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Solid-phase Extraction Method (solid-phase + extraction_method)
Selected AbstractsInfluence of sediment ingestion and exposure concentration on the bioavailable fraction of sediment-associated tetrachlorobiphenyl in oligochaetes,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2008Arto J. Sormunen Abstract The desorption and bioavailability of 3,3,,4,4,-tetrachlorobiphenyl (PCB 77) were studied in spiked natural sediments at six concentrations. The desorption kinetics were measured in a sediment,water suspension using Tenax® resin extraction, and the bioavailability was measured by exposing Lumbriculus variegatus (Oligochaeta) to PCB 77,spiked sediment in a 14-d kinetic study. In addition, freely dissolved pore-water concentrations were measured using the polyoxymethylene solid-phase extraction method. The present study examined whether bioavailability can be defined more accurately by measuring the size of desorbing fractions and the pore-water concentrations than by using the standard equilibrium partitioning approach. The importance of ingested sediment in bioaccumulation also was investigated. Our data showed a clear, decreasing trend in the rapid-desorbing fractions and in the standard biota,sediment accumulation factors (BSAF) with increasing concentration in sediment. Desorbing fractions,refined BSAFs were more uniform across the concentration treatments, and the pore-water PCB 77 concentration predicted tissue concentrations close to observed values. In the risk assessment process, pore-water concentration or desorbing fractions would lead to more precise bioavailability estimates compared with those from the traditional equilibrium partitioning approach. The result also showed, however, that sediment-ingesting worms had access to an additional bioavailable chemical fraction that was especially evident when PCB 77 pore-water concentrations most likely approached the solubility limit. Thus, feeding may modify the bioavailable fraction that cannot be explained by simple equilibrium partitioning models. [source] Isolation and characterisation of selected germander diterpenoids from authenticated Teucrium chamaedrys and T. canadense by HPLC, HPLC-MS and NMRPHYTOCHEMICAL ANALYSIS, Issue 4 2006P. Ramnathan Sundaresan Abstract Teucrium species, such as germander, are rich in neo -clerodane diterpenoids and have been used in traditional folk medicine for their stimulant, diuretic, antipyretic and antiseptic properties. However, the furano neo -clerodane diterpenoids present in germander have been implicated in the in vivo hepatotoxicity of this botanical. In this study, authenticated germander (Teucrium chamaedrys L. and Teucrium canadense L.) was used as the source material. Methanol extracts of powdered plant material were prepared and analysed by HPLC using Synergi® Max-RP columns with monitoring at 220 nm. Limited amounts of teucrin A and other diterpenoid standards were analysed on a Synergi Max-RP column in order to determine their retention times and to generate calibration curves. The same standards were subjected to concurrent mass spectral analysis. Teucrin A and diterpenoids such as dihydroteugin, teuflin, teuflidin and teucvidin were tentatively identified in the plant extracts by HPLC-MS and 1H-NMR experiments. For the isolation of teucrium diterpenoids on a semipreparative scale, a solid-phase extraction method was developed for the first time using styrene divinylbenzene and strata-X sorbents for teucrin A and teuflin, respectively. Semi-preparative HPLC of the methanol extract of the powdered aerial parts of Teucrium plants was carried out on a semipreparative Synergi Max-RP column with photodiode array detection in order to confirm the identities of some diterpenoids by HPLC-MS and NMR. Copyright © 2006 John Wiley & Sons, Ltd. [source] Analysis of estrogenic contaminants in river water using liquid chromatography coupled to ion trap based mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2002Tom Benijts A precise and reliable method, using liquid chromatography combined with ion trap based mass spectrometry, for the determination of three endogenous estrogens, namely, estrone, estradiol, and estriol, and two synthetic estrogens, ethinyl estradiol and diethylstilbestrol, in environmental water samples was developed. Optimization of the parameter settings of the ion source and mass analyzer as well as evaluation of solvent composition were carried out by continuous introduction of standards through a syringe pump. In negative ion mode the electrospray ionization source gave acceptable results. The optimum solvent used consisted of water/acetonitrile, with no volatile bases or buffers added. A simple, off-line, manual solid-phase extraction method was developed for sample preparation of environmental water samples. Recoveries were over 86% for all compounds. The method was validated and found to be linear, selective, and robust. For analysis of a 50-mL sample, the limit of detection (LOD) ranged from 3.2 to 10.6,ng/L for all compounds, and the limit of quantitation (LOQ) from 10.6 to 35.0,ng/L. Within-day (n,=,5) and total (n,=,5) reproducibility were investigated at three different concentration levels and ranged from 6.2 to 9.5% and 9.4 to 12.1%, respectively. Finally, the method was applied to real-world samples. Copyright © 2002 John Wiley & Sons, Ltd. [source] A solid-phase extraction method for high-performance liquid chromatographic determination of salvianolic acid B in rabbit plasma: application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 2 2007Yueming Ma Abstract A sensitive solid-phase extraction/high-performance liquid chromatographic method with ultraviolet detection was established for the analysis of salvianolic acid B in rabbit plasma. The analyte was separated on a reversed-phase column with trifluoroacetic acid,methanol,acetonitrile (70:10:20, v/v/v) as mobile phase at a flow rate of 1 mL/min, and ultraviolet detection at 315 nm. The calibration curve for salvianolic acid B was linear over the range 35,1400 µg/L with coefficients of correlation >0.999. The inter-day and intra-day precisions of analysis were <15%, and assay accuracy ranged from 95.3 to 109.1%. This method is suitable for determining salvianolic acid B in plasma and thus investigating the pharmacokinetics of salvianolic acid B. Copyright © 2007 John Wiley & Sons, Ltd. [source] Determination of S -phenylmercapturic acid in human urine using an automated sample extraction and fast liquid chromatography-tandem mass spectrometric methodBIOMEDICAL CHROMATOGRAPHY, Issue 6-7 2006Yinghe Li Abstract S -phenylmercapturic acid is widely accepted as a specific biomarker for the evaluation of benzene exposure. Here, we describe a fast, specific and sensitive high-performance liquid achromatography coupled with tandem mass spectrometry (LC-MS/MS) method that has been developed and validated for the determination of S- phenylmercapturic acid in human urine. Isotope-labeled S- phenylmercapturic acid- d5 was used as internal standard to improve the method ruggedness. The fully automated solid-phase extraction method on a 96-well Oasis MAX (mix-mode anion exchange) plate was employed to clean up the urine samples before analysis. The rapid LC-MS/MS analysis of extracted samples was achieved on a Genesis C18 column with a run time of only 3 min. Negative electrospray ionization with multiple reaction monitoring (ESI-MRM) mode was used to detect S- phenylmercapturic acid (m/z 238 , 109) and S- phenylmercapturic acid - d5 (m/z 243 , 114). The method fulfils all the standard requirements of method validation. The calibration curve was linear within the concentration range 0.400,200 ng/mL. The method performed accurately and precisely in validation with <7.5% relative error and <6.5% relative standard deviation of quality control samples. The method efficacy was also verified by the analysis of urine samples from 12 smokers and 12 non-smokers. With the fully automated sample cleanup procedure and the fast LC-MS/MS analysis, a sample analysis throughput of 384 samples per day could be achieved. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||