Separation Of Aqueous Phase Research Articles

Pressure-driven liquid-liquid separation in Y-shaped microfluidic junctions

On-chip phase separation of multiphase microflows at the divergence point of Y-shaped microfluidic junctions is an effective way for integrating continuous microstructured devices. In this study, flow pattern maps of various solvent pairs based on the volumetric flow rates of both phases have been drawn experimentally and compared with numerical prediction to investigate the effective domain for which complete phase separation occurred. Furthermore, sufficient separation of aqueous and organic phases at the end of the microchannel was achieved by controlling the pressure difference at the liquid-liquid interface via loading back-pressure on the organic phase. A mathematical model based on interfacial pressure balance was derived. It was found that organic phase outlet tube should be kept between the upper and lower values calculated from the model. Only narrow discrepancy between the model and experimental observation can be seen in using viscous organic solvents.

Separation of external aqueous phase from o/w nanoemulsions

The aim of this study is to develop a simple, reliable, timesaving and cost-effective method for separation of the external aqueous phase from o/w nanoemulsions. The method is based on centrifugation through a hydrophilic membrane. Five o/w nanoemulsions (droplet size of 20–200nm) with radio-labeled C18 triglyceride were prepared. These nanoemulsions were placed in tubes with cellulose membranes (10–50K molecular weight cut-off) and centrifuged at 250–3000g for 5–15min. The filtrates were analyzed for the presence of lipid droplets and radioactivity. The applicability of this method was tested on FITC-dextran-loaded nanoemulsion (FITC-dextran was expected to be in the lipid droplets) and a blank nanoemulsion mixed with FITC-dextran (FITC-dextran was expected to be in the external aqueous phase). The results show that no droplets were detected in the filtrate. The radioactivity in the filtrate was in the range of 0.3–2.9%. The volume of the filtrate increased with increase in the membrane pore size, centrifugal force and time, and decrease in droplet size. There was 41.6±4.2% and 98.4±0.8% FITC-dextran in the aqueous phase of the FITC-dextran-loaded nanoemulsion and the blank nanoemulsion mixed with FITC-dextran, respectively. In conclusion, centrifugation with hydrophilic membrane is an efficient and convenient method for the separation of the external aqueous phase from o/w nanoemulsions with droplet sizes in the range of 20–200nm.

Determination of chloride in brazilian crude oils by ion chromatography after extraction induced by emulsion breaking

The present paper reports on the development of a novel extraction induced by emulsion breaking (EIEB) method for the determination of chloride in crude oils. The proposed method was based on the formation and breaking of oil-in-water emulsions with the samples and the consequential transference of the highly water-soluble chloride to the aqueous phase during emulsion breaking, which was achieved by centrifugation. The determination of chloride in the extracts was performed by ion chromatography (IC) with conductivity detection. Several parameters (oil phase:aqueous phase ratio, crude oil:mineral oil ratio, shaking time and type and concentration of surfactant) that could affect the performance of the method were evaluated. Total extraction of chloride from samples could be achieved when 1.0g of oil phase (0.5g of sample+0.5g of mineral oil) was emulsified in 5mL of a 2.5% (m/v) solution of Triton X-114. The obtained emulsion was shaken for 60min and broken by centrifugation for 5min at 5000rpm. The separated aqueous phase was collected, filtered and diluted before analysis by IC. Under these conditions, the limit of detection was 0.5μgg−1 NaCl and the limit of quantification was 1.6μgg−1 NaCl. We applied the method to the determination of chloride in six Brazilian crude oils and the results did not differ statistically from those obtained by the ASTM D6470 method when the paired Student-t-test, at 95% confidence level, was applied.

Stable isotope (B, H, O) and mineral-chemistry constraints on the magmatic to hydrothermal evolution of the Varuträsk rare-element pegmatite (Northern Sweden)

The internal evolution of the Varuträsk rare-element pegmatite (Skellefte District, Northern Sweden) has been investigated using stable isotope (B, H, O) geochemistry of tourmaline and coexisting micas, feldspar and quartz. Varuträsk is a classic and typical example of highly fractionated LCT-type pegmatites, with a pronounced concentric zoning pattern composed of well-developed border, wall and intermediate zones and a quartz core. The pegmatite displays considerable rare-element enrichment, culminating in the formation of albite-lepidolite and pollucite units in the innermost zones. Major and trace element variations in tourmaline from the main pegmatite zones correlate well with the internal zoning pattern. Mineral compositions record an abrupt change in fractionation trends between the barren outer and intermediate zones and the inner, late-stage assemblages that carry rare-element mineralization. This change is also shown by the B-isotope variations of tourmaline. Early and mid-stage tourmalines record a systematic increase in δ11B from −14.6‰ to −6.2‰ which can be explained by closed-system melt-mineral isotope fractionation whereby crystallization of large amounts of muscovite preferentially removes 10B from the residual melt. In contrast, tourmaline from late-stage assemblages in the inner zones and cross-cutting veinlets shows a reversal in the B isotope trend, with a decrease in δ11B from −8‰ to −14.1‰. This reversal cannot be explained by mineral-melt isotope fractionation, but requires fluid-melt partitioning and partial fluid loss. Hydrogen isotope variations in mica support this model. The systematic increase in δD from −75‰ in the outer zones (muscovite) to −63‰ and −53‰ in the inner zones (Li-micas) cannot be explained by closed-system variations in temperature or melt-mica fractionation, but it is consistent with late fluid exsolution. Oxygen isotope compositions of tourmaline (δ18O from 9.7‰ to 11.6‰), quartz (13.3‰ to 14‰) and mica (10.3‰ to 11.3‰) show good agreement with equilibrium partitioning and yield temperatures in the range 450°C to 600°C. Combining this with the stability fields of Li-aluminosilicates petalite and spodumene indicates crystallization pressures of 2–3kbar. Taken together, the stable isotope and mineral chemistry data demonstrate that rare-element enrichment in the innermost fractionated assemblages in the Varuträsk pegmatite was associated with the transition from purely magmatic crystallization to conditions where a separate aqueous fluid phase became important.

Development and validation of a high performance liquid chromatographic–mass spectrometry method for the simultaneous quantification of 10 trichothecenes in ultra-high temperature processed cow milk

An LC–MS/MS (QqQ) method has been developed and validated for simultaneous determination of the following trichothecenes in UHT cow milk: nivalenol (NIV), deoxynivalenol (DON), deepoxy-deoxynivalenol (DOM-1), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), neosolaniol (NEO), diacetoxyscirpenol (DAS), fusarenon X (FUS-X), T-2 and HT-2 toxins. Sample treatment is simple and based on the extraction with acetonitrile (ACN), acidified with 0.2% formic acid, followed by a purification process, adding sodium acetate to the ACN/water extract in order to separate aqueous phase and, consequently, polar components of the milk. Validation of the method for all the 10 mycotoxins was successful; validation parameters taken into account were as follows: limits of detection (LOD) and quantification (LOQ), linearity, precision (within-day and between-day variability), recovery, matrix effect and stability. The LODs were 10.1, 2.5, 1.5, 1.9, 0.1, 0.5, 1.0, 0.08, 0.4 and 0.05ng/mL for NIV, DON, DOM-1, FUS-X, NEO, 3-ADON, 15-ADON, DAS, HT-2 and T-2, respectively. Mean recovery values (obtained in intermediate precision conditions) were between 63.5 and 75.8 (RSDR≤15%) for all the mycotoxins. All the mycotoxins suffered from matrix effects, especially DON.

A fluorosurfactant and photoreducible Cu(II)-tren click catalyst: surfactant and catalytic properties at liquid/liquid interfaces.

The fluorous copper(ii) complex [Cu(II)(trenRf6)3-benzoylbenzoate]3-benzoylbenzoate 2, composed of a highly fluorophilic tris(2-aminoethyl)amine ligand and two 3-benzoylbenzoates as counterions and photosensitizers, was synthesized from the dinuclear complex [Cu(3-benzoylbenzoate)4(H2O)2] 1 which was characterized by X-ray analysis. Complex 2, which is highly soluble in perfluorocarbons, moderately soluble in organic solvents while insoluble in water, was found to be a very effective fluorosurfactant. At the air/water interface it formed a Langmuir film, which upon compression slowly collapsed at about 28 mN m(-1), which corresponds to a surface area of about 220 Å(2) per molecule. Tensiometric measurements revealed that 2 is more rapidly adsorbed at the diisopropyl ether (DIPE)/water interface than the perfluorodecalin (PFD)/water one, leading to a decrease of the interfacial tensions of about 14 mN m(-1) and 40 mN m(-1), respectively. Photoreduction of 2 occurs effectively in H-donating solvents such as THF and DIPE, or even in PFD ensuring that an electron donor, such as propargyl alcohol, is present in a separate aqueous phase. Complex 2, when combined with light (365 nm), catalyzes the click reaction between the azide 3 and alkyne 4 under homogeneous conditions (methanol), to afford the disaccharide 5. Under emulsified biphasic DIPE/water or PFD/water conditions, the reactions proceeded well. However, it was shown that a fast and significant amount of copper and 3-benzoylbenzoate counterion was transferred into the aqueous phase, and that most of the catalysis could be ascribed to a copper species solubilised in the aqueous phase, and not to the fluorous copper complex accumulated at the interface.

Water-fluxed melting of the continental crust: A review

Abstract Water-fluxed melting, also known as fluid- or water-present melting, is a fundamental process in the differentiation of continents but its importance has been underestimated in the past 20 years during which research efforts focused mostly on dehydration melting reactions involving hydrate phases, in the absence of a separate aqueous phase. The presence of a free aqueous phase in anatectic terranes influences all major physical and chemical aspects of the melting process, from melt volumes, viscosity and ability to segregate from rock pores, to melt chemical and isotopic composition. A review of the literature shows that melting due to the fluxing of aqueous fluids is a widespread process that can take place in diverse tectonic environments. Active tectono-magmatic processes create conditions for the release of aqueous fluids and deformation-driven, transient high permeability channels, capable of fluxing high-temperature regions of the crust where they trigger voluminous melting. Water-fluxed melting can be either congruent in regions at the water-saturated solidus, or incongruent at suprasolidus, P–T conditions. Incongruent melting reactions can give rise to peritectic hornblende, or to nominally anhydrous minerals such as garnet, sillimanite or orthopyroxene. In this case, the presence of an aqueous phase is indicated by a mismatch between the large melt fraction generated and the much smaller fractions predicted in its absence. The relatively small volumes of aqueous fluids compared to that of rocks imply that melting reactions are generally rock buffered. Fluids tend to move upwards and down temperature. However, there are cases in which pressure gradients drive fluids up temperature, potentially fluxing suprasolidus terranes. Crustal regions at conditions equivalent to the water-saturated solidus represent a natural impediment to the up-temperature migration of aqueous fluids because they are consumed in melting reactions. In this case, continued migration into supra-solidus terranes take place through the migration of water-rich melts. Thus, melts become the transport agent of water into supra-solidus terranes and responsible for water-fluxed melting. Other processes, such as the relatively rapid fluid migration through fractures, also allow regional aqueous fluids to by-pass the water-saturated solidus fluid trap and trigger melting above solidus conditions. When aqueous fluids or hydrous melts flux rocks at supra-solidus conditions, they equilibrate with the surroundings through further melting, decreasing water activity and giving rise to undersaturated melts. It is in these conditions that hornblende or anhydrous peritectic phases are stabilized. Unlike dehydration melting, the melt fraction generated in this case is not limited by the water contained in hydrous minerals but by the volume of water added to the system. Unlike melting at the water-saturated solidus, these melts are capable of rising without freezing and do give rise to upper crustal granitic bodies.

Simultaneous production of biosurfactant and ULSD (ultra low sulfur diesel) using Rhodococcus sp. in a chemostat

Production of ultra low sulfur diesel (ULSD) and biosurfactants, namely, 2-hydroxybiphenyl and different lipids has been studied. The substituted benzothiophenes (BTs) and dibenzothiophenes (DBTs) in hydro-treated diesel get converted to 2-hydroxy biphenyl, which is a potential bio-surfactant. Kinetics of biodesulfurization of deep desulfurized diesel using Rhodococcus sp. has been studied with special reference to removal of organo-sulfur compounds in diesel and production of 2-hydroxy biphenyl (2-HBP). The sulfur concentration of feed diesel is in the range of 200–540mg/L. Aqueous phase to diesel ratios have been varied in the range of 9:1 to 1:9. The optimum ratio has been found to be 1:4 based on both the ease of separation of aqueous phase from diesel and the value of specific microbial growth rate and the maximum conversion of sulfur of 95% has been achieved. The values of Monod kinetic parameters, μmax, maximum specific growth rate and Ks, saturation constant of the microbial growth and yield coefficient of surfactant have been measured to be 0.13h−1, 68mg/L, and 18.5μmol/g dry cell weights respectively by conducting batch type experiments at the optimum ratio of oil to aqueous phase. A chemostat has been studied using initial concentration of organo-sulfur compounds in diesel as a parameter. The identification of 2-HBP in treated diesel has been made using HPLC and GC–MS. A mathematical model has been developed on the basis of kinetic parameters derived from the shake flask analysis. The model has been validated by the comparison with the experimental data. Lipid content has been determined. Effects of extent of bio-desulfurization on the reduction of surface tension of aqueous nutrient phase, diesel phase and emulsification index have been determined.

Micelle-Mediated Extraction Prior to LC-UV for Preconcentration and Determination of Trace Amounts of Bisphenol A in Environmental Samples

A simple and high sensitive preconcentration method based on micelle-mediated extraction followed by high performance liquid chromatography (LC-UV) was developed for preconcentration and determination of trace amounts of bisphenol A (BPA) in aqueous samples. The BPA was quantitatively extracted from aqueous samples in the presence of Triton X-114 as a nonionic surfactant and preconcentrated into the small volume (about 30 μL) of the surfactant-rich phase. Taguchi method, an orthogonal array design (OA16 (45)), was utilized to optimize the various factors affecting the micellar extraction of BPA. The maximum extraction efficiency of BPA was obtained at pH 3, 0.2% (w/v) Triton X-114, and 0.25 mol L−1 sodium acetate. For the preconcentration, the solutions were incubated in a thermostatic water bath at 50°C for 7 min. After centrifuge and separation of aqueous phase, the surfactant-rich phase was diluted with 100 μL acetone and injected in the chromatographic system. Under the optimum conditions, preconcentration factor of 34.9 was achieved for extraction from 10 mL of sample solution and the relative standard deviation (RSD%) of the method was lower than 6.6%. The calibration curve was linear in the range of 0.5–150 μg L−1 with reasonable linearity (r2>0.9987). The limit of detection (LOD) based on S/N = 3 was 0.13 μg L−1 for 10 mL sample volumes. The limit of quantification (LOQ) based on S/N = 10 was 0.43 μg L−1 for 10 mL sample volumes. Finally, the applicability of the proposed method was evaluated by the extraction and determination of BPA in the real samples, and satisfactory results were obtained.

Improved Transferase/Hydrolase Ratio through Rational Design of a Family 1 β-Glucosidase from Thermotoga neapolitana

Alkyl glycosides are attractive surfactants because of their high surface activity and good biodegradability and can be produced from renewable resources. Through enzymatic catalysis, one can obtain well-defined alkyl glycosides, something that is very difficult to do using conventional chemistry. However, there is a need for better enzymes to get a commercially feasible process. A thermostable β-glucosidase from the well-studied glycoside hydrolase family 1 from Thermotoga neapolitana, TnBgl1A, was mutated in an attempt to improve its value for synthesis of alkyl glycosides. This was done by rational design using prior knowledge from structural homologues together with a recently generated model of the enzyme in question. Three out of four studied mutations increased the hydrolytic reaction rate in an aqueous environment, while none displayed this property in the presence of an alcohol acceptor. This shows that even if the enzyme resides in a separate aqueous phase, the presence of an organic solvent has a great influence. We could also show that a single amino acid replacement in a less studied part of the aglycone subsite, N220F, improves the specificity for transglycosylation 7-fold and thereby increases the potential yield of alkyl glycoside from 17% to 58%.

Direct catalytic upgrading of biomass pyrolysis vapors by a dual function Ru/TiO2 catalyst

The results of catalytic treatment of vapors exiting a g/min pyrolysis unit before product condensation to the liquid phase using a Ru/TiO2 catalyst for oak and switchgrass pyrolysis are reported. The pyrolysis is conducted at 500°C and the catalysis at 400°C at atmospheric pressure with a hydrogen partial pressure of 0.58 atm. It is found that the catalytic treatment provides significant conversion of light oxygenates to larger, less oxygenated, molecules and, simultaneously, bio‐oil phenolics are also converted to less oxygenated phenolics with methoxy methyl groups transferred to the ring. The activity of the catalyst gradually diminished with increasing biomass fed to the system. Untreated pyrolysis oil forms a single liquid phase with some tarry material, consistent with the literature, whereas the treated liquid product forms separate oil and aqueous phases, the latter of which is about 80% water. The oil from the treated vapors has a lower initial viscosity with only a small increase upon accelerated aging compared to the untreated product oil, which has a dramatic increase in viscosity after aging. This is indicative of poor oil stability for untreated oil that is further confirmed by large increases in molecular weight, while the treated oil has a small increase in molecular weight after accelerated aging. In an effort to understand compatibility with refinery streams, the solubility of the oils in tetralin was examined. The untreated oil was found to have very limited solubility in tetralin, whereas the treated oil phase was completely soluble except for a small aqueous phase that appeared. There are a number of challenges in developing a high yield process for pyrolysis based conversion of biomass to transportation fuels. The Ru/TiO2 catalyst used here shows promise for conducting multiple types of favorable reactions in the presence of the full spectrum of primary pyrolysis products that creates significant product stability under mild conditions. This could lead to higher liquid yields of stable, refinery compatible, product oil. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2275–2285, 2013

Selective Transport of Water-Soluble Proteins from Aqueous to Ionic Liquid Phase via a Temperature-Sensitive Phase Change of These Mixtures

Mixtures of some ionic liquids (ILs) and water show reversible phase change between a homogeneous mixture and phase-separated state by a small change in temperature. Some water-soluble proteins have been migrated from the aqueous to the IL phase. When tetrabutylphosphonium 2,4,6-trimethylbenzenesulfonate was used as an IL, cytochrome c (Cyt.c) was found to be extracted from the water phase to the IL phase. Conversely, both horseradish peroxidase (HRP) and azurin remained in the aqueous phase. This selective extraction was comprehended to be due to the difference in solubility of these proteins in both phases. The separated aqueous phase contained a small amount of IL, which induced the salting-out of Cyt.c. On the other hand, condensed IL phase promoted the salting-in of Cyt.c. As a result, Cyt.c was preferably dissolved in the hydrated IL phase rather than aqueous phase. In the case of HRP, there was only a salting-out profile upon increasing the concentration of IL, which induced selective dissolution of HRP in the aqueous phase. These results clearly suggest that the profile of salting-out and salting-in for proteins is the key factor to facilitate the selective extraction of proteins from aqueous to the IL phase.

Estimation of the electric field strength required for breaking the water-in-oil emulsion: A thermodynamic approach considering droplets deformation and the effect of interfacial tension

The deformability of droplets in an emulsion, when they approach each other, may affect the stability of emulsion and its phase behavior. In this study we have modified the repulsion potential function between the droplets in order to take this phenomenon into account. Appropriate changes to other parts of the potential function have been made to implement the influence of the geometric alternations due to droplets deformation. We have used the first order Barker–Henderson perturbation theory to derive a thermodynamic model for computing the equilibrium between the emulsified water droplets in oil and the separated aqueous phase. Based on the proposed model, phase diagrams for oil-water emulsions have been determined and the effects of various physical parameters on the equilibrium conditions have been investigated. We have also presented phase diagrams comparing the results considering the drops deformable and non-deformable when they approach each other. The model can favorably lead us to the prediction of the required electric field strength for breaking the stable emulsions. The important physical properties such as the polarity of the droplets, adsorption layer thickness, size of the droplets and interfacial tension are taken into account. The results obtained from the proposed model have been favorably compared with available experimental data. It has been shown that deformation has no effect on the emulsions with relatively large water drops; however, for small droplets the effect of deformation is noticeable and could not be ignored.

Complex Phase Behavior in the Transition Region Between Gel (L β ) and Lamellar (L α ) Phases for a Commercial Nonionic Surfactant System, C12-14EO3

Surfactant formulators are faced with many challenges during product processing and manufacture, with increased problems from the use of commercial surfactants. Commercial surfactants have a distribution of EO sizes which can dramatically affect the product properties. The gel (L β )/lamellar (L α ) phase transition of a commercial surfactant C12-14EO2.9/water system is shown to split into two, with the sequence ↔ L α being observed, where the region occurs over a ca. 10°C temperature range. In addition, both the gel and lamellar phases can incorporate at least 2–3 times more water than the pure surfactants before the formation of a separate aqueous phase. So while commerical surfactants could pose problems for formulators, they could also offer the possibility of enhanced solubilization of actives in the lamellar regions coupled with the enhanced emulsion stabilization by the gel phase.

Use of a Corona Discharge to Selectively Pattern a Hydrophilic/Hydrophobic Interface for Integrating Segmented Flow with Microchip Electrophoresis and Electrochemical Detection

Segmented flow in microfluidic devices involves the use of droplets that are generated either on- or off-chip. When used with off-chip sampling methods, segmented flow has been shown to prevent analyte dispersion and improve temporal resolution by periodically surrounding an aqueous flow stream with an immiscible carrier phase as it is transferred to the microchip. To analyze the droplets by methods such as electrochemistry or electrophoresis, a method to "desegment" the flow into separate aqueous and immiscible carrier phase streams is needed. In this paper, a simple and straightforward approach for this desegmentation process was developed by first creating an air/water junction in natively hydrophobic and perpendicular PDMS channels. The air-filled channel was treated with a corona discharge electrode to create a hydrophilic/hydrophobic interface. When a segmented flow stream encounters this interface, only the aqueous sample phase enters the hydrophilic channel, where it can be subsequently analyzed by electrochemistry or microchip-based electrophoresis with electrochemical detection. It is shown that the desegmentation process does not significantly degrade the temporal resolution of the system, with rise times as low as 12 s reported after droplets are recombined into a continuous flow stream. This approach demonstrates significant advantages over previous studies in that the treatment process takes only a few minutes, fabrication is relatively simple, and reversible sealing of the microchip is possible. This work should enable future studies in which off-chip processes such as microdialysis can be integrated with segmented flow and electrochemical-based detection.

Study by Differential Scanning Calorimetry of Water-in-Oil Emulsions Stabilized by Clays and CTAB

In this work, we have tested various formulations in order to get emulsions containing pure water, Tunisian olive oil, Tunisian clays, and an ammonium salt. Two different types of clays: smectite and kaolinite and the cethyltrimethylamonium bromide (CTAB) were tested. CTAB is used as surfactant and a compound modifying the clays properties. The amount of CTAB being fixed at 0.66 w/w, the proportions of clays were varied from 0 to 9% for each of the following proportions of water: 10, 20, 30%. To the aqueous phase obtained by mixing two separate aqueous phases: water + CTAB and water + clay, the oil was added drop by drop, the agitation being maintained at 5000 rpm. The obtained mixtures were analyzed by Differential Scanning Calorimetry (DSC), optical microscopy and bottle tests. An optimized formulation containing water (30%), smectite clay (5.3%) and CTAB (0.66%) was found to give W/O emulsions which kinetic stability is greater than 75 days regarding coalescence and greater than 700 hours regarding sedimentation.

The stability of high internal phase emulsions at low surfactant concentration studied by small angle neutron scattering

The changes in structure of high internal phase emulsions at low concentrations and at elevated temperature are reported for comparison with the same emulsions under conditions well away from instability. Small angle neutron scattering measurements on aqueous ammonium nitrate droplets dispersed in hexadecane and stabilized by very small quantities of a polyisobutylene-based surfactant (PIBSA) as well as related inverse micellar solutions in hexadecane, have been made as a function of temperature and surfactant concentration. Experimental conditions here favour larger and more deformable droplets than in previous studies. Besides the expected micelles and adsorbed surfactant, planar bilayers of micron lateral extent between touching droplets cover 20% of the droplet surface. Another difference from previous experiments is that the oil phase in the emulsions, and corresponding inverse micellar solutions are different in micellar radii and composition. The differences, and changes with surfactant concentration and temperature, are attributed to fractionation of the polydisperse PIBSA in the emulsions, but not the inverse micellar solutions. At low PIBSA concentration and high temperature the SANS shows emulsion decomposing into separate oil and aqueous phases. This occurs when the micelle concentration reaches a very small but measurable value. The inverse micelles may suppress by steric action long wavelength unstable capillary waves in the bilayers. Depletion repulsion forces here have a minor role in the emulsion stabilization.

Improved Extraction Method for the Determination of Iron, Copper, and Nickel in New Varieties of Sunflower Oil by Atomic Absorption Spectroscopy

A simple and fast procedure is proposed for the extraction of iron (Fe), copper (Cu), and nickel (Ni) in 16 varieties of sunflower seed oil samples using an ultrasonic bath. The experimental parameters of the ultrasonic-assisted extraction (UAE) method were optimized to improve the sensitivity and detect the metals at trace levels in minimum time. Conventional wet acid digestion method was used for comparative purposes. The optimum recovery of all 3 metals was obtained by UAE for 7 min, while the separation of aqueous and organic phases after extraction using centrifugation (UAE-2) required 3 min, as compared to the conventional equilibration method (UAE-1) that required 90 min. The respective recoveries of Cu, Fe, and Ni obtained with UAE-2 were in the range of 95.8-97.5, 93.5-98.3, and 95.6-98.2%, respectively, for different varieties of sunflower oil samples. Accuracy was determined by the standard addition method. Under the optimum operating conditions, the limits of detection obtained from the standard addition curves were 21.7, 20.4, and 35.6 ng/mL for Fe, Cu, and Ni, respectively. The fact that all varieties of sunflower oil contain significant amounts of Fe, Cu, and Ni indicates the deterioration of sunflower oil quality immediately after extraction from seeds, which poses a threat to oil quality and human health.

Evidence for 26 distinct acyl-coenzyme A synthetase genes in the human genome

Acyl-coenzyme A synthetases (ACSs) catalyze the fundamental, initial reaction in fatty acid metabolism. "Activation" of fatty acids by thioesterification to CoA allows their participation in both anabolic and catabolic pathways. The availability of the sequenced human genome has facilitated the investigation of the number of ACS genes present. Using two conserved amino acid sequence motifs to probe human DNA databases, 26 ACS family genes/proteins were identified. ACS activity in either humans or rodents was demonstrated previously for 20 proteins, but 6 remain candidate ACSs. For two candidates, cDNA was cloned, protein was expressed in COS-1 cells, and ACS activity was detected. Amino acid sequence similarities were used to assign enzymes into subfamilies, and subfamily assignments were consistent with acyl chain length preference. Four of the 26 proteins did not fit into a subfamily, and bootstrap analysis of phylograms was consistent with evolutionary divergence. Three additional conserved amino acid sequence motifs were identified that likely have functional or structural roles. The existence of many ACSs suggests that each plays a unique role, directing the acyl-CoA product to a specific metabolic fate. Knowing the full complement of ACS genes in the human genome will facilitate future studies to characterize their specific biological functions.

A Proteomics Study of Brassinosteroid Response in Arabidopsis

The plant steroid hormones brassinosteroids (BRs) play an important role in a wide range of developmental and physiological processes. How BR signaling regulates diverse processes remains unclear. To understand the molecular details of BR responses, we performed a proteomics study of BR-regulated proteins in Arabidopsis using two-dimensional DIGE coupled with LC-MS/MS. We identified 42 BR-regulated proteins, which are predicted to play potential roles in BR regulation of specific cellular processes, such as signaling, cytoskeleton rearrangement, vesicle trafficking, and biosynthesis of hormones and vitamins. Analyses of the BR-insensitive mutant bri1-116 and BR-hypersensitive mutant bzr1-1D identified five proteins (PATL1, PATL2, THI1, AtMDAR3, and NADP-ME2) affected both by BR treatment and in the mutants, suggesting their importance in BR action. Selected proteins were further studied using insertion knock-out mutants or immunoblotting. Interestingly about 80% of the BR-responsive proteins were not identified in previous microarray studies, and direct comparison between protein and RNA changes in BR mutants revealed a very weak correlation. RT-PCR analysis of selected genes revealed gene-specific kinetic relationships between RNA and protein responses. Furthermore BR-regulated posttranslational modification of BiP2 protein was detected as spot shifts in two-dimensional DIGE. This study provides novel insights into the molecular networks that link BR signaling to specific cellular and physiological responses.