible composition of its initial gas phase, we first calculate the condensation sequence of ices in Saturn's feeding zone, and show that in Titan's building blocks methanol can have a mass fraction of ∼4 wt% relative to water, i.e., methanol can be up to four times more abundant than ammonia. We then combine available data on the phase diagram of the water–methanol system and scaling laws derived from thermal convection to estimate the influence of methanol on the dynamics of the outer ice I shell and on the heat transfer through this layer. For a fraction of methanol consistent with the building blocks composition we determined, the vigor of convection in the ice I shell is strongly reduced. The effect of 5 wt% methanol is equivalent to that of 3 wt% ammonia. Thus, if methanol is present in the primordial ocean of Titan, the crystallization may stop, and a sub-surface ocean may be maintained between the ice I and high-pressure ice layers. A preliminary estimate indicates that the presence of 4 wt% methanol and 1 wt% ammonia may result in an ocean of thickness at least 90 km.

ACE applied to the quantitative characterization of benzo‐18‐crown‐6‐ether binding with alkali metal ions in a methanol–water solvent system

ACE was applied to the quantitative evaluation of noncovalent binding interactions between benzo-18-crown-6-ether (B18C6) and several alkali metal ions, Li(+), Na(+), K(+), Rb(+) and Cs(+), in a mixed binary solvent system, methanol-water (50/50 v/v). The apparent binding (stability) constants (K(b)) of B18C6-alkali metal ion complexes in the hydro-organic medium above were determined from the dependence of the effective electrophoretic mobility of B18C6 on the concentration of alkali metal ions in the BGE using a nonlinear regression analysis. Before regression analysis, the mobilities measured by ACE at ambient temperature and variable ionic strength of the BGE were corrected by a new procedure to the reference temperature, 25 degrees C, and the constant ionic strength, 10 mM. In the 50% v/v methanol-water solvent system, like in pure methanol, B18C6 formed the strongest complex with potassium ion (log K(b)=2.89+/-0.17), the weakest complex with cesium ion (log K(b)=2.04+/-0.20), and no complexation was observed between B18C6 and the lithium ion. In the mixed methanol-water solvent system, the binding constants of the complexes above were found to be about two orders lower than in methanol and about one order higher than in water.

Synthesis of Readily Accessible BODIPY-Based Fluorescence Derivatization Reagents for Amines

Two BODIPY-based fluorescence derivatization reagents (FDRs) for amines were synthesized in a simple manner with practically acceptable yields via five steps. Both FDRs showed prompt reactivity, even against sterically hindered amines, to afford the corresponding FDR-labeled products in good yields. The solvent effect upon the fluorescence intensity of the derivatized amine was also investigated in a methanol-water binary solvent system to demonstrate that the strong fluorescence intensity was maintained in the solvent with a 0-60% water ratio. The detection limits of the new FDRs were estimated to be 20 fmol, which makes it much more sensitive than commercially available FDRs.

Dual-inlet micro-calorimeter for bio-chemical studies of microliter liquid samples

We present a fluidic micro-calorimeter that shows high versatility measuring both thermal properties of samples and enthalpies of bio-chemical processes. The micro-calorimeter consists of two stacked chips with silicon nitride membranes that define the liquid chamber of 2.6 μl. The chamber has two inlets which allow real time reactions monitoring. We measured the thermal conductivity and diffusivity of water-methanol solutions with 1% resolution, and we determined the mixing enthalpy for watermethanol system with a signal/noise ratio of 20.

Synthesis and characterization of mono-dispersed mesoporous spheres

In the presence of a high TMOS concentration, mono-dispersed mesoporous pure silica spheres with different pore sizes were successfully synthesized using C16TMACl, C14TMACl, and C12TMACl as templates in a methanol–water system, whereas they could not be obtained using C10TMACl. The standard deviation of the particle size prepared with high TMOS concentrations was approximately 10%. Mono-dispersed mesoporous Al-containing spheres could also be synthesized using NaAlO2 as an aluminum source from starting synthesis mixtures with a TMOS/Al ratio of more than 10, but not with a TMOS/Al ratio of less than 8. It was found that the particle size and standard deviation of mono-dispersed mesoporous aluminum-containing spheres depended on the TMOS/Al ratio.

Synthesis of new binary cobalt iron pyrophosphate CoFeP 2O 7

A new binary cobalt iron pyrophosphate, CoFeP 2O 7 was synthesized through solid phase reaction using cobalt carbonate, iron metal and phosphoric acid in the presence of water–methanol system with further calcinations at the temperature of 500 °C. The particle size obtained from X-ray line broadening is 36 ± 7 nm for the CoFeP 2O 7. FTIR spectrum of CoFeP 2O 7 is assigned based on the P 2O 7 4− ion in the structure. The XRD, UV–Vis near IR and FTIR results of the synthesized CoFeP 2O 7 appear to be very similar to that of M 2P 2O 7 (M = Fe and Co), which indicates the monoclinic phase with space group C2/m.

Effect of concentration of methanol for the control of particle size and size-dependent SERS studies

In this paper the effect of concentration of cosolvent (methanol) for the formulation of particles size has been discussed briefly. The binary solvent system has been used which is prepared by simple mixing of two solvents. The morphology of the particles was controlled by varying the amount of cosolvent, keeping the concentration of the stabilizer and reducing agent constant. The polarity of the solvent, transport of the Au(III) ions, and coordinating ability of the solvent play vital roles for nucleus formation and the growth process, which subsequently form different size particles. The particles formed in methanol at lower composition are angular. At higher concentrations of methanol they are spherical. In all the cases the particle size increases as the concentration of the cosolvent decreases. In the methanol system, particles form multiple twined structures and the twining of the particles increase with the decrease of methanol content. The particles have been characterized by XRD analysis, UV–visible spectroscopy, and transmission electron microscopic (TEM) studies. The variable size of the particles, obtained in a water methanol system, was employed for SERS measurement. A Raman probe, Rhodamine 6G (Rh 6G), has been found to be suited for the surface modification of the gold particles and it has also been demonstrated that the larger particles show better SERS signal than the corresponding smaller ones.

Determination of asiatic acid in beagle dog plasma after oral administration of Centella asiatica extract by precolumn derivatization RP-HPLC

A novel precolumn derivatization reversed-phase high-performance liquid chromatography (RP-HPLC) method with UV–vis detection for the quantitative determination of total concentration of asiatic acid (AA) in beagle dog plasma is described. AA was extracted with n-hexane-dichloromethane-2-propanol (20:10:1, v/v/v) from plasma, which had been hydrolyzed by acid and derivatized with p-Toluidine. Chromatographic separation was achieved on a C 18 column using gradient elution in a water–methanol system. Detection was set at UV wavelength of 248 nm. A calibration curve ranging from 0.01 to 1.5 μg/mL was shown to be linear, and the lower limit of quantification (LLOQ) was 0.01 μg/mL. The intra- and inter-day precisions which were determined by three different concentrations (0.05, 0.2 and 0.8 μg/mL) ranged from 4.4% to 13.1% and 4.6% to 14.2%, respectively. Mean extraction recoveries were no less than 65% for AA and ursolic acid (IS). Plasma samples containing asiatic acid were stable for 30 days at −20 °C. The method was successfully applied to a pharmacokinetic study in beagle dogs after oral administration of Centella asiatica extract, and the main pharmacokinetic parameters obtained were: T 1/2, 4.29 h; T max, 2.70 h; C max, 0.74 μg/mL; AUC 0– t and AUC 0–∞, 3.74 and 3.82 μg h/mL, respectively.

Analytical procedure to simultaneously measure trace amounts of trenbolone acetate and β‐trenbolone residues in porcine muscle using HPLC‐UVD and MS

The current study was undertaken to validate the performance for the determination of both TBA and beta-trenbolone (beta-TB) residues in porcine muscle at concentrations required to monitor compliance with the maximum residue limit (MRL). The method involves a one phase liquid-liquid extraction, cleanup with low-temperature fat precipitation, separation of the respective compounds by HPLC on a Capcell pak C(18) column, use of a methanol-water isocratic system as an eluent, and measurement by UV absorbance detection at 340 nm. Both compounds were confirmed using LC-MS/MS with electrospray interface (ESI) and a triple quadrupole (QqQ) analyzer. The method was found to be precise and accurate, with a linearity range of 1-10 microg/kg (r(2) >0.973). The intra- and interday precision showed good reproducibility with RSDs < or =13.25%. The LODs were 0.12 and 0.22 microg/kg, and the LOQs were 0.37 and 0.66 microg/kg, for TBA and beta-TB, respectively. The applicability of the method was demonstrated by analyzing real samples collected from major cities in the Republic of Korea. No residues of the selected compounds were detected in any of the samples. The advantages of our method are that it is: selective, sensitive, requires a short time for analysis (13 min), and performs simple sample extraction and clean-up procedure with low-temperature fat precipitation as compared to the previously published methods.

Recognition mechanism of water-compatible molecularly imprinted solid-phase extraction and determination of nine quinolones in urine by high performance liquid chromatography

Novel water-compatible molecularly imprinted polymers (MIPs) were synthesized in methanol–water systems with ofloxacin as templates and methacryclic acid as functional monomers. The MIPs were used as a special sorbent for the selective solid-phase extraction (SPE) of nine quinolones from urine samples, showing high affinity to the quinolones in aqueous environment. Its molecular recognition mechanisms were investigated by the molecular simulation and the experimental validation with UV and infrared spectrogram as well as 1H NMR. Binding capability and chromatographic characteristic were also evaluated. By using the water-compatible MIPs as SPE sorbents, the nine quinolones can be selectively extracted and enriched, while all matrices interferences were eliminated simultaneously. Under the optimal conditions of SPE and high performance liquid chromatography (HPLC), the good linearity of the method was obtained in a range of 0.05–30 μg/mL with the correlation coefficient of >0.999 and the relative standard division of 2.0–7.4%. The detection limits (s/n = 3) were in a range of 0.036–0.10 μg/mL. The proposed method was successfully applied for the selective extraction and separation of the studied quinolones in urine samples.

Determination of enrofloxacin and ciprofloxacin in milk using molecularly imprinted solid‐phase extraction

A molecularly imprinted solid-phase extraction procedure was developed for the simultaneous identification of enrofloxacin and its active metabolite, ciprofloxacin, in milk samples. Water-compatible molecularly imprinted polymers synthesized in a water-methanol system show a high degree of cross-reactivity for enrofloxacin and ciprofloxacin in aqueous environments. The imprinted particles were applied as selective sorbents in a solid-phase extraction process focusing upon complex milk matrices, which allowed the matrix compounds present in milk samples to be removed effectively. The extracts were sufficiently clean for further chromatographic analysis, and no interference originating from the biological matrix was observed. The mean recoveries of enrofloxacin and ciprofloxacin from milk sample were 82.6-93.5% and 81.2-94.8%, respectively, with the RSD less than 7.5%. This method is simple and sensitive, and is therefore an alternative tool to the existing HPLC methods for analyzing residual enrofloxacin and ciprofloxacin in biological samples.

Simultaneous isolation of six fluoroquinolones in serum samples by selective molecularly imprinted matrix solid-phase dispersion

A simple and sensitive method for the simultaneous determination of six fluoroquinolones from serum samples was developed by selective molecularly imprinted matrix solid-phase dispersion (MI-MSPD) coupled with chromatographic separation. By using ethylene glycol dimethacrylate as crosslinker and reformative methanol–water system as reaction medium, the improved water-compatible imprinted polymers were synthesized which show higher affinity to template and its analogues in aqueous environment. The molecularly imprinted polymers (MIPs) were applied as the selective dispersant of matrix solid-phase dispersion (MSPD) could selectively extracted the six fluoroquinolones from serum, while interferences originated from serum matrices were eliminated simultaneously. Good linearity was obtained in a range of 0.05–100 μg mL −1 with the correlation coefficients >0.999. The average recoveries of the six fluoroquinolones at four different spiked levels (0.25–10 μg mL −1) were ranged from 72.2% to 114.1% with the relative standard deviations less than 6.6%. This method is simple and sensitive, and can be used as an alternative tool to the existing HPLC methods for analyzing the residues of fluoroquinolones in biological samples.

PHEMA Hydrogels Modified through the Grafting of Phosphate Groups by ATRP Support the Attachment and Growth of Human Corneal Epithelial Cells

Converting the surface of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel into a cell-adhesive surface has been successfully achieved through a method based on atom transfer radical polymerization (ATRP) grafting. Following activation of the surface hydroxyl groups of PHEMA by bromination, surface-initiated ATRP of mono(2-methacryloyloxyethyl) phosphate (MMEP) was conducted in a methanol-water system with Cu(I)Br as catalyst at room temperature. The conversion of PHEMA hydroxyl groups to brominated isobutyryl groups and the occurrence of grafting of PMMEP were confirmed by infrared and X-ray photoelectron spectroscopies. Cell attachment experiments were conducted by culturing human corneal limbal epithelial cells on the PMMEP-grafted PHEMA, and on unmodified PHEMA and tissue culture plastic for comparison. The results showed that the grafted PMMEP was homogeneously distributed, and the phosphate groups appeared to significantly promote the attachment, spreading and growth of cells, at a level comparable to the tissue culture plastic.

Tocols in caneberry seed oils

The compositional analysis of tocols in oils extracted from Korean caneberry seeds was compared with commercial soybean, corn, olive, canola, perilla, and grape seed oils. The oils from caneberry seeds of six different species were extracted using either a chloroform–methanol–water system or hot hexane. Tocols from all of the oils were analysed using isocratic HPLC. The contents of total tocopherols in the caneberry seed oils were about 75–290 mg/100 g oil, whereas tocotrienols were not detected. γ-Tocopherol was the most abundant tocopherol (31.8–239 mg/100 g oil) in the caneberry seed oils, followed by α-tocopherol (7.6–58.2 mg/100 g oil). The contents of total tocols in soybean, corn, olive, canola, perilla, and grape seed oils were 99.9, 61.1, 28, 27, 45.4, and 52.2 mg/100 g oil, respectively. Total tocol content was higher in most of the caneberry seed oils including the refined ones than in the commercial vegetable oils.

Methylation in methanol–water mixtures: The effect of solvent composition and high pressure

The effect of pressure (0.1 to 400 MPa) and solvent composition (methanol concentration of 5 to 30%) on the synthesis of β-methylgalactoside was studied. Galactose was used as a reactant and the reaction was catalyzed by β-galactosidase from Aspergillus oryzae. Under the applied conditions the enzyme was sufficiently stable and the reaction equilibrium was reached. Higher methanol concentrations obviously influenced the product yield positively due to an increase in reactant concentration but also due to a solvent effect. This solvent effect can be explained by measurement of the activities of galactose and methylgalactoside. These results may be generalized to other methylations in methanol–water systems, where methanol positively affects synthesis yields. Pressure had a small, negative effect on synthesis yields.