bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of artemisinin and artemisinic acid by capillary and packed supercritical fluid chromatography
Authors: Köhler Marcel , Haerdi Werner , Christen Philippe , Veuthey Jean‐Luc 
Published: May 2005

AbstractArtemisinin (an antimalarial compound) and its bioprecursor artemisinic acid, present in the plant Atemisia annua L., were analyzed by supercritical fluid chromatography (SFS) using capillary and packed columns, coupled respectively with a flame ionization detector (FID) and an evaporative light scattering detector (ELSD). Both methods were optimized and validated with columns of different polarity in order to separate artemisinin and artemisinic acid. Analytical results were comparable, but the paced SFC‐ELSD method was faster. Indeed, artemisinin and artemisinic acid were separated with an aminopropyl silica column in less than 8 minutes instead of about 25 minutes by capillary SFS. Contrary to conventional gas and liquid chromatography coupled to an UV‐visible detector, SFS methods determined both compounds directly, without degradation and/or derivatization in the concentration range expected in the plant material. Results obtained on plant extracts by capillary SFS‐FID and packed SFS‐ELSD were confirmed by GC‐MS.
Eavaluation of automatic thermal desorption–capillary GC for determination of semivolatile organic compounds (SVOCS) in indoor air
Authors: Clausen Per Axel , Wolkoff Peder 
Published: May 2005

AbstractSome data on a newly developed filter/sorbent indoor air SVOC sampling device for thermal desorption analyiss are described. Thermal desorption of SVOCs spiked on Tenax had reponse factors identical to on‐column injection except for highly polar compounds like fatty acids. SVOCs spiked on quartz fiber filters had response factors that on an average were 80% of the on‐column response factors (66% for oxygen containing compounds and 87% for non‐oxygen compounds) Low nanogram on‐tube amounts of SVOCs were found generally to have lower recoveries than larger amounts from both Tenax and quart fiber filters. This appeared to be explained in part by a relatively larger “memory” effect and lower desorption efficiency. In addition, it was indicated that the “memory” effect was an important source of background contaminations that might impair analysis of low nanogram on‐tube amounts of some SVOCs. Polar SVOCs. Polar SVOCs in the gas phase appear to adsorbto the quartz fiber filters. This functions as a precleaning of the sample and thus minimizes the problem with coeluting peaks. The relative standard from nine duplicate samples appeared to be sufficiently low to distinguish a day variation.
Standard equivalent chain length values of monoenic and polyenic (methylene interrupted) fatty acids
Authors: Stránsky Karel , Jursík Tomáš , Vítek Antonín 
Published: May 2005

AbstractThe equivalent chain length (ECL) values of the methyl esters of 83 defined fatty acids (FAs) have been determined by gas chromatog‐raphy (GC) on three fused silica DB‐WAX and three DB‐1 columns. ECL values of further 46 FAs were calculated by different methods. Conditions of chromatography, methods of ECL values calculation and differences between ECL values on individual columns and between trans‐ and cis‐isomers of corresponding FAs are also discussed.
Enantiomer separations by capillary GC on modified gyclodextrins
Authors: Kim Byoung Eog , Lee (deceased) Sun Haing , Park Keung Shik , Lee Kwang Pill , Park Jung Hag 
Published: May 2005

AbstractThree new chiral selectors, 6‐tert‐butyldimethylsilyl‐2,3‐diethyl‐a‐cyclodextrin, 6‐tert‐butyldimethylsilyl‐2,3‐diethyl‐ and dipropyl‐β‐cyclodextrin (TBDE‐α‐CD, TBDE‐β‐CD, TBDP‐β‐CD) were synthesized and tested as chiral stationary phases in capillary gas chromatography. TBDE‐β‐CD in particular showed a high enan‐tioselectivity for test chiral compounds due to good solubility in a polar polysiloxane (OV‐1701). Enantioselectivity obtained with TBDE‐β‐CD was compared with that of 6‐tert‐butyldimethylsilyl‐2,3‐di‐O‐methyl‐β‐cyclodextrin (TBDM‐β‐CD). Better enantiose‐lectivity was obtained with TBDE‐P‐CD than with TBDM‐β‐CD for the test chiral compounds studied. This is probably due to greater effect of the increased hydrophobicity of TBDE‐β‐CD which favors inclusion of the analytes than the effect of increased steric hindrance. With TBDP‐β‐CD the less polar lactones are well separated due most likely to increased hydrophobicity of the propyl groups while the more polar are not well resolved. For TBDP‐β‐CD it is likely that the unfavorable steric hindrance is predominant over the favorable hydrophobicity of the propyl groups, thus hindering the formation of inclusion complexes of the alcohols with TBDP‐β‐CD. TBDE‐α‐CD was also a valuable chiral selector for the separation of small chiral molecules such as simple secondary alcohols and nitro‐substituted alcohols.
Unusual Δ5cis‐fatty acids in seed oils of Cimicifuga species
Authors: Tsevegsüren Nanzad , Aitzetmüllei Kurt 
Published: May 2005

AbstractA range of unusual fatty acids with cis‐5‐unsaturation had been reported in the seed oil of Caltha palustris. Seed oils of Cimicifuga spp. have now been found to contain the same unusual fatty acids as are present in Caltha, plus several other minor fatty acids to give a more complex and more unsaturated seed oil fatty acid pattern.The gas chromatographic fatty acid patterns found seem to be consistent and chemotaxonomically significant, because essentially the same pattern was found in several species of the genus Cimicifuga. These findings may shed a new light on the relation of Cimicifuga to Caltha, and to other genera in the plant family Ranunculaceae.The situation is illustrated by capillary GLC seed oil fatty acid methyl ester “fingerprints” obtained from Cimicifuga and Caltha, and is discussed in relation to other genera. The occurrence in nature of several of these unusual fatty acids, and their chemotax‐onomic significance is discussed. The close relation of GLC fatty acid patterns of Caltha and Cimicifuga could indicate monophyly and/or their belonging to the same tribe or subtribe. These observations are not in accordance with the phylogenetic systematic schemes of the genera in this plant family as published by various authors.
Simultaneous determination of nicotinamide, nicotinic acid, riboflavin, thiamin, and pyridoxine in enriched Brazilian foods by HPLC
Authors: Agostini Tania S. , Godoy Helena T. 
Published: May 2005

AbstractThe control of the enrichment levels in foods is difficult, due mainly to the lack of appropriate analytical methodologies. The amounts of the five B‐group vitamins (nicotinamide, nicotinic acid, ribofla‐vin, thiamin, and pyridoxine) have been determined in enriched Brazilian foods by a high‐performance liquid chromatography (HPLC) method. Fifty products, such as biscuits, liquid and dry milks, flavored milk drinks, flour, macaroni, and cereals were analyzed. Some products showed the amounts declared on the package. Although some slight quantitative variations were shown in the biscuits, one showed levels of riboflavin 35% lower than the value declared. Of five different corn cereal brands, only one showed the declared vitamin content, the others showing levels 30 % lower than that declared. No B‐group vitamins were detected in one brand of enriched macaroni, except for the nicotinic acid naturally present in the flour. On the other hand, one flavored milk drink exhibited vitamins levels 200% higher than the amounts declared and one milk drink mix presented thiamin, riboflavin, and nicotinamide levels 3 to 5 times greater than stated. These results suggest an absence of control of the amount of vitamins in enriched foods.
Application of capillary electrophoresis in migration studies of food contact materials – part 1: Substituted phenolic additives
Authors: Abrantes Shirley , Philo Mark R. , Damant Andrew P. , Castle Laurence 
Published: May 2005

AbstractA method has been developed to determine 11 phenolic antioxidants in the food simulants distilled water, 3% acetie acid, and 15% ethanol, using; micellar capillary electrophoresis (MCE). All the phenols could he analyzed within 35 min. The analytical recovery from spiked simulants was 80 to 119% except for 2,6‐di‐tert‐butyl‐4hydroxytoluenc (BHT) and octyl gallate, which could not be recovered from 3% acetic acid simulant. Calibration graph correlation coefficients for the 11 phenols were 0.982 to 0.999. Limits of detection (LoDs) were from 2.8 to 8.6 mg/L. These LoDs are well below European Union migration limits for these substances. It is concluded therefore that MCE offers a rapid and reliable analysis for the control of migration from plastics intended for food contact which employ these phenols as antioxidants.
Experimental design optimization of the analysis of gasoline by capillary gas chromatography
Authors: Durand Jean Pierre , Gautier Serge , Robert Eric , Guilhem Marie Christine , Phan‐Tan‐Luu Roger 
Published: May 2005

AbstractAn optimization procedure for multi‐step temperature programmed capillary GC was investigated for the detailed hydrocarbon analysis of gasoline. A set of twelve responses, represented by the value of the resolution of the most difficult separations, was selected from several isothermal analyses. The variation of these responses versus the temperature programming conditions was then modeled using a Doehlert matrix for experimental design. Optimal experimental conditions for the twelve responses were then obtained from a response surface optimization. The predicted and experimental resolutions were in good agreement.
Analysis of volatile sesquiterpenoids in environmental and geological samples
Authors: Elias Valdimir O. , Simoneit Bernd R. T. , Cardoso Jari N. 
Published: May 2005

AbstractIn order to evaluate vloatile compounds, especiallly sesquiter‐penoids, in environmental and geological samples a method was penoids, in environmental and geological samples a method was required to characterize these components when they occur at low concentrations. After fractionation of the total sample extracts by TLC the aliphatic fractions were analyzed by HRGC AND THE kovats indices of all resolved peaks were calculated and comkpared with indices of all resolved peaks were calculated and compared with those obtained for commercial standards. As final step, the fractions were analyzed by HRGC‐MS and structures confirmed by comparison of their mass spectra with those of certified sesuiterpene standards. Additionally sesquiterpenoids present in the dissolved phase in water samples were concentrated by solid phase extraction using XAD‐2 resin. In this initial study, recovery tests with the resin were carried out in order to evaluate its performance rather than validating the methodology.
A continuous liquid‐liquid extraction system coupled on‐line with capillary gas chromatography for environmental and ecotoxicological analysis
Authors: Goosens Elise C. , de Jong Dirk , de Jong Gerhardus J. , Brinkman Udo A. Th. 
Published: May 2005

AbstractThe applicability of a liquid‐liquid extraction system which is coupled on‐line with a capillary gas chromatograph was studied for environmental and ecotoxicological analyses. The optimized and automated system was used for the determination of apolar and rather non‐volatile organic compounds in aqueous samples. Relevant aspects of sample introduction, phase separation and selection of extraction solvent are discussed. Three routine‐tipe applications are described, viz. an improved method for the determination of hexachlorocyclohexanes in ground water and the determination of the so‐called NCC‐ether and ACC‐ether in ecotoxicological studies. Depending on the application studied, the concentration levels varied from 0.1 to 6000 μg/I, using ECD and/or FID detection. Typical coefficients of variation obtained with the total extraction–GC procedure were 2–25%.The system was found to be rugged, it saves time compared with set‐ups involving off‐line liquid‐liquid extraction and considerably reduces the manual work load.
Determination of benzene alkyl derivatives in heavily loaded environmental aqueous samples by means of combination of distillation and purge and trap‐gas chromatography‐mass spectrometry
Authors: Zygmunt Bogdan 
Published: May 2005

AbstractSimple distillation was used to prepare aqueous environmental samples (especially those with high content of accompanying dissolved and suspended organic and inorganic matter) for determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) by means of purge and trap (PT) coupled to gas chromatography‐mass spectrometry (GC‐MS). The PT step was carried out with a laboratory‐built device in which alalytes desorbed from a Primary trap (macrotrap) are focused in a microtrap (also with sorbent) and moisture is removed from purge gases by a Nafion tube (walls selectively permeable to water vapor). Recoveries, if only the first 10 ml distillate was collected, were of the order of 40% at optimum distillation parameters. At a probability level of 95% recoveries were independent of concentration in a studied concentration range of 0.50–30 ppb. Enrichment factors for distillation were of the order off 20. Real samples, i.e., raw and treated waste water were analyzedc for BTEX content by the developed medthod.
Cyclodextrin derivatives in GC separation of racemic mixtures of volatiles – part XII: Thick‐film wide‐bore columns for enantiomer GC preparation
Authors: Bicchi Carlo , D'Amato Angela , Manzin Valeria , Galli Anna , Galli Mario 
Published: May 2005

AbstractPreliminary results on thick‐film wide‐bore (0.53mm i.d.) columns for GC preparation of pure enantiomers are described. In particular the loading capacity for several racemates of a 3μm, 30% 2,6‐di‐O‐methyl‐3‐O‐Pentyl‐β‐CD/OV1701 column and of a 2 μm, 30% 2,3‐di‐O‐acetyl‐6‐O‐dimethyl‐t‐butylyl‐β‐CD/PS‐086 collumn were determined. Consideration is also given to the relation‐ship between resolution values of two enantiomers on anayltical columns and their loading capacity and scaling‐up to the corresponding micropreparative columns.
Enantiomeric separation of 5‐alkyl‐5methylhydantion derivatives by capillary gas chromatography on permethylated β‐cyclodextrin and molecular modeling
Authors: Cardinaéul Pascal , Ndziéa Elias , Petit Samuel , Coquerel Géurard , Combret Yvette , Combret Jean Claude 
Published: May 2005

AbstractPermethylated β‐cyclodextrin (hereafter designated perMe‐β‐CD), dililuted or not in polysiloxane, is an efficient chiral discriminant for native, 3‐methylated, and 1,3‐dimethylated series of 5‐methyl‐5‐(CnH2n + 1)hydantoins. From thermodynamic data obtained with pure perMe‐β‐CD and with the aid of molecular modeling, it is concluded that: (i) For native hydantoin derivatives having a carbon chain at the 5‐position varying from ethyl to nonyl (2⩽n⩽9), the retention time is related to their H‐bonding capability. The resolution is poor for derivatives with n⩽4. For n⩽5, the resolution is considerably improved and this increase in resolution is attributed to the long alkyl chain being capable of being buried inside the cyclodextrin cavity. (ii) For 1,3‐dimethylhydantion derivatives having a carbon chain at the 5‐position varying from ethyl to hexyl(2⩽n⩽6), the retention time is mainly determined by a steric fit between the solute and the inner volume of the macrocyclic cavity. For n = 2, a particular behavior is observed, consistent with a total inclusion of the solutes inside the cavity. By contrast with the native hydantoins, the selectively is high for light derivatives. Thus, the selectivity does not correlate with a strong docking energy (such as the presence of H‐bonds postulated with native derivatives). (iii) For 3‐methylhydantoin derivatives having a carbon chain at the 5‐position varying from ethyl to octyl (2⩽n⩽8), as expected, retension time and selectivity are intermediate between that of native hydantoins and 1,3‐dimethylhydantoins. For all three series, where n⩽5, the increase in chain length (n) does not bring about substantial changes in the chromatographic results. Therefore, for these long alkyl chain derivatives, similar dominant interactions with perMe‐β‐CD are postulated.
Nonlinear variation of sorption parameters of n‐alkane homologsl in temperature‐programmed gas chromatography (tpgc) and new equation for calculation of retention indixces
Authors: Golovnya Rimma V. , Syomina Lyuba A. , Samusenko Alexei L. 
Published: May 2005

AbstractIt has been demonstated that the considaerable difference in temperature increments of sorption parameters of n‐alkanes under isothermal conditions is the main reason for nonlinear dependence of sorption parameters on molecular mass of homolog in temperaturre programmed gas chromatography (TPGC). A new nonlinear 4th parameter equation has been given for calculation of the retention indices. Coefficients of the equation are calculated from n‐alkanes. The equation allows extrapolation and interpolation calculations of retention indices under TPGC conditions with experimental precision. The results obtained; for fatty acidkl methyl esters demonstrate the advantage of ovr equation in comparison with van den Dool and Kratz's equation.
Separation of native amino acids at low pH by capillary electrophoresis
Authors: Thorntion Michelle J. , Fritz James S. , Klampfl Christain W. 
Published: May 2005

AbstractAmino Acids are cations at low PH and can be readily separated by capillarty electrophoresis provided an alkanesulfonic acid is added to the elecrolyte carrier. Formation of a Positive net charge on the bare fused‐silica surface at low PH was confirmed by measurement of an anodic electroosmotic flow. The addition of ethanesulfonic acid or octanesulfonic acid to the electrolyte carrier causes a reversal of the EOF. A mechanism is proposed in which the alkanesulfonic acid adsorbs to the positively‐charged capillary wall through electrostatci attraction. Adsorption of a second molecule of alkanesulfonate by hudrophobic attraction to the carbon chain forms a negatively‐charge coating on the capillary wall. The alkanesuflfonate also imparts selectivety to the system by participation in ionpairing interactions with the native amino acids to improve resolution. The CE separation of a mixture of the twenty common amino acids at PH 2.8 with direct absorabance detection at 185 nm resulted in 17 amino acid peals in 20 minutes with a 30 KV applied voltage. The effect of several variables was studied including electrolyte carrieres containing different alkanesulfonic acids, the influence of PH, applied voltage, and concentration of electrolyte carrier.
Separation of metal cations in acidic solution by capillary electrophoresis with direct and indirect UV detection
Authors: Thornton Michelle J. , Fritz James S. 
Published: May 2005

AbstractMethods for the detectionn of metal cations under acidic conditions, near PH 2, in capillary electrophoresis (CE) were investigatged. Conditions for direct UV detection of UV absorbing metal cations such as Cr3+, Cu2+, Fe3+, UO22+, VO2+, and VO2+ were established With aqueous HCl or HClO4 as the electroyte carrier. The speciation of vanadium(IV) and vanadium(V) at PH 2.3 by CE was achieved with direct detection at 185 nm. With the strong absorbance at 185 nm, no complexation was needed to detect the metal cations. An indirect UV detrection scheme for acidic conditions was also investigated. Several background carrier electolytes (BCES) were studied including 4‐methylbenzylamince, nicontinamide, pyridazine, guanidine, 3‐picoline, and chromium (III) to determine their effectivencess under very acidic conditions. The efect of ioni c surfactants and the nonionic surfactant, Trition X‐100, on the peak heights and N Values was also studied.
Determination of solvent recondensation or evaporation in the GC‐precolumn by measurement of temperature changes on the column wall
Authors: Hyötyläuinen Tuulia , Grob Konrad , Riekkola Marja‐Liisa 
Published: May 2005

AbstractTemperature measurements on the column outer well were used for detecting recondensation or evaporation of solvent inside the precolumn during injection or on‐line transfer of large solvent volumes. This facilitates the choice of the most critical parameter of these techniques, i.e. oven temperature. When using the vaporizer/precolumn solvent split/gas discharge system, the dew point of the solvent is determined, either to just prevent solvent recondensation or to limit it to the capacity of the precolumn to retain liquid. In concurrent eluent evaporation through the loop type LC‐GC interface, temperature measurement enables the determination of whether or not the flooded zone exceeds a given limit. Fanally, when solvent trapping is used (on‐column injector/partially concurrent solvent evaporation evaporation or vaporizer/partial recondensation), temperature measurement near the front end of the flooded zone is used as a signal for accurate closure of the vapor exit shortly before the end of solvent evaporation.
Theory of fast capillary gas chromatography part. 2: Speed of analysis
Authors: Blumberg Leonid M. 
Published: May 2005

AbstractUsing hold‐up time as a measure of the speed of analysis with a given column efficiency, a theory of pneumatic optimization of a column in the fast high pressure drop isothermal and temperature programmed GC is developed. Expression for the hold‐up time as a function of column efficiency, carrier gas velocity and film thickness is derived. Also found are the expressions for the minimum hold‐up time and optimum gas velocity in a speed‐optimized column. These quantities are compared with their counterparts in the efficiency‐optimized column.
Studies on a possible molecular basis for the structure of mitochondrial cristae
Authors: Sumegi Balazs , Freeman Dale A. , Inman Lindsey , Srere Paul A. 
Published: May 2005

AbstractWe have investigated a possible molecular basis for mitochondrial cristae formation. Proteoliposomes containing electron transport proteins, cytochrome oxidase, or complex III in their proper orientation bind to pig heart mitoplasts but not pig heart mitochondria. Using Leydig tumor cells, we have confirmed earlier reports that chloramphenicol causes a diminution in cristae content and a change in its characteristic lamellar form. We show that the proteoliposomes containing cytochrome oxidase or complex III in the proper orientation bind to mitoplasts from Leydig tumor cells but do not bind as well to mitoplasts from chloramphenicol‐treated Leydig tumor cells. These experiments provide a possible mechanism to explain cristae formation.