bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupled solid phase extraction–supercritical fluid extraction–on‐line gas chromatography of explosives from water
Authors: Slack Gregory C. , McNair Harold M. , Hawthorne Steven B. , Miller David J. 
Published: May 2005

AbstractA method has been developed for the quantitative extraction of nitrotoluenes (2,3‐dinitrotoluene, 2,4‐dinitrotoluene and trinitrotolugene) from water using a BakerbondTM phenyl sorbent. The average solid phase extraction recoveries for spiked standards ranged from 80 to 95 percent for reagent water and 52 to 95 percent from well and surface water in the low ppb and ppt levels. After the nitrotoluenes had been trapped on the solid sorbent they were quantitatively eluted using SFE. Adding toluene to the extraction cell increased the rate of extraction, but did not improve analyte recovery versus unmodified CO2. The extracts were analyzed off‐line with GC–ECD using an internal standard. Extraction losses were due to analyte breakthrough, and not from poor SFE recoveries. This demonstrates that supercritical fluid extraction is a suitable elution technique for analytes trapped on solid phase extraction sorbents.Also, a method for the direct on‐line coupling of SPE to GC, using SFE, has been developed and evaluated. Supercritical CO2 is ideal for directly coupling SPE to GC, since carbon dioxide is a gas under ambient conditions. One potential problem of on‐line SPE–SFE–GC is the presence of residual water trapped on the active sites of the Bakerbond13 phenyl sorbent. This problem was dealt with by using a split interface previously described by Hawthorne. From the results of this study, the relative standard deviation of the on‐line SPE–SFE–GC interface was determined to be between 4 and 10 percent. In addition, there was no significant difference in the precision of the method with or without the use of an internal standard. A calibration curve was also constructed (r2 = 0.995) from spiked controls, demonstrating that the method is quantitative.
An homologous series of benzodiazepine retention index standards for gas chromatography
Authors: Rasanen Ilpo , Ojanperä Ilkka , Vuori Erkki , Hase Tapio A. 
Published: May 2005

AbstractAn homologous series of benzodiazepine retention index standards (the R‐series) has been synthesized and the gas chromatographic behavior of the series investigated on NB‐54 and NB‐1701 capillary columns. The compounds were stable, exhibited symmetrical peak shapes, and fairly linear retention behavior was observed on both columns. The series can be coinjected with every sample to enable the high precision analysis of toxicological samples; screening for 20 benzodiazepine drugs was possible in 23 minutes (including cooling). The R‐series method was compared with a retention index method based on a series of benzodiazepine drugs as standards and with a method employing relative retention times. The precision of the R‐series method was found to be generally better than that of the two other methods in both long‐ and short‐term studies.
Supercritical fluid extraction of nylon 6: An investigation into the factors affecting the efficiency of extraction of caprolactam and its oligomers
Authors: Venema Arnold , van de Ven Henk J. F. M. , David Frank , Sandra Pat 
Published: May 2005

AbstractCaprolactam and oligomers can be efficiently extracted from nylon 6 by use of supercritical fluid extraction with carbon dioxide containing 7.5 % (m/m) methanol as the extraction fluid. The application of a static extraction, using an additional amount of methanol, is necessary to obtain high extraction efficiencies.
Derivatized cyclodextrins for the separation of enantiomers in capillary electrophoresis
Authors: Schmitt Thomas , Engelhardt Heinz 
Published: May 2005

AbstractThe use of cyclodextrin derivatives for the efficient separation of enantiomeric drugs is described. Hydroxypropylation, methylation or carboxymethylation of the cyclodextrin not only result in a better solubility of the cyclodextrin in aqueous solutions, but also favor, via additional hydrogen bonding, the stabilization of one of the cyclodextrin‐analyte complexes. The influence of the background electrolyte on peak shape is also described here. Carboxymethylated cyclodextrin can be used in similar manner to uncharged cyclodextrins at low pH values (below 4). At pH values above 5, however, its charge also allows the separation of uncharged enantiomers as in a micellar‐like system.
Real‐time control of column switching in multidimensional gas chromatography
Authors: Himber Kimmo , Sippola Erkki , David Frank , Sandra Pat 
Published: May 2005

AbstractIn chromatography the separation power expressed in terms of peak capacity can be greatly enhanced by multidimensional techniques. The most important aspect of multidimensional chromatography is the precise location of the heart‐cut window. Very often the reliability of this positioning is ensured by applying relatively large heart‐cuts; this reduces the intrinsic selectivity offered by the technique.The best way of locating peaks in chromatography is by means of retention indices. This technique can also be used in multidimensional chromatography. A method is described whereby the heartcut window in multidimensional gas chromatography (MDGC) can be defined precisely.
Trapping efficiencies of various collection solvents after supercritical fluid extraction
Authors: Thompson Peter G. , Taylor Larry T. , Richter Bruce E. , Porter Neil L. , Ezzell John L. 
Published: May 2005

AbstractA polarity test mix consisting of acetophenone, N, N‐dimethylaniline, naphthalene, decanoic acid, 2‐naphthol, and n‐tetracosane was spiked onto sand, and extracted with supercritical carbon dioxide, to evaluate the collection efficiency of various solvents and solvent mixtures. Nine single collection solvent systems and four mixed collection solvent systems were studied. When one‐component collection solvents were employed, quantitative (above 90%) recovery of all analytes was not possible. With mixed collection solvents, recoveries of 90% or better with all analytes studied were possible.
Dual‐column GC analysis of mediterranean fish for ten organochlorine pesticides and sixty two chlorobiphenyls
Authors: Rahman M. S. , Bøwadt S. , Larsen B. 
Published: May 2005

AbstractThe simultaneous analysis of α‐HCH, β‐HCH, γ‐HCH, HCB, p,p′‐DDD, p,p′‐DDT, p,p′‐DDE, o,p′‐DDT, mirex, dieldrin and 62 chlorobiphenyl congeners on two parallel capillary GC columns of different polarity is described for nine Mediterranean fish species. Ten commercially available columns with stationary phases completely characterized in respect of their PCB elution patterns were considered for dual‐column GC‐ECD analysis. The combination of a 60 m × 0.25 mm i.d. column coated with a 0.25 μm film of 50% diphenyl dimethylsiloxane and a series combination of a 25 m × 0.25 mm i.d. column coated with a 0.25 μm film of 5% diphenyl dimethylsiloxane with a 25 m × 0.22 mm i.d. column coated with a 0.10 μm film of 1, 10‐dicarba‐closo‐dodecarborane dimethylpolysiloxane furnished the highest number of separated chlorobiphenyl congeners (104). The dual‐column GC system performed with high stability and reproducibility over a broad concentration range (1–3000 ng/g lipid) of the organochlorine compounds in the investigated fish.
A method for reproducible preparation of chiral polysiloxanes with regular repeat units as stationary phases for capillary gas chromatography
Authors: Abe Iwao , Nishiyama Takako , Frank Hartmut 
Published: May 2005

AbstractTrifluoroethyl ester‐functionalized polysiloxanes can be prepared by block condensation of 3‐dichloromethylsilyl‐2‐methylpropionic acid 2′,2′,2′‐trifluoroethyl ester with 1,5‐bis(diethylamino)hexamethyltrisiloxane or with disodium tetramethyldisiloxane‐1,3‐diolate. The functionalized polysiloxanes may serve as supports for a variety of selector groups; for instance, nucleophilic displacements with L‐valine‐t‐butylamide or L‐α‐naphthylethylamine lead to chiral polysiloxanes in high yields and with high reproducibility. Imidazole accelerates the rate of nucleophilic displacement. Capillary columns coated with such chiral polysiloxanes exhibit high enantioselectivity and thermostability.
The selectivity and polarity of carbon layer open tubular capillary columns modified with a polar liquid phase
Authors: Castello Gianrico , Vezzani Sonia , Moretti Paolo 
Published: May 2005

AbstractThe polarity of carbon layer open tubular (CLOT) columns coated with a layer of non‐porous graphitized carbon black (Carbopack B) modified with an appropriate amount of polar polyglycol liquid phase has been evaluated and compared with that of standard polar (Supelcowax‐10) and non‐polar (SPB‐1) bonded phase open tubular columns. The efficiency and selectivity were measured at various temperatures and the polarity of the columns was evaluated by use of McReynolds' constants and the difference in apparent carbon number, ΔC of linear alkanes and alcohols. The polarity of the CLOT column was found to depend on temperature, and changing the analytical conditions therefore enabled the separation of compounds of different polarity whose reciprocal position and resolution were affected by temperature. The application of calculation methods which enable programmed temperature retention times to be predicted from isothermal data was also found to be possible when the polarity of the CLOT column changes with temperature.
High performance liquid chromatography on the chiral stationary phase (R,R)‐DACH‐DNB using carbon dioxide‐based eluents
Authors: Gasparrini Francesco , Maggio Francesco , Misiti Domenico , Villani Claudio , Andreolini Franca , Mapelli Gian Pietro 
Published: May 2005

AbstractFast and efficient separations of chiral stereolabile compounds were obtained at very low temperature on a π‐acid chiral stationary phase (R,R‐DACH‐DNB) using carbon dioxide‐based mobile phases containing alcoholic polar modifiers.Furthermore, efficient separations of the newly discovered spherical carbon cluster buckminsterfullerene (C60) and the related higher fullerenes (C70, etc.) have been performed on the same stationary phase using eluents based on either n‐hexane or carbon dioxide.
Analysis of sorbitan ester surfactants. Part II: Capillary supercritical fluid chromatography
Authors: Wang Zhendi , Fingas Merv 
Published: May 2005

AbstractA rapid, simple and quantitative approach to the separation and identification of sorbitan ester surfactants has been developed using capillary supercritical fluid chromatography (SFC). The sorbitan ester surfactants were well separated into five groups: starting materials and mono‐, di‐, tri‐, and tetraesters, with each group consisting of a number of peaks representing different isomers. High purity glycerides of fatty acids were employed to estimate the relative response factors of sorbitan esters, and reliable group‐wise integration served for quantitation of the distribution of sorbitan fatty acid esters. A very important parameter, hydrophilic–lipophilic balance (HLB), which describes the hydrophilic and hydrophobic characteristics of surfactants, could be correlated with the distribution of the sorbitan esters. A combination of solid‐phase extraction (SPE) and SFC was used to separate, concentrate, and analyze Span‐20 from salt‐water samples. In comparison with the HPLC method, capillary SFC broadens the scope of the technique to encompass high molecular weight sorbitan polyesters while maintaining high separation efficiency.
Methodological approach for evaluating operational parameters and the characterization of a popular sorbent for solid‐phase extraction by high pressure liquid chromatography
Authors: Miller Kenneth G. , Poole Colin F. 
Published: May 2005

AbstractThe kinetic and retention properties of a silica‐based octadecylsiloxane bonded phase sorbent used in solid‐phase extraction (SPE) were determined by high pressure liquid chromatography (HPLC). This sorbent had a high bonded phase density resulting in a material with very low intraparticle porosity. This led to favorable retention and mass transfer properties over the normal sampling flow rate range. Typical cartridges for SPE have a low and variable packing density which is recognized as a significant cause of poor sampling performance and, under some circumstances, results in poor repro‐ducibility. The apparent particle size for the sorbent at 55–57 μm is considerably larger than generally indicated in the trade literature but this is not detrimental to its use for SPE since sorbent cartridges are able to function adequately with only a few theoretical plates. Solute size is identified as the primary driving force for sorbent retention under SPE conditions with polar interactions favoring retention in the aqueous mobile phase and a decrease in the breakthrough volume. All parameters required to predict the optimum sampling conditions, breakthrough volume and recovery in SPE can be conveniently obtained from data generated by HPLC. The sampling characteristics of particle‐loaded membranes are compared to those of conventional sorbent cartridges and differences in operating characteristics which affect the sampling efficiency for both devices are discussed.
Capillary SFC‐FTIR – effects of the flow‐cell on chromatographic resolution
Authors: Jenkins Timothy J. , Kaplan Muammer , Davidson George 
Published: May 2005

AbstractThe quantitative effects on chromatographic resolution of FTIR flow‐cells for detection in capillary SFC have been determined. A suitably designed cell with a volume of 500 nl was shown to cause only modest broadening of chromatographic peaks obtained from the surfactant mixture Triton X‐100, showing that subsequent detection methods can therefore be used in a multi‐hyphenated chromatographic ensemble. A larger‐volume (980 nl) cell was found to give satisfactory results with 100 μ columns, but not with 50 μm columns. The practicability of a multi‐hyphenated system was illustrated by a preliminary capillary SFC‐UV‐FTIR‐FID study on a plant extract. Good infrared spectra were obtained, together with well‐resolved UV and (subsequent) FID chromatograms.
Determination of organic acids and ketones in contaminated soils
Authors: Langbehn Arno , Steinhart Hans 
Published: May 2005

AbstractHydrocarbons and metabolites from biodegradation in soil have been isolated and separated using Soxhlet extraction, with n‐heptane and dichloromethane, combined with solid‐phase extraction on silica gel and basic aluminum oxide using n‐pentane, dichloromethane, methanol, and sulfuric acid – methanol as eluents. This procedure can be used for determination of metabolites both in laboratory‐prepared soil samples containing mineral oils and in actual contaminated soil.After microbiological degradation, organic acids and ketones which were not original components of the diesel fuel and lubricating oil contaminating the soil samples were identified using capillary gas chromatography – mass spectrometry in batch‐soil experiments. Predominantly alicyclic and branched‐chain aliphatic organic acids and diacids, and aromatic ketones, were found to be formed after a few weeks degradation.
System for calculating the linear temperature‐programmed retention indices of polycyclic aromatic compounds
Authors: Shaogang Chu , Xiaobai Xu 
Published: May 2005

AbstractTheoretical procedures have been used to predict linear temperature‐programmed retention indices for polycyclic aromatic compounds. It is possible to calculate such indices for polycyclic aromatic compounds in some practical situations in which the compounds cannot be eluted during a simple linear temperature program. The theory has been tested for a number of polycyclic aromatic hydrocarbon (PAHs) in single‐ and multi‐plateau temperature‐programmed gas chromatography with SE‐52 as the stationary phase. This method will extend the applicability of linear retention indices for the identification of the isomers of polycyclic aromatic compounds.
HPTLC separation of platinum metal 8‐hydroxyquinolinates
Authors: Wenclawiak Bernd W. , Flemming Michael 
Published: May 2005

AbstractHigh performance thin layer chromatography has been used to separate all the platinum metal 8‐hydroxyquinolinates on polar stationary phases. The dependence of Rf values on the composition of mobile phases prepared from chloroform – tetrahydrofuran or chloroform – alcohol mixtures has been investigated. Retention was found to be partially dependent on alcohol chain length in chloroform – alcohol systems. The results obtained from TLC are dependent on the method of sample preparation used for the analyte.
Automated sample cleanup using on‐line coupling of size exclusion chromatography to high resolution gas chromatography
Authors: Blomberg Jan , Schoenmakers Peter J. , van den Hoed Nico 
Published: May 2005

AbstractA fully automated on‐line sample cleanup system based on the coupling of size exclusion chromatography to high resolution gas chromatography is described. The transfer technique employed is based on fully concurrent solvent evaporation using a loop‐type interface, early vapor exit and co‐solvent trapping. Optimization of the LC‐GC transfer was done visually via an all‐glass oven door. To circumvent the problem of mixing within the injection loop, an adaptation was made to the standard loop‐type interface. The determination of a series of additives in a polymer matrix is presented as one example of the vast range of applications opened up by this technique.
Analysis of amines in petroleum
Authors: Thomson Jane S. , Green John B. , McWilliams Ted B. , Yu Shirley K.‐T. 
Published: May 2005

AbstractAn analytical method for differentiation of primary, secondary, and tertiary amines using exhaustive trifluoroacetylation prior to GC/MS has been developed. Using the conditions described in the report, most primary amines add two and secondary amines add one trifluoroacetyl group. In general, tertiary amines do not react. GC retention indices and relative GC/MS total ion current response factors for 102 trifluoroacetyl derivatives are reported. Examples of the application of the method to petroleum and coal liquid products are provided. Because of the limited thermal stability of the derivatives of primary amines, the method is applicable only to distillates boiling below 370 °C (700 °F).
GC–MS analysis of phenolic compounds in fuels after conversion to trifluoroacetate esters
Authors: Green John B. , Yu Shirley K.‐T. , Vrana Robert P. 
Published: May 2005

AbstractThe GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported.The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C0‐, C1‐ and C2‐alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits.In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification.Example applications in analysis of coal‐, shale‐ and petroleum‐derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.
Prediction of programmed temperature retention times on linked capillary columns of different polarity
Authors: Gerbino Tomaso C. , Costello Gianrico 
Published: May 2005

AbstractSystems formed by serial connection of capillary columns of different polarity were studied with methods previously used to predict the behavior of linked capillary columns under isothermal conditions and to obtain programmed temperature gas chromatography (PTGC) retention times of the individual columns starting from isothermal data. The two calculation methods were simultaneously applied in order to predict PTGC retention times of the series system starting from isothermal data obtained on the two individual columns. Experimental retention values measured using different temperature programs on the individual columns and on the series systems were found to agree with those calculated.
Limonene concentration in lemon (Citrus volkameriana) peel oil as a function of ripeness
Authors: Combariza Marianny Yajaira , Tirado Cristian Blanco , Stashenko Elena , Shibamoto Takayuki 
Published: May 2005

AbstractThe dependence of the limonene content of lemon (Citrus volkameriana) peel oil on the degree of ripeness of the fruit has been studied by using steam distillation and cold pressing to extract the oils from lemon fruit peel at different stages of maturation (green, greenish‐yellow, and yellow‐orange peel coloration). Samples of essential oils were analyzed by high resolution GC and GC‐MS, using tetradecane as internal standard for quantitation. Forty components were detected; thirty eight were positively identified by comparison of their mass spectra (El, 70 eV) and Kováts retention indexes (determined using a non‐logarithmic scale on capillary columns coated with both polar (DB‐Wax) and non‐polar (DB‐1) stationary phases) with those of standards and with data reported in the literature. The limonene concentration reached a maximum level of 79.4% when the fruit was in the intermediate maturation stage characterized by greenish‐yellow coloration.
Determination of iphosphamide and seven metabolites in blood plasma, as stable trifluoroacetyl derivatives, by electron capture chemical ionization GC‐MS
Authors: Momerency Guido , Van Cauwenberghe Karel , De Bruijn Ernst A. , Van Oosterom Allan T. , Highley Martin S. , Harper Peter G. 
Published: May 2005

AbstractA method is described for the determination of the antitumor agent iphosphamide and seven of its metabolites in the plasma of cancer patients by multiple ion monitoring (MIM) GC‐MS, mainly using the electron capture chemical ionization mode, of stable methyl and/or trifluoroacetyl derivatives. The metabolites determined were 2‐ and 3‐dechloroethyliphosphamide, 4‐ketoiphosphamide, carboxyiphosphamide, iphosphamide mustard, and two previously undetected metabolites, chloroethylamine and 1,3‐oxazolidine‐2‐one.The isolation of the acidic and neutral metabolites was performed by solid phase extraction on to C18 adsorbent at pH 4. The weakly acidic iphosphamide mustard, isolated under these conditions with a yield of ca 50%, was measured as a stable methyltrifluoroacetyl derivative, in contrast to the corresponding phosphoramide mustard of the isomer cyclophosphamide which decomposes during derivatization. Chloroethylamine and 1,3‐oxazolidine‐2‐one were isolated with high yield by liquid extraction with ethyl acetate at pH 10.Selective measurement of several metabolite derivatives with similar retention times was performed by multiple ion monitoring MS of specific ion masses, using a methyl phenyl siloxane capillary column previously employed in the study of cyclophosphamide metabolites. Quantitation of metabolites in patient plasma samples could be performed in the concentration range 3 ng to 20 μg per ml of original plasma.