Home About us Contact
|
Home About us Contact | ||
|
|
||
High-performance Liquid Chromatography Method (high-performance + liquid_chromatography_method)
Selected AbstractsHigh-performance liquid chromatography method for determination of carnosic acid in rat plasma and its application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 7 2009Haixia Yan Abstract A sensitive and reproducible high-performance liquid chromatography method with ultraviolet detection (UV) was developed for the determination of carnosic acid (CA) in rat plasma. After simple acidification and liquid,liquid extraction of plasma samples using gemfibrozil as an internal standard, the supernatant was evaporated to dryness under a gentle stream of nitrogen. The residue was reconstituted in 200 µL before being injected into the chromatographic system. The analysis was performed on a C18 column protected by an ODS guard column using acetonitrile,0.1% phosphoric acid (55:45, v/v) as mobile phase, and the wavelength of the UV detector was set at 210 nm. The calibration curve was linear over the range of 0.265,265.0 µg/mL with a correlation coefficient of 0.9997. The recovery for plasma samples of 0.530, 13.25, 132.5 and 265.0 µg/mL was 72.2, 87.9, 90.4 and 94.7%, respectively. The intra-day and inter-day relative standard deviations for the measurements of quality control samples were less than 3.1%. The stability of the plasma samples was also validated. This method was successfully used to study the pharmacokinetics and bioavailability of CA in rats. Copyright © 2009 John Wiley & Sons, Ltd. [source] Role of shear stress on nitrite and NOS protein content in different size conduit arteries of swineACTA PHYSIOLOGICA, Issue 2 2009X. Guo Abstract Aim:, Inherent fundamental difference exists among arteries of different sizes. The purpose of this study was to evaluate the relation between regional difference of wall shear stress (WSS) in various sizes arteries and contents of nitrite and NO synthase (NOS) isoforms. Methods:, Five different conduit arteries in a wide range of diameter (1,8 mm) were examined in the hind limbs of 13 pigs. Blood flow rate and outer diameter were measured in vivo to determine WSS. Arterial tissues were harvested for the measurement of nitrite and NOS protein contents. The concentration of nitrite, a product of NO synthesis, was determined by high-performance liquid chromatography method. Western blot analysis was used to assess the protein contents of endothelial NOS (eNOS), inducible NOS (iNOS) and neuronal NOS (nNOS). Results:, Our data show that WSS increases with a decrease in artery diameter. Nitrite level increases with increasing WSS and hence decreases with artery diameter. The eNOS protein contents decrease with an increase in diameter. No significant difference for iNOS and nNOS protein contents was found with different artery diameter. A significant positive correlation between tissue nitrite and eNOS protein contents was also observed. Finally, the WSS-normalized eNOS is not significantly different in various size vessels. Conclusion:, Regional difference in blood flow has no effect on iNOS and nNOS protein contents in these conduit arteries. Regional difference in eNOS expression and nitrite contents may be related to the WSS-induced NO by the endothelium under normal physiological conditions. [source] BIOMARKER: Phosphatidylethanol as a sensitive and specific biomarker,comparison with gamma-glutamyl transpeptidase, mean corpuscular volume and carbohydrate-deficient transferrinADDICTION BIOLOGY, Issue 1 2007Susanne Hartmann ABSTRACT Phosphatidylethanol (PEth), a direct ethanol metabolite, is detectable in blood for more than 2 weeks after sustained ethanol intake. Our aim was to assess the usefulness of PEth [comparing sensitivity, specificity and the area under the curve (AUC)] as compared with carbohydrate-deficient transferrin (CDT), gamma-glutamyl transpeptidase (GGT) and mean corpuscular volume (MCV), calculating the results from sober patients against those from alcohol-dependent patients during withdrawal. Fifty-six alcohol-dependent patients (ICD-10 F 10.25) in detoxification, age 43 years, GGT 81 U/l, MCV 96.4 fl, %CDT 4.2, 1400 g ethanol intake in the last 7 days (median), were included in the study. Over the time of 1 year, 52 samples from 35 sober forensic psychiatric addicted in-patients [age 34 years, GGT 16 U/l, MCV 91 fl, CDT 0.5 (median)] in a closed ward were drawn and used for comparison . PEth was measured in heparinized whole blood with a high-performance liquid chromatography method. GGT, MCV and %CDT were measured using routine methods. A receiver operating characteristic curve analysis was carried out, with ,current drinking status' (sober/drinking) as the state variable and PEth, MCV, GGT and CDT as test variables. The resulting AUC was 0.974 (P < 0.0001, confidence interval 0.932,1.016) for PEth. At a cut-off of 0.36 µmol/l, the sensitivity was 94.5% and specificity 100%. The AUC for CDT, GGT and MCV were 0.931, 0.894 and 0.883, respectively. A significant Spearman's rank correlation was found between PEth and GGT (r = 0.739), CDT (r = 0.643), MVC (r = 0.639) and grams of ethanol consumed in the last 7 days (r = 0.802). Our data suggest that PEth has potential to be a sensitive and specific biomarker, having been found in previous studies to indicate longer lasting intake of higher amounts of alcohol. [source] Simultaneous determination of chlorinated bacteriostats in cosmetic and pharmaceutical productsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2005L.-H. Wang A high-performance liquid chromatography method has been developed for simultaneous determination of triclosan (2,4,4-trichloro-2-hydroxydiphenyl ether) and triclocarban (3,4,4-trichlorocarbanilide) in cosmetic and pharmaceutical products. The two compounds could be separated on a Nucleosil C18 column and eluted with acetonitrile and water (70:30, v/v) as the mobile phase and detected with a differential refractive index detector. The retention times of triclosan and triclocarban were 5.81 and 2.99 min, respectively. The results obtained were in good agreement with those obtained by a differential pulse voltammetric method. [source] Hypericum perforatum,Chemical profiling and quantitative results of St. John's Wort products by an improved high-performance liquid chromatography methodJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2002M. Ganzera Abstract The analysis of flavonoids, naphthodianthrones, and the phloroglucinol derivative hyperforin in H. perforatum is described in this article. In a 35-min HPLC run nine major compounds could be identified and baseline separated in the methanolic plant extracts. For an optimum separation the mobile phase consisted of 10 mM ammonium acetate buffer (pH 5.0) and an acetonitrile/methanol mixture; a Synergi MAX-RP 80 Å column (C-12 material) was used as stationary phase. Detection was performed at 270 nm, and the identity of the compounds was confirmed in an LC-MS experiment. Commercial St. John's Wort products were analyzed and qualitative and quantitative results are discussed. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:623,630, 2002 [source] Permeation of bioactive constituents from Arnica montana preparations through human skin in-vitroJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 9 2006I. A. Tekko This study investigated and characterised transdermal permeation of bioactive agents from a topically applied Arnica montana tincture. Permeation experiments conducted over 48 h used polydimethylsiloxane (silastic) and human epidermal membranes mounted in Franz-type diffusion cells with a methanol-water (50:50 v/v) receptor fluid. A commercially available tincture of A. montana L. derived from dried Spanish flower heads was a donor solution. Further donor solutions prepared from this stock tincture concentrated the tincture constituents 1, 2 and 10 fold and its sesquiterpene lactones 10 fold. Permeants were assayed using a high-performance liquid chromatography method. Five components permeated through silastic membranes providing peaks with relative retention factors to an internal standard (santonin) of 0.28, 1.18, 1.45, 1.98 and 2.76, respectively. No permeant was detected within 12 h of applying the Arnica tincture onto human epidermal membranes. However, after 12 h, the first two of these components were detected. These were shown by Zimmermann reagent reaction to be sesquiterpene lactones and liquid chromatography/diode array detection/mass spectrometry indicated that these two permeants were 11,13-dihydrohelenalin (DH) analogues (methacrylate and tiglate esters). The same two components were also detected within 3 h of topical application of the 10-fold concentrated tincture and the concentrated sesquiterpene lactone extract. [source] Simple method for determination of five terpenoids from different parts of Tripterygium wilfordii and its preparations by HPLC coupled with evaporative light scattering detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2007Xiao-Ling Luo Abstract By optimizing the extraction, separation, and analytical conditions, a reliable and accurate high-performance liquid chromatography method coupled with evaporative light scattering detection (ELSD) was developed for simultaneous determination of five terpenoids, i. e., triptolide, tripchlorolide, demethylzelastral, wilforlide B, and wilforlide A, in root, stem, leaves, root bark, twig, and root without bark of Tripterygium wilfordii Hook. f and six of its herbal preparations. This approach would thus provide a more accurate and general method for evaluating the quality of the herb and its preparations. Separation of these five terpenoids was achieved on a ZORBAX Eclipse XDB-C8 column with gradient elution using water and acetonitrile as solvents, both containing 0.05% formic acid, at a temperature of 30°C and a flow rate of 0.8 mL/min. The drift tube temperature of ELSD was set at 100°C, and the nitrogen flow rate at 1.5 L/min. Good linear relationships were obtained with correlation coefficients for the analytes exceeding 0.992, and the LOD and LOQ were less than 0.149 ,g and 0.297 ,g on column, respectively. Intra-day and inter-day precision of the analytes were less than 1.25% and 5.97%, respectively, and the average recovery rates obtained were in the range of 95.9 ± 3.7% to 100.4 ± 5.0% for all terpenoids with RSDs below 4.99%. Quantitative analysis of the five terpenoids in different parts of Tripterygium wilfordii and its six preparations showed that the contents of the terpenoids varied significantly. The tender root contained higher concentrations of triptolide, tripchlorolide, demethylzelastral, and wilforlide B than any other part of the herb. Correspondingly, the root bark contained the greatest concentration of wilforlide A, and the stem and twig came in second and third. This suggested that we could infer whether the medicinal materials were absolute roots without bark or not from the comparative contents of these terpenoids in the tablets in view of the fact that only the roots without bark are the valid officinal part of the plant. This method and the quantitation results obtained can provide a scientific and general as well as simple and convenient approach for the product manufacturers to set up quality control standards and for informing the public about the quality and safety of the preparations. [source] The effect of whole-body sunbed ultraviolet A exposure on the pharmacokinetics of the photolabile drug nifedipinePHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 3 2000H. S. Al-Ajmi The calcium antagonist nifedipine absorbs ultraviolet A (UVA) radiation and readily photodegrades in vitro to a toxic nitroso-pyridine photoproduct. We examined whether whole body exposure of normal subjects to sunbed UVA radiation would affect the pharmacokinetics of nifedipine. Eight healthy, male, Caucasian volunteers (phototypes I,III) participated in this ethically approved, randomised, cross-over study. Each subject attended on 2 occasions, one week apart, and on each occasion was given a single oral dose (10 mg) of nifedipine following which blood samples were collected at 0, 0.5, 1. 1.5, 2, 2.5, 3, 3.5, 4, 5, 6 and 7 h. During one of the visits, 15 min after nifedipine ingestion, a whole-body UVA (sunbed comprising Philips R-UVA lamps) dose of 70% of the individual's predetermined minimal phototoxic dose was delivered over a period of 17,36 min. Plasma nifedipine levels were measured using a standard reverse-phase high-performance liquid chromatography method. The area under the plasma concentration-time curve (AUC) of nifedipine during the UVA irradiation session (median 206 ng,·,ml,1,·,h,1) was significantly higher than during the non-irradiation control session (median 174.5 ng,·,ml,1,·,h,1) (P=0.03; 95% C.I. for difference in medians 9.9 to 55.9 ng,·,ml,1,·,h,1). UVA irradiation did not significantly affect any of the other measured pharmacokinetic parameters (Cmax, t1/2, tmax). We demonstrate that sunbed UVA irradiation does not lead to in vivo photodegradation of nifedipine in healthy humans after a single dose. The apparent increase in AUC during UVA irradiation may be due to slightly slower metabolism of nifedipine in the presence of toxic photoproduct(s) or due to blood distribution changes affecting liver blood flow. [source] Simultaneous quantification of three major triterpenoids in radix asteris by high-performance liquid chromatography with evaporative light scattering detectionPHYTOCHEMICAL ANALYSIS, Issue 3 2009Yaping Tian Abstract Introduction Radix asteris, with triterpenoids as its main pharmacological effective compounds, has been widely used for moistening the lung, dispersing phlegm and relieving cough. Quantification of the triterpenoids is important for the quality control of Radix asteris. Objective To establish a high-performance liquid chromatography method with evaporative light scattering detection for simultaneous determination of three major triterpenoids, shionone, friedelin and epi-friedelinol, in Radix asteris. Methodology The optimal chromatographic conditions were achieved on an RP18 column with gradient elution by acetonitrile and 0.05% acetic acid in 22 min with ELSD set at an evaporating temperature of 40°C. Validation of the method included tests of linearity, sensitivity, precision, repeatability, stability and accuracy. Results All calibration curves showed good linear regression (r2 > 0.9991) within test ranges. The established method showed good precision and accuracy with overall intra-day and inter-day variations of 1.61,2.97 and 1.74,2.42%, respectively, and overall recoveries of 97.35,101.13% for the three compounds analysed. Conclusion The method developed was successfully applied to quantify the main triterpenoids in 14 Radix asteris samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] Development and validation of a high-performance liquid chromatography method for the simultaneous determination of aspirin and folic acid from nano-particulate systemsBIOMEDICAL CHROMATOGRAPHY, Issue 9 2010Abhishek Chaudhary Abstract Attention has shifted from the treatment of colorectal cancer (CRC) to chemoprevention using aspirin and folic acid as agents capable of preventing the onset of colon cancer. However, no sensitive analytical method exists to simultaneously quantify the two drugs when released from polymer-based nanoparticles. Thus, a rapid, highly sensitive method of high-performance liquid chromatography analysis to simultaneously detect low quantities of aspirin (hydrolyzed to salicylic acid, the active moiety) and folic acid released from biodegradable polylactide-co-glycolide (PLGA) copolymer nanoparticles was developed. Analysis was done on a reversed-phase C18 column using a photodiode array detector at wavelengths of 233,nm (salicylic acid) and 277,nm (folic acid). The mobile phase consisted of acetonitrile,0.1% trifluoroacetic acid mixture programmed for a 30,min gradient elution analysis. In the range of 0.1,100,,g/mL, the assay showed good linearity for salicylic acid (R2 = 0.9996) and folic acid (R2 = 0.9998). The method demonstrated good reproducibility, intra- and inter-day precision and accuracy (99.67, 100.1%) and low values of detection (0.03, 0.01,,g/mL) and quantitation (0.1 and 0.05,,g/mL) for salicylic acid and folic acid, respectively. The suitability of the method was demonstrated by simultaneously determining salicylic acid and folic acid released from PLGA nanoparticles. Copyright © 2009 John Wiley & Sons, Ltd. [source] Development and validation of a rapid and sensitive HPLC method for the quantification of 5-fluorocytosine and its metabolitesBIOMEDICAL CHROMATOGRAPHY, Issue 5 2010Kinta M. Serve Abstract To study the intracellular metabolism of the prodrug 5-fluorocytosine (5FC), we developed a novel reverse-phase high-performance liquid chromatography method to simultaneously detect 5FC and its four major anabolic metabolites: 5-fluorouracil, 5-fluorouridine, 5-fluorouridine-monophosphate and 5-fluoro-2,deoxyuridine-5,-monophosphate. Separation of each compound was accomplished under isocratic conditions using a C18 column and mobile phase of formic acid,water (1,:,99,v/v). The method was validated for both accuracy and reproducibility in cell culture media. Additionally, metabolites were assessed for stability at ambient temperatures and following freeze,thaw cycles. Calibration curves were linear over a range of 1,200,,g/mL. Limit of quantification for four of the five compounds was 1,,g/mL in cell culture media (RSD < 11%). This method was successfully used to monitor intracellular conversion of 5FC to its metabolic products over a 24h period. Copyright © 2009 John Wiley & Sons, Ltd. [source] A simple and rapid high-performance liquid chromatography method for determination of alendronate sodium in beagle dog plasma with application to preclinical pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Jian Meng Abstract A simple and rapid high performance liquid chromatographic (HPLC) method for quantifying alendronate in beagle dog plasma was developed, validated and applied to a pharmacokinetic study. The sample preparation involved coprecipitation with CaCl2 and derivatization with o -phthalaldehyde. Chromatographic separation was achieved on a DiamonsilÔ C18 (250 × 4.6,mm, 5,µm) using acetonitrile,0.4% EDTA-Na2 (16:84, v/v) containing 0.034% of NaOH as mobile phase. The fluorimetric detector was operated at 339,nm (excitation) and 447 nm (emission). The linearity over the concentration range of 5.00,600,ng/mL for alendronate was obtained and the lower limit of quantification was 5.00,ng/mL. For each level of quality control samples, inter-day and intra-day precisions were less than 8.52 and 7.42% and accuracies were less than 9.07%. The assay was applied to the analysis of samples from a pharmacokinetic study. Following the oral administration of 70,mg alendronate sodium to beagle dogs, the maximum plasma concentration (Cmax) and elimination half-life were 152,±,27.3 and 1.75,± 0.267,h, respectively. The method was demonstrated to be highly feasible and reproducible for pharmacokinetic studies. Copyright © 2009 John Wiley & Sons, Ltd. [source] Reversed-phase liquid chromatography method for the determination of total plasma thiols after derivatization with 1-benzyl-2-chloropyridinium bromideBIOMEDICAL CHROMATOGRAPHY, Issue 7 2009Krzysztof Ku, mierek Abstract A high-performance liquid chromatography method was developed for simultaneous detection and quantitation of total cysteine, glutathione, homocysteine and cysteinylglycine in human plasma. The two key steps in the analysis are reduction of disulfides and treatment with 1-benzyl-2-chloropyridinium bromide, which rapidly and quantitatively reacts with thiol groups to form stable S- pyridinium derivatives with intense UV absorption. The derivatives are well separated on a Zorbax SB C18 column using reversed-phase high-performance liquid chromatography and monitored at 315 nm. The calibration graphs were linear over concentration ranges covering most experimental and clinical cases with a regression coefficients better than 0.999. The detection and quantitation limits for all analytes were 0.2 and 0.5 µmol/L, respectively. The recoveries were 99.25,101.68%. The intra- and interassay imprecisions were 0.88,4.24 and 1.68,5.14%, respectively. The method was applied for plasma samples donated by apparently healthy volunteers. Copyright © 2009 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography method for determination of carnosic acid in rat plasma and its application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 7 2009Haixia Yan Abstract A sensitive and reproducible high-performance liquid chromatography method with ultraviolet detection (UV) was developed for the determination of carnosic acid (CA) in rat plasma. After simple acidification and liquid,liquid extraction of plasma samples using gemfibrozil as an internal standard, the supernatant was evaporated to dryness under a gentle stream of nitrogen. The residue was reconstituted in 200 µL before being injected into the chromatographic system. The analysis was performed on a C18 column protected by an ODS guard column using acetonitrile,0.1% phosphoric acid (55:45, v/v) as mobile phase, and the wavelength of the UV detector was set at 210 nm. The calibration curve was linear over the range of 0.265,265.0 µg/mL with a correlation coefficient of 0.9997. The recovery for plasma samples of 0.530, 13.25, 132.5 and 265.0 µg/mL was 72.2, 87.9, 90.4 and 94.7%, respectively. The intra-day and inter-day relative standard deviations for the measurements of quality control samples were less than 3.1%. The stability of the plasma samples was also validated. This method was successfully used to study the pharmacokinetics and bioavailability of CA in rats. 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] Simultaneous quantitation of three major triterpenoid glycosides in Centella asiatica extracts by high performance liquid chromatography with evaporative light scattering detectionBIOMEDICAL CHROMATOGRAPHY, Issue 2 2008Feng-Lun Zhang Abstract A high-performance liquid chromatography method with evaporative light scattering detection was established for simultaneous determination of three major triterpenoid glycosides, i.e. asiaticoside, madecassoside and asiaticoside-B, in Centella asiatica extracts. The optimal chromatographic conditions were achieved on a COSMOSIL 5C18 -MS-II column by constant elution with water (0.01% trifluoroacetic acid, v/v) and acetonitrile (1.0% methyl tert-butyl ether, 0.01% trifluoroacetic acid, v/v) (78:22) as mobile phase at a flow rate of 1.0 mL/min; the column temperature was 30°C. The evaporative light scattering detector was set at an evaporating temperature of 40°C and nitrogen gas pressure of 3.5 bar. The validation of the method included tests of linearity, sensitivity, precision, repeatability, stability and accuracy. All calibration curves showed good linear regression (r2 > 0.9993) within test ranges. The established method showed good precision and accuracy with overall intra-day and inter-day variations of 1.73,3.06 and 3.89%,4.92%, respectively, and overall recoveries of 97.63,99.39% for the three compounds analyzed. The method developed was successfully applied to quantify the main triterpenoid glycosides in Centella asiatica extracts from different companies. Copyright © 2007 John Wiley & Sons, Ltd. [source] Determination of picroside II in dog plasma by HPLC and its application in a pharmacokinetics studyBIOMEDICAL CHROMATOGRAPHY, Issue 4 2005Fu-Chuan Yang Abstract A sensitive and simple high-performance liquid chromatography method with UV detection was developed and validated for determining picroside II in dog plasma. Paeoni,orin was employed as internal standard and the sample pre-treatment procedure consists of deproteinization by addition of acetonitrile. Chromatographic separations were performed on a Shimadzu VP-ODS column (250 × 4.6 mm i.d., 5 µm). The mobile phase consisted of acetonitrile,0.1% acetic acid aqueous (v/v), 23:77, v/v, at a rate of 1 mL/min. Detection was carried out at a wavelength of 266 nm. Calibration standards ranged from 0.25 to 500 µg/mL in dog plasma and the mean correlation coef,cient of 0.9981 was found for the linear calibration curves (n = 6). The limit of quanti,cation (LOQ) was 0.25 µg/mL. Intra- and inter-assay RSD ranged from 0.70 to 7.5%. Accuracy (%bias) ranged from ,6.3 to 6.0%. This method was applied to the pharmacokinetic study of picroside II in dogs. The study demonstrated the plasma picroside II concentration,time curves were ,tted to the two-compartment open model and showed linear pharmacokinetics. Copyright © 2005 John Wiley & Sons, Ltd. [source] Determination of abacavir in human plasma by high-performance liquid chromatography with ultraviolet detection and the analytical error functionBIOMEDICAL CHROMATOGRAPHY, Issue 10 2004Salut M. Ferrer Abstract A rapid and simple high-performance liquid chromatography method has been developed for the determination of the HIV-1 reverse transcriptase inhibitor abacavir in human plasma. It included a single liquid,liquid extraction procedure with a mixture of ethyl acetate-diethyl ether prior to reversed-phase chromatography on a C18 column and C18 precolumn insert. Ultraviolet detection was set at 285 nm. The mobile phase consisted of water,acetonitrile (83:17, v/v) and the ,ow rate was kept at 1 mL/min. The total run time for a single analysis was 10 min. The method has been validated over the range 50,2500 ng/mL. The assay was linear over the entire concentration range (r2 = 0.9993). Intra- and inter-day precision and accuracy were less than 8.1 and ,5.2%, respectively. The extraction recovery was greater than 94.3%. Abacavir was stable under the relevant storage conditions tested. After the validation, the analytical error function was established as standard deviation (SD; ng/mL) = ,1.072 + 0.037C (C = theoretical concentration value). The method developed and its associated analytical error function will be suitable for pharmacokinetic studies and monitoring of HIV-1 patients. Copyright © 2004 John Wiley & Sons, Ltd. [source] A high-performance liquid chromatography method using ultraviolet detection for the quantitation of flavopiridol from human plasmaBIOMEDICAL CHROMATOGRAPHY, Issue 6 2002Suoping Zhai Flavopiridol is an inhibitor of cyclin-dependent kinase, a key regulator of cell cycle, and is currently under clinical trials. We developed and validated an HPLC assay method for the quantitation of flavopiridol in human plasma samples. The sample preparation consisted of protein precipitation with acetonitrile. Separation was accomplished on a C18 column and a C18 precolumn insert utilizing a gradient profile consisting of ammonium acetate and methanol. Ultraviolet detection was set at 268,nm for flavopiridol and 323,nm for umbelliferone, the internal standard. The method was validated over flavopiridol concentration range of 0.025,3.0,µg/mL using 250,µL of plasma. The assay was linear over this concentration range with a coefficient of variation less than 10% for inter- and intra-assay. The retention times were around 6.2,min for umbelliferone and 9.8,min for flavopiridol. The recoveries of flavopiridol and umbelliferone were 88.6,±,1.0% and 97.1,±,3.7%, respectively. This method is suitable for quantifying flavopiridol in plasma samples and further characterizing the clinical pharmacology of this compound. Copyright © 2002 John Wiley & Sons, Ltd. [source] An improved high-performance liquid chromatography method for quantification of methotrexate polyglutamates in red blood cells of children with juvenile idiopathic arthritisBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2009Hroch Abstract Methotrexate is used widely in the pharmacotherapy of juvenile idiopathic arthritis. Polyglutamates of methotrexate are active metabolites which accumulate in cells including erythrocytes. Their intracellular concentration may reflect methotrexate bioavailability and, at the same time, may serve as a bioindicator for optimization of methotrexate therapy and drug monitoring. Therefore, a simple and selective isocratic reversed phase chromatographic method with fluorescence detection (excitation/emission wavelengths of 370/463,nm) was developed which quantifies the sum of all methotrexate polyglutamates in erythrocytes as methotrexate after their enzymatic conversion with ,-glutamylhydrolase. Separation was carried out on a Phenomenex GEMINI C18 column using a mobile phase flowing at a rate of 0.6,ml/min and consisting of a mixture (110:890:0.25 v/v) of acetonitrile, ammonium acetate buffer (0.05,m, pH=5.5) and hydrogen peroxide 30% (w/w). The method was found linear over the concentration range of 25,400,nmol/l. Its intra- and inter-day precision and accuracy were characterized by coefficients of variation and relative errors less than 20%. The limits of detection and quantification achieved 10.9 and 32.9,nmol/l, respectively. The method was proved suitable for monitoring the concentration of methotrexate polyglutamates in erythrocytes of patients with juvenile idiopathic arthritis. Copyright © 2009 John Wiley & Sons, Ltd. [source] Percutaneous absorption of the sunscreen benzophenone-3 after repeated whole-body applications, with and without ultraviolet irradiationBRITISH JOURNAL OF DERMATOLOGY, Issue 2 2006H. Gonzalez Summary Background, Benzophenone-3 (BZ-3; 2-hydroxy-4-methoxybenzophenone, oxybenzone) is commonly used to absorb ultraviolet (UV) radiation. BZ-3 penetrates the skin and can be found in the urine. The amount varies between 0·4% and 2%. This seems to be the main metabolic pathway in rats. Objectives, To investigate the total amount of BZ-3 excreted in the urine after repeated topical whole-body applications of a sunscreen and to see if UV radiation has any effect on the amount excreted. Methods, Twenty-five volunteers applied a commercially available sunscreen containing 4% BZ-3 morning and night for 5 days. Their urine was measured during those 5 days and during a further 5 days after the last application. They were divided into groups A (unirradiated) and B. Group B received UV radiation according to skin type: UVA between 400 and 707 J cm,2, and UVB between 0·46 and 2·0 J cm,2. BZ-3 in urine was analysed with a high-performance liquid chromatography method. Results, The volunteers excreted 1·2,8·7% (mean 3·7%) of the total amount of BZ-3 applied. There was no significant difference between the two groups (P < 0·99, t -test). Conclusions, We show that a large amount of BZ-3 is absorbed. BZ-3 is accumulated in the body as the volunteers excreted BZ-3 5 days after the last application. [source] | ||||||||||||||||