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Solid-phase Extraction Procedure (solid-phase + extraction_procedure)
Selected AbstractsDetermination of flurbiprofen enantiomers in plasma using a single-isomer amino cyclodextrin derivative in nonaqueous capillary electrophoresis,ELECTROPHORESIS, Issue 17 2008Anne Rousseau Abstract A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-,-cyclodextrin as chiral selector. The nonaqueous background electrolyte was made up of 40,mM ammonium acetate in methanol (MeOH), and flufenamic acid was employed as internal standard. Solid-phase extraction was used for sample cleanup prior to the NACE separation. The NACE method reproducibility was optimized by evaluating different capillary washing sequences between runs. After having tested various conditions, trifluoroacetic acid (1,M) in MeOH was finally selected. Concerning the solid-phase extraction procedure, good and reproducible analyte recoveries were obtained using MeOH for protein denaturation and a polymeric phase combining hydrophobic interactions with anion exchange properties (Oasis® MAX) was selected as extraction sorbent. The method selectivity was not only demonstrated toward a blank plasma sample but also toward other non-steroidal anti-inflammatory drugs. The method was then successfully validated with respect to response function, trueness, precision, accuracy, linearity and limit of quantification. [source] Analysis of lamotrigine and its metabolites in human plasma and urine by micellar electrokinetic capillary chromatographyELECTROPHORESIS, Issue 4-5 2005Vincenzo Pucci Abstract A reliable micellar electrokinetic capillary chromatographic method was developed and validated for the determination of lamotrigine and its metabolites in human plasma and urine. The variation of different parameters, such as pH of the background electrolyte (BGE) and Sodium dodecyl sulfate (SDS) concentration, were evaluated in order to find optimal conditions. Best separation of the analytes was achieved using a BGE composed of 10 mM borate and 50 mM SDS, pH 9.5; melatonin was selected as the internal standard. Isolation of lamotrigine and its metabolites from plasma and urine was accomplished with an original solid-phase extraction procedure using hydrophilic-lypophilic balance cartridges. Good absolute recovery data and satisfactory precision values were obtained. The calibration plots for lamotrigine and its metabolites were linear over the 1,20 ,g/mL concentration range. Sensitivity was satisfactory; the limits of detection and quantitation of lamotrigine were 500 ng/mL and 1 ,g/mL, respectively. The application of the method to real plasma samples from epileptic patients under therapy with lamotrigine gave good results in terms of accuracy and selectivity, and in agreement with those obtained with an high-performance liquid chromatography (HPLC) method.* [source] High-performance liquid chromatography/tandem mass spectrometry for the quantitative analysis of a novel taxane derivative (BAY59-8862) in biological samples and characterisation of its metabolic profile in rat bile samplesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2001Cristina Sottani A sensitive, specific, accurate and reproducible high-performance liquid chromatography (HPLC) analytical method was developed and validated for the quantification of the novel oral taxane analogue BAY59-8862 in mouse plasma and tissue samples. A fully automated solid-phase extraction procedure was applied to the plasma after internal standard (IS) addition, with only 0.2,mL volume of the sample loaded on a CN-Sep-pak cartridge. In the case of the tissues a very simple acetonitrile extraction was used to recover BAY59-8862 and its internal standard from liver. The procedure for the quantification of BAY59-8862 and its IS (IDN5127) is based on high-performance liquid chromatography/ion spray-tandem mass spectrometry, operating in selected ion monitoring mode. The retention times of BAY and IS were 7.21 and 10.36,min, respectively. In both plasma and tissue specimens the assay was linear in the range 50,5000,ng/mL (ng/g). The overall precision and accuracy were assessed on three different days. The results for plasma were within 6.1% (precision) and between 99 and 112% (accuracy), and for the liver samples within 7.3% and between 104 and 118%, respectively. The LOD was 5,ng/mL and 20,ng/g in the plasma and liver, respectively. In addition, the biliary excretion of the compound in rats was studied. The study showed that an oxidative chemical reaction was the preferred metabolic pathway for biliary excretion, and two sets of mono- and dihydroxylated metabolites were detected by LC/ISP-MS/MS experiments. With this method, BAY59-8862 pharmacokinetic was determined in mice. The combined results demonstrate that the methodology can be considered a valid approach to conduct pharmacokinetic and metabolic studies during preclinical and clinical investigations. Copyright © 2001 John7 Wiley & Sons, Ltd. [source] Development of a method to measure methadone enantiomers and its metabolites without enantiomer standard compounds for the plasma of methadone maintenance patientsBIOMEDICAL CHROMATOGRAPHY, Issue 7 2010Sheng-Chang Wang Abstract A liquid chromatography,photodiode array (LC-PDA) method using a chiral analytical column was developed to determine the plasma levels of enantiomers of methadone and its chiral metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), without the standard compounds of R -form or S -form enantiomers. This method was established by the characteristics of recombinant cytochrome P-450 (CYP) isozymes, where CYP2C19 prefers to metabolize R -methadone and CYP2B6 prefers to metabolize S -methadone. We incubated the racemic methadone standard with either enzyme for 24,h. We identified the retention times of R - and S -methadone to be around 10.72 and 14.46,min, respectively. Furthermore, we determined the retention times of R - and S -EDDP to be approximately 6.76 and 7.72,min, respectively. No interferences were shown through the retention times of morphine, buprenorphine and diazepam. With the high recovery rate of a solid-phase extraction procedure, this method was applied in analyzing plasma concentrations of seven methadone maintenance patients where R - and S -methadone and R - and S -EDDP were 233.4 ± 154.9 and 185.9 ± 136.3,ng/mL and 84.4 ± 99.4 and 37.6 ± 22.9,ng/mL, respectively. These data suggest that the present method can be applied for routine assay for plasma methadone and EDDP concentrations for patients under treatment. Copyright © 2009 John Wiley & Sons, Ltd. [source] Quantitation of oxcarbazepine and its metabolites in human plasma by micellar electrokinetic chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 4 2003Vincenzo Pucci Abstract A reliable micellar electrokinetic chromatographic method for the determination of oxcarbazepine and its two main metabolites, 10-hydroxycarbamazepine and 10,11- trans -dihydroxy-10,11-dihydroxycarbamazepine, in human plasma was developed. The separation and determination of the analytes was achieved using a system consisting of 60,mM SDS in phosphate buffer (30,mM, pH 8.0), to which 20% (v/v) methanol was added. Separation was carried out in an uncoated fused-silica capillary with a separation voltage of 25,kV and currents typically less than 40,µA. Spectrophotometric detection was at 205,nm. Isolation of oxcarbazepine and its metabolites from plasma was accomplished by a solid-phase extraction procedure. The mean extraction yield of the analytes from plasma was higher than 94%. The linear correlation coefficients were better than 0.994 for all analytes. The limit of detection was 0.05,µg/mL, the limit of quantitation 0.15,µg/mL. The repeatability for the spiked blank plasma samples was lower than 1.9% and the intermediate precision lower than 2.1%, both expressed as RSD%. The results obtained analysing real plasma samples from epileptic patients under therapy with Tolep® were satisfactory in terms of precision, accuracy and detectability. Copyright© 2003 John Wiley & Sons, Ltd. [source] Competitive MS Binding Assays for Dopamine D2 Receptors Employing Spiperone as a Native MarkerCHEMBIOCHEM, Issue 10 2005Karin V. Niessen Abstract A competitive MS binding assay employing spiperone as a native marker and a porcine striatal membrane fraction as a source for dopamine D2 receptors in a nonvolatile buffer has been established. Binding of the test compounds to the target was monitored by mass-spectrometric quantification of the nonbound marker, spiperone, in the supernatant of the binding samples obtained by centrifugation. A solid-phase extraction procedure was used for separating spiperone from ESI-MS-incompatible supernatant matrix components. Subsequently, the marker was reliably quantified by LC-ESI-MS-MS by using haloperidol as an internal standard. The affinities of the test compounds, the dopamine receptor antagonists (+)-butaclamol, chlorpromazine and (S)-sulpiride obtained from the competitive MS binding assay were verified by corresponding radioligand binding experiments with [3H]spiperone. The results of this study demonstrate that competitive MS binding assays represent a universally applicable alternative to conventional radioligand binding assays. [source] | ||||||||||