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Ziad El Rassi - One of the best experts on this subject based on the ideXlab platform.
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selective precolumn derivatization of fatty acids with the fluorescent tag 6 aminoquinoline and their determination in some food samples by reversed phase Chromatography
Electrophoresis, 2017Co-Authors: Murthy Jonnada, Guadalupe Davilael Rassi, Ziad El RassiAbstract:Fatty acids (FAs) have been selectively derivatized with a fluorescent tag, 6-aminoquinoline (6AQ), which yielded fluorescent FA-6AQ derivatives that have excitation (λexc = 270 nm) and emission (λemi = 495 nm) wavelengths that are farther apart. This precolumn derivatization is characterized by its simplicity occurring at room temperature between the carboxylic acid group of the FA and the amino group of 6AQ in the presence of a nonaqueous soluble carbodiimide coupling agent such as the N,N´-dicyclohexylcarbodiimide. The FAs extracts are readily derivatized in chloroform and can be analyzed without any further sample cleanup that minimizes sample loss. The FA-6AQ derivatives derived from standard FAs as well as from extracted FAs from food samples were separated by reversed phase Chromatography on a homemade naphthyl methacrylate monolithic (NMM) column and C4 silica-based column. While the NMM column provided excellent separation for saturated FA-6AQ derivatives, the C4 silica column was able to separate simultaneously saturated and unsaturated FA-6AQ derivatives. The MNN column permitted the analysis and quantitation of the saturated FA-6AQ derivatives extracted from coconut oil. The C4 column provided the selectivity needed to analyze and quantify saturated and unsaturated derivatized with 6AQ and extracted from meat. The limits of detection and quantitation were 5 and 20 nM, respectively, with a linear dynamic range extending from 20 nM to 40 μM. The 40 μM upper limit was due to the limited solubility of the FA-6AQ derivatives in the diluting mobile phase, which is the initial mobile phase used in gradient runs.
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polar and nonpolar organic polymer based monolithic columns for capillary electroChromatography and high performance liquid Chromatography
Electrophoresis, 2017Co-Authors: Renuka Rathnasekara, Murthy Jonnada, Shantipriya Khadka, Ziad El RassiAbstract:This review article is a continuation of the previous reviews on the area of monolithic columns covering the progress made in the field over the last couple of years from the beginning of the second half of 2014 until the end of the first half of 2016. It summarizes and evaluates the evolvement of both polar and nonpolar organic monolithic columns and their use in hydrophilic interaction LC and CEC and Reversed-Phase Chromatography and RP-CEC. The review article discusses the results reported in a total of 62 references.
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monolithic stationary phases with incorporated fumed silica nanoparticles part ii polymethacrylate based monolithic column with covalently incorporated modified octadecyl fumed silica nanoparticles for reversed phase Chromatography
Journal of Chromatography A, 2016Co-Authors: Cemil Aydogan, Ziad El RassiAbstract:This study is concerned with the incorporation of surface modified fumed silica nanoparticles (FSNPs) into polymethacrylate based monolithic columns for use in reversed phase Chromatography (RPC) of small solutes and proteins. First, FSNPs were modified with 3-(trimethoxysilyl)propylmethacrylate (TMSPM) to yield the "hybrid" methacryloyl fumed silica nanoparticle (MFSNP) monomer. The resulting MFSNP was then mixed with glyceryl monomethacrylate (GMM) and ethylene dimethacrylate (EDMA) in a binary porogenic solvent composed of cyclohexanol and dodecanol, and the in situ copolymerization of MFSNP, GMM and EDMA was performed in a stainless steel column of 4.6 mm i.d. The silanol groups of the hybrid monolith thus obtained were grafted with octadecyl ligands by perfusing the hybrid monolithic column with a solution of 4% w/v of dimethyloctadecylchlorosilane (DODCS) in toluene while the column was maintained at 110°C for 6h (in a heated HPLC oven). One of the originalities of this study was to demonstrate MFSNP as a novel derivatized "hybrid monomer" in making RPC monolithic columns with surface bound octadecyl ligands. In this respect, the RPC behavior of the monolithic column with "covalently" incorporated FNSPs having surface grafted octadecyl ligands was evaluated with alkylbenzenes, aniline derivatives and phenolic compounds. The results showed that the hybrid poly(GMA-EDMA-MFSNP) having surface bound octadecyl ligands exhibited hydrophobic interactions under reversed phase elution conditions. Furthermore, six standard proteins were baseline separated on the column using a 10min linear gradient elution at increasing ACN concentration in the mobile phase at a flow rate of 1.0mL/min using a 10 cm×4.6mm i.d. column. The relative standard deviations (RSDs) for the retention times of the tested solutes were lower than 2.1% and 2.4% under isocratic elution and gradient elution conditions, respectively.
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High Performance Liquid Phase Separation of Glycosides. I. Reversed Phase Chromatography of Cyanogenic Glycosides with UV and Pulsed Amperometric Detection
Journal of Liquid Chromatography & Related Technologies, 1997Co-Authors: Kimberly Wasserkrug, Ziad El RassiAbstract:Abstract High performance liquid Chromatography procedures based on reversed phase Chromatography (RPC) using microparticulate octadecylsilica columns were introduced for the separation and detection of some representative cyanogenic glycosides and their degradation products. Pulsed amperometric detection (PAD) provided relatively low detection limits (10−5-10−7 M) for the cyanogenic glycosides and permitted the detection of those lacking a chromophore in their structures (e.g., linamarin) which could not be detected in the UV even at low wavelength. In addition, the PAD was a more selective method of detection when compared to UV at 200 nm, a wavelength at which the molar absorptivity and in turn the detection sensitivity were relatively high for the chromophoric cyanogenic glycosides. However, and in the presence of acetonitrile in the eluent, the detector response in PAD was linear in concentration range over 2 to 3 orders of magnitude as opposed to 4 to 5 orders of magnitude in the UV. Finally, RPC pr...
Markus Dachtler - One of the best experts on this subject based on the ideXlab platform.
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on line liquid Chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling for the separation and characterization of secoisolariciresinol diglucoside isomers in flaxseed
Journal of Chromatography A, 2002Co-Authors: Jan Fritsche, R Angoelal, Markus DachtlerAbstract:Abstract Two secoisolariciresinol diglucoside (SDG) diastereomers were extracted from flaxseed and liberated through alkaline hydrolysis. Anion-exchange and Reversed-Phase Chromatography were successfully employed to purify the hydrolyzed flaxseed extract. On-line LC–NMR–MS analyses revealed the structure of the isolated and purified SDG diastereomers, [2 R ,2′ R ]-2,3-bis[(4-hydroxy-3-methoxyphenyl)-methyl]-1,4-butanediyl-bis-β-glucopyranoside the predominant flaxseed lignan and [2 R ,2′ S ]-2,3-bis[(4-hydroxy-3-methoxyphenyl)methyl]-1,4-butanediyl-bis-β-glucopyranoside, a previously incompletely characterized minor flaxseed lignan. Circular dichroism (CD) analyses confirmed the presence of two distinguished optically active compounds present in the flaxseed extract.
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on line liquid Chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling for the separation and characterization of secoisolariciresinol diglucoside isomers in flaxseed
Journal of Chromatography A, 2002Co-Authors: Jan Fritsche, R Angoelal, Markus DachtlerAbstract:Two secoisolariciresinol diglucoside (SDG) diastereomers were extracted from flaxseed and liberated through alkaline hydrolysis. Anion-exchange and Reversed-Phase Chromatography were successfully employed to purify the hydrolyzed flaxseed extract. On-line LC-NMR-MS analyses revealed the structure of the isolated and purified SDG diastereomers, [2R,2'R]-2,3-bis[(4-hydroxy-3-methoxyphenyl)-methyl]-1,4-butanediyl-bis-beta-glucopyranoside the predominant flaxseed lignan and [2R,2'S]-2,3-bis[(4-hydroxy-3-methoxyphenyl)methyl]-1,4-butanediyl-bis-beta-glucopyranoside, a previously incompletely characterized minor flaxseed lignan. Circular dichroism (CD) analyses confirmed the presence of two distinguished optically active compounds present in the flaxseed extract.
Simon J Gaskell - One of the best experts on this subject based on the ideXlab platform.
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purification characterization and sequence determination of bmkk4 a novel potassium channel blocker from chinese scorpion buthus martensi karsch
Peptides, 2004Co-Authors: Naixia Zhang, Michael J Chalmers, Simon J GaskellAbstract:The scorpion neurotoxin BmKK4 was purified from the venom of the Chinese scorpion Buthus martensi Karsch by a combination of gel-filtration, ion exchange and reversed phase Chromatography. The primary sequence of BmKK4 was determined using the tandem MS/MS technique and the cDNA database searching as followings: ZTQCQ SVRDC QQYCL TPDRC SYGTC YCKTT (NH(2)). BmKK4 is the first isolated member of a new subfamily alpha-KTx17 of scorpion K(+) toxins.
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purification characterization and sequence determination of bmkk4 a novel potassium channel blocker from chinese scorpion buthus martensi karsch
Peptides, 2004Co-Authors: Naixia Zhang, Michael J Chalmers, Simon J GaskellAbstract:The scorpion neurotoxin BmKK4 was purified from the venom of the Chinese scorpion Buthus martensi Karsch by a combination of get-filtration, ion exchange and reversed phase Chromatography. The primary sequence of BmKK4 was determined using the tandem MS/MS technique and the cDNA database searching as followings: ZTQCQ SVRDC QQYCL TPDRC SYGTC YCKTT (NH2). BmKK4 is the first isolated member of a new subfamily alpha-KTx17 of scorpion K+ toxins. (C) 2004 Elsevier Inc. All rights reserved.
Eric Denoyer - One of the best experts on this subject based on the ideXlab platform.
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high performance liquid Chromatography of selenoamino acids and organo selenium compounds speciation by inductively coupled plasma mass spectrometry
Journal of Chromatography A, 1997Co-Authors: Susan Mary Bird, Honghong Ge, Eric Block, Peter C. Uden, Julian F Tyson, Eric DenoyerAbstract:As part of an ongoing study to identify selenium compounds with cancer chemopreventive activity, extracts of selenium-enriched samples were analyzed by HPLC-inductively coupled plasma (ICP)-MS. Ion-exchange, ion pair and derivatization methods for Reversed-Phase HPLC were considered and advantages and disadvantages for each compared. Anion exchange allows separation of selenite and selenate, but otherwise provides poor separation. Pre-column derivatization and Reversed-Phase Chromatography provides separation of compounds with terminal amine functionalities, but many other species elute in the void volume. The ion pair method gave optimal separation and was compatible with standard ICP-MS operating conditions.
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speciation of selenoamino acids and organoselenium compounds in selenium enriched yeast using high performance liquid Chromatography inductively coupled plasma mass spectrometry
Journal of Analytical Atomic Spectrometry, 1997Co-Authors: Susan Mary Bird, Eric Block, Peter C. Uden, Julian F Tyson, Eric DenoyerAbstract:As part of an ongoing study to identify selenium compounds with cancer chemopreventive activity, selenium-enriched yeast was analyzed by HPLC–ICP-MS. More than twenty selenium-containing species were found in hot water and enzymatic hydrolysis extracts of the yeast. Trifluoroacetic acid was used as an ion-pairing agent in a water–methanol mobile phase with Reversed-Phase Chromatography on an octylsilane stationary phase. The presence of selenocystine, selenomethionine and methylselenocysteine was confirmed by comparative retention of standards. The column efficiency was 8500 theoretical plates and the mobile phase was compatible with standard ICP-MS operating conditions.
Jan Fritsche - One of the best experts on this subject based on the ideXlab platform.
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on line liquid Chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling for the separation and characterization of secoisolariciresinol diglucoside isomers in flaxseed
Journal of Chromatography A, 2002Co-Authors: Jan Fritsche, R Angoelal, Markus DachtlerAbstract:Abstract Two secoisolariciresinol diglucoside (SDG) diastereomers were extracted from flaxseed and liberated through alkaline hydrolysis. Anion-exchange and Reversed-Phase Chromatography were successfully employed to purify the hydrolyzed flaxseed extract. On-line LC–NMR–MS analyses revealed the structure of the isolated and purified SDG diastereomers, [2 R ,2′ R ]-2,3-bis[(4-hydroxy-3-methoxyphenyl)-methyl]-1,4-butanediyl-bis-β-glucopyranoside the predominant flaxseed lignan and [2 R ,2′ S ]-2,3-bis[(4-hydroxy-3-methoxyphenyl)methyl]-1,4-butanediyl-bis-β-glucopyranoside, a previously incompletely characterized minor flaxseed lignan. Circular dichroism (CD) analyses confirmed the presence of two distinguished optically active compounds present in the flaxseed extract.
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on line liquid Chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling for the separation and characterization of secoisolariciresinol diglucoside isomers in flaxseed
Journal of Chromatography A, 2002Co-Authors: Jan Fritsche, R Angoelal, Markus DachtlerAbstract:Two secoisolariciresinol diglucoside (SDG) diastereomers were extracted from flaxseed and liberated through alkaline hydrolysis. Anion-exchange and Reversed-Phase Chromatography were successfully employed to purify the hydrolyzed flaxseed extract. On-line LC-NMR-MS analyses revealed the structure of the isolated and purified SDG diastereomers, [2R,2'R]-2,3-bis[(4-hydroxy-3-methoxyphenyl)-methyl]-1,4-butanediyl-bis-beta-glucopyranoside the predominant flaxseed lignan and [2R,2'S]-2,3-bis[(4-hydroxy-3-methoxyphenyl)methyl]-1,4-butanediyl-bis-beta-glucopyranoside, a previously incompletely characterized minor flaxseed lignan. Circular dichroism (CD) analyses confirmed the presence of two distinguished optically active compounds present in the flaxseed extract.
