The Experts below are selected from a list of 156561 Experts worldwide ranked by ideXlab platform
Heba Elmansi - One of the best experts on this subject based on the ideXlab platform.
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analysis of four antimigraine drugs in two ternary mixtures by sweeping micellar electrokinetic chromatography with retention factor gradient effect and dynamic ph junction
2016Co-Authors: F Belal, Mohie Sharaf K Eldin, M M Tolba, Mohamed I Elawady, Heba ElmansiAbstract:Abstract A new, robust, and reliable sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method with dynamic pH junction and retention factor gradient effect (RFGE) is developed for the simultaneous determination of four different analytes in two ternary mixtures of pharmaceutical importance. The studied analytes are drotaverine hydrochloride and caffeine combined with paracetamol (Mixture-I) or dipyrone (Mixture-II). Different experimental parameters are carefully investigated in order to achieve the highest possible resolution and sensitivity in a short analysis time. A special interest is given to the effect of Sample Matrix composition on the attainable enrichment efficiency with a focus on dynamic pH junction and RFGE. Up to 8 times increase in sensitivity is achieved by the modification of the Sample Matrix. The theoretical considerations of the underlying effects regarding the separation and the enrichment processes are thoroughly discussed. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in their co-formulated or single-ingredient tablet preparations with a total run time of less than 11 min.
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analysis of four antimigraine drugs in two ternary mixtures by sweeping micellar electrokinetic chromatography with retention factor gradient effect and dynamic ph junction
2016Co-Authors: F Belal, Mohie Sharaf K Eldin, M M Tolba, Mohamed I Elawady, Heba ElmansiAbstract:Abstract A new, robust, and reliable sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method with dynamic pH junction and retention factor gradient effect (RFGE) is developed for the simultaneous determination of four different analytes in two ternary mixtures of pharmaceutical importance. The studied analytes are drotaverine hydrochloride and caffeine combined with paracetamol (Mixture-I) or dipyrone (Mixture-II). Different experimental parameters are carefully investigated in order to achieve the highest possible resolution and sensitivity in a short analysis time. A special interest is given to the effect of Sample Matrix composition on the attainable enrichment efficiency with a focus on dynamic pH junction and RFGE. Up to 8 times increase in sensitivity is achieved by the modification of the Sample Matrix. The theoretical considerations of the underlying effects regarding the separation and the enrichment processes are thoroughly discussed. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in their co-formulated or single-ingredient tablet preparations with a total run time of less than 11 min.
David J Miller - One of the best experts on this subject based on the ideXlab platform.
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comparisons of soxhlet extraction pressurized liquid extraction supercritical fluid extraction and subcritical water extraction for environmental solids recovery selectivity and effects on Sample Matrix
2000Co-Authors: Steven B Hawthorne, Carol B Grabanski, Esther Martin, David J MillerAbstract:Abstract Extractions of a polycyclic aromatic hydrocarbon (PAH)-contaminated soil from a former manufactured gas plant site were performed with a Soxhlet apparatus (18 h), by pressurized liquid extraction (PLE) (50 min at 100°C), supercritical fluid extraction (SFE) (1 h at 150°C with pure CO 2 ), and subcritical water (1 h at 250°C, or 30 min at 300°C). Although minor differences in recoveries for some PAHs resulted from the different methods, quantitative agreement between all of the methods was generally good. However, the extract quality differed greatly. The organic solvent extracts (Soxhlet and PLE) were much darker, while the extracts from subcritical water (collected in toluene) were orange, and the extracts from SFE (collected in CH 2 Cl 2 ) were light yellow. The organic solvent extracts also yielded more artifact peaks in the gas chromatography (GC)–mass spectrometry and GC–flame ionization detection chromatograms, especially compared to supercritical CO 2 . Based on elemental analysis (carbon and nitrogen) of the soil residues after each extraction, subcritical water, PLE, and Soxhlet extraction had poor selectivity for PAHs versus bulk soil organic matter (∼1/4 to 1/3 of the bulk soil organic matter was extracted along with the PAHs), while SFE with pure CO 2 removed only 8% of the bulk organic Matrix. Selectivities for different compound classes also vary with extraction method. Extraction of urban air particulate matter with organic solvents yields very high concentrations of n - and branched alkanes (∼ C 18 to C 30 ) from diesel exhaust as well as lower levels of PAHs, and no selectivity between the bulk alkanes and PAHs is obtained during organic solvent extraction. Some moderate selectivity with supercritical CO 2 can be achieved by first extracting the bulk alkanes at mild conditions, followed by stronger conditions to extract the remaining PAHs, i.e., the least polar organics are the easiest organics to extract with pure CO 2 . In direct contrast, subcritical water prefers the more polar analytes, i.e., PAHs were efficiently extracted from urban air particulates at 250°C, with little or no extraction of the alkanes. Finally, recent work has demonstrated that many pollutant molecules become “sequestered” as they age for decades in the environment (i.e., more tightly bound to soil particles and less available to organisms or transport). Therefore, it may be more important for an extraction method to only recover pollutant molecules that are environmentally-relevant, rather than the conventional attempts to extract all pollutant molecules regardless of how tightly bound they are to the soil or sediment Matrix. Initial work comparing SFE extraction behavior using mild to strong conditions with bioremediation behavior of PAHs shows great promise to develop extraction methodology to measure environmentally-relevant concentrations of pollutants in addition to their total concentrations.
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comparisons of soxhlet extraction pressurized liquid extraction supercritical fluid extraction and subcritical water extraction for environmental solids recovery selectivity and effects on Sample Matrix
2000Co-Authors: Steven B Hawthorne, Carol B Grabanski, Esther Martin, David J MillerAbstract:Extractions of a polycyclic aromatic hydrocarbon (PAH)-contaminated soil from a former manufactured gas plant site were performed with a Soxhlet apparatus (18 h), by pressurized liquid extraction (PLE) (50 min at 100 degrees C), supercritical fluid extraction (SFE) (1 h at 150 degrees C with pure CO2), and subcritical water (1 h at 250 degrees C, or 30 min at 300 degrees C). Although minor differences in recoveries for some PAHs resulted from the different methods, quantitative agreement between all of the methods was generally good. However, the extract quality differed greatly. The organic solvent extracts (Soxhlet and PLE) were much darker, while the extracts from subcritical water (collected in toluene) were orange, and the extracts from SFE (collected in CH2Cl2) were light yellow. The organic solvent extracts also yielded more artifact peaks in the gas chromatography (GC)-mass spectrometry and GC-flame ionization detection chromatograms, especially compared to supercritical CO2. Based on elemental analysis (carbon and nitrogen) of the soil residues after each extraction, subcritical water, PLE, and Soxhlet extraction had poor selectivity for PAHs versus bulk soil organic matter (approximately 1/4 to 1/3 of the bulk soil organic matter was extracted along with the PAHs), while SFE with pure CO2 removed only 8% of the bulk organic Matrix. Selectivities for different compound classes also vary with extraction method. Extraction of urban air particulate matter with organic solvents yields very high concentrations of n- and branched alkanes (approximately C18 to C30) from diesel exhaust as well as lower levels of PAHs, and no selectivity between the bulk alkanes and PAHs is obtained during organic solvent extraction. Some moderate selectivity with supercritical CO2 can be achieved by first extracting the bulk alkanes at mild conditions, followed by stronger conditions to extract the remaining PAHs, i.e., the least polar organics are the easiest organics to extract with pure CO2. In direct contrast, subcritical water prefers the more polar analytes, i.e., PAHs were efficiently extracted from urban air particulates at 250 degrees C, with little or no extraction of the alkanes. Finally, recent work has demonstrated that many pollutant molecules become "sequestered" as they age for decades in the environment (i.e., more tightly bound to soil particles and less available to organisms or transport). Therefore, it may be more important for an extraction method to only recover pollutant molecules that are environmentally-relevant, rather than the conventional attempts to extract all pollutant molecules regardless of how tightly bound they are to the soil or sediment Matrix. Initial work comparing SFE extraction behavior using mild to strong conditions with bioremediation behavior of PAHs shows great promise to develop extraction methodology to measure environmentally-relevant concentrations of pollutants in addition to their total concentrations.
Shigeru Terabe - One of the best experts on this subject based on the ideXlab platform.
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simple on line Sample preconcentration technique for peptides based on dynamic ph junction in capillary electrophoresis mass spectrometry
2007Co-Authors: Koshi Imami, Maria Rowena N Monton, Yasushi Ishihama, Shigeru TerabeAbstract:We report an on-line Sample preconcentration technique based on dynamic pH junction in capillary electrophoresis-mass spectrometry (CE-MS). For peptide analysis, the Samples were dissolved in a solution with higher pH than the background solution (BGS), and were injected into the capillary as a long plug. The pH difference between the Sample Matrix and BGS caused changes in analytes' mobilities during electrophoresis, resulting in narrowing of their bands at the boundary. Around 550-1000-fold sensitivity enhancement could be achieved in terms of peak intensity without degrading peak shape and resolution. This technique is easy to perform and will be useful for peptide mass fingerprinting in protein analysis.
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sweeping concentration mechanism and applications to high sensitivity analysis in capillary electrophoresis
2002Co-Authors: Joselito P Quirino, Jongbok Kim, Shigeru TerabeAbstract:Sweeping in capillary electrophoresis (CE) involves the interaction of a pseudostationary phase (PS) in the separation solution and a Sample in the Matrix that is free of the PS used. The PS includes not only the PSs employed in electrokinetic chromatography, but also complexation reagents such as borate. The Sample Matrix could have a lower, similar, or higher conductance than the separation solution. Thus, the basic condition for sweeping is a Sample Matrix free of the additive. The accumulation of analyte molecules during the interaction makes this interesting phenomenon very useful as an on-line preconcentration method for CE. Preconcentration occurs due to chromatographic partitioning, complexation, or any interaction between analytes and PS. Contact between analyte and PS is facilitated by the action of electrophoresis and is independent of electroosmosis. The analyte, PS, or both should have electrophoretic velocities when an electric field is applied. The extent of preconcentration is dictated by the strength of the interaction involved. From tens to several thousand-fold improvements in detector response for many neutral and charged analytes have been achieved with this technique, suggesting sweeping as a general approach to on-line preconcentration in CE. The mechanism and applications of the sweeping phenomenon under different experimental conditions are discussed in this review, with particular emphasis on a better understanding of the sweeping mechanism under reduced electric field (high conductivity) in the Sample zone.
F Belal - One of the best experts on this subject based on the ideXlab platform.
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analysis of four antimigraine drugs in two ternary mixtures by sweeping micellar electrokinetic chromatography with retention factor gradient effect and dynamic ph junction
2016Co-Authors: F Belal, Mohie Sharaf K Eldin, M M Tolba, Mohamed I Elawady, Heba ElmansiAbstract:Abstract A new, robust, and reliable sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method with dynamic pH junction and retention factor gradient effect (RFGE) is developed for the simultaneous determination of four different analytes in two ternary mixtures of pharmaceutical importance. The studied analytes are drotaverine hydrochloride and caffeine combined with paracetamol (Mixture-I) or dipyrone (Mixture-II). Different experimental parameters are carefully investigated in order to achieve the highest possible resolution and sensitivity in a short analysis time. A special interest is given to the effect of Sample Matrix composition on the attainable enrichment efficiency with a focus on dynamic pH junction and RFGE. Up to 8 times increase in sensitivity is achieved by the modification of the Sample Matrix. The theoretical considerations of the underlying effects regarding the separation and the enrichment processes are thoroughly discussed. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in their co-formulated or single-ingredient tablet preparations with a total run time of less than 11 min.
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analysis of four antimigraine drugs in two ternary mixtures by sweeping micellar electrokinetic chromatography with retention factor gradient effect and dynamic ph junction
2016Co-Authors: F Belal, Mohie Sharaf K Eldin, M M Tolba, Mohamed I Elawady, Heba ElmansiAbstract:Abstract A new, robust, and reliable sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method with dynamic pH junction and retention factor gradient effect (RFGE) is developed for the simultaneous determination of four different analytes in two ternary mixtures of pharmaceutical importance. The studied analytes are drotaverine hydrochloride and caffeine combined with paracetamol (Mixture-I) or dipyrone (Mixture-II). Different experimental parameters are carefully investigated in order to achieve the highest possible resolution and sensitivity in a short analysis time. A special interest is given to the effect of Sample Matrix composition on the attainable enrichment efficiency with a focus on dynamic pH junction and RFGE. Up to 8 times increase in sensitivity is achieved by the modification of the Sample Matrix. The theoretical considerations of the underlying effects regarding the separation and the enrichment processes are thoroughly discussed. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in their co-formulated or single-ingredient tablet preparations with a total run time of less than 11 min.
Lan Ding - One of the best experts on this subject based on the ideXlab platform.
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preparation of magnetic strong cation exchange resin for the extraction of melamine from egg Samples followed by liquid chromatography tandem mass spectrometry
2010Co-Authors: Ligang Chen, Qinglei Zeng, Hui Wang, Xiaopan Zhang, Lei Sun, Qi Zhao, Lan DingAbstract:Abstract In the work, magnetic strong cation exchange (MSCX) resins were prepared using hydrophobic Fe 3 O 4 magnetite as the magnetically susceptible component, styrene and divinylbenzene as polymeric Matrix components, acetyl sulfonate as the sulfonation agent. The resins were successfully applied to the extraction of melamine (MEL) from egg Samples. The extraction procedure was carried out in a single step by blending and stirring the Sample, extraction solvent and the magnetic resins. The MEL was extracted from the Sample Matrix then adsorbed onto the resins directly through ion-exchange interaction. When the extraction was completed, the resins with adsorbed analyte were easily separated from the Sample Matrix by applying an appropriate magnetic field. Main factors affecting the extraction of MEL such as the amount of MSCX resins, extraction time, washing and eluting conditions were optimized. The MEL eluted from the resins was determined by liquid chromatography–tandem mass spectrometry. The linearity of quantification obtained by analyzing Matrix-matched standards is in the range of 10–1000 ng g −1 . The limit of detection and quantification obtained are 2.6 and 8.8 ng g −1 , respectively. The relative standard deviations of intra- and inter-day ranging from 1.6% to 6.5% and from 2.1% to 7.2% are obtained. The recoveries of MEL are in the range of 77.2–99.3%. The proposed method was successfully applied to determine MEL in eggs obtained from different local markets. MEL was detectable with the contents of 43.5 and 234.1 ng g −1 in two Samples.
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preparation of magnetic molecularly imprinted polymer for the separation of tetracycline antibiotics from egg and tissue Samples
2009Co-Authors: Ligang Chen, Jun Liu, Qinglei Zeng, Hui Wang, Hanqi Zhang, Lan DingAbstract:Abstract Magnetic molecularly imprinted polymers were prepared using hydrophobic Fe3O4 magnetite as the magnetically susceptible component, oxytetracycline as template molecule, methacrylic acid as functional monomer, and styrene and divinylbenzene as polymeric Matrix components. The polymers were applied to the separation of tetracycline antibiotics from egg and tissue Samples. The extraction and clean-up procedures were carried out in a single step by blending and stirring the Sample, extraction solvent and polymers. The analytes can be transferred from the Sample Matrix to the polymers directly or through the extraction solvent as medium. When the extraction was complete, the polymers adsorbing the analytes were easily separated from the Sample Matrix by an adscititious magnet. The analytes eluted from the polymers were determined by liquid chromatography–tandem mass spectrometry. The recoveries ranging from 72.8% to 96.5% were obtained with relative standard deviations in the range of 2.9–12.3%. The limit of detection was less than 0.2 ng g−1. The feasibility of this method was validated by analysis of incurred egg and tissue Samples, and the results were compared with those obtained by the classical method in which solvent extraction, centrifugation, and subsequent clean-up and concentration by solid-phase extraction were applied. The proposed method reduced the complicacy of classical method and improved the reliability of method.
