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Liquid Extraction (liquid + extraction)
Kinds of Liquid Extraction Terms modified by Liquid Extraction Selected AbstractsThe Use of N -Type Ligands in the Enantioselective Liquid,Liquid Extraction of Underivatized Amino AcidsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2010Bastiaan J. V. Verkuijl Abstract The first palladium based extraction system using chiral N -based ligands in the enantioselective liquid,liquid extraction (ELLE) of underivatized amino acids, is presented. The system shows the highest selectivity for the ELLE of methionine with metal complexes as hosts reported to date. Furthermore, the host can be prepared in situ from commercially available compounds. The dependency of the system on parameters such as pH, organic solvent, and temperature has been established. The intrinsic selectivity was deduced by determination of the association constants of the palladium complex with the tryptophan enantiomers. [source] Historical review of sample preparation for chromatographic bioanalysis: pros and consDRUG DEVELOPMENT RESEARCH, Issue 3 2007Min S. Chang Abstract Sample preparation is a major task in a regulated bioanalytical laboratory. The sample preparation procedure significantly impacts assay throughput, data quality, analysis cost, and employee satisfaction. Therefore, selecting and optimizing an appropriate sample preparation method is essential for successful method development. Because of our recent expertise, this article is focused on sample preparation for high-performance liquid chromatography with mass spectrometric detection. Liquid chromatography with mass spectrometric detection (LC-MS) is the most common detection technique for small molecules used in regulated bioanalytical laboratories. The sample preparation technologies discussed are pre-extraction and post-extraction sample processing, protein precipitation (PPT), liquid,liquid extraction (LLE), offline solid-phase extraction (SPE), and online solid-phase extraction. Since all these techniques were in use for more than two decades, numerous applications and variations exist for each technique. We will not attempt to categorize each variation. Rather, the development history, a brief theoretical background, and selected references are presented. The strengths and the limitations of each method are discussed, including the throughput improvement potential. If available, illustrations from presentations at various meetings by our laboratory are used to clarify our opinion. Drug Dev Res 68:107,133, 2007. ©2007 Wiley-Liss, Inc. [source] Simultaneous determination of memantine and amantadine in human plasma as fluorescein derivatives by micellar electrokinetic chromatography with laser-induced fluorescence detection and its clinical applicationELECTROPHORESIS, Issue 11 2010Hsin-Hua Yeh Abstract A nonionic surfactant MEKC method with LIF detection was developed for the simultaneous determination of memantine, an anti-Alzheimer's disease agent, and amantadine, an anti-Parkinson's disease drug, in human plasma. Before analysis, the plasma samples were pretreated by liquid,liquid extraction with ethyl acetate, and derivatized with 6-carboxyfluorescein N -hydroxysuccinimide ester. The chemical derivatization is performed with 6-carboxyfluorescein N -hydroxysuccinimide ester in ACN , 5,mM pH 9.0 borate buffer (40:60, v/v) at 35°C for 3,h. After the derivatization reaction, hydrodynamic injection (0.5,psi, 8,s) was used to introduce the derivatized solution, and the separation was performed in borate buffer (30,mM, pH 9.5) with the nonionic surfactant Brij-35® (0.07%, w/v); the separation voltage was 6,kV. The linear ranges of the method for the determination of memantine and amantadine in human plasma were over a range of 2.0,60.0,ng/mL. The detection limit was 0.5,ng/mL (S/N=3). This method was applied successfully to monitor the concentration of memantine or amantadine in patients with Alzheimer's disease or Parkinson's disease. [source] Mercury speciation by CE: An updateELECTROPHORESIS, Issue 1 2009Petr Kubán Abstract This review provides an update on mercury speciation by CE. It includes a brief discussion on physicochemical properties, toxicity and transformation pathways of mercury species (i.e. methyl-, ethyl-, phenyl- and inorganic mercury) and outlines recent trends in Hg speciation by CE. CE is presented as a complementary technique to chromatographic separation techniques, especially in cases when speed, high efficiency and low sample volumes are required. The development of suitable sample preconcentration/isolation (sample stacking, ion exchange, liquid,liquid,liquid extraction, dual-cloud point extraction) to achieve low LODs for analysis of trace concentrations of mercury species in real samples is emphasized. Hyphenation of CE to element specific detectors (i.e. electrothermal atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry) is discussed as well as a potential of CE in interaction studies that may provide useful information on interaction of various Hg species with selected bio-macromolecules. [source] Sensitive analysis of donepezil in plasma by capillary electrophoresis combining on-column field-amplified sample stacking and its application in Alzheimer's disease,ELECTROPHORESIS, Issue 17 2008Hsin-Hua Yeh Abstract Field-amplified sample stacking (FASS) in capillary electrophoresis (CE) was used to determine the concentration of donepezil, an acetylcholinesterase inhibitor, in human plasma. A sample pretreatment by liquid,liquid extraction with isopropanol/n -hexane (v/v 3:97) and subsequent quantification by FASS-CE was used. Before sample loading, a water plug (0.5,psi, 6,s) was injected to permit FASS. Electrokinetic injection (7,kV, 90,s) was used to introduce sample cations. The separation condition for donepezil was performed in electrolyte solutions containing Tris buffer (60,mM, pH 4.0) with sodium octanesulfonate 40,mM and 0.01% polyvinyl alcohol as a dynamic coating to reduce analytes' interaction with capillary wall. The separation was performed at 28,kV and detected at 200,nm. Using atenolol as an internal standard, the linear ranges of the method for the determination of donepezil in human plasma were over a range of 1,50,ng/mL. The limit of detection was 0.1,ng/mL (S/N=3, sampling 90,s at 7,kV). One female volunteer (54 years old) was orally administered a single dose of 10,mg donepezil (Aricept®, Eisai), and blood samples were drawn over a 60,h period for pharmacokinetic study. The method was also applied successfully to monitor donepezil in sixteen Alzheimer's disease patients' plasmas. [source] Development of HPLC and NACE methods for the simultaneous determination of benzoic and sorbic acids in sour snap beans containing oilELECTROPHORESIS, Issue 22 2007Po Han Abstract The practical methods were developed for the simultaneous determination of benzoic acid (BA) and sorbic acid (SA) in sour snap bean samples containing oil. BA and SA in the samples were extracted by ultrasonication with water, followed by cleanup procedures with precipitation for removing the potential proteins and with petroleum ether liquid,liquid extraction for removing the edible oil contained in the samples. The HPLC method was developed using Supelco C18 (250,mm×4.6,mm id, 5,,m) as column, MeOH,20,mM NH4Ac (25:75 v/v) at 1.0,mL/min as the mobile phase and 230,nm as the detection wavelength. The optimal NACE method was established with a running buffer of 20.0,mM NH4Ac in 95% MeOH (pH*,10.6), and an applied voltage of ,30,kV over a capillary of 50,,m id×48.5,cm (40,cm to the detector window), which gave a baseline separation of BA and SA, and as well as of the blank matrix within ca. 10,min. Both HPLC and NACE methods gave the relatively lower limits of quantification at about 0.01,0.02 and 0.04,0.05,mg/kg, respectively, whereas the overall recoveries were larger than 85.0%. The proposed methods have been successfully applied to measure 15 real sour bean samples and the content profile of BA and SA in sour bean samples was obtained and evaluated. [source] Validated capillary electrophoresis assay for the simultaneous enantioselective determination of propafenone and its major metabolites in biological samplesELECTROPHORESIS, Issue 8 2006Minoo Afshar Abstract A robust, inexpensive, and fully validated CE method for the simultaneous determination of the enantiomers of propafenone (PPF), 5-hydroxy-propafenone (5OH-PPF) and N -despropyl-propafenone (NOR-PPF) in serum and in in vitro media is described. It is based upon liquid,liquid extraction at alkaline pH followed by analysis of the reconstituted extract by CE in presence of a pH,2.0 running buffer composed of 100,mM sodium phosphate, 19% methanol, and 0.6% highly sulfated ,-CD. For each compound, the S -enantiomers are shown to migrate ahead of their antipodes, and the overall run time is about 30,min. Enantiomer levels between 25 and 1000,ng/mL provide linear calibration graphs, and the LOD for all enantiomers is between 10 and 12,ng/mL. The assay is shown to be suitable for the determination of the enantiomers of PPF and its metabolites in in vitro incubations comprising human liver microsomes or single CYP450 enzymes (SUPERSOMES). Incubations with CYP2D6 SUPERSOMES revealed, for the first time, the simultaneous formation of the enantiomers of 5OH-PPF and NOR-PPF with that enzyme. CE data can be used for the evaluation of the enzymatic N -dealkylation and hydroxylation rates. [source] Capillary electrophoretic chiral separation of hydroxychloroquine and its metabolites in the microsomal fraction of liver homogenatesELECTROPHORESIS, Issue 5-6 2006Carmem Dickow Cardoso Abstract A rapid, selective, and low-cost chiral capillary electrophoretic method was developed for the simultaneous analysis of hydroxychloroquine (HCQ) and its three chiral metabolites: desethylchloroquine (DCQ), desethylhydroxychloroquine (DHCQ), and bisdesethylchloroquine (BDCQ) in the microsomal fraction of liver homogenates. After liquid,liquid extraction using toluene as extracting solvent, the drug and metabolites were resolved on a fused-silica capillary (50,,m ID, 50,cm total length, and 42,cm effective length), using 100,mmol/L of Tris/phosphate buffer, pH,9.0 containing 1% w/v sulfated-,-CD and 30,mg/mL hydroxypropyl-,-CD. Detection was carried out at 220,nm. The extraction procedure was efficient in removing endogenous interferents, and low values (,15%) for CVs and deviation from theoretical values were demonstrated for both within-day and between-day assays. The quantitation limit was 125,ng/mL with linear response over the 125,2000,ng/mL of concentration range for all metabolites. After validation, the method was used for an in vitro metabolism study of HCQ. The major HCQ metabolite formed by microsomal enzymes was (,)-(R)-DHCQ. [source] Sensitive chiral analysis by capillary electrophoresisELECTROPHORESIS, Issue 1 2006Carmen García-Ruiz Abstract In this review, an updated view of the different strategies used up to now to enhance the sensitivity of detection in chiral analysis by CE will be provided to the readers. With this aim, it will include a brief description of the fundamentals and most of the recent applications performed in sensitive chiral analysis by CE using offline and online sample treatment techniques (SPE, liquid,liquid extraction, microdialysis, etc.), on-column preconcentration techniques based on electrophoretic principles (ITP, stacking, and sweeping), and alternative detection systems (spectroscopic, spectrometric, and electrochemical) to the widely used UV-Vis absorption detection. [source] Occurrence of pharmaceuticals and hormones in sewage sludgeENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2010Antonio Nieto Abstract The present study evaluates the presence of nine hormones and their conjugates and 20 pharmaceuticals such as anti-inflammatories, lipid regulators, and antibiotics among others in sewage sludge from two sewage treatment plants (STPs) in the Tarragona area (Spain) for the period March 2007 until March 2008. Target analytes have been determined using different methods involving pressurized liquid extraction and liquid chromatography (electrospray ionization) tandem mass spectrometry (MS-MS). Most of the pharmaceuticals and hormones were found at low micrograms per kilogram dry weight levels in the sewage sludge samples analyzed. Some compounds were present in all samples, such as acetaminophen, caffeine, carbamazepine, and ibuprofen, among others. Other compounds, such as estriol, were found only in the STP of Reus. The compounds that showed the highest concentration in both STPs were roxithromycin and tylosin (1,446 and 1,958,µg/kg dry wt, respectively). The presence of these compounds in sewage sludge demonstrated that they are partially or totally removed from the influent wastewater by sorption into the sewage sludge. Environ. Toxicol. Chem. 2010;29:1484,1489. © 2010 SETAC [source] Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper(II)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005Holger Stephan Abstract Dendritic oxybathophenanthroline ligands (generation 0 to 3) have been synthesized by treatment of 4,7-bis(4,-hydroxyphenyl)-1,10-phenanthroline with the corresponding Fréchet-type dendrons carrying a benzylic bromide function at the focal point. The complexation of copper(II) has been studied by liquid,liquid extraction using the radioisotope 64Cu and time-resolved laser-induced fluorescence spectroscopy (TRLFS) in organic media indicating the formation of 1:3 complexes (Cu:dendritic ligand). Electronic and EPR spectroscopy were used to characterize the copper(II) chromophore, which is shown to have the expected distorted square-planar geometry with two phenanthroline donors coordinated to the copper(II) center. The third dendritic ligand therefore is proposed to be bound by secondary interactions. The stability constants of the 1:3 complexes were found to be in the order of log K , 16 in CHCl3. On the other hand, increasing generation of the dendritic Fréchet-type branches leads to enhanced shielding of the copper ion from the environment. Additional information about this behaviour was obtained by the fluorescence lifetimes, which are much less influenced upon addition of copper(II) salt to solutions of the higher generation ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] The Use of N -Type Ligands in the Enantioselective Liquid,Liquid Extraction of Underivatized Amino AcidsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2010Bastiaan J. V. Verkuijl Abstract The first palladium based extraction system using chiral N -based ligands in the enantioselective liquid,liquid extraction (ELLE) of underivatized amino acids, is presented. The system shows the highest selectivity for the ELLE of methionine with metal complexes as hosts reported to date. Furthermore, the host can be prepared in situ from commercially available compounds. The dependency of the system on parameters such as pH, organic solvent, and temperature has been established. The intrinsic selectivity was deduced by determination of the association constants of the palladium complex with the tryptophan enantiomers. [source] Volatile composition of the laksa plant (Polygonum hydropiper L.), a potential source of green note aroma compoundsFLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2005J. Jiang Abstract Volatile compounds were extracted from laksa plant (Polygonum hydropiper L.) by three isolation techniques,dynamic headspace sampling, simultaneous distillation and extraction (SDE) and liquid,liquid extraction with dichloromethane (DCM). In the GC,MS analysis of the volatile extracts, a total of 46 compounds were identi,ed, including 14 carbonyls, 14 alcohols, 10 hydrocarbons, four esters, two furans, one acid and one base. Carbonyls (aldehydes/ketones) and alcohols are the predominant classes of volatile compounds, accounting for almost 90% (or above) of the total volatiles extracted from the plant. The major compounds include dodecanal (3,40%), (E)-2-hexenal (20,35%), decanal (4,22%), (Z)-3-hexen-1-ol (4,31%), hexanal (1.7,5.1%) and , -caryophyllene (1.7,2.3%). Signi,cantly high levels of both (E)-2-hexenal (leaf aldehyde) and (Z)-3-hexen-1-ol (leaf alcohol) may make the weed plant become a potential source of green note aroma componds. More (Z)-3-hexen-1-ol was found in the stem while more (E)-2-hexenal was detected in the leaf. The laksa stem appeared to contain more decanal and dodecanal but less esters than the leaf. Different isolation techniques produced volatile extracts with different proportions of the major volatile components. Copyright © 2005 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry for the determination of flocoumafen and brodifacoum in whole bloodJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2007Mi-cong Jin Abstract A high-performance liquid chromatographic,tandem mass spectrometric (HPLC,MS,MS) assay was developed and validated to determine quantitatively flocoumafen and brodifacoum in whole blood using warfarin as an internal standard (IS). Liquid,liquid extraction, using ethyl acetate, was used to isolate flocoumafen, brodifacoum and the IS from the biological matrix. Detection was performed on a mass spectrometer by negative electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The calibration curves were linear (r2 > 0.998) in the concentration range of 0.1,100.0 ng ml,1 with a lower limit of quantification of 0.05 ng ml,1 for flocoumafen, and 0.1 ng ml,1 for brodifacoum in whole blood. Intra-day and inter-day relative standard deviations (RSDs) were less than 8.0% and 10.8%, respectively. Recoveries of flocoumafen and brodifacoum ranged from 78.0% to 83.7%. This assay can be used to determine trace flocoumafen and brodifacoum in whole blood to investigate suspected poisoning of human and animals. Copyright © 2006 John Wiley & Sons, Ltd. [source] Solvent extraction studies of Sm(III) from nitrate medium and separation factors of rare earth elements with mixtures of sec -octylphenoxyacetic acid and 1,10-phenthrolineJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2010Shujuan Fan Abstract BACKGROUND: Liquid,liquid extraction is widely used for the separation of rare earths, among which synergistic extraction has attracted more and more attention. Numerous types of synergistic extraction systems have been applied to rare earths with high extraction efficiency and selectivities. In the present study, mixtures of sec -octylphenoxyacetic acid (CA12, H2A2) and 1,10-phenanthroline (phen, B) have been used for the extraction of rare earths from nitrate medium. The stoichiometry of samarium(III) extraction has been studied using the methods of slope analysis and constant molar ratio. The possibility of using synergistic extraction effects to separate rare earths has also been studied. RESULTS: Mixtures of CA12 and phen display synergistic effects in the extraction of rare earth elements giving maximum enhancement coefficients of 5.5 (La); 13.7 (Nd); 15.9 (Sm); 24.5 (Tb); 45.4 (Yb) and 12.3 (Y). Samarium(III) is extracted as SmHA4B3 with mixtures of CA12 and phen instead of SmHA4 when extracted with CA12 alone. The calculated logarithm of the equilibrium constant is 6.0 and the thermodynamic functions, ,H, ,G, and ,S, have been calculated as 4.3 kJ mol,1, , 33.7 kJ mol,1 and 129.7 J mol,1 K,1, respectively. CONCLUSION: Mixtures of CA12 and phen exhibit synergistic effects on rare earth elements. Graphical and numerical methods have been successfully used to determine their stoichiometries. The different synergistic effects may provide the possibility of separating yttrium from heavy lanthanoids at an appropriate ratio of CA12 and phen. Copyright © 2010 Society of Chemical Industry [source] Liquid,liquid extraction of cadmium(II) by Cyanex 923 and its application to a solid-supported liquid membrane systemJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2005Ana María Rodríguez Abstract The extraction of cadmium(II) by Cyanex 923 (a mixture of alkylphosphine oxides) in Solvesso 100 from hydrochloric acid solution has been investigated. The extraction reaction is exothermic. The numerical analysis of metal distribution data suggests the formation of CdCl2.2L, HCdCl3.2L and H2CdCl4.2L (L = ligand) in the organic phase. The results obtained for cadmium(II) distribution have been implemented in a solid-supported liquid membrane system. The influences of feed phase stirring speed (400,1400 min,1), membrane composition (carrier concentration: 0.06,1 mol dm,3) and metal concentration (0.01,0.08 g dm,3) on cadmium transport have been investigated. Copyright © 2005 Society of Chemical Industry [source] Liquid,liquid extraction of Hg(II) from acidic chloride solutions using bis-2-ethylhexyl sulfoxideJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2001Tania Francis Abstract The liquid,liquid extraction of Hg(II) from acidic chloride solutions has been studied using bis-2-ethylhexyl sulfoxide (B2EHSO) as an extractant. For comparison, extraction studies have also been carried out using di- n -octyl sulfoxide (DOSO) and diphenyl sulfoxide (DPhSO). The extraction data have been analysed by both graphical and theoretical methods taking into account aqueous phase speciation and all plausible complexes extracted into the organic phase. These results demonstrate that Hg(II) is extracted into xylene as HgCl2.3R2SO (where R2SO represents the sulfoxide). The equilibrium constant of the extracted complex has been deduced by non-linear regression analysis. The developed liquid,liquid extraction procedure has been applied for the recovery of mercury from the brine-sludge of a Chlor-Alkali plant. © 2001 Society of Chemical Industry [source] APPLICATION OF EXPERIMENTAL DESIGN METHOD TO THE OIL EXTRACTION FROM OLIVE CAKEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2 2009SMAIL MEZIANE ABSTRACT Olive cake is an important solid waste of the olive oil production. It still contains a certain quantity of oil that can be recovered by means of solvent extraction. In this study, two-level full factorial design was performed to evaluate the effects of four variables and their interactions on the oil extraction by the ethanol 96.0% in a batch reactor. The variables included size of particles, temperature, and time of contact and solvent-to-solids ratio. The statistical analysis of the experimental data showed that the extracted oil mass depends on all the examined variables. It also depends on the interactions between size of particles and solvent-to-solid ratio and size of particles and temperature. The experimental data were in good agreement with those predicted by the model. PRACTICAL APPLICATIONS Olive cake is solid waste of the olive oil industry that is available in large amounts in many Mediterranean countries and at very low cost. It can be treated or valorized, enabling at the same time the solution to environmental problems caused by the olive oil production process. The economic interest that it presents is especially because of the residual oil that it contains and that can be recovered by solvent extraction. However, this solid,liquid extraction depends on several parameters: the ones inherent to the products (structure and properties of the sample, nature of extraction solvent); and the others to the extraction process (time of contact, temperature of extraction, solvent-to-solid ratio, stirring velocity). The experimental design method enables to determine the most important variables and their interaction in the extraction process at the same time performing a low number of experiments. [source] Kinetic and dynamic study of liquid,liquid extraction of copper in a HFMC: Experimentation, modeling, and simulationAICHE JOURNAL, Issue 6 2010M. Younas Abstract In this work, we present the dispersion-free liquid,liquid extraction of copper from aqueous streams in a hollow fiber membrane contactor (HFMC). Copper has been transferred from aqueous solutions to heptane using LIX 84-I (2-hydroxy-5-nonylacetephenone oxime) as extracting agent. In a first step, batch experiments have been performed to identify the extraction kinetics and to measure the partition coefficient of copper aqueous-organic phase system. Then, the continuous recycled-base extraction process has been performed in a HFMC Liqui-Cel® module. The module has been modeled from resistance in series concept to gain the exit concentrations, which are used to develop a dynamic model to calculate the exit concentration of copper from the output of storage tanks. The model has been validated with experimental data at various operating conditions. The integrated process model algorithm was scripted in MATLAB® 7.4 R (a). Simulations have been made for a range of different operating parameters to determine the optimum criterion conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] An ionic liquid proposed as solvent in aromatic hydrocarbon separation by liquid extractionAICHE JOURNAL, Issue 2 2010Ana B. Pereiro Abstract Liquid,liquid extraction is the most common method for extraction of aromatics from their mixtures with aliphatic hydrocarbons. An ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide [BMpyr][NTf2] was tested as solvent for this separation. The liquid,liquid equilibria (LLE) of the ternary mixtures heptane + benzene, or toluene, or ethylbenzene + [BMpyr][NTf2] were carried out at 298.15 K. The solvent ability of the IL was evaluated in terms of solute distribution ratio and selectivity. The results were compared with those previously reported for the extraction of aromatics from its mixtures with heptane by using ILs. The conventional process using sulfolane as solvent was discussed. The experimental LLE data were correlated by non-random two liquid equation. A proposal of extraction process with this IL as solvent is simulated by conventional software and the results are shown. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Fully automated liquid extraction-based surface sampling and ionization using a chip-based robotic nanoelectrospray platform,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2010Vilmos Kertesz Abstract A fully automated liquid extraction-based surface sampling device utilizing an Advion NanoMate chip-based infusion nanoelectrospray ionization system is reported. Analyses were enabled for discrete spot sampling by using the Advanced User Interface of the current commercial control software. This software interface provided the parameter control necessary for the NanoMate robotic pipettor to both form and withdraw a liquid microjunction for sampling from a surface. The system was tested with three types of analytically important sample surface types, viz., spotted sample arrays on a MALDI plate, dried blood spots on paper, and whole-body thin tissue sections from drug dosed mice. The qualitative and quantitative data were consistent with previous studies employing other liquid extraction-based surface sampling techniques. Published in 2009 by John Wiley & Sons, Ltd. [source] Characterization of N -palmitoylated human growth hormone by in situ liquid,liquid extraction and MALDI tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2007Emmanuelle Sachon Abstract Acylation is a common post-translational modification found in secreted proteins and membrane-associated proteins, including signal transducing and regulatory proteins. Acylation is also explored in the pharmaceutical and biotechnology industry to increase the stability and lifetime of protein-based products. The presence of acyl moieties in proteins and peptides affects the physico-chemical properties of these species, thereby modulating protein stability, function, localization and molecular interactions. Characterization of protein acylation is a challenging analytical task, which includes the precise definition of the acylation sites in proteins and determination of the identity and molecular heterogeneity of the acyl moiety at each individual site. In this study, we generated a chemically modified human growth hormone (hGH) by incorporation of a palmitoyl moiety on the N, group of a lysine residue. Monoacylation of the hGH protein was confirmed by determination of the intact molecular weight by mass spectrometry. Detailed analysis of protein acylation was achieved by analysis of peptides derived from hGH by protease treatment. However, peptide mass mapping by MALDI MS using trypsin and AspN proteases and standard sample preparation methods did not reveal any palmitoylated peptides. In contrast, in situ liquid,liquid extraction (LLE) performed directly on the MALDI MS metal target enabled detection of acylated peptide candidates by MALDI MS and demonstrated that hGH was N -palmitoylated at multiple lysine residues. MALDI MS and MS/MS analysis of the modified peptides mapped the N -palmitoylation sites to Lys158, Lys172 and Lys140 or Lys145. This study demonstrates the utility of LLE/MALDI MS/MS for mapping and characterization of acylation sites in proteins and peptides and the importance of optimizing sample preparation methods for mass spectrometry-based determination of substoichiometric, multi-site protein modifications. Copyright © 2007 John Wiley & Sons, Ltd. [source] A rapid and sensitive liquid chromatography/positive ion tandem mass spectrometry method for the determination of cimetropium in human plasma by liquid,liquid extractionJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2006Heon-Woo Lee Abstract We have developed and validated a simple detection system with high-performance liquid chromatography (HPLC) with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) for determining cimetropium levels in human plasma using scopolamine butyl bromide as an internal standard (I.S.). The acquisition was performed in the multiple reaction monitoring (MRM) mode, by monitoring the transitions: m/z 357.9 > 103.1 for cimetropium and m/z 359.9 > 103.1 for butyl-scopolamine. The method involves a simple single-step liquid,liquid extraction with dichloromethane. The analyte was chromatographed on an YMC C18 reversed-phase chromatographic column by isocratic elution with 10 mM ammonium formate buffer,methanol (19 : 81, v/v; adjusted to pH 4.0 with formic acid). The results were linear over the studied range (0.2,100 ng ml,1), with r2 = 1.0000, and the total analysis time for each run was 2 min. Intra- and interassay precisions were 0.70,8.54% and 1.08,4.85%, respectively, and intra- and interassay accuracies were 97.56,108.23% and 97.48,103.91%, respectively. The lower limit of quantification (LLOQ) was 0.2 ng ml,1. At this concentration, mean intra- and interassay precisions were 8.54% and 4.85%, respectively, and mean intra- and interassay accuracies were 97.56% and 98.91%, respectively. The mean recovery ranged from 62.71 ± 4.06 to 64.23 ± 2.32%. Cimetropium was found to be stable in plasma samples under typical storage and processing conditions. The devised assay was successfully applied to a pharmacokinetic study of cimetropium bromide administered as a single oral dose (150 mg) to healthy volunteers. Copyright © 2006 John Wiley & Sons, Ltd. [source] New designer drug, 2,5-dimethoxy-4-propylthio-,-phenethylamine (2C-T-7): studies on its metabolism and toxicological detection in rat urine using gas chromatography/mass spectrometry,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2005Denis S. Theobald Abstract Studies are described on the metabolism and toxicological analysis of the phenethylamine-derived designer drug 2,5-dimethoxy-4-propylthio-,-phenethylamine (2C-T-7) in rat urine using gas chromatography/mass spectrometry (GC/MS). The identified metabolites indicated that 2C-T-7 was metabolized by hydroxylation of the propyl side chain followed by N -acetylation and sulfoxidation and also by deamination followed by oxidation to the corresponding acid or by reduction to the corresponding alcohol. To a minor extent, 2C-T-7 was also metabolized by S -dealkylation followed by N -acetylation, S -methylation and sulfoxidation. The authors' systematic toxicological analysis (STA) procedure using full-scan GC/MS after acid hydrolysis, liquid,liquid extraction microwave-assisted acetylation allowed the detection of an intake of a dose of 2C-T-7 in rat urine that corresponds to a common drug users' dose. Assuming similar metabolism, the described STA procedure should be suitable for proof of an intake of 2C-T-7 in human urine. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ticlopidine quantification in human plasma by high-performance liquid chromatography coupled to electrospray tandem mass spectrometry.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2004Application to bioequivalence study Abstract A rapid, sensitive and specific method to quantify ticlopidine in human plasma using clopidogrel as the internal standard (IS) is described. The analyte and the IS were extracted from acidified plasma by liquid,liquid extraction using diethyl ether,hexane (80 : 20, v/v). The extracts were analyzed by high-performance liquid chromatography coupled to electrospray tandem mass spectrometry (HPLC/MS/MS). Chromatography was performed isocratically on a Jones Genesis C8 4 µm analytical column (150 × 4.1 mm i.d.). The method had a chromatographic run time of 3.0 min and a linear calibration curve over the range 1.0,1000 ng ml,1 (r2 > 0.999427). The limit of quantification was 1.0 ng ml,1. This HPLC/MS/MS procedure was used to assess the bioequivalence of two ticlopidine 250 mg tablet formulations (ticlopidine test formulation from Apotex do Brasil, Brazil, and Ticlid from Sanofi-Synthelabo, standard reference formulation). A single 250 mg dose of each formulation was administered to healthy volunteers. The study was conducted using an open, randomized, two-period crossover design with a 2 week washout interval. Since the 90% confidence interval for Cmax and area under the curve ratios were all inside the 80,125% interval proposed by the US Food and Drug Administration, it was concluded that ticlopidine formulation from Apotex do Brasil is bioequivalent to Ticlid formulation with respect to both the rate and the extent of absorption. Copyright © 2004 John Wiley & Sons, Ltd. [source] Quantitative analysis of the P-glycoprotein inhibitor Elacridar (GF120918) in human and dog plasma using liquid chromatography with tandem mass spectrometric detectionJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2004Ellen Stokvis Abstract A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method for the determination of the P-glycoprotein and breast cancer resistance protein inhibitor Elacridar in human and dog plasma is described. The internal standard was stable isotopically labelled Elacridar. Sample pretreatment involved liquid,liquid extraction with tert -butyl methyl ether. Analysis of Elacridar and internal standard was performed by reversed-phase LC on a basic stable minibore analytical column with an eluent consisting of acetonitrile and aqueous ammonia. An API-2000 triple-quadrupole mass spectrometer with an electrospray ion source was used in the positive-ion multiple reaction monitoring mode. The run time per sample was only 6 min. The method is sensitive and specific, with a dynamic range from 1 to 500 ng ml,1 from 100 µl of human or dog plasma. The accuracy of the method was within 15% bias and the precision was lower than 15% for all tested concentration levels and in both matrices. The method is simple and the liquid,liquid extraction produces clean samples. This method was successfully applied to support the pharmacokinetics of a clinical trial in which orally applied Elacridar was used as a bioavailability enhancer. Copyright © 2004 John Wiley & Sons, Ltd. [source] Screening, library-assisted identification and validated quantification of 23 benzodiazepines, flumazenil, zaleplone, zolpidem and zopiclone in plasma by liquid chromatography/mass spectrometry with atmospheric pressure chemical ionizationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2004Carsten Kratzsch Abstract A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (LC/APCI-MS) is presented for fast and reliable screening and identification and also for precise and sensitive quantification in plasma of the 23 benzodiazepines alprazolam, bromazepam, brotizolam, camazepam, chlordiazepoxide, clobazam, clonazepam, diazepam, flunitrazepam, flurazepam, desalkylflurazepam, lorazepam, lormetazepam, medazepam, metaclazepam, midazolam, nitrazepam, nordazepam, oxazepam, prazepam, temazepam and tetrazepam, triazolam, their antagonist flumazenil and the benzodiazepine BZ1 (omega 1) receptor agonists zaleplone, zolpidem and zopiclone. It allows confirmation of the diagnosis of an overdose situation and monitoring of psychiatric patients' compliance. The analytes were isolated from plasma using liquid,liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' LC/MS library, the analytes were quantified in the selected-ion monitoring mode. The quantification assay was fully validated. It was found to be selective proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes, except bromazepam. The corresponding reference levels the assay's accuracy and precision data for all studied substances are listed. The accuracy and precision data were within the required limits with the exception of those for bromazepam. The analytes were stable in frozen plasma for at least 1 month. The validated assay was successfully applied to several authentic plasma samples from patients treated or intoxicated with various benzodiazepines or with zaleplone, zolpidem or zopiclone. It has proven to be appropriate for the isolation, separation, screening, identification and quantification of the drugs mentioned above in plasma for clinical toxicology, e.g. in cases of poisoning, and forensic toxicology, e.g. in cases of driving under the influence of drugs. Copyright © 2004 John Wiley & Sons, Ltd. [source] Simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method for the quantification of lacidipine in human plasmaJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2004N. V. S. Ramakrishna Abstract A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantification of lacidipine in human plasma using its structural analogue, amlodipine, as internal standard (IS). The method involves a simple single-step liquid,liquid extraction with tert -butyl methyl ether. The analyte was chromatographed on an Xterra MS C18 reversed-phase chromatographic column by isocratic elution with 20 mM ammonium acetate buffer,acetonitrile (10 : 90, v/v; pH 6) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 456.4 , 354.4 and m/z 409.3 , 238.3 were used to measure the analyte and the I.S., respectively. The chromatographic run time was 1.5 min and the weighted (1/x2) calibration curves were linear over the range 0.1,25 ng ml,1. Lacidipine was sensitive to temperature in addition to light. The method was validated in terms of accuracy, precision, absolute recovery, freeze,thaw stability, bench-top stability and re-injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 50 and 100 pg ml,1, respectively. The within- and between-batch accuracy and precision were found to be well within acceptable limits (<15%). The analyte was stable after three freeze,thaw cycles (deviation <15%). The average absolute recoveries of lacidipine and amlodipine (IS) from spiked plasma samples were 51.1 ± 1.3 and 50.3 ± 4.9%, respectively. The assay method described here could be applied to study the pharmacokinetics of lacidipine. Copyright © 2004 John Wiley & Sons, Ltd. [source] Rate-based nonisothermal LLX model and its experimental validationAICHE JOURNAL, Issue 2 2004Debjit Sanpui Abstract Most of the current open literature handles liquid,liquid extraction (LLX) using equilibrium and/or isothermal models. However, in most industrial applications, the assumption of equilibrium and isothermal operation is not reasonable. A rate-based nonequilibrium model for both the mass and energy transfer in LLX during the three distinct stages of drop formation,drop, fall or rise, and drop coalescence,has been developed. These three hydrodynamic phenomena affect the mass transfer between dispersed and continuous phases for which a parallel,parallel mass-transfer resistance model has been incorporated. Because of the very large number of computations associated with repeated calculations of mass-transfer coefficients a local model has been proposed. We have compared our rate-based simulator with two other commercial simulators and our bench-scale experiments have been done for toluene,acetone,water and methyl isobutyl ketone,acetic acid,water systems. Stagewise mass and energy transfer and the hydrodynamics features have been compared between the experimental and the simulation runs. Relative-error square analysis (for the concentration profiles) shows that our simulation results are two orders of magnitude better in comparison to other commercial simulators. © 2004 American Institute of Chemical Engineers AIChE J, 50: 368,381, 2004 [source] Metal ion-binding ability of tetrapeptides containing ,-aminoisobutyric acidJOURNAL OF PEPTIDE SCIENCE, Issue 3 2004Masayuki Hanyu Abstract ,-Aminoisobutyric acid (Aib), one of the C,, , -disubstituted glycines, is a sterically hindered amino acid that acts as a conformational constraint in peptides. However, studies for the application of the ability of Aib to control conformation are quite few. The paper focuses on the molecular recognition ability of acyclic oligopeptides containing Aib. Liquid,liquid extraction of nine kinds of metal ions from aqueous layers to nonpolar organic layers with acyclic tetrapeptides, X-Trp-Xaa2 -Gly-Xaa4 -NH-Ar (X = H or C6H5CH2OCO (Z), Xaa2 = Aib or Gly, Xaa4 = Leu or Ala, Ar = phenyl or 3,5-dimethylphenyl) was examined using picrate as the anion of ion pairs. The extraction behaviour of the metal ions with the tetrapeptides was investigated in the pH range from 3 to 9. In the case of basic pH regions, Cu(II) and Ag(I) were effectively extracted with Trp-Aib-Gly-Leu-NH-Ar. Pd(II) was specifically extracted with Trp-Aib-Gly-Leu-NH-Ar in acidic pH regions. The extraction percent (%E) of the peptide host, which has a 3,5-dimethylphenyl group, was even larger than that of the host, which has a phenyl group. Moreover, Pd(II) was extracted with a peptide host which has Leu and a 3,5-dimethylphenyl group in the absence of picrate as the anion of ion pairs. The free ,-amino group, the turn conformation and the hydrophobicity of peptide molecules were important factors for the extraction of the metals. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||