Showing papers on "Elution published in 2007"
TL;DR: The developed extraction procedures resulted in good repeatability and reproducibility with relative standard deviations (RSDs) less than 13% for all the tested compounds for both types of samples, and the developed methods were successfully applied to the analysis of the target compounds in real samples.
315 citations
TL;DR: A liquid chromatography-tandem mass spectrometry screening method has been developed targeting 23 pharmaceuticals and 2 metabolites with differing physicochemical properties in fish tissue and was subsequently used to screen for target analytes in fish from an effluent-dominated stream.
Abstract: A liquid chromatography-tandem mass spectrometry (LC-MS/MS) screening method has been developed targeting 23 pharmaceuticals and 2 metabolites with differing physicochemical properties in fish tissue. Reversed-phase separation of target compounds was achieved using a C18 column and a nonlinear gradient consisting of 0.1% (v/v) formic acid and methanol. Eluted analytes were introduced into the mass analyzer using positive or negative electrospray ionization, as appropriate. A variety of extraction solvents, differing in polarity, pH, or both, were investigated in order to assess recovery of target compounds from 1-g tissue homogenates. Among 10 solvents tested, a 1:1 mixture of 0.1 M aqueous acetic acid (pH 4) and methanol was identified as optimal, resulting in extraction recoveries for 24 of 25 compounds exceeding 60%. Tissue extracts were found to influence the LC-MS/MS response for several analytes. Consequently, matrix-matched calibration standards were employed to determine analyte concentrations in environmental samples. Statistically derived method detection limits were <6 ng/g for most analytes. The method was subsequently used to screen for target analytes in fish from an effluent-dominated stream. Diphenhydramine, diltiazem, carbamazepine, and norfluoxetine were detected in 11 of 11 environmental samples at concentrations ranging from 0.11 to 5.14 ng/g.
260 citations
TL;DR: An improved analytical method for the simultaneous quantification of 17 kinds of Aspergillus, Fusarium and Penicillium mycotoxin contaminants in foods and feeds by ultra-performance liquid chromatography combined with electrospray ionization triple quadrupole tandem mass spectrometry under the multiple reaction monitoring (MRM) mode.
227 citations
TL;DR: The usefulness of porous graphitic carbon columns coupled to ESI-MS for the separation of N-glycans with two or more sialic acids and the separation system's potential for analyzing tri- and tetrasialylated N- glycans was demonstrated.
Abstract: Analysis of the numerous possible, often isobaric structures of protein-bound oligosaccharides calls for a high-performance two-dimensional method that combines liquid chromatography's ability to separate isomers and mass spectrometry's ability to determine glycan composition. Here we investigate the usefulness of porous graphitic carbon columns coupled to ESI-MS for the separation of N-glycans with two or more sialic acids. Internal standards helped to rectify retention time fluctuations and thus allowed elution times to play an essential role in the structural assignment of peaks. For generation of a retention time library, standards representing the possible isomers of diantennary non-, mono-, and disialylated N-glycans, differing in the linkage of galactose and sialic acids as well as isobaric hybrid-type N-glycans, were produced using recombinant glycosyltransferases. Once the retention times library was established, isomers could be identified by LC-ESI-MS in the positive mode without additional MS/...
192 citations
TL;DR: River water and wastewater treatment plant effluents from metropolitan Taipei, Taiwan were tested for the presence of the pollutants estrone (E1), estriol (E3), 17beta-estradiol (E2), and 17alpha-ethinylest radiol (EE2) using a new methodology that involves high-flow solid-phase extraction and liquid chromatography/tandem mass spectrometry.
172 citations
TL;DR: The solid-phase extraction (SPE) joined with the dispersive liquid-liquid microextraction (DLLME) has been developed as an ultra preconcentration technique for the determination of chlorophenols in water samples.
171 citations
TL;DR: A general screening method based on solid phase extraction and liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) was developed and investigated with 124 different doping agents, including stimulants, beta-blockers, narcotics, beta(2)-adrenergic agonists, agents with anti-estrogenic activity, diuretics and cannabinoids.
154 citations
TL;DR: Developed strategy has been demonstrated to be an improvement over existing methods due to its greater sensitivity and the low volume of matrix used and the total analysis time (extraction, derivatization, analysis) is less than 17 min.
145 citations
TL;DR: The satisfactory recovery values obtained without using analyte addition method confirms the feasibility of this method for Pb (II) ions determination in different type of samples.
143 citations
TL;DR: The 40s that are usually used for the polymerization of resin composites seems insufficient in order to prevent a high release of monomers after polymerization, as shown in the results of this study.
141 citations
TL;DR: An automated online multidimensional liquid chromatography system coupled to ESI-based tandem mass spectrometry was used to assess the effectiveness of TiO2 in the enrichment of phosphopeptides from tryptic digests of protein mixtures, where TiO 2 was shown to be superior in performance.
Abstract: An automated online multidimensional liquid chromatography system coupled to ESI-based tandem mass spectrometry was used to assess the effectiveness of TiO2 in the enrichment of phosphopeptides from tryptic digests of protein mixtures. By monitoring the enrichment of phosphopeptides, an optimized set of loading, wash, and elution conditions were realized for TiO2. A comparison of TiO2 with other resins used for phosphopeptide enrichment, Fe(III)-IMAC and ZrO2, was also carried out using tryptic digests of both simple and moderately complex protein mixtures; where TiO2 was shown to be superior in performance.
TL;DR: This work builds the EECCC concept by performing a full theoretical treatment and providing equations for retention volumes, peak widths, resolution factors, and distribution constants, and improves the improved capabilities of KD targeting.
Abstract: Elution−extrusion countercurrent chromatography (EECCC) takes full advantage of the liquid nature of the stationary phase in CCC by combining regular chromatographic elution with stationary-phase extrusion. EECCC is shown to be a three-stage process consisting of classical elution (I), sweeping elution (II), and extrusion (III). After only two column volumes of solvent, it rapidly yields a high-resolution chromatogram that covers an extended polarity range of solutes. As hydrophilicity/lipophilicity balance is a crucial discriminatory property of analytes in highly complex mixtures such as metabolomic samples, the precise determination of CCC distribution constants (KD) is vital to the analysis of metabolomes and other complex biological matrixes. This work builds the EECCC concept by performing a full theoretical treatment and providing equations for retention volumes, peak widths, resolution factors, and distribution constants. Experimental validation utilizes natural products standards that resemble th...
TL;DR: The present work demonstrates that the mixed stationary phase is efficient and selective and can be an alternative choice for the GC analysis of samples of complex composition.
Abstract: The seeming “dual nature” of ionic liquids (ILs) for separating both apolar and polar compounds suggests that ILs may have a great potential for complex samples like essential oils from herbal plants that contain a great variety of compounds. In the present work, a geminal dicationic IL, 1,9-di(3-vinylimidazolium)nonane bis[(trifluoromethyl)sulfonyl]imidate, was investigated for this purpose. To find the best way to achieve satisfactory separations simultaneously for the compounds in essential oils, the dicationic IL was used as the stationary phase for capillary gas chromatography (GC) in two ways, either in its pure state or as a mixed stationary phase with monocationic ILs and a polysiloxane diluent. Interestingly, it was found that the mixed stationary phase exhibited a much better selectivity for polar and nonpolar compounds than either the dicationic IL or the polysiloxane, suggesting that a kind of synergistic effect occurred when these stationary phases were combined in the way described. A comparison with two commercial stationary phases (polar and nonpolar) indicated that this novel mixed stationary phase behaved in a way closer to a polar stationary phase in terms of selectivity and elution order. The present work demonstrates that the mixed stationary phase is efficient and selective and can be an alternative choice for the GC analysis of samples of complex composition.
TL;DR: In this paper, a new technique, crystallization elution fractionation (CEF), combines the separation power of Tthis paper and CRYSTAF and has been shown to provide very fast analysis of the composition distribution.
Abstract: New crystallization procedures have been developed for the analysis of the chemical composition distribution in polyolefins by pumping a small flow of solvent during the crystallization cycle. One of the new techniques, crystallization elution fractionation (CEF) combines the separation power of TREF and CRYSTAF and has been shown to provide very fast analysis of the composition distribution.
TL;DR: A novel micro-extraction procedure was developed through the use of an electrospun polymer nanofiber as a solid-phase extraction (SPE) sorbent to directly extract trazodone from human plasma using a high performance liquid chromatography with ultraviolet detector (HPLC-UV) system.
TL;DR: Elution from the Protein A resin was found to increase the aggregation rate constants over and above what would be expected from exposure to low pH conditions in solution alone, demonstrating that Protein A-Fc interactions can destabilize product structure and increase the tendency to aggregate.
TL;DR: This work describes the standard protocol using an automated FAC system (FAC-1), consisting of two isocratic pumps, an autosampler, a column oven and two miniature columns connected to a fluorescence detector, which has so far obtained quantitative interaction data of >100 lectins for >100 PA oligosaccharides.
Abstract: Frontal affinity chromatography using fluorescence detection (FAC-FD) is a versatile technique for the precise determination of dissociation constants (Kd) between glycan-binding proteins (lectins) and fluorescent-labeled glycans. A series of glycan-containing solutions is applied to a lectin-immobilized column, and the elution profile of each glycan (termed the 'elution front', V) is compared with that (V0) for an appropriate control. Here we describe our standard protocol using an automated FAC system (FAC-1), consisting of two isocratic pumps, an autosampler, a column oven and two miniature columns connected to a fluorescence detector. Analysis time for 100 sugar-protein interactions is approximately 10 h, using as little as 2.5 pmol of pyridylaminated (PA) oligosaccharide per analysis. Using FAC-FD, we have so far obtained quantitative interaction data of >100 lectins for >100 PA oligosaccharides.
TL;DR: The proposed MISPE protocol could overcome the drawback of traditional detection methods, which require pre-treatments of the samples, and the possibility to obtain the selective recognition of alpha-TP from natural samples in aqueous mixtures represents one of the main advantages of the materials.
TL;DR: An organic-inorganic hybrid poly-o-toluidine Th(IV) phosphate was chemically synthesized and a cation-exchanger ion-selective membrane electrode was fabricated for the determination of Hg(II) ions in solutions to understand the ion-exchange capabilities.
TL;DR: The reported SPE and RP-HPLC methods were applied to the analysis of 49 authentic honey samples from various floral sources and the results indicate that they may serve with respect to the quantitative control of a number of phenolic acids in plant-derived foods and medicinal plants.
Abstract: The determination of 18 aromatic and arylaliphatic carboxylic acids in honey from different floral origin using solid-phase extraction (SPE) and reversed-phase high performance liquid chromatography (RP-HPLC) is reported. The behaviour of the solutes on SPE cartridges was predicted from preliminary calculations involving the pK(a) constants of the carboxylic groups, the n-octanol:water partition coefficients and the distribution coefficients at different pH values of the conditioning and washing solvents. The proposed SPE isolation and pre-concentration of the acids was achieved on reversed-phase Bond Elut C18 cartridges using an acetonitrile:tetrahydrofuran (1:1, v/v) elution system. RP-HPLC separations were performed on a Spherisorb ODS-2 column using linear gradient elution with a mobile phase composed of 20 mm phosphate buffer (pH 2.92) and methanol, and with UV detection. The reported SPE and RP-HPLC methods were applied to the analysis of 49 authentic honey samples from various floral sources and the results indicate that they may serve with respect to the quantitative control of a number of phenolic acids in plant-derived foods and medicinal plants.
TL;DR: A method using solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the determination of 12 β-blockers and β2-agonists in wastewater samples as discussed by the authors.
TL;DR: A titanium dioxide (TiO2)-packed pipette tip is used as a phosphopeptide trap that acts as an offline first-dimension separation step in a two-dimensional chromatography system that is directly compatible with subsequent analysis by online nano electrospray ionization tandem mass spectrometry.
Abstract: We have developed a new offline chromatographic approach for the selective enrichment of phosphorylated peptides that is directly compatible with subsequent analysis by online nano electrospray ionization tandem mass spectrometry. In this technique, a titanium dioxide (TiO2)-packed pipette tip is used as a phosphopeptide trap that acts as an offline first-dimension separation step in a two-dimensional chromatography system. This is followed by online nano reversed-phase high-performance liquid chromatography. Here, we present suitable methods for enrichment, optimized separately for each step: sample loading, washing and elution from the TiO2-filled tips. To increase the trapping selectivity of the TiO2 column, we used the sodium salt of 1-octanesulfonic acid combined with 2,5-dihydroxybenzoic acid as ion-pairing agents and displacers for acidic peptides. These agents also improve the binding of phosphorylated peptides and block the binding of non-phosphorylated ones. This enrichment procedure takes 30 min, followed by a 100-min HPLC program, including washing and an elution gradient.
TL;DR: It is shown that arginine reduces non-specific protein binding in gel permeation chromatography and facilitates elution of antibodies from Protein-A columns, suggesting its effectiveness as a solvent for elution in HIC and IEC.
TL;DR: The proposed mesoporous titanium dioxide as a novel solid-phase extraction material for flow injection micro-column preconcentration on-line coupled with ICP-OES determination of trace metals in environmental samples has been successfully applied and has been validated using a certified reference material.
TL;DR: A new method to selectively enrich S1P and dihydro-S1P from biological samples by the Fe(3+) gel immobilized metal affinity chromatography (IMAC) coupled with a HPLC-based separation and detection system is described.
TL;DR: A method for the preconcentration of some transition elements at trace level was proposed using a column filled with Amberlite XAD-2000 resin and applied to natural waters and kale vegetable by analysis of certified reference materials.
TL;DR: Effective sample pretreatment procedures based on solid-phase extraction (SPE) for multiresidue determination of seven neonicotinoid insecticides in agricultural products were investigated, and the average recoveries were excellent, with the exception of nitenpyram.
Abstract: Effective sample pretreatment procedures based on solid-phase extraction (SPE) for multiresidue determination of seven neonicotinoid insecticides in agricultural products were investigated. After extraction with acetone and concentration, the insecticides in aqueous sample extracts were transferred into organic solvent phases with a Chem Elut SPE cartridge. Finally, the eluate from the cartridge was cleaned up with a SPE cartridge packed with graphitized carbon black and aminopropyl silica gel, which showed a higher cleanup efficiency than the classical silica gel SPE cartridge. Seven insecticides were separated on a reversed-phase C18 column and a gradient system of methanol and phosphate solution based on high-performance liquid chromatography. The established multiresidue determination has been applied to several artificially spiked agricultural samples, with the result that the average recoveries were excellent, with the exception of nitenpyram. The limit of detection of the method ranged from 0.01 to 0.03 mg/kg for the insecticides.
TL;DR: The analysis of dust samples from private houses and office buildings confirmed the ubiquitous presence of target bacteriocides in these environments.
TL;DR: A comparative study was performed on strong cation-exchangers to investigate the pH dependence, efficiency, binding strength, particle size distribution, static and dynamic capacity, and SEM pictures of chromatographic resins, showing good agreement with experiments with model proteins.
TL;DR: Advantages of subcritical water chromatography include the elimination of hazardous organic solvents used in traditional RPLC, rapid analysis time, improved selectivity, temperature-dependent separation efficiency,Temperature-programmed elution, and compatibility with both gas- and liquid-phase detectors.
Abstract: At temperatures and pressures lower than 374°C and 218 atm, subcritical water has widely tunable properties such as dielectric constant, surface tension, viscosity, and dissociation constant achieved by simply adjusting the temperature with a moderate pressure to keep water in the liquid state. At elevated temperatures, water acts like a weak polar organic solvent. Thus, subcritical water has been used as a green eluent to replace hazardous solvents commonly used as organic modifiers in RPLC. Subcritical water chromatography (SBWC) is capable of separating polar, moderately polar, and even some nonpolar analytes. Most of these low molecular weight solutes are stable at elevated temperatures during a chromatographic run. Some new packing materials are also quite stable and robust at mild temperatures ranging from 80 to 150°C. Advantages of SBWC include the elimination of hazardous organic solvents used in traditional RPLC, rapid analysis time, improved selectivity, temperature-dependent separation efficiency, temperature-programmed elution, and compatibility with both gas- and liquid-phase detectors. In this paper, the technical aspects as well as the applications of SBWC are reviewed. Topics addressed in this review include the unique characteristics of subcritical water, analytes separated by SBWC, packing materials tested for SBWC, the application of GC and LC detection techniques in SBWC, SBWC instrumentation development, temperature effects on SBWC separation, and models developed for separation in SBWC.