Methanol-water Solvent System Research Articles

Synthesis of pyridinium-based ionic liquids and their application to improve Candida rugosa lipase stability in a methanol-water solvent system.

This paper studied the effect of pyridinium-based ionic liquids as cosolvents in a methanol-water solvent system on the hydrolytic activity of Candida rugosa lipase. These ionic liquids were successfully synthesized using imidazolium-based ionic liquid synthesizing methods with a certain adjustment. The hydrolytic activity of Candida rugosa lipase was analyzed using 4-nitrophenol acetate (pNPA) and 4-nitrophenol palmitate (pNPP) as substrates. The addition of ionic liquids had no significant effect on the hydrolytic activity of lipase in a water solvent, and it had a greater effect in methanol. The addition of [C6Py] Br ionic liquid as a methanol cosolvent (methanol: ionic liquid, 10:5) could increase the hydrolytic activity of lipase. The use of ionic liquid as a cosolvent could increase the hydrolytic activity of lipase by about 15.61% while using pNPP as a substrate in the methanol system. A molecular dynamics study for the interaction between lipase and ionic liquids supported the experimental results. The ionic liquid using bromide as an anion provided more stability on lipase conformation. It tends to form the short-range interaction between the lipase and bromide anion.

Saponins from Albizia procera extract: Surfactant activity and preliminary analysis

We report our results on surface activity and preliminary analytical data of natural surfactant (saponin) from Albizia procera extract. The plant-based extract exhibited moderate reduction of surface tension, low alkalinity, moderate foaming and emulsifying characteristics. The critical micelle concentration is 7.00 × 10−3 g/cc, where the emulsifying power reached a maximum. An abrupt increase in viscosity and conductivity with surfactant concentration was seen in this region. Dirt dispersion results displayed a sharp maximum at the Critical Micelle Concentration. The extracts were analyzed to understand the constituents. The presence of polar and non-polar compounds was seen in Thin Layer Chromatography analysis. Using methanol water solvent system, a good separation of compounds was observed in High Performance Liquid Chromatography. The presence of saponin along with some traces of flavonoids was observed by UV-Visible spectroscopy. Occurrence of triterpenoid saponins were indicated by Fourier Transform Infrared spectroscopy analysis. The results obtained from surface tension, foaming and emulsification highlights the efficiency of Albizia procera extract to be employed as a possible environment friendly surface-active agent. This natural surfactant could find various industrial and domestic applications.

Parametric study on the mixed solvent synthesis of ZIF-8 nano- and micro-particles for CO adsorption: A response surface study

The room temperature synthesis of ZIF-8 micro- and nano-particles was investigated using a mixed methanol-water solvent system. ZIF-8 particles of good quality and high crystallinity were obtained. Response surface methodology was used to determine the effect of the synthesis conditions on the ZIF-8 yield, particle size distribution, and mean particle size. The ligand/metal salt molar ratio followed by the amount of sodium formate (the deprotonating agent) and then the amount of water (i.e., the composition of the mixed solvent) respectively had the largest effects on both the ZIF-8 yield and particle size. Results showed that mixing of solvents with different strengths in producing ZIF-8 crystals is a practical method to size-controlled synthesis of ZIF-8 particles. This method is more favorable for industrial-scale ZIF-8 synthesis than using excess amounts of ligands or chemical additives (like sodium formate). In addition, ZIF-8 samples with different mean particle sizes (100, 500, and 1000 nm) were used for CO adsorption and the mid-sized ZIF-8 particles had the highest adsorption capacity.

Monitoring the antioxidant activities by extracting the polyphenolic contents of algae collected from the Bosphorus

The identification and quantification of ascorbic acid, phenolic acids and flavonoids were carried out simultaneously with a rapid method of reverse-phase high-performance liquid chromatography (RP-HPLC). Total flavonoid contents were being determined by UV–Vis spectrophotometry, and total phenolic contents were determined by UV–Vis spectrophotometry using the Folin-Ciocalteu Reagent (FCR) method.In all of the individual contents and total phenolic content analysis, the best results were obtained with the methanol-water solvent system. The methanol-hexane solvent system was selected as the best for the extraction of total flavonoid contents. The reason for this difference is the flavonoids in the analyzed samples which were the lipophilic character. Examining the algae species, the highest contents were achieved from Ulva lactuca and Ceramium rubrum species. Depending on industrial activity and the population density, regional characteristics have been shown to be effective in the changes of these contents which show antioxidant properties.

Electrospun and functionalized PVDF/PAN composite for the removal of trace metals in contaminated water

The electrospinning of a nanofiber composite of polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) in a dimethylformamide (DMF) solvent was carried out prior to functionalization by free radical grafting of acrylic acid (AA) brushes. Subsequent application for the removal of Pb2+ and Cd2+ from contaminated water is reported. Free radicals were initiated on the polymeric nanofiber composite using 5% 2,2′-Azobis(2-methylpropionitrile) (AIBN) in acetone. Upon solvent removal by air-drying, AA was added and grafting (in a methanol-water solvent system) was carried out in an oil bath at 70 °C for 5 h under nitrogen atmosphere. Structural and chemical characterization of the composite was done using scanning electron microscope (SEM), nitrogen sorption at 77 K (BET method), goniometer and Fourier transform infrared spectrometer (FTIR), while changes in metal ion concentration during batch adsorption were monitored using inductively coupled plasma optical emission spectrometer (ICP-OES). Through isotherm study, the adsorption was confirmed to follow both Langmuir and Freundlich models whilst adsorption kinetic studies showed that the adsorption rate is of pseudo-second order. In furtherance, the respective values for adsorption capacity and estimated removal efficiency for Pb2+ and Cd2+ were 1.585 and 0.164 mg g−1, 90% and 80% respectively, while a 5% loss in regeneration efficiency after 10 cycles was also observed. Consequently, the nanocomposite was found efficient when applied to the removal of Pb2+ and Cd2+ from contaminated water.

Determination of Steady-State Kinetic Parameters of 1-Deoxy-D-xylulose-5-phosphate Synthase by Pre-column Derivatization High Performance Liquid Chromatography Using 2,4-Dinitrophenylhydrazine as Derivative Reagent

Abstract Carbonyl containing compounds can normally be determined by high performance liquid chromatography (HPLC) through pre-column derivatization with 2,4-dinitrophenylhydrazine (DNPH). Using this method, the steady-state kinetic parameters of 1-deoxy- D -xylulose-5-phosphate synthase (DXS) was measured. First, the enzymatic product 1-deoxy- D -xylulose-5-phosphate (DXP) was dephosphorylated by alkaline phosphatase, then the product 1-deoxy- D -xylulose (DX) was derived with DNPH in acidic solution to give the corresponding hydrazones which was subsequently determined by HPLC. The optimum derivatization conditions are as follows: 1.5% perchloric acid, reaction temperature of 37 °C, reaction time of 60min, molar ratio of DNPH to DXP 6:1. The HPLC was run with a linear gradient of methanol-water solvent system: 0 min, 40% methanol; 17 min, 80% methanol; 18 min, 40% methanol; 20 min, 40% methanol. The method has a detect limit of 1 mg L −1 for DXP and a linear correlation in the range of 0.005–1 g L −1 ( R = 0.999). The relative standard deviation is less than 5.0%. The steady-state kinetic parameters of DXS determined by this method are identical with the reported data.

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.

Micellar Studies of Magnesium Soaps Using Ion-selective Electrode

Abstract Magnesium soaps of caproic and caprylic acids were prepared and a cell was set up for the measurement of EMF (electromotive force) of the cell containing referred soap solutions in methanol water solvent system with the aid of ion-selective electrode. The critical micelle concentration of soap solutions was determined by plotting the electromotive force of the cell against soap concentration. The critical micelle concentration of these soap solutions varies with increase in chain length of the fatty acids in the soap. The energetic studies of the system have been carried out from the electromotive force values of the cell containing soap solution to ascertain the chain length compatibility and agglomeration profile. The values of free energy change are negative indicating the spontaneity of cell reaction and decreases with increasing soap concentration while increases with the increase methanol concentration in solvent mixture.

HSCCC‐MS Study of Flavonoids in the Extracts from the Seeds of Oroxylum indicum

In this study, two analytical high‐speed countercurrent chromatography (HSCCC) instruments, interfaced directly with electrospray ionization and atmospheric pressure chemical ionization mass spectrometry, were explored for the separation of a mixture of three standard flavonoids. Hexane–ethyl acetate–methanol–water solvent systems with different ratios were chosen and optimized for the best separation. On‐line HSCCC‐MS was successfully used in the identification of flavonoids from an ethyl acetate extract of the seeds of Oroxylum indicum.

An efficient method for the purification and characterization of nematicidal azadirachtins A, B, and H, using MPLC and ESIMS.

Azadirachtin A enriched concentrate containing 60% active ingredient (a.i.) was prepared from the methanolic extract of the de-fatted neem (Azadirachta indica A. Juss) seed kernels. Azadirachtins A, B, and H, the three major bioactive constituents of neem seed kernel, were purified from this methanolic concentrate by employing reverse phase medium-pressure liquid chromatography (MPLC), using methanol-water solvent system as an eluant. The three pure azadirachtin congeners thus obtained were characterized by their unique mass spectral fragmentation, using electrospray probe in positive ion mode (ESI). All three azadirachtins exhibited nematicidal and antifungal activities. Azadirachtin B was the most effective against the reniform nematode Rotylenchulus reniformis (EC(50) 96.6 ppm), followed by Azadirachtin A (119.1 ppm) and H (141.2 ppm). At 200-ppm concentration, the test compounds caused 50-65% mortality of Caenorhabditis elegans nematode. Azadirachtin H showed the highest activity against the phytophagous fungi Rhizoctonia solani (EC(50) 63.7 ppm) and Sclerotium rolfsii (EC(50) 43.9 ppm), followed by B and A. The isolation of pure azadirachtins A, B, and H directly by MPLC purification from its concentrate and their characterization by ESIMS are unique and less time-consuming.

A Reverse Phase Technique for Separating the Linearc Furano Coumarins in Celery

Abstract A reverse phase method for separating the four linear furanocoumarins psoralen, xanthotoxin, bergapten, and isopimpinellin in celery is described. The photosensitizing compounds, psoralen, xanthotoxin, and bergapten were also quantified in celery blades and leaves. The method utilizes a phenyl-bonded HPLC column with a methanol-water solvent system. This system allows the use of a detection wavelength (225 nm) more appropriate for these linear furanocoumarins than is currently used with normal phase systems.

Chlorine-selective monitoring for high-performance liquid chromatography with a hall electrolytic conductivity detector

Simple, inexpensive modifications have been made to a commercial Hall electrolytic conductivity gas chromatographic detector in order to utilize it for high-performance liquid chromatographic (HPLC) halogen (chlorine) selective monitoring. A portion (0.1–0.3 ml/min) of the column eluent was introduced directly together with hydrogen make-up gas into the heated quartz furnace of a Hall detector, the presence of chlorine-containing compounds in the solvent liberating hydrogen chloride, which was detected in the conventional manner by changes in electrolytic conductivity. Optimization of the detector parameters are described, important features being the length of the inlet tube protruding into the furnace, the furnace temperature and the electrolyte flow-rate. The detector was shown to be sensitive to 50 ng (1.4 ng/sec) of chlorine in chloroalkanes, eluted by reversed-phase HPLC with methanol-water solvent systems, giving a linear response over at least one order of magnitude (0.8–8.0 μ of chlorine). The choice of HPLC solvents was, however, limited to methanol and methanol-water mixtures, as with other organic solvents extensive carbon deposits accumulated in the detector furnace. Applications of the detector are illustrated by its use for monitoring the fractionation of vinyl chloride oligomers isolated from PVC resins.

Liquid Chromatographic Separation of Some Alkylaminocyclohexanecarbonitriles from Phenylcyclohexylamines Related to Phencyclidine

Abstract The synthesis of five 1-aminocyclohexanecarboni-Iriles and the corresponding 1-phenylcyclohexylamines related to phencyclidine is reported. The compounds are separated by reverse phase liquid chromatography in an acidic methanol-water solvent system.

Hydroperoxide-dependent oxygenation of [formula omitted]-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene by ram seminal vesicle microsomes. Source of the oxygen

Incubation of 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid with ram seminal vesicle microsomes (RSVM) triggers the oxygenation of trans -7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol). The principal oxidation products are 7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrenes which are non-enzymatic hydrolysis products of r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene. At short incubation times, an additional product is isolated which is identified as r-7,t-8,t-9-trihydroxy-c-10-methoxy-7,8,9,10-tetrahydrobenzo[a]pyrene. This product appears to arise by solvolysis of the extracted diolepoxide during high performance liquid chromatography using methanol-water solvent systems. The incubation of 18O-labeled 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid with BP-7,8-diol and RSVM leads to very little incorporation of 18O into the stable solvolysis products (analyzed by gc-ms of their peracetates). Parallel incubations conducted with 16O-labeled hydroperoxide under an 18O 2 atmosphere indicate that the principle source of the epoxide oxygen is molecular oxygen.

Liquid Chromatography in Pharmaceutical Analysis XI: Determination of Muscle Relaxant-Analgesic Mixtures Using Reversed-Phase and Ion-Pair Techniques

High-pressure liquid chromatography using reversed-phase and/or ion-pair techniques was used to optimize resolution of aspirin-containing muscle relaxant mixtures as well as other therapeutic agents commonly found in muscle relaxant-analgesic mixtures. The compounds were chromatographed on an octadecylsilane column using methanol-water solvent systems, some of which contained tetrabutylammonium cation as counterion. Mixtures of methocarbamol-aspirin and chlorzoxazone-acetaminophen were selected to demonstrate separation and quantification. The methocarbamol-aspirin mixture was chromatographed with methanol-water (40:60, pH 6.8) containing 0.01M tetrabutylammonium cation at a flow rate of 2.0ml/min. The chlorzoxazone-acetaminophen mixture was chromatographed with methanol-water (50:50) at a 2.0-ml/min flow rate. The separation and quantitation of each mixture were achieved in approximately 8min with accuracy in the 2–3% range.

Studies on the conformations and interactions of elastin. Proton magnetic resonance of the repeating tetramer.

AbstractProton magnetic resonance studies at 220 MHz were carried out on synthetic polymers of the repeating tetrapeptide of elastin. Temperature dependence and solvent‐mixture dependence of peptide proton chemical shifts were determined for both linear polymers, N‐formyl‐(Val‐Pro‐Gly1‐Gly2)n‐Val OMe where n ≃ 8 and 40, and for cyclic polymers (Val‐Pro‐Gly1‐Gly2)n, where n = 3 and 4. The Gly2 NH was found to be solvent shielded. In addition, by studying the polymers Boc‐Val‐Pro‐Gly1‐Gly2‐OH, H‐Pro‐Gly1‐Gly2‐Val OMe, H(Pro‐Gly1‐Gly2‐Val)3OH, and others, it was demonstrated that the Val C–O immediately preceding the Gly2 NH in the sequence was required for solvent shielding. Also the Gly2 NH resonance is found at higher field than the Gly1 NH resonance. This provides the basis for proposing a β turn in which the Pro and Gly1 residues form the corners, i.e., residues i + 1 and i + 2, and in which the Gly2 NH, residue i + 3 hydrogen bonds to the carbonyl of residue i, the Val residue.Studies on methanol–water solvent systems indicated retention of the β turn as a significant conformational feature. This suggests that the β turn occurs in the elastic fiber, which contains about 60% water but which utilizes association of hydrophobic groups as a primary force in fibrogenesis.