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Satisfactory Repeatability (satisfactory + repeatability)
Selected AbstractsMicrofluidic chip-capillary electrophoresis for two orders extension of adjustable upper working range for profiling of inorganic and organic anions in urineELECTROPHORESIS, Issue 18 2010Wen Peng Guo Abstract To meet the need for onsite monitoring of urine anions, a microfluidic chip-capillary electrophoresis device was designed, fabricated and tested to extend the upper CE working range for an enhancement up to 500 fold (100 fold for sample dilution and 5 folds for CE injection) in order to analyze highly variable anionic metabolites in urine samples. Capillaries were embedded between two PMMA plates with laser-fabricated microchannel patterns to produce the microfluidic chip-capillary electrophoresis to perform standard/sample dilution and CE injection with adjustable dilution ratios. A circular ferrofluid valve was incorporated on-chip to perform cleanup and conditioning, mixing and dilution, injection and CE separation. Under optimized conditions, a complete assay for four samples can be achieved within an hour for 15 anions commonly found in urines. Satisfactory working ranges (0.005,500,mM) and low detection limits (0.5,6.5,,M based on S/N =2) are obtained with satisfactory repeatability (RSD, n=5) 0.52,0.87% and 4.1,6.5% for migration time and peak area, respectively. The working ranges with two orders adjustable upper extension are adequate to cover all analytes concentrations commonly found in human urine samples. The device fabricated shows sufficiently large experimentally verifiable enhancement factor to meet the application requirements. Its reliability was established by more than 94% recoveries of spiked standards and agreeable results from parallel method comparison with conventional ion chromatography method. The extension of the upper CE working range enables flexible onsite dilution on demand, a quick turn-around of results, and a low-cost device suitable for bedside monitoring of patients under critical conditions for metabolic disorders. [source] Through oven transfer adsorption,desorption interface for the analysis of methyl jasmonate in aromatic samples by on-line RPLC-GCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2008Gema Flores Abstract A fully automated method for the determination of medium volatility compounds in aromatic samples was developed. Specifically, the determination of methyl jasmonate in jasmine fragrances was performed by using the through oven transfer adsorption,desorption (TOTAD) interface for the on-line coupling between RPLC-GC. A study of the most relevant variables involved in the performance of the TOTAD interface for medium volatility compounds was carried out by testing different values of helium flow (100, 300, 400, and 500 mL/min), transfer speed (0.1, 0.3, 0.5, and 2.0 mL/min), and methanol/water percentages (86:14, 85:15, 83:17, 80:20, and 70:30). The method developed provided satisfactory repeatability (RSD for retention times of 0.15% and for peak areas of 9.4%) and recovery (71%) as well as excellent LOD (0.01 mg/L) for methyl jasmonate in commercial jasmine essence under the experimental conditions selected as optimum. Additional advantages of the automated RPLC-TOTAD-GC method proposed in the present work are its rapidness, reliability, and the possibility of directly introducing the sample with no further pretreatment. [source] On-line concentration by field-enhanced sample injection with reverse migrating micelles in micellar electrokinetic capillary chromatography for the analysis of coumarins from traditional Chinese medicine and human serumBIOMEDICAL CHROMATOGRAPHY, Issue 6 2010Ting-Fu Jiang Abstract In this work, a simple, reproducible and sensitive micellar electrokinetic chromatography method was developed for the separation and determination of three coumarins, imperatorin (IM), isoimperatorin (IO) and osthole (OS) from traditional Chinese medicine and human serum. Field-enhanced sample injection with reverse migrating micelles was used for on-line concentration of the coumarins. The optimum buffer contained 50,mM H3PO4, 160,mM sodium dodecyl sulfate, 20% acetonitrile and 15% 2-propanol, and the pH of buffer was 2.0. The sample solution was diluted with water containing 5,mM sodium dodecyl sulfate and injected for 15,s with ,8,kV after injection of 2,s water plug. The effects of concentrations of sodium dodecyl sulfate and organic modifier, the sample matrix, the injection time of water plug, the injection voltage and injection time of sample on the separation and stacking efficiency were investigated. Under the optimum conditions, the analytes were well separated and by optimizing the stacking conditions, about 93, 195 and 136 fold improvement in the detection sensitivity was obtained for IM, IO and OS. The contents of three coumarins in Angelica dahurica Benth, Radix Angelicae Pubescentis and Fructus Cnidii were successfully determined with satisfactory repeatability and recovery. The possibilities of using this method for the determination of three coumarins in spiked human serum were also tested. Copyright © 2009 John Wiley & Sons, Ltd. [source] Separation and determination of isoflavones in red clover by micellar electrokinetic capillary chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 9 2007Yu Zhang Abstract A micellar electrokinetic capillary chromatography (MECC) method has been developed for the determination of the four isoflavones, i.e. biochanin A, formononetin, genstein and daidzein in red clover (Trifolium Pratense L.). The effect of running buffer pH and concentration were investigated. An electrolyte composed of 30 mm borate, 20 mm sodium dodecyl sulfate (SDS) and 4 mg/mL HP- , -CD containing 5% (v/v) ethanol at pH 10.1 provides a satisfactory separation for all the analytes. The applied voltage was 25 kV, and the capillary temperature was kept constant at 25°C with a UV detection at 254 nm. The relative standard deviations (RSD) of the migration time and peak area were less than 1.73 and 3.94% (intra-day), and 2.29 and 4.38% (inter-day), respectively, under the optimized separation conditions. Regression equations revealed a good linear relationship between the peak area of each compound and its concentration. The contents of the four compounds in red clover were successfully determined with satisfactory repeatability and recovery. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||