bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct coupling of capillary supercritical fluid chromatography with supercritical fluid extraction using modified carbon dioxide
Authors: Daimon Hiroyuki , Hirata Yukio 
Published: May 2005

AbstractCapillary supercritical fluid chromatography has been directly coupled with supercritical fluid extraction using modified carbon dioxide. The mixed fluids were prepared with a single pump on‐line mixing system. The most important step in the SFE‐SFC interface was the elimination of the modifier solvent. This was achieved by use of a coupled trap, 0.1 mm i.d. and 0.53 mm i.d. capillary tubing connected in series, with the collected solutes refocused on the second (0.53 mm i.d.) trap before transfer into the separation column. This enabled complete elimination of various modifier solvents and high efficiency collection of the solutes. The effect of the modifier on trapping efficiency was investigated using methanol, ethanol, dichloromethane, hexane, and toluene at a variety of concentrations. n‐Eicosane was, for example, trapped quantitatively by modified carbon dioxide containing up to 13 % (w/w) methanol. The use of the technique has been demonstrated by selective extraction of n‐paraffins, fatty acid methyl esters, and alcohols from a silica matrix; the effect of different modifiers on the extraction of a mixture of pesticides from soil has also been investigated.
Large volume sample introduction using temperature programmable injectors: Implications of liner diameter
Authors: Mol Hans G. J. , Janssen Hans‐Gerd , Cramers Carel A. , Brinkman Udo A. Th. 
Published: May 2005

AbstractTemperature programmable injectors with liner diameters ranging from 1 to 3.5 mm are evaluated and compared for solvent split injection of large volumes in capillary gas chromatography. The liner dimensions determine whether a large sample volume can be introduced rapidly or has to be introduced in a speed controlled manner. The effect of the injection technique used on the recovery of n‐alkanes is evaluated. Furthermore the influence of the liner diameter on the occurrence of thermal degradation during splitless transfer to the analytical column is studied. Guidelines are given for the selection of the PTV liner internal diameter best suited for specific applications.
Column liquid chromatography coupled on‐line with mass spectrometry using post‐column phosphate suppression
Authors: Debets Alexander J. J. , Mekes Tanja J. L. , Ritburg Andrew , Jacobs Peter L. 
Published: May 2005

AbstractThe coupling of column liquid chromatography on‐line with mass spectrometry using post‐column phosphate suppression is described. A membrane suppressor is used to remove the non‐volatile phosphate ions from the mobile phase after the chromatographic separation prior to introduction into the mass spectrometer. Using post‐column phosphate suppression by a membrane device phosphate concentrations up to 10 mM phosphate, at a mobile phase flow rate of 0.1 ml/min, could be removed for more than 99% without any decay of the sensitivity of the MS detection.Using a new antidepressant tetracyclic basic compound, ORG 4428, and some structure related compounds as model compounds electron impact as well as chemical ionisation spectra of all compounds could be obtained. The set‐up could be used for several weeks running, using a phosphate containing mobile phase, without any loss of performance.
Catalytic transformation of copaiba (Copaifera officinalis) oil over zeolite ZSM‐5
Authors: Stashenko Elena , Wiame Hughes , Dassy Stephane , Martinez Jairo René , Shibamoto Takayuki 
Published: May 2005

AbstractThe oil extracted from the trunk of the copaiba tree (Copaifera officinalis) is composed of sesquiterpenes, C15H24, and a small amount (>7 %) of sesquiterpenols, C15H26O; these were identified from their Kováts indices and mass spectra. The use of zeolites in the catalytic transformation of this renewable source of hydrocarbons is of interest in the search for new chemicals and ecologically clean fuels. Oil samples from copaiba trees growing in Colombia's Oriental Plains were circulated over zeolite ZSM‐5 in a continuous flow fixed‐bed micro reactor at 225, 265, and 325°C, for 1 h and subsequently analyzed by HRGC and GC‐MS. Whereas only thirty four sesquiterpenes were identified in the original oil, over two hundred compounds were found in the product of the treatment of copaiba oil with zeolite ZSM‐5. This complex mixture of sesquiterpenes, light aromatic compounds, and indene and naphthalene derivatives resulted from reactions such as isomerization, hydrogenation, cracking, and dehydrogenation with and without cracking. The amount of cracking products and aromatic compounds increased with reactor temperature but decreased with catalyst aging.
Trace analysis of airborne haloacetates
Authors: Frank Hartmut , Renschen Dirk , Klein Armin , Scholl Harald 
Published: May 2005

AbstractHaloacetates in various environmental compartments can be determined by gas chromatography‐negative‐ion chemical‐ionization mass spectrometry after derivatization with 1‐pentafluorophenyl diazoethane. Detection limits in absolute amounts per injection are between 0.01 fg (chlorodifluoroacetate) and 80 fg (monofluoroacetate). Sampling of haloacetates in urban air was performed by means of cylindrical denuders coated with alkalized glycerol. The haloacetates detected are trifluoro‐, monochloro‐, dichloro‐, trichloro‐, monobromo‐, and dibromoacetate. The concentrations in ambient air fluctuate strongly, e.g. between 20 and 3000 pg/m3 for TFA. Haloacetates are also found in river waters and tree foliage. A major problem is interference from contamination with trifluoro‐ and trichloroacetate.
Analysis of triacylglycerol positional isomers by silver ion high performance liquid chromatography
Authors: Adlof Richard O. 
Published: May 2005

AbstractSilver ion chromatography, utilizing two commercially available HPLC columns connected in series, was used to separate a variety of triacylglycerol positional isomers. The isomers had a fatty acid composition of ABA and AAB, where A and B were fatty acids containing zero to three double bonds. Isocratic solvent systems of 0.5% to 1.0% acetonitrile in hexane were used to separate the triacylglycerol isomers. This methodology can be used to rapidly determine the isomeric purity of synthesized or isolated triacylglycerols and to isolate specific positional isomers.
Comparison of polydimethyl siloxane stationary phases with 5% and 50% phenyl substitution for the separation of organophosphorus and organonitrogen pesticides under optimized gas chromatographic conditions
Authors: Sippola Erkki , David Frank , Sandra Pat 
Published: May 2005

AbstractThe CGC analysis of 25 organophosphorus and organonitrogen pesticides was optimized on two different stationary phases, namely a 5% diphenyl dimethyl silicone (SE‐54 type) and a 50% diphenyl dimethyl silicone (OV‐17 type) by selecting the best temperature program conditions, using computer simulation.
Analysis of amine compounds by capillary gas chromatography using ammonia–helium carrier gas
Authors: Ghaoui Labib , Pell Karen , Chritz Karen , Loomis Robert N. 
Published: May 2005

AbstractThe use of 10%, 1%, and 0.1% ammonia in helium as carrier gas was investigated as a means of improving poor chromatographic peak shape often associated with low level determinations of amine compounds using thin film capillary columns. The 1% ammonia in helium was found suitable for improving the peak shape of sterically unhindered amine compounds, such as urethane and certain aliphatic primary amines, during gas chromatographic analysis on thin film columns. There was a negligible effect on the peak tailing arising on thick film columns. The 0.1% ammonia in helium was suitable, but not as efficient as the 1% ammonia in helium, in eliminating the peak tailing associated with low level analysis of amine compounds. The signal‐to‐noise (S/N) ratio improved from < 1 using helium carrier gas to 20–25 (for certain test amine compounds) using 1% ammonia in carrier gas. The 10% ammonia in helium carrier gas had an effect on the chromatographic performance similar to that of the 1% ammonia in helium, but the baseline level was very high and this mixture was not used in further studies.
Cyclodextrin carbamates as novel chiral stationary phases for capillary gas chromatography
Authors: Takeichi Tsutomu , Toriyama Hisashi , Shimura Shigeru , Takayama Yuzi , Morikawa Masami 
Published: May 2005

AbstractThe following carbamate derivatives of cyclodextrins (CDs) were prepared as novel chiral stationary phases for capillary gas chromatography: hexakis(2,6‐di‐O‐pentyl)‐α‐cyclodextrin hexa(3‐n‐propyl, 3‐isopropyl, and 3‐phenylcarbamate), heptakis‐(2,6‐di‐O‐pentyl)‐β‐cyclodextrin hepta(3‐n‐propyl, 3‐isopropyl, and 3‐phenylcarbamate), and octakis(2,6‐di‐O‐pentyl)‐γ‐cyclodextrin octa(3‐n‐propyl, 3‐isopropyl, and 3‐isopropyl, and 3‐phenylcarbamate). Metal capillary columns coated with these stationary phases resolved many kinds of racemic mixture. In general, they were especially effective towards polar compounds such as free alcohols, amines, and epoxides. The types of sample which were effectively resolved depended on the cavity size of the CD: α‐CD derivatives were specifically effective toward compounds having linear alkyl chains, and β‐CD derivatives toward compounds with phenyl groups. The results indicate that chiral separation with the cyclodextrin carbamates depends on the formation of inclusion complexes and also on the hydrogen‐bonding interactions between the samples and the CD carbamates.
Quantitative analysis of the mono‐ and sesquiterpenoids of douglas‐fir sapwood by solvent extraction and gas chromatography with mass selective detection
Authors: Kimball Bruce A. , Craver Rori K. , Johnston John J. , Nolte Dale L. 
Published: May 2005

AbstractIn order to investigate the relationship between terpenoid content and black bear foraging preference, an analytical method was required to quantify mono‐ and sesquiterpenoids present in Douglas‐fir sapwood. Sapwood samples were scraped from trees, immediately frozen in liquid nitrogen, and then homogenized. A simple extraction requiring no clean‐up step was performed with ethyl acetate. Extracts were analyzed by gas chromatography with mass selective detection versus external standards. The recoveries of 22 terpenoids from fortified controls were approximately 90% with good precision (relative standard deviations of approximately 10%).
An SPE column‐teflon sleeve assembly for in‐line retention during supercritical fluid extraction of analytes from biological matrices
Authors: Maxwell Robert J. , Lightfield Alan R. , Stolker Alida A. M. 
Published: May 2005

AbstractAn in‐line collector assembly designed for use in supercritical fluid extraction (SFE) vessels is described. This assembly enables solutes extracted by supercritical fluids (SF) to be retained in‐line on standard solid phase extraction (SPE) columns. The assembly consists of a standard 1 mL or 3 mL SPE column fitted into a specially fabricated Teflon© sleeve. The SPE column‐Teflon sleeve assembly is inserted into the SFE vessel followed by the sample matrix. This unit forms a leak‐tight seal with the vessel's end‐cap up to pressures of 680 bar. The choice of sorbents used in the in‐line SPE columns is dependent upon the properties of the solute in the supercritical state. After SFE is completed, the SPE column is removed and the solutes are recovered in 1–2 mL of the eluting solvent. No further clean‐up is normally required prior to chromatographic analysis of the analyte. A comparison was made of recoveries by in‐line and off‐line (after SF decompression) techniques for the SFE of three anabolic steroids in fortified chicken liver. The HPLC chromatograms of the steroids from the off‐line SPE columns were too complex for quantitation, because of coeluting artifacts, whereas chromatograms obtained from in‐line SPE columns were free from UV‐absorbing interferences and were easily quantified.
Trace‐level determination of aromatic sulfonates in water by on‐line ion‐pair extraction/ion‐pair chromatography and their behavior in the aquatic environment
Authors: Lange Frank Thomas , Wenz Michael , Brauch Heinz‐Jürgen 
Published: May 2005

AbstractA new HPLC method for the fully automatic determination of aromatic sulfonates in aqueous samples is presented. The analytical procedure consists of an on‐line combination of ion‐pair extraction (IPE) and ion‐pair chromatography (IPC), both using RP‐C18 solid‐phase material and a tetrabutylammonium salt as ion pairing reagent. Experimental details and performance data are given. This method is suited for the trace‐level determination of a wide variety of benzene, naphthalene, anthraquinone and stilbene sulfonates. Detection limits for surface water using a diode‐array detector are in the sub‐ppb range. For naphthalene sulfonates a very good selectivity and minimal detectable limits of 0.02 μg/L or even lower can be achieved. So far, this method has been successfully applied to waste water, river water, bank filtrate, and water from different steps of drinking water production. The fate of several aromatic sulfonates has been studied beginning at the effluents of industrial waste water treatment plants and ending after activated carbon filtration in a water works. Napthalene‐1,5‐disulfonate (NDS, Armstrong acid) and cis‐4,4′‐dinitrostilbene‐2,2′‐disulfonate (DNS) appear in the raw water of the investigated water works and therefore have to be termed as relevant to water works. In contrast to other disulfonates NDS is extremely stable to biodegradation and ozonation and it is even desorbed from a highly loaded activated carbon filter.
Separation and determination of m‐phenoxybenzaldehyde reaction products by capillary gas chromatography
Authors: Husain Sajid , Sarma Ponnapalli Nageswara , Swamy Sankarayya 
Published: May 2005

AbstractA capillary GC method employing an internal standard has been developed and successfully used for quantitative determination both of the raw materials used for the manufacture of m‐phenoxybenzaldehyde and for the components of the reaction mixtures obtained at various stages of the development of the process. A complete analysis can be performed in a single temperature programmed run.
Chromatographic methods for the analysis of crude tall‐oil
Authors: Nogueira José M. F. , Pereira José L. C. , Sandra Pat 
Published: May 2005

AbstractChromatographic methods currently used for isolation, separation, and identification of the components of crude tall‐oil have been reviewed, and their resolution and analytical methodology compared. Sample introduction by cold on‐column, rather than vaporizing, injection provides good reproducibility and operational convenience for capillary GC analysis. Size exclusion chromatography for isolation followed by capillary GC‐MS for identification, gave the best performance for analysis of acidic and dimeric compounds.
On‐Line coupling of supercritical fluid extraction with high performance liquid chromatography
Authors: Ashraf‐Khorassani Mehdi , Barzegar Mohsen , Yamini Yadolah 
Published: May 2005

AbstractSupercritical fluid extraction was coupled directly with high performance liquid chromatograph. The system was evaluated for direct injection of supercritical CO2 and modified supercritical CO2 at high pressure and temperature onto a HPLC system with varying mobile phase compositions and flow rates. Injection of 9 μL supercritical CO2 onto the HPLC using methanol/water mobile phases from 100% methanol to 80% with a flow of 1.0 mL/min did not adversely affect the baseline of UV detector. However at higher percentages of water, CO2 solubility in the mobile phase decreased and caused baseline interferences on the UV detector. At higher HPLC mobile phase flow rates, supercritical CO2 was injected to higher percentages of water without any effect on the UV baseline. Also, increasing the extraction pressure or modifier concentration did not change the results. Separations of polynuclear aromatic hydrocarbons and linear alkenebenzene sulfonate test mixtures were obtained using on‐line SFE/HPLC interfaced system.
Optimized splitless injection of hydroxylated PCBs by pressure pulse programming
Authors: Vincenti Marco , Minero Claudio , Sega Michela , Rovida Costanza 
Published: May 2005

AbstractHydroxylated polychlorobiphenyls (polyhydroxy‐PCBs) are subjected to severe discrimination effect when they are introduced into a capillary gas chromatograph by splitless injection. This effect can be considerably reduced by using a pulsed pressure injection to favor sample transfer and by further programming the eluent gas pressure during the GC run. By multistep gas pressure programming, splitless injection provides analytical performances and chromatograms for (poly)hydroxy‐PCBs closely resembling those obtained by on‐column injection, whose use is generally discouraged with real environmental samples. Among the six model compounds studies, the dihydroxy congeners exhibit the best results.
A simple, inexpensive, rapid, sensitive and solventless technique for the analysis of accelerants in fire debris based on SPME
Authors: Furton Kenneth G. , Bruna Juan , Almirall José R. 
Published: May 2005

AbstractThe current method of choice for the extraction of flammable or combustible liquid resides from fire debris samples is passive headspace concentration using activated charcoal strips (ACS) for adsorption of the liquid residues followed by elution with carbon disulfide or other suitable solvent. Presently, we report a new technique based on headspace solid‐phase microextraction which has been successfully applied to the identification of a wide range of accelerants commonly seen in arson analysis. The SPME technique developed is simple, inexpensive, rapid, and eliminates the use of the highly flammable and toxic solvent carbon disulfide. Results using this SPME method have been directly compared to results obtained via the ACS technique for light, medium, and heavy petroleum distillates as well as gasoline. All of the accelerants studied were accurately identified by the SPME method with equal or greater sensitivity compared to the ACS method.
Application of a thermal desorption cold trap injector to multidimensional GC and GC‐MS
Authors: Nishimura Osamu 
Published: May 2005

AbstractThe Thermal desorption Cold Trap injector (TCT) was used as a part of modified multidimensional GC (MDGC) or MDGC mass spectroscopy (MS) systems. These systems were based on a preparative GC (GC1), an analytical GC (GC2), or GC‐MS and the TCT. The TCT was mounted on the GC2 or GC‐MS. Analysis was carried out as follows: first, the volatile compounds heart‐cut after separation on the GC1 column were adsorbed onto the Porapak Q column out of the GC1 oven. This Porapak Q column was then coupled to the TCT, and the volatile compounds adsorbed on the Porapak Q were thermally desorbed, cold trapped, and injected onto an analytical column in the GC2 or GC‐MS. Repeatability of the retention time (RT) and area % of model samples consisting of citronellol, decanol, and geranyl acetate was examined. Also, the volatile compounds present at very low concentrations in ethanol solution were concentrated on the Porapak Q column. These were injected onto the analytical column by the same method as described above, and the repeatability of the RT and area % on the chromatogram was examined. In the two experiments, the standard deviation of the RT and area % for each compound was about 0.02 and less than 2.85, respectively. A commercial geranium oil was successfully analyzed by this technique. The results indicate that this modified MDGC and MDGC‐MS system are very useful for detection and determination of compounds in complex mixtures.
Capillary GC‐MS investigation of the metabolism and excretion of oxabolone in man
Authors: Barbarulo Maria Vittoria , Buiarelli Francesca , Ciardi Massino , Giarrusso Alberto , Rosati Felice , Cartoni G. P. 
Published: May 2005

AbstractThe metabolism of oxabolone cipionate, 17‐(3‐cyclopentyl‐1‐oxopropoxy)‐4‐hydroxyestr‐4‐en‐3‐one, a synthetic anabolic steroid, was investigated in man, the cumulative urinary excretion and the metabolism of the compounds being studied by GC‐MS in both electron impact and chemical ionization modes. After administration by injection to volunteers, five different metabolities were detected in urine. The metabolites and the parent compound were detected in urine up to a week after administration.
The effect of electroosmotic and hydrodynamic flow profile superposition on band broadening in capillary electrophoresis
Authors: Kutter Jörg , Welsch Thomas 
Published: May 2005

AbstractThe effect of the superposition of electroosmotic flow and pressureinduced hydrodynamic counterflow on efficiency has been investigated for different capillary electrophoretic systems. Results are shown for 50 and 75 μm internal diameter capillaries at several voltage and counterpressure levels. Hydrodynamic counterflows were successfully applied in electrokinetic chromatography in order to delay the entry of a UV‐active pseudostationary phase, tetraphenyl porphyrintetrasulfonate, into the detection zone allowing the separation of neutral nitroaromatics. The separations are based on the weak charge‐transfer interactions between the porphyrin and the analytes.
Retention behavior of aromatic hydrocarbons and dansylamino acids in reversed‐phase liquid chromatography with cation‐exchange‐induced stationary phases
Authors: Takeuchi Toyohide , Miwa Tomoo , Hu Rongzong , Chu Jianhua 
Published: May 2005

AbstractThe retention behavior of aromatic hydrocarbons and dansylamino acids on cation‐exchangers modified with alkylammonium ions has been examined by microcolumn liquid chromatography. Several parameters affected the retention of analytes, involving concentration of the modifier in the mobile phase, its alkyl chain length and mobile phase composition. Stationary phases modified with a reagent having longer alkyl chains achieved better column efficiency.
Effect of ammonia on the response of the electron capture detector (ECD)
Authors: Abdel‐Rehim Mohamed , Kamel Mohamed , Hassan Moustapha 
Published: May 2005

AbstractThe effect of ammonia on the electron capture detector (ECD) response has been investigated. Nitrogen with different ammonia concentrations (5–20%) was used as make‐up gas. Compared to pure nitrogen, the ECD response decreased when the ammonia concentration in the make‐up gas was 5%. However, the response increased when the ammonia concentration was 20%. The response factor of 4‐chlorophenol increased 4 fold when ammonia was 20%. Also, di‐ and tri‐chlorophenols increased by 30–50%. The nitroaromatic compounds responses increased by about 2–3.7 times with 20% ammonia in the make‐up gas. The signal‐to‐noise (S/N) increased when 20% ammonia in nitrogen was used as make‐up gas compared to pure nitrogen. Also, the detector linearity increased by 50% with ammonia.
Identification of pesticide residues in real matrices by combining retention indices and specific multidetection responses
Authors: Bicchi Carlo , D'amato Angela , Binello Arianna 
Published: May 2005

AbstractA previous paper reported the possibility of using the ratio between the responses of two different specific detectors to a single compound (detector response ratio, DRR) as an identification criterion for that compound, in combination with its retention index.This article gives some applications of DRR in the identification of some pesticides in four different fruits (apples, apricots, strawberries, and peaches) in a range varying from 0.02 to 1.3 ppm, by means of their ECD/FPD DRRs. After clean‐up GC analyses were performed on a single column with dual parallel detection; a personal computer system was used for data analysis.