Search results for "liquid chromatography"

Characterization of DNA adducts at the bay region of dibenz[a,h]anthracene formed in vitro

1993

Bay region diolepoxide-DNA adducts of dibenz[a,h]anthracene (DBA) formed in vitro were identified and their absolute stereochemistry was assigned. After activation of [5,12-14C]DBA with liver microsomes obtained from Aroclor 1254 treated male Sprague-Dawley rats in the presence of calf thymus DNA for 1 h, the amount of DNA adducts was found to be 9.9 +/- 2.4 pmol/mg DNA, calculated on the basis of the portion of radioactivity eluted from the HPLC reversed-phase column with a water/acetonitrile gradient. Bay region diolepoxide-DNA adducts represented 27.5% of radioactivity associated with DNA adducts. The absolute configuration of the various adducts was determined from the reaction of the (…

High-performance liquid chromatography with fluorimetric detection in biological tissues of the 4-bromomethyl-7-methoxycoumarin ester derivative of 5…

1985

Measurement of Duloxetine in Blood Using High-performance Liquid Chromatography with Spectrophotometric Detection and Column Switching

2007

A method using high-performance liquid chromatography (HPLC) with column switching and ultraviolet (UV) spectroscopy was developed for the determination of duloxetine in human plasma. After centrifugation and addition of venlafaxine as internal standard, plasma samples were injected into the HPLC system and precleaned on a column (10 x 4.0 mm) filled with cyanopropyl (CN)-modified silica of 20 microm particle size, with use of 8% (vol/vol) acetonitrile in deionized water as eluent. Duloxetine was eluted and separated on a LiChrospher 100 CN (5-microm particle size; column size, 250 x 4.6 mm I.D.) using acetonitrile-water-potassium dihydrogenphosphate trihydrate buffer (pH, 6.4; 50:50 vol/vo…

The use of high-pressure liquid cation-exchange chromatography for determination of the 5-methylcytosine content of DNA.

1976

Metabolism of 3-hydroxychrysene by rat liver microsomal preparations

1990

3-Hydroxychrysene, a metabolite of the polycyclic aromatic hydrocarbon (PAH) chrysene, was metabolised by rat liver microsomal preparations obtained from Arochlor 1254-pretreated rats. Eight major metabolites were isolated by high performance liquid chromatography and characterised by u.v. spectroscopy and a variety of mass spectrometric techniques. The metabolites were unambiguously identified as 9-hydroxy-trans-1,2-dihydroxy-1,2-dihydrochrysene and 9-hydroxy-r-1,t-2,t-3,c-4-tetrahydroxy-1,2,3,4-tetrahydrochrysene and tentatively identified as 3-hydroxy-trans-5,6-dihydroxy-5,6-dihydrochrysene (since chrysene is a symmetrical molecule the 3- and 9-positions are equivalent), 9-hydroxy-trans-…

Determination of globotriaosylceramide in plasma and urine by mass spectrometry

2009

Abstract Background: Fabry disease is an X-chromosomally inherited lysosomal storage disorder leading to accumulation of glycosphingolipids, mainly globotriaosylceramide (ceramide-trihexoside, Gb3). Concentrations of Gb3 in plasma and urine have been used to diagnose Fabry disease and to monitor enzyme replacement therapy with recombinant α-galactosidase. Methods: Gb3 was purified from plasma or urine by combined liquid extraction/protein precipitation and solid-phase extraction, and was detected by flow-injection analysis electrospray mass spectrometry (MS) using multi-reaction-monitoring. Calibration was performed via standard addition using C17-Gb3 as internal standard. The most abundant…

Automated determination of clomipramine and its major metabolites in human and rat serum by high-performance liquid chromatography with on-line colum…

1998

A fully automated method including column-switching and isocratic high-performance liquid chromatography (HPLC) was developed for simultaneous determination of the tricyclic antidepressant clomipramine and its metabolites demethylclomipramine, 2-, 8-, and 10-hydroxyclomipramine, 2-, and 8-hydroxydemethylclomipramine and didemethylclomipramine in serum. After serum injection into the HPLC system and on-line sample clean-up on a clean-up column (Hypersil CN; 10 x 4.6 mm) by an eluent consisting of 35% acetonitrile and 65% deionized water, the chromatographic separation was performed on an analytical column (LiChrospher CN; 250 x 4.6 mm I.D.) by an eluent consisting of 38% acetonitrile and 62%…

Determination of microcystins in biological samples by matrix solid-phase dispersion and liquid chromatography–mass spectrometry

2005

A method for the detection and quantification of the microcystins (MCs)-MC-LR, MC-RR and MC-YR-in biological samples by matrix solid-phase dispersion (MSPD) has been developed. The optimum extraction conditions were 500 mg of liver or kidney, C18 bonded silica as dispersant, and a mixture methanol-water (70:30) as eluent. The MCs were determined by liquid chromatography electrospray mass spectrometry (LC/ES/MS). Recoveries of biological extracts at three different spiked levels (1-10 mg kg(-1)) ranged from 40.5 to 87.0% in liver, and from 52.5 to 74.5 in kidney. R.S.D.s were < 15.6% and < 10.6%, respectively. The detection and quantification limits were 0.05 and 0.5 mg kg(-1), for all MCs. …

Endogenous role of epoxide-hydratase. Development of a steroid epoxide-hydratase assay and properties of the enzyme.

1979

A highly sensitive and rapid radiometric assay for the determination of specific epoxide hydratase activity with a steroid epoxide (16α, 17α-epoxy-1,3,5(10)-estratrien-3-ol, ‘estroxide’) has been developed. The unreacted substrate was separated from the product 1,3,5(10)-estratrien-3,16β,17α-triol by extraction into light petroleum. The product was then extracted into ethyl acetate and measured by scintillation spectrometry. Radiochromatography established that after subtraction of the blank the entire radioactivity measured in the ethyl acetate phase resulted from the product 1,3,5(10)-estratrien-3,16,17-triol, whilst high performance liquid chromatography with the four possible isomers of…

Determination of benzophenone-3 and its main metabolites in human serum by dispersive liquid–liquid microextraction followed by liquid chromatography…

2013

A new analytical method for the determination of benzophenone-3 (2-hydroxy-4-methoxybenzophenone), and its main metabolites (2,4-dihydroxybenzophenone and 2,2'-dihydroxy-4-methoxybenzophenone) in human serum is presented. The method is based on dispersive liquid-liquid microextraction (DLLME) as preconcentration and clean-up technique, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Acidic hydrolysis and protein precipitation with HCl 6 M (1:1) (100 °C, 1 h) were carried out before extraction. The variables involved in the DLLME process were studied. Under the optimized conditions, 70 µL of acetone (disperser solvent) and 30 µL of chloroform (extraction solvent) were …