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Column-switching System (column-switching + system)
Selected AbstractsDetermination of iodide in samples with complex matrices by hyphenation of capillary isotachophoresis and zone electrophoresisELECTROPHORESIS, Issue 20 2007Pavla Pant Abstract A method has been developed for the determination of iodide in mineral water, seawater, cooking salt, serum, and urine based on hyphenation of capillary ITP and zone electrophoresis. A commercially available instrumentation for capillary ITP with column-switching system was used. ITP served for removal of chloride present in the analyzed samples in a ratio of 106,107:1 to iodide, zone electrophoresis was used for evaluation. Isotachophoretic separation proceeded in a capillary made of fluorinated ethylene,propylene copolymer of 0.8,mm id and 90,mm total length to the bifurcation point filled with a leading electrolyte (LE) composed of 8,mM HCl,+,16,mM ,-alanine (,-Ala),+,10% PVP,+,2.86,mM N2H4×2HCl, pH,3.2; and a terminating electrolyte composed of 8,mM H3PO4,+,16,mM ,-Ala,+,10% PVP,+,5,mM N2H4, pH,3.85 for all the matrices except seawater. For ITP of seawater the LE consisted of 50,mM HCl,+,100,mM ,-Ala,+,10% PVP +,2.86,mM N2H4×2HCl, pH,3.52. Distance of conductivity detector from the injection point and bifurcation point was 52 and 38,mm, respectively. Zone electrophoresis was performed in a capillary made of fused silica of 0.3,mm id and 160,mm total length filled with LE from isotachophoretic step. LODs reached for all matrices were 2,3×10,8,M concentration (2.5,4,,g/L) enabled monitoring of iodide in all analyzed samples with RSD 0.4,9.3%. Estimated concentrations of iodide in individual matrices were 10,6,10,8,M. [source] Simple and simultaneous determination of sulphapyridine and acetylsulphapyridine in human serum by column-switching high-performance liquid chromatographyJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 6 2002D. Teshima PhD Summary Objective:, A high-performance liquid chromatography (HPLC) with an automated on-line column-switching system was used for the simultaneous determination of sulphapyridine and acetylsulphapyridine, two major active metabolites related to the adverse effects of sulphasalazine, in human serum. Methods:, Serum samples were directly injected into the HPLC, with the valve automatically switched on to remove serum proteins and other hydrophilic components remaining in the pre-column after elution of sulphapyridine and acetylsulphapyridine to the analytical column. Results:, Serum proteins did not interfere with the analysis of either compound. The recoveries of SLP and Ac-SLP from drug-free human serum were 93·03,99·18% and CV were 2·88,4·34%. The within-run reproducibility of assays was excellent with relative standard deviations (RSD) of 1·01,3·90% (SLP) and 0·77,5·56% (Ac-SLP). The limit of quantification of sulphapyridine and acetylsulphapyridine was 3·13 ,g/mL and 0·50 ,g/mL, respectively. The serum concentrations in a patient with ulcerative colitis, who took 1·0 g sulphasalazine twice daily, were 31·20 ,g/mL for sulphapyridine and 14·64 ,g/mL for acetylsulphapyridine at 7 h after ingestion. Conclusion:, The present simple and reproducible assay was useful for the monitoring of serum sulphapyridine and acetylsulphapyridine. [source] A strategy for quantitative bioanalysis of non-polar neutral compounds by liquid chromatography/electrospray ionization tandem mass spectrometry: determination of TS-962, a novel acyl-CoA:cholesterol acyltransferase inhibitor, in rabbit aorta and liver tissuesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2001Jun-ichi Yamaguchi A strategy for the sensitive and reliable quantitative determination of non-polar neutral compounds in biological matrices by liquid chromatography/electrospray ionization tandem mass spectrometry is described in the context of assay development for TS-962, a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, in rabbit aorta and liver tissues. The electrospray ionization (ESI) mass spectrum of this compound with a mobile phase of water/acetonitrile did not give abundant [M,+,H]+ ions, but did give alkali metal cation adducts such as [M,+,Na]+, [M,+,CH3CN,+,Na]+ and [M,+,K]+ ions. The cationized species are acknowledged as unsuitable precursor ions for selected reaction monitoring (SRM) for various reasons, such as difficulty in obtaining characteristic product ions in low-energy collision-induced dissociation, and irreproducibility of the adduct-ion intensities. To overcome this problem, a solution of 3.4,mM trifluoroacetic acid in 2-propanol was added to the mobile phase as a postcolumn additive, resulting in a decrease of the undesirable adduct formation and significant enhancement of [M,+,H]+ ion intensity. An attempt was then made to prevent the matrix effect by employing a column-switching system, which allowed direct injection of a large volume of 2-propanolic tissue homogenate (950,µL) followed by sufficient clean-up, separation, and ESI-SRM on-line. This enabled development of a sensitive and reliable assay method for TS-962 in rabbit aorta and liver tissues in the concentration range of 5,500,ng/g wet tissue using a 25-mg aliquot of tissue sample. Application of this method to the determination of aortic TS-962 levels at 24,h after repeated oral administration of this compound (3,mg/kg) once a day for 12 weeks to 1% cholesterol-fed rabbits is also presented. Results showed that TS-962 is well distributed to both the thoracic and abdominal aorta tissues, at levels higher than the 50% inhibitory concentration value of this compound for microsomal ACAT activity from rabbit aorta. Copyright © 2001 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] Determination of bisphenol A in human breast milk by HPLC with column-switching and ,uorescence detectionBIOMEDICAL CHROMATOGRAPHY, Issue 8 2004Yen Sun Abstract A highly sensitive HPLC method was developed for the determination of xenoestrogenic compound, bisphenol A (BPA) in human breast milk samples. After a two-step liquid,liquid extraction, BPA was derivatized with ,uorescent labeling reagent, 4-(4,5-diphenyl-1H -imidazol-2-yl)benzoyl chloride (DIB-Cl). The excess ,uorescent reagent could be removed effectively using a column-switching system. The separation of DIB-BPA from endogenous materials in milk was carried out on two C18 columns and ,uorescence intensity was monitored at 475 nm with the excitation of 350 nm. A good linearity (r = 0.994) was observed of BPA in the concentration range of 0.2,5.0 ng mL,1 in breast milk, and the detection limit was 0.11 ng mL,1 at a signal-to-noise ratio of 3. Intra- and inter-day precision (RSD, %) were less than 8.7 and 10.4, respectively. Twenty-three breast milk samples of healthy lactating women were analyzed for the BPA concentration; the mean value was 0.61 ± 0.20 ng mL,1, with no correlation to the lipid content of milk samples. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||