Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “selective extraction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMed2001

Selectivity of solid-phase extraction phases in the determination of biodegradation products.

The extraction techniques connected with gas chromatography were used to describe quantitatively and qualitatively the biodegradation process. We investigated the biodegradation of hydrocarbons and non-ionic surfactants. Solid-phase extraction (SPE) and liquid-liquid extraction were used for the isolation of the non-degraded compounds and their degradation products. The selectivity of SPE has a significant influence on the isolation and preconcentration of organic compounds from water.

Biodegradation, Environmental↗
PubMed2000

Microtox testing of pentachlorophenol in soil extracts and quantification by capillary electrochromatography (CEC)--a rapid screening approach for contaminated land.

An approach to rapid soil testing which involved the use of simple solvent extraction methods was developed. The analytes of interest were priority pollutants of low water solubility which could not be readily removed from the soil using water. Direct toxicity testing of the soil samples by Microtox showed a high background toxicity which prevented realistic toxicity data from being obtained for the contaminants present. A range of different extraction solutions was used in an attempt to extract the contaminants while eliminating the matrix effects of the soil. It was necessary that the solvents selected for extraction of the soil samples were not of significant toxicity, as this could potentially mask the toxic effects of any compounds extracted from the soil. The extraction efficiencies of solvent systems were evaluated using pentachlorophenol (PCP) as a model compound of known toxicity in the Microtox assay. A rapid and cost-effective method was developed in order to determine the amount of PCP recovered from the soil by the extraction solvents employed. This method consisted of a solid phase extraction (SPE) step followed by quantification using capillary electrochromatography (CEC). Recoveries were greater when a higher proportion of organic solvent (methanol) was used in the extraction process, and lowest when water was used. An extraction based on water could provide information on the potential for leaching of contaminants from the soil into nearby water bodies in an environmental setting. An organic solvent extraction method could indicate how much toxicity soil-dependent organisms might be exposed to through ingestion. Extraction based on 50% (v/v) methanol in water was considered to be the most suitable overall extraction solution for soil screening, given that this permitted extraction of the water-insoluble compound PCP at a level which was clearly toxic in the Microtox assay while also retaining the capability to extract water-soluble contaminants.

Chemistry Techniques, Analytical↗
PubMed2003

Ionic liquids as a novel solvent for lanthanide extraction.

Octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) dissolved in an ionic liquids, 1-butyl-3-methyl-imidazolium hexafluorophosphate, greatly enhances extractability and selectivity of lanthanide cations compared to that dissolved in conventional organic solvents; further, the recovery of lanthanides extracted into ionic liquids can be accomplished using several stripping solutions containing complexing agents. The possibility of utilizing ionic liquids as novel separation media in an industrial liquid-liquid extraction process was demonstrated.

Journal Article↗
PubMed1995

Determination of the anti-platelet-activating factor BN-50727 and its metabolites in human plasma by high-performance liquid chromatography-solid-phase extraction.

A sensitive and selective HPLC-solid-phase extraction procedure was developed for the determination of platelet-activating factor antagonist BN-50727 and its metabolites in human plasma. The procedure consisted of an automated solid-phase extraction of the drug and metabolites on disposable propylcarboxylic acid cartridges, followed by on-line chromatographic separation. The method was linear from 3.75 to 2400 ng/ml and the limit of quantitation for BN-50727 in plasma samples was 3.75 ng/ml. The within-run precision of the method, expressed as relative standard deviation, ranged from 2.1 to 8.1%. The accuracy, expressed as relative error, ranged from -3.5 to 4.0%. For the main metabolite, the O-demethylated BN-50727 product, the method was linear from 7.5 to 2400 ng/ml and the limit of quantitation in plasma was 7.5 ng/ml. The within-run precision ranged from 2.1 to 11.0% and the accuracy from -5.3 to 1.1%. This paper describes the validation of the analytical methodology for the determination of BN-50727 in human plasma and also of its metabolites. The method has been used to follow the time course of BN-50727 and its metabolites in human plasma after administration of single and multiple doses.

Azepines↗
PubMed1996

Determination of the anti-platelet-activating factor BN-50727 and metabolites in human urine by high-performance liquid chromatography using solid-phase extraction.

A sensitive and selective HPLC solid-phase extraction procedure was developed for the determination of platelet-activating factor antagonist BN-50727 and its metabolites in human urine. The procedure consisted in a double solid-phase extraction of the urine samples on cyanopropyl and silica cartridges, followed by an automated solid-phase extraction of the drug and metabolites on CBA cartridges and posterior elution on-line to the chromatographic system for its separation. The method allowed quantitation in the concentration range 10-2400 ng/ml urine for both BN-50727 and the main metabolite, the O-demethylated BN-50727 product. The limit of quantitation for both compounds was 10 ng/ml. The inter-assay precision of the method, expressed as relative standard deviation, ranged from 1.9 to 4.5% for BN-50727 and from 2.5 to 9.0% for the metabolite. The accuracy, expressed as relative error, ranged from -2.4 to 4.2% and from 0.2 to 6.2%, respectively. This paper describes the validation of the analytical methodology for the determination of BN-50727 in human urine and also for its metabolites. The method has been used to follow the time course of BN-50727 and its metabolites in human urine after single-dose administration.

Azepines↗
PubMed2006

Multicriteria optimisation of a simultaneous supercritical fluid extraction and clean-up procedure for the determination of persistent organohalogenated pollutants in aquaculture samples.

A useful tool based on a single-step extraction and clean-up procedure for the determination of 15 organohalogenated pollutants (including brominated flame retardants) in aquaculture samples, using aluminium oxide basic and acidic silica gel in the supercritical extraction cell followed by gas chromatography with electron capture detection or mass spectrometry has been developed. This effective clean-up step ensures a minimum of chromatographic difficulties related to complex matrix components such as aquaculture feed. The extraction procedure has been screened by a fractional factorial design for the preliminary statistically significant parameters. The factors selected were extraction temperature, pressure, static extraction time, dynamic extraction time and carbon dioxide flow rate. The Doehlert design, followed by a multicriteria decision-making strategy, was then performed in order to determine the optimum conditions for the two most significant factors: pressure (165 bar) and dynamic extraction time (27 min). Under optimal conditions, the procedure developed with GC-MS/MS provides an excellent linearity, detection (0.01-0.2 ng g(-1)) and quantification limits (0.05-0.8 ng g(-1)) for most of the analytes investigated. The feasibility of the proposed supercritical fluid extraction method was validated by analysing two reference materials and fish feed and shellfish samples with satisfactory results.

Animal Feed↗
PubMed2003

Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides.

Two calix[4]arene tetraethers (Y = C5H11, C14H29) bearing on their wide rim four -N(Me)-CO-CH2-P(O)Ph2 residues were synthesized for the first time. Their ability to extract lanthanides and actinides from an acidic aqueous phase to organic phases (CH2Cl2, NPHE) was studied. In comparison to the corresponding -NH-analogs, they are less efficient extractants, the selectivity for the light over the heavy lanthanides is less pronounced, while there is still an interesting selectivity of Am3+ over Eu3+. Stability constants for selected lanthanide salts were determined also in homogenous phase (methanol, acetonitrile) but do not account for the different extraction results. The complexation of Gd3+ was also followed by relaxivity (NM RD) measurements, which suggest an even stronger aggregation for the N-methyl compound while the 1:1 complex is reached for a smaller ratio [L]/[Gd3+] compared to the NH analog. The formation of aggregates is also supported by dynamic light scattering measurements. A single crystal X-ray structure of the pentyl ether reveals a C2-symmetrical pinched cone conformation for the free ligand.

Journal Article↗
PubMed2003

Use of solid phase microextraction (SPME) for profiling fungal volatile metabolites.

AIMS: The influence of isolation methods: solid phase microextraction (SPME) with different fibres and simultaneous distillation extraction (SDE) on the profile of isolated fungal volatile metabolites was investigated. METHODS AND RESULTS: Four SPME fibre types: Polydimethylsiloxane, Polyacrylate, Carboxen/PDMS and Carboxen/Divinylbenzene/PDMS were evaluated in terms of their efficiency in extracting volatile metabolites emitted by Penicillium roqueforti grown on wheat kernel medium. All fibres showed varied efficiency and selectivity in extracting volatile compounds. Sesquiterpene hydrocarbons were the predominant fraction of volatile compounds isolated by all fibres, and ranged from 55.4 to 93.7% of all volatiles depending on the type of fibre used. Alcohols and ketones ranged from 2.7 to 20.5%, esters from 1.2 to 12.8%, and monoterpene hydrocarbons from 1.2 to 5.4%. Profile of volatile compounds obtained by SDE differed from SPME and the oxygenated sesquiterpenes formed the predominant fraction of volatiles isolated using SDE. SIGNIFICANCE AND IMPACT OF THE STUDY: The data in this study show that analysed profile of volatile compounds emitted by fungi is highly dependent on the extraction method.

Fungi↗
PubMed1991

Aeroallergen analyses and their clinical relevance. I. Immunochemical quantification of allergens by RAST-inhibition, Mab-ELISA, basophil histamine release, and counter current immuno electrophoresis.

The aim was to compare IgE and IgG4 RAST-inhibition assay (RI), monoclonal antibody ELISA (Mab-ELISA), counter current immuno electrophoresis (CCIE) and histamine release from basophil leukocytes (HR) for allergen quantification with special reference to aeroallergen detection. As components of indoor aeroallergens, cat, dog, and Derm. pter. allergen extracts were selected for the experiments. To evaluate unspecific interference, these allergens were compared mutually and with Cladosporium herbarum. Allergen extracts in varying dilutions were mixed with crushed glass fibre filter materials, eluted, recovered by centrifugation, and allergen concentration quantified by the assays. Equal sensitivity was found for both IgE- and IgG4-RI assaying cat allergen (in the range 5-50 SQ-U/ml) and dog allergen (in the range 10(2)-10(3) SQ-U/ml). The IgG4-RI assaying Derm. pter. was more sensitive (50 SQ-U/ml) than IgE-RI (2*10(3) SQ-U/ml). The ranges of allergen detection limits for the Mab-ELISA were equal for cat and Derm. pter. (10-10(2) SQ-U/ml). The range of allergen detection limits for CCIE, assaying dog were 10(4)-10(5) SQ-U/ml. The ranges of allergen detection limits for HR were equal for cat and Derm. pter. (10-10(2) SQ-U/ml), and 10(2)-10(3) SQ-U/ML for dog. Because of cross-reactivity, a minor degree of interference was observed in the IgE-RI and the HR test for the highest concentration of cat and dog allergens.

Air Pollutants↗
PubMed2002

Towards ochratoxin A selective molecularly imprinted polymers for solid-phase extraction.

Molecularly imprinted polymers (MIPs) displaying selective binding properties for the mycotoxin ochratoxin A (OTA) in polar/protic media were prepared. Crucial to the success of these efforts was the implementation of rationally designed OTA mimics as templates and a set of novel basic and neutral functional monomers, allowing the maximization of the template-functional monomer association via ion-pairing, hydrophobic and steric interactions. MIPs prepared with a 20:1:1:3 molar ratio of cross-linking agent, template mimic, basic functional monomer and hydrophobic auxiliary monomer produced polymers with superior recognition properties compared to materials generated with other stoichiometries. Chromatographic evaluation using the OTA mimics, OTA and a set of structurally closely related compounds as analytes revealed pronounced substrate selectivity of these MIPs in polar/protic media, the templates and OTA being bound with significantly higher affinities. Complementary substrate selectivities/affinities were observed in aprotic and apolar solvents. The possibility of solvent-dependent tuning of substrate selectivity/affinity and the high binding capacity recommend the developed MIPs as promising solid-phase extraction adsorbents for clean-up and pre-concentration of OTA from various biologically relevant matrices.

Magnetic Resonance Spectroscopy↗
PubMed2000

Synthesis and evaluation of a molecularly imprinted polymer for selective on-line solid-phase extraction of 4-nitrophenol from environmental water.

A molecularly imprinted polymer (MIP) able to bind 4-nitrophenol (4-NP) was prepared using noncovalent molecular imprinting methods and evaluated as a selective sorbent in molecularly imprinted solid-phase extraction (MISPE) on-line coupled to a reversed-phase HPLC. It has been shown that the conditions chosen for washing the MIP and for eluting the analyte in the MISPE process are extremely important for ensuring good selectivity and recovery. River water samples, spiked with the 11 Environmental Protection Agency phenolic compounds at microgram per liter levels, were preconcentrated on-line using this MIP, and 4-NP was selectively extracted. The humic acid interference was simultaneously reduced considerably. The MIP was also compared with a commercially available highly cross-linked polymer (LiChrolut EN) and the former yielded cleaner extracts.

Chromatography, High Pressure Liquid↗
PubMed2002

Aggregation of peptides during hydrolysis as a cause of reduced enzymatic extractability of soybean meal proteins.

With the purpose of analyzing the size and composition of enzyme-unextractable proteins in differently heat-treated soybean meals, a selection of extractants was screened for their ability to extract these proteins from enzyme-unextractable residues. The largest effects were obtained with urea, urea plus beta-mercaptoethanol, and dilute alkali; the latter extracted up to 87% of the enzyme-unextractable protein. Gel permeation chromatography indicated that a large proportion of the extracted material was of high molecular weight. However, the combined results from gel electrophoresis, LC-MS, and MALDI-ToF MS showed that the extracted protein material was composed of aggregated peptides. The largest aggregates were observed in the enzymatic residues originating from meals heat-treated at high humidity. Extracted aggregates were fully degraded upon subsequent proteolytic treatment.

Amino Acids↗
PubMed2006

Determining whether delayed nonarteritic ischemic optic neuropathy associated with cataract extraction is a true entity.

PURPOSE: To evaluate cases of delayed nonarteritic anterior and posterior ischemic optic neuropathy after cataract extraction and to evaluate the need for centralized prospective reporting of nonarteritic ischemic optic neuropathy after cataract extraction. SETTING: Neuro-ophthalmology Clinics, University of Colorado Health Sciences Center and Denver Veterans Affairs Medical Center, Denver, Colorado, USA. METHODS: A retrospective review of all patients referred to the Neuro-ophthalmology Divisions, University of Colorado Health Sciences Center and Denver Veterans Affairs Medical Center, from January 2001 to October 2005 was performed. All patients with a diagnosis of nonarteritic anterior or posterior ischemic optic neuropathy were identified. Patients with ischemic optic neuropathy that occurred between 2 months and 12 months after cataract extraction were selected for evaluation. RESULTS: Six eyes with nonarteritic ischemic optic neuropathy that occurred 2 to 6 months after cataract extraction in 4 patients (2 bilateral nonarteritic ischemic optic neuropathy) and 1 eye with nonarteritic ischemic optic neuropathy that occurred after 6 months in 1 patient were identified. One patient had nonarteritic ischemic optic neuropathy in 1 eye 3 months after cataract extraction and 4 years later had nonarteritic ischemic optic neuropathy in the fellow eye 5 months after cataract extraction. Follow-up after the last cataract extraction was 1 to 3 years for all patients. CONCLUSIONS: Although an association between cataract extraction and delayed nonarteritic anterior and posterior ischemic optic neuropathy has been suggested, current data do not support a causal relationship. In addition, the window of postoperative susceptibility for delayed ischemic optic neuropathy after cataract extraction is unclear.

Aged↗
PubMed1997

Chronic venous insufficiency and venous ulceration.

OBJECTIVE: To review and summarize the literature on the normal venous circulation of the leg, and the epidemiology, pathophysiology, and treatment of chronic venous insufficiency (CVI). DATA SOURCES: English-language articles identified through a MEDLINE search (1966-1996) using the terms venous insufficiency or varicose ulcer and epidemiology, pathophysiology, diagnosis, and clinical trial (pt), and selected cross-references. STUDY SELECTION: Articles on epidemiology, pathophysiology, and treatment of CVI. Randomized, controlled studies were specifically sought for treatment efficacy. DATA EXTRACTION: Data were manually extracted from selected studies and reviews: emphasis was placed on information relevant to the general internist. DATA SYNTHESIS: Chronic venous insufficiency is a common primary care problem associated with significant morbidity and health care costs. The clinical spectrum of disease ranges from minor cosmetic concerns to severe fibrosing panniculitis and ulceration. Duplex Doppler ultrasonography may be the single best test to rule out deep venous thrombosis and other entities that can mimic CVI. Leg elevation and compression stockings are effective treatments for CVI; recalcitrant cases may require intermittent pneumatic compression. Topical antiseptics, antibiotics, enzymes, or growth factors offer no clear advantages in ulcer healing. Ulcer dressings remain a matter of convenience, cost, and physician judgment. The role of surgery in CVI appears to be limited. CONCLUSIONS: Chronic venous insufficiency is a recalcitrant, recurrent medical problem. This condition can be managed by primary care physicians with relatively inexpensive treatment modalities in association with lifestyle modification.

Chronic Disease↗
PubMed2006

Extracts from Pygeum africanum and other ethnobotanical species with antiandrogenic activity.

Extracts from Pygeum africanum, Serenoa repens and Cucurbita pepo are used in the treatment of benign prostatic hyperplasia (BPH) and prostate cancer (PCa). The activity of the androgen receptor (AR) is known to control growth of the prostate. Here, we examined extracts of these plants for their antiandrogenic activity using an AR responsive reporter gene assay for drug discovery. A selective dichloromethane extract from the stem barks of Pygeum africanum revealed the highest antiandrogenic effect. Bioactivity-directed fractionation of this extract led to the isolation of N-butylbenzenesulfonamide (NBBS) indicating that extracts of the stem bark of P. africanum harbour androgen antagonistic activity. This compound may provide a novel approach for the prevention and treatment of BPH and human PCa.

Androgen Antagonists↗
PubMed1981

Purified glucocorticoid receptors bind selectively in vitro to a cloned DNA fragment whose transcription is regulated by glucocorticoids in vivo.

Activated glucocorticoid receptor protein, purified to 40-60% homogeneity from rat liver extracts, binds selectively in vitro to a cloned fragment of murine mammary tumor virus (MTV) DNA. The DNA fragment tested contains about half of the sequences present in intact MTV DNA, and its rate of transcription, like that of the intact viral element, is strongly stimulated by glucocorticoids when it is introduced into the genome of a receptor-containing cell. In contrast, the receptor fails to bind selectively to DNA restriction fragments from E. coli plasmids pBR322 and RSF2124 or from bacteriophages lambda and T4. Preliminary experiments to localize regions within MTV DNA responsible for selective binding have revealed thus far one subfragment that fails to bind the receptor and one selectively bound subfragment that maps far downstream from the 5' terminus of the normal RNA transcript. These studies are consistent with the notion that steroid receptors may modulate rates of transcription by recognizing specific DNA sequences within or near the regulated genes.

Animals↗
PubMed1985

U2 as well as U1 small nuclear ribonucleoproteins are involved in premessenger RNA splicing.

Two different experimental approaches have provided evidence that both U2 and U1 snRNPs function in pre-mRNA splicing. When the U2 snRNPs in a nuclear extract are selectively degraded using ribonuclease H and either of two deoxyoligonucleotides complementary to U2 RNA, splicing activity is abolished. Mixing an extract in which U2 has been degraded with one in which U1 has been degraded recovers activity. Use of anti-(U2)RNP autoantibodies demonstrates that U2 snRNPs associate with the precursor RNA during in vitro splicing. At 60 min, but not at 0 min, into the reaction intron fragments that include the branch-point sequence are immunoprecipitated by anti-(U2)RNP. At all times, U1 snRNPs bind the 5' splice site of the pre-mRNA. Possible interactions of the U2 snRNP with the U1 snRNP and with the pre-mRNA during splicing are considered.

Base Sequence↗
PubMed2002

[Laparoscopic transcystic biliary calculus extraction with Dormia basket].

We describe transcystic common bile duct (CBD) stone extraction using Dormia basket in patients with preoperatively unexpected CBD stones during laparoscopic cholecystectomy (LC). We perform intraoperative cholangiography (IOC) selectively. Stone extraction was successful five times and we converted to open procedure in one patient because of the size of the stone. Mild postoperative acute pancreatitis developed once. No other complication was detected. Procedures performed if CBD stone is detected intraoperatively are evaluated in the article, including indications and difficulties of the Dormia basket method. We suggest the introduction of the method as an alternative treatment for unexpected CBD stones during laparoscopic cholecystectomy.

Biliary Tract Surgical Procedures↗