Addition Of Alkanols Research Articles

Optimization of Fat-Soluble Vitamins Separations by Reversed-Phase Liquid Chromatography with the Use of Aliphatic Alcohols as Mobile Phase Additives

In an effort to reduce the total amount of organic solvent required for the elution of fat-soluble vitamins (FSVs) in reversed-phase liquid chromatography separation, a systematic approach was developed using a mixture of methanol, water, and an alkanol as the mobile phase. In the optimization procedure, a five-parameter retention model was developed and the statistical evaluation of model, revealed that the variations of retention times of each vitamins caused by addition of alkanols to the mobile phase were predicted with an average relative deviation of 1.83%. For this model, all the and values for all vitamins were higher than 0.9839 and 0.9798, respectively, and lack of fit (LOF) values were not statistically significant. A mobile phase containing methanol/octanol/water (86:9:5) was proposed as the optimum mobile phase composition using grid search method and a good agreement was observed between predicted and experimental response values (relative error = −0.734%). Using this optimum condition, the simultaneous separation of six FSVs was achieved in 9.94 min. The results showed an improvement in the separation of FSVs and in reduction of the total amount of organic solvent used for separation with addition of low amount of alkanols as additive to the mobile phase.

Effect of the addition of alkanols of different topology to dipalmitoyl-phosphatidylcholine vesicles in the presence of gramicidin

In the present work, we analyze the effect of incorporation of the nonanol family (e.g., 1-Nonanol (1-N), 5-Nonanol (5-N), and 2,6-Dimethyl-4-Heptanol (2,6-DH)) into DPPC LUVs in the presence of different gramicidin concentrations. The principal aim of this work is to study the effect of alkanols solubilization on the physicochemical properties of lipid bilayers in the presence of peptide trans-membrane channels, that is, the effects of nonanol family in the interface of lipid–peptide region, considering that the study provides the analysis of a ternary system by direct excitation as well as by Fluorescence Resonance Energy Transfer. Fluorescence measurements were carried out at 20°C after direct excitation of the extrinsic probe or by Fluorescence Resonance Energy Transfer (FRET) from the tryptophan group of gramicidin. Alkanol incorporation decreases with increasing gramicidin content and branching of the additives. 1-N generates most important changes in the inner part of the bilayer, where it produces an increase in bulk acyl chain mobility. Similarly, 1-N significantly modifies the properties of the hydrophilic–hydrophobic interface region sensed by Laurdan, increasing the polarity of the probe microenvironment and/or increasing the relaxation time of interfacial water molecules. On the other hand, 1-N produces a decrease in PDA fluorescence lifetime, a result that can be explained by a significant amount of water entrance to the inner part of the bilayer. The same behavior was observed when pseudo-first-order quenching rate constants by oxygen were measured. 1-N produces an increase in mobility/solubility of the oxygen in the lipid membrane, an effect that is more noticeable in the deep region of the bilayer sensed by PDA, in the absence and in the presence of 2mol% of Gr. 1-N incorporation produces a greater reduction in GP value than 5-N and 2,6-DH when Laurdan was excited by FRET. These results show that 1-N has the greatest effect in the lipidic domains near the gramicidin channel. On the other hand, excimer–monomer ratios of PDA obtained by FRET show that 1-N reduces the lateral mobility of acyl chains near the lipid–gramicidin interface when gramicidin concentration in the lipid bilayer increases. This effect is more noticeable than that obtained by direct irradiation of the probe in the presence of 5-N and 2,6-DH. On the other hand, the addition of the three alkanols in the presence of Gr produces a noticeable increase in the water permeability, particularly for 1-N. In this context, we propose a scheme that represents the effect of 1-nonanol on the water outflow in DPPC LUVs in the absence and in the presence of Gr.

Dynamics of Polar Solvation in Quaternary Microemulsions

Steady-state spectroscopy and time-resolved solvation dynamics have been used to investigate the effects the addition of alkanol has on the location of coumarin 343 (C343) in cetyltrimethylammonium bromide (CTAB)/1-pentanol/cyclohexane/water, CTAB/1-heptanol/cyclohexane/water, and sodium dodecyl sulfate/1-heptanol/cyclohexane/water reverse micelles. Steady-state spectroscopy showed that the probe molecule is not sensitive to alkanol chain lengths or water loading. Instead, C343 is sensitive to the surfactant used to form the reverse micelles. Solvation dynamics measurements utilizing ultrafast time-resolved fluorescence-upconversion spectroscopy revealed two solvation reorganization times regardless of the micellar system studied or hydration level. A hundreds of picosecond time component is attributed to collective motion of the interface. Time-zero analysis reveals a substantial relaxation component occurring on the femtosecond time scale.

Spectroscopic probing of the effect of alkanols on the properties of the head group region in reverse micelles of AOT–heptane–water

The effects of addition of alkanols (ethanol, n-hexanol, and 3-ethyl-3-pentanol) on the micropolarity and microviscosity of the head group region in reverse micelles of AOT–heptane–water have been investigated by fluorescence probing methods (ANS fluorescence yield and TMADPH fluorescence anisotropy), complemented by the use of the solvatochromic probe E T (30) in absorption spectroscopy. For all the alkanols considered, ANS fluorescence in AOT reverse micelles (at W=3) is quenched by additive incorporation, being the effect elicited almost independent of the alkanol chain length and topology. As sensed by the E T (30) parameter, the micropolarity of the micelle surface increases, remains unmodified, and decreases upon addition of ethanol, 3-ethyl-3-pentanol, and hexanol, respectively. While ethanol barely modifies the fluorescence anisotropy of TMADPH, 3-ethyl-3-pentanol and n-hexanol addition strongly decrease it. The similarity of the tendencies of ANS data to TMADPH anisotropies and the differences between ANS data and E T (30) values would indicate that, at least for 3-ethyl-3-pentanol and n-hexanol, microviscosity, rather than micropolarity, must be considered to interpret the effect of the alkanols upon the fluorescent behavior of ANS.

Facile Routes to Alkoxymaleimides/Maleic Anhydrides

New routes to alkoxymaleic anhydrides 1a/b have been described in good yields via base-induced chemoselective vinylic substitution of bromo atom in bromomaleimide 4 with alkanols, and base-induced oxa-Micahel addition of alkanols to dialkyl acetylenedicarboxylates 8a/b as key steps. An unusual acyl exchange in the conversion of 6a/b to 1a/b under very simple and mild reaction conditions is noteworthy.

Titrimetric determination of Cremophor® EL in aqueous solutions and biofluids: Part 2: Ruggedness of the method with respect to biofluids

A titration method for Cremophor® EL, as a multicomponent mixture commonly used as non-ionic emulgent for manufacturing certain parenteralia, was developed for quantitative routine analysis in biofluids. A coated wire electrode is used as the end-point indicator in potentiometric titrations of Cremophor® EL with sodium tetraphenylborate. The method tolerates a broad pH range, addition of alkanols and components of drug formulations and is sufficiently rugged. Reliable results are obtained at 20°C. Disturbing ions from biofluid matrices can be masked or complexed by addition of formaldehyde, ethylenediaminetetraacetic acid and sodium fluoride. Sodium hydroxide is used for the required adjustment of the samples to pH 10. Cremophor® EL spiked urine samples can be determined directly, whereas the true value of the emulgent content in the case of Cremophor® EL spiked plasma samples is achieved by means of a conventional method.

Poly[(methyl methacrylate)-co-(methacrylic acid)] Microgel Particles: Swelling Control Using pH, Cononsolvency, and Osmotic Deswelling

The swelling of poly[(methyl methacrylate)-co-(methacrylic acid)] (PMA-MAA) microgel particles (prepared using 17 mol % MAA) dispersed in water can be controlled by pH adjustment, addition of alkanols, and addition of water soluble homopolymer. Transmission electron microscopy revealed two-dimensional order for PMA-MAA particles deposited on a grid from alkaline solution. The swelling of the microgel particles was studied by means of photon correlation spectroscopy. The stability of the particles was investigated using turbidity−wavelength measurements; flocculation occurred when the pH was less than 6. A buffer (NaHCO3/NaOH) was employed to stabilize the pH of the PMA-MAA dispersions at about pH = 10. The hydrodynamic diameter of the PMA-MAA particles is sensitive to pH with a maximum at about pH = 8. PMA-MAA microgel particles deswell upon addition of an alcohol (methanol or 2-propanol) or poly(ethylene glycol) (PEG). Poly(N-isopropylacrylamide) (PNP) microgel particles also deswell in aqueous alcohol s...

Winsor transitions and interfacial film compositions in systems containing sodium dodecylbenzene sulphonate and alkanols

In alkane + water systems, containing the single chain surfactant sodium dodecylbenzene sulphonate (SDBS), inversion of microemulsion type (from o/w to w/o) cannot be effected by addition of salt alone. The addition of alkanols as cosurfactants can promote the Winsor I—III—II transitions and reduce the oil-water interfacial tension to ultralow values. The compositions of mixed monolayers of surfactant and alkanol have been determined tensiometrically and (in the case of butanol) by direct analysis. Long chain alkanols are more effective at promoting microemulsion phase inversion than the shorter homologues. The ratios of cosurfactant to surfactant at the microemulsion drop surfaces at the condition of minimum tension are 3.0, 1.3 and 1.0 for butanol, octanol and dodecanol, respectively. The effects of alkane chain length on monolayer compositions incorporating butanol are discussed in terms of the differing extents of alkane penetration into the chain region of the film. Estimated rigidity constants for films containing SDBS and butanol are low (approximately 0.7 kT) in line with measured values reported recently for a number of surfactant+cosurfactant systems.

Some properties of alkyl 2-chloro-1,1,2-trifluoroethyl ethers

A series of alkyl 2-chloro-1,1,2-trifluoroethyl ethers was prepared by the addition of alkanols to chlorotrifluoroethylene. R-OH + CF2=CFCl → R-O-CF2-CHClF R = methyl, ethyl, isopropyl, t-butyl, cyclohexyl, pinakolyl, menthylThermal stability of alkyl 2-chloro-1,1,2-trifluoroethyl ethers was investigated on glc columns at 80 - 200 °C and on heating in solvents of various polarity.Products of thermal decomposition of t-butyl 2-chloro-1,1,2-trifluoroethyl ether in benzene, benzylalcohol and decahydronaphthalene were isolated and identified. In strongly polar solvents (N,N-dimethylaniline, pyridine, dimethylsulfoxide or N,N-dimethylformamide) the decomposition of the t-butyl 2-chloro -1,1,2-trifluoroethyl ether did not proceed.

Dynamic properties of micellar solutions: I. Effects of short-chain alcohols and polymers on micellar stability

The effect of n-alkanols from C1 to C5 on both equilibrium and dynamic properties of sodium dodecyl sulfate (SDS) micellar solutions has been investigated using electrical conductivity and pressure-jump methods. Methanol and ethanol were found to decrease the conductance of micellar solutions due to the lowering of dielectric constant of solvent. Higher alkanols from C3 to C5 may decrease or increase the conductance of micellar solutions depending on the concentration of SDS. At low surfactant concentration, a minimum of conductance was observed. This has been attributed to both effects of decrease in surfactant monomer concentration (CMC) and the increase in counterion dissociation of micelles upon the penetration of alcohols into micelles. At higher surfactant concentration, the conductance was found to increase directly due to the dominance of the latter effect. Unlike the complex change of conductance, the slow relaxation rate constant, 1/τ2, has been found to increase monotonically upon the addition of all alkanols except pentanol. The labilizing effect (i.e., decreasing τ2) of alkanols increases with increasing alkanol chain length from C1 to C3 and levels off at C4. The labilizing effect has also been found to vary with SDS concentration depending upon the mechanism of slow relaxation process. Based on the Aniansson and Wall theory, the labilizing effect of alkanols has been attributed to two factors: (1) the stabilization of micelle nuclei either due to a decrease of micelle nucleus size, or due to an increase of micelle nucleus population; (2) the decrease of activation energy for the formation of micelle nuclei. In view of the changes in both slow relaxation time and CMC upon the addition of alkanols, the concept of micelle stability has been discussed in terms of the “thermodynamic stability” and the “kinetic stability” of micelles. Finally, the effect of polymers on the slow relaxation process was also investigated. The slow relaxation rate constant 1/τ2 was found to increase by three orders of magnitude as the concentration of polyvinylpyrrolidone increased up to 8% (w/w). Based on the molecular model of polymer-micelle complex proposed by B. Cabane (J. Phys. Chem.81, 1639, 1977), the effect of polymer has been interpreted in terms of the polymer being the nucleating agent for micelle nuclei. The result verifies the concept that the rate-limiting step in micelle formation and dissolution process is the formation of micelle nuclei.

Micellization behavior in the presence of alcohols

The effect of the addition of alkanols on the micellization of various surfactant molecules has been investigated using a molecular thermodynamic approach. Solubilization of the longer chain alcohol molecules in the micelles brings about a reduction in the critical micelle concentration of these surfactants. Longer alcohols and larger amounts of a given alcohol increase the depression of the CMC. The calculated values of the CMC are in agreement with experimental values reported in the literature. Further, the average aggregation number for the surfactant as well as for the solubilized alcohol molecules are also found to be in satisfactory agreement with the available experimental data. The distribution coefficient, defined as the ratio of mole fractions of alcohol in the micellar and aqueous phases, is shown to be independent of the nature of the surfactant and to decrease with increasing alcohol concentrations. The present calculations suggest the occurrence of an “azeotrope” for some surfactant-alcohol systems.

Alcohol effects on rapid kinetics of water transport through lipid membranes and location of the main barrier.

The effect of 1-alkanols (from 1-butanol up to 1-dodecanol) on the water permeability of dimyristoylphosphatidylcholine vesicle membranes was studied by measuring the osmotic swelling rate as functions of 1-alkanol concentrations and temperatures above the gel-to-liquid-crystalline phase transition. For 1-butanol and 1-hexanol, the activation energy for water permeation was invariant with the addition of alkanols, whereas for 1-octanol, 1-decanol and 1-dodecanol, the activation energy decreased depending on the alkanol concentration, and the extent of the decrease was larger for alkanol with a longer hydrocarbon chain. These results suggests that hydrocarbon moiety beyond seven or eight carbon atoms from the head group in phospholipid molecules constitutes the main barrier for water permeation through the dimyristoylphosphatidylcholine vesicle membrane. The relative volume change of the vesicle due to osmotic swelling increased with the addition of 1-alkanols. Presumably, the membrane structural strength is weakened by the presence of 1-alkanols in the membrane. Contrary to the dependence of the swelling rate upon the alkanol carbon-chain length, no significant difference in the effect on the relative volume changes was seen among the 1-alkanols. This result suggests that weakening of the membrane structure is caused by perturbation of the membrane/water interface induced by incorporation of 1-alkanols into the membrane.

The Partial Molar Volume of 1-Alkanols in a Sodium Dodecylsulfate Solution around Its Critical Micelle Concentration

Abstract The partial molar volume (Va) of 1-alkanols (C6–C8) was determined at 25 °C in a solution of sodium dodecylsulfate up to its critical micelle concentration in water. The Va in micellar solutions is higher than that in non-micellar ones. This increase in Va has been explained in terms of the promotion of micellization by the addition of alkanol.

Viscosities of cholesteryl myristate, palmitate and oleate in the isotropic, cholesteric and transition states with and without the addition of higher alkanols.

The viscosities of cholesteryl myristate (ChM), cholesteryl palmitate (ChP) and cholesteryl oleate (ChO) were measured with a cone-plate viscometer at various shear rates with continuous heating. After a rapid decrease near the smectic-cholesteric transition temperature, the viscosities decreased gradually in the cholesteric and isotropic phases, with a peak at the cholesteric-isotropic transition. The peak temperature agrees reasonably well with the values obtained by differential scanning calorimetry (DSC) and polarized light microscopy. From the shear rate vs. shearing stress relations at various temperatures, it was concluded that the flow in the isotropic phase was Newtonian, while the flow in the cholesteric phase was non-Newtonian. With respect to the cholestericisotropic transition temperature, the effect of alkanols on the of ChM was the same as that on the DSC curve. However, the vs. temperature curve showed a stronger transition peak than the DSC curve, in spite of the addition of alkanols. The change of ChM under stress was also followed at various temperatures ; the static viscosity was obtained by extrapolation of the to zero time and the viscosity from the steady-state value under stress. Comparison between the measured with continuous heating and the kinetic confirmed the validity of the former method, especially in the isotropic and cholesteric-isotropic transition states.

Notes - The Addition of Alkanols to 1,1,2,-Trichloro-3,3,3-trifluoropropene - Some Corrective Data

Notes - The Addition of Alkanols to 1,1,2,-Trichloro-3,3,3-trifluoropropene - Some Corrective Data