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At least 289 records · Page 16Linked to original sources
PubMed2004

Determination of residues of UV filters in natural waters by solid-phase extraction coupled to liquid chromatography-photodiode array detection and gas chromatography-mass spectrometry.

This study describes a procedure for the enrichment, separation and quantification of four major UV filters in natural waters. Solid-phase extraction combined with liquid chromatography and photodiode array detection (LC-UV-DAD), and gas chromatography with mass spectroscopy (GC-MS) were employed for the analyses. LC of the four compounds with surfactant-modified hydro-organic eluents gave satisfactory resolution of overlapping peaks. In GC, a significant improvement of the detection limits was attained, but only three compounds could be detected. The method was validated for, and applied to, various water samples prone to UV filter accumulation due to recreational activities. Recoveries from real samples were 86-99% with LOQs as low as 0.5 ng/l depending on the sample volume and the analytical procedure.

Chromatography, Liquid↗
PubMed2004

Evaluation of fast gas chromatography and gas chromatography-mass spectrometry in the analysis of lipids.

Fast and conventional gas chromatography (GC) techniques were applied to nine different lipidic matrices (butter, lard, tallow, and peanut, corn, sunflower, soya, olive, menhaden oils). Simultaneous methylic transesterification was performed on all samples prior to GC analysis. Several practical aspects concerning high speed analysis were investigated, such as the great increase in linear velocity, the use of fast temperature ramps, column sample capacity and detection systems. Analytical results showed certain losses in resolution, balanced by a consistent reduction in analysis time. The actual time savings were variable (60-70 min) as they were dependent on the complexity of the sample while the speed enhancement factor was equal to 10.5. Peak identification was achieved by means of different information sources, such as fast GC-mass spectrometry (MS), linear retention indices and comprehensive two-dimensional (2D) gas chromatography group patterns. The method developed was shown to be applicable in routine applications on complex natural samples.

Chromatography, Gas↗
PubMed2004

Identification of iso- and n-propylphosphonates using liquid chromatography-tandem mass spectrometry and gas chromatography-Fourier transform infrared spectroscopy.

Organophosphorus nerve agents and their precursors, specifically listed in the schedules of chemicals in the Annex to the Chemical Weapons Convention (CWC), include analogues with C1-C3 alkyl groups on phosphorus. The Organisation for the Prohibition of Chemical Weapons (OPCW) requires designated laboratories to unequivocally identify isomeric propyl groups bonded to phosphorus in analytes that may be present in samples submitted for analysis. Homologous series of isomeric pairs of dialkyl iso- and n-propylphosphonates, alkyl iso- and n-propylphosphonochloridates, and alkyl iso- and n-propylphosphonofluoridates, have been analysed by liquid chromatography-ion trap tandem mass spectrometry and/or by gas chromatography-Fourier transform infrared spectroscopy. The results show that P-propyl isomers can be reliably differentiated by collision induced dissociation (CID) of selected fragment ions and by their infrared P=O stretching and C-H deformation frequencies.

Chromatography, Gas↗
PubMed2004

Gel permeation chromatography followed by pyrolysis-gas chromatography-mass spectrometry via a solvent-evaporative interface.

The measurement of chemical composition as a function of molecular weight has always been a challenge for analytical chemists. In this paper, we present a unique way to combine gel permeation chromatography (GPC) with pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) for this purpose. A commercially available solvent-evaporative interface, originally designed for GPC-IR measurements, was used to deposit the eluent of GPC onto aluminum foil. Small strips of aluminum foil were cut and subjected to Py-GC-MS analysis. Compared with the GPC-IR measurements, the proposed technique offers the advantage of being able to distinguish between structurally similar monomers in a complex copolymer. As an example, a copolymer composed of four monomers was analyzed. The results clearly demonstrate that this technique can be applied to complex polymeric systems to yield information regarding chemical heterogeneity versus molecular weight.

Chromatography, Gel↗
PubMed2005

Strategy for metabonomics research based on high-performance liquid chromatography and liquid chromatography coupled with tandem mass spectrometry.

Metabonomics, the study of metabolites and their roles in various disease states, is a novel methodology arising from the post-genomics era. This methodology has been applied in many fields. Current metabonomic practice has relied on mass spectrometry (MS), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR) to analyze metabolites. In this study, a strategy was developed for applying high-performance liquid chromatography (HPLC) and LC-MS-MS to metabonomics research. One of the key problems to be solved in this strategy is to match the peaks between the chromatograms. A peak alignment algorithm has been developed to match the chromatograms before the pattern recognition. As an application example, the strategy described above was applied to metabonomics research on liver diseases, and the false-positive result of live cancer diagnosis from the hepatocirrhosis and hepatitis diseases was effectively reduced to 7.40%. Based on the pattern recognition, several potential biomarkers were found and further identified by the following LC-MS-MS experiments. The structures of eight potential biomarkers were given for distinguishing the liver cancer from the hepatocirrhosis and hepatitis diseases.

Adult↗
PubMed2005

Affinity chromatography with monolithic capillary columns. II. Polymethacrylate monoliths with immobilized lectins for the separation of glycoconjugates by nano-liquid affinity chromatography.

Monolithic capillary columns with surface bound lectin affinity ligands were introduced for performing lectin affinity chromatography (LAC) by nano-liquid chromatography (nano-LC). Two kinds of polymethacrylate monoliths were prepared, namely poly(glycidyl methacrylateco-ethylene dimethacrylate) and poly(glycidyl methacrylate-co-ethylene dimethacrylate-co-[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride) to yield neutral and cationic macroporous polymer, respectively. Two lectins including concanavalin (Con A) and wheat germ agglutinin (WGA) were immobilized onto the monolithic capillary columns. The neutral monoliths with immobilized lectins exhibited lower permeability under pressure driven flow than the cationic monoliths indicating that the latter had wider flow-through pores than the former. Both types of monoliths with immobilized lectins exhibited strong affinity toward particular glycoproteins and their oligosaccharide chains (i.e., glycans) having sugar sequences recognizable by the lectin. Due to the strong binding affinity, the monoliths with surface bound lectins allowed the injection of relatively large volume (i.e., several column volumes) of dilute samples of glycoproteins and glycans thus allowing the concentration of the glycoconjugates and their subsequent isolation and detection at low levels (approximately 10(-8) M). To further exploit the lectin monoliths in the isolation of glycoconjugates, two-dimensional separation schemes involving LAC in the first dimension and reversed-phase nano-LC in the second dimension were introduced. The various interrelated methods established in this investigation are expected to play a major role in advancing the sciences of "nano-glycomics".

Chromatography, Affinity↗
PubMed2006

Comparison of ultra-performance liquid chromatography and high-performance liquid chromatography for the determination of priority pesticides in baby foods by tandem quadrupole mass spectrometry.

Determination of 16 priority pesticides and transformation products specified in the EU Baby Food Directive 2003/13/EC has been compared using high-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography (UPLC) coupled to tandem quadrupole mass spectrometry (MS/MS). Prior to analysis, co-extractives were removed from acetonitrile extracts using dispersive solid-phase extraction (SPE) with primary secondary amine (50 mg). Extracts spiked with pesticides at 1 microg kg(-1) yielded average recoveries in the range 85-119%, with relative standard deviations less than 17%. The HPLC-MS/MS and UPLC-MS/MS multi-residue methods developed are simple, rapid and suitable for the quantification and confirmation of the 16 priority pesticides in fruit-, potato- and cereal-based baby food at 1 microg kg(-1). The major advantages of UPLC, using 1.7 microm particles, over HPLC are the speed of analysis, the narrower peaks (giving increased signal-to-noise ratio) and improved confirmation for the targeted pesticides in the analyses of baby foods.

Chromatography, High Pressure Liquid↗
PubMed2006

Two-dimensional capillary liquid chromatography: pH gradient ion exchange and reversed phase chromatography for rapid separation of proteins.

In the present work, an orthogonal two-dimensional (2D) capillary liquid chromatography (LC) method for fractionation and separation of proteins using wide range pH gradient ion exchange chromatography (IEC) in the first dimension and reversed phase (RP) in the second dimension, is demonstrated. In the first dimension a strong anion exchange (SAX) column subjected to a wide range (10.5-3.5) descending pH gradient was employed, while in the second dimension, a large pore (4,000 A) polystyrene-divinylbenzene (PS-DVB) RP analytical column was used for separation of the protein pH-fractions from the first dimension. The separation power of the off-line 2D method was demonstrated by fractionation and separation of human plasma proteins. Seventeen pH-fractions were manually collected and immediately separated in the second dimension using a column switching capillary RP-LC system. Totally, more than 200 protein peaks were observed in the RP chromatograms of the pH-fractions. On-line 2D analysis was performed for fractionation and separation of ten standard proteins. Two pH-fractions (basic and acidic) from the first dimension were trapped on PS-DVB RP trap columns prior to back-flushed elution onto the analytical RP column for fast separation of the proteins with UV/MS detection.

Animals↗
PubMed2006

Apolar chromatography on Sephadex LH-20 combined with high-speed counter-current chromatography. High yield strategy for structurally closely related analytes-Destruxin derivatives from Metarhizium anisopliae as a case study.

A novel high yield isolation procedure for lipophilic cyclic peptide derivatives is presented. Destruxin (dtx) A, B, D, E, and E-diol retrieval from Metarhizium anisopliae culture broth was achieved with a three-step purification protocol. After liquid-liquid extraction column chromatography over Sephadex LH-20 served as enrichment step. High-speed counter-current chromatography (HSCCC) was used for the final purification. Within the first chromatographic step dtx D and dtx E-diol were separated in purities exceeding 90%. The separation of dtx A, B, and E was achieved from an enriched Sephadex LH-20 fraction by a HSCCC protocol using light petroleum-ethyl acetate-methanol-water = 2:5:2:5 (v/v) as eluent system. These derivatives were obtained in purities above 98% and total yields exceeding 40%.

Ascomycota↗
PubMed2006

Collaborative trial validation study of two methods, one based on high performance liquid chromatography-tandem mass spectrometry and on gas chromatography-mass spectrometry for the determination of acrylamide in bakery and potato products.

A European inter-laboratory study was conducted to validate two analytical procedures for the determination of acrylamide in bakery ware (crispbreads, biscuits) and potato products (chips), within a concentration range from about 20 microg/kg to about 9000 microgg/kg. The methods are based on gas chromatography-mass spectrometry (GC-MS) of the derivatised analyte and on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) of native acrylamide. Isotope dilution with isotopically labelled acrylamide was an integral part of both methods. The study was evaluated according to internationally accepted guidelines. The performance of the HPLC-MS/MS method was found to be superior to that of the GC-MS method and to be fit-for-the-purpose.

Acrylamide↗
PubMed2006

Determination of fragrance allergens in cosmetics by size-exclusion chromatography followed by gas chromatography-mass spectrometry.

A method using size-exclusion chromatography (SEC) combined with gas chromatography-mass spectrometry (GC-MS) was developed for the quantitation of 24 restricted allergenic fragrance compounds in cosmetic samples. To achieve reproducible results fragrance calibration has to be performed with propyl acetate as a solvent containing a constant proportion of matrix components. With the exception of hydroxycitronellal (66+/-5%) all compounds showed good recovery rates in the range of 90-120%. The mean accuracy (relative error) was 1+/-10% for all 24 compounds in five spiked creams (10 mg/kg per allergen) and 8+/-34% in a reference sample (4-15 mg/kg). The biggest benefit compared to other methods is the flexible clean up with SEC which allows the determination of a large range of compounds in difficult matrices with GC-MS.

Allergens↗
PubMed2006

Identification and quantification of the constituents of madder root by gas chromatography and high-performance liquid chromatography.

The possibilities in the identification and quantitation of the constituents of Rubia tinctorum L.'s root, called also madder root, was described and compared by gas chromatography (GC)-MS, high-performance liquid chromatography (HPLC)-UV/photodiode array detection (DAD) and HPLC-MS: chromatographic analyses were carried out in parallel, from the same samples/extracts/hydrolyzates. Anthraquinone glycosides, anthraquinones, carboxylic acids and sugars were determined directly in the presence of the matrix and in its extracts without and subsequently to hydrolyses. Hydrolyses were performed as a function of time, with hydrochloric and trifluoroacetic acids, as well as enzymatically. Data revealed that as hydrolyzing agent trifluoroacetic acid is to be preferred. Madder root's anthraquinones (pseudopurpurin/purpurin, alizarin, lucidin, munjistin, nordamnacanthal) were identified on the basis of their absorption spectra (HPLC-DAD) and fragmentation patterns by GC-MS and HPLC-MS, equally. Reproducibility of anthraquinone's quantitation, by HPLC-DAD and GC-MS, in the concentration ranges of 4 x 10(-5) to 3 x 10(-2)g/g dried sample, provided an average reproducibility of 4.2% (varying between 0.9 and 9.4% relative standard deviation (RSD percentages)). Carboxylic acids (malic, citric, quinic, rosmarinic acids) and saccharides (xylose, ribose, fructose, glucose, sucrose, primverose) were quantified as their trimethylsilyl (oxime) ether/ester derivatives by GC-MS, in the concentration ranges of 10(-5)g to 10(-2)g/g dried sample, with an average reproducibility of 4.7% RSD.

Anthraquinones↗
PubMed2006

High-throughput quantification of lincomycin traces in fermentation broth of genetically modified Streptomyces spp. Comparison of ultra-performance liquid chromatography and high-performance liquid chromatography with UV detection.

A new separation and quantification method using ultra-performance liquid chromatography (UPLC) with UV detection was developed for detection of lincomycin traces in fermentation broth of different Streptomyces spp. A similar high-performance liquid chromatography (HPLC) protocol was simultaneously developed for comparison purposes. Both methods were validated and showed a linear range of detector response for quantification of lincomycin in concentration from 3.125 to 1000.0 microgml(-1) with correlation coefficient 0.999 and recoveries ranging from 81.5 to 89.85% with precision < or =5%. Compared with the HPLC, the UPLC method offered high sample throughput and about 10 times lower consumption of solvents. The developed assays were used for determination of lincomycin production in genetically manipulated production strain Streptomyces lincolnensis and for determination of lincomycin production after heterologous expression of lincomycin biosynthetic gene cluster in non-producing strain Streptomyces coelicolor.

Chromatography, High Pressure Liquid↗
PubMed2006

On-line size exclusion chromatography-pyrolysis-gas chromatography-mass spectrometry for copolymer characterization and additive analysis.

On-line coupled size exclusion chromatography-pyrolysis gas chromatography mass spectrometry (SEC-Py-GC-MS) is studied as a novel tool for the characterization of complex polymer samples. An automated system for on-line SEC-Py-GC-MS allowing transfer of multiple fractions was developed based on stop-flow operation of the SEC dimension, syringe-based transfer of the SEC fraction to the GC instrument and solvent elimination with subsequent pyrolysis in a programmed temperature vaporization (PTV) injector. After optimization the system was applied to the characterization of a complex terpolymer composed of very similar monomers. The use of the system for combined pyrolysis and additive analyses in polycarbonate was also demonstrated. Results obtained with the new method indicate the interesting potentials of the method for detailed characterization of polymeric materials.

Chromatography, Gel↗
PubMed2005

Estimation of the effect of the acidosis and alkalosis on the anesthetic potency of local anesthetics by biopartitioning micellar chromatography and micellar electrokinetic chromatography.

Local anesthetics are hydrophobic compounds and weak bases with protonation constants ranged between 7.5 and 8.8. These drugs block reversibly nerve conduction near their site of application or injection and thus produce temporary loss of feeling or sensation in a limited area of the body. The efficacy of anesthetic blockade of local anesthetics depends on the charged/uncharged form ratio and the hydrophobicity of the compounds. In addition their toxicological effects have been reported to be highly dependent on the physiological pH. Biopartitioning micellar chromatography (BMC) and micellar electrokinetic chromatography (MEKC), that use micellar solutions as mobile phases, have proven to be useful for describing the biological behavior of different kind of compounds. In this paper, relationships between the retention data in BMC and MEKC using Brij35 as surfactant (at pH 7.4) and some pharmacodynamic parameters of local anesthetics are obtained. These models are compared with those obtained using an immobilized artificial column (IAM). Finally, the effect of the corporal pH in situations of acidosis and alkalosis on the pharmacological and toxicological properties of local anesthetics is studied using the retention of compounds in BMC at different mobile phase pH values.

Acidosis↗
PubMed2005

Development of simultaneous gas chromatography-mass spectrometric and liquid chromatography-electrospray ionization mass spectrometric determination method for the new designer drugs, N-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP) and their main metabolites in urine.

To prove the intake of recently controlled designer drugs, N-benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (TFMPP), a simple, sensitive and reliable method which allows us to simultaneously detect BZP, TFMPP and their major metabolite in human urine has been established by coupling gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). GC-MS accompanied by trifluoroacetyl (TFA) derivatization and LC-MS analyses were performed after the enzymatic hydrolysis and the solid phase extraction with OASIS HLB, and BZP, TFMPP and their major metabolites, 4'-hydroxy-BZP (p-OH-BZP), 3'-hydroxy-BZP (m-OH-BZP) and 4'-hydroxy-TFMPP (p-OH-TFMPP), have found to be satisfactorily separated on a semi-micro SCX column with acetonitrile-40 mM ammonium acetate buffer (pH 4) (75:25, v/v) as the eluent. The detection limits produced by GC-MS were estimated to be from 50 ng/ml to 1 microg/ml in the scan mode, and from 200 to 500 ng/ml in the selected ion monitoring (SIM) mode. Upon applying the LC-ESI-MS technique, the linear calibration curves were obtained by using the SIM mode for all analytes in the concentration range from 10 ng/ml to 10 microg/ml. The detection limits ranged from 5 to 40 ng/ml in the scan mode, and from 0.2 to 1 ng/ml in the SIM mode. These results indicate the high reliability and sensitivity of the present procedure, and this procedure will be applicable for proof of intake of BZP and TFMPP in forensic toxicology.

Animals↗
PubMed2006

Immunoaffinity chromatography of abscisic acid combined with electrospray liquid chromatography-mass spectrometry.

Polyclonal antibodies with high specificity for C1-immobilised (+)-cis,trans-abscisic acid (ABA) were raised, characterised by enzyme-linked immunosorbent assay (ELISA) and used for preparation of an immunoaffinity chromatography (IAC) gel. The detection limit of the ELISA was approximately 4.6x10(-10)mol/L. Sensitive electrospray liquid chromatography-mass spectrometry (LC-ESI-MS) methods were also developed with detection limits below 0.1x10(-12)mol. The IAC allowed quick, single-step processing of samples prior to the analyses. The LC-ESI-MS and LC-ELISA techniques were used for comparative estimation of endogenous ABA levels in immunoaffinity purified extracts of normal and water-stressed Nicotiana tabacum L. leaves. The analytical approaches were validated using deuterium- and tritium-labelled internal standards, respectively. The IAC method was found to be highly effective, sensitive and convenient for isolating the target analyte from plant material.

Abscisic Acid↗
PubMed2004

Micellar electrokinetic capillary chromatography, high performance liquid chromatography and nuclear magnetic resonance--three orthogonal methods for characterization of critical drugs.

Purity assessment of multicomponent drugs such as aminoglycoside antibiotics is still a challenge. For example, the high performance liquid chromatography (HPLC) method reported in the European Pharmacopoeia for gentamicin suffers from various disadvantages, i.e. missing robustness, long retention times and broad peaks. Previously an effective and robust micellar electrokinetic chromatography (MEKC) method has been described which is capable of separating all components and impurities. Since a couple of gentamicin lots collected from international markets showed a high number and high quantities of impurities NMR spectroscopy as a primary analytical method was applied in order to validate the quantification results obtained from MEKC. In this study NMR spectroscopy was found to be a very good orthogonal and complementary method.

Chromatography, High Pressure Liquid↗