Organic Phase Ratio Research Articles

A highly efficient three-phase single drop microextraction technique for sample preconcentration.

A highly efficient three-phase single drop microextraction (SDME) method is presented by using an organic-aqueous compound droplet. A coupling microdevice is designed to produce compound droplets in different sizes conveniently. In this way, the volume ratio of organic phase to aqueous phase in a compound droplet can be significantly reduced. Good operability and droplet stability were observed during extraction under vigorous stirring conditions. Five statins were used as model compounds and spiked in river water and human serum samples to evaluate the analytical performance of the proposed method. By using a 1.2 μL toluene-aqueous compound droplet (volume ratio 0.2 : 1), a 350 to 1712 fold enrichment of statins was obtained within 4 minutes. The results indicate that the proposed method is a very rapid and efficient sample pretreatment method, and is promising for automated and high-throughput applications.

Solvent extraction of rubidium and cesium from salt lake brine with t-BAMBP–kerosene solution

The residues of salt lake brine from which potassium had been removed were used to extract Rb+ and Cs+ together with a sulphonated kerosene (SK) solution of 1.0 mol/L 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP). Rb+ and Cs+ were enriched and separated effectively by precipitating Mg2+ before extraction and by scrubbing out K+ and Na+ repeatedly before stripping. The effects of the volume ratio of organic phase to aqueous extraction phase (O/A), alkalinity of aqueous phase (c(OH)−), interference from K+ and Mg2+, and ratio the volume of organic phase to aqueous scrubbing phase (O/A′) were investigated. The experimental brine was extracted optimally by 5-stage extraction with 1.0 mol/L t-BAMBP in SK, c(OH−)=1 mol/L, and O/A=1:1. The scrubbing yield of rubidium was only about 10.5% when the extraction solvent was washed 3 times with 1×10−4 mol/L NaOH at O/A′=1:0.5. After 5-stage countercurrent extraction, the final extraction yields of Rb+ and Cs+ reached 95.04% and 99.80%, respectively.

Cobalt Ion Extraction by 2-Ethylhexyl Phosphoric Acid Mono-2-Ethylhexyl Ester Microemulsion Saponified

The extraction process of cobalt using microemulsion system saponified with P507 as extracting agent was studied. The influences of initial concentration, the concentration of P507, initial pH, the extracting time and the volume ratio of organic phase to water phase on extraction coefficient were also studied. Experimental results show that the saponification microemulsion system using P507 as extractant is thermodynamic stable, and it can separate cobalt better. The optimum conditions were achieved as: the initial concentration is 0.04 mol/L, pH is 2; The concentration of P507 is 6%, extraction time is 6 min; The volume ratio of organic phase to water phase is 1.5:1.

Extraction and stripping of Cr(VI) from aqueous solution by solvent extraction

The solvent extraction of Cr(VI) from an aqueous solution by hexadecyl trimethyl ammonium bromide (HTAB) in amyl alcohol was investigated at 27°C. The maximum extraction efficiency was obtained at pH 1.0 ± 0.1. Chromate is an anionic form; therefore, it requires a cationic carrier for the extraction purpose and HTAB acts as cationic carrier in this study. The efficiency of extraction decreased with increasing the chromium concentration. The extracted Cr(VI) in the organic phase can be back extracted into 0.2 mol/L sodium nitrate. The important experimental parameters examined were: the effect of HTAB concentration, the effect of pH, the effect of Cr(VI) concentration, the effect of equilibrium time, and the effect of temperature, aqueous to organic phase ratio, and various stripping agents. Real effluent was also studied under optimized condition [Cr(VI) concentration 10 mg/L at pH 1.0 ± 0.1, carrier concentration = 0.06 mol/L, stripping concentration = 0.2 mol/L, and equilibrium time = 5 min at 27°C] and satisfactory result has been found.

Separation of copper and iron from chloride media using Cyanex 921 in kerosene

The extraction and separation of Cu(II) and Fe(III) from HCl media using Cyanex 921 in kerosene were investigated. The effect of shaking time, aqueous phase acid concentration, Fe(III)/Cu(II) concentration, Cyanex 921 concentration, temperature and aqueous to organic phase ratio on the separation of Cu(II) and Fe(III) was studied using 0.1 mol/L Cyanex 921 in kerosene. Maximum separation was achieved from 2 mol/L HCl containing 0.001 mol/L Cu(II) and 0.005 mol/L Fe(III) with 0.1 mol/L Cyanex 921 in kerosene. Feasible separation of copper and iron was also possible from 5 mol/L HCl using 0.02 mol/L Cyanex 921.

Effect of operational parameters and internal recycle on rhenium solvent extraction from leach liquors using a mixer-settler

The extraction of rhenium from molybdenite roasting dust leach solution was performed using a mixer-settler extractor by tributyl phosphate (TBP) diluted in kerosene as the extractant. In the single-stage extraction experiments, effect of the aqueous to organic phase ratios, Qa/Qo, and the number of extraction stages, N, on the rhenium extraction was studied. It was found that using the phase ratio of 1:1 in a two-stage extraction, 87.5% depletion of rhenium was obtained. The comparison of experimental results with the continuous co-current extraction showed a good agreement. The effect of internal recycle of organic phase was investigated in the phase ratio of 1:1 by changing the flow rate ratio of recycle-to-fresh organic phase, Qro/Qfo. The optimum performance was achieved in the phase ratio, Qro/Qfo, equal to 3:7. It was found that improvement in the performance of the mixer-settler for the rhenium-TBP system can be obtained in the phase ratio of 1:1when Qro/Qfo = 3:7.

Separation and Recovery of Vanadium from Synthetic Leach Liquor Solutions Containing Iron, Calcium, Sodium, Aluminum, and Manganese by the Solvent Extraction Technique

Solvent extraction and separation of vanadium from other associated metals such as Ca, Na, Fe, Mn, Al from sulfate solutions using various extractants like phosphorus based and amine- based extractants were studied. And the other experimental conditions were optimized as follows: pH influence, extractants influence, 3rd phase studies, extraction equilibrium time, aqueous: organic phase ratios (A:O), water washings followed by sulfuric acid stripping process of metal from loaded organic phase were established. In the present study an analytical instrument, that is, an inductively coupled plasma optimal emission spectrometer (ICP-OES), was used for the vanadium and other metals analysis in aqueous solutions. The calculated separation factors (SFs) are presented and comparisons are made among all the experiments.

Sodium hydroxide regeneration of trialkylamine extractant containing inhibitors from corn stover prehydrolyzate by liquid–liquid extraction

Trialkylamine was an effective extractant for the removal of inhibitors from corn stover prehydrolyzate. Ethanol fermentability of the extracted prehydrolyzate was improved significantly. An approach for regeneration and valuable solutes (mainly acetic acid) recovery from such extractant was to back-extract the extractant containing inhibitors with sodium hydroxide. The influences of NaOH concentration, aqueous–organic phase ratio (A/O) on the extractant regeneration were investigated. The results indicated that 17.5g/l NaOH could remove 100% acetic acid at A/O of 1:1. 175g/l NaOH at A/O of 1:10 could also reach the same effect. Likewise, the results of 175g/l NaOH at A/O of 1:1 repeatedly back-extracted the extractant for ten cycles were the same as before. The performance of regenerated extractant on extraction the corn stover prehydrolyzate showed almost no change after reused ten cycles. So NaOH was very suitable to regenerate the extractant containing inhibitors in bioethanol industry.

Preparation and physicochemical characteristics of an allicin nanoliposome and its release behavior

Allicin, the main active component derived from a traditional flavoring agent - garlic, exerts a variety of biological effects. Unfortunately, its high potential in food processing is limited by its sensibility towards heat and alkaline conditions and its pungent smell. In this research, allicin nanoliposomes were prepared using reverse-phase evaporation method in an attempt to circumvent these shortcomings. The process conditions were optimized by response surface methodology, and the optimal parameters obtained were: lecithin-allicin ratio 3.70:1, lecithin-cholesterol ratio 3.77:1, ultrasonic time 3.40 min, organic phase-aqueous phase ratio 3.02:1. The experimental maximum of entrapment efficiency was 75.20 ± 0.62%, which was consistent with the predictive value (75.05%). Various physicochemical characteristics of allicin liposomes were determined and evaluated. The mean size of allicin nanoliposomes with well-defined spherical shape was 145.27 ± 15.19 nm and only a negligible difference was found after 30 days of storage. The allicin nanoliposomes gave a zeta potential of −40.10 ± 0.96 mV. Based upon the in vitro release profiles, allicin nanoliposomes exhibited a sustained-releasing potential in addition to the release behavior followed the first-order equation. The results indicated that the encapsulation of allicin into liposomes proved to be a promising technology for more widespread application.

Development of a Validated RP-HPLC Method for Simultaneous Estimation of Metformin Hydrochloride and Rosuvastatin Calcium in Bulk and In-House Formulation

A simple, precise, rapid, selective, and economic reversed phase high-performance liquid chromatography (RPHPLC) method has been established for simultaneous analysis of Metformin hydrochloride and Rosuvastatin in bulk powder and In-House Formulation on a Phenomenex C18 (250×4.6 mm i.d) chromatographic column equilibrated with mobile phase containing Acetonitrile/0.02 M Sodium dihydrogen o-phosphate. Experimental conditions such as pH of mobile phase, ratio of organic phase, flow rate, wavelength, etc. were critically studied and the optimum conditions were selected. Efficient chromatographic separation was achieved with mobile phase containing combination of Phosphate buffer pH 2.8 and Acetonitrile in ratio of 65:35(v/v) adjusted to pH 3.8 at flow rate of 1.0 ml/min and eluents were monitored at 252 nm. 20 μl of sample was injected into chromatographic system and the total run time was 10 min. The retention time for Metformin and Rosuvastatin were 2.147 min and 3.80 min respectively. The method was linear in the range of 5μg mL-1to 30μg mL-1and 0.4 μg mL-1to2.4μg mL-1for Metformin and Rosuvastatin respectively. The proposed method was successfully applied to the analysis of Metformin and Rosuvastatin in bulk and in-house formulation without interference from other additives. The developed method was validated according to ICH guidelines. Linearity, regression value, recovery and % RSD of intra and interday precision values were found within the limits and the method was found to be satisfactory. This validated HPLC procedure is economic, sensitive, user-friendly and less time consuming than other chromatographic procedures.

Uranium (VI) Removal from Flood Water Using Trioctyl Amine (TOA), At Abu Rusheid Area, South Eastern Desert, Egypt

Flash floods are considered natural disasters that can cause casualties and demolishing of infrastructures. The flash flood takes place over Abu Rusheid in 29 November 2011. After one month from the falling of flood, ten flooding water samples were collected from the cavities in the mountain at Abu Rusheid area, South Eastern Desert, Egypt. The salinity ranges between 380 and 1460 ppm, while pH ranges between 7.1 and 8.1. Trioctyl amine (TOA) dissolved in kerosene has been chosen for removal both of uranium and thorium. Different parameters were carried out testing the following variables: different diluents, TOA concentrations, aqueous to organic phase ratio, shaking time, temperature, and different stripping agents. The factors studied were followed by application of the removal system to determine the uranium and thorium from flooding water samples. The uranium concentration in the studied area were ranged between 172 ppb and 1012 ppb. While, thorium was ranged between 98 ppb and 524 ppb. Meanwhile, the dissolution and leaching (%) of uranium and thorium in flood water samples after one month from the falling of flood in the studied area are ranging between 0.032 - 0.9 % and 0.016 - 0.36 %. After chemical treatment of the flood water was observed that, the remaining elements of uranium and thorium are very few. We recommend not to use those waters from flooding which contain a small concentration of uranium.

Recovery of methylene blue from aqueous solution by liquid–liquid extraction

The aim of this study is the removal and recovery of methylene blue (MB) from wastewater. MB is one of the most commonly used substances for dyeing cotton, wood, and silk. Though MB is not strongly hazardous, it can cause some harmful effects where acute exposure to MB may cause increased heart rate, vomiting, shock, cyanosis, jaundice and quadriplegia and tissue necrosis in human. So, we selected the MB for solvent/liquid–liquid extraction study. MB is the cationic dye, so it requires an anionic carrier for extraction purpose. Salicylic acid acts as an anionic carrier in this study. Removal of MB using salicylic acid in benzene was studied. The efficiency of dye extraction increased with decreasing dye concentration. The extracted dye in the organic phase can be back-extracted into 1M oxalic acid solutions. The experimental parameters examined were salicylic acid concentration, effects of diluents, effect of pH, effect of initial dye concentration, effect of equilibrium time, aqueous to organic phase ratio, and various stripping agents. Real effluent was also studied under optimized condition and satisfactory result has been found.

Development and Characterisation of Ursolic Acid Nanocrystals Without Stabiliser Having Improved Dissolution Rate and In Vitro Anticancer Activity

Ursolic acid (UA), which is a natural pentacyclic triterpenoid, has the potential to be developed as an anticancer drug, whereas its poor aqueous solubility and dissolution rate limit its clinical application. The aim of the present study was to develop UA nanocrystals to enhance its aqueous dispersibility, dissolution rate and anticancer activity. Following the investigation on the effects of stabiliser, the ratio of organic phase to aqueous solution and drug concentration, the UA nanocrystals without stabiliser were successfully prepared by anti-solvent precipitation approach. The nanocrystals maintained similar crystallinity with particle size, polydispersion index and zeta potential values of 188.0 ± 4.4 nm, 0.154 ± 0.022, and -25.0 ± 5.9 mV, respectively. Compared with the raw material, the UA nanocrystals showed good aqueous dispensability and a higher dissolution rate, and they could be completely dissolved in 0.5% SDS solution within 120 min. Moreover, the suspension of UA nanocrystals was physically stable after storage at 4°C for 7 weeks. By inducing G2/M phase cell cycle arrest, the UA nanocrystals significantly induced stronger cell growth inhibition activity against MCF-7 cells compared with free drug in vitro, although the uptake of free UA was approximately twice higher than that of the UA nanocrystals. The UA nanocrystals may be used as a potential delivery formulation for intravenous injection with enhanced dissolution velocity and anticancer activity.

PH-Sensitive Micelles for Targeted Drug Delivery Prepared Using a Novel Membrane Contactor Method

A novel membrane contactor method was used to produce size-controlled poly(ethylene glycol)-b-polycaprolactone (PEG-PCL) copolymer micelles composed of diblock copolymers with different average molecular weights, Mn (9200 or 10,400 Da) and hydrophilic fractions, f (0.67 or 0.59). By injecting 570 L m(-2) h(-1) of the organic phase (a 1 mg mL(-1) solution of PEG-PCL in tetrahydrofuran) through a microengineered nickel membrane with a hexagonal pore array and 200 μm pore spacing into deionized water agitated at 700 rpm, the micelle size linearly increased from 92 nm for a 5-μm pore size to 165 nm for a 40-μm pore size. The micelle size was finely tuned by the agitation rate, transmembrane flux and aqueous to organic phase ratio. An encapsulation efficiency of 89% and a drug loading of ~75% (w/w) were achieved when a hydrophobic drug (vitamin E) was entrapped within the micelles, as determined by ultracentrifugation method. The drug-loaded micelles had a mean size of 146 ± 7 nm, a polydispersity index of 0.09 ± 0.01, and a ζ potential of -19.5 ± 0.2 mV. When drug-loaded micelles where stored for 50 h, a pH sensitive drug release was achieved and a maximum amount of vitamin E (23%) was released at the pH of 1.9. When a pH-sensitive hydrazone bond was incorporated between PEG and PCL blocks, no significant change in micelle size was observed at the same micellization conditions.

Quantitative structure–ion intensity relationship strategy to the prediction of absolute levels without authentic standards

The lack of authentic standards represents a major bottleneck in the quantitative analysis of complex samples. Here we propose a quantitative structure and ionization intensity relationship (QSIIR) approach to predict the absolute levels of compounds in complex matrixes. An absolute quantitative method for simultaneous quantification of 25 organic acids was firstly developed and validated. Napierian logarithm (LN) of the relative slope rate derived from the calibration curves was applied as an indicator of the relative ionization intensity factor (RIIF) and serves as the dependent variable for building a QSIIR model via a multiple linear regression (MLR) approach. Five independent variables representing for hydrogen bond acidity, HOMO energy, the number of hydrogen bond donating group, the ratio of organic phase, and the polar solvent accessible surface area were found as the dominant contributors to the RIIF of organic acids. This QSIIR model was validated to be accurate and robust, with the correlation coefficients (R2), R2 adjusted, and R2 prediction at 0.945, 0.925, and 0.89, respectively. The deviation of accuracy between the predicted and experimental value in analyzing a real complex sample was less than 20% in most cases (15/18). Furthermore, the high adaptability of this model was validated one year later in another LC/MS system. The QSIIR approach is expected to provide better understanding of quantitative structure and ionization efficiency relationship of analogous compounds, and also to be useful in predicting the absolute levels of analogous analytes in complex mixtures.

Solvent Extraction of Cyclohexanecarboxylic Acid From Waste Fluid by Using a Mixture of Toluene and 1-Octanol

Solvent extraction studies have been carried out for the recovery of cyclohexanecarboxylic acid (CCA) from simulated waste fluid. Influences of various parameters including extractant types, pH of the solution, equilibration time, and initial concentrations of CCA, etc., were studied. A mixture of toluene and 1-octanol (90:10, v/v) was found suitable for the extraction. The results showed that solution pH had a great effect on the distribution ratio, and CCA could be efficiently extracted when the pH was lower than 3.5. The extraction was found quite rapidly. The distribution ratio decreased as the initial concentration of CCA increased. The stripping rate of CCA using sodium hydroxide as stripping agent was found to be increased with the increase of alkali concentration. After back extraction once, more than 98% stripping efficiency was achieved with 0.8 mol/L sodium hydroxide solution at aqueous to organic phase (A/O) ratio 1:1 when CCA concentration was lower than 38.3 g/L. The practical extraction process was carried out for the waste fluid (concentration of CCA 36.5 g/L) discharged in the production of caprolactam from toluene. After four extraction stages at A/O ratio 1:1, the cumulative extraction recovery reached 99.3%. The practical stripping efficiency from loaded organic phase reached 98.2% in one single stage.

Preparation of polyacrylamide based microgels with different charges for drug encapsulation

The unique physicochemical properties of hydrogels have attracted considerable attention in their drug storage and delivery applications. Herein, a series of acrylamide based hydrogels with different charges (cationic, neutral, and anionic) under different pH (1, 7, and 13) were prepared via an inverse emulsion polymerization process. The effects of pH and aqueous to organic phase (w/o) ratio on the size of the produced hydrogels were studied. Fluorescein was used as the model drug to assess and optimize the encapsulation efficiency of the hydrogels. Optical microscopy and confocal fluorescence microscopy were carried out to examine the existence and distribution of fluorescein inside the hydrogels. It was found that the hydrogels were swollen to the greatest extent at pH=13 and their size increased with decreasing w/o ratio. Fluorescein was molecularly dispersed within the cationic and anionic hydrogels at pH=13 with an encapsulation efficiency of ∼45wt%. This study provides a convenient method to prepare hydrogels with the required properties and demonstrates the potential of using hydrogels to store and stabilize therapeutics.

Applicability of LC–MS/MS to optimize derivatization of topiramate with FMOC-Cl using reacted/intact drug ratio

Topiramate is an antiepileptic agent, which is structurally different from the other anticonvulsants. The drug has no UV-Vis absorption or emits fluorescence. Thus for its analysis using high performance liquid chromatography (HPLC) with conventional UV or fluorescence detectors, the drug should be derivatized with a suitable reagent. In previous study using fluorenylmethyl chloroformate (FMOC-Cl) and HPLC coupled with fluorescence detector, we reported an analytical method for derivatization and analysis of the drug in human serum. In this method, several factors including time and temperature of the reaction, pH and concentration of the used buffer, ratio of organic phase in the medium and removal of the reagent excess by glycine should be optimized to obtain maximum yield of the product. In HPLC coupled with fluorescence detector, there is not any signal from intact topiramate and only the final product (FMOC-topiramate) is appeared. Thus to optimize the reaction conditions for obtaining the highest derived yield, intensity of the final product peak is considered as a criteria for progression of the reaction. In LC-MS/MS system however, both free and reacted topiramate are visible in observed spectra. In the present study reaction of the drug with FMOC-Cl was re-optimized using LC-MS/MS technique on the basis of reacted/free topiramate ratio as the new and more accurate index. The results showed that, ratio of organic/aqueous phase has a dominant effect on the reaction, the most efficient temperature is 70°C and the reaction is reversed following addition of the glycine.

Optimization of Fabrication Parameters to Prepare Tea Catechin-Loaded Liposomes using Response Surface Methodology

The purpose of this study was to optimize the formulation of tea catechin-loaded nano-liposomes using response surface methodology. Response surface methodology based on central composite rotatable design has been successfully used to model and optimize biochemical and biotechnological processes. The mass ratio of phosphatidylcholine and cholesterol (1-3), catechin concentration (3-5 mg/mL), pH values of phosphate buffer solution (6-7) and the volume ratio of organic phase and aqueous phase (2-4) were selected as independent variables with encapsulation efficiency and particle size as dependent variables. For each response, a second-order polynomial model was developed using multiple linear regression analysis. Applying a desirability function method the optimum parameters were: phosphatidylcholine to cholesterol mass ratio of 2.17, catechin concentration of 5 mg/mL, pH values of phosphate buffer solution of 6.62 and organic phase to aqueous phase volume ratio of 3.05. At this optimum point, particle size and encapsulation efficiency were found to be 220 nm and 60.18%, respectively. Furthermore, leakage ratio of nano-liposomes was used to determine the influence of storage period.

Biotransformation of Indole to Indigo by the Whole Cells of Phenol Hydroxylase Engineered Strain in Biphasic Systems

Biotransformation of indole to indigo in liquid-liquid biphasic systems was performed in Escherichia coli cells expressing phenol hydroxylase. It was suggested that indole could inhibit the cell growth even at low concentration of 0.1g/L. The critical Log P for strain PH_(IND) was about 5.0. Three different solvents, i.e., decane, dodecane, and dioctyl phthalate, were selected as organic phase in biphasic media. The results showed that dodecane gave the highest yield of indigo (176.4mg/L), which was more than that of single phase (90.5mg/L). The optimal conditions for biotransformation evaluated by response surface methodology were as follows: 540.26mg/L of indole concentration, 42.27% of organic phase ratio, and 200r/min of stirrer speed; under these conditions, the maximal production of indigo was 243.51mg/L. This study proved that the potential application of strain PH_(IND) in the biotransformation of indole to indigo using liquid-liquid biphasic systems.