Showing papers on "Extraction (chemistry) published in 1998"

Solid-Phase Extraction: Principles and Practice

Abstract: Overview of Solid-Phase Extraction. Theory of Sorption and Isolation. Methods Development. Reversed-Phase Solid-Phase Extraction. Normal-Phase Solid-Phase Extraction. Ion-Exchange Solid-Phase Extraction. Environmental Analysis. Drugs and Pharmaceuticals. Food and Natural Products. Automation of Solid-Phase Extraction. Solid Phase Extraction Disks. New Technology in Solid-Phase Extraction. Appendix. Index.

Microwave irradiation of soil for routine measurement of microbial biomass carbon

Abstract: Microwave irradiation was evaluated as a non-toxic alternate to chloroform fumigation for routine measurement of soil microbial biomass C. Microwave energy was applied to moist soil to disrupt microbial cells. The flush of C released was then measured after extraction or incubation. Microwave irradiation at 800 J g–1 soil was optimal because this level resulted in an almost instantaneous rise in soil temperature (≥80 °C), an abrupt reduction in microbial activity, maximal release of biomass C, and minimal solubilization of humic substances. Both incubation-CO2 titration and extraction-colorimetry methods were used on separate 20-g subsamples to compare the labile C in the microwave-treated and untreated soil samples. The incubation-titration method was also used to measure C in chloroform-fumigated soil samples. Averaged across soils, the chloroform fumigation yielded 123.3±5.1 mg CO2-C kg–1. Microwave irradiation yielded 93.6±3.9 mg CO2-C kg–1 soil determined by incubation and 52.4±2.4 mg C kg–1 soil determined by extraction, accounting for 76% and 42% of the net flush of C measured by the chloroform fumigation. Microwave-stimulated net flushes of C were correlated closely (r 2=0.974 for incubation or 0.908 for extraction) with microbial biomass C measured by the chloroform fumigation. Little correlation was found with the total soil organic C (r 2=0.241 for incubation or for 0.166 extraction). Mean efficiency factors for incubation (K MI) or extraction (K ME) were used to calculate microbial biomass C from net flushes of C between microwaved and unmicrowaved soils. Values of K MI and K ME were not affected by soil pH, bulk density or clay contents. Extraction of microwaved soil by 0.5M K2SO4 proved to be a simple, fast, precise, reliable, and safe method to measure soil microbial biomass C.

Methods for microbial DNA extraction from soil for PCR amplification.

Abstract: Amplification of DNA from soil is often inhibited by co-purified contaminants. A rapid, inexpensive, large-scale DNA extraction method involving minimal purification has been developed that is applicable to various soil types (1). DNA is also suitable for PCR amplification using various DNA targets. DNA was extracted from 100g of soil using direct lysis with glass beads and SDS followed by potassium acetate precipitation, polyethylene glycol precipitation, phenol extraction and isopropanol precipitation. This method was compared to other DNA extraction methods with regard to DNA purity and size.

Extraction methods for environmental analysis

Abstract: Environmental Analysis. AQUEOUS SAMPLES. Aqueous Sample Preparation. Classical Approaches for the Extraction of Analytes from Aqueous Samples. Solid Phase Extraction. Solid Phase Microextraction. SOLID SAMPLES. Solid Sample Preparation. Liquid--Solid Extraction. Supercritical Fluid Extraction. Microwave--Assisted Extraction. Accelerated Solvent Extraction. Comparison of Extraction Methods. Indexes.

Application of dynamic liquid-phase microextraction to the analysis of chlorobenzenes in water by using a conventional microsyringe.

Abstract: A dynamic liquid-phase microextraction technique combined with gas chromatography/mass spectrometry (GC/MS) is described for the extraction of 10 chlorobenzenes from water samples into 1 μL of organic solvent by using a conventional microsyringe. The effects of extraction solvent, plunger movement pattern, sampling volume, number of samplings, and salt concentration on the extraction performance were investigated. Good repeatabilities of extraction were obtained, with the RSD values below 5.3% except for hexachlorobenzene (9.3%). By using a sampling volume of 6 μL and 15 samplings, detection limits were found to be between 0.02 and 0.05 μg/L under GC/MS-selective ion monitoring mode.

Extraction of Rosemary by Superheated Water

Abstract: Superheated water under pressure between 125 and 175 °C has been shown to rapidly extract the oxygenated fragrance and flavor compounds from Rosmarinus officinalis, while the monoterpenes are extracted slowly, and only very small amounts of the sesquiterpenes, waxes, and lipids are removed. The eventual yields of oxygenated compounds are higher than are obtained by steam distillation. Although larger amounts of water are needed for extraction by superheated water, the energy costs are competitive because it is not necessary to vaporize the water and most of the heat required can be recycled. The experiments conducted on a laboratory scale indicate that extraction by superheated water could be a viable process for the production of high quality plant extracts. Keywords: Rosmarinus officinalis; superheated water; subcritical water; extraction; fragrance; flavor

Bioaccessibility of Metals in Soils for Different Liquid to Solid Ratios in Synthetic Gastric Fluid

Abstract: The bioaccessible fraction of metals in the stomach has been estimated for two soil materials using laboratory synthesized gastric juice. Heavy metals present in each soil matrix were extracted and measured, as a technique to simulate metal solubilization processes that occur in the human stomach. The results from the synthetic gastric juice extraction were compared to values obtained using a modified EPA concentrated acid extraction procedure, method 3051, on the same soils. The experiments evaluated the effect of varying the liquid to solid ratio on gastric juice extraction efficiency for arsenic (As), chromium (Cr), nickel (Ni), cadmium (Cd), and lead (Pb). Soil samples employed were a National Institute of Standards and Technology (NIST) standard soil (Montana SRM 2710) and a composite hazardous waste contaminated soil from Jersey City, NJ. The current work demonstrates that bioaccessibility is not the same for each metal within a given soil, nor between the soils. Estimates of the bioaccessible fract...

Two phase extraction of oil from biomass

Abstract: A method of separating edible oil from biological material is disclosed. A biomass slurry containing microbial material in an aqueous suspension is collected. The slurry is typically placed in a centrifuge and then in a homogenizer. The resulting slurry is fed into a contacting device, such as a packed column, and mixed with a solvent that is essentially immiscible in water, for example hexane. The solvent extracts the oil from the biomass slurry and then separates from the slurry. Edible oil is recovered from the solvent and further processed.

Pressure-enhanced extraction and purification

Abstract: Methods for cell lysis and purification of biological materials, involving subjecting a sample to high pressure. Also featured is an apparatus for practicing the methods.

Solvent Microextraction with Simultaneous Back-Extraction for Sample Cleanup and Preconcentration: Quantitative Extraction

Abstract: A solvent microextraction technique has been developed to perform simultaneous forward- and back-extraction across a microliter-size organic liquid membrane. The organic liquid membrane phase (o), consisting of 40 or 80 μL of n-octane, is layered over 0.5 or 1.0 mL of aqueous sample phase (a1) contained in a 1- or 2-mL microreaction vial and is stabilized against mechanical disruption by a small Teflon ring, even when the a1 phase is stirred at a speed of 2000 rpm. A 0.1- or 0.2-mL aqueous receiving phase (a2) is layered over the o phase. After extraction for a prescribed time, an aliquot of the a2 phase is injected directly into an HPLC for quantification. The technique is efficient and selective for ionizable compounds. In 30 min, the model compounds, mephentermine and 2-phenylethylamine, in the a1 phase buffered at pH 13 are 100% and 90% extracted, respectively, into the a2 phase buffered at pH 2.1. A kinetic model has been developed, based on the Whitman two-film theory, to describe the extraction pro...

Survey and Trends in the Preparation of Chemically Bonded Silica Phases for Liquid Chromatographic Analysis

Abstract: In order to increase chromatographic selectivity and to extend the analytical capability of reversed phase liquid chromatography (RP HPLC) many investigators have concentrated on the preparation of silica based column packings with chemically bonded phases (CBP). These phases have also been successfully used in sample preparation techniques, mainly in solid phase extraction (SPE). Although alkyl bonded phases (e.g., C2, C8, and C18) are the most widely used packings in RP HPLC and SPE, various specific applications require CBPs with polar functional groups (e.g., -NH2, -NO2, -CN, and/or -OH). The solution of problems with separation of complicated chiral compounds was attempted by applying stationary phases with chiral selectors (e.g., cyclodextrins, Pirkle phases, crown ethers, etc.). On the other hand, packings with pseudo-membrane or liquid crystal properties have been utilized for the separation of various substances of natural origin. Porous silica is commonly used as a support in the preparation of CBPs. Its physico-chemical characteristics, such as: type and structure of siliceous matrix, porosity, type and concentration of silanol groups, as well as surface purity, strongly influence the density and structure of chemically bonded phases. Recognition of these properties is helpful in optimizing separation processes based on RP HPLC elution and/or extraction of substances with polar character.

Characterization and Quantification of Betacyanin Pigments from Diverse Amaranthus Species

Abstract: The betacyanin pigments from 21 genotypes of 7 Amaranthus species were separated by gel filtration chromatography and HPLC. On the basis of their IR and UV−visible spectra, enzymatic hydrolysis, and chromatographic profiles, the pigments were identified as homogeneous betacyanins, which consisted on average of 80.9% amaranthine and 19.2% isoamaranthine. Dried crude betacyanin extracts contained 23.2−31.7% protein, and the purified sample retained 12.8% protein. The betacyanins were difficult to separate from protein. Total betacyanins in the Amaranthus species ranged from 46.1 to 199 mg/100 g of fresh plant material and from 15.4 to 46.9 mg/g of dry extracts. The mean extraction rate of the eight best genotypes was 2.18%. Amaranthus cultivated species contained much more betacyanin than wild species and had much higher biomass, indicating that certain cultivated genotypes had greater potential for commercial development as natural colorant sources. Dried extracts from Amaranthus species may form natural n...

Nonmonotonic Effect of Ionic Strength on Surface Dye Extraction during Dye−Polyelectrolyte Multilayer Formation

Abstract: Multilayer formation between organic dyes and polyions is complicated by the possible competition between dye extraction from the surface by the polymer solution instead of polymer adsorption. We study the effects of salt concentration (NaCl, Na2SO4, MgCl2, and MgSO4) on this process and note that significant fractions of the dye are removed from the surface at intermediate salt concentration but that at lower or higher salt concentration less surface dye extraction occurs. Polymer solutions with intermediate NaCl concentrations show more than 60% dye extraction, while those of MgCl2, Na2SO4, and MgSO4 show approximately 30%, 25%, and 20% dye extraction, respectively. The maximum in dye extraction for all of these salts occurs when the solution Debye length is approximately 2 A. The reduced efficiency of dye complexation away from the maximum is interpreted in terms of the polymer's expected increase in persistence length (low salt concentration) and the reduced electrostatic interactions between the char...

EFFECT OF NITRIC ACID EXTRACTION ON PHASE BEHAVIOR, MICROSTRUCTURE AND INTERACTIONS BETWEEN PRIMARY AGGREGATES IN THE SYSTEM DIMETHYLDIBUTYLTETRADECYLMALONAMIDE (DMDBTDMA) / n-DODECANE / WATER: A PHASE ANALYSIS AND SMALL ANGLE X-RAY SCATTERING (SAXS) CHARACTERISATION STUDY

Abstract: Among the different problems to be solved when designing a liquid-liquid solvent extraction process, third phase formation. i.e. the splitting of the organic phase into two layers when extracting high concentration of solutes, like nitric acid or metallic nitrates (here trivalent f ions), is one of the most important to address. In some conditions the formation of a “third phase” is observed with dimethyldibutyltetradecylmalonamide (DMDBTDMA), a potential extractant used in the DIAMEX process We have investigated the phase behavior of the system DMDBTDMA / n-dodecane / water / HNO3, in the acceptable concentration limits for the DIAMEX process.