Composition Of Solvent Mixture Research Articles

Viscometric Behaviour and Micellization of Complexes of Copper (II) Stearate with N-donor Heterocyclic Dyes

Abstract Colloido-chemical behavior of copper (II) stearate and N-donor ligands in benzene-methanol mixture of varying composition has been investigated by viscometric measurements. The critical micelle concentration values depend upon the composition of solvent mixture and are to be found in close agreement with each other. The general trend observed is that the viscometric parameters with concentration are quite different and the plots are obtained with curvature at a definite concentration corresponding to critical micelle concentration at which there is marked change in the aggregation of the complex molecules. The results of phenylthiourea and benzothiazole complexes in regards to solute-solvent and solute-solute interactions in mixed solvent systems have been discussed in terms of the equations proposed by Moulik and Jones-Dole. The complexes were synthesized with N-donor ligands and copper (II) stearate and characterized by their elemental analysis, molecular weight, melting point, IR and NMR spectral studies. Due to the surface-active properties of copper stearate, the complexes show remarkable applications in industries and are used as emulsifiers, dispersing agents, foaming and wetting agents. N-donor ability of ligands make them useful as intermediates for many organic compounds such as colorants, agrochemical and pharmaceutical. They are good antiviral, antibacterial and antimalerial agents.

Viscometric investigations and molecular interactions of triphenodioxazine dyes in mixed organic solvents

Colloid chemical behaviour of 6,13-dichloro-3,10-dimethyl triphenodioxazine (TPDO-I) and 6,13-dibromo-3,10-dimethyl triphenodioxazine (TPDO-II) in non-aqueous solvent mixture benzene-methanol of varying composition has been investigated by viscometric measurements at 303 ± 0.1 K. The viscosity of the system increases with the increase in triphenodioxazine concentration. The Trend Change Point (TCP) values have been determined by intersection of two straight lines which are found to be dependent on the composition of solvent mixtures. The study confirms that the nature of triphenodioxazine agglomerate formed below and above 50% benzene concentration is quite different. The viscometric data have been analysed in terms of Einstein, Vand, Moulik and Jones-Dole equations. These well known equations have been successfully applied to explain the results of viscosity measurements and the viscometric parameters show that the behaviour of triphenodioxazine dyes changes in the proximity of 50% benzene concentration.

Controlled Self‐Assembly of Functional Metal Octaethylporphyrin 1 D Nanowires by Solution‐Phase Precipitative Method

Metal octaethylporphyrin M(OEP) (M = Ni, Cu, Zn, Pd, Ag, and Pt) nanowires are fabricated by a simple solution-phase precipitative method. By controlling the composition of solvent mixtures, the diameters and lengths of the nanowires can be varied from 20 to 70 nm and 0.4 to 10 microm, respectively. The Ag(OEP) nanowires have lengths up to 10 microm and diameters of 20-70 nm. For the M(OEP) nanowires, the growth orientation and packing of M(OEP) molecules are examined by powder XRD and SAED measurements, revealing that these M(OEP) nanowires are formed by the self-assembly of M(OEP) molecules through intermolecular pi...pi interactions along the pi...pi stacking axis, and the M(2+) ion plays a key role in the nanowire formation. Using the bottom contact field effect transistor structure and a simple drop-cast method, a single-crystal M(OEP) nanowires-based field effect transistor can be readily prepared with prominent hole transporting behaviour and charge-carrier mobility up to 10(-3)-10(-2) cm(2) V(-1) s(-1) for holes, which are 10 times higher than that of vacuum-deposited M(OEP) organic thin-film transistors (OTFTs).

Influence of the Substitution Degree on the Dilute Solution Properties of Cellulose Acetate

Modification of intrinsic viscosity, coil size, and preferential adsorption coefficients of cellulose acetate with various substitution degrees in single and mixed solvents was investigated at different temperatures. Miscibility is attained by specific competitive interactions between the solvent-solvent and solvent-polymer systems, which induce modification in the composition of solvent mixtures both inside and outside the polymer coil. The conformational properties in solutions were correlated with the preferential adsorption coefficients, known as depending on the interaction parameters of the polymer/solvent/solvent systems. The intermolecular interactions observed in the cellulose acetate solutions assure the main properties necessary for obtaining membranes with different applications.

Preparation of Poly(t-butyl methacrylate)-Polyimide Particles by Dispersion Polymerization of t-Butyl Methacrylate Using Poly(amic acid) as a Stabilizer and Subsequent Imidization

Dispersion polymerization of t-butyl methacrylate (BMA) and a cationic comonomer, 4-(vinylbenzyl)trimethylammonium chloride (VBA) was conducted in alkaline aqueous ethanol using various aromatic poly(amic acid)s (PAA) as stabilizers. The monodisperse particles were obtained in high yield using the optimum composition of solvent mixture depending on the PAA structure. By using a cationic comonomer (VBA), PAA was quantitatively incorporated into the particles. The imidization of PAA on the particles proceeded with acetic anhydride and 4-(dimethylamino)pyridine to form PBMA-polyimide (PBMA-PI) particles. The PBMA-PI particles were maintained in spherical shape by the thermal treatment up to 280 °C.

Improvement in bioavailability of transdermally applied flurbiprofen using tulsi ( Ocimum sanctum) and turpentine oil

Penetration enhancing potential of tulsi and turpentine oil on transdermal delivery of flurbiprofen, a potent non-steroidal anti-inflammatory agent, was investigated. The transdermal permeation rate of flurbiprofen across the rat abdominal skin from binary solvent mixture composition of propylene glycol (PG):isopropyl alcohol (IPA) (30:70%, v/v) was 98.88 μg/cm 2/h, significantly higher than other binary solvent mixtures. The corresponding steady state plasma concentration, 0.71 μg/ml, was much lower than required steady state plasma concentration of 3–5 μg/ml. Hence influence of tulsi and turpentine oil in the optimized binary solvent mixture along with the increased drug load on the flurbiprofen permeation was evaluated. The magnitude of the flux enhancement factor with turpentine oil and tulsi oil was 2.4 and 2.0 respectively at 5% (v/v) concentration beyond which there was no significant increase in the flux. Addition of 2% (w/v) hydroxypropyl methylcellulose (HPMC), as a thickening agent, resulted in desired consistency for the fabrication of patch with insignificant effect on permeation rate of flurbiprofen. The reservoir type of transdermal patch formulation, fabricated by encapsulating the flurbiprofen reservoir solution within a shallow compartment moulded from polyester backing film and microporous ethyl vinyl acetate membrane, did not modulate the skin permeation of flurbiprofen through rat skin in case of turpentine formulations whereas flux of formulations with tulsi oil was significantly altered. The influence of penetration enhancer and solvents on the anatomical structure of the rat skin was studied. Enhancement properties exhibited by turpentine oil and tulsi oil in optimized binary solvent mixture were superior as compared to solvent treated and normal control groups with negligible skin irritation. The fabricated transdermal patches were found to be stable. The bioavailability of flurbiprofen with reference to orally administered flurbiprofen in albino rats was found to increase by 2.97, 3.80 and 5.56 times with transdermal patch formulation without enhancer, tulsi and turpentine oil formulations, respectively. The results were confirmed by pharmacodynamic studies in rat edema inflammation model.

Physical Gelation of Binary Mixtures of Hydrocarbons Mediated by n-Lauroyl-l-Alanine and Characterization of Their Thermal and Mechanical Properties

Fatty acid amides, such as n-lauroyl-L-alanine, gelate both aliphatic and aromatic hydrocarbon solvents efficiently. In addition this compound is found to gelate the binary solvent mixtures comprised of aromatic hydrocarbon, e.g., toluene and aliphatic hydrocarbons, e.g., n-heptane. Scanning electron microscopy and atomic force microscopy show that the fiber thickness of the gel assembly increases progressively in the binary mixture of n-heptane and toluene with increasing percentage of toluene. The self-assembly patterns of the gels in individual solvents, n-heptane and toluene, are however different. The toluene gel consists of predominantly one type of morphological species, while n-heptane gel has more than one species leading to the polymorphic nature of the gel. The n-heptane gel is thermally more stable than the toluene gel as evident from the measurement using differential scanning calorimetry. The thermal stability of the gels prepared in the binary mixture of n-heptane and toluene is dependent on the composition of solvent mixture. Rheology of the gels shows that they are shear-thinning material and show characteristic behavior of soft viscoelastic solid. For the gels prepared from binary solvent mixture of toluene and n-heptane, with incorporation of more toluene in the binary mixture, the gel becomes a more viscoelastic solid. The time sweep rheology experiment demonstrates that the gel made in n-heptane has faster gel formation kinetics than that prepared in toluene.

Determination of clenbuterol in human urine and serum by solid-phase microextraction coupled to liquid chromatography

A solid-phase microextraction (SPME)–LC–UV method for the determination of the beta-adrenergic drug clenbuterol in human urine and serum samples was developed for the first time using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) coated fiber. The procedure required very simple sample pretreatments, isocratic elution, and provided highly selective extractions. All the aspects influencing fiber adsorption (extraction time, temperature, pH, salt addition) and desorption (desorption and injection time, desorption solvent mixture composition) of the analyte have been investigated. The linear ranges investigated in urine and serum were 10–500 and 5–500 ng/ml, respectively (that covers the typical clenbuterol concentration observed in biological fluids). Within-day and between-days R.S.D.% in urine ranged between 5.0–5.3 and 8.5–8.7, respectively, while in serum ranged between 5.5–5.9 and 8.7–9.1, respectively. Estimated LOD and LOQ were 9 and 32 ng/ml (spiked urine), respectively, and 5 and 24 ng/ml (spiked serum), respectively, well below the usual clenbuterol urinary and serum level.

Polimeryzacja akrylonitrylu w obecnosci funkcyjnego inicjatora azowego—propionianu 2,2‘-azobis[2-metylo-omega-hydroksy- oligo(oksyetylenowego)]omega-hydroksy-oligo(oksyetylenowego)

The course of acrylonitrile (AN) polymerization initiated with oligomeric azoester 2,2'-azobis[2-methyl-?-hydroxy-oligo(oxyethylene) propionate] [AIB-OOE(400)] in N,N-dimethylformamide (DMF) solutions, at temp. 60°C and in the whole possible to study range of monomer - solvent mixture compositions (expressed by the monomer mole fraction xM), was characterized (Fig. 1-4). The determined kinetic parameters of the reaction, i.e. rate constant (2kdf) and efficiency (f) of initiation, polymerization rate (overall rate constant K~), polymerizability (?) and indirectly also the propagation rate constant (kp) illustrate the variability of polymerization conditions. They are homogeneous, transient and heterogeneous (Table 2 and 3) being functions of xM (concentration effect of polymerization). A hypothesis was proposed that selective solvation of initiator by monomer and solvent has got further consequences expressed as changes of reactivity of growing radicals. The studied process of acrylonitrile polymerization in the presence of functional initiator (azoester) was compared with AN polymerization initiated with conventional initiator 2,2'-azobisisobutyronitrile (AIBN), carried out in similar conditions. The different kinetic characteristics of both polymerizations [particularly for xM>0.4, when a significant acceleration of the process takes place when AIB-OOE(400) initiator is used] suggest the possibility of preliminary arrangement of monomer, favored by mutual interactions of chemical groups in monomer and initiator.

Simultaneous determination of citalopram, fluoxetine and their main metabolites in human urine samples by solid-phase microextraction coupled with high-performance liquid chromatography

A liquid chromatography method was developed for the determination of some frequently prescribed selective serotonin re-uptake inhibitors (SSRI) – citalopram and fluoxetine – and its main metabolites – demethylcitalopram, didemethylcitalopram and norfluoxetine – in human urine samples, using a previous stage of solid-phase microextraction. All the extraction parameters influencing adsorption (extraction time, temperature, pH, ion strength and organic modifier addition) and desorption (desorption time and desorption solvent mixture composition) of the analytes on the fiber have been studied. A satisfactory reproducibility for extraction from urine samples (R.S.D. < 10%) was obtained. The linearity for urine ranged from 0.05 to 2 mg l −1 with limits of detection close to 0.01 mg l −1, which cover the typical urinary concentrations obtained for citalopram, fluoxetine and their metabolites.

Preparation of Well-Defined Poly[(ethylene oxide)-block-(sodium 2-acrylamido-2-methyl-1-propane sulfonate)] Diblock Copolymers by Water-Based Atom Transfer Radical Polymerization

Well-defined poly[(ethylene oxide)-block-(sodium 2-acrylanudo-2-methyl-1-propane sulfonate)] diblock copolymers [P(EO m -b-AMPS n )], have been obtained by water-based ATRP using α-methoxy-ω-(2-methylbromoisobutyrate) poly(ethylene oxide)s (MeO-P[EO] m -Br i B with m ranging from 12 to 113) and CuBr · 2Bpy (Bpy for 2,2'-bipyridyl) as macro-initiator and catalytic complex, respectively. Compared to direct polymerization in water, it has been demonstrated that the water/ methanol (3:1, v/v) mixture is better suited for predicting the final number-average molar mass from the initial monomer-to-macroinitiator molar ratio and achieving a quite narrow polydispersity, even at high monomer conversion (M w /M n ≈ 1.4 at 80% conversion). The effect of temperature, solvent mixture composition and addition of NaCI salt on the polymerization rate and extent of control over the copolymer molecular parameters have been highlighted as well.

The extraction of aromatic amino acids with binary and ternary mixtures of hydrophilic solvents

The extraction of tyrosine and phenylalanine with binary and ternary mixtures of hydrophilic solvents from aqueous salt solutions was studied, and several tendencies were observed. Simplex-lattice planning of experiment was used for the optimization of the composition of solvent mixtures. It was shown that the extraction systems developed could be employed for the almost complete extraction of tyrosine and phenylalanine from aqueous solutions.

Inorganic Surface Nanostructuring by Atmospheric Pressure Plasma-Induced Graft Polymerization

Surface graft polymerization of 1-vinyl-2-pyrrolidone onto a silicon surface was accomplished by atmospheric pressure (AP) hydrogen plasma surface activation followed by graft polymerization in both N-methyl-2-pyrrolidone (NMP) and in an NMP/water solvent mixture. The formation of initiation sites was controlled by the plasma exposure period, radio frequency (rf) power, and adsorbed surface water. The surface number density of active sites was critically dependent on the presence of adsorbed surface water with a maximum observed at approximately a monolayer surface water coverage. The surface topology and morphology of the grafted polymer layer depended on the solvent mixture composition, initial monomer concentration, reaction temperature, and reaction time. Grafted polymer surfaces prepared in pure NMP resulted in a polymer feature spacing of as low as 5-10 nm (average feature diameter of about 17 nm), an rms surface roughness range of 0.18-0.72 nm, and a maximum grafted polymer layer thickness of 5.5 nm. Graft polymerization in an NMP/water solvent mixture, however, resulted in polymer feature sizes that increased up to a maximum average feature diameter of about 90 nm at [NMP] = 60% (v/v) with polymer feature spacing in the range of 10-50 nm. The surface topology of the polymer-modified silicon surfaces grafted in an NMP/water solvent mixture exhibited a bimodal feature height distribution. In constrast, graft polymerization in pure NMP resulted in a narrow feature height distribution of smaller-diameter surface features with smaller surface spacing. The results demonstrated that, with the present approach, the topology of the grafted polymer surface was tunable by adjusting the NMP/water ratio. The present surface graft polymerization method, which is carried out under AP conditions, is particularly advantageous for polymer surface structuring via radical polymerization and can, in principle, be scaled to large surfaces.

Purification of wet process phosphoric acid by solvent extraction with TBP and MIBK mixtures

In the present work, the purification of the wet process phosphoric acid (WPA) with mixtures of methyl isobutyl ketone (MIBK) and tri-butyl phosphate (TBP) was investigated. Based on a three step purification process, the optimal solvent mixture composition that yielded the highest purified acid with the greatest possible P 2O 5 recovery was obtained for an MIBK percentage of 55%. Acid recovery increased for higher solvent MIBK contents whereas the impurities’ contents were lower for near equal TBP and MIBK percentages in the binary solvent mixture. The phase diagram of the ternary system H 3PO 4–water–optimal solvent mixture was determined. The partition ratios for H 3PO 4 as well as three trace metallic impurities were also obtained. Relative purification was better for Mg. The lowest selectivity was that of Fe which, unlike for the other trace elements does not improve when the solvent rate increases. The best purifications are obtained for the higher solvent mixture rates. While TBP has the highest selectivity, compared with MIBK, the solvent mixture is more selective for extracting H 3PO 4.

Optimization of extraction and determination of emodin from Polygonum cuspidatum Sieb. et Zucc. products by HPLC-DAD

A uniform experimental design procedure was used to investigate the effects of some operating parameters on the extraction of emodin from Polygonum cuspidatum Sieb. et Zucc. products. Variables tested were volume ratio of material to solvent, size of material, extraction time and temperature and composition of extraction solvent (mixtures of acetone-water). Each variable was tested at seven levels; 7 experiments were performed in random order. Analyses of the extracts were performed by high-performance liquid chromatography with diode array detection(HPLC-DAD). Analytical responses were processed by using a forward regression analysis, in order to find polynomial function describing the relationship between variables and responses. For all the analytes the experimental conditions for providing the highest extraction yield inside the experimental domain considered were found. Finally, a simple, rapid and accurate analytical method was developed for the determination of emodin by high performance liquid chromatography. The separation is achieved within 25 min on an ODS column using methanol and water as gradient mobiles. Emodin can be quantified by using external standard method detecting at 436 nm. Good linearity is obtained with correlation coefficient exceeding 0.9986 and the detection limit and the quantification limit are 1.53 and 3.23 mg/L respectively. This method shows good reproducibility for the quantification of the emodin with intra-day and inter-day relative standard deviation less than 2.3% and 5.6% respectively. Under optimized extraction conditions, the recovery of the standard is 96.5%. The validated method is successfully applied to quantify the emodin in seven Polygonum cuspidatum sieb. Et zucc. products, which provided an idea for the pre-treatment of determination of active compounds in traditional Chinese medicines.

Optimization of conditions for TLC screening of phenothiazine derivatives

Chromatographic properties of seven phenothiazine derivatives have been studied under conditions of TLC on silica gel plates in various single-component eluents. It is established that better results are provided by eluents with ammonia additions. Optimum compositions of binary and ternary solvent mixtures for the best separation of phenothiazine derivatives have been determined and the possibility of modifying silica gel with ammonia has been studied. The complete separation of the compounds studied is achieved using two-dimensional TLC.

Hydrogen-bond Assisted Formation of Rod Shaped Organic Nanocrystals: Control of the Aggregational State and Structural Elucidation

Rod-shaped nanocrystals are formed by self assembly of t-Bu-phenyl substi- tuted tetra(carboxamido)perylenes (BPP) in different solvents. The structure and the di- mensions of the nano-rods may be controlled by the choice of the hydrogen-bond ac- cepting capacity of the solvent (DMSO, DMF, DMAc, HMPA), by the concentration and by the composition of solvent-mixture (by adding hydrogen-bond donating solvents), but is independent of the surface used for their deposition (mica, silicon, gold, glass). The different forms of aggregation were examined by AFM and SNOM and were corre- lated to UV-Vis absorption spectra of the aggregates in solution. The orientation of the transition dipole moment of the molecules in the nanocrystals has been determined by polarized fluorescence microscopy and, in combination with the crystal structure of the t-Bu substituted analogue of BPP, is used to develop a model for the internal molecular structure of the rod shaped aggregates.

Preparation of Well‐Defined Poly[(ethylene oxide)‐block‐(sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate)] Diblock Copolymers by Water‐Based Atom Transfer Radical Polymerization

AbstractSummary: Well‐defined poly[(ethylene oxide)‐block‐(sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate)] diblock copolymers [P(EOm‐b‐AMPSn)], have been obtained by water‐based ATRP using α‐methoxy‐ω‐(2‐methylbromoisobutyrate) poly(ethylene oxide)s (MeO‐P[EO]m‐BriB with m ranging from 12 to 113) and CuBr · 2Bpy (Bpy for 2,2′‐bipyridyl) as macroinitiator and catalytic complex, respectively. Compared to direct polymerization in water, it has been demonstrated that the water/methanol (3:1, v/v) mixture is better suited for predicting the final number‐average molar mass from the initial monomer‐to‐macroinitiator molar ratio and achieving a quite narrow polydispersity, even at high monomer conversion ($\overline M _{\rm w} /\overline M _{\rm n}$ ≈ 1.4 at 80% conversion). The effect of temperature, solvent mixture composition and addition of NaCl salt on the polymerization rate and extent of control over the copolymer molecular parameters have been highlighted as well. magnified image

Thermosolvatochromism of Betaine Dyes Revisited: Theoretical Calculations of the Concentrations of Alcohol−Water Hydrogen-bonded Species and Application to Solvation in Aqueous Alcohols

Solvatochromic data of 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (RB) in aqueous methanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol at 25 degrees C were recalculated by employing a recently introduced model that explicitly considers the presence of 1:1 alcohol-water hydrogen-bonded species, ROH-W, in bulk solution and their exchange equilibria with water and alcohol in the probe solvation microsphere. The thermosolvatochromic behavior of RB in aqueous ethanol was measured in the temperature range from 10 to 60 degrees C; the results thus obtained were treated according to the same model. All calculations require reliable values of Kdissoc, the dissociation constant of the ROH-W species. This was previously calculated from the dependence of the density of the binary solvent mixture on its composition. Through the use of iteration, the volume of the hydrogen-bonded species, VROH-W, and Kdissoc are obtained simultaneously from the same set of experimental data. This approach may be potentially problematic because Kdissoc and VROH-W are highly correlated. Therefore, we introduced the following approach: (i) VROH-W was obtained from ab initio calculations, (ii) these volumes were corrected for the nonideal behavior of the binary solvent mixtures at different temperatures, (iii) corrected VROH-W values were employed as a constant in the equation used to calculate Kdissoc (from density vs binary solvent mixture composition). VROH-W calculated by the COSMO-RS solvation model fitted the density data better than those calculated by the IEFPCM model. In all aqueous alcohols, solvation by ROH-W is favored over that by the two precursor solvents. In aqueous ethanol, a temperature increase resulted in a gradual desolvation of RB, due to a decrease in the hydrogen-bonding of both components of the mixture. The microscopic polarities of ROH-W are much closer to those of the precursor alcohols.

Solvent effects on spectrophotometric titrations and vibrational spectroscopy of 5,10,15-triphenyl-20-(4-hydroxyphenyl)porphyrin in aqueous DMF

The spectrophotometric titration by sodium hydroxide of 5,10,15-triphenyl-20-(4-hydroxyphenyl)porphyrin ((OH) 1PH 2) is studied as a function of solvent composition of DMF–H 2O binary solvent mixture ([OH −] = 0.04 M). Combining the structure changes of the porphyrin and the “four orbital” model of Gouterman, many features of the optical spectra of this deprotonated para-hydroxy-substituted tetraphenylporphyrin in different composition of binary solvent mixtures can be rationalized. In highly aqueous solvents, the changes of the titration curves are shown to be mainly due to hydrogen-bonding of the oxygen of the phenoxide anion group by the hydroxylic solvent, Which decreases the energy of the phenoxide anion π orbital. Thus the phenoxide anion π orbital cannot cross over the porphyrin π orbital being a different HOMO. However, its energy is close to that of the porphyrin π orbitals. As a result, in the visible region, no charge-transfer band is observed, while in the visible-near region, the Soret peak split into two components. In nonaqueous solvents, the changes are mainly attributed to further deprotonation of pyrrolic-Hs of (OH) 1PH 2 by NaOH and coordination with two sodium ions to form the sodium complex of (OH) 1PH 2, which turns hyperporphyrin spectra of deprotonated of phenolic-H of (OH) 1PH 2 into three-banded spectra of regular metalloporphyrin.