bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of tetracycline and its related substances by capillary zone electrophoresis
Authors: Van Schepdael Ann , Saevels Jan , Lepoudre Xavier , Kibaya Rukia , Gang Ni Zhi , Roets Eugèn , Hoogmartens Jos 
Published: May 2005

AbstractTetracycline was separated from its main impurities 4‐epitetracycline, anhydrotetracycline, 4‐epianhydrotetracycline, chlortetracycline, and demethyltetracycline by capillary electrophoresis. Systematic method development was performed in which following parameters were consecutively optimized: type and pH of the buffer, buffer concentration, type and concentration of organic modifier, voltage and temperature. Qualitative and quantitative aspects of the method are compared with liquid chromatography.
Characterization and identification of the mucilage extracted from orchid bulbs (Bletia campanulata) by high temperature capillary gas chromatography (HT‐CGC)
Authors: Peña Araceli , Capella Santiago , González Carolusa 
Published: May 2005

AbstractThe aim of this work was to develop an analytical method by High Temperature Capillary Gas Chromatography (HT‐CGC) to characterize and identify the presence of tzauhtli, orchid mucilage, in works of art. During the pre‐Hispanic and colonial period, tzauhtli was used as an adhesive for paper and feathers, as well as paint binder, and was one of the components of the paste used to model corn stalk sculptures. The mucilage was extracted with hot water from orchid bulbs (Bletia campanulata) and lyophilized. The free sugars from the mucilage were analyzed by CGC after derivatization. The polysaccharide of the mucilage was characterized after its partial acid hydrolysis by HT‐CGC analysis of the oligosaccharides obtained. The proposed chromatographic method allows the identification of different mucilages in works of art. This contribution is the first report of the oligosaccharides from the hydrolysis of the mucilage extracted from orchid bulbs (Bletia campanulata).
Automated optimization of split ratio in capillary gas chromatography
Authors: Nishikawa Y. , Miyoshi S. , Shyoji M. , Braun G. 
Published: May 2005

AbstractAn electronic gas‐flow controller system called Advanced Flow Control (AFC), which controls not only carrier gas pressure at the column inlet but also the total gas flow including the split flow, was designed and evaluated. BASIC programming of repetitive analyses of standard mixtures under varied split ratios and pressure programs allowed automated optimization of those conditions for the desired column loading and resolution between adjacent peaks.
Separation of twenty‐one naphthalene sulfonates by means of capillary electrophoresis
Authors: Kok Steven J. , Koster Emile H. M. , Gooijer Cees , Velthorst Nel H. , Brinkman Udo A. Th. , Zerbinati Orfeo 
Published: May 2005

AbstractThe production and use of naphthalene sulfonates can easily cause pollution of surface and other types of waters. In the present study, capillary electrophoresis in combination with UV absorption detection was used to separate 21 amino‐ and hydroxy‐substituted naphthalene sulfonates which included multiple isomeric compounds. The influence of various parameters such as pH (which turned out to be extremely important), temperature of the surrounding air flow, and the use of buffer additives (micelles, cyclodextrins, organic modifiers) was studied. Complete separation of all analytes including the isomers, was achieved in two runs with a 50 mM boric acid/borate buffer, containing either 100 mM sodium dodecylsulfonate or 15% acetonitrile. The limits of detection obtained for the individual compounds typically were 20μgI−1. River water samples spiked at this concentration level could be analysed using a simple three‐step sample clean‐up procedure.
HPLC—UV determination of pesticide residues at 0.01 ppm in apple and pear pulp used for baby food
Authors: Bicchi Carlo , Balbo Cristina , Binello Arianna , D'Amato Angelam 
Published: May 2005

AbstractTwo distinct methods are described for determination of residues of ethiofencarb and triforine, and of diflubenzuron, teflubenzuron, and triflumuron at the 0.01 ppm level in apple and pear pulp used for baby food;recoveries are above 50%. Diflubenzuron, teflubenzuron, and triflumuron are extracted with a 1:1 mixture of dichloromethane and acetone, and the extracts are cleaned by SPE using C18 as stationary phase and methanol as mobile phase. Ethiofencarb and triforine are extracted with dichloromethane, and the extracts cleaned using the same stationary phase but a 1:1 mixture of acetonitrile and water as mobile phase. Analysis of both groups of pesticides is by isocratic HPLC—UV at 210 nm using an RP‐18 column and acetonitrile‐water as mobile phase.
Gas chromatographic separation of the stereoisomers of organophosphorus chemical warfare agents using cyclodextrin capillary columns
Authors: Smith J. Richard , Schlager John J. 
Published: May 2005

AbstractThe synthesis of the organophosphorus nerve agents sarin, tabun, and cyclohexyl methylphosphonofluoridate (GF) produces a mixture of two stereoisomers except for soman where four stereoisomers are produced. Significant differences exist in the reported toxicity and AChE inhibition rates of the various stereoisomers. This makes the ability to distinguish between the different stereoisomers desirable. Five different derivatized cyclodextrin stationary phases developed for gas chromatography were tested for their ability to resolve the nerve agent stereoisomers using a gas chromatograph interfaced to an atomic emission detector. Of the five columns that we examined, only the 2,6‐di‐O‐pentyl‐3‐O‐trifluoroacetyl or 2,6‐di‐O‐pentyl‐3‐O‐butyryl γ‐cyclodextrins were able to successfully resolve all four soman stereoisomers. The elution order for each column was determined using solutions of isolated soman stereoisomers. Enantiomers of sarin, tabun, and GF were resolved with varying degrees of success on the different cyclodextrin stationary phases. Only the butyryl γ‐cyclodextrin was able to separate the enantiomers of all four of the nerve agents examined in this study. The capacity (k) and selectivity (α) factors were determined for each of the chemical warfare agents successfully separated. The TNO Prins Maurits Laboratory in the Netherlands has previously developed several different chromatographic methods to resolve the stereoisomers of soman, sarin, and tabun. The advantage of the method described here is that commercially available cyclodextrin gas chromatography columns were used to resolve the stereoisomers, thereby facilitating rapid and routine analysis of organophosphorus nerve agents.
A new method for the chiral HRGC assay of L‐2‐hydroxyglutaric acid in urine
Authors: das Neves Higuinaldo J. Chaves , Noronha João Paulo , Rufino Helena 
Published: May 2005

AbstractL‐2‐Hydroxyglutaric aciduria is a recently discovered inherited neurometabolic disease for which diagnostic identification of the right enantiomer is required. A method is described where alkyl esters of both L‐and D‐2‐hydroxyglutaric acids are prepared without side lactonization. Esterification is achieved at room temperature by reaction with appropriate alkyl chloroformates. This method avoids lactonization, in contrast to esterification with alcohols in acidic media or with diazomethane. The identity of the derivatives is established by HRGC‐FTIR and HRGC‐MS. Chiral HRGC separation with capillaries coated with 1(R)‐trans‐N‐N'‐1,2‐cyclohexylenebisbenzamideoligodimethyL‐siloxane and with a cyclodextrin is compared. The method is adequate for quantitative determinations.
Determination of cholesterol in fat and muscle of pig by HPLC and capillary gas chromatography with solvent venting injection
Authors: Maraschiello Ciriaco , Díaz Isabel , Regueiro José A. García 
Published: May 2005

AbstractTwo methods for determination of cholesterol in fat and muscle of pig were evaluated: extraction with chloroform:methanol (2:1, v/v) followed by saponification (method 1) and direct saponification (method 2). HPLC and GC were used to determine cholesterol concentrations. GC analysis was performed with a capillary column of 100 μm using a PTV injector in the modes of cold split and solvent venting. Cholesterol was analyzed without derivatization. Both methods of extraction did not present significant differences (p > 0.01). Sample analysis by GC with solvent venting injection and HPLC showed the lowest % r.s.d. but GC in the cold split mode allowed to obtain a shorter analysis time. Cholesterol concentrations obtained by HPLC were not statistically different from the results obtained by GC with solvent venting injection and were slightly lower than those previously reported. Cholesterol concentrations in fat and muscle tissues respectively ranged from 52 to 77 mg/100 g and from 55 to 65 mg/100 g.
Retention in SFC at high density
Authors: Shen Yufeng , Hung Hongxin , Zhou Liangmo 
Published: May 2005

AbstractThe elucidation of the detailed mechanism of retention in supercritical fluid chromatography (SFC) is a complex problem, especially for high‐density supercritical fluid mobile phases. Martire and Boehm developed a theory of SFC retention based on a statistical thermodynamic treatment, and introduced a density‐squared equation for retention in SFC: In k = a + b/T + cρ + dρ/T + eρ2/T. In this paper the systems n‐alkane‐polydimethylsiloxane‐CO2 and n‐carboxylic acid methyl ester‐polydimethylsiloxane‐CO2 have been treated using the method introduced by Martire and Boehm. In the ranges of reduced temperature from 1.079 to 1.293 and reduced SF mobile phase density from 0.705 to 1.632, two problems were discovered in the treatment of SFC retention behavior by the method of Martire and Boehm: (1) the experimental value of the site of CO2 in the lattice field, ra, of the two systems was ca 0.9, which is obviously different from the theoretical values of 3.6 or 5.4; and (2) the difference between experimental and calculated retention values increased with increasing SF mobile phase density. The minimum in SFC retention predicted by Martire and Boehm was not observed. On the basis of some assumptions and the experimental data, the following retention equation was derived: In k = a + b/T + cρ + dρ/T + eρ2/T + fρ3/T + gρ4/T. This equation was consistent with the experimental data and can conveniently be used to explain other SFC retention behavior.
The advantage of dual‐column approach and retention indices combined with refined reporting in gas chromatographic drug screening
Authors: Rasanen Ilpo , Ojanperä Ilkka , Vartiovaara Juhani , Vuori Erkki , Sunila Pekka 
Published: May 2005

AbstractA dual‐column gas chromatographic retention index method was evaluated for the toxicological screening for basic drugs in autopsy blood samples. The dual‐column approach with DB‐5 and DB‐1701 capillary columns doubles the Identification Power of the corresponding single column methods. The long‐term intralaboratory variation of the dialkylfluoroaniline series based retention indices of drugs in blood ranged from 0.03% to 0.2% which was generally better than that obtained using the relative retention time. Novel software is described for the processing and reporting of the dual‐column chromatographic data in analytically useful form. Besides retention data, the response factors served as an additional identification factor.
HRGC/FID/NPD and HRGGC/MSD study of Colombian ylang‐ylang (Cananga odorata) oils obtained by different extraction techniques
Authors: Stashenko Elena E. , Prada Nubia Quiroz , Martínez Jairo R. 
Published: May 2005

AbstractSteam distillation (SD), simultaneous distillation‐solvent extraction (SDE), and supercritical (CO2) extraction (SFE) were used to isolate volatile secondary metabolites from fresh, totally mature flowers of Colombian ylang‐ylang (Cananga odorata). The various extracts were analyzed by capillary chromatography (DB‐1, DBWAX, 60 m columns) using FID, NPD or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard substances were employed for compound identification. 51, 70, and 73 compounds at concentrations above 100 ppb were detected in the SD, SDE, and SFE extracts, respectively. The main constituents of these extracts were linalool (20.7, 28.0, and 16.5%), germacrene‐D (10.1, 3.1, and 20.3%) benzyl benzoate (14.1, 2.9, and 3.9%), benzyl acetate (9.6, 17.0, and 6.2%), caryophyllene (3.1, 2.9, and 3.9%), and p‐methylanisole (6.8, 6.1, and 2.7%). 85% of the composition of SDE extracts was represented by oxygenated compounds. Heavy hydrocarbons (Cn >20) and fatty acids were found only in the SFE extracts, which also had a higher content of nitrogenated compounds (phenylacetonitrile, 4‐methylbenzaldoxime, indole, 2‐phenyl‐nitroethane, and methyl anthranilate) and sesquiterpenes (43% vs 19.5% in SD and 8.1% in SDE) and 1.5 – 2 times lower concentration of monoterpenes and light oxygenated compounds than the SD (49.7%) and SDE (64.5%) extracts.
Capillary electrophoresis determination of six bioactive constituents in San‐huang‐hsieh‐hsin‐tang
Authors: Sheu Shuenn‐Jyi , Lu Chyong‐Fang 
Published: May 2005

AbstractA capillary electrophoretic method for simultaneous determination of six bioactive ingredients (berberine, palmatine, baicalin, sennoside B, emodin, and sennoside A) in the Chinse herbal formula San‐huang‐hsieh‐hsin‐tang was established. A carrier composed of aqueous buffer solution (50 mM sodium cholate, 15 mM sodium dihydrogen phosphate, and 4.25 mM sodium borate)‐acetonitrile (3:2) was found to be the most suitable electrolyte for this separation. Contents of these constituents in a non‐pretreated methanol‐water extract of San‐huang‐hsieh‐hsin‐tang sample could be easily determined within 20 min. The effects of borate, cholate, and organic modifier (acetonitrile) concentration of the carrier on the migration behavior of the solutes were also studied.
Separation of neutral and basic enantiomers by cyclodextrin electrokinetic chromatography using anionic cyclodextrin derivatives as chiral pseudo‐stationary phases
Authors: Tanaka Yoshihide , Yanagawa Mayumi , Terabe Shigeru 
Published: May 2005

AbstractSeparations of neutral and basic racemates were performed using five different anionic cyclodextrin (CD) derivatives as chiral selectors, viz. carboxymethylated β‐CD, β‐CD phosphate sodium salt, sulfobutyl ether β‐CD sodium salt, carboxymethylated γ‐CD, and γ‐CD phosphate sodium salt. For the separation of neutral racemates, an untreated fused silica capillary was employed and various neutral racemates were successfully separated. Since the pH of the buffer affected the electroosmotic flow (EOF), the resolution was improved by changing the buffer pH. A polyacrylamide coated capillary was employed for the separation of basic racemates to suppress EOF and to prevent adsorption of cationic analyte on the capillary surface. By choosing an appropriate type and concentration of anionic CD, about 40 basic racemates were successfully separated. Some rough binding constants of basic analytes with an anionic β‐CD were measured to discuss the optimum concentration of the CD. The migration direction was dependent on the binding constants and the concentration of the CD. The analyte strongly bound to the anionic CD migrated towards the anode but the weakly bound one moved towards the cathode. Anionic γ‐CDs were also very useful for the separation of basic enantiomers. Five neutral CDs were employed as chiral selectors to compare selectivity between charged and neutral CDs, and eleven racemates could only be resolved using anionic CDs. The separation of some basic racemates in human plasma was also described. The direct injection of plasma samples was possible for some enantiomers that did not interact strongly with plasma proteins.
On‐line solvent evaporator for coupled LC systems: Further developments
Authors: Moret Sabrina , Grob Konrad , Conte Lanfranco S. 
Published: May 2005

AbstractAn on‐line solvent (eluent) evaporator is used for reconcentrating a fraction from a first LC column before introduction into a second LC separation step, possibly involving another mobile phase. For pentane and pentane containing 10 % of dichloromethane, evaporation rates of 1 ml/min were achieved. On evaporating a volume of 6 ml, 2‐ethylnaphthalene was retained to more than 75%. Separation of aliphatic and polyaromatic hydrocarbons in a linseed oil is shown as an application.
The determination of volatile organic compounds in soils using solid phase microextraction with gas chromatography‐mass spectrometry
Authors: James Kevin J. , Stack Mary A. 
Published: May 2005

AbstractSolid phase microextraction (SPME) was applied in the development of a protocol for the analysis of a number of target organic compounds in landfill site samples. The selected analytes, including aromatic hydrocarbons, chlorinated hydrocarbous, and unsaturated compounds, were absorbed directly from a headspace sample above a soil layer onto a fused silica fiber. Following exposure, the fiber was thermally desorbed in the injection port of the gas chromatograph and eluted compounds were detected using a mass selective detector. The stability and sensitivity of the extraction technique were examined at five temperatures (22–60°C) using a 100μm polydimethylsiloxane fiber. Calibrations, using soil samples spiked with selected solvents (0.5–30 μg/g), were linear; trichloroethene (r2 = 0.992) and benzene (r2 = 0.998). SPME was applied to the examination of a municipal landfill where 8 sites were sampled, at three depths, resulting in the detection of xylene (maximum 2.8 μg/g) and a number of other non‐target organic contaminants.
High temperature (70°C) size exclusion chromatography of petroleum waxes with RI and FID detection
Authors: Carbognani Lante 
Published: May 2005

AbstractMolecular weight distribution of solid petroleum waxes is a key parameter for the general characterization of these materials. Particular interest concerns extremely large components, typically present in oil distillation residua, and solid deposits found in oil production facilities. Molecular weight distributions of oil waxes were determined in this work by high temperature size exclusion chromatography. Separations were carried out with two different eluents, namely toluene and ortho‐dichlorobenzene and two detection systems, these being a differential refractive index and a flame ionization detector. Toluene proved to be the best choice when combined with flame ionization detection. Better uniformity of response was the greatest advantage achieved by this approach. The experimental set up permitted analysis of samples containing molecules with up to 138 carbon atoms. Burning properties of very large molecules, isomerism affecting calibration, and signal asymmetry when flame ionization detection was adopted were three issues still requiring additional efforts to understand and to improve analysis accuracy.
Environmental applications of capillary gas chromatography coupled with atomic emission detection — a review
Authors: Pedersen‐Bjergaard Stig , Greibrokk Tyge 
Published: May 2005

AbstractEnvironmental applications of capillary gas chromatography coupled with atomic emission derection (GC‐AED) have been reviewed with emphasis on both the commercial and laboratory‐built systems. Attention was focused on (1) element‐selective detection of non‐metallic as well as metallic pollutants, (2) identification of contaminants, and (3) sample preparation considerations.
Complete PCB congener distributions for 17 aroclor mixtures determined by 3 HRGC systems optimized for comprehensive, quantitative, congener‐specific analysis
Authors: Frame George M. , Cochran Jack W. , Bøwadt Søren S. 
Published: May 2005

AbstractThree HRGC systems (1: 30m DB‐XLB capillary with MS‐SIM detection; 2: 60m DB‐XLB capillary with full‐scan, ion‐trap MS detection; and 3: Parallel dual‐column DB‐17 and series‐coupled HP5/HT5 with ECD detection) were used to completely characterize multiple lots of 8 different‐numbered Aroclor mixtures by quantitative calibration against 9 solutions containing primary standards of all 209 PCB congeners. Despite lower absolute sensitivity and more Aroclor congener coelutions than the dual‐column ECD system, the MS systems enabled measurement of more congeners per Aroclor since their greater linear response range did not require dilution of samples and standards. Pairs of different lots of Aroclors 1248 and 1254 displayed markedly different proportions of congeners, and the 1254 pair displayed strong differences in the extent of ortho‐chlorine substitution. The tables of congener weight percent distributions among Aroclors are more comprehensive and quantitatively precise than those of prior publications. However, the limitations of single‐level calibration precluded measurement of all congeners to the ±10% accuracy desirable for establishing these Aroclors as secondary standards for comprehensive, quantitative congener‐specific PCB analysis.
Adulteration or natural variability? enantioselective gas chromatography in purity control of essential oils
Authors: König Wilfried A. , Fricke Christiane , Saritas Yücel , Momeni Behdad , Hohenfeld Gerhard 
Published: May 2005

AbstractThe potential of enantioselective capillary gas chromatography with modified cyclodextrins as chiral stationary phases for authenticity control is demonstrated for a selection of economically important essential oils. Adulteration can be easily detected in cases where enantiomerically pure constituents are present in natural oils. In cases of (naturally) varying enantiomeric compositions of chiral constituents, enantioselective gas chromatography may prove insufficient.
Analysis of carbamate pesticides by micellar electrokinetic chromatography
Authors: Rossi Massimo , Rotilio Domenico 
Published: May 2005

AbstractCapillary elcctrophoresis (CE) was used for the qualitative and quantitative analysis of eleven compounds of the carbamate, thio‐carhamate, and dithiocarbamate classes of pesticides. Micellar elec‐trokinetic chromatography (MEKC) was employed for the separation of these substances. The analysis was performed using an uncoated fused silica column, in borate buffer containing SDS and 10% methanol at basic pH, and UV detection at 230 nm. The addition of methanol to the buffer increased the separation and affected intrinsic migration of analytes. The working standard solutions were prepared in acetonitrile/water 50:50. Although these compounds are structurally different, with a large spectrum of chemical properties, such as polarity and solubility, good separation and sensitivity were obtained. Moreover, good recovery of car‐bamates was obtained from tap‐water using a styrene‐divinylben‐zene polymer column with the solid phase extraction (SPE) technique.
Matrix‐induced peak enhancement of pesticides in gas chromatogrtaphy: Is there a solution?
Authors: Erney D. Ronald , Pawlowski Tina M. , Poole Colin F. 
Published: May 2005

AbstractIn this study, it is shown that calibration solution prepared in control matrix extrix extract can be used to compensate for matrix‐induced chromatographic response enhancement observed for certain pesticedes. This phenomenon is characterized by enhanced chromatographic response for certain pesticides in the presence of matrix du to reduced analyte loss during injection. Unacceptably high recoveries are seen for affected pesticides when maatrix‐free solutions are used for reference and calibration. The effects of matrix concentration on overall enhancement and linear response were determined. When used as reference standards for the determination of recovery, matrix‐standard solutions were found to provide acceptable recoveries for pesticides subject to matrix‐induced chromatographic response enhancement along with other pesticides. General guidelines are presented for using matrix‐standard calibration solutions in pesticide residue analysis.