Home About us Contact
|
Home About us Contact | ||
|
|
||
M Ammonium Acetate (m + ammonium_acetate)
Selected AbstractsQuantitative analysis of EO9 (apaziquone) and its metabolite EO5a in human plasma by high-performance liquid chromatography under basic conditions coupled to electrospray tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2006Liia D. Vainchtein A sensitive and specific LC-MS/MS assay for the quantitative determination of EO9 and its metabolite EO5a is presented. A 200-µl human plasma aliquot was spiked with a mixture of deuterated internal standards EO9- d3 and EO5a- d4 and extracted with 1.25 ml ethyl acetate. Dried extracts were reconstituted in 0.1 M ammonium acetate,methanol (7 : 3, v/v) and 25 µl-volumes were injected into the HPLC system. Separation was achieved on a 150 × 2.1 mm C18 column using an alkaline eluent (1 mM ammonium hydroxide,methanol (gradient system)). Detection was performed by positive ion electrospray followed by tandem mass spectrometry. The assay quantifies a range from 5 to 2500 ng/ml for EO9 and from 10 to 2500 ng/ml EO5a using 200 µl of human plasma samples. Validation results demonstrate that EO9 and EO5a concentrations can be accurately and precisely quantified in human plasma. This assay will be used to support clinical pharmacologic studies with EO9. Copyright © 2006 John Wiley & Sons, Ltd. [source] Positive ion electrospray ionization mass spectrometry of double-stranded DNA/drug complexesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2001Rajesh Gupta An Erratum has been published for this article in Rapid Communicatons in Mass Spectrometry 16(7) 2002,740,741. Positive ion electrospray ionization mass spectra of 16 base-pair double-stranded (ds)DNA have been obtained with essentially no ions from single-stranded DNA present. Single-stranded DNA was minimized by: (1) careful choice of DNA sequences; (2) the use of a relatively high salt concentration (0.1,M ammonium acetate, pH 8.5), and, (3) a low desolvation temperature (40,°C). Similarly, ESI-MS complexes of dsDNA with cisplatin, daunomycin and distamycin were obtained that contained only negligible amounts of single-stranded DNA. The complexes with daunomycin and distamycin were more stable to strand separation in the gas phase than dsDNA alone. This is in agreement with solution studies and with other recent gas phase results. These data contrast with many earlier ESI-MS studies of dsDNA and DNA/drug complexes in which ions from ssDNA are also normally observed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Crystallization and preliminary X-ray analysis of bucain, a novel toxin from the Malayan krait Bungarus candidusACTA CRYSTALLOGRAPHICA SECTION D, Issue 10-2 2002L. Watanabe Bucain is a three-finger toxin, structurally homologous to snake-venom muscarinic toxins, from the venom of the Malayan krait Bungarus candidus. These proteins have molecular masses of approximately 6000,8000,Da and encompass the potent curaremimetic neurotoxins which confer lethality to Elapidae and Hydrophidae venoms. Bucain was crystallized in two crystal forms by the hanging-drop vapour-diffusion technique in 0.1,M sodium citrate pH 5.6, 15% PEG 4000 and 0.15,M ammonium acetate. Form I crystals belong to the monoclinic system space group C2, with unit-cell parameters a = 93.73, b = 49.02, c = 74.09,Å, , = 111.32°, and diffract to a nominal resolution of 1.61,Å. Form II crystals also belong to the space group C2, with unit-cell parameters a = 165.04, b = 49.44, c = 127.60,Å, , = 125.55°, and diffract to a nominal resolution of 2.78,Å. The self-rotation function indicates the presence of four and eight molecules in the crystallographic asymmetric unit of the form I and form II crystals, respectively. Attempts to solve these structures by molecular-replacement methods have not been successful and a heavy-atom derivative search has been initiated. [source] Highly sensitive method for the determination of omeprazole in human plasma by liquid chromatography,electrospray ionization tandem mass spectrometry: application to a clinical pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 4 2009Shivva Vittal Abstract A highly sensitive, rapid assay method has been developed and validated for the estimation of omeprazole (OPZ) in human plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive-ion mode. The assay procedure involves alkalinization of plasma followed by simple liquid,liquid extraction of OPZ and lansoprazole (internal standard, IS) from human plasma with acetonitrile. Chromatographic separation was achieved with 0.01 m ammonium acetate:acetonitrile (40:60, v/v) at a flow rate of 0.25 mL/min on an Inertsil ODS 3 column with a total run time 2.5 min. The MS/MS ion transitions monitored were 346.1 , 198.1 for OPZ and 370.1 , 252.1 for IS. Method validation and clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.05 ng/mL and the linearity was observed from 0.05 to 10.0 ng/mL. The intra-day and inter-day precisions were in the ranges 2.09,8.56 and 5.29,8.19%, respectively. This novel method has been applied to a pharmacokinetic study of OPZ in humans. Copyright © 2008 John Wiley & Sons, Ltd. [source] The determination of raloxifene in rat tissue using HPLCBIOMEDICAL CHROMATOGRAPHY, Issue 3 2007Zhaoyong Yang Abstract We report a rapid and reliable HPLC-UV method for determination of raloxifene, a kind of selective estrogen receptor modulator (SERM), in rat tissue. Proteins were precipitated by adding 200 µL of acetonitrile and 50 µL of methanol to 100 µL of the tissue homogenates, following vortex mixing and centrifugation. Separation was carried out on a reversed-phase C18 column (150 × 4.6 mm, 5 µm) with a mobile phase of acetonitrile:0.05 m ammonium acetate (pH 4.0 ± 0.1; 33:67, v/v) at a flow rate of 1.0 mL/min. The UV detection wavelength was set at 289 nm and the temperature of column was kept at 23°C, without interference from endogenous tissue compounds. The calibration curve was linear from 0.0125 to 10.0 µg/mL with correlation coefficient of over 0.994, while the limit of quantification was 0.008 µg/mL. The intra- and inter-day coefficients of variation were less than 10% (RSD). The recovery of assay was between 95.8 and 104.5%. Furthermore, the method was used to measure the concentration of raloxifene in rat tissue after a simple oral dose. The highest level was observed in liver, lung, spleen, then heart and kidney. The lowest level was found in brain. These results suggest that raloxifene distributes rapidly and moderately into tissues such as liver, lung and spleen. Copyright © 2007 John Wiley & Sons, Ltd. [source] High-throughput determination of atrasentan in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 9 2005Perry G. Wang Abstract Atrasentan (A-147627) is an endothelin antagonist receptor being developed at Abbott Laboratories for the treatment of prostate cancer. A quick and sensitive method for the determination of atrasentan in human plasma has been developed and validated using high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. A dual-column, single mass spectrometer system is used to provide a reliable and routine means to increase sample throughput. The analytical method involves liquid,liquid extraction and internal standard (A-166790). The plasma samples and internal standard are acidified with 0.3 m hydrochloric acid prior to being extracted into 1:1 (v[sol ]v) hexanes,methyl t -butyl ether. The organic extract was evaporated to dryness using heated nitrogen stream and reconstituted with mobile phase. Atrasentan and internal standard were separated with no interference in a Zorbax SB-C18 analytical column with 2.1 × 50 mm, 5 µm, and a Zorbax C8 guard column using a mobile phase consisting of 50:50 (v:v) acetonitrile,0.05 m ammonium acetate, pH 4.5, at a flow rate of 0.30 mL[sol ]min to provide 4 min chromatograms. For a 250 µL plasma sample volume, the limit of quantitation was approximately 0.3 ng[sol ]mL. The calibration was linear from 0.30 to 98.0 ng[sol ]mL (r2 > 0.995). A significant advantage of the method is the ability to employ parallel HPLC separations with detection by a single MS[sol ]MS system to provide sensitivity and selectivity sufficient to achieve robust analytical results with a lower limit of quantitation of 0.30 ng[sol ]mL and high throughput. Copyright © 2005 John Wiley & Sons, Ltd. [source] Determination of the ,avone tricin in human plasma by high-performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 7 2003Hong Cai Abstract Tricin is a ,avone constituent of brown rice and rice bran, which interferes potently with the survival of human-derived breast and colon cancer cells in vitro. A speci,c and simple high-performance liquid chromatographic (HPLC) method was developed for the determination of tricin in human plasma with UV,visible detection. HPLC separation on Hypersil-BDS C18 (4.6 × 250 mm) was carried out with an isocratic mobile phase of 52% methanol in 0.1 m ammonium acetate, pH 5.10, containing 0.27 mm disodium ethylenediamine tetraacetic acid and detection at 355 nm. The retention times of tricin and quercetin (internal standard) were 14.2 and 7.8 min, respectively. The assay was linear in the range 1,100 µg/mL (r2 , 0.995). Tricin in plasma was ef,ciently extracted with 0.1 m acetic acid in acetone, and the recoveries were in the range 92.6,102.8% (n = 6) with relative standard deviation below 10% for three concentrations of tricin, 5, 10 and 100 µg/mL. The lower limit of quantitation (relative standard deviation <20%) was 1 µg/mL. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||