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Excellent Linearity (excellent + linearity)
Selected AbstractsQuantification 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] Rapid gas chromatography/mass spectrometry quinine determination in plasma after automated solid-phase extractionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2006Richard Damien The combined use of an automatic solid-phase extraction (SPE) apparatus with Oasis MCX cartridges and gas chromatography/mass spectrometry (GC/MS) to rapidly quantify quinine in biological samples with cyproheptadine as the internal standard is described. The selected ion monitoring mode, with the quantification ions m/z 136 and 287 (qualifier ions: m/z 261, 381 and 215, 96), allows the estimation of quinine levels, respectively. Separation was completed within 12.7,min. Excellent linearity was found up to 10 000,µg/L of plasma. The limit of detection (LOD) was 12.2,µg/L and the limit of quantification (LOQ) was 40.6,µg/L. High reproducibility (intra-assay CV range 1.9,4.3%, inter-assay CV range 2.2,11.3%) and accuracy values (intra-assay range 83.2,103.7%, inter-assay range 86.8,103.7%) were obtained. Recoveries were concentration-independent (97.2% and 89.8% for 4000 and 10 000,µg/L, respectively). This sensitive, simple assay for quinine in various matrices meets the current requirements for bioanalytical assays and may be used to monitor quinine levels in patients developing severe malaria with acute renal failure during hemofiltration. The optimal quinine dose in this situation is not really established and to improve clinical care, quinine concentrations might be explored to improve efficacy and minimise potential toxicity. Copyright © 2006 John Wiley & Sons, Ltd. [source] [2H/H] Isotope ratio analyses of [2H5]cholesterol using high-temperature conversion elemental analyser isotope-ratio mass spectrometry: determination of cholesterol absorption in normocholesterolemic volunteersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2004Jean-Philippe Godin This paper validates the use of high-temperature conversion elemental analyser isotope-ratio mass spectrometry (TC-EA/IRMS) for measuring the [2H/H] enrichment of plasma [2H5]cholesterol. From a molecular point of view, the free cholesterol is initially separated from plasma by thin-layer chromatography (TLC) and then injected onto the TC-EA reactor which converts cholesterol molecules into CO and H2 gases. The slope of the curve of the experimental mole percent excess (MPE(exp.)) versus MPE(theor.) was very close to 1, demonstrating that no significant isotopic fractionation was observed during all processing of the samples (i.e., isolation of plasma free cholesterol by TLC and pyrolysis in the TC-EA reactor). Excellent linearity (r2,=,0.9994, n,=,4) of , (,) of [2H/H] isotopic measurements versus mole percent (MP) was assessed over the range 0 to 0.1 MP. The precision of the [2H/H] measurement, evaluated with two calibration points processed with TLC, was ,2HV-SMOW,=,,192.5,±,3.4, and ,2HV-SMOW,=,,136.9,±,2.9,. The standard deviations of the within-assay and between-assay repeatabilities of the analytical process, evaluated using the quality control (QC) of plasma samples, were 4.6 and 6.1,, respectively. Plant sterols are known to reduce cholesterol absorption and therefore were used as a positive control in a clinical study performed with normocholesterolemic volunteers. This present method produces biological results consistent with those already reported in the literature. Copyright © 2004 John Wiley & Sons, Ltd. [source] Analysis of neuroactive amino acids from microdialysate samples by fluorescence detection using a modification of the 6-aminoquinolyl- N -hydroxysuccinimidyl carbamate methodBIOMEDICAL CHROMATOGRAPHY, Issue 10 2005M. Teresa Oreiro-García Abstract A sensitive and rapid reversed-phase high-performance liquid chromatographic method using pre-column derivatization with 6-aminoquinolyl- N -hydroxysuccinimidyl carbamate (AQC) and fluorescence detection is reported. By directly derivatizing microdialysate samples with AQC, an automatic and rapid simultaneous measurement of aspartate, serine, glutamate, glycine and histidine was developed. Excellent linearity (r2 , 0.998) was achieved for the standard mixture used for the validation experiments. Within-day and between-day precision was less than 6.2%, and the accuracy ranged from 95 to 105.2% in standards. This method is suitable for single run analysis of a high number of small volume microdialysate samples from rat hippocampus. Amino acids from microdialysate samples were quantified with RSD for reproducibility below 2%, and at approximately 0.1% for retention time. Copyright © 2005 John Wiley & Sons, Ltd. [source] Quantification and characterization of subvisible proteinaceous particles in opalescent mAb Formulations Using Micro-Flow ImagingJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2010Deepak K. Sharma Abstract Micro-flow imaging (MFIÔ) has been shown to be more sensitive than light obscuration (LO) methods for measuring subvisible proteinaceous particles in protein formulations. Given the potential challenges in detecting particulates in opalescent mAb formulations, the accuracy of MFI to size and count particles in opalescent solutions was investigated and compared to LO and membrane microscopy methods. Proteinaceous monoclonal antibody (mAb) particles, generated either by chemical denaturation or agitation stress, polystyrene and glass particles were used as model systems for measurements in opalescent mAb solutions. The sizing and counting accuracies of MFI were unaffected by the opalescence of the medium. Using glass particles as a model system for proteinaceous particles, MFI was able to detect relatively low particle concentrations (,10/mL) in opalescent solutions. MFI showed excellent linearity (R2,=,0.9969) for quantifying proteinaceous particles in opalescent solutions over a wide range of particle concentrations (,20,160,000/mL). Analyses of MFI particle image intensities revealed significant differences in the transparency of proteinaceous particles as a function of their size and mode of generation. LO method significantly underestimated proteinaceous particles, particularly those in the 2,10,µm size range. The less opaque proteinaceous particles were relatively more underestimated by the LO method in opalescent solutions. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2628,2642, 2010 [source] Monitoring of mutarotation of monosaccharides by hydrophilic interaction chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2010í Pazourek Abstract Calibration based on the "single-point calibration method", a simple exponential transformation of the response function of an evaporative light scattering detector was improved and applied to analysis of selected saccharides under hydrophilic interaction chromatography mode (a polar phase LiChrospher100 DIOL, mobile phase acetonitrile/water). The improved approach to the calibration procedure yielded a calibration curve with an excellent linearity (quality coefficient <5%). This quantitative evaluation of chromatograms of D -galactose suggested that not only anomers but even pyranose and furanose forms of the anomers could be resolved , the resulting calculations of abundance of the anomeric form strongly correlated with data from the literature obtained mostly by NMR studies (analogous results were also obtained for D -arabinose, D -glucose, and D -mannose). Because of the rapid separation (retention time less than 10,min), the observed correlation enabled to monitor anomeric conversion (mutarotation) of monosaccharides. [source] A 38-dBm power amplifier using AlGaAs/lnGaAs/GaAs PHEMT for S-band applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2005Hong-Zhi Liu Abstract A high-performance S-band power amplifier fabricated on a low-cost 20-mil-thick FR-4 printed circuit board (PCB) for S-band radar applications is demonstrated. The amplifier consists of a single-ended driver stage and a balanced output power stage utilizing Wilkinson power dividers/combiners with quarter-wave transmission lines. Under 10-V and 2.45-A dc bias condition, the S-band power amplifier with 23-dB small-signal gain, 38-dBm 1-dB gain-compression power with 25.6% power-added efficiency (PAE) and 3.9-dB noise figure can be achieved. In addition, excellent linearity with a 48.73-dBm 3rd -order intercept point is also measured. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 311,313, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20620 [source] Determination of lead content in medicinal plants by pre-concentration flow injection analysis,flame atomic absorption spectrometryPHYTOCHEMICAL ANALYSIS, Issue 6 2009Marina M. A. Campos Abstract Introduction , Although medicinal plants are widely used throughout the world, few studies have been carried out concerning the levels of heavy metal contaminants present. Such metals are highly toxic to living organisms even in low concentrations owing to their cumulative effect. The present paper describes the the development of a pre-concentration flow injection analysis-flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level. Objective , To develop a pre-concentration flow injection analysis-flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level. Methodology , A pre-concentration flow system was coupled to a flame atomic absorption spectrometer. The plant samples were analysed after nitroperchloric digestion. The proposed system was optimised by evaluating the following parameters: nature, concentration and volume of the eluent solution, elution flow rate, elution efficiency, pre-concentration flow rate and pre-concentration time. Results , The proposed system exhibited good performance with high precision and repeatability (RSD , 2.36%), excellent linearity (r = 0.9999), low sample consumption (10.5 mL per determination) and an analytical throughput of 55 samples/h. Lead concentrations ranged from 3.37 ± 0.25 to 7.03 ± 0.51 ,g/g in dry material. This concentration interval is greater than that previously published in the literature. Conclusion , The inclusion of a pre-concentration column in the flow manifold improved the sensitivity of the spectrometer. Thus, it was possible to determine the analyte at the ng/mL level in sample solutions of medicinal plants. This is a very important accomplishment, especially when the cumulative effect of heavy metals in living organisms is considered. Copyright © 2009 John Wiley & Sons, Ltd. [source] Simultaneous determination of ten antihistamine drugs in human plasma using pipette tip solid-phase extraction and gas chromatography/mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2006Chika Hasegawa Ten antihistamine drugs, diphenhydramine, orphenadrine, chlorpheniramine, diphenylpyraline, triprolidine, promethazine, homochlorcyclizine, cyproheptadine, cloperastine and clemastine, have been found to be extractable from human plasma samples using MonoTip C18 tips, inside which C18 -bonded monolithic silica gel was fixed. Human plasma (0.1,mL) containing the ten antihistamines was mixed with 0.4,mL of distilled water and 25,µL of a 1,M potassium phosphate buffer (pH 8.0). After centrifugation of the mixture, the supernatant fraction was extracted to the C18 phase of the tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C18 phase were then eluted with methanol by five repeated aspirating/dispensing cycles. The eluate was injected into a gas chromatography (GC) injector without evaporation and reconstitution steps, and was detected by a mass spectrometer with selected ion monitoring in the positive-ion electron impact mode. The separation of the ten drugs from each other and from impurities was generally satisfactory using a DB-1MS column (30,m,×,0.32,mm i.d., film thickness 0.25,µm). The recoveries of the ten antihistamines spiked into plasma were 73.8,105%. The regression equations for the ten antihistamines showed excellent linearity with detection limits of 0.02,5.0,ng/0.1,mL. The within-day and day-to-day coefficients of variation for plasma were not greater than 9.9%. The data obtained from determination of diphenhydramine and chlorpheniramine in human plasma after oral administration of the drugs are also presented. Copyright © 2006 John Wiley & Sons, Ltd. 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