bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dual opposite injection electrokinetic chromatography: Nonionic microemulsion pseudostationary phase and novel approach to electrokinetic sampling bias
Authors: Zhou Marilyn X. , Foley Joe P. 
Published: February 2004

AbstractDual opposite injection capillary electrophoresis (DOI‐CE) is a family of CE techniques in which the sample is introduced into both ends of the capillary. For the analysis of compounds with widely varying pKa values using a voltage‐driven separation scheme, DOI‐CE is superior to conventional CE with sample introduction at only one end of the capillary due to DOI‐CE's broader elution window. To enhance the DOI‐CE separation, a running buffer with a microemulsion system was developed. Since DOI‐CE works best under conditions of low electroosmotic flow (EOF), the suppression of EOF via the addition of a multiply charged cation (e.g., Zn2+) to the buffer was investigated, and was found to suppress the EOF effectively at moderate concentrations (2.5–10 mM). Three different dual opposite injection modes were studied: simultaneous electrokinetic injection, sequential electrokinetic injection, and sequential hydrodynamic injection. The injection bias in the first two electrokinetic injection modes was compared with the sequential hydrodynamic injection. Corrections in the bias of the electrokinetic injections were discussed, and an improved approach was suggested. Finally, the effect of the relative concentration of the multiply charged cation in the sample plug and running buffer on the peak shape of co‐electroosmotic and counter‐electroosmotic ions was examined, and found to be much more influential on the latter.
Determination of basic pharmaceuticals in human serum by hydrophilic interaction capillary electrochromatography
Authors: Fu Hongjing , Jin Wenhai , Xiao Hua , Xie Chuanhui , Guo Baochuan , Zou Hanfa 
Published: February 2004

AbstractHydrophilic interaction capillary electrochromatography (HI‐CEC) for the determination of basic pharmaceuticals spiked in human serum is described. The organic modifier content, ionic strength, and pH value of the mobile phase as well as the applied voltage are optimized for separation and elution of these drug analytes. Excellent separation was achieved for drugs using a mobile phase composition of 80% v/v acetonitrile in 100 mM triethylamine phosphate (TEAP) buffer at pH 2.8 with column efficiencies for analytes more than 200 000 plates/m. The samples of human serum spiked with basic drugs were directly injected after a simple acetonitrile treatment. The linear range and reproducibility of these basic drugs using an external and internal standard method were compared. As a result, the reproducibility could be greatly improved by using the internal standard method. Good calibration curves with regression coefficients more than 0.998 in the range of 5–160 μg/mL were observed with the internal standard method. The limits of quantitation, based on standards with acceptable relative standard deviations (RSDs), were below 5 μg/mL. The intra‐ and inter‐day precisions, determined as RSDs, were less than 4.57%.
Stir bar sorptive extraction‐liquid desorption applied to the analysis of hop‐derived bitter acids in beer by micellar electrokinetic chromatography
Authors: De Villiers André , Vanhoenacker Gerd , Lynen Fréderic , Sandra Pat 
Published: February 2004

AbstractStir bar sorptive extraction‐liquid desorption (SBSE‐LD) has been applied as an efficient sample preparation method for the analysis of beer bitter acids. Extracts free of almost all interfering compounds were obtained, allowing simultaneous analysis of iso‐α‐acids and reduced iso‐α‐acids. A robust micellar electrokinetic chromatography (MEKC) method was developed that enables fast separation of iso‐α‐acids and reduced iso‐α‐acids. Quantitative data are in good agreement with results obtained by high‐performance liquid chromatography (HPLC) using direct beer injection.
Polymeric sulfated surfactants with varied hydrocarbon tail: I. Synthesis, characterization, and application in micellar electrokinetic chromatography
Authors: Akbay Cevdet , Shamsi Shahab A. 
Published: February 2004

AbstractThe influence of surfactant hydrocarbon tail on the solute/pseudostationary phase interactions was examined. Four anionic sulfated surfactants with 8‐, 9‐, 10‐, and 11‐carbon chains having a polymerizable double bond at the end of the hydrocarbon chain were synthesized and characterized before and after polymerization. The critical micelle concentration (CMC), polarity, and aggregation number of the four sodium alkenyl sulfate (SAlS) surfactants were determined using fluorescence spectroscopy. The partial specific volume of the polymeric SAlS (poly‐SAlS) surfactants was estimated by density measurements and capillary electrophoresis (CE) was employed for determination of methylene selectivity as well as for elution window. The CMC of the monomers of SAlS surfactants decrease with increase in chain length and correlated well when fluorescence method was compared to CE. The physicochemical properties (partial specific volume, methylene selectivity, electrophoretic mobility, and elution window) increased with an increase in chain length. However, no direct relationship was found between the aggregation number and the length of hydrophobic tail of poly‐SAlS surfactants. These polymeric surfactants were then used as pseudostationary phases in micellar electrokinetic chromatography (MEKC) to study the retention behavior and selectivity factor of 36 benzene derivatives with different chemical characteristics. Although variation in chain length of the polymeric surfactants significantly affects the retention of nonhydrogen bonding (NHB) benzene derivatives, these effects were less pronounced for hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) benzene derivatives. Therefore, hydrophobicity of poly‐SAlS surfactants was found to be a major driving force for retention of NHB derivatives. However, for several benzene derivatives (NHB, HBA, and HBD) significantly higher selectivity factor was observed with longest chain polymeric surfactant (e.g., poly(sodium 10‐undecenyl sulfate), poly‐SUS) compared to shorter chain polymeric surfactant (e.g., poly(sodium 7‐octenyl sulfate), poly‐SOcS). In addition, the effect of the surfactant hydrophobic chain was also found to have some impact on migration order of NHB, HBA, and HBD benzene derivatives.
Polymeric sulfated surfactants with varied hydrocarbon tail: II. Chemical selectivity in micellar electrokinetic chromatography using linear solvation energy relationships study
Authors: Akbay Cevdet , Shamsi Shahab A. 
Published: February 2004

AbstractThe effect of hydrocarbon chain length on chemical selectivity in micellar electrokinetic chromatography (MEKC) was investigated using polymeric sulfated surfactants: poly‐(sodium 7‐octenyl sulfate), poly(sodium 8‐nonenyl sulfate), poly(sodium 9‐decenyl sulfate), and poly(sodium 10‐undecenyl sulfate). Linear solvation energy relationships (LSERs) and free energy of transfer studies were conducted to predict the selectivity differences between the four polymeric surfactants. The overall nature of the solute/ polymeric micelle interactions was found to be different despite the fact that all polymeric surfactants have the same head group. The polar character and acidic strength of the polymeric surfactant are found to decrease as the hydrocarbon chain length of the surfactant is increased. On the other hand, the polarizability of the polymeric sulfated surfactants increases (upon interacting with solute lone‐pair electrons) with increasing hydrocarbon chain length. The LSER results show that the solute size and hydrogen bond accepting ability play the key roles in MEKC retention.
Capillary electrochromatography of peptides on a neutral porous monolith with annular electroosmotic flow generation
Authors: Li Yan , Xiang Rong , Horváth Csaba , Wilkins James A. 
Published: February 2004

AbstractA new kind of monolithic capillary column was prepared for capillary electrochromatography (CEC) with a positively charged polymer layer on the inner wall of a fused‐silica capillary and a neutral monolithic packing as the bulk stationary phase. The fused‐silica capillary was first silanized with 3‐glycidoxypropyltrimethoxysilane (GPTMS). Polyethyleneimine (PEI) was then covalently bonded to the GPTMS coating to form an annular positively charged polymer layer for the generation of electroosmotic flow (EOF). A neutral bulk monolithic stationary phase was then prepared by in situ copolymerization of vinylbenzyl chloride (VBC) and ethylene glycol dimethacrylate in the presence of 1‐propanol and formamide as porogens. Benzyl chloride functionalities on the monolith were subsequently hydrolyzed to benzyl alcohol groups. Effects of pH on the EOF mobility of the column were measured to monitor the completion of reactions. Using a column with this design, we expected general problems in CEC such as irreversible adsorption and electrostatic interaction between stationary phase and analytes to be reduced. A peptide mixture was successfully separated in counter‐directional mode CEC. Comparison of peptide separations in isocratic monolithic CEC, gradient HPLC and capillary zone electrophoresis (CZE) indicated that the separation in CEC is governed by a dual mechanism that involves a complex interplay between selective chromatographic retention and differential electrophoretic migration.
Polymeric alkenoxy amino acid surfactants: III. Chiral separations of binaphthyl derivatives
Authors: Rizvi Syed Asad Ali , Simons David Nicholas , Shamsi Shahab A. 
Published: February 2004

AbstractMicellar electrokinetic chromatography (MEKC) was investigated for the enantiomeric separations of three binaphthyl derivatives ((±)‐1,1'‐bi‐(2‐naphthol) (BOH), (±)‐1,1'‐binaphthyl‐2,2'‐diyl hydrogenphosphate (BNP), and (±)‐1,1'‐binaphthyl‐2,2'‐diamine (BNA)) using two recently synthesized chiral polymeric surfactants (polysodium N‐undecenoxy carbonyl‐L‐leucinate (poly‐L‐SUCL) and polysodium N‐undecenoxy carbonyl‐L‐isoleucinate (poly‐L‐SUCIL)) in our laboratory [33]. Enantiomeric separation (resolution and selectivity) of the binaphthyl derivatives was influenced by polymerization concentration of the monomeric surfactant, pH, type and concentration of the background electrolyte (BGE) as well as concentration of the polymeric surfactant. Two BGEs (dibasic phosphate and Tris‐borate) were compared for this study. The use of dibasic phosphate as BGE in poly‐L‐SUCL provides baseline resolution of (±) BOH and (±) BNP, however, no resolution and selectivity at all was observed for (±) BNA. A similar approach was adopted with Tris‐borate‐poly‐L‐SUCL system at fixed pH 10.1, which resulted in baseline resolution of all three binaphthyl derivatives. Although Rs of binaphthyl derivatives was always higher and electroosmotic flow (EOF) was always lower using Tris‐borate than with dibasic phosphate, the selectivity values for the two buffer systems did not differ significantly. In addition, it was found that poly‐L‐SUCL provided better enantiomeric resolution and selectivity for (±) BOH and (±) BNA, while poly‐L‐SUCIL provided enhanced enantiomeric resolution but similar enantioselectivity for (±) BNP. This indicates that the depth of analyte penetration into the palisade layer and the micellar core are responsible for chiral recognition of hydrophobic analyte (e.g., (±) BOH, and (±) BNA) whereas for moderately hydrophobic analyte (e.g., (±) BNP) interaction with the polar head group seems to dictate chiral recognition. Simultaneous enantioresolution of all three binaphthyl derivatives was possible in a single electrophoretic run using either poly‐L‐SUCL or poly‐L‐SUCIL. Further comparison of the two polymeric surfactants showed that poly‐L‐SUCL provided slightly longer analysis time than poly‐L‐SUCIL but the use of the former polymeric surfactant should be preferred due to its ability to provide complete baseline resolution and higher selectivity of all the three atropisomers with a wider chiral window.
Optimization of sample stacking for the simultaneous determination of nonsteroidal anti‐inflammatory drugs with a wall‐coated histidine capillary column
Authors: Pai Yi‐Fen , Lin Chun‐Chi , Liu Chuen‐Ying 
Published: February 2004

AbstractA wall‐coated histidine capillary column was developed for the on‐line preconcentration of nonsteroidal anti‐inflammatory drugs (NSAIDs) in capillary electrochromatography (CEC). A wide variety of experimental parameters, such as the sample buffer, background electrolyte (BGE) composition, concentration, sample plug lengths, water plug, and the effect of organic modifiers were studied. The relationship between peak height and injection times for the NSAIDs by variation of sample and BGE buffer concentration was investigated. On addition of sodium chloride (0.3–0.6%) to the sample zone, the stacking efficiency was increased. With acetate buffer (100 mM, pH 5.0)/ethanol (20% v/v) as BGE and sample solution in acetate buffer (0.2 mM, pH 5.0)/ethanol (20% v/v)/NaCl (0.3% w/v), NSAIDs could be determined at low μM levels without sample matrix removal. The detection limit was 0.096 μM for indoprofen, 0.110 μM for ketoprofen, 0.012 μM for naproxen, 0.023 μM for ibuprofen, 0.110 μM for fenoprofen, 0.140 μM for flurbiprofen, and 0.120 μM for suprofen. The method could be successfully applied to the simultaneous determination of NSAIDs in urine. The recoveries were better than 82% for all the analytes. The present method enables simple manipulation with UV detection for the determination of NSAIDs at low concentration levels in complex matrix samples.
The use of novel water‐in‐oil microemulsions in microemulsion electrokinetic chromatography
Authors: Altria Kevin D. , Broderick Margo F. , Donegan Sheila , Power Joe 
Published: February 2004

AbstractWe describe the novel use of water‐in‐oil (W/O) microemulsions to achieve unique separations in microemulsion electrokinetic chromatography (MEEKC). The choise and concentration of the buffer type, surfactant and co‐surfactant were all examined and optimized. Separations of a range of neutral and acidic analytes was shown to be markedly different to that obtained by (oil‐in‐water) O/W MEEKC. Neutral solutes are separated by virtue of their solubility (log P) values in O/W MEEKC with the more water‐insoluble solutes migrating last. This separation process does not occur in W/O, as neutral solutes are not separated in order of log P.
Antimutagenic and antiradical properties of flavones from the roots of Scutellaria baicalensis Georgi
Authors: Wożniak Dorota , Lamer‐Zarawska Eliza , Matkowski Adam 
Published: February 2004

AbstractThe four flavonoids baicalin, baicalein, wogonoside, and wogonin have been isolated from Scutellaria baicalensis (Lamiaceae) root extract as main bioactive components. We evaluated their antimutagenic activity as potential chemopreventive natural substances using the Ames test. Free radical scavenging properties have also been measured with the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. Both crude extract and isolated flavone glycosides and aglycones have antimutagenic and free radical scavenging properties. The lipophilic flavone baicalein has been confirmed to be the most powerful antimutagen among the compounds tested.
Properties of wheat bran polyphenol oxidase
Authors: Soysal Çiǧdem , Söylemez Zerrin 
Published: February 2004

AbstractPolyphenol oxidase (PPO) obtained from wheat bran catalyzed the oxidation of 4‐methyl catechol. Phenolic compounds found naturally in crude extract played role as an endogeneous substrate and activity of crude extract needed correction. Activity versus enzyme concentration gave a linear plot at high substrate concentration whereas a nonlinear plot was obtained at low substrate concentration which proved the presence of endogeneous substrate. Adsorption on celite and extraction with polyvinylpyrrolidone (PVPP) caused the removal of phenols. Adsorption of PPO on celite yielded a 4‐fold increase in specific activity whereas extraction with PVPP yielded a 2.5‐fold increase in specific activity compared to the crude extract. The kinetics of PPO catalyzed oxidation obeyed Michaelis‐Menten model; Km and Vmax values were found as 218 mM and 99 μM/min, respectively. The enzyme was inhibited by ethyl alcohol, dithiothreitol (DTT) and isoproterenol and exhibited heat stability up to a temperature of 90°C. The optimum pH of the enzyme was found to be 5.0.
Quality and safety evaluation of genetically modified potatoes Spunta with Cry V gene: Compositional analysis, determination of some toxins, antinutrients compounds and feeding study in rats
Authors: El Sanhoty Rafaat , Abd El‐Rahman Ahamed Ali , Bögl Klaus Werner 
Published: February 2004

AbstractThe aim of this study was to evaluate the composition, nutritional and toxicology safety of GM potato Spunta lines compared to that of conventional potato Spunta. Compositional analyses were conducted to measure the proximate chemical composition with references to 14 components, total solid, protein, lipid, crude fibre, ash, carbohydrate, starch, reducing sugar, nonreducing sugar, sodium, calcium, potassium, phosphorus, and ascorbic acid. Some toxins and anti‐nutrients compounds were determined. Feeding study of GM potatoes line (G2 and G3) in rats were done for 30 days. Four groups of albino rats were used for studying the effect and the safety assessment of GM potatoes Spunta G2 and G3. Group (I) was fed on control basal diet, group (II) was fed on control diet plus 30% freeze‐dried nongenetically modified potato Spunta, group (III) was fed on control diet plus 30% freeze‐dried genetically modified potato Spunta, and group (IV) was fed on control diet plus 30% freeze‐dried genetically modified potato Spunta GMO G3. There were no significant differences between GM potatoes G2, G3, and Spunta control potato line in the proximate chemical composition. The levels of glycoalkaloids in transgenic potato tubers and nontransgenic were determined and there were also no significant differences between the GM potatoes and conventional potato line, the levels were in agreement with a safety level recommended by FAO/WHO (200 mg/kg) for acute toxicity. Protease inhibitor activity and total phenol were estimated and no significant differences between the GM potatoes line and conventional potato Spunta line were found. During the period tested, rats in each group (I, II, III, IV) grew well without marked differences in appearance. No statistical difference were found in food intake, daily body weight gain and feed efficiency. But there is a slightly significant difference in finally body weight between the control group and experimental groups. No significant difference were found in serum biochemical value between each groups, and also between relative organs weight (liver, spleen, heart, kidney, testes). From these results, it can be concluded that the GM potatoes Spunta line (G2 and G3) with Cry V gene are confirmed to have nearly the composition and biochemical characteristics as non‐GM potato Spunta.
Effects of extrusion variables on the properties of waxy hulless barley extrudates
Authors: Köksel Hamit , Ryu Gy‐Hyung , Basman Arzu , Demiralp Hande , Ng Perry K. W. 
Published: February 2004

AbstractThe objective of this research was to investigate the extrudability of waxy hulless barley flour under various extrusion conditions. Waxy hulless barley flour was processed in a laboratory‐scale corotating twin‐screw extruder with different levels of feed moisture content (22.3, 26.8, and 30.7%) and die temperature (130, 150, and 170°C) to develop a snack food with high β‐glucan content. The effects of extrusion condition variables (screw configuration, moisture, and temperature) on the system variables (pressure and specific mechanical energy), the extrudate physical properties (sectional expansion index, bulk density), starch gelatinization, pasting properties (cold peak viscosity, trough viscosity, and final viscosity), and β‐glucan contents were determined. Results were evaluated by using response surface methodology. Increased extrusion temperature and feed moisture content resulted in decreases in exit die pressure and specific mechanical energy values. For extrudates extruded under low shear screw configuration (LS), increased barrel temperature decreased sectional expansion index (SEI) values at both low and high moisture contents. The feed moisture seems to have an inverse relationship with SEI over the range studied. Bulk density was higher at higher moisture contents, for both low and high barrel temperatures, for samples extruded under high shear screw configuration (HS) and LS. Cold peak viscosities (CV) were observed in all samples. The CV increased with the increase in extrusion temperature and feed moisture content. Although β‐glucan contents of the LS extrudates were comparable to that of barley flour sample, HS samples had generally lower β‐glucan contents. The extrusion cooking technique seems to be promising for the production of snack foods with high β‐glucan content, especially using LS conditions.
Genotypic effects on glucosinolates and sensory properties of broccoli and cauliflower
Authors: Schonhof Ilona , Krumbein Angelika , Brückner Bernhard 
Published: February 2004

AbstractThe objective of this study was to investigate the influence that the species, form or cultivar exerts on the glucosinolate spectrum for glucosinolates and free sugars in selected vegetable species of the Brassica genus (Brassica oleracea var. italica Plenck, Brassica rapa var. alboglabra and Brassica oleracea var. botrytis L.). The results showed significant differences amongst the cultivar groups for the glucosinolate proportions as well as the contents of health‐promoting and flavour‐influencing alkyl, alkenyl and indole glucosinolates. The clear differences in the proportions of glucosinolates amongst the groups were not significantly influenced by the weather, although the absolute glucosinolate contents were. Interestingly, the species, forms and cultivars diverged in their external and internal sensory attributes, for example, colour, taste properties such as bitter and sweet, flavour such as green/grassy, spicy, broccoli‐like, cabbage‐like, cauliflower‐like, kohlrabi‐like, leek‐like and mouth‐feel pungent. Differences in the sensory attributes led to different consumer acceptability based on first impressions judged on colour, flavour and overall liking. Consumers were seen to prefer cultivars with a bright colour, a lower level of bitter tasting glucosinolates (alkenyl and indole glucosinolates) and a higher sucrose content. Significant correlations were determined between the compound concentrations, the descriptively determined sensory properties and the consumer scores. Here, we identified properties of broccoli and cauliflower which, when optimised to the tastes of the consumer, could boost their acceptability.