bluuebunny/crossref_metadata_2025_split huggingface dataset:
A window diagram for key component analysis in on‐line gas chromatography
Authors: Villalobos Richard 
Published: May 2005

AbstractWindow diagrams that optimize for the separation of only one or a few components in a complex mixture are applied to on‐line process analysis when speed of analysis is more important than a complete separation of all components in the sample. A window diagram based on retention indexes is the most useful for quickly evaluating the feasibility of a given pair of phases. The one with the most useful output is one based on partition ratios, as this can be used directly with the columns in hand. A PC‐based spreadsheet program with integral specific retention volume data for the common liquid phases is described as a tool for selecting the optimum ratio of lengths for the columns in hand.
Characterization of fluvalinate residues in honey by gas chromatography–atomic emission detection and gas chromatography–mass spectrometry
Authors: Jiménez Juan José , Atienza Julián , Bernal José Luis 
Published: May 2005

AbstractTwo hyphenated techniques, gas chromatography–mass spectrometry and gas chromatography–atomic emission detection, have been used to identify the degradation products of the acaricide fluvalinate in a methanol solution of the commercially available formulation Mavrick, as well as in honey from beehives treated with this product. The major degradation products were 2‐chloro‐4‐trifluoromethylaniline (I), methyl 2‐[2‐chloro‐4‐trifluoromethylaniline]‐3‐methylbutanoate (II), N‐(2‐chloro‐4‐trifluoromethyl‐phenyl)valine (III), and 3‐phenoxybenzaldehyde (IV). Fluvalinate in honey is gradually degraded, 3‐phenoxybenzaldehyde being the most abundant residue.
Electron caputure detection in high‐speed narrow‐bore capillary gas chromatography: Fast and sensitive analysis of PCBs and pesticides
Authors: van Ysacker Peter G. , Janssen Hans‐Gerd , Snijders Henri M. J. , Cramers Carl A. 
Published: May 2005

AbstractIn this work the combination of high‐speed narrow‐bore capillary GC with electron capture detection is evaluated. The make‐up gas flow rate is a key parameter in the successful coupling of narrowbore columns and ECD detection. The make‐up flow has to be as high as possible to eliminate peak tailing caused by the large detection cell volume. The sensitivities at these elevated make‐up flow rates (400 to 1000 ml/min), measured for some pesticides like HCB and dieldrin, were very good. Detection limits for these compounds of 0.1 pg were obtained, resulting in minimum detectable concentrations of approximately 0.2 ppb. The performance of the system is illustrated by several high‐speed analyses of environmentally relevant samples of PCBs and pesticides.
On‐line reversed‐phase liquid chromatography‐capillary gas chromatography using a programmed temperature vaporizer as interface
Authors: Señoráns F. Javier , Herraiz Marta , Tabera Javier 
Published: May 2005

AbstractAn on‐line reversed‐phase LC‐GC method involving the use of a Programmed Temperature Vaporizer (PTV) as interface is used for the rapid analysis of sterols. The experimental procedure requires only the use of commercial HPLC and GC equipments and a Rheodyne valve. The LC preseparation can be performed satisfactorily even with aqueous eluents containing up to 25% water. Factorial experimental design is applied to investigate the sensitivity achievable in the analysis with some variables (adsorbent material used in the PTV, particle size and plug length) being considered at two different levels. As a result, the sensitivty can be increased by a factor as large as 35 merely by performing the analysis under the experimental conditions giving the highest response. The use of the proposed configuration allows the transfer of up to 1050 μL from LC into the GC system, 1400 μL/min being the speed of sample introduction. The proposed procedure was succesfully applied to the analysis of real samples.
Correlation of supercritical‐fluid extraction recoveries with supercritical‐fluid chromatographic retention data: A fundamental study
Authors: Lou Xianwen , Janssen Hans‐Gerd , Cramers Carel A. 
Published: May 2005

AbstractThe possibility of using supercritical‐fluid chromatographic retention data for examining the effects of operational parameters, such as pressure and flow rate, on the extraction characteristics in supercritical‐fluid extraction (SFE) was investigated. A model was derived for calculating the extraction efficiency in SFE from retention data and peak shapes measured in supercritical‐fluid chromatography (SFC). By performing the SFC experiments at the same pressure and temperature as the SFE extractions using the SFE extraction cell as the SFC column, an accurate prediction of extraction efficiencies could be made. Finally, the effects of matrix composition and analyte concentration on extraction efficiency were studied.
Rapid analysis of environmental samples using solid‐phase microextraction (SPME) and narrow bore capillary columns
Authors: Shirey Robert E. 
Published: May 2005

AbstractThe application of SPME, a solventless extraction procedure, is demonstrated for two environmental applications. Extraction of VOCs by SPME is coupled with analysis on short narrow bore capillary gas chromatography columns. The technique is shown both as a fast screening tool and as part of an analytical procedure when combined with a mass spectrometer. Data show the linear range of the procedure. The extraction of chlorinated pesticides from hazardous wastewater and drinking water by SPME is also described in this paper. SPME is compared to traditional extraction procedures with respect to cost, time, ease of use, solvent usage, and sample usage.
GC‐MS analysis of the PCB substitute Ugilec 141 and its occurrence in waste mineral oils
Authors: van der Velde Els G. , Linders Sylvia H. M. A. , Wammes Hans I. J. , Meiring Hugo D. , Liem A. K. Djien 
Published: May 2005

AbstractAfter the restrictions on production and use of PCBs, Ugilec 141, a technical mixture of dichlorobenzyldichlorotoluenes (DBDTs), has been used as a PCB substitute in hydraulic systems. In the Netherlands, the production, import and use of Ugilec 141 has been forbidden since 1988. A method has been developed for the analysis of Ugilec 141 in waste mineral oils to control waste oil import and processing.The method development was based on modification of procedures for the analysis of PCBs in oil and dioxins in fatty matrices and analysis was performed with gas chromatography with mass spectrometry. For sample clean‐up, several combinations of column chromatography with activated carbon, alumina, and silica gel have been tested to obtain extracts free from matrix interferences. An internal standard of 13C‐labeled DBDT was examined to check recoveries from the clean‐up procedures. Quantification was performed by comparison with the six most abundant peaks of an external Ugilec 141 standard mixture. Validation experiments showed a linear range from 0.25 to 60 mg Ugilec 141 kg−1 oil, a reproducibility of 3% and a limit of determination of 0.25 mg Ugilec 141 kg−1 waste oil.The method was applied in a survey of 70 samples of waste mineral oils from producers all over the Netherlands; this revealed levels below the limit of determination and one positive sample with a concentration of 5.7±0.1 mg Ugilec 141 kg−1 oil. In an inspection inquiry, one contaminated oil was found containing 116 ± 9 g Ugilec 141 kg−1 oil.
GC/MS quantitation of hydroquinone, 1,4‐benzoquinone, and 1,4‐cyclohexanedione: One by one and simultaneously
Authors: Molnár‐Perl Ibolya , Tisza Sándor , Korös Endre , Kurin‐Csörgei Krisztina , Szalai István 
Published: May 2005

AbstractA GC/MS study was performed in order to determine 1,4‐benzoquinone, 1,4‐cyclohexanedione, and hydroquinone derivatives on by one and in the presence of each other in different concentrations. Exhaustive investigations, related to the quantitation both of their underivatized compounds and those of their oxime/methoxime and silyl derivatives. Results proved that subsequently to the oximation/methoximation of the carbonyl groups – for the sake of a well shaped and accurately evaluable hydroquinone peak – also silylation is unavoidably necessary. Reproducibility data in the microgram/nanogram level, based on quantitation of their total ion currents and/or those of their selective fragments, were given in details.
Multidimensional gas chromatographic separation of selected PCB atropisomers in technical formulations and sediments
Authors: Benická Eva , Novakovsky Radoslav , Hrouzek Ján , Krupcík Ján , Sandra Pat , Zeeuw Jaap De 
Published: May 2005

AbstractA simple dual‐column gas chromatographic system with a six‐port switching valve has been used to separate the atropisomers of PCB congeners 84, 91, and 95 in technical PCB formulations and in extracts of soil and river sediment. A capillary column coated with a methylphenylsiloxane stationary phase (CP‐Sil 8) was used as the first column, for retention window selection, and a permethylated β‐cyclodextrin (ChirasilDex) capillary column as the main separation column. Because peak overlap could not be eliminated by optimization of column temperature, the enantiomeric ratios of PCB congeners could not be determined from the original chromatograms. The correct enantiomer ratio was determined from the peak areas obtained by deconvolution of the chromatograms. Whereas the PCB atropisomers considered were present in equal concentrations in the technical PCB formulations, analysis of a river sediment sample confirmed different residual concentrations of the atropisomers of congener 95.
Determination of polynuclear aromatic hydrocarbons in environmental samples by Micellar liquid chromatography
Authors: Delgado M. A. Rodríguez , Sánchez Ma J. , González V. , Montelongo F. García 
Published: May 2005

AbstractA method for the separation of polycyclic aromatic hydrocarbons (PAHs) by high‐performance liquid chromatography using a hybrid micellar mobile phase is described. The detection of PAHs was carried out using the fluorescence method with programmable excitation and emission wavelength. The method is applied to the analysis of several environmental samples (sea water, sediments, limpets, sea worms) and several of these compounds are quantitated at concentration below 70 ng L−1(kg−1) in the original samples.
Fast electrophoretic separation of sulfur‐ and selenium‐containig amino acid enantiomers with vancomycin as a chiral selector in coated capillaries
Authors: Vespalec Radim , Billiet Hugo A. H. , Frank Johannes , Luyben Karel Ch. A. M. 
Published: May 2005

AbstractBaseline separation of the enantiomers of the negatively charged 6‐aminoquinolyl‐N‐hydroxysuccinimidyl carbamate (AQC) derivatives of cystine, methionine, ethionine, and their seleno analogs can be achieved in 3–5 min with capillary electrophoresis in polyacrylamide coated capillaries and submillimolar concentrations of vancomycin as the chiral selector.In addition to the vancomycin concentration, the separation is affected by the type, concentration and pH of the buffer. Good buffers are more suitable than phosphate buffer. At pH values above the isoelectric point of vancomycin the mobility difference between the enantiomers becomes smaller. This effect is larger than would be expected from the reversal of the vancomycin migration alone.
Open‐tubular supercritical fluid chromatography with simultaneous flame ionization and chemiluminescent nitrogen detection
Authors: Shi Heng , Taylor Larry T. , Fujinari Eugene M. 
Published: May 2005

AbstractThe use of a simultaneous detection system for open‐tubular supercritical fluid chromatogrphic separation of aniline isomers, alkyl(C8 to C18)dimethylamines, a dialkylmethylamine mixture, and an extract of a Japanese horseradish power “Wasabi” is demonstrated. A chemiluminescent nitrogen detector (CLND) and a flame ionization detector (FID) were configured at the end of the open tubular column via a zero‐ to dead‐volume tee. The dual detection was achieved with a post‐column split at a 1:2.5 ratio for the CLND and FID, respectively. The optimized CLND showed virtually no response to non‐nitrogenous components such as benzene, toluene, and methanol which were used as injection solvents in these applications.
On‐line determination of organochlorine pesticides in water by solid‐phase microextraction and gas chromatography with electron capture detection
Authors: Young Richard , Lopez‐Avila Viorica , Beckert Werner F. 
Published: May 2005

AbstractThis paper describes the extraction of 20 organochlorine pesticides (OCPs) from water samples using solid‐phase microextraction (SPME). Three fused‐silica fibers coated or bonded with polydimethylsiloxane (PDMS) of different film thicknesses (20‐, 30‐, and 100‐μm) were evaluated. The extraction time, the effects of stirring and addition of NaCl to the aqueous sample, the linear range and the precision of this technique, and the effect of carryover were examined for 20 analytes and are presented here. A comparison with results using conventional liquid‐liquid extraction demonstrate that the SPME technique is well suited as a fast screening technique for OCPs in water samples.
GC‐MS headspace analysis of the volatile components of soya oil without heating the sample
Authors: Pinnel Viviane , Vandegans Jacques 
Published: May 2005

AbstractThe analysis of volatile compounds, and particularly of certain hydrocarbons, e.g. pentane, and some aldehydes, e.g. hexanal, has been used to estimate the degree of oxidation of vegetable oil. We have tested a dynamic headspace technique without heating the sample during the purge time of the analysis. Some tests have been performed after heating the sample at 180°C for a specified time before the analysis, to compare the results of analysis with and without heating. The best results were obtained at room temperature.
Development of a method for the rapid determination of pentachlorophenol in leather using supercritical fluid extraction with in situ derivatization
Authors: Meyer Anja , Kleiböhmer Wolfgang 
Published: May 2005

AbstractPentachlorophenol (PCP) was extracted from leather with supercritical carbon dioxide and in situ acetylated under static SFE conditions in the presence of triethylamine. During the dynamic extraction step, the derivatives were removed from the matrix and collected with either a pure liquid (light petroleum) or a liquid‐solid (light petroleum‐solid sorbent (C18, alumina, Florisil or Celite)) trap. To prevent restrictor plugging, a suitable restrictor was designed. The clean‐up of the extracts was optimized in this study. Different internal standards were tested and it was shown that not all of them were usable. The SFE results were compared with those obtained by Soxhlet extraction with methanol. With SFE instead of conventional Soxhlet extraction, the overall time required for determination of PCP in leather can be reduced from about 2 days to approx. 3 hours.
The influence of the carrier gas on retention in capillary gas‐solid chromatography
Authors: Berezkin Viktor G. , Malyukova Irina V. , Alishoev Victor R. , de Zeeuw Jaap 
Published: May 2005

AbstractIn capillary gas‐solid chromatography where interactions between solute and carrier gas and adsorption of the solute on the surface of the adsorbent are considered to be imperfect, it has been shown that chromatographic retention is determined largely by adsorption processes. It has been established that correlation relationships k(P2)=A k(P1) + B, where k is the retention factor, and A and B are equation constants, was valid for use of different carrier gases P1 and P2. Column efficiency could be improved by use of carbon dioxide. The advantages of using carbon dioxide as the carrier gas were investigated.
Practical limits of high speed chromatography: Evaluation with a computer based theoretical model of several commercially available gas chromatographs
Authors: Annino Raymond 
Published: May 2005

AbstractSeveral commercially available chromatographs have been evaluated with respect to their ability to support high speed chromatography. Both autoinjection and trap and thermal pulse injection are both found to be suitable procedures to deliver the required narrow sample injection peak widths. However, even with the appropriate injectors in place, the systems are burdened with relatively slow data acquisition rates and large amplifier time constants that further degrade system performance and make them unsuitable for the high speed chromatography discussed herein. The study was conducted using a computer implemented model of a gas chromatograph's output.
Performance and characteristics of a trace gas analyzer for the determination of volatile organic compounds in air
Authors: Munari Fausto , Mapelli Gian Pietro , Kotzias Dimitrios , Duane Matthew 
Published: May 2005

AbstractAn instrument has been developed and tested for the continuous measurement of volatile organic compounds (VOC) in air. The system consists of a gas chromatograph equipped with a dedicated sampling device that allows the sample to be transferred to a cooled microtrap via sampling loops (10, 100, 250 ml) or via a direct pump transfer to the trap. The microtrap is placed in the chromatographic oven just below a modified split‐splitless injector, allowing direct liquid injection for calibration of the system; the injector is in communication with the sampling valve equipped with the loop and the sampling pump. The system allows 24‐hour sampling and analysis of a large number of VOC (up to 25 individual hydrocarbons ranging from C2C9) and also polar volatile organic compounds PVOC. Thanks to the particular trap geometry, a minimum consumption of liquid nitrogen (between 150300 ml) is needed for each analytical run and no water managing system is normally required for humid air samples.
Trace analysis of semi‐volatile organic air pollutants using thick film silicone rubber traps with capillary gas chromatography
Authors: Ortner Erla K. , Rohwer Egmont R. 
Published: May 2005

AbstractEstablished standard methods for analyzing semi‐volatile pollutants by capillary gas chromatography are cumbersome, time‐consuming, and expensive. With the longer term aim of replacing the sample preparation procedures with convenient concertrating and thermal desorption steps, thick film silicone rubber traps were constructed in a novel multi‐channel configuration. Tests were performed to determine breakthrough volumes and thermal desorption characteristics for total transfer of the trap contents to a capillary column. Initial results are very promising.
Determination of the gas chromatographic elution sequences of the (+)‐ and (−)‐enantiomers of stable atropisomeric PCBs on Chirasil‐dex
Authors: Haglund Peter , Wiberg Karin 
Published: May 2005

AbstractPure enantiomers of chiral (atropisomeric) polychlorinated biphenyls (PCBs) obtained by high‐performance liquid chromatography were used to establish the gas chromatographic elution sequences of the (+)‐ and (−)‐enantiomers of six PCB atropisomers on Chirasil‐Dex. The elution order was found to be (−/+) for PCBs 84, 132, 136, and 176 and (+/−) for PCBs 135 and 174. The retention characteristics of all 19 tri‐ and tetra‐ortho atropisomeric PCBs were also investigated. Nine of the atropisomers could be separated using this chiral selector. PCBs 95, 132, and 149 were completely resovled and PCBs 84, 91, 135, 136, 174, and 176 were partially separated (R = 0.7–0.9). All of the separated congeners are 2,3,6‐substituted in at least one ring, and conversely – none of the congeners that lacks 2,3,6‐substitution could be separated. Thus, chiral recognition and enantiomer separation seems to be strongly governed by 2,3,6‐substitution.
On‐line HPLC‐HRGC coupling and simultaneous transfer of two different LC fractions: Determination of aliphatic alcohols and sterols in olive oil
Authors: Lanuzza Francesco , Micali Giuseppe , Calabrò Giuseppe 
Published: May 2005

AbstractA modified loop‐type interface is decribed which uses two 6‐way valves and concurrent eluent evaporation to perform an on‐line transfer and simultaneous gas chromatographic analysis of two different fractions pre‐separated by liquid chromatography. The interface is used to simultaneously analyze aliphatic alcohols and sterols present in olive oil. LC pre‐separation is carried out using a normal phase column (20 cm × 0.21 cm i.d.) and hexane‐isopropanol (99:1) as a mobile phase at a flow of 0.2 ml/min; for the GC analysis a 5 % phenyl, 95 % dimethyl siloxane (25 m × 0.32 mm i.d., 0.4 μm film thickness) column is used.
Ultratrace determination of 1,2,4‐trichlorobenzene in waste water by purge and trap/gas chromatography coupled to different detectors: Flame ionization (FID), electron capture (ECD), and multiple ion detection‐mass spectrometry (MID‐MS)
Authors: Borrelli Raffaella , Fiorani Tiziana , Golfetto Piero 
Published: May 2005

AbstractHigh resolution gas chromatography (HRGC) coupled to a “purge and trap” extraction‐injection technique is described as a method of determining 1,2,4‐trichlorobenzene in water at levels as low as parts‐per‐trillion (ppt). In order to investigate the interference from other volatile organic compounds (VOCs) several detection systems were compared: flame ionization, electron capture, and mass spectrometry‐multiple ion detection. Concentrations ranging from 15 to 600 ng/L were analyzed in 20 ml standard aqueous solutions. The mean accuracy of the method varied from 89 to 103%, and its mean precision varied from ± 0.85 to ± 7.5 % for all detectors. The detection limits were 20 ng/L for FID, 2 ng/L for ECD and 0.5 ng/L for MID‐MS detectors. The procedure was successfully applied to the analysis of industrial waste waters. The necessity of an appropriate internal standard to improve the quantitative determination and to determine possible losses or degradation of 1,2,4‐trichlorobenzene during handling or storage is discussed.
Relative velocity profile and flow‐rate in sedimentation field‐flow fractionation
Authors: Martin Michel 
Published: May 2005

AbstractAlthough the classical retention theory is used for interpreting data or optimizing separations in sedimentation field‐flow fractionation (SedFFF), as in most other field‐flow fractionation techniques, the assumption of a parabolic flow profile on which this theory is based is not rigorously correct in SedFFF because of the curvature of the channel walls. In order to examine quantitatively the influence of this effect, the relative velocity profile in SedFFF is obtained by solving the Navier‐Stokes equation in cylindrical coordinates. Discrepancies found in the literature about the definition of the mean velocity in such channels are discussed. Relationships between mean velocity, flow‐rate and pressure gradient are given.Approximating the velocity profile by a third‐degree polynomial of the radial coordinate which provides the same slope as the exact profile at a reference wall, for small values of δ, the curvature ratio (ratio of the channel thickness to the mean curvature radius), shows that the adjustable parameter of the approximate profile, ν, is equal to ± δ/3, the sign depending on whether the reference wall is the inner or outer wall. The curvature ratio appears to be a good indicator of the error made on retention when using the straight channel approximation in retention theory. The error is quite small for typical SedFFF channels. It may have to be taken into account for precise determinations if thicker channels and/or miniaturized systems are used.