Solvent Extraction Phase Research Articles

Effect of High Pressure Homogenization on Aqueous Phase Solvent Extraction of Lipids from Nannochloris Oculata Microalgae

The ability to extract lipids from high-moisture Nannochloris Oculata algal biomass disrupted with high pressure homogenization was investigated. During the first phase, the effect of high pressure homogenization (system pressure and number of passes) on disrupting aqueous algae (of different concentrations and degree of stress) was investigated. Se-condly, the effect of degree of cell wall disruption on the amount of lipids extracted with three solvents, namely: hexane, dichloromethane and chloroform, were compared. Studies reveled that high pressure homogenization is effective on cell disruption while the amount of system pressure being the most significant factor affecting the degree of cell breakage. Al-though the number of passes had some impact, the level of disruption seemed to level-off after a certain number of passes. The study revealed that slightly polar solvents (such as chloroform and dichloromethane) performed better in aqueous-phase lipid extractions as compared to hexane. Also, it was revealed that it was not necessary to disrupt the algal cells completely to achieve appreciable levels of lipid yields. In fact, conditions that exerted only 20% of the cells to completely disrupt, allowed sufficient damage to liberate most of the lipids contained in the remainder of the cells.

Photocatalytic Desulfurization of Waste Tire Pyrolysis Oil

Waste tire pyrolysis oil has high potential to replace conventional fossil liquid fuels due to its high calorific heating value. However, the large amounts of sulfurous compounds in this oil hinders its application. Thus, the aim of this research was to investigate the possibility to apply the photo-assisted oxidation catalyzed by titanium dioxide (TiO2, Degussa P-25) to partially remove sulfurous compounds in the waste tire pyrolysis oil under milder reaction conditions without hydrogen consumption. A waste tire pyrolysis oil with 0.84% (w/w) of sulfurous content containing suspended TiO2 was irradiated by using a high-pressure mercury lamp for 7 h. The oxidized sulfur compounds were then migrated into the solvent-extraction phase. A maximum % sulfur removal of 43.6% was achieved when 7 g/L of TiO2 was loaded into a 1/4 (v/v) mixture of pyrolysis waste tire oil/acetonitrile at 50 °C in the presence of air. Chromatographic analysis confirmed that the photo-oxidized sulfurous compounds presented in the waste tire pyrolysis oil had higher polarity, which were readily dissolved and separated in distilled water. The properties of the photoxidized product were also reported and compared to those of crude oil.

Fast gas chromatography with solid phase extraction clean-up for ultratrace analysis of pesticide residues in baby food

A sample preparation method based on single solvent phase extraction and solid-phase extraction (SPE-NH 2) clean-up is studied in combination with fast capillary gas chromatography (GC) to determine 18 selected pesticides belonging to various chemical classes in apples, the common raw material for baby food production and baby food, at the concentration level ≤10 μg/kg maximum residual limit (MRL). Possibilities of mass spectrometry (MS) detector and electron capture detector (ECD) in fast gas chromatography (GC) of samples with complex matrice at ultra trace levels of pesticide residues were studied and compared. MS detection in single ion monitoring (SIM) mode provided higher selectivity compared to ECD. Optimisation of extraction as well as the simplifying of the whole process of sample preparation was carried out. Recoveries obtained at concentration level of 5 μg/kg (the required value for limit of quantification (LOQ) in baby food) were >90%, except of dimethoate (77.7%) and captan (46.4%) with MS detection. The obtained LOQs were at least 1 order lower than 5 μg/kg for the majority of compounds. The repeatability of gas chromatography–mass spectrometry (GC–MS) measurements of the matrix matched standards expressed as relative standard deviation was <11% except of captan and cypermethrin.

Determination of fecal sterols in the sediments of different wastewater outputs by GC-MS

An improved method for the analysis of fecal sterols in sediments was applied to distinguish livestock wastewater, domestic sewage, and industrial wastewater pollution in the receiving waters of Taiwan’s rivers. The method included direct saponification, solvent phase extraction, derivatization with N-methyl-N-trimethyltrifluoroacetamide and catalyst, and separation by gas chromatography with an HP-50+ capillary column, followed by qualitative and quantitative analysis by mass spectrometry. Recoveries of nine sterols by this method were 78–89%. The indicators of biopollution markers ((coprostanone × coprostanol)/epicoprostanol) in different sources of wastewater effluents were calculated as human 0.913 ± 0.251, pig 0.224 ± 0.135, cow 0.023 ± 0.001, duck 0.007 ± 0.001; such indicators are feasible for distinguishing between different animal sources of fecal pollution in water.

A fast and accurate method to measure both oxidative stress and vitality in a single organ slice

Increased oxidative stress does not necessarily cause an organ to suffer from oxidative damage, since antioxidant systems to protect organs are present. However, when a decrease in the vitality of an organ coincides with an increase in oxidative stress, increased oxidative damage is likely. A sequential method for the measurement of both energy status and oxidative stress in the same sample has been developed. The novelty of this method lies in the combination of efficiency and accuracy. Nucleotides and malondialdehyde (MDA) of 80 different samples can be released in a perchloric environment with ultrasonic treatment instead of homogenization. Malondialdehyde concentration can be measured after complexing with 2,4-dinitrophenylhydrazine without any homogenization, solvent phase extraction, and centrifugation steps. Yields of both malondialdehyde and nucleotides were similar to those of the homogenization procedure. Detection limit was 141 fmol for MDA and 22.5 pmol for the nucleotides. Furthermore, the stability of the malondialdehyde-2,4-dinitrophenylhydrazine complex after 3 weeks at −20 °C is excellent 99.7% (±5.6). Nucleotides are stable for the same time period. Spiking of samples with MDA and nucleotides showed good recoveries (102.5% (±5.0) and 99.8% (±7.9), respectively). The present data show an accurate method to measure both the energy status and the oxidative stress in a single organ slice with a minimum of effort and time.

Redox effects on resin extraction of herbicides from soil

Relative soil aeration affects the surfaces upon which pesticides adsorb and non-ionic resins offer a means of observing and evaluating this factor. A non-ionic resin extractor, developed for pesticide extraction under reducing conditions, was used to adsorb a fraction of the reversibly adsorbed (active portion) herbicides. The extractor consists of cleaned XAD-2 resin encased in a dialysis membrane composed of regenerated cellulose. Anaerobiosis was achieved by incubating soil suspensions with glucose under a 95% N 2–5% H 2 environment until the redox potential reached −150 mV. Nine soils with a range of physical and chemical characteristics were examined for atrazine, metribuzin, and alachlor content. Amounts of atrazine, metribuzin, and alachlor extracted from soil ranged to 100, 140, and 75 ng g −1, respectively. Resin extractions (RE) conducted under aerobic conditions recovered about 25–50% of the pesticide extractable with conventional solid phase solvent extraction at 60 °C (SPE 60). Under anaerobic conditions, equal amounts of atrazine were extracted with RE and SPE 60. Slightly less metribuzin was recovered under anaerobic extraction with the exception of those soils lacking detectable amounts by SPE 60. Larger amounts of alachlor were extracted with resins under anaerobic conditions than under aerobic conditions but the amounts were not correlated with those determined by SPE 60. Large amounts of soil organic matter were solublized under anaerobiosis and smaller molecular weight material was extracted with the herbicides. The nature and amounts of co-extracted organic matter varied among soils. RE directly from soil suspensions enabled simultaneous determination of all three herbicides.

Effect of Osmotic Pressure in the Solvent Extraction Phase on BSA Release Profile from PLGA Microspheres

This study investigated the influence of osmotic pressure in the organic solvent extraction phase on release profile of bovine serum albumin (BSA) from poly(lactide-co-glycolide) (PLGA) microspheres. BSA-loaded PLGA microspheres with a target load of 10% were prepared by a double emulsion phase separation method. All the microsphere batches were fabricated in the same conditions except that in the organic solvent (CH2Cl2) evaporation step. Different concentrations of NaCl (0, 1.8, and 3.6%) or sucrose (20%) were used to generate a range of osmotic pressures in the extraction aqueous phase. These microspheres were characterized for incorporation efficiency, surface and internal morphology, particle size, protein stability, and in vitro release. The microspheres were spherical with particle size ranging from 16.8 to 27.8 μm. Higher osmotic pressure resulted in a denser internal structure although similar nonporous surface morphology was observed with all batches. No significant difference in encapsulation efficiency existed from batch to batch (87–94%). Sodium dodecyl sulfate–polyamide gel electrophoresis showed that BSA integrity was well retained. The release profile of the batch prepared with only water as the continuous (solvent extraction) phase exhibited a 79% burst release in the first 24 hr followed by a plateau and then a little release after 21 days. In the presence of NaCl or sucrose, the burst effect significantly decreased with increase in osmotic pressure in the extraction aqueous phase, which was then followed by sustained release for 35 days. A mass balance was made when the release terminated. Therefore, in the organic solvent extraction and evaporation step, increasing the osmotic pressure in the aqueous phase both reduced the burst release from the microspheres and improved the subsequent sustained release profile.

Mechanistic study of trivalent europium transport through supported liquid membranes (SLMs) and a novel immobilized phase solvent extraction (IPSE) system

The extraction of Eu(III) from medium acidic nitrate solutions with supported liquid membranes (SLMs) was studied with the cavitand-based Carriers 1– 3. The experimental time-dependent Eu(III) concentrations were on-line monitored with a radiotracer, the concentration profiles can be described with a non-steady state model. The membrane diffusion coefficients D m were directly determined from the experimental data. Evaluation of the rate-limiting step showed that aqueous diffusion plays a significant role and that the SLM and the solvent extraction (SX) models are in good agreement. The new immobilized phase solvent extraction (IPSE) system is based on the SLM principle and is a versatile technique for (semi-)continuous extraction of cations.

An Attempt to Theoretically Predict Third-Phase Formation in the Dimethyldibutyltetradecylmalonamide (DMDBTDMA)/Dodecane/Water/Nitric Acid Extraction System

ABSTRACT The formation of a third phase in solvent extraction (due to splitting of the organic phase into two layers) often occurs when the aqueous phase is highly concentrated in acids. This has been reported with the extraction system dimethyldibutyltetradecylmalonamide (DMDBTDMA)/n-dodecane/water/nitric acid, both in the presence and absence of metal ions. Whereas many experimental efforts have been made to investigate the effects of different parameters on third-phase formation, very few attempts have been made to predict this phenomenon on theoretical grounds. Because the part played by aggregation of the extractant molecules is recognized, we propose a new predictive approach based on the use of the Flory-Huggins theory of polymer solutions, which had been successfully applied for the prediction of phase separation phenomena in nonionic surfactant solutions. We show that this model can provide an excellent prediction of the demixing curve (in the absence of metal ions) when establishing the relation between the interaction parameter ×12 calculated from this theory and the nitric acid content of the aqueous phase. Apparent values of the solubility parameter δ2 of the diamide extractant at different acid loadings have been calculated, from which the effect of the nature of the diluent can also be very nicely predicted.

An Attempt to Theoretically Predict Third-Phase Formation in the Dimethyldibutyltetradecylmalonamide (DMDBTDMA)/Dodecane/Water/Nitric Acid Extraction System

ABSTRACT The formation of a third phase in solvent extraction (due to splitting of the organic phase into two layers) often occurs when the aqueous phase is highly concentrated in acids. This has been reported with the extraction system dimethyldibutyltetradecylmalonamide (DMDBTDMA)/n-dodecane/water/nitric acid, both in the presence and absence of metal ions. Whereas many experimental efforts have been made to investigate the effects of different parameters on third-phase formation, very few attempts have been made to predict this phenomenon on theoretical grounds. Because the part played by aggregation of the extractant molecules is recognized, we propose a new predictive approach based on the use of the Flory-Huggins theory of polymer solutions, which had been successfully applied for the prediction of phase separation phenomena in nonionic surfactant solutions. We show that this model can provide an excellent prediction of the demixing curve (in the absence of metal ions) when establishing the relation...

Enhancement in Extraction Rates by Addition of Organic Acids to Aqueous Phase in Solvent Extraction of Rare Earth Metals in Presence of Diethylentriamine-Pentaacetic Acid.

It is well known that the selectivity of rare earth metals by solvent extraction is increased by the addition of a chelating agent such as diethylenetriaminepentaacetic acid (DTPA) in the aqueous phase. One of the disadvantages of this method is the decrease in extraction rates due to complexation in the aqueous phase. In this paper, further addition of organic acids to the aqueous phase was examined for the purpose of enhancing the extraction rates in solvent extraction with DTPA. The addition of several kind of organic acids such as formic acid, acetic acid, malonic acid, lactic acid and citric acid was investigated for a Er/Y separation system. A remarkable enhancement in extraction rates was observed with a slight decrease in the selectivity by the addition of citric acid or lactic acid. Extraction rates in the presence of both DTPA and citric acid increased with the increase in citric acid concentration and with the increase in proton concentration. A 150 times enhancement in extraction rates was found in the low proton concentration condition. In order to analyze the extraction rates and selectivities obtained, mass transfer equations were presented by considering both the dissociation reaction of rare earth metal-DTPA complexes and the complex formation between rare earth metal and organic acid in the aqueous phase. The experimental data were analyzed by these equations.

Functional properties and amino-acid composition of solvent-extracted flaxseed meals

The functional properties of solvent-extracted flaxseed meals were studied. The solvent systems employed consisted of hexane and absolute or 95% (v/v) alkanol with or without 10% (w/w) ammonia. Approximately 55% of the total nitrogen-containing compounds present in the meals were dissolved in water. Meals extracted with methanol-ammonia-water/hexane had the highest nitrogen-solubility index. The minimum solubility of nitrogenous compounds in hexane-extracted and methanol-ammonia-water/hexane-extracted meals occurred between pH 3·0 and 3·5. Flaxseed meals had a high water-adsorption value, and the two phase solvent extraction did not influence it. Fat adsorption of the meals was influenced by the presence of ammonia in the extraction system, and the pH of these meals was increased by nearly one unit. Solvent-extracted flaxseed meals had improved emulsifying and foaming properties. Extraction with methanol-ammonia-water/hexane did not change the amino-acid composition of flaxseed meals.