|
| ||
|
|
||
C8 Column (c8 + column)
Selected AbstractsAn improved validated ultra high pressure liquid chromatography method for separation of tacrolimus impurities and its tautomersDRUG TESTING AND ANALYSIS, Issue 3 2010Acharya Subasranjan Abstract A selective, specific and sensitive ultra high pressure liquid chromatography (UHPLC) method was developed for determination of tacrolimus degradation products and tautomers in the preparation of pharmaceuticals. The chromatographic separation was performed on Waters ACQUITY UPLC system and BEH C8 column using gradient elution of mobile phase A (90:10 v/v of 0.1% v/v triflouroacetic acid solution and Acetonitrile) and mobile phase B (90:10 v/v acetonitrile and water) at a flow rate of 0.6 mL min,1. Ultraviolet detection was performed at 210 nm. Tacrolimus, tautomers and impurities were chromatographed with a total run time of 25 min. Calibration showed that the response of impurity was a linear function of concentration over the range 0.3,6 µg mL,1 (r2 , 0.999) and the method was validated over this range for precision, intermediate precision, accuracy, linearity and specificity. For precision study, percentage relative standard deviation of each impurity was < 15% (n = 6). The method was found to be precise, accurate, linear and specific. The proposed method was successfully employed for estimation of tacrolimus impurities in pharmaceutical preparations. Copyright © 2010 John Wiley & Sons, Ltd. [source] Identification of salivary components that induce transition of hyphae to yeast in Candida albicansFEMS YEAST RESEARCH, Issue 7 2009Jelani T.D. Leito Abstract Candida albicans, the major human fungal pathogen, undergoes a reversible morphological transition from single yeast cells to pseudohyphae and hyphae filaments. The hyphae form is considered the most invasive form of the fungus. The purpose of this study is to investigate the effect of saliva on hyphae growth of C. albicans. Candida albicans hyphae were inoculated in Roswell Park Memorial Institute medium with whole saliva, parotid saliva or buffer mimicking the saliva ion composition, and cultured for 18 h at 37 °C under aerobic conditions with 5% CO2. Whole saliva and parotid saliva induced transition to yeast growth, whereas the culture with buffer remained in the hyphae form. Parotid saliva was fractionated on a reverse-phase C8 column and each fraction was tested for inducing transition to yeast growth. By immunoblotting, the salivary component in the active fraction was identified as statherin, a phosphoprotein of 43 amino acids that has been implicated in remineralization of the teeth. Synthetically made statherin induced transition of hyphae to yeast. By deletion of five amino acids at the negatively charged N-terminal site (DpSpSEE), yeast-inducing activity and binding to C. albicans were increased. In conclusion, statherin induces transition to yeast of C. albicans hyphae and may thus contribute to the oral defense against candidiasis. [source] Direct quantification of 11-nor-,9 -tetrahydrocannabinol-9-carboxylic acid in urine by liquid chromatography/tandem mass spectrometry in relation to doping control analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2010C. Chebbah An accurate and precise method for the quantification of 11-nor-,9 -tetrahydrocannabinol-9-carboxylic acid (THCA) in urine by liquid chromatography/tandem mass spectrometry (LC/MS/MS) for doping analysis purposes has been developed. The method involves the use of only 200,µL of urine and the use of D9 -THCA as internal standard. No extraction procedure is used. The urine samples are hydrolysed using sodium hydroxide and diluted with a mixture of methanol/glacial acetic acid (1:1). Chromatographic separation is achieved using a C8 column with gradient elution. All MS and MS/MS parameters were optimised in both positive and negative electrospray ionisation modes. For the identification and the quantification of THCA three product ions are monitored in both ionisation modes. The method is linear over the studied range (5,40,ng/mL), with satisfactory intra-and inter-assay precision, and the relative standard deviations (RSDs) are lower than 15%. Good accuracy is achieved with bias less than 10% at all levels tested. No significant matrix effects are observed. The selectivity and specificity are satisfactory, and no interferences are detected. The LC/MS/MS method was applied for the analysis of 48 real urine samples previously analysed with a routine gas chromatography/mass spectrometry (GC/MS) method. A good correlation between the two methods was obtained (r2,>,0.98) with a slope close to 1. Copyright © 2010 John Wiley & Sons, Ltd. [source] Determination of paclitaxel in human plasma following the administration of Genaxol or Genetaxyl by liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2006Erin R. Gardner A sensitive and specific assay for paclitaxel in plasma has been developed to overcome limitations in previously published assays, using liquid chromatography with tandem mass spectrometric detection. Plasma samples (100,µL) were subjected to liquid-liquid extraction with 1-chlorobutane/acetonitrile (4:1, v/v), with [2H5]paclitaxel employed as the internal standard. Chromatography was carried out with a Waters SymmetryShield C8 column (50,×,2.1 mm, 3.5,µm). The total run time, including equilibration, was 8 min, using a gradient of acetonitrile and 10,mM ammonium formate, pH 4.0. The assay is accurate and precise over the range of 2,2500,ng/mL and has been successfully applied to study the clinical pharmacokinetics of two formulations of paclitaxel, Genaxol and Genetaxyl, given orally and intravenously. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous determination of lamivudine, stavudine and nevirapine in human plasma by LC,MS/MS and its application to pharmacokinetic study in clinicBIOMEDICAL CHROMATOGRAPHY, Issue 9 2010Zhou Li Abstract A new high-throughput LC,MS/MS method for the simultaneous determination of lamivudine (3TC), stavudine (d4T) and nevirapine (NVP) in human plasma is presented, with zidovudine as an internal standard. The analytes were extracted from plasma by protein precipitation and only 150,,L plasma was needed. Chromatographic separation was achieved on a Shiseido C8 column (150 × 2.0,mm, 5,,m) with a total run time of 6,min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring under positive ionization mode with an electrospray ionization interface. The method was developed and validated over the concentration range of 25,5000,ng/mL for 3TC and NVP and 20,4000,ng/mL for d4T. The method was validated in terms of intra- and inter-day precision (,8.6%), accuracy (within ± 8.4%), linearity and specificity. The method has been successfully applied to the pharmacokinetic study of a combination treatment of 300,mg lamivudine, 30,mg stavudine and 200,mg nevirapine in 22 healthy male volunteers under fasting conditions. Copyright © 2010 John Wiley & Sons, Ltd. [source] Liquid chromatography,mass spectrometry for analysis of a novel ,2 -adrenoceptor agonist trantinterol and its metabolites in beagle dog urineBIOMEDICAL CHROMATOGRAPHY, Issue 3 2010Yanjuan Wang Abstract A liquid chromatography,tandem mass spectrometry method was developed for the identification of metabolites of trantinterol, a novel ,2 -adrenoceptor agonist, in beagle dog urine. The separation of metabolites was performed on a reversed-phase C8 column using 0.1% formic acid in water and methanol (70 : 30, v/v) as the mobile phase. The structural information and elemental information of metabolites were acquired by an electrospray ionization tandem mass spectrometer and a quadrupole time-of-flight mass spectrometer, respectively. A total of 13 metabolites were detected and characterized on the basis of their tandem MS/MS fragmentation patterns. The accurate masses of nine metabolites were determined and two metabolites were further confirmed by comparing with reference standards. The metabolic pathways of trantinterol in beagle dog are proposed. Copyright © 2009 John Wiley & Sons, Ltd. [source] An analytical method for cyclosporine using liquid chromatography,mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Srividya V. Kanduru Abstract A liquid chromatographic mass spectrometric (LC-MS) assay has been developed for cyclosporine A (CyA) in rat plasma using amiodarone as internal standard (IS). Rat plasma (100,µL) containing drug and IS were extracted using liquid,liquid extraction with 4,mL of 95:5 ether:methanol. After evaporation of the organic layer the residue was reconstituted with 500,µL of water. Then the aqueous layer was transferred to LC-MS sample vials. A 10,µL volume was injected. The analysis was performed on a C8 column 3.5,µm (2.1 × 50,mm) heated to 60°C with a mobile phase consisting of acetonitrile:methanol:0.2% NH4OH (60:20:20) at an isocratic flow-rate of 0.2,mL/min. The ions used for quantitation of CyA and IS were m/z 1202.8 and 645.9, with retention times of 3.35 and 4.72,min, respectively. Linear relationships (r2,>,0.99) were achieved between plasma or blood concentration and peak height ratios (drug:IS) over the concentration range 50,5000,ng/mL. The CV% and mean error were <19%. Based on validation data, the lower limit of quantification for the assay was 50,ng/mL. The reported assay method displayed high measures of linearity, sensitivity, reliability and precision, allowing its applicability in pharmacokinetic studies in rat. Copyright © 2009 John Wiley & Sons, Ltd. [source] Liquid chromatography-tandem mass spectrometry for the determination of a new oxazolidinone antibiotic DA-7867 in human plasmaBIOMEDICAL CHROMATOGRAPHY, Issue 2 2004Hye Young Ji Abstract A liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for the determination of a new ox-azolidinone antibiotic DA-7867, (S)-[N -3-(4-(2-(1-methyl-5-tetrazolyl)-pyridine-5-yl)-3-,uorophenyl)-2-oxo-5-oxazolidinyl]methyl acetamide, in human plasma was developed. DA-7867 and internal standard, linezolid, were extracted from human plasma with ethyl acetate at acidic pH. A reverse-phase LC separation was performed on Luna C8 column with the mixture of acetonitrile,ammonium formate (10 mm, pH 4.5; 35:65, v/v) as mobile phase. The analytes were determined using an electrospray ionization tandem mass spectrometry in the multiple-reaction-monitoring mode. The lower limits of quanti,cation for DA-7867 was 2.5 ng/mL. The single liquid,liquid extraction quantitatively recovered DA-7867 and internal standard from plasma samples at the ranges of 82.2,86.7%. DA-7867 was stable in blank human plasma at room temperature for 24 h and following three freeze,thaw cycles. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||