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Linear Dynamic Range (linear + dynamic_range)
Selected AbstractsElectrodeposited Silver Nanoparticles on Carbon Ionic Liquid Electrode for Electrocatalytic Sensing of Hydrogen PeroxideELECTROANALYSIS, Issue 13 2009Afsaneh Safavi Abstract Silver nanoparticles (narrowly dispersed in diameter) were electrodeposited on carbon ionic liquid electrode (CILE) surface using a two-step potentiostatic method. Potentiostatic double pulse technique was used as a suitable and simple method for controlling the size and morphologies of silver nanoparticles electrodeposited on CILE. The obtained silver nanoparticles deposited on CILE surface showed excellent electrocatalytic activity (low overpotential of ,0.35,V vs. Ag/AgCl) towards reduction of hydrogen peroxide. A linear dynamic range of 2,200,,M with an experimental detection limit of 0.7,,M (S/N=3) and reproducibility of 4.1% (n=5) make the constructed sensor suitable for peroxide determination in aqueous solutions. [source] Carbon Ceramic Electrodes Modified with Laccase from Trametes hirsuta: Fabrication, Characterization and Their Use for Phenolic Compounds DetectionELECTROANALYSIS, Issue 9 2007Behzad Haghighi Abstract Fungal laccase (Lc) from the basidiomycete Trametes hirsuta was immobilized on top of a carbon ceramic electrode using physical absorption. Direct, unmediated heterogeneous electron transfer between Lc and the carbon ceramic electrode (CCE) under aerobic conditions was shown. The bioelectrocatalytic reduction of oxygen on Lc-CCE started at about 430,mV vs. Ag|AgCl|KClsat at pH,3.5 and moved with about 57,mV in the cathodic region per pH unit. The Lc-modified CCE was then used as a biosensing detection element in a single line flow injection system for the amperometric determination of a variety of phenolic substrates of the enzyme. The experimental conditions were studied and optimized for catechol serving as a model compound. Statistical aspects were applied and the sensor characteristics and Michaelis-Menten constants of the investigated phenolic compounds were calculated and compared with those obtained for solid graphite electrodes modified with Trametes hirsuta laccase. The results showed that the CCE based biosensor in comparison with the solid graphite based biosensor offers a lower detection limit, a wider linear dynamic range, and excellent operational stability with no sensor passivation, indicating that the sol,gel lattice improves the electrochemical behavior of the biosensor. [source] Simultaneous Determination of Uric Acid and Ascorbic Acid Using Edge Plane Pyrolytic Graphite ElectrodesELECTROANALYSIS, Issue 8 2006Roohollah, Torabi Kachoosangi Abstract Edge plane pyrolytic graphite electrodes have been applied for the determination of uric acid and ascorbic acid. The separate determination of uric acid was found to produce three linear ranges from 100,nM to 3400,,M with a detection limit of 30,nM found to be possible. Uric acid detection was also explored in the presence of 200,,M ascorbic acid where a detection limit of 52,nM was found to be possible. The detection of ascorbic acid in the presence of uric acid was also explored over three linear ranges of ascorbic acid with a limit of detection of 80,nM. Last the simultaneous determination of both uric acid and ascorbic acid is investigated over the range 100,nM to 1000,,M where detection limits of 50,nM and 120,nM were obtained respectively. Analysis of uric acid in a growth tissue medium was found to be successful, confirming the applicability of the methodology to real matrices. This protocol is shown to provide low detection limits, easy handling (no electrode modification), good voltammetric peak separation of uric acid and ascorbic acid and a wide linear dynamic range. [source] Analysis of major alkaloids in Rhizoma coptidis by capillary electrophoresis-electrospray-time of flight mass spectrometry with different background electrolytesELECTROPHORESIS, Issue 10 2008Junhui Chen Abstract CE-based techniques with DAD and detection ESI-TOF-MS have been developed for the analysis of seven protoberberine alkaloids and one aporphinoid alkaloid in Huanglian (Rhizoma coptidis), a well-known traditional Chinese herbal medicine. One aqueous BGE and one nonaqueous BGE were developed for CE-DAD and CE-MS analyses, and the CE-ESI-TOF-MS conditions including nebulizer gas pressure, the sheath-liquid composition, its flow rate, etc. were optimized. Eight main alkaloids in R. coptidis could be separated with baseline resolution by CE-DAD with these two different BGEs, and identified by TOF-MS analysis. Moreover, three major alkaloids (berberine, palmatine, and jatrorrhizine) could be quantified accurately by CE-DAD and CE-MS with the BGE system consisting of 50:50 v/v water and ACN containing 50,mM ammonium acetate at pH,6.8. Both techniques provided similar LODs and could be applied with confidence within similar linear dynamic range. However, reproducibility and speed of analysis were better using CE-DAD. When the CE technique was compared with the RP-HPLC method, the CE-DAD and CE-MS methods provided greater efficiency and faster analysis speed, i.e., achieving baseline resolution for all the eight main basic compounds in less than 14,min. The CE method, as a viable alternative to HPLC, is suitable for use as a routine procedure for the rapid identification and quantification of basic compounds in herbal or natural product applications. [source] Semiquantitative determination of Alicyclobacillus acidoterrestris in orange juice by reverse- transcriptase polymerase chain reaction and capillary electrophoresis , laser induced fluorescence using microchip technologyELECTROPHORESIS, Issue 21-22 2004Maribel Funes-Huacca Abstract The semiquantitative detection of Alicyclobacillus acidoterrrestris in orange juice by reverse-transcriptase polymerase chain reaction (RT-PCR) with a linear dynamic range of 2×105, 2 colony forming units (CFU)/mL in terms of cell count is described. Separation, detection, and quantification of the RT-PCR products were accomplished using the Agilent 2100 bioanalyzer in conjunction with the DNA 1000 LabChip kit. After 0 and 12 h of enrichment, it was possible to generate a linear standard curve between the amount of cells and amplicon concentration of RT-PCR and PCR products. Using this method, cell diminution was verified in samples of orange juice treated with a natural inhibitor (Sapindus saponaria), determining the persistence of viable cells. Semiquantitative RT-PCR using the Agilent 2100 bioanalyzer is a potentially useful approach for rapid in vitro determination of A. acidoterrestris and monitoring of inhibitor susceptibility for the orange juice-producing industry. [source] LC,ESI-MS/MS analysis for the quantification of morphine, codeine, morphine-3-,- D -glucuronide, morphine-6-,- D -glucuronide, and codeine-6-,- D -glucuronide in human urineJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2005Constance M. Murphy Abstract A liquid chromatographic-electrospray ionization-tandem mass spectrometric method for the quantification of the opiates morphine, codeine, and their metabolites morphine-3-,- D -glucuronide (M-3-G), morphine-6-,- D -glucuronide (M-6-G) and codeine-6-,- D -glucuronide (C-6-G) in human urine has been developed and validated. Identification and quantification were based on the following transitions: 286 to 201 and 229 for morphine, 300 to 215 and 243 for codeine, 644 to 468 for M-3-G, 462 to 286 for M-6-G, and 476 to 300 for C-6-G. Calibration by linear regression analysis utilized deuterated internal standards and a weighting factor of 1/X. The method was accurate and precise across a linear dynamic range of 25.0 to 4000.0 ng/ml. Pretreatment of urine specimens using solid phase extraction was sufficient to limit matrix suppression to less than 40% for all five analytes. The method proved to be suitable for the quantification of morphine, codeine, and their metabolites in urine specimens collected from opioid-dependent participants enrolled in a methadone maintenance program. Copyright © 2005 John Wiley & Sons, Ltd. [source] Rapid simultaneous determination of codeine and morphine in plasma using LC-ESI-MS/MS: Application to a clinical pharmacokinetic studyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 2 2009Qiongfeng Liao Abstract A rapid and sensitive high-performance LC-MS/MS method was developed and validated for the simultaneous quantification of codeine and its metabolite morphine in human plasma using donepezil as an internal standard (IS). Following a single liquid-liquid extraction with ethyl acetate, the analytes were separated using an isocratic mobile phase on a C18 column and analyzed by MS/MS in the selected reaction monitoring mode using the respective [M+H]+ ions, mass-to-charge ratio (m/z) 300/165 for codeine, m/z 286/165 for morphine and m/z 380/91 for IS. The method exhibited a linear dynamic range of 0.2,100/0.5,250 ng/mL for codeine/morphine in human plasma, respectively. The lower LOQs were 0.2 and 0.5 ng/mL for codeine and its metabolite morphine using 0.5 mL of human plasma. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated LC-MS/MS method was applied to a pharmacokinetic study in which healthy Chinese volunteers each received a single oral dose of 30 mg codeine phosphate. [source] A novel [Ag(NH3)2]+ probe for chemiluminescent imaging detection of proteins after polyacrylamide gel electrophoresisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 15 2007Xin Xiong Abstract The development of a novel [Ag(NH3)2]+ probe chemiluminescence (CL)-based imaging method for the detection of various proteins after PAGE is described. The detection is based upon the probe [Ag(NH3)2]+ catalyzing the CL reaction of the luminol,potassium persulfate system. The proposed method detects various proteins labeled by [Ag(NH3)2]+ and expands the application scope to SDS gels. It also detects proteins directly in polyacrylamide gels, without tedious transferring procedures. Furthermore, successful identification of proteins by peptide mass profiling using ionization MS was easily performed, and no pretreatments of gel prior to digestion are needed. Detection limits for standard marker proteins match CBB-R250 staining and the linear dynamic range is superior to CBB-R250 staining and silver staining. The CL imaging conditions, including luminescent reagents, silver ion concentration, the ammonia-controlled system and the washing reagents parameters have also been optimized. [source] Atmospheric pressure desorption/ionization on silicon ion trap mass spectrometry applied to the quantitation of midazolam in rat plasma and determination of midazolam 1,-hydroxylation kinetics in human liver microsomesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006Rick C. Steenwyk The application of atmospheric pressure desorption/ionization on silicon (AP-DIOS) coupled with ion trap mass spectrometry (ITMS) was investigated for the quantification of midazolam in rat plasma, and determination of midazolam 1,-hydroxylation kinetics in pooled human liver microsomes. Results indicate good sensitivity with absolute detection limits for midazolam in rat plasma of approximately 300 femtograms. A linear dynamic range from approximately 10,5000,ng/mL was obtained in rat plasma with analysis times of 1,min per sample. Kinetic constants for midazolam 1,-hydroxylation in human liver microsomes yielded an apparent Km of 10.0,µM and Vmax of 6.4,nmol/min/mg. Studies investigating the inhibition of 1,-hydroxymidazolam formation by the cytochrome P450 3A4 model inhibitor ketoconazole yielded an IC50 of 0.03,µM. Quantitative precision for replicate analysis of rat plasma and human liver microsomal samples was variable with relative standard deviation (RSD) values ranging from a low of approximately 3% to over 50%, with the highest variability observed in data from human liver microsomal incubations. While preliminary studies investigating the application of AP-DIOS-ITMS suggested feasibility of this technique to typical pharmacokinetic applications, further work is required to understand the underlying causes for the high variability observed in these investigations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous quantification of a non-nucleoside reverse transcriptase inhibitor efavirenz, a nucleoside reverse transcriptase inhibitor emtricitabine and a nucleotide reverse transcriptase inhibitor tenofovir in plasma by liquid chromatography positive ion electrospray tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 4 2009Ramakrishna Nirogi Abstract A high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry method for the simultaneous quantification of efavirenz, emtricitabine and tenofovir was developed and validated with 100 µL human plasma. Following solid-phase extraction, the analytes were separated using a gradient mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H]+ ions, m/z 316 to 168 for efavirenz, m/z 248,130 for emtricitabine and m/z 288,176 for tenofovir, m/z 482,258 for rosuvastatin (IS), m/z 260,116 for propranolol (IS). The method exhibited a 100-fold linear dynamic range for all the three analytes in human plasma (20,2000, 2,200 and 20,2000 ng/mL for efavirenz, emtricitabine and tenofovir respectively). The lower limit of quantification was 2 ng/mL for emtricitabine and 20 ng/mL for both efavirenz and tenofovir with a relative standard deviation of less than 11%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time of 4 min for each sample made it possible to analyze more than 250 human plasma samples per day. The method is precise and sensitive enough for its intended purpose. The method is also successfully applied to quantify efavirenz, emtricitabine and tenofovir concentrations in a rodent pharmacokinetic study. Copyright © 2008 John Wiley & Sons, Ltd. [source] Sensitive liquid chromatography tandem mass spectrometry method for the quantification of sitagliptin, a DPP-4 inhibitor, in human plasma using liquid,liquid extractionBIOMEDICAL CHROMATOGRAPHY, Issue 2 2008Ramakrishna Nirogi Abstract A sensitive high-performance liquid chromatography,positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of sitagliptin, a DPP-4 inhibitor, in human plasma. Following liquid,liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H]+ ions, m/z 408,235 for sitagliptin and m/z 310,148 for the internal standard. The assay exhibited a linear dynamic range of 0.1,250 ng/mL for sitagliptin in human plasma. The lower limit of quantification was 0.1 ng/mL with a relative standard deviation of less than 6%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic studies. Copyright © 2007 John Wiley & Sons, Ltd. [source] Quantification of tenatoprazole in rat plasma by HPLC: validation and its application to pharmacokinetic studiesBIOMEDICAL CHROMATOGRAPHY, Issue 12 2007Ramakrishna Nirogi Abstract A simple, reliable HPLC method with UV detection (295 nm) in rat plasma was developed and validated for quantification of tenatoprazole, a novel proton pump inhibitor, which is in clinical trials. Following a single-step liquid,liquid extraction, the analyte and internal standard were separated using an isocratic mobile phase on a reverse phase C18 column. The lower limit of quantitation was 20 ng/mL, with a relative standard deviation of less than 10%. A linear dynamic range of 20,6000 ng/mL was established. This HPLC method was validated with between-batch and within-batch precision of 2.9,6.3 and 1.4,5.8%, respectively. The between-batch and within-batch accuracy was 95.1,104.1 and 92.4,101.0%, respectively. This validated method is simple and repeatable enough to be used in pharmacokinetic studies. Copyright © 2007 John Wiley & Sons, Ltd. [source] On-line automatic SPE-CE coupling for the determination of biological markers in urineELECTROPHORESIS, Issue 5 2007José Ruiz-Jiménez Abstract Automatic SPE has been coupled on-line to CE by a transfer tube and the replenishment system of the CE instrument. The approach allows the target analytes (viz. creatinine, creatine, xanthine, hypoxanthine, uric acid, p -aminohippuric acid and ascorbic acid in urine samples) to be removed from the sample matrix, cleaned up, preconcentrated and injected into the capillary. The detection limits range between 0.14 and 4.50,,g/mL, the quantification limits between 0.45 and 15.0,,g/mL, and linear dynamic ranges , which include the reference healthy human values , from the quantification limits to 1332,,g/mL. The precision, expressed as RSD, ranges between 0.38 and 2.22% for repeatability and between 1.79 and 7.61% for within-laboratory reproducibility. The errors, expressed as RSD for all compounds, range between 0.20 and 6.90%. The time for automatic SPE and that necessary for the individual separation,detection of the target analytes are 13 and 12,min, respectively; the analysis frequency is 5,h,1. The accuracy of the method and potential matrix effects were studied by using spiked samples and recoveries between 96.00 and 103.07 % were obtained. The proposed method was applied to samples from healthy young students. [source] | ||||||||||