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On-line Solid-phase Extraction (on-line + solid-phase_extraction)
Selected AbstractsOn-line solid-phase extraction with a monolithic weak cation-exchange column and simultaneous screening of ,1-adrenergic receptor antagonists in human plasmaJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007Xiaoyi Wei Abstract An on-line SPE,HPLC method, using a monolithic poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (poly(GMA-EDMA)) based weak cation-exchange (WCX) column, was developed for simultaneous determination of ,1-adrenergic receptor antagonists in human plasma. The monolithic WCX column was prepared by an in-situ polymerization protocol and modified stepwise with ethylenediamine and chloroacetic acid. On connecting this column to an injection valve, an on-line SPE protocol could be established for removal of matrices (mainly proteins and lipids) and preconcentration of four ,1-adrenergic receptor antagonists in human plasma. This method was validated and then used for determination of terazosin, alfuzosin, prazosin, and doxazosin in clinical plasma samples. For all analytes, each calibration curve was found to be linear over a range of 0.005,5 ,g/mL (R >0.997), and the limit of detection for each analyte was 0.5 ng/mL. Recovery (> 80%) and precision (RSD <15%) for inter- and intra-day assay were tested at three concentration levels of each analyte and showed acceptable results for quantitative assay. Real samples from hypertensive patients were monitored and results were in agreement with those of the conventional liquid,liquid extraction-HPLC method. Furthermore, due to its good permeability and biocompatibility, the monolithic WCX sorbent could be reused more than 300 times. The proposed method was especially appropriate for multi-analyte monitoring in plasma samples. [source] Investigating the presence of pesticide transformation products in water by using liquid chromatography-mass spectrometry with different mass analyzers,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2008Félix Hernández Abstract Many pesticide transformation products (TPs) can reach environmental waters as a consequence of their normally having a higher polarity than their parent pesticides. This makes the development of analytical methodology for reliable identification and subsequent quantification at the sub-microgram per liter levels necessary, as required under current legislation. In this paper we report the photodegradation of several pesticides frequently detected in environmental waters from the Spanish Mediterranean region using the high-resolution and exact-mass capabilities of hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) hyphenated to liquid chromatography (LC). Once the main photodegradation/hydrolysis products formed in aqueous media were identified, analytical methodology for their simultaneous quantification and reliable identification in real water samples was developed using on-line solid-phase extraction (SPE)-LC-tandem MS with a triple-quadrupole (QqQ) analyzer. The methodology was validated in both ground and surface water samples spiked at the limit of quantification (LOQ) and 10 × LOQ levels, i.e. 50 and 500 ng/l, obtaining satisfactory recoveries and precision for all compounds. Subsequent analysis of ground and surface water samples resulted in the detection of a number of TPs higher than parent pesticides. Additionally, several soil-interstitial water samples collected from the unsaturated zone were analyzed to explore the degradation/transformation of some pesticides in the field using experimental plots equipped with lisimeters. Several TPs were found in these samples, with most of them having also been detected in ground and surface water from the same area. This paper illustrates the extraordinary potential of LC-MS(/MS) with QTOF and QqQ analyzers for qualitative/structural and quantitative analysis, respectively, offering analytical chemists one of the most powerful tools available at present to investigate the presence of pesticide TPs in water. Copyright © 2007 John Wiley & Sons, Ltd. [source] Rapid and sensitive on-line liquid chromatographic/tandem mass spectrometric determination of an ethylene oxide-DNA adduct, N7-(2-hydroxyethyl)guanine, in urine of nonsmokersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2008Chih-Chun Jean Huang Ethylene oxide (EtO) is classified as a known human carcinogen. The formation of EtO-DNA adducts is considered as an important early event in the EtO carcinogenic process. An isotope-dilution on-line solid-phase extraction and liquid chromatography coupled with tandem mass spectrometry method was then developed to analyze one of the EtO-DNA adducts, N7-(2-hydroxyethyl)guanine (N7-HEG), in urine of 46 nonsmokers with excellent accuracy, sensitivity and specificity. The merits of this method include small sample volume (only 120,µL urine required), automated sample cleanup, and short total run time (12 minutes per sample). This method demonstrates its high-throughput capacity for future molecular epidemiology studies on the potential health effects resulting from the low-dose EtO exposure. Copyright © 2008 John Wiley & Sons, Ltd. [source] Automated analysis of fluvoxamine in rat plasma using a column-switching system and ion-pair high-performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 12 2008Shicheng Liu Abstract We have established a robust, fully automated analytical method for the analysis of fluvoxamine in rat plasma using a column-switching ion-pair high-performance chromatography system. The plasma sample was injected onto a precolumn packed with Shim-pack MAYI-ODS (50 µm), where the drug was automatically purified and enriched by on-line solid-phase extraction. After elution of the plasma proteins, the analyte was back-flushed from the precolumn and then separated isocratically on a reversed-phase C18 column (L-column ODS) with a mobile phase (acetonitrile,0.1% phosphoric acid, 36:64, v/v) containing 2 mm sodium 1-octanesulfonate. The analyte was monitored by a UV detector at a wavelength of 254 nm. The calibration line for fluvoxamine showed good linearity in the range of 5,5000 ng/mL (r > 0.999) with the limit of quantification of 5 ng/mL (RSD = 6.51%). Accuracy ranged from ,2.94 to 4.82%, and the within- and between-day precision of the assay was better than 8% across the calibration range. The analytical sensitivity and accuracy of this assay is suitable for characterization of the pharmacokinetics of orally-administered fluvoxamine in rats. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||