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Isocratic Elution (isocratic + elution)
Selected AbstractsSimultaneous RP-HPLC-DAD quantification of bromocriptine, haloperidol and its diazepane structural analog in rat plasma with droperidol as internal standard for application to drug-interaction pharmacokineticsBIOMEDICAL CHROMATOGRAPHY, Issue 7 2010Johnique Billups Abstract A simple and rapid RP-HPLC-DAD method was developed and validated for simultaneous determination of the dopamine antagonists haloperidol, its diazepane analog, and the dopamine agonist bromocriptine in rat plasma, to perform pharmacokinetic drug-interaction studies. Samples were prepared for analysis by acetonitrile (22.0,,g/mL) plasma protein precipitation with droperidol as an internal standard, followed by a double-step liquid-liquid extraction with hexane,:,chloroform (70:30) prior to C-18 separation. Isocratic elution was achieved using a 0.1% (v/v) trifluoroacetic acid in deionized water, methanol and acetonitrile (45/27.5/27.5, v/v/v). Triple-wavelength diode-array detection at the ,max of 245,nm for haloperidol, 254,nm for the diazepane analog and droperidol, and 240,nm for bromocriptine was carried out. The LLOQ of DAL, HAL, and BCT were 45.0, 56.1, and 150,ng/mL, respectively. In rats, the estimated pharmacokinetic parameters (i.e., t1/2, CL, and Vss) of HAL when administered with DAL and BCT were t1/2 = 16.4,min, Vss = 0.541,L/kg for HAL, t1/2 = 28.0,min, Vss = 2.00,L/kg for DAL, and t1/2 = 24.0,min, Vss = 0.106,L/kg for BCT. The PK parameters for HAL differed significantly from those previously reported, which may be an indication of a drug-drug interaction. Copyright © 2009 John Wiley & Sons, Ltd. [source] Simultaneous determination of maraviroc and raltegravir in human plasma by HPLC-UVIUBMB LIFE, Issue 4 2009Stefania Notari Abstract Therapeutic drug monitoring is pivotal to improve the management of HIV infection. Here, a new HPLC,UV method to quantify simultaneously maraviroc and raltegravir levels in human plasma is reported. Remarkably, this is the first method for maraviroc determination in human plasma. The volume of the plasma sample was 600 ,L. This method involved automated solid-phase extraction with Oasis HLB Cartridge 1 cc (30 mg divinylbenzene and N -vinylpyrrolidone) and evaporation in a water bath under nitrogen stream. The extracted samples were reconstituted with 200 ,L 50/50 of mobile-phase solution (0.01 M KH2PO4 and acetonitrile). Twenty microliters of these samples were injected into a HPLC,UV system, the analytes were eluted on an analytical dC18 Atlantis column (150 mm × 4.6 mm I.D.) with a particle size of 5 ,m. The mobile phase (0.01 M KH2PO4 and acetonitrile) was delivered at 1.0 mL/min with isocratic elution. The total run time for a single analysis was 10 min; maraviroc and raltegravir were detected by UV at 197 and 300 nm. The calibration curves were linear up to 2,500 ng/mL. The absolute recovery ranged between 93 and 100%. The HPLC,UV method reported here has been validated and is currently applied to monitor plasma levels of maraviroc and raltegravir in HIV-infected patients. © 2009 IUBMB IUBMB Life, 61(4):470,475, 2009 [source] Phenolic Acid Content and Composition in Leaves and Roots of Common Commercial Sweetpotato (Ipomea batatas L.) Cultivars in the United StatesJOURNAL OF FOOD SCIENCE, Issue 6 2007V.-D. Truong ABSTRACT:, Phenolic acids in commercially important sweet potato cultivars grown in the United States were analyzed using reversed-phase high-performance liquid chromatography (HPLC). Caffeic acid, chlorogenic acid, 4,5-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, and 3,4-di-O-caffeoylquinic acid were well separated with an isocratic elution in less than 25 min compared to about 120 min for analyzing and re-equilibrating the column with a gradient method. The isocratic elution order of these caffeoylquinic acid derivatives was confirmed by LC-MS/MS. Chlorogenic acid was the highest in root tissues, while 3,5-di-O-caffeoylquinic acid and/or 4,5-di-O-caffeoylquinic acid were predominant in the leaves. Steam cooking resulted in statistically nonsignificant increases in the concentration of total phenolics and all the individual phenolic acids identified. Sweetpotato leaves had the highest phenolic acid content followed by the peel, whole root, and flesh tissues. However, there was no significant difference in the total phenolic content and antioxidant activity between purees made from the whole and peeled sweet potatoes. [source] Preparation and a simple one-step purification of [His1 -mono- 125I-Tyr10,Nle27]-hGHRH(1-32)-NH2JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2002Janos Gardi Abstract A one-step purification of [His1 -mono- 125I-Tyr10,Nle27]-hGHRH(1-32)-NH2, prepared using chloramine-T, by HPLC with isocratic elution is described. The labeled GHRH analog was suitable for GHRH receptor binding assays. Copyright © 2002 John Wiley & Sons, Ltd. [source] A rapid and sensitive liquid chromatography/positive ion tandem mass spectrometry method for the determination of cimetropium in human plasma by liquid,liquid extractionJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2006Heon-Woo Lee Abstract We have developed and validated a simple detection system with high-performance liquid chromatography (HPLC) with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) for determining cimetropium levels in human plasma using scopolamine butyl bromide as an internal standard (I.S.). The acquisition was performed in the multiple reaction monitoring (MRM) mode, by monitoring the transitions: m/z 357.9 > 103.1 for cimetropium and m/z 359.9 > 103.1 for butyl-scopolamine. The method involves a simple single-step liquid,liquid extraction with dichloromethane. The analyte was chromatographed on an YMC C18 reversed-phase chromatographic column by isocratic elution with 10 mM ammonium formate buffer,methanol (19 : 81, v/v; adjusted to pH 4.0 with formic acid). The results were linear over the studied range (0.2,100 ng ml,1), with r2 = 1.0000, and the total analysis time for each run was 2 min. Intra- and interassay precisions were 0.70,8.54% and 1.08,4.85%, respectively, and intra- and interassay accuracies were 97.56,108.23% and 97.48,103.91%, respectively. The lower limit of quantification (LLOQ) was 0.2 ng ml,1. At this concentration, mean intra- and interassay precisions were 8.54% and 4.85%, respectively, and mean intra- and interassay accuracies were 97.56% and 98.91%, respectively. The mean recovery ranged from 62.71 ± 4.06 to 64.23 ± 2.32%. Cimetropium was found to be stable in plasma samples under typical storage and processing conditions. The devised assay was successfully applied to a pharmacokinetic study of cimetropium bromide administered as a single oral dose (150 mg) to healthy volunteers. Copyright © 2006 John Wiley & Sons, Ltd. [source] Quantification of fudosteine in human plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry employing precolumn derivatization with 9-fluorenylmethyl chloroformateJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2006Fengguo Xu Abstract This paper describes a novel method for the sensitive and selective determination of fudosteine in human plasma. The method involves a derivatization step with 9-fluorenylmethyl chloroformate (FMOC-Cl) in borate buffer and detection based on high-performance liquid chromatography-electrospray ionization mass spectrometry (LC/ESI/MS). After acetonitrile-induced protein precipitation of plasma samples, fudosteine was derivatized with FMOC-Cl, then extracted by ethyl acetate, evaporated, reconstituted and injected using an LC/ESI/MS instrument. Separation was achieved using an ODS column and isocratic elution. Excellent linearity was obtained for the entire calibration range from 0.05 to 20 µg/ml. Validation assays of the lower limit of quantification (LLOQ) as well as for the intra- and inter-batch precision and accuracy met the international acceptance criteria for bioanalytical method validation. Using the developed analytical method, fudosteine could be detected for the first time in human plasma with a low limit of detection (LLOD) of 0.03 µg/ml. The proposed method has been successfully applied to study the pharmacokinetics of fudosteine in healthy Chinese volunteers after single and multiple oral administration. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method for the quantification of lacidipine in human plasmaJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2004N. V. S. Ramakrishna Abstract A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantification of lacidipine in human plasma using its structural analogue, amlodipine, as internal standard (IS). The method involves a simple single-step liquid,liquid extraction with tert -butyl methyl ether. The analyte was chromatographed on an Xterra MS C18 reversed-phase chromatographic column by isocratic elution with 20 mM ammonium acetate buffer,acetonitrile (10 : 90, v/v; pH 6) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 456.4 , 354.4 and m/z 409.3 , 238.3 were used to measure the analyte and the I.S., respectively. The chromatographic run time was 1.5 min and the weighted (1/x2) calibration curves were linear over the range 0.1,25 ng ml,1. Lacidipine was sensitive to temperature in addition to light. The method was validated in terms of accuracy, precision, absolute recovery, freeze,thaw stability, bench-top stability and re-injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 50 and 100 pg ml,1, respectively. The within- and between-batch accuracy and precision were found to be well within acceptable limits (<15%). The analyte was stable after three freeze,thaw cycles (deviation <15%). The average absolute recoveries of lacidipine and amlodipine (IS) from spiked plasma samples were 51.1 ± 1.3 and 50.3 ± 4.9%, respectively. The assay method described here could be applied to study the pharmacokinetics of lacidipine. Copyright © 2004 John Wiley & Sons, Ltd. [source] Micellar and aqueous-organic liquid chromatography using sub-2,,m packings for fast separation of natural phenolic compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2010Jun Cao Abstract The objective of the present work was to investigate the chromatographic behavior of natural phenolic compounds in micellar and aqueous-organic LC using a short column packed with 1.8,,m particles. Firstly, the effect of ACN and SDS on elution strength and selectivity was examined by isocratic submicellar (0,30% ACN/5% 1-butanol/1,6,mM SDS) and micellar (0,30% ACN/5% 1-butanol/40,60,mM SDS) systems. The varied concentrations of two modifiers in the mobile phases revealed different eluting power. Then, the application of organic modifier gradient was discussed in both submicellar and micellar LC using mobile phases of 4,mM SDS/5% 1-butanol or 50,mM SDS/5% 1-butanol containing ACN gradient from 0 to 30%, respectively. For micellar system, the separation was found to be better in gradient than isocratic elution. Additionally, the sensitivity of aqueous-organic LC was examined. The mobile phase was a mixture of ACN and water employing gradient elution at a flow rate of 0.5,mL/min, with analysis time below 9,min. It was found that separation efficiency was significantly better compared with micellar LC. Besides, the aqueous-organic LC has been applied to separation of various phenolic compounds in Yangwei granule or Radix Astragali samples. [source] Silica-based monolithic column with evaporative light scattering detector for HPLC analysis of bacosides and apigenin in Bacopa monnieriJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009Pamita Bhandari Abstract A high performance liquid chromatographic method using a silica-based monolithic column coupled with evaporative light scattering detector (HPLC,ELSD) was developed and validated for simultaneous quantification of bacosides (bacoside A, bacopaside I, bacoside A3, bacopaside II, bacopaside X, bacopasaponin C) and apigenin in Bacopa monnieri. The chromatographic resolution was achieved on a Chromolith RP-18 (100×4.6 mm) column with acetonitrile/water (30:70) as mobile phase in isocratic elution at a flow rate of 0.7 mL/min. The drift tube temperature of the ELSD was set to 95°C, and the nitrogen flow rate was 2.0 SLM (standard liter per minute). The calibration curves revealed a good linear relationship (r2 >0.9988) within the test ranges. The detection limits (S/N = 3) and the quantification limits (S/N = 10) for the compounds were in the range of 0.54,6.06 and 1.61,18.78 ,g/mL, respectively. Satisfactory average recovery was observed in the range of 95.8,99.0%. The method showed good reproducibility for the quantification of these compounds in B. monnieri with intra- and inter-day precision of less than 0.69 and 0.67%, respectively. The validated method was successfully applied to quantify analytes in nine accessions of B. monnieri and thus provides a new basis for overall quality assessment of B. monnieri. [source] A review of the background, operating parameters and applications of microemulsion liquid chromatography (MELC)JOURNAL OF SEPARATION SCIENCE, JSS, Issue 15 2005A. Marsh Abstract Microemulsions are dispersions of nanometre-sized droplets of an immiscible liquid within another liquid. Droplet formation is facilitated by the addition of surfactants and often also cosurfactants. Microemulsions are classified as either oil-in-water (O/W) (oil droplets such as octane dispersed throughout aqueous buffer) or water-in-oil (W/O) (aqueous droplets in oil such as hexane). Both microemulsion types have been used as mobile phases for separation in microemulsion HPLC (MELC). There has been a recent increase of interest in this area with new applications and developments such as gradient elution and optimisation of methods using experimental design. O/W microemulsions have been employed as eluents for RP-HPLC while W/O microemulsions have been used for normal phase chromatography. Separations can have superior speed and efficiency to conventional HPLC modes while offering a unique selectivity with excellent resolution. The capability for quantitative and stability-indicating analysis has also been demonstrated. Specific advantages include the ability to operate at low UV wavelengths and elimination of the need for an equilibration rinse between gradients. Operational issues associated with the use of MELC have been identified including the need to add salt to the gradient eluent, relatively high back-pressures and increased need for equipment cleaning compared to conventional RP eluent. This report details the different microemulsion types and compositions used and their reported applications. The use of gradient and isocratic elution is described. The effects on separations of varying operating parameters such as temperature, oil type and concentration, surfactant type and concentration, sample solvent, column type, and organic solvent addition will be discussed and illustrated. [source] Simultaneous determination of morphine, codeine, 6-acetylmorphine, cocaine and benzoylecgonine in hair by liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2009Da-Kong Huang A fast and sensitive liquid chromatography/triple quadrupole tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous determination of morphine, codeine, 6-acetylmorphine (6-AM), cocaine and benzoylecgonine (BE) in hair. Pulverized hair samples were extracted with methanol, and a 50,µL supernatant aliquot was injected into the LC/MS/MS system. Chromatography was performed with an XBridgeÔ phenyl column (3.5,µm particle size, 4.6,×,150,mm), and the mobile phase was composed of methanol and 10,mM ammonium acetate adjusted to pH 4.00 with 99% formic acid (95:5, v/v). A separation run with isocratic elution was completed in 10,min at a flow rate of 500,µL/min. Positive electrospray ionization and multiple reaction monitoring (MRM) with one precursor ion/product ion transition were used for the identification of each analyte. Deuterated analogues as internal standards were used for quantification and qualification. Linearity was established in the concentration range of 100,3000,pg/mg. The limits of detection were 10,pg/mg for morphine, codeine and 6-AM; and 1,pg/mg for cocaine and BE. The precision and accuracy were determined by spiking hair samples at six concentration levels. For all analytes, the relative standard deviations of intra- and inter-day precision were 0.1,6.3% and 1.5,10.6%, respectively. The accuracy ranged from 92.7 to 109.7%. The validated LC/MS/MS method was successfully applied to the analysis of 79 authentic hair samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of the ionophoric coccidiostats narasin, monensin, lasalocid and salinomycin in eggs by liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2005Leen Mortier A sensitive and selective liquid chromatographic tandem mass spectrometric method (LC/MS/MS) for the simultaneous detection of the ionophoric coccidiostats narasin, monensin, lasalocid and salinomycin in whole eggs has been developed. A very simple sample preparation consisting of an extraction with an organic solvent was carried out. Sample extracts were injected into the LC/MS/MS system on a C18 column and an isocratic elution was performed. Nigericin was used as internal standard. The precursor ions produced by electrospray positive ionisation were selected for collisional dissociation with argon into product ions. Validation of the methods was performed based on Commission Decision 2002/657/EC.1 CC, was found to be 1,,g/kg for all four compounds. Monitoring of Belgian egg samples in 2004 revealed that residues of salinomycin, lasalocid and monensin could be found. Copyright © 2005 John Wiley & Sons, Ltd. [source] A liquid chromatography/tandem mass spectrometry method for determination of aristolochic acid-I in rat plasmaBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Yiming Liu Abstract A sensitive, rapid and specific liquid chromatography,electrospray ionization,tandem mass spectrometry method was developed and validated for the determination of aristolochic acid-I (AA-I) in rat plasma. Finasteride was used as the internal standard (IS). The analyte was separated on a Zorbax Eclipse XDB-C18 column by isocratic elution with methanol-10,mM ammonium acetate (75:25, v/v, pH = 7.3) at a flow rate of 0.25,mL/min, and analyzed by mass spectrometry in positive multiple reaction monitoring mode. The precursor-to-product ion transitions of m/z 359.0 , 298.2 and m/z 373.1 , 305.2 were used to detect AA-I and IS, respectively. Good linearity was achieved over a range of 0.4,600,ng/mL. Intra- and inter-day precisions measured as relative standard deviation were less than 13.5%, and accuracy ranged from 94.2 to 97.5%. The developed method was successfully applied in the pharmacokinetic study of AA-I in rats. Copyright © 2009 John Wiley & Sons, Ltd. [source] Solid-phase extraction and analysis of paroxetine in human plasma by ultra performance liquid chromatography,electrospray ionization mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Mitesh Bhatt Abstract A rapid, sensitive and rugged solid-phase extraction ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for determination of paroxetine in human plasma. The procedure for sample preparation includes simple SPE extraction procedure coupled with Hypersil Gold C18 column (100 mm , 2.1 mm, i.d., 1.9 ,m) with isocratic elution at a flow-rate of 0.350 mL/min and fluoxetine was used as the internal standard. The analysis was performed on a triple-quadrupole tandem mass spectrometer by multiple reactions monitoring mode via electrospray ionization. Using 500 ,L plasma, the methods were validated over the concentration range 0.050,16.710 ng/mL for paroxetine, with a lower limit of quantification of 0.050 ng/mL. The intra- and inter-day precision and accuracy of the quality control samples were within 10.0%. The recovery was 69.2 and 74.4% for paroxetine and fluoxetine respectively. Total run time was only 1.9 min. The method was highly reproducible and gave peaks with excellent chromatography properties. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of fenofibric acid in human plasma by ultra performance liquid chromatography,electrospray ionization mass spectrometry: application to a bioequivalence studyBIOMEDICAL CHROMATOGRAPHY, Issue 9 2009Dasandi Bhavesh Abstract A rapid, specific and sensitive ultra-performance liquid chromatography tandem mass spectrometry method was developed for the determination of fenofibric acid in human plasma. The method involves simple, one-step liquid,liquid extraction procedure coupled with an Acquity UPLCTM BEH C18 column (50 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow-rate of 0.2 mL/min and mefenamic acid was used as the internal standard. The Quattro Premier XE mass spectrometry was operated under the multiple reaction-monitoring mode using the electrospray ionization technique. Using 250 µL plasma, the methods were validated over the concentration rang 0.05,7.129 µg/mL, with a lower limit of quantification of 0.05 µg/mL. The intra- and inter-day precision and accuracy were within 9.3%. The recovery was 66.7% and 52.6% for fenofibric acid, and mefenamic acid, respectively. Total run time was 1.8 min only for each sample, which makes it possible to analyze more than 350 samples per day. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of total retronecine esters-type hepatotoxic pyrrolizidine alkaloids in plant materials by pre-column derivatization high-performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Ai-zhen Xiong Abstract A pre-column derivatization high-performance liquid chromatography method with diode array detection was developed and validated to determine the total retronecine esters-type hepatotoxic pyrrolizidine alkaloids (RET-HPAs) in herbs. The RET-HPAs reacted with o -chloranil in methanolic solution heated for 3 h, and an oxidative derivative was produced that could be detected at a maximal absorption of 223 nm. The analysis was performed using a C18 column with an isocratic elution of methanol and aqueous 0.01% triethylamine (adjusted to pH 4 with formic acid), and the detection was carried out with DAD at 223 nm. The validation of the method included linearity, sensitivity, recovery and stability. It showed a good linear regression (r2 > 0.9900) in the range of 2.5,250 µm with a limit of detection (S/N = 3) of 0.5 µm. The method provided desirable repeatability with overall intra- and inter-day variations of less than 4.6%. The obtained recoveries for both of the extraction and derivatization process were between 94.6 and 100.7% (n = 3). Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of quinapril and quinaprilat in human plasma by ultraperformance liquid chromatography,electrospray ionization mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 5 2009Bhavesh Dasandi Abstract A novel, specific and sensitive ultraperformance liquid chromatography tandem mass spectrometry (UPLC,MS/MS) method was developed for the simultaneous determination of quinapril and its active metabolite quinaprilat in human plasma. The method involves a simple, one-step extraction procedure coupled with an Acquity UPLCÔ BEH C18 column (100 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow-rate of 0.2 mL/min and lisinopril as the internal standard. Detection was performed on a triple-quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionization. Using 250 µL plasma, the methods were validated over the concentration range 5.010,500.374 ng/mL for quinapril and 10.012,1000 ng/mL for quinaprilat, with a lower limit of quantification of 5.010 ng/mL for quinapril and 10.012 ng/mL for quinaprilat. The intra- and inter-day precision and accuracy were within 10.0%. The recovery was 85.8, 62.6 and 61.3% for quinapril, quinaprilat and lisinopril, respectively. Total run time was 3.0 min only. Copyright © 2008 John Wiley & Sons, Ltd. [source] Enantioselective HPLC-UV method for determination of eslicarbazepine acetate (BIA 2-093) and its metabolites in human plasmaBIOMEDICAL CHROMATOGRAPHY, Issue 11 2007Gilberto Alves Abstract Eslicarbazepine acetate (BIA 2-093) is a novel central nervous system drug undergoing clinical phase III trials for epilepsy and phase II trials for bipolar disorder. A simple and reliable chiral reversed-phase HPLC-UV method was developed and validated for the simultaneous determination of eslicarbazepine acetate, oxcarbazepine, S- licarbazepine and R -licarbazepine in human plasma. The analytes and internal standard were extracted from plasma by a solid-phase extraction using Waters Oasis® HLB cartridges. Chromatographic separation was achieved by isocratic elution with water,methanol (88:12, v/v), at a flow rate of 0.7 mL/min, on a LichroCART 250-4 ChiraDex (, -cyclodextrin, 5 µm) column at 30°C. All compounds were detected at 225 nm. Calibration curves were linear over the range 0.4,8 µg/mL for eslicarbazepine acetate and oxcarbazepine, and 0.4,80 µg/mL for each licarbazepine enantiomer. The overall intra- and interday precision and accuracy did not exceed 15%. Mean relative recoveries varied from 94.00 to 102.23% and the limit of quantification of the assay was 0.4 µg/mL for all compounds. This method seems to be a useful tool for clinical research and therapeutic drug monitoring of eslicarbazepine acetate and its metabolites S- licarbazepine, R -licarbazepine and oxcarbazepine. Copyright © 2007 John Wiley & Sons, Ltd. [source] Rapid quantification of lisinopril in human plasma by liquid chromatography/tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 4 2007Weiwei Qin Abstract An assay based on protein precipitation and liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed and validated for the quantitative analysis of lisinopril in human plasma. After the addition of enalaprilat as internal standard (IS), plasma samples were prepared by one-step protein precipitation using perchloric acid followed by an isocratic elution with 10 mm ammonium acetate buffer (pH adjusted to 5.0 with acetic acid),methanol (70:30, v/v) on a Phenomenex Luna 5µC18 (2) column. Detection was performed on a triple-quadrupole mass spectrometer utilizing an electrospray ionization (ESI) interface operating in positive ion and selected reaction monitoring (SRM) mode with the precursor to product ion transitions m/z 406,246 for lisinopril and m/z 349,206 for enalaprilat. Calibration curves of lisinopril in human plasma were linear (r = 0.9973,0.9998) over the concentration range 2,200 ng/mL with acceptable accuracy and precision. The limit of detection and lower limit of quantification in human plasma were 1 and 2 ng/mL, respectively. The validated LC-MS/MS method has been successfully applied to a preliminary pharmacokinetic study of lisinopril in Chinese healthy male volunteers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Quantitative LC/MS/MS method and in vivo pharmacokinetic studies of vitexin rhamnoside, a bioactive constituent on cardiovascular system from hawthornBIOMEDICAL CHROMATOGRAPHY, Issue 4 2007Mingjin Liang Abstract A simple and accurate liquid chromatography coupled with tandem mass spectrometry method was developed for determination and in vivo pharmacokinetic studies of vitexin rhamnoside in rat plasma. After protein precipitation using methanol, the analytes were separated by a Luna C18 column with an isocratic elution and analyzed by mass spectrometry in multiple reaction monitoring mode using the respective negative ion at m/z 577.2,293.0 for vitexin rhamnoside and m/z 593.2,413.0 for internal standard (IS) vitexin glucoside. The method was validated systematically within the concentration range 5,5000 µg/L (R > 0.996) and the lower limit of quantitation was 5 µg/L. Acceptable precision and accuracy were acquired for concentrations over the standard curve range. It was further applied to assess pharmacokinetics and bioavailability of vitexin rhamnoside after intravenous and oral administration to rats. The oral bioavailability of vitexin rhamnoside was only 3.57%, which indicated that vitexin rhamnoside had poor absorption or underwent extensive first-pass metabolism. Practical utility of this new LC/MS/MS method was confirmed in pilot pharmacokinetic studies in rats following both intravenous and oral administration. Copyright © 2007 John Wiley & Sons, Ltd. [source] A sensitive and selective determination method of histamine by HPLC with intramolecular excimer-forming derivatization and ,uorescence detectionBIOMEDICAL CHROMATOGRAPHY, Issue 8 2003Takashi Yoshitake Abstract A highly sensitive, selective and simple method is described for the determination of histamine by high-performance liquid chromatography (HPLC) with ,uorescence detection. The method is based on an intramolecular excimer-forming ,uorescence derivatization of histamine with 4-(1-pyrene)butyric acid N -hydroxysuccinimide ester (PSE), followed by reversed-phase HPLC. Histamine, having two amino moieties in a molecule, was converted to the dipyrene-labeled derivative by reaction with PSE. The derivative afforded intramolecular excimer ,uorescence (450,540 nm), which can clearly be discriminated from the monomer ,uorescence (370,420 nm) emitted from PSE. Typically, a 10 µL sample solution was mixed with 100 µL of derivatization reagent solution, which was a mixture of 0.5 mm PSE in acetonitrile and 0.5 mm potassium carbonate in water (8:2, v/v). The derivatization was carried out at 100°C for 90 min. The PSE derivative of histamine could be separated by reversed-phase ODS column with isocratic elution using acetonitrile:water (82:18, v/v) containing 0.03% triethylamine. The detection limit (singnal-to-noise ratio = 3) of histamine was 0.5 fmol for a 30 µL injection. The method was successfully applied to the determination of histamine in human urine, and had enough selectivity and sensitivity for urinary histamine quanti,cation. Copyright © 2003 John Wiley & Sons, Ltd. [source] Simultaneous determination of nicotinamide, pyridoxine hydrochloride, thiamine mononitrate and riboflavin in multivitamin with minerals tablets by reversed-phase ion-pair high performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 8 2002Ke Li A reversed-phase ion-pair high performance liquid chromatographic method (HPLC) has been developed and validated for the routine analysis of nicotinamide, pyridoxine hydrochloride, thiamine mononitrate and riboflavin in multivitamin with minerals tablets. HPLC separation of the vitamins was performed on a Hypersil C18 column and detected by ultraviolet absorbance at 280,nm. The use of methanol-aqueous 0.5% acetic acid solution (18:82, v/v; containing 2.5,mM sodium hexanesulfonate, pH,=,2.8) as the mobile phase at a flow-rate of 1.2,mL/min enables the baseline separation of the four analytes free from interferences with isocratic elution at 30°C. The analysis time was 17,min per injection. The method was linear in the ranges of 5,90, 2.5,90, 5,95 and 25,450,µg/mL for thiamine mononitrate, riboflavin, pyridoxine hydrochloride and nicotinamide, respectively. The average coefficients of variation of within- and between-day assays were 2.2 and 3.6% for thiamine mononitrate, 1.8 and 2.4% for riboflavin, 1.3 and 1.7% for pyridoxine hydrochloride and 1.0 and 1.5% for nicotinamide, respectively. The average recoveries of thiamine mononitrate, riboflavin, pyridoxine hydrochloride and nicotinamide were 97.0, 97.2, 98.9 and 100.4% for the tablets, respectively. The method has been successfully applied to the simultaneous determination of nicotinamide, pyridoxine hydrochloride, thiamine mononitrate and riboflavin in multivitamin with minerals tablets. Copyright © 2002 John Wiley & Sons, Ltd. [source] Application of liquid chromatography,Tandem mass spectrometry method for the analysis of new nonselective ,-adrenergic blocker 1-(1- H -indol-4-yloxy)-3-{[2-(2-methoxy phenoxy)ethylo]amino}propan-2-ol (2F109) in rat plasmaCHIRALITY, Issue 7 2007Maria Walczak Abstract A sensitive and specific liquid chromatography electrospray ionization,tandem mass spectrometry method for the enantioselective determination of the novel ,-adrenolytic compound, 1-(1- H -indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethylo]amino} propan-2-ol, in rat plasma has been developed and validated. Chromatography was performed on a reversed-phase Chiralcel OD-RH analytical column (150 × 4.6 mm, 5 ,m, Daicel Chemical Industries, Tokyo, Japan) with isocratic elution using a mobile phase containing acetonitrile and water with 0.01% formic acid. Detection was achieved by an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 2000 triple quadrupole mass spectrometer. Electrospray ionization (ESI) was used for ion production. The limit of detection in the MRM mode was found to be 1.25 ng/ml. The limit of quantification of both enantiomers was 2.5 ng/ml. The precision and accuracy for both intra- and inter-day determination of 2F109 enantiomers ranged from 2.6 to 12% and from 89.1 to 107.1%. This analytical method allowed us to carry out pharmacokinetic studies in rats. Our findings demonstrate that 2F109 shows stereoselective disposition in rat plasma after i.v. administration. The terminal half-lives of (+)-(R)-2F109 and (,)-(S)-2F109 were 33.5 and 42.6 min, respectively. The AUC0,inf of (+)-(R)-2F109 exceeded that of (,)-(S)-2F109. Chirality, 2007. © 2007 Wiley-Liss, Inc. [source] | ||||||||||