Showing papers on "Extraction (chemistry) published in 1992"
TL;DR: In this paper, the effect of nitric acid concentration on the selectivity of a novel extraction chromatographic resin consisting of an octanol solution of 4,4′(5′)-bis(t-butyl-cyclohexano)-18-crown-6 sorbed on an inert polymeric support for strontium over a number of alkali, alkaline earth, and other metal cations was evaluated.
Abstract: The effect of nitric acid concentration on the selectivity of a novel extraction chromatographic resin consisting of an octanol solution of 4,4′(5′)-bis(t-butyl-cyclohexano)-18-crown-6 sorbed on an inert polymeric support for strontium over a number of alkali, alkaline earth, and other metal cations was evaluated. The effect of macro quantities of selected elements on strontium retention by the resin was also examined. The resin is shown to exhibit excellent selectivity for strontium over nearly all of the test elements; only lead and tetravalent neptunium, polonium, and plutonium show significant affinity for the material. In addition, concentrations of calcium or sodium ion up to ∼ 0.1 M. are shown not to diminish the sorption of strontium appreciably. Several useful radiochemical separation schemes devised on the basis of the results obtained are described.
686 citations
TL;DR: In this paper, the absorption and desorption processes of benzene, toluene, and p-xylene were described and compared with experimental results for solid-phase microextraction using poly(dimethylsiloxane)-coated fused silica optical fibers.
Abstract: Mathematical descriptions of the absorption and desorption processes were developed and compared with experimental results for solid-phase microextraction (SPME) using poly(dimethylsiloxane)-coated fused silica optical fibers. Extraction times for benzene, toluene, and p-xylene using a coating thickness of 55 {mu}m are under 10 min and can be shortened substantially using agitation. Detection limits and distribution coefficients for several organic compounds are presented. 20 refs., 13 figs., 1 tab.
605 citations
TL;DR: In this paper, the effect of macro levels of selected elements on the sorption of actinide ions by a novel extraction chromatographic resin comprised of a solution of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide in tri-n-butyl phosphate supported on an inert polymeric substrate is described.
578 citations
TL;DR: In this paper, the authors found that milkweed fiber and cotton fiber sorbed significantly higher amounts of crude oil than polypropylene fiber and polyethylene web from the surface of an artificial sea water bath containing crude oil and from a crude oil bath.
Abstract: Milkweed (Asclepias) fiber and cotton fiber sorbed significantly higher amounts of crude oil than polypropylene fiber and polypropylene web from the surface of an artificial sea water bath containing crude oil and from a crude oil bath. Milkweed sorbed approximately 40 g of crude oil/g of fiber at room temperature. The oil sorption capacity of kenaf core material was comparable with that of polypropylene web with high-viscosity Bunker C oil. Only a slight variation was observed in the oil sorption of the natural fiber sorbent by Soxhlet extraction and water-soaking treatments before the sorption process
539 citations
247 citations
226 citations
TL;DR: It was found that the degrading strain was able to grow to the same high numbers in soil amended with 2,4-D, while the strain in nonamended soil were maintained at the inoculation level.
Abstract: A new method for the extraction of bacterial DNA from soil has been developed. Soil samples of 50 g were dispersed, and bacteria were released by use of a cation-exchange resin; subsequently, bacteria were separated from soil particles by low-speed centrifugation and lysed with lysozyme and ionic detergent, and the DNA was then purified by CsCl-ethidium bromide equilibrium density centrifugation. The extracted DNA was of high molecular weight and sufficiently pure for restriction enzyme digestion, DNA-DNA hybridization, and amplification by the polymerase chain reaction. The advantages of the new method are that the separation of bacteria from soil is considerably faster than by repeated blending, more samples can be handled, and furthermore no aerosols are formed during separation. Also, we investigated whether the CsCl-ethidium bromide equilibrium density centrifugation could be replaced by purification using Gene-Clean. However, this method produced DNAs which were insufficiently pure for several types of analysis. The new method was used to study survival of a 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading Pseudomonas cepacia DBO1 (pRO101) in unamended soil and in soil amended with 2,4-D. We found that the degrading strain, irrespective of inoculation level, was able to grow to the same high numbers in soil amended with 2,4-D, while the strain in nonamended soil were maintained at the inoculation level. Detection based on DNA extraction and subsequent dot blot DNA-DNA hybridization was in accordance with detection by plating on selective medium. Images
209 citations
TL;DR: In this article, the suitability of a recently published extraction chromatographic method to isolate from geological samples for isotopic analyses by thermal ionization mass spectrometry was evaluated, which has several significant advantages over conventional ion exchange techniques.
205 citations
TL;DR: In this paper, a continuous substrate feeding has been applied to the batch fermentation process using freely suspended cells, for ABE (acetone-butanol-ethanol) production, where liquid-liquid extraction, perstraction, gas-stripping, and pervaporation were investigated.
Abstract: The technique of continuous substrate feeding has been applied to the batch fermentation process using freely suspended cells, for ABE (acetone-butanol-ethanol) production. To avoid the product inhibition which normally restricts ABE production to less than 20 g/L and sugar utilization to 60 g/L, a product removal technique has been integrated into the fermentation process. The techniques investigated were liquid-liquid extraction, perstraction, gas-stripping, and pervaporation. By using a substrate of whey permeate, the reactor productivity has been improved over that observed in a traditional batch fermentation, while equivalent lactose utilization and ABE production values of 180 g and 69 g, respectively, have been achieved in a 1-L culture volume. 17 refs., 14 figs., 5 tabs.
182 citations
TL;DR: In this article, a comparison of the solvent extraction behavior of metallurgically important first-row transition metal ions from acidic sulfate solution by these reagents is reported, and the nature of the metal complexes formed have been determined using slope analysis techniques and spectroscopic measurements.
181 citations
TL;DR: The sensitivity of the method was determined by the thickness of the film of stationary phase; the equilibration time, however, increased with the film thickness, although it can be minimized by use of a cross-shaped stirrer bar as discussed by the authors.
Abstract: Solid Phase Micro Extraction (SPME) involves exposing a fused silica fiber coated with stationary phase to a contaminated water sample. The organic analytes become partitioned between the stationary phase and the water and when equilibrium is reached the fiber is removed from the solution and the analytes are thermally desorbed in the injector of a gas chromatograph. The fiber is contained in a syringe to facilitate handling.
Factors which affect linear range, limit of detection, and total analysis time are discussed with regard to the development of a method for analysis of volatile compounds in environmental water samples. The sensitivity of the method was determined by the thickness of the film of stationary phase; the equilibration time, however, increased with the film thickness, although it can be minimized by use of a cross-shaped stirrer bar.
Increasing the thickness of stationary phase in the analytical column enables the cryofocusing temperature to be increased from −40 to −15°C. With an ion trap mass spectrometer, detection limits required by the US Environmental Protection Agency are met for all compounds except chloromethane and chloroethane. The method has been applied to environmental water samples.
TL;DR: In this article, a modified method based upon liquid-solid extraction of pesticides from drinking water followed by high-performance liquid chromatography (HPLC) was modified to make it suitable for monitoring 89 pesticides in ground-water and river water.
Abstract: Our recent method based upon liquid-solid extraction of pesticides from drinking water followed by high-performance liquid chromatography (HPLC) was modified tomake it suitable for monitoring 89 pesticides in ground-water and river water. The modified method involved passing 2, 1.5, and 0.5 L, respectively, of drinking water, groundwater, and river water through a 300-mg Carbopack cartridge at 120-130 mL/min. The complete separation of base-neutral pesticides from acidic ones was accomplished by a stepwise elution. After concentration of the two extracts, pesticides were separated and quantified by reversed-phase HPLC with UV detection
TL;DR: In this paper, the authors investigated the extraction mechanisms of U(VI), Th(IV), and Pu(IV) from nitric acid media for the amide DOBA(((C4H9) (C2H5) CHCH2)2 NC(O) C3H7) and DOiBA (((C 4H9), (C 2H5), CHCH 2 )2 NC (O) CH(CH3)2)) for low aqueous acidities.
Abstract: N,N-dialkylamides are potential alternative extractants to tributyl-phosphate for the actinide separation in nuclear fuel reprocessing. Extraction mechanisms of U(VI), Th(IV) and Pu(IV) from nitric acid media are investigated for the amide DOBA(((C4H9) (C2H5) CHCH2)2 NC(O) C3H7) and DOiBA (((C4H9) (C2H5) CHCH2)2 NC(O) CH(CH3)2). For low aqueous acidities, amides are neutral extractants. Extraction stoichiometrics of (Amide = DOBA or DOiBA), have been established. Th(IV) is supposed to form a di- and a trisolvate in the inner-coordination sphere. For concentrated solvents, bilogarithmic dependences of distribution coefficients with ligand concentration point out non-integer slopes higher than those expected from stoichiometry. Such features, very often noted for amides, do not seem to be due to new chemical second-sphere species, which has never observed experimentally, but to polyoriented interactions between free ligands and complexes and may be considered as part of non-ideality. Amides behave ...
TL;DR: In this paper, the extraction of caffeine from whole coffee beans with supercritical carbon dioxide was studied in a continuous-flow extraction apparatus and the decaffeination rates were determined as a function of CO2 flow rate, temperature and pressure by continuously monitoring the caffeine in the effluent with a flame ionization detector.
Abstract: The extraction of caffeine from whole coffee beans with supercritical carbon dioxide was studied in a continuous-flow extraction apparatus. Decaffeination rates were determined as a function of CO2 flow rate, temperature and pressure by continuously monitoring the caffeine in the effluent with a flame ionization detector. Soaking the raw beans in water prior to decaffeination enhanced the rate of extraction, which increased markedly with water content. Using CO2 saturated with water also increased the rate of extraction. The rate of decaffeination increased with pressure and temperature and was influenced by both intraparticle diffusion in the water-soaked beans and external mass transfer. A mathematical model based on a linear-driving-force approximation of mass transfer and partitioning of caffeine between the water and the supercritical CO2 describes the time-dependent process. The partition coefficient for caffeine distributed between water and supercritical CO2, the only parameter determined from the dynamic extraction rate data, increases with temperature and pressure.
TL;DR: Liquid—liquid extraction by reverse micelles of ionic surfactants in organic solvents is well suitable for separation and purification of extracellular enzymes from complex fermentation media, as demonstrated with α-amylase from Bacillus licheniformis.
TL;DR: In this article, supercritical fluid extraction (SFE) recoveries for native pollutants including PCBs from a standard reference material sediment (SRM 1939), PAH from a petroleum waste sludge, and PAHs from railroad bed soil were compared using supercritical CHCIF 2 (Freon-22), N 2 O, and CO 2.
Abstract: Supercritical fluid extraction (SFE) recoveries for native pollutants including PCBs from a standard reference material sediment (SRM 1939), PAHs from a petroleum waste sludge, and PAHs from railroad bed soil were compared using supercritical CHCIF 2 (Freon-22), N 2 O, and CO 2 . While SFE with pure CO 2 yielded the lowest recoveries for each sample, CHCIF 2 consistently yielded the highest extraction efficiencies, most likely because of its high dipole moment
01 Jan 1992
TL;DR: A mixer-settler arrangement provides a single equilibrium stage; a number of them connected together provide multistage extraction as mentioned in this paper, which creates a large interfacial area and increases the extraction rate considerably.
Abstract: Solvent extraction is a common industrially used equilibrium-based separation process. In such a process, a solute (or solutes) in a solution, aqueous or organic, is extracted into an immiscible solvent, organic or aqueous, by dispersing one of the immiscible phases as drops in the other phase. This creates a large interfacial area and increases the extraction rate considerably. After the extraction is over, the phases are separated and the dispersed phase coalesced. There are two general categories of equipment for solvent extraction. A mixer-settler arrangement provides a single equilibrium stage; a number of them connected together provide multistage extraction. Continuous countercurrent contacting equipment whether in the form of columns or centrifugal devices can generate the equivalent of many stages in one device (Treybal 1963).
TL;DR: Homologue and isomer distributions of SAS in sewage sludge indicated an enrichment of the more hydrophobic components in sewageSludge during sewage treatment.
Abstract: Secondary alkanesulfonate (SAS) and linear alkylbenzene-sulfonate (LAS) surfactants were quantitatively (> 90%) extracted from sewage sludges as their tetrabutylammonium ion pairs using 400 atm of supercritical CO2 for 5 min of static extraction followed by 10 min of dynamic extraction at 80 degrees C. Ion pairs of SAS and LAS quantitatively formed butyl esters in the injection port of the gas chromatograph and were determined by gas chromatography/mass spectrometry without class fractionation of the sewage sludge extracts. Concentrations of SAS and LAS in sludges from five different sewage treatment plants ranged from 0.27 to 0.80 g/kg of dry sewage sluge and from 3.83 to 7.51 g/kg, respectively. Good reproducibility was achieved with RSDs of typically 5% for replicate extractions and analyses. Homologue and isomer distributions of SAS in sewage sludge indicated an enrichment of the more hydrophobic components in sewage sludge during sewage treatment.
TL;DR: In this article, a mechanism is proposed to explain coextraction of essential oil and leaf and cuticular waxes, based on different mass transfer mechanisms for the two compound families.
Abstract: Carbon-dioxide SCF extraction from herbaceous substrates produces nearly solid extracts because of simultaneous solubilization of essential oil components and cuticular waxes. Fractionation of the extract is required to isolate the essential oil. A mechanism is proposed to explain coextraction of essential oil and leaf and cuticular waxes, based on different mass transfer mechanisms for the two compound families. Cuticular waxes are hypothesized as mainly solubilized by leaching, while essential oil extraction is supposed dependent on complex diffusion phenomena. If extraction mechanisms operate as modeled, fractional separation of supercritical solution can be realized in a series of separators, taking advantage of the different solubilities of the two compound families and of their different concentrations in the solution. Marjoram leaf (Origanum Majorana L.) essential oil isolation by SCF has been studied as an application of fractional separation procedure. A nearly complete fractionation has been realized and a high quality essential is oil produced.
TL;DR: In this paper, the acid hydrolyzed extracts which represented the total starch lipid [TSL] content ranged from 0.1% (potato) to 0.8% (corn) and the combined action of chloroform-methanol 2:1 v/v [CM] at ambient temperature, followed by n-propanol-water 3:1 V/V [PW] at 90-100°C.
TL;DR: In this paper, algae cells were successfully immobilized on a silica substrate and used in a chromatographic separation procedure that removed Pb from synthetic solutions, which revealed acceptable flow rates and efficient metal stripping by both HNO 3 and HCl.
Abstract: Algae cells were successfully immobilized on a silica substrate and used in a chromatographic separation procedure that removed Pb from synthetic solutions. Characterization of the resin in a chromatographic extraction mode revealed acceptable flow rates and efficient metal stripping by both HNO 3 and HCl. Variability associated with the growth, harvesting, immobilization, and column packing procedures were evaluated. Results revealed excellent reproducibility for the immobilization procedure, and the greatest source of variation was associated with the algae growing process
TL;DR: The nature of the species of the above metal ions extracted into the organic phase has been suggested and the effects of nitric acid, TBP and CMPO concentrations have been studied.
TL;DR: In this paper, the ability of various electrolytes to modify EDTA extraction of Pb from a grossly-contaminated soil (PbT=21%) was investigated using batch equilibration experiments.
Abstract: Because the economics of soil extraction processes depend on conservation and reuse of costly chelating agents, the ability of various electrolytes to modify EDTA extraction of Pb from a grossly-contaminated soil (PbT=21%) was investigated using batch equilibration experiments. In the absence of added electrolyte, a single 5-hr. extraction with 0.04 M EDTA (corresponding to 1∶1 PbT to EDTA ratio) released 65% of PbT over the pH 5 to 9 range. Under these conditions, Na+-, Li+-, and NH4ClO4 salts at 0.5 M increased Pb desorption to nearly 80%, probably from exchange displacement of soilbound Pb2+ and increased solubility of Pb-containing phases at higher ionic strength. Because Cl− and ClO4
− salts were equally effective, chlorocomplex formation was insignificant. Under slightly acidic conditions, Ca(ClO4)2 and Mg(ClO4)2 at 0.167 M caused roughly the same elevation in Pb recovery as 0.5M of the monovalent electrolytes. However, with progressively higher pH, Ca, and to a lesser extent Mg, suppressed Pb solubilization by competitive chelation of EDTA. Pb recovery by EDTA soil washing could be enhanced by addition of Ca salts at pH 4 to 6. Subsequent pH elevation in the presence of Ca would promote decomposition of Pb-EDTA complexes and separation of Pb as a hydroxide precipitate.
TL;DR: In this article, the solubilities of six fatty acids were modeled by Chrastil's equation, and estimated model parameters were used to plot the isotherms of fatty acids at 313, 323 and 333°K (40, 50 and 60°C) as a function of SC-CO2 density.
Abstract: The solubilities of lauric, linoleic, myristic, oleic, palmitic and stearic acid in supercritical carbon dioxide (SC-CO2) at different pressures and temperatures were measured. The solubility values obtained in this work were compared with previously published data, and possible causes for observed discrepancies were discussed. The solubilities of the six fatty acids were modeled by Chrastil’s equation, and estimated model parameters were used to plot the solubility isotherms of fatty acids at 313, 323 and 333°K (40, 50 and 60°C) as a function of SC-CO2 density. The comparison of solubility isotherms of fatty acids and vegetable oil suggests that separation of fatty acids from triglycerides might be possible by using SC-CO2 at densities less than 700 kg/m3. From the effect of temperature on fatty-acid and vegetable-oil solubility, it seems that the extraction yield could be increased without sacrificing the selectivity of SC-CO2 for fatty acids by choosing a higher operating temperature. The data also suggest that fractionation of certain fatty acids might be possible by manipulating the processing conditions. Given the values of the constants, Chrastil’s equation could serve as a guideline for choosing appropriate processing conditions and predicting the effect of pressure and temperature of SC-CO2 on solute solubility.
TL;DR: A solid-phase extraction procedure was developed for the isolation of acidic, neutral, and basic drugs from whole blood and the drugs with pKa's close to the pH of the extraction system appeared in both fractions.
Abstract: A solid-phase extraction procedure was developed for the isolation of acidic, neutral, and basic drugs from whole blood. A blood sample was sonicated, diluted with phosphate buffer, and the drugs were extracted on a mixed-mode bonded-phase silica column at pH 6.0. The extraction system was adjusted to pH 3.3 with acetic acid. After column drying, the drugs were selectively eluted from the column by two different eluates, which were collected separately. Acidic, neutral, and weakly basic drugs with lower pKa values (e.g., benzodiazepines) were present in the first acetone-chloroform (1:1) fraction. The other basic drugs were present in the second fraction (basic ethyl acetate). The drugs with pKa's close to the pH of the extraction system (pH 3.3) appeared in both fractions. The two fractions were evaporated until approximately 100 microL of solvent remained in the tube and were then analyzed on a gas chromatograph equipped with a wide-bore capillary column and flame ionization detector. The absolute recoveries of all tested drugs exceeded 81% at a concentration of 2 micrograms/mL.
TL;DR: In this paper, small columns of the chemically modified resins were found to be very efficient for the solid phase extraction of many types of organic solutes from aqueous samples.
TL;DR: Three simple, rapid procedures are presented: HPLC with final UV (275 nm) detection, a microanalysis utilizing a three-electrode electrochemical detector and a micro analysis with column-switching HPLC and electrochemical detection, concluded to be suitable for total plasma Co Q10 determination.
TL;DR: The behavior of crown ether-synergized sulfonic acid extraction systems suggested that the title system would be selective for cesium, and the new lipophilic crown ether, bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7), allowed testing of this hypothesis as discussed by the authors.
Abstract: The behavior of other crown ether-synergized sulfonic acid extraction systems suggested that the title system would be selective for cesium. Synthesis of the new lipophilic crown ether, bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7), allowed testing of this hypothesis. Under nonloading conditions, the distribution coefficient for cesium between a toluene solution 0.025 M in didodecylnaphthalenesulfonic acid (HDDNS) and D(tBB)21C7 and an aqueous phase 0.1 M in nitric acid is 100 with separation factors of 1.2 from rubidium, 5.6 from potassium, and 294 from sodium. Under loading and competitive extraction conditions, the distribution coefficients were lower (5 for cesium), but the separation factors remained in the same order and of useful magnitude, 1.5 from rubidium, 6.4 from potassium, and 192 from sodium. Increasing the concentrations of D(tBB)21C7 and HDDNS in the organic phase gives higher distribution coefficients for cesium as did lower aqueous acid concentrations. 23 refs., 8 figs., 1 tab.
TL;DR: In this article, a simple method for the separation and preconcentration of radiostrontium from acidic nuclear waste solutions for subsequent determination is described, which involves passage of the waste solution, acidified to at least 2M with nitric acid, through an extraction chromatographic column consisting of a 1M solution of bis-4,4′(5′)[(t-butyl)cyclohexano]-18-crown-6 in 1-octanol sorbed on an inert polymeric substrate, which preferentially retains strontium.
Abstract: A simple method for the separation and preconcentration of radiostrontium from acidic nuclear waste solutions for subsequent determination is described. The method involves passage of the waste solution, acidified to at least 2M with nitric acid, through an extraction chromatographic column consisting of a 1M solution of bis-4,4′(5′)[(t-butyl)cyclohexano]-18-crown-6 in 1-octanol sorbed on an inert polymeric substrate, which preferentially retains strontium. The strontium may then be stripped from the column with a small volume of either dilute (≤0.05M) nitric acid or water. Actinides present are removed quantitatively prior to strontium separation by passage of the sample through an actinide-specific extraction chromatographic column.