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Sample Matrix (sample + matrix)
Selected AbstractsDirect on-line analysis of neutral analytes by dual sweeping via complexation and organic solvent field enhancement in nonionic MEKCELECTROPHORESIS, Issue 8 2009Jun Cao Abstract Conventionally, neutral compounds cannot be separated by nonionic micelle capillary electrophoresis. In this report, the development of a novel on-line preconcentration technique combining dual sweeping based on complexation and organic solvent field enhancement is applied to the sensitive and selective analysis of three neutral glucosides: ginsenoside Rf, ginsenoside Rg1, and ginsenoside Re. Nonionic micelle detectability by CE is demonstrated through effective focusing of large sample volumes (up to 38% capillary length) using a dual sweeping mode. This results in a 50- to 130-fold improvement in the LODs relative to conventional injection method. Neutral compounds sweeping is examined in terms of analyte mobility dependence on borate complexation, solvent viscosity difference, and Brij-35 interaction. Enhanced focusing performance by this hyphenated method was demonstrated by a greater than fourfold reduction in glucoside bandwidth, as compared with common sweeping (devoid of organic solvent-mediated sweeping method in the sample matrices). Moreover, separation efficiencies greater than a million theoretical plates can be achieved by sweeping large sample volumes into narrow zones. The designated method was also tested for its ability to determine the presence of glucosides in the crude extracts obtained from plant sample. [source] Pharmaceutical metabolites in the environment: Analytical challenges and ecological risks,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2009Mary D. Celiz Abstract The occurrence of human and veterinary pharmaceuticals in the environment has been a subject of concern for the past decade because many of these emerging contaminants have been shown to persist in soil and water. Although recent studies indicate that pharmaceutical contaminants can pose long-term ecological risks, many of the investigations regarding risk assessment have only considered the ecotoxicity of the parent drug, with very little attention given to the potential contributions that metabolites may have. The scarcity of available environmental data on the human metabolites excreted into the environment or the microbial metabolites formed during environmental biodegradation of pharmaceutical residues can be attributed to the difficulty in analyzing trace amounts of previously unknown compounds in complex sample matrices. However, with the advent of highly sensitive and powerful analytical instrumentations that have become available commercially, it is likely that an increased number of pharmaceutical metabolites will be identified and included in environmental risk assessment. The present study will present a critical review of available literature on pharmaceutical metabolites, primarily focusing on their analysis and toxicological significance. It is also intended to provide an overview on the recent advances in analytical tools and strategies to facilitate metabolite identification in environmental samples. This review aims to provide insight on what future directions might be taken to help scientists in this challenging task of enhancing the available data on the fate, behavior, and ecotoxicity of pharmaceutical metabolites in the environment. [source] Accounting for co-extractable compounds (blank correction) in spectrophotometric measurement of extractable and total-bound proanthocyanidin in Leucaena sppJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2002Scott A Dalzell Abstract Methods to account for the spectral interference of co-extractable compounds (blank correction) in the spectrophotometric analysis of both extractable and bound proanthocyanidin (PA) using the proanthocyanidin (butanol/HCl) assay were evaluated. Crude extractable and bound PA sample matrices of PA-free Leucaena magnifica were used. Extractable PA blanks generated in heated 95% butanol/5% H2O reagent underestimated the optical density (absorbance) of co-extractable compounds by 24% (P,<,0.01), whereas unheated 95% butanol/5% HCl blanks, incubated at room temperature, accurately measured the absorbance of the background matrix (P,<,0.01). Current procedures that estimate bound PA concentrations using the proanthocyanidin assay produce intensely coloured background matrices. Recovery measurements from total-bound PA extracts spiked with 1071 and 2142,µg anthocyanidin per tube indicated that existing analytical procedures that do not account for the spectral interference of co-extractable compounds overestimated (P,<,0.01) bound PA concentrations by 69 and 38% respectively. An innovative technique that generated an internal correction factor for each sample, using wavelength-scanning spectrophotometry and non-linear curve-fitting computer software, was developed. This procedure recovered 100% of added anthocyanidins from bound PA matrices. © 2002 Society of Chemical Industry [source] Report from a workshop on multianalyte microsphere assays,,§CYTOMETRY, Issue 5 2002Marie C. Earley Abstract Multiplexed assays using fluorescent microspheres is an exciting technique that has been gaining popularity among researchers, particularly those in the public health field. Part of its popularity is due to its flexibility, as both immunoassays and oligonucleotide hybridization assays can be developed on this platform. This report summarizes a workshop held by the Centers for Disease Control and Prevention that discussed issues surrounding these assays and the Luminex 100 xMAP instrument. Topics included instrumentation, assay design, sample matrix and volume, quality control, and development of commercial applications. Cytometry (Clin. Cytometry) 50:239,242, 2002. Published 2002 Wiley-Liss, Inc. [source] Heart-cutting 2D-CE with on-line preconcentration for the chiral analysis of native amino acidsELECTROPHORESIS, Issue 6 2010Suzanne Anouti Abstract The use of transient moving chemical reaction boundary (tMCRB) was investigated for the on-line preconcentration of native amino acids in heart-cutting 2D-CE with multiple detection points using contactless conductivity detection. The tMCRB focusing was obtained by using ammonium formate (pH 8.56) as sample matrix and acetic acid (pH 2.3) as a BGE in the first dimension of the heart-cutting 2D-CE. Different experimental parameters such as the injected volume and the concentration in ammonium formate were optimized for improving the sensitivity of detection. A stacked fraction from the first dimension was selected, isolated in the capillary, and then separated in the second dimension in the presence of a chiral selector ((+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid). This on-line tMCRB preconcentration coupled with heart-cutting 2D-CE was applied with success to the chiral separation of D,L -phenylalanine, and D,L -threonine in a mixture of 22 native amino acids. The sample mixture was diluted in 0.8,M of ammonium formate, and injected at a concentration of 2.5,,M for each enantiomer with a volume corresponding to 10% of the total capillary volume. An LOD (S/N=3) of 2,,M was determined for L -threonine. [source] Application of CE with novel dynamic coatings and field-amplified sample injection to the sensitive determination of isomeric benzoic acids in atmospheric aerosols and vehicular emissionELECTROPHORESIS, Issue 19 2007Ewa Dabek-Zlotorzynska Dr. Abstract A simple and reliable CE method with direct UV detection has been developed to separate eight isomeric benzoic acids in atmospheric aerosols and vehicular emission without complex sample pretreatment. Optimal electrophoretic conditions, with migration times under 5,min, were obtained by using a 50,mM acetate buffer (pH,4.7) containing a dynamic surface coating EOTrolÔ LN (0.005% w/v). The separations were carried out in a cathode to anode direction (,30,kV) allowing the low cathodal EOF (,1×10,9,m2V,1s,1) to extend the effective separation by slowing the movement of the studied aromatic acids. Moreover, the sensitivity of the method at 200,nm was enhanced by using a field-amplified sample injection (FASI) with electrokinetic (EK) sample injection (,2,kV, 60,s). Prior to sample injection, a short water plug (3,s at 0.5,psi) was introduced. Under these conditions, the method was capable of detecting the analytes in deionized water with LODs (S/N,=,3) as low as 0.1,,g/L for most of the studied acids. In the presence of 10,mg/L of sulphate (added to simulate a sample matrix), LODs ranged from 0.26 to 0.62,,g/L. The validation of the method has proven an excellent separation performance and accuracy for the determination of isomeric benzoic acids in the studied matrices. [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] Direct Current Plasma Emission Spectrometric Determination of Major, Minor and Trace Elements in Microwave Oven Acid Leachates of Powdered Whole Coal SamplesGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2005Sandro Fadda DCP-AES; échantillons de charbon; four à micro-ondes; éléments facilement ionisables; effets de matrice. Major concentrations of Al2O3, Fe2O3, MgO, CaO, Na2O and K2O, minor levels of TiO2, P2O5 and thirty petrologically, geochemically and environmentally significant trace elements have been determined in microwave oven acid leachates of whole powdered coal samples by direct current plasma-atomic emission spectrometry (DCP-AES). A single sample preparation procedure was suitable for all the determinations with no additional dilution step for major elements solution. Dried samples (0.5 g) were treated in low-pressure PFA digestion vessels with HF/HCl/HNO3/HClO4 acids to quantitatively extract the analytes from the bulk material, while leaving the major part of organic matrix as a residue. The major constituents of geological samples, in particular the easily ionised elements (EIEs) such as alkali and alkaline earths, may complicate the instrumental determinations in DCP-AES because of differential enhancements of elemental emission intensities and stray light interferences. Taking account of these factors, the coal matrix is considered to have very low major oxide totals as compared to many other common geo-environmental and related materials (rocks, sediments, soil, ashes etc.). The sample size employed here, while yielding a relatively concentrated solution to cover a wide range of elemental determinations, provided a sample matrix that significantly diminished interferences for DCP measurements. The need for closely matching the unknowns and calibrators was eliminated except for overall acidity and an excess quantity of caesium for EIE buffering. Calibration of the spectrometer was accomplished by simple aqueous single element solutions as high concentration calibrators in addition to a reagent blank as a low concentration calibrator. Two point working curves were established to allow for the maximum concentrations of each element expected in the unknowns. The precision of determinations under routine conditions as well as the reproducibility of the leaching and precision of instrumental measurements have been evaluated. Relative standard deviations (RSD) were of 1,2% for those elements whose concentrations in solid samples were well above the limits of quantification. Method detection limits in the buffered solutions were also evaluated. To evaluate the accuracy of the microwave oven-DCP method a suite of eight certified coal reference materials of differing rank, were analysed with good agreement with the certified and/or available published data. Results are presented for the uncertified major oxides in the AR series reference materials. Les concentrations en éléments majeurs: Al2O3, Fe2O3, MgO, CaO, Na2O et K2O, en éléments mineurs TiO2, P2O5 et en 30 éléments en trace dont le comportement est important en Pétrologie, en Géochimie et en Environnement, ont été analysées par spectrométrie d'émission atomique à plasma à courant direct (DCP-AES), dans des lessivages acides effectués dans un four à micro-ondes sur des échantillons de charbon mis en poudre. Ce mode préparatoire unique est adaptéà toutes les déterminations sans qu'il soit nécessaire d'effectuer une dilution supplémentaire pour l'analyse des éléments majeurs. Les échantillons préalablement desséchés (0.5 g) sont traités dans les pots de PFA de basse pression, avec un mélange d'acides HF/HCl/HNO3/HClO4, afin d'extraire quantitativement les analytes du matériel géologique, tout en laissant la plus grande part de la matrice organique sous forme résiduelle. Les constituants majeurs de ces échantillons géologiques, en particulier les éléments facilement ionisables (EIEs) tels que les alcalins et les alcalino-terreux, peuvent compliquer l'analyse en DCP-AES à cause des rendements variables des intensités d'émission élémentaires et des interférences de raies de lumière. Mais là dessus, la matrice de charbon se révèle être bien plus pauvre en oxydes majeurs que les autres matériaux géologiques, environnementaux ou de type proche (roches, sédiments, sols, cendres). La taille d'échantillon retenue ici, tout en fournissant une solution relativement concentrée qui permet la détermination de beaucoup d'éléments, fournit une matrice qui diminue significativement les interférences lors de la mesure par DCP-AES. Le besoin d'avoir les solutions d'échantillons et les solutions de calibration avec des matrices très proches est donc éliminé, mis à part pour l'acidité totale et la quantité excessive de Césium pour tamponner les EIE. La calibration du spectromètre est faite avec des solutions mono- élémentaires aqueuses, pour déterminer les points de concentrations élevées et avec le blanc de réactifs pour le point de concentration basse. Les courbes de calibrations sont déterminées avec 2 points, pour autoriser l'analyse de concentrations maximales pour chaque élément dans les échantillons inconnus. La précision des déterminations en conditions de routine ainsi que la reproductibilité de l'opération de lessivage et la précision instrumentale des analyses ont étéévaluées. Les déviations standards relatives (RSD) sont de 1,2% pour tout élément dont les concentrations dans le solide sont au dessus des limites de quantification. Les limites de détection de la méthode dans les solutions tamponnées ont aussi étéévaluées. Enfin, pour évaluer la justesse de cette méthode "micro-ondes - DCP" huit charbons certifiés matériaux de référence de différents types ont été analysés, et sont en bon accord avec les données certifiées ou seulement disponibles publiées. Les données sur un certain nombre d'oxydes d'éléments majeurs actuellement non certifiés sont présentées pour les matériaux de référence AR. [source] The differentiation of biodegradable and non-biodegradable dissolved organic matter in wastewaters using fluorescence spectroscopyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002M Reynolds Abstract The chemical and biochemical oxygen demand values of a number of synthetic and wastewater samples were determined using fluorescence spectroscopy. Treated and untreated sewage samples were obtained from a local sewage treatment works while synthetic samples were analysed before, during, and after treatment via a rotating biodisc contactor. Fluorescence intensities were normalised using the water Raman signal as an internal standard and corrections applied to take into account the attenuation effects caused by the sample matrix. The fluorescence emission spectra (,exc,=,280,nm) of synthetic and sewage samples were very similar in that two main fluorescence bands centred around 350,nm and 440,nm were observed in all samples. Normalised fluorescence data, centred at 350,nm, correlate well with corresponding BOD, COD and TOC values (R2 values ranging between 0.93 and 0.98). Using BOD, COD and TOC data the fluorescence at 350,nm and 440,nm can be apportioned to biodegradable and non-biodegradable dissolved organic matter respectively. The findings of this research show that fluorescence data can be used to quantify oxygen demand values (chemical and biochemical) and total organic carbon values. Furthermore, the fluorescence spectral response can be apportioned to biodegradable (BOD) and non-biodegradable (COD,,,BOD) dissolved organic matter. The potential of using fluorescence spectroscopy as a possible tool for real-time monitoring of sewage wastes is discussed. © 2002 Society of Chemical Industry [source] Matrix effects on accurate mass measurements of low-molecular weight compounds using liquid chromatography-electrospray-quadrupole time-of-flight mass spectrometry,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2006F. Calbiani Abstract Liquid chromatography (LC) with high-resolution mass spectrometry (HRMS) represents a powerful technique for the identification and/or confirmation of small molecules, i.e. drugs, metabolites or contaminants, in different matrices. However, reliability of analyte identification by HRMS is being challenged by the uncertainty that affects the exact mass measurement. This parameter, characterized by accuracy and precision, is influenced by sample matrix and interferent compounds so that questions about how to develop and validate reliable LC-HRMS-based methods are being raised. Experimental approaches for studying the effects of various key factors influencing mass accuracy on low-molecular weight compounds (MW < 150 Da) when using a quadrupole-time-of-flight (QTOF) mass analyzer were described. Biogenic amines in human plasma were considered for the purpose and the effects of peak shape, ion abundance, resolution and data processing on accurate mass measurements of the analytes were evaluated. In addition, the influence of the matrix on the uncertainty associated with their identification and quantitation is discussed. A critical evaluation on the calculation of the limits of detection was carried out, considering the uncertainty associated with exact mass measurement of HRMS-based methods. The minimum concentration level of the analytes that was able to provide a statistical error lower than 5 ppm in terms of precision was 10 times higher than those calculated with S/N = 3, thus suggesting the importance of considering both components of exact mass measurement uncertainty in the evaluation of the limit of detection. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simple and rapid extraction, separation, and detection of alkaloids in beveragesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 21 2008Christine L. Copper Abstract Implementation of an uncomplicated SPE process for the rapid extraction and preconcentration of the alkaloids, colchicine, strychnine, aconitine, and nicotine, from water, apple juice, and nonfat milk samples is presented. When coupled to analysis via micellar EKC (MEKC), the total analysis time per sample was less than 15 min for the water and juice samples and less than 20 min for the milk. The SPE process allowed for anywhere from a three to a fourteen-fold improvement in the LOD for each alkaloid when compared to detecting the alkaloids in a nontreated water sample matrix. Following SPE, the LODs for colchicine, strychnine, and nicotine were sufficient to meet levels from 150 to 5000 times more dilute than the LD50 for a 50 kg individual drinking 12 oz of a contaminated beverage. Aconitine, on the other hand, was detected at approximately the LD50 level. The percent recoveries for the SPE ranged from 37% to as high as 99%. Nicotine attained the highest recovery efficiencies, followed by colchicine, and finally, aconitine and strychnine, which were nearly identical. The greatest recovery efficiencies were achieved from apple juice and water, whereas nonfat milk yielded the lowest. [source] Determination of some hydroxybenzoic acids and catechins in white wine samples by liquid chromatography with luminescence detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2006Rafael Carlos Rodríguez-Díaz Abstract A liquid chromatographic method with luminescence detection for the determination of eight phenolic compounds is reported. The method involves postcolumn derivatization with terbium(III). This derivatization is based on the reaction between phenolics and terbium(III) to form luminescent chelates, which were determined at ,ex 295 and ,em 545 nm using the fluorescence mode. The long wavelength emission of lanthanide chelates can minimize interferences from background sample matrix, which usually emit at shorter wavelengths. Also, the chromatographic separation allows the individual determination of phenolics, which cannot be done using the direct measurement of the fluorescence of their corresponding terbium chelates. Dynamic ranges of the calibration graphs and detection limits, obtained with standard solutions of analytes were (,g/mL): gallic acid (0.9,40, 0.3), protocatechuic acid (0.05,7, 0.016), catechin (0.2,40, 0.07), vanillic acid (0.25,40, 0.08), p -hydroxybenzoic acid (0.8,40, 0.25), syringic acid (0.17,40, 0.05), epicatechin (0.3,40, 0.09) and salicylic acid (0.07,12, 0.02). The precision was established at two concentration levels of each analyte and expressed as the percentage of RSD with values ranging between 1.0 and 6.5%. The practical usefulness of the method was demonstrated by the analysis of white wine samples, which were diluted two-fold and directly injected into the chromatographic system. The recovery values obtained ranged between 93.3 and 108.0%. [source] Comparison of two capillary electrophoresis online stacking modes by analysis of polycyclic aromatic hydrocarbons in airborne particulatesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2006Guan-Qun Song Abstract Naphthalene, fluorene, pyrene, anthracene, phenanthrene, and chrysene were successfully separated by CD-modified MEKC (CD-MEKC) using 20 mM borate (pH 9.0) containing 90 mM SDS and 75 mM ,-CD. Two online stacking methods, i. e., sweeping and field-enhanced sample injection (FESI), were explored to enhance the detection sensitivity. The influences of some crucial parameters in sweeping and FESI procedures were investigated. For FESI method, a plug of water and low-conductivity sample matrix was used to increase the stacking efficiency. Compared with the sweeping method, FESI can increase the sensitivity in the range of 10,20-fold. The proposed method was used for the analysis of polycyclic aromatic hydrocarbons in airborne particulates. [source] Environmental analysis by inductively coupled plasma mass spectrometryMASS SPECTROMETRY REVIEWS, Issue 4 2010Diane Beauchemin Abstract This article reviews the numerous ways in which inductively coupled plasma mass spectrometry has been used for the analysis of environmental samples since it was commercially introduced in 1983. Its multielemental isotopic capability, high sensitivity and wide linear dynamic range makes it ideally suited for environmental analysis. Provided that some care is taken during sample preparation and that appropriate calibration strategies are used to circumvent non-spectroscopic interferences, the technique is readily applicable to the analysis of a wide variety of environmental samples (natural waters, soils, rocks, sediments, vegetation, etc.), using quadrupole, time-of-flight or double-focusing sector-field mass spectrometers. In cases where spectroscopic interferences arising from the sample matrix cannot be resolved, then separation methods can be implemented either on- or off-line, which can simultaneously allow analyte preconcentration, thus further decreasing the already low detection limits that are achievable. In most cases, the blank, prepared by following the same steps as for the sample but without the sample, limits the ultimate detection limits that can be reached. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:560,592, 2010 [source] On-line preconcentration and quantitative analysis of peptide hormone of brain and intestine using on-column transient isotachophoresis coupled with capillary electrophoresis/electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008Shifei Xia A new approach was described to achieve very sensitive analysis of peptide hormone of brain and intestine by capillary electrophoresis coupled with a transient isotachophoresis (tITP) preconcentration method. The system used was electrospray ionization mass spectrometry (ESI-MS) as detector and equipped with a sheath flow configuration. The effects of sample matrix, pH and concentration of leading electrolyte (LE), sample injection time, and ESI-MS instrumental parameters on the efficiency of the sample stacking were investigated in detail. Under the optimized conditions, lower than micromole (0.01,µM) concentrations of the peptides were easily detected. Compared to traditional hydrodynamic injection methods, about 40,230-fold increase in detection sensitivity was obtained by this technique. A distinguishing feature of the described approach is that the background electrolyte can serve as terminating electrolyte (TE), which simplifies the process of the experiments. The method was further evaluated by the analysis of low concentration active peptide mixtures spiked in hypothalamus tissue of the rat. Copyright © 2008 John Wiley & Sons, Ltd. [source] A direct injection high-throughput liquid chromatography tandem mass spectrometry method for the determination of a new orally active ,v,3 antagonist in human urine and dialysateRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2003Wei Zeng A generic high-throughput liquid chromatography (HTLC) tandem mass spectrometry (MS/MS) assay for the determination of compound I in human urine and dialysate (hemodialysis) was developed and validated. By using the HTLC on-line extraction technique, sample pretreatment was not necessary. The sample was directly injected onto a narrow bore large particle size extraction column (50,×,1.0,mm, 60,,m) where the sample matrix was rapidly washed away using a high flow rate (5,mL/min) aqueous mobile phase while analytes were retained. The analytes were subsequently eluted from the extraction column onto an analytical column using an organic-enriched mobile phase prior to mass spectrometric detection. The analytes were then eluted from the analytical column to the mass spectrometer for the determination. The linear dynamic range was 2.0,6000,ng/mL for the urine assay and 0.1,300,ng/mL for the dialysate assay. Intraday accuracy and precision were evaluated by analyzing five replicates of calibration standards at all concentrations used to construct the standard curve. For the urine assay, the precision (RSD%, n,=,5) ranged from 1.9 to 8.0% and the accuracy ranged from 87.8 to 105.2% of nominal value. For the dialysate assay, the precision (RSD%, n,=,5) ranged from 1.1 to 10.0% and the accuracy from 94.5 to 105.2% of nominal value. In-source fragmentation of the acyl glucuronide metabolite (compound III) did not interfere with the determination of parent compound I. The developed HTLC/MS/MS methodology was specific for compound I in the presence of compound III. Column life-time is increased and sample analysis time is decreased over traditional reversed-phase methods when direct injection assays for urine and dialysate are coupled with the technology of HTLC. Copyright © 2003 John Wiley & Sons, Ltd. [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] A sensitive and specific liquid chromatography/tandem mass spectrometry method for determination of echinacoside and its pharmacokinetic application in ratsBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Hao Yang Abstract A rapid and sensitive method based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the determination of echinacoside in rat plasma was established and fully validated. A single step of liquid,liquid extraction with n -butanol was utilized. Chromatographic separation of the analyte and the internal standard (IS), chlorogenic acid, from the sample matrix was performed using a Capcell-MG C18 analytical column (100 2.0 mm × 5 µm), with a gradient of acetonitrile and water containing 0.1% acetic acid as the mobile phase. Detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization source operated in negative ion selected reaction monitoring mode. The method was linear in the concentration range 10,2500 ng/mL. The deviations of both intra- and inter-day precisions (RSD) were 7.1% and the assay accuracies were within 99.2,106.5%. Echinacoside proved to be stable during sample storage, preparation and analysis when an antioxidant solution was used. The method was successfully applied to a pharmacokinetic study in rats after an intragastric administration of echinacoside (100 mg/kg). With the lower limit of quantification at 10 ng/mL, this method proved to have sufficient selectivity, sensitivity and reproducibility for the pharmacokinetic study of echinacoside. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||