bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of fatty acid methyl esters as minor components of fish oil by multidimensional GC‐MSD: New furan fatty acids
Authors: Wahl Hans Günther , Liebich Hartmut M. , Hoffmann Andreas
Published: May 2005

The separation and analysis of furan fatty acids and other minor component fatty acids present at very low concentrations in complex sample matrices, such as fish oil or lipids derived from liver and testes, require several pre‐analytical separation steps if single column gas chromatography is to furnish sufficient resolution: after extraction and transesterification hydrogenation, urea complex precipitation and argentation TLC have been applied prior to GC analysis of furan fatty acids.

By using multidimensional GC‐MSD with cooled injection and flow‐controlled column switching with intermediate cold trapping, it has been possible to identify directly the methyl esters of furan fatty acids without further pre‐analytical separation.

The most common of the furan fatty acids can be subdivided into two groups depending on whether they bear a propyl or pentyl side group in the 5‐position of the furan ring. In addition to the eight furan fatty acids known to be present in fish oil, six new ones were identified, four with propyl substitution and two with pentyl substitution. Four have earlier been reported to be present in the hepatopancreas of crayfish and in fish tissue, whereas the propyl‐substituted 16,19‐epoxy‐17,18‐dimethyldocosa‐16,18‐dienoic acid and the pentyl‐substituted furan fatty acid 6,9‐epoxy‐7‐methyltetradeca‐6,8‐dienoic acid were hitherto unknown.
Determination of sulfur components in natural gas: A review
Authors: Tuan Hai Pham , Janssen Hans‐Gerd , Cramers Carel A. , Smit André L. C. , van Loo Ellen M.
Published: May 2005

More stringent environmental regulations as well as higher demands presently being imposed on the sulfur content of natural gas feed‐stocks for chemical processes necessitate the development of new analytical procedures for sulfur determination in natural gas. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. The complexity of the natural gas matrix as well as the extremely low concentration levels at which the sulfur species occur make the development of these analytical methods a true challenge. In this review the three steps common for analytical methods for trace analysis in complex matrices, i.e. pretreatment, chromatographic separation, and detection, are discussed in detail. Possible methods for calibration of the system are discussed in the final section.

Various techniques to determine sulfur in natural gas are described. Depending on the application, the most suitable system has to be selected. For example, for on‐line application in a hazardous area a simple and rugged system is required, i.e. a simple gas chromatograph with a flame photometric detector, while for laboratory application a more complex instrument including preconcentration, column switching, and more exotic detection systems could be more suitable. Therefore it is crucial to define the requirements of the instrument at an early stage and use the information in this review article to develop/select a dedicated instrument/procedure for the problem at hand.
Characterization of fuel samples by on‐line LC‐GC with automatic group‐type separation of hydrocarbons
Authors: Trisciani A. , Munari F.
Published: May 2005

Characterization of fuels by LC‐GC is possible by use of automatic successive transfer (multiple transfer) of HPLC fractions to a GC via an on‐column interface. This paper describes the instrumentation and the methodology for the HPLC separation of the hydrocarbons (aliphatic and aromatic) into separate groups and the on‐line transfer of these groups to a capillary GC column. Two HPLC methods were used with the same valve configuration: single column (silica) with column back‐flush to detector; and double column (silica and amino‐bonded silica) with multiple fraction transfer and back‐flush. The first method was used for the analysis of total saturated compounds and total aromatic compounds; the second was used for the separation of the one‐, two‐, three‐, and four‐ring aromatic compounds present in diesel fuels. Examples are shown of the characterization of diesel fuels, and the repeatability of the data.
Molecular characterization of organically‐bound sulfur in crude oils. A feasibility study for the application of Raney Ni desulfurization as a new method to characterize crude oils
Authors: Damsté Jaap S. Sinninghe , Rijpstra W. Irene C. , de Leeuw Jan W. , Lijmbach Gerard W. M.
Published: May 2005

Five crude oils with varying sulfur contents (0.1 – 4.7%) were characterized on a molecular level for organically‐bound sulfur. Aromatic fractions were analyzed by GC‐(MS) and asphaltene and polar fractions were analyzed by flash pyrolysis‐GC‐(MS). The polar fractions were also desulfurized with Raney Ni and the hydrocarbons formed were analyzed by GC‐MS. Major sulfur compounds in the aromatic fractions were identified as alkylbenzo‐ and alkyldiben‐zothiophenes. The flash pyrolyzates of the asphaltene contained alkylthiophenes and alkylbenzothiophenes as major compounds, depending on the thermal maturity of the oil. Generally, the sulfur‐rich crude oils contained relatively more sulfur compounds. The flash pyrolyzates of polar fractions contained a variety of sulfur compounds (alkylthiolanes, alkylthianes, terpenoid sulfides, alkylbenzothiophenes) with substantial differences between different crude oils. Raney Ni desulfurization of the polar fraction yielded hydrocarbons dominated by n‐alkanes, but isoprenoid alkanes, n‐alkylcyclohexanes, mid‐chain methylalkanes, tricyclic terpanes, hopanes and steranes were also present. These hydrocarbons show a potential to fingerprint crude oils since their distribution patterns are more characteristic than those of the hydrocarbons present in the saturated hydrocarbon fraction.
Coupled SFE/SFC/GC for the trace analysis of pesticide residues in fatty food samples
Authors: Nam Ki‐Souk , King Jerry W.
Published: May 2005

An on‐line SFE‐chromatographic system, where SFE has been coupled with SFC and GC, was developed and utilized for trace analyses of organochlorine and organophosphorus pesticide residues from gram‐sized complex sample matrices, such as chicken fat, ground beef, and lard. The SFE process and chromatographic techniques were instrumentally integrated for efficient and automated on‐line analysis, having minimal sample handling between the sample preparation and separation steps. A cleanup step, incorporating packed column SFC, allowed the fractionation of relatively small‐sized, non‐polar pesticides from the co‐extracted fatty materials. This permitted final high‐resolution separation of analytes on a capillary GC column. Detection of pesticides was accomplished using selective electron‐capture and nitrogen‐phosphorus detectors. Pesticide concentrations determined with the on‐line system were accurate and reproducible, for fatty samples containing both fortified and incurred pesticides. This method, utilizing supercritical carbon dioxide, was considerably faster and less laborious than the conventional analytical procedures based on liquid extraction.
Improving GC‐MS screening analysis by functional‐group‐related silica gel fractionation of industrial wastewater extracts
Authors: Reemtsma Thorsten , Jekel Martin
Published: May 2005

The separation of the components of complex industrial waste water extracts according to their functional groups has been accomplished by use of small silica gel columns eluted with a hexane – dichloromethane – methanol gradient. The six fractions obtained covered a polarity range from aliphatic fatty acids to (aromatic) polyhydroxy and polyether compounds. Recovery of model compounds was between 75 and 105%.

Used prior to GC‐MS analysis this fractionation substantially enhances chromatographic resolution and facilitates peak identification. The procedure was exemplarily applied to an extract of anaerobically treated tannery waste water. Phenols, aromatic acids, and aromatic and aliphatic (poly)hydroxy acids, in the low ppm range, were determined as main constituents. Since fractionation extends the range of detection, trace substances such as chlorocresol, dichlorobenzoic acid, mercaptobenzothiazole, and mercaptoacetic acid were also detectable at the ppb level.
Capillary zone electrophoresis with indirect UV detection: Determination of sodium dodecyl sulfate in simulated stream water
Authors: Gibbons Jean M. , Hoke Steven H.
Published: May 2005

SDS (sodium dodecyl sulfate) has been quantitatively determined by capillary zone electrophoresis using a fused silica capillary and a 5 mM dihydroxybenzoic acid / sodium hydroxide buffer in 5% methanol solution at a pH of 8.1. The ion was detected by indirect UV absorption at 250 nm. Detection range was from 0.8 to 50 mg SDS/L. This rapid method requiring only small sample volumes was developed in support of an aquatic toxicology study in a simulated stream water and is applicable to waters containing common inorganic ions.
Capillary zone electrophoresis of neutral organic molecules in organic – aqueous solution
Authors: Shi Youchun , Fritz James S.
Published: May 2005

Very good separations of non‐ionic organic compounds have been achieved by capillary zone electrophoresis (CZE) using a tetrahep‐tylammonium salt as an additive in aqueous acetonitrile as solvent. A systematic study was undertaken to determine the effect of experimental parameters on electroosmotic mobility and electro‐phoretic mobility. It was found that pH, acetonitrile concentration, and the type and concentration of quaternary ammonium salt are important experimental variables. Under appropriate conditions, the separation window was enlarged and a broad range of electrically neutral organics, including very hydrophobic compounds (e. g. poly‐cyclic aromatic hydrocarbons) and fairly hydrophilic compounds were separated in a relatively short time. By adjusting the separation conditions, high resolution CZE of a specific group of neutral organic compounds could be achieved. A method for calculation of capacity factor was proposed and capacity factors for a variety of non‐lonic organic compounds were calculated.
Splitless injection of large volumes of aqueous samples: Further experience. Experiments on analyzing triazines by direct injection of drinking water
Authors: Grob Konrad , Fröhlich Dieter
Published: May 2005

Conditions were optimized for the introduction of large volumes of drinking water by splitless injection with vapor overflow, experimenting with the determination of triazines. No co‐solvent was added, and the maximum injection volume was 400 μl. A vapor outlet beyond a coated precolumn was used to discharge water vapors released belatedly from the packing. Using alkali flame ionization detection (AFID), detection limits were around 0.5 μg/l.
Detection of nitro musks in human fat by capillarv gas chromatography with atomic emission detection (AED) using programmed temperature vaporization (PTV)
Authors: Linkerhägner Manfred , Stan Hans‐Jürgen , Rimkus Gerhard
Published: May 2005

Atomic emission detection (AED) has been successfully applied to the determination of nitro musks in the fat of human adipose tissue by gas chromatography at trace concentration levels. Element specific detection with the AED combined with a clean‐up procedure for nonpolar substances makes target screening analysis for lipophilic nitro aromatic compounds possible for the first time. The lack of sensitivity, especially in the AED nitrogen and oxygen trace, was compensated by higher concentration of the extracts and injection of larger sample volumes performed by cold programmed temperature vaporization (PTV) in the solvent split mode. The combination of the superior quantification properties of the atomic emission detector with large sample volume introduction makes the quantification of nitro musks down to the ppb level possible. All five nitro musks investigated exhibit linear dynamic ranges going down close to instrumental limits of detection. Moreover, organochlorine compounds could be sensitively detected in the same sample extract by the AED chlorine trace without any interferences from coeluting matrix compounds.
PCB separation by HRGC‐MS. Fourier analysis for characterizing Aroclor chromatograms
Authors: Pietrogrande Maria C. , Pasti Luisa , Dondi Francesco , Rodriguez Maria H. Bollain , Diaz Maria A. Carro
Published: May 2005

Aroclor and Aroclor mixture chromatograms obtained using temperature programmed high resolution capillary GC coupled with mass spectrometric selective detection have been investigated by Fourier analysis developed for the study of multicomponent chromatograms. The experimental autocorrelation function (EACF), i.e. peak shape and position correlation, showed a retention ‐ structure pattern which could be associated with both the type of Aroclor and the ion used for selective ion monitoring (m/z value). In particular, o‐m and m‐m isomerization effects were singled out by EACF analysis. By fitting EACF with previously developed theoretical models, it was possible to characterize a specific Aroclor in terms of the number of PCB congeners present in it. The results obtained agreed closely with the typical Aroclor content. For the Aroclor mixture, the distribution of inter‐distance between successive peaks was derived. The two first distribution moments obtained agreed with those derived from retention data reported in the literature. The consequences on the separation performance, i.e. the number of singlets, doublets, etc. in the chromatogram, are discussed.
Gas chromatographic separation of polychlorinated biphenyls on a new apolar capillary column
Authors: Vetter Walter , Luckas Bernd , Biermans Frans , Mohnke Manfred , Rotzsche Harald
Published: May 2005

Eighty one polychlorinated biphenyls (PCBs) and nineteen chlorinated pesticide standards have been analyzed on a newly developed apolar high resolution gas chromatography (HRGC) column. Emphasis was placed on the determination of PCB indicator congeners which are part of national regulations, and of toxic coplanar PCB congeners.

The new column enables almost unambiguous quantification of the PCB indicator congeners (PCB 138 can be separated from both PCB 163 and PCB 164; PCB 28 and PCB 31 were also separated and no coelution was observed for PCB 52, PCB 118, and PCB 180). The new column furnished better results than CP‐Sil 8 for the analysis of PCB indicator congeners in a sample of seal blubber.
Volatile enrichment on automatic static headspace using a precolumn and stopping the carrier gas flow during injection
Authors: Barcarolo Robertino , Casson Pierino
Published: May 2005

The aim of this study was to develop a technique for performing automatic static headspace analysis of volatiles without a cryogenic device. Reconcentration of solutes was accomplished using a graphitized carbon coated precolumn between two splitting points and stopping carrier gas flow during injection. Chromatographic profiles of volatile compounds from ground coffee compared with split and splitless injections provide confirmation of the good sensitivity of the technique. The analysis of a standard mixture covering a wide range of volatility confirms that the described technique might be useful to achieve enrichement of low volatile headspace compounds, even if discrimination against the various components is present.
Artifact formation from the use of potassium‐iodide‐based ozone traps during atmospheric sampling of trace organic gases
Authors: Helmig Detlev , Greenberg Jim
Published: May 2005

Trace atmospheric gases have been sampled using potassium‐iodide‐based reactant traps for ozone removal. GC‐MS analysis revealed the presence of organic iodine compounds which were present neither in the atmosphere nor as contaminants of the materials used, but more likely arose from reactions of organic gases or aerosols sampled with reactive iodine or hypoiodite released from reaction of ozone with potassium iodide in the traps. Losses of the individual organic trace gases measured were not, however, observed as a result of this mechanism. Several cautions in identifying unknown compounds from the atmosphere when using potassium iodide ozone traps are discussed.
Determination of organophosphorus pesticides in whole/chocolate/skim‐milk and infant formula using solid‐phase extraction with capillary gas chromatography/flame photometric detection
Authors: Ronald Erney D.
Published: May 2005

Twenty nine organophosphorus pesticides (OPPs) are identified on a DB‐17 capillary column using gas chromatography‐flame photometric detection (GC‐FPD). An acetone‐acetonitrile mixture is used to initially extract OPPs from milk and infant formula samples, followed by partition of the analytes into dichloromethane (DCM). Dichloromethane is removed on a rotary evaporator and the residue taken up in acetonitrile (ACN) for cleanup on a C‐18 (octadecylsiloxane bonded silica) (SPE) cartridge. ACN eluate is evaporated under nitrogen and the residue taken up in acetone for GC‐FPD determination.

Initial studies showed mean recoveries for 28 of 29 OPPs in whole milk fortified at 0.10 ppm ranged between 69 and 99% with a relative standard deviation (RSD) of 1.0–9.7%. Whole/chocolate/skim‐milk and four infant formula products fortified at 0.02 ppm gave mean recoveries of 64–103% with RSDs between 1.9 and 20.9% for 24 of 29 OPPs. Excluding skim milk, recoveries for Dichlorvos, Methamidophos, Mevinphos E, and Acephate ranged between 47 and 89%. Sample extracts were extremely clean and posed no difficulty to the GC system. The procedure is faster and less costly than Association of Official Analytical Chemists (AOAC) procedures and allows for determination of a broad spectrum of OPPs.
Capillary GC on 50 micrometer I.D. Columns coated with thick films. Theory and selected practical results
Authors: Steenackers Dirk , Sandra Pat
Published: May 2005

The chromatographic performance of 50 μm internal diameter (i.d.) fused silica columns coated with up to 2 μm films of immobilized SE‐54 (methyl phenyl (5%) silicone) is evaluated under gas chromatographic conditions. The influence of pressure drop on the plate height is discussed. In comparison to thick film 250–530 μm i.d. columns, much higher efficiencies and faster analyses are obtained. Practical examples, performed on a standard GC instrument, illustrate the features of thick film 50 μm i.d. columns.
Quantitative analysis of selected PCB congeners in marine matrix reference materials using a novel cyanobiphenyl stationary phase
Authors: Hillery Barbara R. , Girard James E. , Schantz Michele M. , Wise Stephen A.
Published: May 2005

A novel p,p‐cyanobiphenyl stationary phase (p‐cyanobiphenyl, p‐allyloxy methylpolysiloxane) has been evaluated for the GC investigation of polychlorinated biphenyls (PCBs). Several PCB congeners which coelute on the phases typically used for PCB analysis (e.g. 5% phenyl methylpolysiloxane) are separated on the p,p‐cyanobiphenyl phase, including the hexachlorobiphenyl congeners PCB 163, PCB 164, and PCB 138. In this work, a p,p‐cyanobiphenyl stationary phase was used to measure selected PCB congeners in two Standard Reference Materials (SRMs) available from the National Institute of Standards and Technology (NIST), and two Certified Reference Materials (CRMs) available from the Community Bureau of Reference (BCR). The materials analyzed were SRM 1588, Organics in Cod Liver Oil; SRM 1945, Organics in Whale Blubber; CRM 349, Chlorobiphenyls in Cod Liver Oil; and CRM 350, Chlorobiphenyls in Mackerel Oil. Concentrations are reported for several PCB congeners which coelute on the 5% phenyl methylpolysiloxane, including PCB 163 and PCB 164.
Solid phase microextraction/isothermal GC for rapid analysis of complex organic samples
Authors: Górecki Tadeusz , Pawliszyn Janusz
Published: May 2005

Solid phase microextraction (SPME) was used as the sample introduction technique for high‐speed isothermal GC. An injector dedicated for SPME fiber injection was designed and built. The injector was operated in two modes, continuously heated and flash heated. The latter mode proved to be better for high‐speed separations. The injector was then used for sample introduction in separation of BTEX. When sampling directly from water with a fiber having a 56 μm thick poly(dimethylsiloxane) coating, the BTEX components were separated under isothermal conditions in ca. 18 s. A fiber with a thinner coating (15 μm) enabled the separation to be completed in ca. 12 s when sampling from headspace. In both cases the results were highly reproducible, as measured by the estimated values of the relative standard deviation.
Micellar electrokinetic chromatography in coated capillaries: Determination of micelle–aqueous partition coefficients
Authors: Janini George M. , Muschik Gary M. , Issaq Haleem J.
Published: May 2005

A micellar electrokinetic chromatography method is presented for the determination of the partition coefficient for the distribution of nonpolar and moderately polar solutes between the micelle and the aqueous phases in aqueous micellar solutions. In comparison with the literature the method is, theoretically and experimentally, the most straightforward for this application. An equation is derived for the determination of the partition coefficient in a coated fused silica capillary, with neglible electroosmotic flow, from simple measurements of the migration times of solutes and a marker for micelle migration. The advantages and limitations of this method are discussed. The method is tested by using sodium dodecylsulfate (SDS) surfactant and naphthalene, benzene, toluene, and phenol solutes. Micellar electrokinetic chromatography in coated columns isideally suited for the separation of hydrophobic solutes in aqueous samples.
Optimization of separations of alkyl‐substituted phenolate anions by capillary zone electrophoresis
Authors: Benz Nancy J. , Fritz James S.
Published: May 2005

Anions of alkylphenols have very similar electrophoretic mobilities in CZE owing to their very small differences in size and the narrow range of their pKa values. By studying electrophoretic mobility as a function both of pH and of the amount of acetonitrile in the electrolyte solution, optimum separation conditions were determined. It was possible to separate a group of methyl‐substituted phenols, including several positional isomers. Mixtures containing n‐propyl and isopropyl phenols and 1°, 2°, and 3° butylphenols could be resolved.
HPLC separation of the enantiomers of racemic benzergoline derivatives on a chiral binaphthalene covalently bonded to silica gel
Authors: Küsters Ernst , Dosenbach Cornelia
Published: May 2005

A novel chiral stationary phase (CSP) derived from the atropisomeric enantiomer S‐3,3′‐dicarboxy‐2,2′‐dihydroxy‐1,1′‐binaphthyl (S‐DDBN) has been synthesized and its use for the separation of enantiomers demonstrated. The chiral selector is covalently bonded to amino‐functionalized silica gel, thus enabling the use of alcohols as mobile phases. Good chiral discrimination was obtained for the pharmacologically interesting class of benzergoline derivatives which act as selective dopamine D1 receptor agonists. This paper reports the successful separtion of fifteen structurally related benzergoline racemates with separation factors up to 3.5. The influence of small differences in molecular structure on chiral discrimination was examined.
Gas chromatographic separation of the enantiomers of flumecinol and some related compounds
Authors: Reinhardt R. , Engewald W. , Görög S.
Published: May 2005

Flumecinol and related compounds can, without derivatization, be separated into their enantiomers by gas chromatography on cyclodextrin phases; permethylated β‐cyclodextrin dissolved in OV‐1701 can be particularly recommended. Thermodynamic data describing the different intensities of interaction of the individual enantiomers with the stationary phases were determined. The values measured imply different separation mechanisms for the compounds investigated.
An automatic sampling device for capillary zone electrophoresis
Authors: Kaljurand M. , Ebber A. , Somer T.
Published: May 2005

An automatic sampling device has been developed for capillary zone electrophoresis. The sample is introduced to the column electrokinetically by rapidly exchanging buffer for sample in a narrow channel drilled in a plexiglass block. The autosampler is capable, under computer control, of performing multiple sample injections from a large volume sample source (such as a reaction vessel) as the sample concentration changes, and thus presents the possibility of analyzing time‐varying processes by CZE. Peak area reproducibility in electropherograms obtained after use of the sampler is less than 1% and efficiency is more than 2.2 × 105 theoretical plates.
Characterization of silicones by direct‐deposition GC/FT‐IR
Authors: Bonanno Anthony S. , Griffiths Peter R.
Published: May 2005

Materials used in the manufacture of silicone breast prostheses were analyzed by supercritical fluid chromatography (SFC) and high temperature gas chromatography (GC) coupled with direct deposition FT‐IR detection. The chromatographic resolution and deposition quality were found to be unsatisfactory for SFC/FT‐IR; however, high temperature GC/FT‐IR produced excellent results. The chromatograms and spectra obtained allowed for the identification of poly‐dimethyl silicones and mono‐, di‐, and tri‐diphenylsubstituted poly‐dimethyl silicones. An automated method of baseline correction was developed that allowed functional group chromatograms due to molecules containing Si‐phenyl bonds to be constructed without significant interference from Si‐methyl bonds despite the fact that the Si‐C stretching mode of Si‐phenyl bands overlapped significantly with the strong bands due to Si‐CH3 groups.
Use of capillary gas chromatography/sensory analysis as an additional tool for sampling technique comparison in peach aroma analysis
Authors: Rizzolo Anna , Lombardi Patrizia , Vanoli Maristella , Polesello Stefano
Published: May 2005

Capillary GC/sensory analysis was used to judge if dynamic headspace on sliced pulp and on intact fruit, and solvent extraction could collect the “character impact” and the “contributory” aroma compounds in peaches. Capillary GC/sensory data showed that the headspace techniques selectively recovered the “contributory” volatile compounds, which are strictly related to the characteristic odor of the various peach cultivars, whereas solvent extraction better quantified the “character impact” compounds (lactones).
Chromatographic quantitation using fractions of the peak areas
Authors: Pires Valente Antonio L. , Augusto Fabio , da Rocha Eduardo Carasek
Published: May 2005

Quantitative chromatographic analysis is liable to errors due to peak asymmetry because the uncertainty in the detected position of the end of the peak tail decreases the reliability of the computed peak area. This dependence may be a severe drawback whenever peaks of different areas must be compared, as in the case of calibration curves. A new approach to overcome the uncertainties of area calculation due to peak asymmetry is reported in this paper. The approach consists of calculating only the area included between the start and the maximum of the chromatographic peak. Simulated and experimental chromatographic data were used in this study. Both the peak start‐to‐peak maximum area (SMA) and the start‐to‐end or total area (TA) were calculated and the quantitative results were compared. Within the scope of this work it is concluded that the SMA yields calibration curves that are more linear and have intercepts closer to zero than the calibration curves obtained using the TA.
A window diagram for key component analysis in on‐line gas chromatography
Authors: Villalobos Richard
Published: May 2005

Window 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

Two 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

In 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

An 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

The 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

The 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

After 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

A 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

A 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

A 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

Baseline 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

The 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

This 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

The 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

Pentachlorophenol (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

In 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

Several 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

An 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

Established 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

Pure 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

A 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.