Organic Solvent Ratio Research Articles

The impact of the cononsolvency effect on poly (N-isopropylacrylamide) based microgels at interfaces

The paper addresses the effect of solid interfaces on the cononsolvency effect for poly(N-iso propylacrylamide) based microgels containing different contents of the co-monomer allyl acetic acid (AAA). The cononsolvency effect is studied by dynamic light scattering (DLS) in solution and with atomic force microscopy (AFM) at surfaces against different mixtures of water and organic solvent (ethanol, iso-propanol, and tetrahydrofuran). For the studies at interfaces, the microgels are spin coated on silicon wafers that are precoated with poly(allylamine hydrochloride) (PAH). The minimum in particle volume due to cononsolvency shows a pronounced shift from 10–20 % of organic solvent to 40–50 % after deposition at the Si/PAH wafer. The strong shift indicates an increase of water to organic solvent ratio within the gel at the surface with respect to the bulk solution. In order to understand the increase of water to organic solvent ratio, shrinking/reswelling AFM experiments for different spin-coating conditions and under ambient conditions are carried out. Spin coating from water instead from different solvent mixtures has no effect on the cononsolvency. In ambient conditions, the cononsolvency effect disappears

Coulometric microdevice for organophosphate pesticide detection

A coulometric microdevice based on plug-based microfluidics was developed for the detection of organophosphate pesticides (OPs). Detection was based on the inhibition of an enzyme, acetylcholinesterase (AChE), by the OPs. Hydrogen peroxide (H2O2), produced in a series of enzymatic reactions involving AChE and choline oxidase (ChOx), was oxidized on a microelectrode array, and changes in AChE activity upon addition of an OP were measured by coulometry. A linear relationship was confirmed between the charge generated and the logarithm of the OP concentration. The lower limit of detection (LOD) was 33nM for malathion and 90nM for acephate, MEP, and diazinon. An increase in the ratio of organic solvents was also found to inhibit AChE activity. However, the concentrations sufficient to produce this effect were several orders of magnitude higher than those of the OPs, indicating that this influence can be ignored in the analysis of OPs.

Three-dimensional desirability spaces for quality-by-design-based HPLC development.

In this study, three-dimensional desirability spaces were introduced as a graphical representation method of design space. This was illustrated in the context of application of quality-by-design concepts on development of a stability indicating gradient reversed-phase high-performance liquid chromatography method for the determination of vinpocetine and α-tocopheryl acetate in a capsule dosage form. A mechanistic retention model to optimize gradient time, initial organic solvent concentration and ternary solvent ratio was constructed for each compound from six experimental runs. Then, desirability function of each optimized criterion and subsequently the global desirability function were calculated throughout the knowledge space. The three-dimensional desirability spaces were plotted as zones exceeding a threshold value of desirability index in space defined by the three optimized method parameters. Probabilistic mapping of desirability index aided selection of design space within the potential desirability subspaces. Three-dimensional desirability spaces offered better visualization and potential design spaces for the method as a function of three method parameters with ability to assign priorities to this critical quality as compared with the corresponding resolution spaces.

Preparation and Characterization of Al2O3/PVDF-HFP Based Polymer Electrolyte

Al2O3/PVDF-HFP based polymer electrolyte was prepared by the phase transfer method with different mass ratios of organic solvent and non-organic solvent. The solid polymer electrolyte was characterized by means of SEM, FTIR and AC impedance methods. The results show that the optimum mass ratio of organic solvent to non-organic solvent is 1:0.3 and the optimum mass ratio of Al2O3is 7%. The liquid absorption rate of the polymer electrolyte is 225%. The lithium ionic conductivity of the polymer electrolyte at room temperature is about 1.75×10−3S·cm-1, and the LiCoO2/Al2O3/PVDF-HFP/Li cell has good cycle performance.

Functional expression of Serratia marcescens H30 lipase in Escherichia coli for efficient kinetic resolution of racemic alcohols in organic solvents

Abstract A lipase from Serratia marcescens H30 was cloned and functionally expressed in E. coli in soluble form (more than 80%). The recombinant lipase activity reached 25,000 U/L after optimization. Different carriers were used to immobilize the recombinant S. marcescens lipase (SmL), and LH-EP was found to be the most ideal carrier. LH-EP immobilized SmL could catalyze enantioselective resolution of racemic alcohols. Using 4-phenyl-2-butanol as the model alcohol, the effects of temperature, organic solvent, water activity, acyl donor and substrate molar ratio on the LH-EP immobilized SmL catalyzed kinetic resolution were investigated. All of these factors influenced the resolution effect to some extent. At last, a high E value of more than 200 was achieved, with eeS > 99% and a conversion of 49.9%. Further studies showed that the LH-EP immobilized SmL could also catalyze the kinetic resolution of other structure similar racemic alcohols. These results indicate that the SmL is useful for biocatalytic production of chiral alcohols. This work is the first attempt of using SmL in this field, and it further broadens the application field of SmL.

New Strategy for Controlled Release of Drugs. Potential Pinpoint Targeting with Multiresponsive Tetraaniline Diblock Polymer Vesicles: Site-Directed Burst Release with Voltage

A series of amphiphlic diblock polymers, tetraaniline block with different length of poly(N-isopropylacrylamide) (TA-b-PNIPAM), have been successfully synthesized. In a suitable solution, the as-synthesized diblock polymers can form stable large compound vesicles (LCVs) with multiple bimolecular-layer structure through self-assembly. These factors, such as the block length, different organic solvent, solvent ratio, pH value, temperature, and voltage, which affect the morphology and properties of the assembled aggregates, are systematically investigated. When the degree of polymerization of PNIPAM block is close to 10, the as-synthesized diblock polymer may form stable LCVs with the uniform size as well as few defects in the mixed solvent of dimethylformamide/water (v/v = 3:7). The assembled LCVs possess the properties of triple-responsive capacity on temperature, pH, and voltage. Variation in any of these factors can cause some changes in the morphology of LCVs. The drug release properties for doxorubicin (DOX) loaded by LCVs affected by temperature, voltage, and different pH values have been investigated. It is interesting that the structure of LCVs can be destructed completely by applying a voltage at 0.6 V. With such an advantage, the drugs loaded by the LCVs could burst release into designated place by using appropriate circuit design or instrument, thus achieving maximum efficacy of the loaded drugs or other bioactive molecules without any unnecessary chemical substances added. This approach allows us to concentrate more on material design aspects only, without regard to the complex targeting issue which is the biggest obstacle of such materials in practical applications.

Improvement of Discharge Properties by Printing ${\rm LaB}_{6}$ Films on MgO Protective Layers in Plasma Display Panel

In this letter, a screen-printed LaB6 discontinuous film is coated on MgO thin film to improve the discharge properties of MgO protective layer in alternating current plasma display panel (AC PDP). High transmittance of is obtained by adjusting the concentration ratio of polycrystal LaB6 powders and organic solvent of screen-printed slurry. The LaB6/MgO double protective layer almost shows lower firing voltage and shorter discharge delay time than conventional MgO protective layer, likely owing to the low work function of LaB6. Therefore, it is highly suitable to be applied for AC PDP with low electrical power consumption.

Development of solid lipid nanoparticles based controlled release system for topical delivery of terbinafine hydrochloride

The study describes the development and evaluation of solid lipid nanoparticles (SLNs) of terbinafine hydrochloride (TH) for sustained release and skin targeting. TH-loaded SLNs were prepared by solvent-injection technique and optimized using 33 full-factorial design. Effect of drug:lipid ratio, surfactant concentration and volume of organic solvent were studied on % entrapment efficiency (%EE) and particle size (PS). The optimum formulation based on desirability (0.945) exhibited %EE of 73.74% and PS of 300nm. Optimized SLNs were incorporated into Carbopol gel and evaluated for drug content, pH, in vitro release, ex vivo retention, in vivo pharmacodynamic and stability studies. Drug release from SLNs dispersion followed Korsmeyer–Peppas model, indicating Fickian drug release, while that from the gel followed Higuchi model. The ex vivo studies through rat abdominal skin indicated skin retention ability of SLNs as compared to commercial product. In vivo pharmacodynamic studies showed that the SLNs based gel reduced fungal burden of Candida albicans in rats as compared to commercial product in shorter duration of time. The SLNs dispersion and gel exhibited physicochemical stability under refrigeration upto 3months. It was concluded that SLNs incorporated Carbopol gel had skin targeting ability and may serve as a promising carrier in treatment of fungal skin infections.

Surfactant protein B amount and kinetics in newborn infants: an optimized procedure

Surfactant protein B (SP-B) plays a key role in surfactant homeostasis affecting its biophysical properties and physiological function. Recently, a method to measure SP-B amount and kinetics from tracheal aspirates (TAs) became available. The main objective of this study was to improve the critical steps of the procedure to obtain a better SP-B sensitivity. We administered a 24 h continuous infusion of 1 mg/kg/h of 1(13)C-leucine to ten newborn infants. SP-B was isolated from serial TAs and its fractional synthesis rate, secretion time, peak time and half life were derived from (13)C enrichment curves obtained by gas chromatography mass spectrometry. SP-B amount in TAs was also assessed. During the extraction step, acidification and organic solvent ratio optimization doubled the recovery of SP-B from TAs, so did the elongation of the propylation time (from 20 min to 1 h) with enhanced leucine derivatization yield. Measurement of (13)C leucine enrichments, and therefore all SP-B kinetics parameters, were successfully calculated in all TAs samples due to the increase of SP-B yield. SP-B amount was 0.29 (0.16-0.41) % of total phospholipids with a minimum value of 0.08% belonging to one of the respiratory distress syndrome (RDS) patients. In conclusion, this new procedure enables accurate determination of SP-B kinetics even in the presence of low protein amount like in preterm RDS patients.

Optimization of Formulation Variables to Increase Antigen Entrapment in PLGA Particles

Efficient antigen entrapment is a key factor in preparation of poly (lactide-co-glycolide) acid (PLGA) vaccine formulations when the antigen is of short supply. This study presents a systematic approach in the testing of formulation variables with the objective to increase antigen entrapment in particles when the antigen stock concentration was low. Some of the experimental variables tested were poly (vinyl) alcohol (PVA) concentration in the inner (W1) and outer (W2) aqueous phase, W1/oil (O) phase ratio and choice of organic solvent. The double emulsion solvent evaporation technique was applied to prepare PLGA particles with sonication as the emulsifying force. To measure antigen entrapment efficiency, the antigen (bovine serum albumin, BSA) was isotope labeled with 125iodine (125I). Our results demonstrated that a low PVA concentration in the inner aqueous (W1) phase was beneficial to achieve a high encapsulation efficiency of antigen. On the contrary, in the outer aqueous (W2) phase, a high PVA concentration favored antigen entrapment. We also demonstrated that decreasing the W1 to O/polymer ratio contributed to increased entrapment efficiency. Testing different organic solvents (ethyl acetate, dichloromethane and chloroform), either alone or in combination, revealed that using chloroform as solvent resulted in the highest encapsulation of antigen and the highest production yield. Some of the results presented in this work are in disagreement with well-established formulation variables from previous studies.

Application of a design of experiment approach in the development of a sensitive bioanalytical assay in human plasma

To support a first-in-human (FIH) clinical study in healthy volunteers, a human plasma assay, a 20-fold more sensitive method than the validated non-clinical LC-MS/MS assays, was requested. For the clinical assay, a LLOQ of 0.050 ng/mL for Compound A and 0.100 ng/mL for Compound B was desired to accurately determine the analyte concentrations in human plasma samples across all treatment groups. A design of experiment (DOE) investigation was performed in an effort to optimize the extraction procedure of the bioanalytical assay used to support the first in human study and future clinical studies. Three factors, extraction buffer pH (two pHs), volume ratio of organic solvent to plasma (two ratios), and extraction shake time (three times), were selected for the DOE. Both analytes were analyzed at a low concentration, 0.150 ng/mL, and a stable isotope label internal standard was used for each analyte. To estimate the recovery of each analyte from the extraction, the response ratio of each analyte over the respective internal standard was used, and to estimate matrix effects, the absolute response (peak area) of each analyte was used. The results of the DOE indicated that the three factors tested had a more significant effect on the extraction of the metabolite, Compound B, compared to that of the parent, Compound A. The extraction buffer pH had the greatest influence on Compound B and the volume of extraction solvent had an influence on both analytes. Unexpectedly, a longer extraction time caused an apparent decrease in the overall recovery for both analytes. This was presumably due to an increased extraction of interfering matrix components. Optimal conditions were achieved for the combined analysis of both compounds using the DOE approach.

Ionic Liquid Enhanced Solvent Extraction for Bitumen Recovery from Oil Sands

An ionic liquid (IL) with low viscosity, 1-ethyl-3-methyl imidazolium tetrafluoroborate ([Emim][BF4]), was used to enhance bitumen recovery from oil sands by solvent extraction using a composite solvent of n-heptane and acetone. Results demonstrated that [Emim][BF4] increased the bitumen recovery by up to 95% at room temperature. Much less clay fines in the recovered bitumen than those using solvent extraction without IL, and organic residue was not observed in the spent sands. This technology circumvented the issue of tailing water because only a small amount of water was used to recycle IL, and organic solvent could be readily regenerated by distillation. The low viscosity of [Emim][BF4] made it outperform other alternative ILs for application in the oil sand industry. Results also highlighted the role of acetone in this technology (i.e., decrease IL viscosity and reduce IL consumption). The optimal solvent extraction conditions were found to be stirring for 10 min at 450 rpm at 25 °C. The optimized ratio of acetone to n-heptane in the composite solvent and the ratio of organic solvents to oil sands was determined as 2:6 (v/v) and 4:1 (v/w), respectively.

Preparation and Properties of PLA Microspheres Containing ENRO by an S/O/W Emulsion Technique

In the present paper, monodisperse poly(lactic acid) (PLA) microspheres (MS) containing the enrofloxacin (ENRO), were manufactured by using a modified solid in oil in water (S/O/W) emulsion solvent evaporation method. In order to prepare PLA microspheres with a higher drug loading efficiency by this modified technique, the test of stability and productivity of the primary emulsion was preliminary examined by change species or concentration of the oil-soluble surfactant and the ratio of water and organic solvent. Firstly, enrofloxacin polylactic acid microspheres (ENRO-PLA-MS) were producted, then the morphology and particle size distribution were estimated by scanning electron microscopy (SEM), its encapsulation efficiency and drug loading efficiency were assessed by High performance liquid chromatography (HPLC). In vivo conditions were simulated by an stable release buffer to obtain a detailed release and polymer degradation profile. Consequently, the ENRO-PLA-MS had a denser structure with a smooth, pore-free surface, the preparation of microspheres was simple, the prepared microspheres had excellent controlled drug release characteristics in vitro.

Treatment of phosphorus waste water using crystallization method

Phosphorus is the restrictive factor of water eutrophication and phosphorus removal is the key point to control this phenomenon. It's also important to recover phosphorus resource from wastewater. Crystallization method was used to treat and recycle high concentration phosphorus wastewater, the selection of organic solvent, influence of volume ratio of organic solvent and wastewater, precipitation time and stirring speed on the production of crystal and its structure was investigated. Experimental results indicate that, with ethanol as extractant, under the condition of volume ratio of ethanol to wastewater being 1.5:1 and stirring speed about 200 r/min, crystal precipitated fast with fine crystal shape and purity, phosphorus removal efficiency more than 85% was obtained.

Mg/Al-CO3 layered double hydroxide nanorings

Mg/Al-CO3 Layered Double Hydroxide (LDH) nanorings with a 750 nm exterior diameter and 250 nm interior diameter were synthesized in an organic/water solvent system via a urea hydrolysis method, using Mg10(OH)18Cl2·5H2O nanowires as precursors. X-Ray diffraction and Fourier-transform infrared spectroscopy clearly revealed the nanorings to comprise Mg/Al-CO3 LDH. The character of the precursor materials and the ratio of organic solvents to water used for reaction played crucial roles in determining the final ring-like morphology. A possible mechanism was proposed for the LDH nanoring formation. The unique LDH nanorings exposed a higher specific surface area and larger pore volume than plate-like and flower-like analogues, and thus were further explored for their catalytic activity using the Knoevenagel reaction between benzaldehyde and diethyl malonate as a probe reaction. The ring-like structure displayed a significantly enhanced catalytic performance above other analogues.

Antifungal Activity in Ethanolic Extracts of Carica papaya L. cv. Maradol Leaves and Seeds

Bioactive compounds from vegetal sources are a potential source of natural antifungic. An ethanol extraction was used to obtain bioactive compounds from Carica papaya L. cv. Maradol leaves and seeds of discarded ripe and unripe fruit. Both, extraction time and the papaya tissue flour:organic solvent ratio significantly affected yield, with the longest time and highest flour:solvent ratio producing the highest yield. The effect of time on extraction efficiency was confirmed by qualitative identification of the compounds present in the lowest and highest yield extracts. Analysis of the leaf extract with phytochemical tests showed the presence of alkaloids, flavonoids and terpenes. Antifungal effectiveness was determined by challenging the extracts (LE, SRE, SUE) from the best extraction treatment against three phytopathogenic fungi: Rhizopus stolonifer, Fusarium spp. and Colletotrichum gloeosporioides. The leaf extract exhibited the broadest action spectrum. The MIC(50) for the leaf extract was 0.625mgml(-1) for Fusarium spp. and >10mgml(-1) for C. gloeosporioides, both equal to approximately 20% mycelial growth inhibition. Ethanolic extracts from Carica papaya L. cv. Maradol leaves are a potential source of secondary metabolites with antifungal properties.

Effect of HPLC binary mobile phase composition on the analysis of carbonyls

The relative performance of the binary mobile phase in the high-performance liquid chromatography analysis of carbonyl compounds (CCs) was tested using the liquid-phase standards containing 15 aldehyde/ketone-DNPH mixture. The Hichrome column was employed for the analysis of CCs at a flow rate of 1.5 mL min( - 1). The binary mobile phases prepared using both acetonitrile/water (AW) and a possible alternative of methanol:water (MW) mixture were examined by their calibration results. The data derived from these two binary phases were then evaluated in terms of three key variables (i.e., resolution, relative sensitivity, and retention time). The relative water content (or the water to organic solvent ratio (W/A) or (W/M)) of the binary phase was found as the key variable for the performance. The results indicate that the optimal resolution of AW combination was attained consistently for most composition, while MW generally suffered from overpressure problem. The changes of water content in the AW mixture led to the changes of all three variables in the quantitative analysis of CCs. The obtained results confirm that the AW mixture should be the optimal elutant for the CC analysis, as other simple binary compositions like MW are limited in many respects.

Polyhedral 50-Facet Cu2O Microcrystals Partially Enclosed by {311} High-Index Planes: Synthesis and Enhanced Catalytic CO Oxidation Activity

Micro- and nanoparticles with high-index facets may exhibit higher chemical activities that are of great importance in practical applications. Cuprite is a potential alternative to expensive noble metals as the catalyst for CO oxidation at moderate temperatures. We report here a solution based approach to the preparation of unusual polyhedral 50-facet Cu2O microcrystals with a morphological yield higher than 70%. It has been revealed that the concentration of OH(-) and the volume ratio of polar organic solvent to water in the mixed solvent play crucial roles in controlling the morphology of Cu2O microcrystals. The formation of the 50 facets could be geometrically viewed as the truncation of all the 24 vertices of a small rhombicuboctahedron having 26 facets. When growing from solutions, however, the anisotropic growth rates along the <100>, <110>, and <111> directions might be responsible for the formation of this morphology. The Miller index of the 24 nearly isosceles trapezoids could be assigned to {311} planes based on geometrical analysis and was verified by simulated models using the WinXmorph software and supported by TEM and ED observations. Compared with other polyhedral Cu2O microcrystals, the as-prepared microcrystals showed a higher specific catalytic rate toward CO oxidation.

Experimental study of the retention properties of a cyclo olefin polymer pillar array column in reversed-phase mode

Experimental measurements to study the retention capacity and band broadening under retentive conditions using micromachined non-porous pillar array columns fabricated in cyclo olefin polymer are presented. In particular, three columns with different depths but with the same pillar structure have been fabricated via hot embossing and pressure-assisted thermal bonding. Separations of a mixture of four coumarins using varying mobile phase compositions have been monitored to study the relation between the retention factor and the ratio of organic solvent in the aqueous mobile phase. Moreover, the linear relation between the retention and the surface/volume ratio predicted in theory has been observed, achieving retention factors up to k=2.5. Under the same retentive conditions, minimal reduced plate height values of h(min)=0.4 have been obtained at retention factors of k=1.2. These experimental results are compared with the case of non-porous and porous silicon pillars. Similar results for the plate heights are achieved while retention factors are higher than the non-porous silicon column and considerably smaller than the porous pillar column, given the non-porous nature of the used cyclo olefin polymer. The feasibility of using this polymer column as an alternative to the pillar array silicon columns is corroborated.

A modified double-emulsion method for the preparation of daunorubicin-loaded polymeric nanoparticle with enhanced in vitro anti-tumor activity

The encapsulation of hydrophilic drug in polymeric nanoparticles with high loading remains a challenge due to the rapid penetration of the drug to the external aqueous phase. In order to improve the encapsulation efficiency of daunorubicin (DNR) in poly(d,l-lactic-co-glycolic acid (PLGA) and poly(d,l-lactic acid) (PDLLA) nanoparticles, we fabricated a series of DNR-loaded nanoparticles using a modified double-emulsion solvent evaporation/diffusion method, which introduced a partially water-soluble organic solvent into the particle formation. The influence of various preparation parameters was investigated systematically, such as the ratio of organic solvent, the type of surfactant, the type of polymers and the molecular weight. Results showed that regular spherical PLGA nanoparticles with diameters of 200–300 nm could be produced with a remarkably high DNR encapsulation efficiency (>80%) and loading (6.5% (w/w)). Upon encapsulation, the sustained release of DNR could be controlled over 2 weeks. The results of FT-IR and DSC analysis indicated that the encapsulated DNR in polymeric nanoparticles was inclusion, not absorption. Furthermore, optimized DNR/PLGA nanoparticles showed a significant enhancement of cellular uptake, higher cytotoxicity against HL-60 cells compared with free DNR. These results were potentially useful for the nanoparticle formulation of hydrophilic chemotherapeutic drugs that require efficient delivery to cancer cells as well as sustained release at the specific site.