Home About us Contact
|
Home About us Contact | ||
|
|
||
Gas Chromatographic (gas + chromatographic)
Terms modified by Gas Chromatographic Selected AbstractsGas chromatographic,mass spectrometric urinary metabolome analysis to study mutations of inborn errors of metabolismMASS SPECTROMETRY REVIEWS, Issue 6 2005Tomiko Kuhara Abstract Urine contains numerous metabolites, and can provide evidence for the screening or molecular diagnosis of many inborn errors of metabolism (IEMs). The metabolomic analysis of urine by the combined use of urease pretreatment, stable-isotope dilution, and capillary gas chromatography/mass spectrometry offers reliable and quantitative data for the simultaneous screening or molecular diagnosis of more than 130 IEMs. Those IEMs include hyperammonemias and lactic acidemias, and the IEMs of amino acids, pyrimidines, purines, carbohydrates, and others including primary hyperoxalurias, hereditary fructose intolerance, propionic acidemia, and methylmalonic acidemia. Metabolite analysis is comprehensive for mutant genotypes. Enzyme dysfunction,either by the abnormal structure of an enzyme/apoenzyme, the reduced quantity of a normal enzyme/apoenzyme, or the lack of a coenzyme,is involved. Enzyme dysfunction,either by an abnormal regulatory gene, abnormal sub-cellular localization, or by abnormal post-transcriptional or post-translational modification,is included. Mutations,either known or unknown, common or uncommon,are involved. If the urine metabolome approach can accurately observe quantitative abnormality for hundreds of metabolites, reflecting 100 different disease-causing reactions in a body, then it is possible to simultaneously detect different mutant genotypes of far more than tens of thousands. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:814,827, 2005 [source] Nursery pollination by a moth in Silene latifolia: the role of odours in eliciting antennal and behavioural responsesNEW PHYTOLOGIST, Issue 4 2006S. Dötterl Summary ,,Since the 1970s it has been known that the nursery pollinator Hadena bicruris is attracted to the flowers of its most important host plant, Silene latifolia, by their scent. Here we identified important compounds for attraction of this noctuid moth. ,,Gas chromatographic and electroantennographic methods were used to detect compounds eliciting signals in the antennae of the moth. Electrophysiologically active compounds were tested in wind-tunnel bioassays to foraging naïve moths, and the attractivity of these compounds was compared with that to the natural scent of whole S. latifolia flowers. ,,The antennae of moths detected substances of several classes. Phenylacetaldehyde elicited the strongest signals in the antennae, but lilac aldehydes were the most attractive compounds in wind-tunnel bioassays and attracted 90% of the moths tested, as did the scent of single flowers. ,,Our results show that the most common and abundant floral scent compounds in S. latifolia, lilac aldehydes, attracted most of the moths tested, indicating a specific adaptation of H. bicruris to its host plant. [source] Ultra-trace analysis of multiple endocrine-disrupting chemicals in municipal and bleached kraft mill effluents using gas chromatography,high-resolution mass spectrometryENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2008Michael G. Ikonomou Abstract A comprehensive gas chromatographic,high-resolution mass spectrometric (GC-HRMS),based method was developed that permitted the simultaneous determination of 30 estrogenic endocrine-disrupting chemicals (EDCs) and related compounds, including surfactants, biogenic and synthetic steroids, fecal sterols, phytoestrogens, and plasticizers, in wastewater. Features of the method include low sample volume (,40 ml), optimized Florisil® cleanup to minimize matrix interferences and optimized analyte derivatization to improve sensitivity via GC-HRMS. Detection limits were in the low- to mid-ng/L range, and recoveries were greater than 60% for most target analytes. This new method allows for high throughput analysis of many organic wastewater contaminants in a complex matrix with relative standard deviation of less than 15% for most measurable compounds. The applicability of the method was demonstrated by examining wastewater samples from different origins. Compounds such as di(2-ethylhex-yl)phthalate, cholesterol, cholestanol, and other cholesterol derivatives were measured in much higher concentrations in untreated sewage and were reduced substantially in concentration by the treatment process. However, steroidal compounds, particularly estrone (E1), 17,-estradiol (E2), and estriol (E3), as well as plant sterols (except stigmastanol), were greater in the treated municipal wastewater versus the untreated effluent. Plant and fungi sterols, stigmastanol and ergosterol, were found largely associated with bleached kraft mill effluent (BKME) as compared to the municipal effluents. [source] Comparative study on the antimicrobial activities of different sandalwood essential oils of various originFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2006Leopold Jirovetz Abstract In total, eight samples of different sandalwoods [Amyris balsamifera L., Santalum album L. and Santalum spicatum (R.Br.) A.DC.] and a mixture of , - and , -santalols, as well as eugenol as reference compound, were tested by an agar dilution and agar diffusion method for their antimicrobial activities against the yeast Candida albicans, the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. The main compounds of each essential oil were investigated by gas chromatographic,spectroscopic (GC-FID and GC,MS) and ,olfactory methods to obtain information about the inßuence of these volatiles on the observed antimicrobial effects. For the santalol mixture, as well as for one S. album and one S. spicatum sample with moderate concentrations of santalols, antimicrobial activity was found against all the strains used. The A. balsamifera sample, containing only a small quantity of , -santalol and nearly no , -santalol, showed high effects only against Klebsiella pneumoniae, while against the other strains weak or no activity was observed. Therefore, santalols in medium and/or high concentrations in sandalwood oils show a significant inßuence on antimicrobial potential in such natural products. Copyright © 2006 John Wiley & Sons, Ltd. [source] Chemical composition and olfactory characterization of essential oils of fruits and seeds of African pear (Dacryodes edulis (G. Don) H. J. Lam) from CameroonFLAVOUR AND FRAGRANCE JOURNAL, Issue 2 2005Leopold Jirovetz Abstract The composition of the essential oil of Dacryodes edulis (G. Don) H. J. Lam (Burseraceae) fruits and seeds from Cameroon were investigated by gas chromatographic,spectroscopic (GC,FID and GC,MS) and olfactory methods to identify those volatiles responsible for the characteristic aroma of this commonly known African pear. Monoterpenes, such as , -pinene (fruits/seeds: 22.3/21.5%), , -pinene (13.7/19.7%), limonene (7.2/27.5%) and , -phellandrene (10.8/12.1%) were found to be main compounds of these essential oils. A correlation of the identi,ed constituents of the two essential oils of African pear from Cameroon with their single odour impressions is also given. Copyright © 2004 John Wiley & Sons, Ltd. [source] Determination of average carbon number of petroleum waxes by X-ray diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2008Sanat Kumar Eight petroleum waxes, both paraffin as well as microcrystalline, have been analysed by X-ray diffraction. The average carbon number has been estimated by the long-range ordering observed in the diffractograms of these waxes. The average carbon number has also been determined following the standard gas chromatographic (GC) method. The results obtained by X-ray diffractometry compare well with those obtained by the GC method. The former method also permits determination of the average carbon number of high melting point waxes, which is otherwise difficult using GC. [source] Rapid and sensitive determination of morphine in street opium samples by thermal desorption gas chromatography using a microfurnace pyrolyzerJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2004Minemasa Hida Abstract Thermal desorption of the alkaloids in opium samples at 300°C using a vertical microfurnace pyrolyzer was followed by their on-line gas chromatographic (GC) analysis on a large-bore glass capillary column. This method permitted rapid and sensitive determination of the content of the main alkaloid, morphine, in the small (ca. 100 ,g) opium samples with a relative standard deviation within 4% for 5 runs. The observed morphine contents of about 12 to 15 w/w% in the given opium samples were in fairly good agreement with those estimated by a conventional GC-MS method. [source] A portable multi-dimensional gas chromatographic system for field applicationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12-13 2003Jon H. Wahl Abstract We have constructed and tested a multi-dimensional gas chromatographic system that can be utilized for field portable applications. The chromatographic system is capable of one-dimensional separations and multi-dimensional gas chromatographic (MDGC) separations in a single compact package. Three different general multi-dimensional separation approaches are possible: column switching; traditional heart-cutting; and comprehensive analyses. The MDGC system utilizes a simple 10-port valving approach to accomplish these separations to a single point detector. Because of this valving scheme no hardware change is required to switch between the heart-cut and the comprehensive separation modes, only a software methodology change is required. An additional advantage of this valving approach is that 100% of the first-dimensional effluent is sampled to the second dimension for separation. The system is capable of rapid column heating (room temperature to 250°C in approximately 10 s) and rapid column cooling (250°C to room temperature within approximately 30 s). Preliminary results for heart-cut and comprehensive separations that target five compounds against high concentration levels of complex background are illustrated. [source] Glass-Transition Temperature (Tg) of Free-Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 1.MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2002A Study on Tg of Atactic Monodisperse Polystyrenes Abstract The glass-transition temperature (Tg) of several atactic monodisperse polystyrenes (PSt)s was studied by an inverse gas chromatographic (IGC) analysis, as a preliminary study for the detection of the Tg of polyacrylonitrile. The Tg of PSt with different molecular weights was clearly obtained by this method. The agreement in the Tg values obtained by IGC and by differential scanning calorimetry (DSC) was quite good within the molecular-weight range Mp,=,7,600,2,430,000 (where, Mp,=,(Mn,×,Mw)1/2). This method has a wide universality for the detection of the Tg of polymers. Several essential factors were extracted for the establishment of the optimum conditions for IGC measurements, such as the concentration of polymer toward a clay matrix (10 wt.-%), and the type of lower probe, decane. The best probe was determined empirically from the most effective detection in the IGC measurements of PSt. Molecular-weight dependence of the Tg of PSt. Experimental data obtained here are indicated by an arrow. Other data was taken from ref.21 [source] Glass-Transition Temperature (Tg) of Free-Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 2,.MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2002Molecular-Weight Dependence of Tg of Two Different Types of Aqueous Polymers Abstract The molecular-weight dependence of the glass-transition temperature (Tg) of a series of atactic polyacrylonitriles (PAN)s was studied by inverse gas chromatographic (IGC) analysis. PANs having different molecular weights were prepared by either; (i) the addition of isopropyl alcohol as a chain-transfer agent, or (ii) a scission reaction induced by the addition of alkali (NaOH) to a solution (N,N -dimethylformamide solution, at 25,°C) of the resulting polymer. The intrinsic viscosity [,] was in the range of 10.9,0.1 (dl,·,g,1), which corresponds to a viscosity-averaged molecular weight (Mv) of 1,590,000,3,000. As part of the results, a side reaction, which saw the conversion of the nitrile (CN) groups of PAN into amide (CONH2) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular-weight dependence of the Tg in free-radically prepared PAN was discussed in connection with a chain-transfer mechanism in an aqueous medium. Molecular-weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow. [source] Application of automated matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the measurement of enzyme activitiesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2001Min-Jung Kang Sample preparation methods and data acquisition protocols were optimized for the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) to high-throughput quantitative analysis of low molecular mass substrates and products of an enzyme-catalyzed reaction. Using a deuterlum-labeled internal standard, precise standard curves were obtained (r2,=,0.9998) over two orders of magnitude of concentration of rac -1-phenylethylamine (PEA), which is converted to 2-methoxy- N -[(1R)-1-phenylethyl]acetamide (MET) by a lipase-catalyzed reaction with ethylmethoxyacetate (EMA) as second substrate. Reliable relative standard deviations were achieved (,5%) using automated analysis with peak intensity ratios between 0.2 and 5 of analyte to internal standard. This method permitted quantitative analysis of the lipase reaction, producing results comparable to those from gas chromatographic (GC) analysis in the dynamic range of GC. This work shows that MALDI-TOFMS can be applied for the high-throughput screening of enzymes. Copyright © 2001 John Wiley & Sons, Ltd. [source] Optimization of a novel headspace,solid-phase microextraction,gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devicesBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Michael P. DiCicco Abstract Medical devices sterilized by ethylene oxide (EtO) retain trace quantities of EtO residuals, which may irritate patients' tissue. Reliably quantifying trace level EtO residuals in small medical devices requires an extremely sensitive analytical method. In this research, a Doehlert uniform shell design was utilized in obtaining a response surface to optimize a novel headspace,solid-phase microextraction,gas chromatographic (HS-SPME-GC) method developed for analyzing trace levels of EtO residuals in sterilized medical devices, by evaluating sterilized, polymer-coated, drug-eluting cardiovascular stents. The effects of four independent experimental variables (HS-SPME desorption time, extraction temperature, GC inlet temperature and extraction time) on GC peak area response of EtO were investigated simultaneously and the most influential experimental variables determined were extraction temperature and GC inlet temperature, with the fitted model showing no evidence of lack-of-fit. The optimized HS-SPME-GC method demonstrated overall good linearity/linear range, accuracy, repeatability, reproducibility, absolute recovery and high sensitivity. This novel method was successfully applied to analysis of trace levels of EtO residuals in sterilized/aerated cardiovascular stents of various lengths and internal diameter, where, upon heating, trace EtO residuals fully volatilized into HS for extraction, thereby nullifying matrix effects. As an alternative, this novel HS-SPME-GC method can offer higher sensitivity compared with conventional headspace analyzer-based sampling. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of terbinafine hydrochloride in cat hair by two chromatographic methodsBIOMEDICAL CHROMATOGRAPHY, Issue 8 2001Jernej Kuz Terbinafine hydrochloride (terbHCl) concentration on the site of infection with Microsporum canis is a very important indicator of drug effectiveness. Several chromatographic methods exist that can be used for the determination of terbHCl concentration in biological samples. A high performance liquid chromatographic (HPLC) method and a gas chromatographic (GC) method have been compared and critically evaluated for the determination of a terbHCl levels in cat hair. The sensitivity and the linearity of the previously developed HPLC method were 0.25,ng/mL and 0.25,3000,ng/mL, respectively. The limit of quantification (LOQ) was 0.01,µg/g of terbHCl in cat hair, and reproducibility of 96.6% and recovery of 93.8% were achieved using appropriate sample pre-treatment and optimal chromatographic conditions. The sensitivity of the GC method, 25,ng/mL (LOQ 625 ppb), was much lower than that of the HPLC method. The GC method still enables determination of terbHCl in a range of concentrations in cat hair. The reproducibility of terbHCl for the cat hair samples was 95.3% and the recovery was only 70.0%. Both methods can be used for the evaluation of drug effectiveness in cats and both of them require only basic chromatographic equipment that can be found in most analytical laboratories. Copyright © 2001 John Wiley & Sons, Ltd. [source] The pharmacokinetics of ethosuximide enantiomers in the ratBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2001J. Mifsud Abstract A chiral gas chromatographic assay previously developed for quantitative analysis of ethosuximide and its major metabolites in rat urine has been adapted for the analysis of the drug in plasma. Ethosuximide, both as a racemic mixture and as the individual enantiomers, was administered to conscious rats by the intravenous (i.v.) and intraperitoneal (i.p.) routes. Pharmacokinetic parameters were estimated using standard non-compartmental methods. Comparison of the pharmacokinetic parameters of (S)-ethosuximide and (R)-ethosuximide showed that total body clearance of (R)-ethosuximide was significantly larger than that of (S)-ethosuximide and that elimination half-life was significantly shorter following administration of both 40 mg i.v. and i.p. doses, indicating that there is stereoselective elimination of ethosuximide. However, no significant differences were found between apparent volumes of distribution. In addition, no significant differences were found for either enantiomer between the estimates of the pharmacokinetic parameters obtained following administration as the individual enantiomer and as a constituent of the racemic mixture. This indicates that, at the doses studied, the preferential faster elimination of (R)-ethosuximide is not dependent upon the presence of the (S)-enantiomer. Also, for each enantiomer, the lack of any significant difference between estimates of clearance when administered as part of a racemic mixture and when administered separately indicates that neither enantiomer affects the clearance of the other. Copyright © 2001 John Wiley & Sons, Ltd. [source] Use of Volatiles as Indicators of Lipid Oxidation in Muscle FoodsCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 1 2006Carolyn F. Ross ABSTRACT Lipid oxidation has long been recognized as a leading cause of quality deterioration in muscle foods and is often the decisive factor in determining food product storage life. Lipid oxidation generates a number of products, including volatile compounds, which are the major contributors to the development of rancid off-flavors and odors. Over the years, methodologies have been developed to quantify lipid oxidation products in muscle foods. This article reviews the analytical methods that have been used to quantify volatile compounds as indicators of lipid oxidation in muscle foods. The sampling methodologies of distillation/solvent extraction and headspace analysis, and isolation methods associated with gas chromatographic (GC) and high-performance liquid chromatography (HPLC) analyses are discussed. Within gas chromatographic methodologies, headspace (HS) sampling (static HS, dynamic purge-and-trap HS techniques, and solid-phase microextraction [SPME]) are addressed. [source] | |||||||||||||