Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Solid Phase 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 55 records · Page 3Linked to original sources
PubMed2003

Analysis of multiple pesticide residues in tobacco using pressurized liquid extraction, automated solid-phase extraction clean-up and gas chromatography-tandem mass spectrometry.

A new method was developed for the analysis of pesticide residues in tobacco. The objective was to significantly increase the number of samples that can be processed by the laboratory and to enable the extension of the current coverage to additional pesticides. A new analytical approach was therefore defined based on two main axes, the automation of the sample preparation and the selectivity of the analyte detection using tandem mass spectrometry. This latter aspect reduces the stringency of the requirements placed on the clean-up of the extracts and on the chromatographic resolution when less selective detectors are used. The extraction of the analytes from the matrix is performed using the pressurized liquid extraction technique. Tobacco samples are extracted at elevated temperature and pressure (100 C and 100 atm; 1 atm = 101,325 Pa) using acetone as an extraction solvent. The resulting extract is then concentrated using a Vortex evaporator. Three different solid-phase extraction (SPE) procedures, adjusted to the chemical properties of the different active ingredients to be measured, are applied to the concentrated extract, thus leading to three extract fractions. The first fraction contains such main classes of active ingredients as organohalogenated and 2,6-dinitroaniline compounds while the second one collects the organophosphorus and acylalanines residues; these two fractions are analyzed by capillary gas chromatography coupled to tandem mass spectrometry using negative chemical ionization and electron impact ionization in the positive mode, respectively. The third extract fraction gathers the N-methylcarbamates residues which are analyzed by HPLC with post-column derivatization and fluorescence detection. The different sample preparation stages from extraction to SPE clean-up have been automated through the use of recent analytical technologies. In combination with the analysis by tandem mass spectrometry, this provided a potential for a high sample throughput.

Automation↗
PubMed1996

Determination of amisulpride, a new benzamide derivative, in human plasma and urine by liquid-liquid extraction or solid-phase extraction in combination with high-performance liquid chromatography and fluorescence detection. application to pharmacokinetics.

Amisulpride (SOLIAN) belongs to the benzamide series and shows antischizophrenic and antidepressant (anti-dysthymic) properties in man. Two methods suitable for pharmacokinetic investigations are proposed for the determination of amisulpride in human plasma. For the liquid-liquid extraction (LLE) based method, the plasma, added with the internal standard (an amisulpride analogue) is alkalinised with NaOH and extracted with a diethyl ether-chloroform mixture. The organic phase is removed, evaporated to dryness and redissolved in an acidic phosphate-acetonitrile mixture that, after a back-washing step with n-hexane, is injected onto the HPLC column (C18 BDS type) connected with a fluorimetric detector. The second method is based on an automatic solid-phase extraction (SPE) performed on an ASPEC device. The plasma sample, diluted with a pH 9 borate buffer, is loaded onto a disposable SPE C18 100-mg column. The analytes of interest (amisulpride and internal standard), after two washing steps with different solvents, are recovered in pure methanol; after evaporation to dryness, the residue is dissolved in an acidic phosphate buffer and injected onto the chromatographic apparatus already described. The limit of quantitation (LOQ) is 0.5 ng ml-1 for both methods; a linear correlation between concentrations and detector response has been demonstrated in the range 0.5-640 ng ml-1 for LLE, which is the most used method; for SPE methods, less used, linearity has been assessed in the plasma range of 0.5-160 ng ml-1.

Amisulpride↗
PubMed2005

Determination of volatile compounds in grape distillates by solid-phase extraction and gas chromatography.

Solid-phase extraction (SPE) procedure on octadecylsilica (C18) was developed for accumulation of volatile compounds from grape distillates. The procedure was optimised for final analysis by capillary gas chromatography. At mass concentrations in model solutions ranging from 0.1 to 50 mg/l solid-phase extraction recoveries of all analytes ranged from 69% for 2-phenylethanol to 102% for capric acid, with RSD values from 2 to 9%. SPE recoveries of internal standards to be added in the sample solution prior to extraction, higher alcohols 2-ethyl-1-hexanol and 1-undecanol, were 97 and 93%, respectively, with RSD values of 3%. Detection limits of analyzed compounds in model solutions ranged from 0.011 mg/l for isoamyl acetate to 0.037 mg/l for caproic acid. Method efficiency was tested in relation to acetic acid content, volume fraction of ethanol and possible matrix effects. A significant influence of matrix on SPE efficiency for geraniol, cis-2-hexen-1-ol and cis-3-hexen-1-ol was detected. For the same reason, 2-phenylethanol could not be determined by developed SPE method in samples of grape distillates. The developed solid-phase extraction method was successfully applied to determine the differences in volatile compound content in different grape distillates produced by the distillation of crushed, pressed and fermented grapes.

Adsorption↗
PubMed2002

An improved method for acetaldehyde determination in blood by high-performance liquid chromatography and solid-phase extraction.

This study reports on an improved method for acetaldehyde (ACH) determination in blood by high-performance liquid chromatography (HPLC). In the case of HPLC analysis, ACH is generally converted to derivatives for ultraviolet detection (for example 2,4-dinitrophenylhydrazine [DNPH] derivative). Nevertheless, elevation of the background during protein precipitation, hydrazone synthesis, or both frequently results in a serious loss of accuracy and precision of the analysis. The method in this study is developed to minimize the increase in nonspecific ACH-DNPH with a view to optimize mainly the synthetic condition of ACH-DNPH. The background is decreased dramatically by gentle deproteination, optimization of the DNPH amount and reaction pH, and reversed-phase solid extraction for the elimination of excess DNPH reagent. The standard curves show good linearity between 0 and 100 microM and minimal background is observed, indicating that the method is useful for monitoring the ACH concentration in blood.

Acetaldehyde↗
PubMed1996

Stereoselective determination of methadone in serum by HPLC following solid-phase extraction on disk.

A solid-phase extraction (SPE) technique for methadone has been developed using a mixed-mode solid-phase extraction disk which contains both hydrophobic and cation-exchange functional groups. The SPE technique was used to isolate the drug from the biological matrix and to prepare a cleaner sample prior to stereoselective analysis by HPLC on a silica column with covalently bound alpha 1-acid glycoprotein (Chiral-AGP) followed by ultraviolet detection at 205 mm. The within-run precision was less than 5% for the complete method over the therapeutic range. The quantification limit was 25 ng ml-1. The between-run precision was less than 15% at the quantification limit. The between-run precision at other concentrations was less than 8.5% with an accuracy of more than 95%. The mean recovery for R-methadone was 78.5% and the mean recovery for S-methadone was 73.4%. The complete procedure has been validated. This method was successfully used for the analysis of 15 clinical cases.

Analgesics, Opioid↗
PubMed1998

Cleanup and analysis of sugar phosphates in biological extracts by using solid-phase extraction and anion-exchange chromatography with pulsed amperometric detection.

A cleanup method based on anion-exchange solid-phase extraction (SPE) was developed to render biological extracts suitable for the analysis of hexose phosphates with a modified anion-exchange chromatography method and pulsed amperometric detection. The method was applied to cell extracts of Saccharomyces cerevisiae obtained by using cold methanol as quenching agent and chloroform as extraction solvent. It was shown that pretreatment of the cell extract with SPE markedly improved the quality of the liquid chromatography analysis with recoveries of the sugar phosphates close to 100%. Furthermore, the method allowed for sample enrichment and the original extraction procedure could be simplified by implementing SPE early in the extraction protocol.

Cell Fractionation↗
PubMed2000

Isolation and quantification of dissolved lignin from natural waters using solid-phase extraction and GC/MS.

Solid-phase extraction (SPE) was tested for the isolation of dissolved lignin from diverse natural waters (fresh, estuarine, and marine) in preparation for CuO oxidation. Capillary GC coupled to selected-ion monitoring mass spectrometry (SIM-MS) of CuO oxidation products provides the high sensitivity and precision required for the identification and quantification of trace levels of lignin in seawater. The low blanks and quick cleanup of C18 cartridges support SPE for processing such samples. Comparison of SPE with other isolation procedures (direct dry-down and ultrafiltration) has shown that this method quantitatively recovers dissolved lignin and preserves its compositional parameters. The concentration and nature of dissolved organic matter appear to be primary factors that constrain the amount of water that should be processed to obtain quantitative and reproducible recoveries of dissolved lignin using SPE. Highest recoveries of dissolved lignin were obtained at low pH (1.5-4.0) with substantial decreases at pH > 4. Extraction efficiencies were independent of flow rate within a range of five to fifteen bed volumes per minute (50-150 mL min(-1)), and both refrigeration and freezing were appropriate long-term storage methods for processed cartridges prior to elution of retained dissolved lignin.

Gas Chromatography-Mass Spectrometry↗
PubMed2000

Determination of organochlorine and organophosphorus pesticide residues in eggs using a solid phase extraction cleanup.

A multiresidue solid phase extraction (SPE) method for the isolation and subsequent gas chromatographic determination of nonpolar organochlorine and polar organophosphorus pesticide residues in eggs is described. The method uses an acetonitrile extraction followed by an SPE cleanup using graphitized carbon black and aminopropyl SPE columns. Organophosphorus pesticides are determined by gas chromatography with flame photometric detection. After further cleanup of the extract using Florisil SPE columns, organochlorine pesticides are determined by gas chromatography with electron capture detection. Studies were performed using eggs containing both fortified and incurred pesticide residues. The average recoveries were 86-108% for 8 fortified organochlorine pesticide residues and 61-149% for 28 fortified organophosphorus pesticide residues.

Animals↗
PubMedDate not supplied

Isolation of acidic, neutral, and basic drugs from whole blood using a single mixed-mode solid-phase extraction column.

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.

Blood Chemical Analysis↗
PubMed2003

Determination of [18F]FCWAY, [18F]FP-TZTP, and their metabolites in plasma using rapid and efficient liquid-liquid and solid phase extractions.

Liquid-liquid and solid phase extraction methods were developed for the accurate and rapid quantitation of radioactive components in human plasma following injection of two PET ligands. A solid phase extraction (SPE) method was developed for the determination of the 5HT(1A) receptor ligand [N-[2-[4-(2-methoxyphenyl) piperazino]ethyl]-N-(2-pyridinyl) trans-4-[(18)F]fluorocyclohexanecarboxamide (FCWAY), and its acidic metabolite, 4-[(18)F]fluorocyclohexane carboxylic acid (FC). In both cases, the extraction method was much faster and easier to use, yet provided results comparable to HPLC and TLC methods. In addition, an easy to perform two-step liquid-liquid extraction was developed for quantitation of 3-(3-((3-[(18)F]fluoropropyl)thio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine ([(18)F]FP-TZTP), a selective M2 muscarinic agonist.

Chromatography, Thin Layer↗
PubMed2001

Solvent vapour monitoring in work space by solid phase micro extraction.

Solid phase micro extraction (SPME) is a fast, solvent-less alternative to conventional charcoal tube sampling/carbon disulfide extraction for volatile organic compounds (VOC). In this work, SPME was compared to the active sampling technique in a typical lab atmosphere. Two different types of fibre coatings were evaluated for solvent vapour at ambient concentration. A general purpose 100 microm film polydimethylsiloxane (PDMS) fibre was found to be unsuitable for VOC work, despite the thick coating. The mixed-phase carboxen/PDMS fibre was found to be suitable. Sensitivity of the SPME was far greater than charcoal sorbent tube method. Calibration studies using typical solvent such as dichloromethane (DCM), benzene (B) and toluene (T) showed an optimal exposure time of 5 min, with a repeatability of less than 20% for a broad spectrum of organic vapour. Minimum detectable amount for DCM is in the range of 0.01 microg/l (0.003 ppmv). Variation among different fibres was generally within 30% at a vapour concentration of 1 microg DCM/l, which was more than adequate for field monitoring purpose. Adsorption characteristics and calibration procedures were studied. An actual application of SPME was carried out to measure background level of solvent vapour at a bench where DCM was used extensively. Agreement between the SPME and the charcoal sampling method was generally within a factor of two. No DCM concentration was found to be above the regulatory limit of 50 ppmv.

Adsorption↗
PubMed2004

Analysis of wheat extracts for ochratoxin A by molecularly imprinted solid-phase extraction and pulsed elution.

A molecularly imprinted solid-phase extraction (MISPE) method has been developed for the rapid analysis of wheat extracts for ochratoxin A (OTA). Molecularly imprinted polymer (MIP) particles were synthesized from N-phenylacrylamide (PAM) and slurry-packed into a micro-column for selective solid-phase extraction (SPE) of OTA. With water flowing at 0.5 mL min(-1), a total binding capacity of 30 ng OTA was determined for the 20 mg of MIP particles. MISPE conditions were optimized using OTA in methanol/acetic acid (99:1 v/v). Nearly 100% binding could be achieved from one 20-microL injection of sample containing up to 30 ng of OTA. Pulsed elution (PE) using methanol/triethylamine (99:1 v/v) was good for the quantitative desorption of OTA. The MISPE-PE method, with fluorescence detection at lambda(ex)=385 nm and lambda(em)=445 nm, afforded a detection limit of 5.0 ng mL(-1) (or 0.1 ng in 20 microL of sample injected) for OTA. Recovery of OTA from wheat extracts was 103+/-3%. Each MISPE-PE analysis required less than 5 min to complete.

Acrylamide↗
PubMed2004

Simultaneous extraction of tetracycline, macrolide and sulfonamide antibiotics from agricultural soils using pressurised liquid extraction, followed by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

The veterinary antibacterial agents chlortetracycline (CTC), oxytetracycline (OTC), sulfadiazine (SDZ), erythromycin (ERY) and tylosin (TYL A, B, C and D) were extracted from soil using pressurized liquid extraction (PLE). Citric acid (pH 4.7) and methanol was used as extraction buffer, followed by tandem-solid-phase extraction (SPE) clean-up (SAX + HLB) for all compounds. For quantification two slightly different methods were employed using LC-MS-MS with MRM detection. The soil extraction method was validated using a loamy sand soil and a sandy soil, representing two typical Danish agricultural soils. Recoveries were 50-80% for the tetracyclines (CTC and OTC) and sulfadiazine (SDZ) and 60-100% for the macrolides (TYL and ERY). Limits of detection for the soil extraction method (LOD(soil)) were 0.6-5.6 microg kg(-1) soil for CTC and OTC, 0.9-2.9 microg kg(-1) soil for SDZ and 2.4-5.5 microg kg(-1) soil for TYL A and ERY. Furthermore, the method was applied to field samples taken from two agricultural fields fertilised with liquid manure containing CTC and TYL A. These results showed a decline in the content of antibacterial agents throughout the sampling period of 155 days from 10 to 15 microg CTC kg(-1) soil and 20-55 microg TYL A kg(-1) soil to below or near the LOD(soil) listed above. Finally, the method was applied to barley grains harvested from the fields. None of the antibacterial agents were measured in grain samples, but recoveries for spiked grain samples were similar to soil recoveries.

Anti-Bacterial Agents↗
PubMed2000

Static subcritical water extraction with simultaneous solid-phase extraction for determining polycyclic aromatic hydrocarbons on environmental solids.

A rapid and very simple method for extracting polycyclic aromatic hydrocarbons (PAHs) from soils, sediments, and air particulate matter has been developed by coupling static subcritical water extraction with styrene-divinylbenzene (SDB-XC) extraction discs. Soil, water, and the SDB-XC disc are placed in a sealed extraction cell, heated to 250 degrees C for 15 to 60 min, cooled, and the PAHs recovered from the disc with acetone/methylene chloride. If the cells are mixed during heating, all PAHs with molecular weights from 128 to 276 are quantitatively (>90%) extracted and collected on the sorbent disc and are then recovered by shaking with acetone/methylene chloride. After water extraction, the sorbent discs can be stored in autosampler vials without loss of the PAHs, thus providing a convenient method of shipping PAH extracts from field sites to the analytical laboratory. The method gives good quantitative agreement with standard Soxhlet extraction, and with certified reference materials for PAH concentrations on soil, sediment (SRM 1944), and air particulate matter (SRM 1649a).

Environmental Pollutants↗
PubMed1994

Extraction, purification by solid-phase extraction and high-performance liquid chromatographic analysis of taxanes from ornamental Taxus needles.

Needles from ornamental yews (Taxus spp.) are known to contain significant amounts of the anticancer agent Taxol (paclitaxel), as well as other analogous taxane compounds. Methanol extracts the taxanes from the needles efficiently, but the crude methanolic extract contains large amounts of co-extractives in addition to the taxanes of interest. The crude extract may be fractionally partitioned using C18 solid-phase extraction (SPE), permitting the collection of a fraction in which the taxanes elute quantitatively. This fraction can then be analyzed directly by means of high-performance liquid chromatography. We have successfully scaled-up the quantity of crude extract partitioned by means of the SPE technique, using larger SPE cartridges prepared in our laboratory as well as using Empore extraction disks. SPE using the Empore disks permits us to collect large quantities of the taxane fraction for studies on its cytostatic effect on non-mammalian eukaryotic cells.

Chromatography, High Pressure Liquid↗
PubMed2005

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

A sample preparation method based on single solvent phase extraction and solid-phase extraction (SPE-NH2) clean-up is studied in combination with fast capillary gas chromatography (GC) to determine 18 selected pesticides belonging to various chemical classes in apples, the common raw material for baby food production and baby food, at the concentration level < or = 10 microg/kg maximum residual limit (MRL). Possibilities of mass spectrometry (MS) detector and electron capture detector (ECD) in fast gas chromatography (GC) of samples with complex matrice at ultra trace levels of pesticide residues were studied and compared. MS detection in single ion monitoring (SIM) mode provided higher selectivity compared to ECD. Optimisation of extraction as well as the simplifying of the whole process of sample preparation was carried out. Recoveries obtained at concentration level of 5 microg/kg (the required value for limit of quantification (LOQ) in baby food) were >90%, except of dimethoate (77.7%) and captan (46.4%) with MS detection. The obtained LOQs were at least 1 order lower than 5 microg/kg for the majority of compounds. The repeatability of gas chromatography-mass spectrometry (GC-MS) measurements of the matrix matched standards expressed as relative standard deviation was <11% except of captan and cypermethrin.

Chromatography, Gas↗
PubMed2002

Determination of fluoroquinolone antibacterial agents in sewage sludge and sludge-treated soil using accelerated solvent extraction followed by solid-phase extraction.

A method for the quantitative determination of humanuse fluoroquinolone antibacterial agents (FQs) ciprofloxacin and norfloxacin in sewage sludge and sludge-treated soil samples was developed. The accelerated solvent extraction was optimized with regard to solvents and operational parameters, such as temperature, pressure, and extraction time. A 50 mM aqueous phosphoric acid/ acetonitrile mixture (1:1) was found to be optimum in combination with an extraction temperature of 100 degrees C at 100 bar, during 60 and 90 min for sewage sludge and sludge-treated soil samples, respectively. A cleanup step using solid-phase extraction substantially improved the selectivity of the method. Overall recovery rates for FQs ranged from 82 to 94% for sewage sludge and from 75 to 92% for sludge-treated soil, with relative standard deviations between 8 and 11%. Limits of quantification were 0.45 and 0.18 mg/kg of dry matter for sewage sludge and sludge-treated soils, respectively. The presented method was successfully applied to untreated and anaerobically digested sewage sludges and sludge-treated soils. Ciprofloxacin and norfloxacin were determined in sewage sludges from several wastewater treatment plants with concentrations ranging from 1.40 to 2.42 mg/kg of dry matter. Therefore, contrary to what may be expected for human-use pharmaceuticals, FQs may reach the terrestrial environment as indicated by the occurrence of FQs in topsoil samples from experimental fields, to which sewage sludge had been applied.

Anti-Infective Agents↗
PubMed1996

Comparison of new solid-phase extraction methods for chromatographic identification of drugs in clinical toxicological analysis.

OBJECTIVES: Newly presented solid-phase extraction methods (Solid Phase Disc Extraction, SPEC-Plus, Multi-Modal, and Solid Phase Micro Extraction, SPME have been checked with respect to their applicability to clinical toxicological analysis. In comparison with conventional liquid/liquid-extraction and a common mixed-phase column technology, their use in general screening and selective extraction methodology is discussed. DESIGN AND METHODS: Recovery studies were performed with urine-based samples including model substances, as well as drugs and metabolites from native urine samples. Chromatographic performance of the resulting extracts is presented in some examples. RESULTS: Liquid/liquid extraction, common mixed-phase column technique and the new SPEC-Plus, Multi-Modal disc extraction method gave the best recoveries with respect to broad-spectrum general screening. The purity of the concentrates was somewhat different, however. Solid-phase C18 and Solid-Phase Micro Extraction methodologies are better suited for selective drug extraction. In SPEC Disc or SPME extraction, the use of solvents is greatly reduced or omitted. Recovery of some volatile substances is enhanced. SPEC discs can be inserted directly into TLC chromatographic plates, SPME fibers into GC injection ports. CONCLUSIONS: The new solid-phase extraction technologies offer advantages in different respects: The mixed-phase disc extraction SPEC 1 Plus AR/MP3 Multi-Modal delivers promising results with respect to broad-spectrum general screening. Solvent consumption is low, throughput times are short, the extracts are clean, and recovery rates are good, comparable, or even higher than with common mixed-phase column techniques. The new SPME extraction method shows benefits in dedicated, selective extraction procedures (e.g., analysis of volatile substances such as amphetamines). Sampling is solvent-free, the handling is easy, and the yields of extraction are good, but only for selected substances. Broad-spectrum general screening still remains problematic with this technique. Further examinations have to be carried out including a larger number of drugs of toxicological relevance. Headspace sampling by SPME offers a good alternative to conventional mechanized sampling in the analysis of volatile substances in biological samples, omitting the need for expensive instrumentation.

Blood Chemical Analysis↗