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Clean-up Step (clean-up + step)
Selected AbstractsPreparative isolation and purification of four flavonoids from the petals of nelumbo nucifera by high-speed counter-current chromatographyPHYTOCHEMICAL ANALYSIS, Issue 3 2010Xingfeng Guo Abstract Introduction , Flavonoids, the primary constituents of the petals of Nelumbo nucifera, are known to have antioxidant properties and antibacterial bioactivities. However, efficient methods for the preparative isolation and purification of flavonoids from this plant are not currently available. Objective , To develop an efficient method for the preparative isolation and purification of flavonoids from the petals of N. nucifera by high-speed counter-current chromatography (HSCCC). Methodology , Following an initial clean-up step on a polyamide column, HSCCC was utilised to separate and purify flavonoids. Purities and identities of the isolated compounds were established by HPLC-PAD, ESI-MS, 1H-NMR and 13C-NMR. Results , The separation was performed using a two-phase solvent system composed of ethyl acetate,methanol,water,acetic acid (4,:,1,:,5,:,0.1, by volume), in which the upper phase was used as the stationary phase and the lower phase was used as the mobile phase at a flow-rate of 1.0,mL/min in the head-to-tail elution mode. Ultimately, 5.0,mg syringetin-3- O-, -d-glucoside, 6.5,mg quercetin-3- O-, -d-glucoside, 12.8,mg isorhamnetin-3- O-, -d-glucoside and 32.5,mg kaempferol-3- O-, -d-glucoside were obtained from 125,mg crude sample. Conclusion , The combination of HSCCC with a polyamide column is an efficient method for the preparative separation and purification of flavonoids from the petals of N. nucifera. Copyright © 2009 John Wiley & Sons, Ltd. [source] Multi-residue analysis of eight thioamphetamine designer drugs in human urine by liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2009Maria Nieddu An analytical procedure for the simultaneous determination in human urine of several thioamphetamine designer drugs (2C-T and ALEPH series) is reported. The quantitative analysis was performed by liquid chromatography/tandem mass spectrometry and has been fully validated. The mass spectrometer was operated in positive-ion, selected reaction monitoring (SRM) mode. In order to minimize interferences with matrix components and to preconcentrate target analytes, solid-phase extraction was introduced in the method as a clean-up step. The entire method was validated for selectivity, linearity, precision and accuracy. The method turned out to be specific, sensitive, and reliable for the analysis of amphetamine derivatives in urine samples. The calibration curves were linear over the concentration range of 1 to 100,ng,mL,1 for all drugs with correlation coefficients that exceeded 0.996. The lower limits of detection (LODs) and quantification (LOQs) ranged from 1.2 to 4.9,ng,mL,1 and from 3.2 to 9.6,ng,mL,1, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Application to routine analysis of a method to determine multiclass pesticide residues in fresh vegetables by gas chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2002J. L. Martínez Vidal The use of gas chromatography/tandem mass spectrometry (GC/MS/MS) applied to determine multiple pesticide residues in fresh vegetables has been thoroughly studied. A single injection method to detect, confirm and quantify 54 multiclass pesticides has been developed and applied in a routine analysis laboratory. The proposed method consists of a rapid extraction of 15,g of vegetable sample with dichloromethane. An additional clean-up step is not necessary even when injecting 10,µL of extract. Instead the gas chromatograph was fitted with a carbofrit inserted into the glass liner and a guard column. In addition, the detection mode chosen (MS/MS) provides additional selectivity. The method has been validated and applied to 1300 samples in a routine laboratory following specified quality criteria. The recovery efficiencies obtained for all the pesticides ranged between 70.2 and 110.8% at two different fortification levels. The relative standard deviation for quantification (RSD) was lower than 16.7% for all the compounds. Important experimental parameters, such as the conditioning of carbofrit, overload of the analytical column, and cleanliness of the ion trap, were evaluated for their influence on the performance of the method. Copyright © 2002 John Wiley & Sons, Ltd. [source] Multiresidue determination of antibiotics in aquaculture fish samples by HPLC,MS/MSAQUACULTURE RESEARCH, Issue 9 2010Consuelo Cháfer-Pericás Abstract An analytical method based on HPLC with MS/MS detection was developed and optimized in order to determine the most useful antibiotics (sulphonamides and tetracyclines) used in aquaculture. A simple extraction procedure, without any clean-up step, was evaluated in order to obtain maximum analyte recovery from fish samples (Sparus aurata). A mixture of methanol:water 70:30 (v/v)+1 mL EDTA 0.1 M was selected as optimum extractant solution. Because no matrix effects were observed, a standard calibration curve prepared in mobile phase was used for quantification purposes. Antibiotic-free fish samples were spiked at different concentration levels and analysed by the optimized HPLC method. The average recoveries (n=6) obtained were satisfactory, ranging from 88% to 110% at 100 ,g kg,1. The proposed methodology provided limits of detection for the tested antibiotics in the 1.2,16 ,g kg,1 range, lower than 100 ,g kg,1, the maximum residue level established by the European Union. Finally, commercial fish samples from different origins were analysed in order to confirm the usefulness of the developed methodology. [source] A simple RP-HPLC method for quantification of columbianadin in rat plasma and its application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 4 2010You-Bo Zhang Abstract A rapid and sensitive reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed to investigate pharmacokinetics of columbianadin, one of the main bioactive constituents in the roots of Angelica pubescens f. biserrata, in rat plasma after intravenous administration to rats at two doses of 10 and 20,mg/kg. The method involves a plasma clean-up step using liquid,liquid extraction by diethyl ether, followed by RP-HPLC separation and detection. Separation of columbianadin was performed on an analytical DiamonsilÔ ODS C18 column, with a mobile phase of MeOH,H2O (85,:,15, v/v) at a flow-rate of 1.0,mL/min, and UV detection was set at 325,nm. The retention time of columbianadin and scoparone (internal standard) was 6.7 and 3.5,min, respectively. The calibration curve was linear over the range of 0.2,20.0,,g/mL (r2 = 0.9986) in rat plasma. The lower limits of detection and quantification were 0.05 and 0.1,,g/mL, respectively. The extraction recovery from plasma was in the range of 81.61,89.93%. The intra- and inter-day precisions (relative standard deviation) were between 1.01 and 9.33%, with accuracies ranging from 89.76 to 109.22%. The results indicated that the method established was suitable for the determination and pharmacokinetic study of columbianadin in rat plasma. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of caudatin-2,6-dideoxy-3 -O- methy- , - d -cymaropyranoside in rat plasma using liquid chromatography,tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 6 2008Yunru Peng Abstract A selective, sensitive and rapid liquid chromatography,tandem mass spectrometry method has been developed for the determination of caudatin-2,6-dideoxy-3 -O- methy- , - d -cymaropyranoside (CDMC) in rat plasma. This method involves a plasma clean-up step using liquid,liquid extraction, followed by LC separation and positive electrospray ionization mass spectrometry detection (LC/ESI-MS/MS). Chromatographic separation of the analytes was achieved using a C18 column with a mobile phase of acetonitrile and water (70:30, v/v) at a flow rate of 1.0 mL/min. Low energy collision tandem mass spectrometric analysis (CID-MS/MS) using the multiple reaction monitoring (MRM) mode was used for analyte quantification. For the MRM analysis of CDMC, the following transition at m/z 658.4 , 529.6 derived from the protonated molecule [M + Na]+. A calibration curve was linear in the 5,500 ng/mL range for CDMC, and the limit of detection was 5 ng/mL. The inter- and intra-day precisions (RSD) were ,8.5 and ,9.1%, respectively. The accuracy (RE) was ± 10.9%. The novel developed LC/ESI-MS/MS method was successfully applied to pharmacokinetic studies of CDMC after oral administration to rats. The total chromatographic run time of this method was 5.0 min per sample, allowing for analysis of a large number of samples per batch. Copyright © 2008 John Wiley & Sons, Ltd. [source] Determination of ligustilide in rat blood and tissues by capillary gas chromatography/mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 10 2006Yunfeng Shi Abstract A gas chromatography/mass spectrometry (GC/MS) method was developed to study the pharmacokinetics of ligustilide following oral administration to rats. The method was used for the analysis of samples taken from rats. Biological samples were prepared by liquid,liquid extraction (LLE) using an n -hexane,ether (2:1) solvent mixture for a sample clean-up step and analyzed by GC/MS with a quadrupole MS detector in selected ion monitoring mode (m/z 190). The calibration curves were linear over the concentration range 0.172,8.60 µg/mL (r > 0.99) for blood samples and a different range (r > 0.99) for different tissue samples. The limit of detection (LOD) was 1.0 ng/mL or 1.0 ng/g (three times the signal,noise ratio). Within- and between-day precision expressed as the relative standard deviation (RSD) for the method was 1.58,3.88 and 2.99,4.91%, respectively. The recovery for all samples was >80%, except for liver samples (>70%). The main pharmacokinetic parameters obtained were: Tmax = 0.65 ± 0.07 h, Cmax = 1.5 ± 0.2 µg/mL, AUC = 34 ± 6 h µg/mL and Ka = 3.5 ± 0.6/h. The experimental results showed that ligustilide was easily absorbed, but its elimination was slow, from 3 to 12 h after oral administration. The concentrations of ligustilide in rat cerebellum, cerebrum, spleen and kidney were higher than those in other organs. Copyright © 2006 John Wiley & Sons, Ltd. [source] Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of 4-sulfophenyl isothiocyanate-derivatized peptides on AnchorChipÔ sample supports using the sodium-tolerant matrix 2,4,6-trihydroxyacetophenone and diammonium citrateRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2005Leon P. Oehlers The reagent 4-sulfophenyl isothiocyanate (SPITC) is an effective, stable, and inexpensive alternative to commercially available reagents used in the N-terminal sulfonation of peptides for enhanced postsource decay (PSD) in matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analyses. However, suppression of ionization of sulfonated peptides due to sample and matrix contaminants such as sodium can be a problem when using prestructured MALDI target sample supports, such as the Bruker Daltonics AnchorChipÔ. We show that use of the salt-tolerant matrix 2,4,6-trihydroxyacetophenone containing diammonium citrate (THAP/DAC) as an alternative to , -cyanohydroxycinnamic acid (HCCA) reduces the need for extensive washing of ZipTip-bound peptides or additional on-target sample clean-up steps. Use of the THAP/DAC matrix results in selective ionization of sulfonated peptides with greater peptide coverage, as well as detection of higher mass derivatized peptides, than was observed for HCCA or THAP alone. The THAP/DAC matrix is quite tolerant of sodium contamination, with SPITC-peptides detectable in preparations containing up to 50,mM NaCl. In addition, THAP/DAC matrix was found to promote efficient PSD fragmentation of sulfonated peptides. We demonstrated the utility of using the THAP/DAC MALDI matrix for peptide sequencing with DNA polymerase , tryptic peptide mixture, as well as tryptic peptides derived from Xiphophorus maculatus brain extract proteins previously separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||