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EPA Science Inventory

A modified method for the derivatization and analysis of acrylamide as 2-bromopropenamide by gas chromatography/electron capture detection was validated in serum and sciatic nerve from rats. he method was accurate and precise over the concentration range of 2240 to 74700 ppm (w/v...


Quantitative detection of trace explosive vapors by programmed temperature desorption gas chromatography-electron capture detector.  


The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples. PMID:25145416

Field, Christopher R; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C; Rose-Pehrsson, Susan L



Part-per-trillion determination of chlorobenzenes in water using dispersive liquid–liquid microextraction combined gas chromatography–electron capture detection  

Microsoft Academic Search

In this study, a simple, rapid and efficient method, dispersive liquid–liquid microextraction (DLLME) combined gas chromatography–electron capture detection (GC–ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5?l chlorobenzene) and disperser solvent (0.50ml acetone) for the formation of cloudy solution in 5.00ml aqueous sample

Reyhaneh Rahnama Kozani; Yaghoub Assadi; Farzaneh Shemirani; Mohammad-Reza Milani Hosseini; Mohammad Reza Jamali



Determination of pentachlorophenol residue in meat and fish by gas chromatography-electron capture detection and gas chromatography-mass spectrometry with accelerated solvent extraction.  


A novel analytical method, using gas chromatography-electron capture detection (GC-ECD) and GC-mass spectrometry detection (MS), was developed for the qualitative and quantitative measurement of pentachlorophenol in meat and fish. The analyte was extracted by methanol-2% trichloroacetic acid (3/1, v/v) with accelerated solvent extraction (ASE). The eluted fraction was evaporated and derivatized with acetic anhydride-pyridine (1/1, v/v) for GC-ECD analysis and GC-MS confirmation. The parameters for extraction pressure, temperature and cycle of ASE, cleanup, derivatization and analysis procedure were optimized. The averaged decision limits and detection capability of the method were in the ranges of 0.25-0.41 and 0.49-1.01 µg/kg in the muscle and liver of swine and bovine and in the muscle of carp and finless eel, respectively. Spiked recoveries from levels of 0.5-2.0 µg/kg were found to be more than 71.1%, with relative standard deviation less than 14.7% in GC-ECD and GC-MS. This rapid and reliable method can be used for the characterization and quantification of residues of pentachlorophenol in animal and fish tissues. PMID:23690067

Zhao, Dongmei



Group-selective enrichment and determination of pyrethroid insecticides in aquaculture seawater via molecularly imprinted solid phase extraction coupled with gas chromatography-electron capture detection.  


Two types of molecularly imprinted polymers (MIPs) for the simultaneous determination of six pyrethroid insecticides have been developed using deltamethrin (D-MIPs) and cypermethrin (C-MIPs) as template molecules. A comparison of the performance of D-MIPs, C-MIPs, and the corresponding non-imprinted polymers (NIPs) were conducted. Stronger group-selective interactions between the C-MIPs and the six pyrethroid insecticides were achieved. The MISPE method based on the C-MIPs displayed higher extraction recoveries (86.4-96.0%) with RSD values ranging from 2.4 to 7.8% for the six pyrethroid insecticides in aquaculture seawater. After the C-MIP cartridge procedure, the limits of detection and quantification for fenvalerate, deltamethrin, cypermethrin, cyfluthrin, and bifenthrin were in the 16.6-37.0 and 55.3-109.1 ng L?¹ ranges, respectively, and 0.68 and 2.26 ?g L?¹ for phenothrin, respectively. The proposed MISPE method coupled with gas chromatography-electron capture detection was successfully used for the determination of the six pyrethroid insecticides in aquaculture seawater. PMID:22265776

Shi, Xizhi; Liu, Jinghua; Sun, Aili; Li, Dexiang; Chen, Jiong



Simultaneous determination of cyanide and carbonyls in cyanogenic plants by gas chromatography-electron capture/photoionization detection.  


A new method to simultaneously detect cyanide and carbonyl compounds arising from cyanogenic glycosides in plants is described. A portable gas chromatograph.housing two detectors using a single carrier gas is employed to measure the carbonyl compounds (photoionization detector) and cyanide as its cyanogen chloride derivative (electron capture detector) from the headspace of a plant sample. This method affords in-field, rapid screening of plants to determine cyanogenicity. Good agreement was seen between this method for cyanide determination and two traditional field cyanide test kits. Detection of both the cyanide and the carbonyl compound(s) allows for confirmation of the presence of cyanogenic glycosides and eliminates the problem of false positives often seen in traditional cyanide test kits. Gas phase limits of detection for cyanide, acetone, butanone, and benzaldehyde were 69, 41, 105, and 0.39 parts per billion by volume (ppbv), respectively, allowing sensitive detection of cyanogenic glycoside breakdown products. The method's utility for screening cyanogenic plants is demonstrated, and it should be useful for screening cyanogenic foodstuffs to determine suitability for consumption. PMID:12475032

Curtis, Abigale J; Grayless, C Charles; Fall, Ray



[Analysis of organochlorine pesticides and pyrethroid pesticides in vegetables by gas chromatography-electron capture detection coupled with solid-phase extraction using multiwalled carbon nanotubes as adsorbent].  


A multi-residue analytical method based on solid-phase extraction (SPE) with multiwalled carbon nanotubes (MWCNTs) as adsorbent was developed. The determination of 6 organochlorine pesticides and 7 pyrethroid pesticides in vegetables (including cucumber, cherry tomato, cabbage, lettuce, purple cabbage, leek, shallot and onion) was carried out by gas chromatography-electron capture detection (GC-ECD). The GC-ECD method used two columns (HP-50 and HP-1) and two ECD detectors. The HP-50 column was used for the analysis and the HP-1 column for validation. The clean-up conditions were optimized. The analytes were extracted by acetonitrile, and the extract was cleaned up by the MWCNTs SPE cartridge. The extract was re-dissolved by hexane, eluted with acetone-hexane (7:3, v/v) from the columns. The recoveries were over 70% for the 11 pesticides in the 13 pesticides. The results indicated that the MWCNTs SPE cartridge was efficient for 8 vegetable samples, because it reduced the contamination of the coloring materials to GC-ECD. The experimental results showed the MWCNTs SPE cartridge can adsorb the coloring materials and the eluant was nearly colorless. PMID:21847981

Zhao, Haixiang; Jia, Yanxia; Ding, Mingyu; Sun, Dajiang; Zhao, Mengbin



Analysis of corky off-flavour compounds at ultra trace level with multidimensional gas chromatography-electron capture detection.  


A robust method for routine quality control of corky off-flavour compounds in wine and cork soak matrices has been established. Based on an automated headspace solid phase microextraction (HS-SPME), the method needs only marginal sample preparation and achieves low (sub-ng L(-1)) trace level detection limits (LODs) for the most relevant off-flavour compounds, such as 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and 2,4,6-tribromoanisole (TBA). Particularly for wine matrix, reliable trace level quantification had only been achieved after applying heart-cutting multidimensional gas chromatography (MDGC). Using a halogen-sensitive electron capture detector (ECD) and quantification with a stable isotope dilution assay (SIDA), LODs of 0.1ng L(-1) for TCA, TeCA and TBA could be obtained. Since a SIDA based quantification method is used with a non-mass spectrometric detector, the necessary chromatographic resolution of internal standard and target analyte peaks resulted from the use of highly deuterated [(2)H(5)]-isotopologues. PMID:23219330

Slabizki, Petra; Schmarr, Hans-Georg



Determination of pyrethroid metabolites in human urine using liquid phase microextraction coupled in-syringe derivatization followed by gas chromatography/electron capture detection.  


Metabolites of synthetic pyrethroids such as cis-3-(2,2-dibromovinyl)-2,2-di-methylcyclo-propane-1-carboxylic acid, cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid), 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-PBA are biomarkers for exposure to phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin, and permethrin. In this study, the pyrethroid metabolites in workers' urine samples were monitored for the first time with a novel sample pretreatment process combining hollow fiber liquid phase microextraction (HF-LPME) and in-syringe derivatization (ISD) followed by gas chromatography-electron capture detector (GC-ECD) analysis. A micro-syringe pre-filled with derivatizing agents and syringe needle connected to an extracting solvent impregnated hollow fiber segment was used as the LPME probe. Pyrethroid metabolites were extracted and enriched simultaneously from urine samples by HF-LPME sampling and acid hydrolysis at 70 °C for 10 min. After sampling, the ISD was performed by mixing the extracting solution and derivatizing agents through plunger movements, followed by GC-ECD analysis. Parameters influencing the HF-LPME efficiency and ISD were investigated and optimized. Under optimum conditions, the method provided enrichment factors of 69.8-154.6, repeatability from 5.0 to 12% (n = 5), and good linearity (R(2) = 0.9980-0.9998) for interested analytes spiked in urine samples. The method detection limits ranged from 1.6 to 17 ng/mL. A comparison was performed between the proposed method and conventional methods. The proposed method was applied to analyze pyrethroid metabolites in the urine samples collected from workers of pesticide formulation plants. The results suggested that the proposed HF-LPME coupled ISD method was a rapid, simple, efficient, and eco-friendly technique in the biomonitoring of metabolites of pyrethroids in workers' urine. PMID:21667061

Lin, Chiu-Hwa; Yan, Cheing-Tong; Kumar, Ponnusamy Vinoth; Li, Hong-Ping; Jen, Jen-Fon



Microwave-assisted headspace controlled temperature liquid-phase microextraction of chlorophenols from aqueous samples for gas chromatography-electron capture detection.  


A modified headspace liquid-phase microextraction (HS-LPME) method was studied for the extraction of chlorophenols (CPs) from aqueous samples with complicated matrices, before gas chromatographic (GC) analysis with electron capture detection (ECD). Microwave heating was applied to accelerate the evaporation of CPs into the headspace, and an external-cooling system was used to control the sampling temperature. Conditions influencing extraction efficiency, such as the LPME-solvent, the sampling position of LPME, the sampling temperature, microwave power, and irradiation time (the same as sampling time), sample pH, and salt addition were thoroughly optimized. Experimental results indicated that the extraction of CPs from a 10mL aquatic sample (pH 1.0) was achieved with the best efficiency through the use of 1-octanol as solvent, microwave irradiation of 167W, and sampling at 45 degrees C for 10min. The detections were linear in the concentration of 5.0-100microg/L for 2,4-dichlorophenol (2,4-DCP), and 0.5-10microg/L for 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP). Detection limits were found to be 0.7, 0.04, 0.07, and 0.08microg/L for 2,4-DCP, 2,4,6-TCP, 2,3,4,6-TeCP, and PCP, respectively. A landfill leachate sample was analyzed with recovery between 83 and 102%. The present method was proven to serve as a simple, sensitive, and rapid procedure for CP analysis in an aqueous sample. PMID:18760797

Shi, Yi-An; Chen, Ming-Zen; Muniraj, Sarangapani; Jen, Jen-Fon



Use of green coating (cork) in solid-phase microextraction for the determination of organochlorine pesticides in water by gas chromatography-electron capture detection.  


A novel method for the determination of organochlorine pesticides in water samples with extraction using cork fiber and analysis by gas chromatography with electron capture detector was developed. Also, the procedure to extract these pesticides with DVB/Car/PDMS fiber was optimized. The optimization of the variables involved in the extraction of organochlorine pesticides using the aforementioned fibers was carried out by multivariate design. The optimum extraction conditions were sample temperature 75°C, extraction time 60min and sodium chloride concentration 10% for the cork fiber and sample temperature 50°C and extraction time 60min (without salt) for the DVB/Car/PDMS fiber. The quantification limits for the two fibers varied between 1.0 and 10.0ngL(-1). The linear correlation coefficients were >0.98 for both fibers. The method applied with the use of the cork fiber provided recovery values between 60.3 and 112.7 and RSD?25.5 (n=3). The extraction efficiency values for the cork and DVB/Car/PDMS fibers were similar. The results show that cork is a promising alternative as a coating for SPME. PMID:25618687

Neves Dias, Adriana; Simão, Vanessa; Merib, Josias; Carasek, Eduardo



Simultaneous analysis of polychlorinated biphenyls and organochlorine pesticides in seawater samples by membrane-assisted solvent extraction combined with gas chromatography-electron capture detector and gas chromatography-tandem mass spectrometry.  


A highly efficient and environment-friendly membrane-assisted solvent extraction system combined with gas chromatography-electron capture detector was applied in the simultaneous determination of 17 polychlorinated biphenyls and organochlorine pesticides in seawater samples. Variables affecting extraction efficiency, including extraction solvent used, stirring rate, extraction time, and temperature, were optimized extensively. Under optimal extraction conditions, recoveries between 76.9% and 104.6% in seawater samples were achieved, and relative standard deviation values below 10% were obtained. The limit of detection (signal-to-noise ratio=3) and limit of quantification (signal-to-noise ratio=10) of 17 polychlorinated biphenyls and organochlorine pesticides in seawater ranged from 0.14ngL(-1) to 0.36ngL(-1) and 0.46ngL(-1) to 1.19ngL(-1), respectively. Matrix effects on extraction efficiency were evaluated by comparing with the results obtained using tap water. The extraction effect of developed membrane-assisted solvent extraction method was further demonstrated by gas chromatography-tandem mass spectrometry which can provide structural information of the analytes for more accurate identification, and results identical to those produced by gas chromatography-electron capture detector were obtained. These findings demonstrate the applicability of the developed membrane-assisted solvent extraction determination method for coupling to gas chromatography-electron capture detector or tandem mass spectrometry for determining polychlorinated biphenyls and organochlorine pesticides in seawater samples. PMID:25310709

Shi, Xizhi; Tang, Zigang; Sun, Aili; Zhou, Lei; Zhao, Jian; Li, Dexiang; Chen, Jiong; Pan, Daodong



Polymer-functionalized single-walled carbon nanotubes as a novel sol-gel solid-phase micro-extraction coated fiber for determination of poly-brominated diphenyl ethers in water samples with gas chromatography-electron capture detection.  


Single-walled carbon nanotubes (SWNTs) were functionalized with a hydroxyl-terminated silicone oil (TSO-OH). It is synthesized by the reactions of carbonyl chloride groups on the surface of SWNTs and hydroxyl groups of silicone oil (TSO-OH). The functionalized product SWNTs-TSO-OH was first used as precursor and selective stationary phase to prepare the sol-gel derived poly(SWNTs-TSO-OH) solid-phase microextraction (SPME) fiber for determination of polybrominated diphenyl ethers (PBDEs) in water samples. The possible major reaction of the sol-gel coating process was discussed and confirmed by IR spectra, Raman spectroscopy, and scanning electron microscopy. Some parameters of SPME fiber for the determination of PBDEs were investigated by headspace SPME/gas chromatography with electron-capture detection (HS-SPME/GC-ECD). Compared with the commercial SPME fiber, the new coated fiber showed higher extraction efficiency to PBDEs, better thermal stability (over 340 degrees C), and longer life span (over 200 times). All of these advantages are mainly due to the incorporation of SWNTs, which enhanced the pi-pi interaction with PBDEs and increased the surface area of extraction in contact with the sample. Moreover, the sol-gel coating technology additionally provided the porous structure of the 3-D silica network and the strong chemical binding provided which also will improve the extraction efficiency. Under optimized conditions, the method detection limits for seven PBDEs were 0.08-0.8 ng/L (S/N = 3) and the precision (RSD, n = 5) was 2.2-7.5% at the 50 ng/L level. The linearity of the developed method is in the range of 5-500 ng/L with coefficients of correlation greater than 0.995. The developed method was successfully applied for the analysis of trace PBDEs in reservoir water and wastewater samples. The recoveries obtained at spiking 50 ng/L were between 74% and 109% (n = 5) for PBDEs in water samples. PMID:19364140

Zhang, Weiya; Sun, Yin; Wu, Caiying; Xing, Jun; Li, Jianying



Suitability of magnetic particle immunoassay for the analysis of PBDEs in Hawaiian freshwater fish and crabs in comparison with gas chromatography/electron capture detection-ion trap mass spectrometry  

Technology Transfer Automated Retrieval System (TEKTRAN)

A gas chromatograph/electron capture detector-ion trap mass spectrometer (GC/ECD-ITMS) was used for the determination of polybrominated diphenyl ethers (PBDEs) in freshwater fish and crabs. The samples were also analyzed with an enzyme-linked immunosorbent assay (ELISA). GC/ECD-ITMS results showed...


Comparison and analysis of organochlorine pesticides and hexabromobiphenyls in environmental samples by gas chromatography-electron capture detector and gas chromatography-mass spectrometry.  


Two analytical methods, gas chromatography-electron capture detector (GC-ECD) and gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS), were evaluated and compared for the measurement of persistent organic pollutants, specifically for 26 organochlorine pesticides and two hexabromobiphenyls, in atmospheric particulate matter and soil samples. The hypothesis tested was that the coelution of non-target compounds may lead to false positives when analyzed by GC-ECD, and that the overestimation associated with these false positives can be eliminated using GC-NCI-MS. The study showed that both methods had satisfactory linearity and reproducibility for the target compounds. Although the sensitivities of GC-ECD for most of the compounds investigated were higher than those observed with the GC-NCI-MS method, the matrices interference was obvious with GC-ECD. There was indeed an apparently high false-positive rate or overestimate when GC-ECD was used for environmental samples, implying that the GC-ECD method has been used with care and that GC-NCI-MS is generally superior for the analysis of trace amounts of these compounds in environmental samples. Based on these results, the sample extraction and cleanup procedures of the GC-NCI-MS method were optimized for achieving acceptable recoveries and less matrices interference. PMID:24872522

Liu, Yu; Fu, Xiaofang; Tao, Shu; Liu, Liang; Li, Wei; Meng, Bingjun



Analysis of C(14)-C(17) Polychloro-n-alkanes in Environmental Matrixes by Accelerated Solvent Extraction-High-Resolution Gas Chromatography/Electron Capture Negative Ion High-Resolution Mass Spectrometry.  


A method for quantifying medium-chain (C(14)-C(17)) polychloroalkanes (mPCAs) in environmental matrixes by accelerated solvent extraction high-resolution gas chromatography/electron capture negative ion high-resolution mass spectrometry in the selected ion monitoring mode is presented. The formula group abundance profiles of industrial mPCA mixtures, which are used as standards, and of samples are first determined by monitoring [M - Cl](-) ions of specific m/z values corresponding to the molecular formulas present and by correcting the integrated ion signals for the fractional abundance of the specific m/z value monitored and the number of chlorine atoms in the formula group. mPCA concentrations in environmental samples are then determined by comparing the response of a specific m/z peak in the sample to that in the standard. Extraction recoveries of mPCAs from spiked fish and sodium sulfate (in place of sediment) were >79%. Method detection limits were 13 ng/g for fish and 1.4 ng/?L for sediment, while the analytical detection limit was ?200 pg, at a signal-to-noise ratio of 4:1. By this method, mPCAs were detected in biota and sediment from the mouth of the Detroit River (MI) and ranged from 70 to 900 ng/g. The simultaneous quantitation of C(10)-C(13) (sPCAs) and C(14)-C(17) PCAs, based on monitoring two specific m/z peaks, one characteristic of sPCAs and the other of mPCAs, is also demonstrated. PMID:21662834

Tomy, G T; Stern, G A



Determination of the enantiomer fraction of PBB 149 by gas chromatography/electron capture negative ionization tandem mass spectrometry in the selected reaction monitoring mode.  


Enantioselective determination of the atropisomers of 2,2',3,4',5',6-hexabromobiphenyl (PBB 149) in a purified sample from a bird egg was attempted in this work. By application of the classic method for PBB determination, i.e. gas chromatography coupled to electron capture negative ionization mass spectrometry (GC/ECNI-MS) using the bromide ions, the enantiomers interfered with another brominated compound. Subsequent measurements clarified that this interference did not occur in the mass chromatogram of the molecular ion of PBB 149. Therefore, a GC/ECNI tandem mass spectrometry (MS/MS) method was developed, based on the fragmentation of [M]-. A suitable precursor-product ion transition was found for m/z 627.5 --> 80 +/- 1.5, representing the most abundant ion trace of the molecular ion and the bromide ions. Optimization of the ion source temperature, the methane gas pressure, and the collision voltages resulted in a robust method that could solve the problem. Subsequent injections of a technical PBB product (Firemaster BP-6) resulted in the anticipated racemic proportion (enantiomer fraction (EF) = 0.50 +/- 0.02 (n = 8)). By contrast, the EF in the purified extract of a bird egg was found to be 0.42 +/- 0.02 (n = 10), indicative of a significant enantioenrichment of the second eluting atropisomer. Additional measurements were performed on a non-chiral column. These measurements allowed for the detection of 16 hexabromobiphenyls (hexa-BBs) in Firemaster BP-6. These comparisons verified that PBB 149 enantiomers did not interfere with an isomer that could falsify the enantiomer fraction in the sample. The novel method using GC/ECNI-MS/MS in the selected reaction monitoring (SRM) mode was eight times more sensitive than application of conventional GC/ECNI-MS selected ion monitoring (SIM) analysis of the molecular ion. PMID:16302204

von der Recke, Roland; Mariussen, Espen; Berger, Urs; Götsch, Arntraut; Herzke, Dorte; Vetter, Walter



The determination of PCBs in Rocky Flats Type IV waste sludge by gas chromatography/electron capture detection. Part 2  

SciTech Connect

Before disposal, radioactive sludge (Type IV) from Rocky Flats Plant (RFP) must be evaluated for polychlorinated biphenyl (PCB) content. The Type IV sludge consists of organic solvents, degreasers, cutting oils, and transuranic (TRU) waste mixed with calcium silicate (MicroCel E{reg_sign} and Oil Dri{reg_sign} to form a grease or paste-like material. For laboratory testing, a nonradioactive simulated Type 17V RFP sludge was prepared at Argonne National Laboratory-East (ANL-E). This sludge has a composition similar to that expected from field samples. In an earlier effort, a simplified method was developed for extraction, cleanup of extract, and determination of PCBs in samples of simulated sludge spiked with Aroclors 1254 and 1260. The simplified method has now been used to determine the presence and quantities of other Aroclors in the simulated sludge, namely, Aroclors 10 1 6, 1221, 1232, 1242, and 1248. The accuracy and precision of the data for these Aroclors were found to be similar to the data for sludges spiked with Aroclors 1254 and 1260. Since actual sludges may vary in composition, the method was also verified by analyzing another source of Type IV simulated sludge, prepared by Argonne National Laboratory-West (ANL-W).

Parish, K.J.; Applegate, D.V.; Postlethwait, P.D.; Boparai, A.S.; Reedy, G.T.



Determination of PCBs in Rocky Flats Type IV waste sludge by gas chromatography/electron capture detection  

SciTech Connect

Type IV Rocky Flats Plant (RFP) radioactive sludge samples must be evaluated for polychlorinated biphenyl (PCB) content before disposal. The Type IV sludge consists of organic solvents, degreasers, cutting oils, and transuranic (TRU) waste mixed with calcium silicate (MicroCel E{reg_sign}) and Oil Dri{reg_sign} to form a grease or paste-like material. For laboratory studies a nonradioactive simulated Type IV RFP sludge was prepared having a composition similar to that expected from field samples. A simplified method was developed for extraction, purification and analysis of PCBs using samples of simulated sludge spiked with Aroclors 1254 and 1260 (reports provided to Argonne indicated Aroclors 1254 and 1260 as the most likely PCB contaminants in RFP sludge samples). The developed method was compared to the Environmental Protection Agency (EPA) accepted SW-846 method for analysis of PCBs (Method 8081). The accuracy and precision data were found to be similar for the two methods. The developed method was also tested with samples of simulated sludge spiked with Pu (in solid and solution forms). Reduction of radioactivity in final extract versus in the spike sample ranged from a factor of 10{sup 5} to 10{sup 7}.

Parish, K.J.; Applegate, D.V.; Boparai, A.S.; Reedy, G.T.



Highly selective and sensitive gas chromatography-electron-capture negative-ion mass spectrometry method for the indirect enantioselective identification of 2- and 3-hydroxy fatty acids in food and biological samples.  


A gas chromatographic (GC) method is described for the indirect enantioresolution of 2- and 3-hydroxy fatty acids (OH-FAs). It combines the derivatization of each alkylated enantiomer and the subsequent transfer with (R)-(-)-alpha-methoxy-alpha-trifluoromethylphenylacetyl chloride [(R)-(-)-MTPA-Cl, Mosher's reagent] into a diastereomeric (S)-MTPA derivative. The enantiomers of each derivatized OH-FA were well separated on three non-chiral GC-columns (CP-Sil 2, CP-Sil 8/20% C18 and VF-5ms). The derivatives were detected with high sensitivity by GC with electron-capture detection (GC/ECD) and electron-capture negative-ion mass spectrometry (GC/ECNI-MS) because of their enhanced electron-capturing properties. When applied to sunflower oil spiked with a small amount of a racemic 2-OH-FA, the present method allowed for a highly selective identification without influence from the sample matrix. For more complex samples such as wool wax, GC/ECNI-MS was superior to GC/ECD, since the high sensitivity of this method was linked with high selectivity. Using GC/ECNI-MS in the selected ion monitoring (SIM) mode, 16 enantiopure 2-OH-FAs were detected in a wool wax sample. PMID:17292906

Jenske, Ramona; Vetter, Walter



Novel glycosylation sites localized in Campylobacter jejuni flagellin FlaA by liquid chromatography electron capture dissociation tandem mass spectrometry.  


Glycosylation of flagellin in Campylobacter jejuni is essential for motility and virulence. It is well-known that flagellin from C. jejuni 81-176 is glycosylated by pseudaminic acid and its acetamidino derivative, and that Campylobactor coli VC167 flagellin is glycosylated by legionaminic acid and its derivatives. Recently, it was shown, by use of a metabolomics approach, that C. jejuni 11168 is glycosylated by dimethyl glyceric acid derivatives of pseudaminic acid, but the sites of glycosylation were not confirmed. Here, we apply an online liquid chromatography electron capture dissociation (ECD) tandem mass spectrometry approach to localize sites of glycosylation in flagellin from C. jejuni 11168. Flagellin A is glycosylated by a dimethyl glyceric acid derivative of pseudaminic acid at Ser181, Ser207 and either Thr464 or Thr 465; and by a dimethyl glyceric acid derivative of acetamidino pseudaminic acid at Ser181 and Ser207. For comparison, on-line liquid chromatography collision-induced dissociation of the tryptic digests was performed, but it was not possible to assign sites of glycosylation by that method. PMID:21158479

Zampronio, Cleidiane G; Blackwell, Gemma; Penn, Charles W; Cooper, Helen J



[A case of chloropicrin detection by purge and trap gas chromatography/mass spectrometry].  


Chloropicrin (CP) is an agricultural chemical used as insecticide or fungicide, which occasionally causes accidental poisoning and may used in criminal cases including suicide and homicide. Although CP is usually analyzed using gas chromatography/electron capture detection technique (GC/ECD), further identification by gas chromatography/mass spectrometry (GC/MS) may be required from the view point of forensic chemistry and also clinical toxicology. However, it is very difficult to detect a trace of CP by routine GC/MS. The present paper describes a criminal case, in which GC/MS equipped with curie point purge and trap sampler was successfully applied to detect a small amount of CP. PMID:14582358

Ishizawa, Fujio; Ishiwata, Tetsuya; Miyata, Katsufumi; Yoshida, Tsutomu



Simultaneous determination of insecticide fipronil and its metabolites in maize and soil by gas chromatography with electron capture detection.  


An integrated method for the simultaneous determination of insecticide fipronil and its three metabolites, desulfinyl, sulfide, and sulfone, in maize grain, maize stem, and soil was developed. This three-step method uses liquid-solid extraction with ultrasound or mechanical grinding, followed by liquid-liquid partitioning and florisil solid-phase extraction (SPE) for cleanup. The quantification was conducted by gas chromatography-electron capture detection in triplicate for each sample. The method was validated with five replicates at three fortification concentrations, 0.002, 0.01, and 0.1 mg kg(-1), in each matrix and gave mean recoveries from 83 to 106 % with relative standard deviation ? 8.9 %. The limits of quantification (LOQ) were 0.002 mg kg(-1) for the compounds in all matrixes. In the field study in Beijing and Shandong 2012, fipronil-coated maize seeds were planted and the proposed method was applied for checking the possible existence of four compounds in maize and soil samples, but none of them contained residues higher than the LOQs in both application rates. Moreover, the dissipation of fipronil in soil fits first-order kinetics with half-lives 9.90 and 10.34 days in Beijing and Shandong, respectively. Combined with an adequate sample treatment, this technique offers good sensitivity and selectivity in the three complex matrixes. The results could provide guidance for the further research on pesticide distribution and safe use of fipronil as seed coat in cereals. PMID:24338055

Wang, Tielong; Hu, Jiye; Liu, Chaolun



Rapid determination of the isomeric truxillines in illicit cocaine via capillary gas chromatography/flame ionization detection and their use and implication in the determination of cocaine origin and trafficking routes.  


The isomeric truxillines are a group of minor alkaloids present in all illicit cocaine samples. The relative amount of truxillines in cocaine is indicative of the variety of coca used for cocaine processing, and thus, is useful in source determination. Previously, the determination of isomeric truxillines in cocaine was performed with a gas chromatography/electron capture detection method. However, due to the tedious sample preparation as well as the expense and maintenance required of electron capture detectors, the protocol was converted to a gas chromatography/flame-ionization detection method. Ten truxilline isomers (alpha-, beta-, delta-, epsilon-, gamma-, omega, zeta-, peri-, neo-, and epi-) were quantified relative to a structurally related internal standard, 4',4?-dimethyl-?-truxillic acid dimethyl ester. The method was shown to have a linear response from 0.001 to 1.00 mg/mL and a lower detection limit of 0.001 mg/mL. In this method, the truxillines are directly reduced with lithium aluminum hydride and then acylated with heptafluorobutyric anhydride prior to analysis. The analysis of more than 100 cocaine hydrochloride samples is presented and compared to data obtained by the previous methodology. Authentic cocaine samples obtained from the source countries of Colombia, Bolivia, and Peru were also analyzed, and comparative data on more than 23,000 samples analyzed over the past 10 years with the previous methodology is presented. PMID:25219521

Mallette, Jennifer R; Casale, John F



Gas Flow Detection System  

NASA Technical Reports Server (NTRS)

This system provides a portable means to detect gas flow through a thin-walled tube without breaking into the tubing system. The flow detection system was specifically designed to detect flow through two parallel branches of a manifold with only one inlet and outlet, and is a means for verifying a space shuttle program requirement that saves time and reduces the risk of flight hardware damage compared to the current means of requirement verification. The prototype Purge Vent and Drain Window Cavity Conditioning System (PVD WCCS) Flow Detection System consists of a heater and a temperature-sensing thermistor attached to a piece of Velcro to be attached to each branch of a WCCS manifold for the duration of the requirement verification test. The heaters and thermistors are connected to a shielded cable and then to an electronics enclosure, which contains the power supplies, relays, and circuit board to provide power, signal conditioning, and control. The electronics enclosure is then connected to a commercial data acquisition box to provide analog to digital conversion as well as digital control. This data acquisition box is then connected to a commercial laptop running a custom application created using National Instruments LabVIEW. The operation of the PVD WCCS Flow Detection System consists of first attaching a heater/thermistor assembly to each of the two branches of one manifold while there is no flow through the manifold. Next, the software application running on the laptop is used to turn on the heaters and to monitor the manifold branch temperatures. When the system has reached thermal equilibrium, the software application s graphical user interface (GUI) will indicate that the branch temperatures are stable. The operator can then physically open the flow control valve to initiate the test flow of gaseous nitrogen (GN2) through the manifold. Next, the software user interface will be monitored for stable temperature indications when the system is again at thermal equilibrium with the test flow of GN2. The temperature drop of each branch from its "no flow" stable temperature peak to its stable "with flow" temperature will allow the operator to determine whether a minimum level of flow exists. An alternative operation has the operator turning on the software only long enough to record the ambient temperature of the tubing before turning on the heaters and initiating GN2 flow. The stable temperature of the heated tubing with GN2 flow is then compared with the ambient tubing temperature to determine if flow is present in each branch. To help quantify the level of flow in the manifolds, each branch will be bench calibrated to establish its thermal properties using the flow detection system and different flow rates. These calibration values can then be incorporated into the software application to provide more detailed flow rate information.

Moss, Thomas; Ihlefeld, Curtis; Slack, Barry



Fission gas detection system  


A device for collecting fission gas released by a failed fuel rod which device uses a filter to pass coolant but which filter blocks fission gas bubbles which cannot pass through the filter due to the surface tension of the bubble.

Colburn, Richard P. (Pasco, WA)



46 CFR 154.1345 - Gas detection.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Gas detection. 154.1345 Section...VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment...Instrumentation § 154.1345 Gas detection. (a) Each vessel carrying...have: (1) A fixed flammable gas detection system that...



Photodegradation and stability of chlorothalonil in water studied by solid-phase disk extraction, followed by gas chromatographic techniques.  


Photodegradation of chlorothalonil was studied in deionized and ground water with sunlight and Suntest apparatus, with and without FeCl3/H2O2 and TiO2/H2O2. After irradiation of the water samples spiked at 28-100 micrograms/l of chlorothalonil, the water solutions were preconcentrated using solid-phase disk extraction with C18 and analyzed by gas chromatography-electron capture and gas chromatography-mass spectrometric detection. The degradation products identified by GC-MS were: trichloro-1,3-dicyanobenzene, dichloro-1,3-dicyanobenzene and chloro-1,3-dicyanobenzene. The degradation kinetics followed a first order reaction and the R.S.D. of rate constants, for n = 3, varied from 2 to 14%. Halflives varied between 0.7 and 101 h. The stability of chlorothalonil on C18 Empore disks was also investigated at 20 degrees C, 4 degrees C and -20 degrees C for periods of up to 3 months. Chlorothalonil was not degraded on C18 Empore disks. PMID:9818395

Peñuela, G A; Barceló, D



LC/ESI-MS/MS detection of FAs by charge reversal derivatization with more than four orders of magnitude improvement in sensitivity[S  

PubMed Central

Quantitative analysis of fatty acids (FAs) is an important area of analytical biochemistry. Ultra high sensitivity FA analysis usually is done with gas chromatography of pentafluorobenzyl esters coupled to an electron-capture detector. With the popularity of electrospray ionization (ESI) mass spectrometers coupled to liquid chromatography, it would be convenient to develop a method for ultra high sensitivity FA detection using this equipment. Although FAs can be analyzed by ESI in negative ion mode, this method is not very sensitive. In this study, we demonstrate a new method of FA analysis based on conversion of the carboxylic acid to an amide bearing a permanent positive charge, N-(4-aminomethylphenyl)pyridinium (AMPP) combined with analysis on a reverse-phase liquid chromatography column coupled to an ESI mass spectrometer operating in positive ion mode. This leads to an ?60,000-fold increase in sensitivity compared with the same method carried out with underivatized FAs. The new method is about 10-fold more sensitive than the existing method of gas chromatography/electron-capture mass spectrometry of FA pentafluorobenzyl esters. Furthermore, significant fragmentation of the precursor ions in the nontag portion improves analytical specificity. We show that a large number of FA molecular species can be analyzed with this method in complex biological samples such as mouse serum. PMID:23945566

Bollinger, James G.; Rohan, Gajendra; Sadilek, Martin; Gelb, Michael H.



Development and Application of an Indirect Competitive Enzyme-Linked Immunosorbent Assay for the Detection of p,p?-DDE in Human Milk and Comparison of the Results against GC-ECD  

PubMed Central

1,1-Dichloro-2,2-bis(p-chlorophenyl) ethylene (p,p?-DDE) is the major metabolite of insecticide 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (p,p?-DDT) and a persistent organic pollutant (POPs) with concerns regarding its bioaccumulation and persistence in the environment and food chain. In the present study, an indirect competitive enzyme-linked immunosorbant assay (ic-ELISA) specific for the detection of p,p?-DDE is described. In hapten synthesis, 2,2?-bis(4-chlorophenyl)ethanol and glutaric anhydride were used as precursor and spacer arm, respectively. The hapten was then conjugated to bovine serum albumin (BSA) as immunogen for mouse immunization and also conjugated to ovalbumin as coating antigen for ELISA. The developed ic-ELISA was used for detecting p,p?-DDE in human milk samples and validated against the results from conventional gas chromatography–electron capture detection (GC-ECD). Coefficients of variation (%CV) of ELISA were 5.7–10.4% for intra-assay and 10.6–19.6% for interassay variations. The Pearson correlation coefficient of p,p?-DDE concentrations between ic-ELISA and GC-ECD was r = 0.766, which was in an acceptable range. The results indicate that the developed assay could be an alternative analytical tool for monitoring p,p?-DDE in lipimic matrices such as human milk. PMID:22122759

Hongsibsong, Surat; Wipasa, Jiraprapa; Pattarawarapan, Mookda; Chantara, Somporn; Stuetz, Wolfgang; Nosten, Francois; Prapamontol, Tippawan



Air Monitoring for Hazardous Gas Detection  

NASA Technical Reports Server (NTRS)

The Hazardous Gas Detection Lab (HGDL) at Kennedy Space Center is involved in the design and development of instrumentation that can detect and quantify various hazardous gases. Traditionally these systems are designed for leak detection of the cryogenic gases used for the propulsion of the Shuttle and other vehicles. Mass spectrometers are the basis of these systems, which provide excellent quantitation, sensitivity, selectivity, response times and detection limits. A Table lists common gases monitored for aerospace applications. The first five gases, hydrogen, helium, nitrogen, oxygen, and argon are historically the focus of the HGDL.

Arkin, C. Richard; Griffin, Timothy P.; Adams, Frederick W.; Naylor, Guy; Haskell, William; Floyd, David; Curley, Charles; Follistein, Duke W.



49 CFR 192.736 - Compressor stations: Gas detection.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Compressor stations: Gas detection. 192.736 Section 192...SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS...Maintenance § 192.736 Compressor stations: Gas detection. (a) Not later than...



Semiconducting polymers for gas detection  

NASA Technical Reports Server (NTRS)

Conjugated polyenes, and polyesters containing phthalocyanine in their backbone, were synthesized. These polymers were characterized by chemical analysis, thermogravimetric analysis, spectral analysis, and X-ray diffraction studies for crystallinity, as well as for their film-forming capability and gas/polymer interactions. Most of the polymers were relatively insensitive to water vapor up to 50 percent relative humidity, but the polyester/phthalocyanine (iron) polymer was relatively insensitive up to 100 percent RH. On the other hand, poly(p-dimethylaminophenylacetylene) was too conductive at 100 percent RH. Of the gases tested, the only ones that gave any evidence of interacting with the polymers were SO2, NOx, HCN and NH3. Poly(imidazole)/thiophene responded to each of these gases at all relative humidities, while the other polymers gave varying response, depending upon the RH. Thus, since most of these gases were electron-accepting, the electron-donating character of poly(imidazole)/thiophene substantiates the concept of electronegativity being the operating principle for interaction effects. Of the six polymers prepared, poly(imidazole)/thiophene first showed a very good response to smoldering cotton, but it later became nonresponsive; presumably due to oxidation effects.

Byrd, N. R.; Sheratte, M. B.



Gas sensitive materials for gas detection and method of making  


A gas sensitive material comprising SnO2 nanocrystals doped with In2O3 and an oxide of a platinum group metal, and a method of making the same. The platinum group metal is preferably Pd, but also may include Pt, Ru, Ir, and combinations thereof. The SnO2 nanocrystals have a specific surface of 7 or greater, preferably about 20 m2/g, and a mean particle size of between about 10 nm and about 100 nm, preferably about 40 nm. A gas detection device made from the gas sensitive material deposited on a substrate, the gas sensitive material configured as a part of a current measuring circuit in communication with a heat source.

Trakhtenberg, Leonid Israilevich; Gerasimov, Genrikh Nikolaevich; Gromov, Vladimir Fedorovich; Rozenberg, Valeriya Isaakovna



Gas sensitive materials for gas detection and methods of making  


A gas sensitive material comprising SnO.sub.2 nanocrystals doped with In.sub.2O.sub.3 and an oxide of a platinum group metal, and a method of making the same. The platinum group metal is preferably Pd, but also may include Pt, Ru, Ir, and combinations thereof. The SnO.sub.2 nanocrystals have a specific surface of 7 or greater, preferably about 20 m2/g, and a mean particle size of between about 10 nm and about 100 nm, preferably about 40 nm. A gas detection device made from the gas sensitive material deposited on a substrate, the gas sensitive material configured as a part of a current measuring circuit in communication with a heat source.

Trakhtenberg, Leonid Israilevich; Gerasimov, Genrikh Nikolaevich; Gromov, Vladimir Fedorovich; Rozenberg, Valeriya Isaakovna



Comparative evaluation of liquid chromatography–mass spectrometry versus gas chromatography–mass spectrometry for the determination of hexabromocyclododecanes and their degradation products in indoor dust  

Microsoft Academic Search

Domestic and office dust samples (n=37) were analyzed for hexabromocyclododecanes (HBCDs) using gas chromatography–electron-capture negative ionization–mass spectrometry (GC–ECNI\\/MS) and liquid chromatography–electrospray tandem mass spectrometry (LC–ESI\\/MS\\/MS). To determine the best method to quantify HBCDs using GC–ECNI\\/MS, BDE 128 was used as internal standard (I.S.) in all samples, while 13C-labeled ?-HBCD was used as I.S. in some samples. Total HBCD concentrations (sum

Mohamed Abou-Elwafa Abdallah; Catalina Ibarra; Hugo Neels; Stuart Harrad; Adrian Covaci



Evolved gas detection of iron oxyhydroxides  

Microsoft Academic Search

A procedure is described for recording evolved gas detection (thermal desorption spectra) of various FeOOH samples up to 400°. Characteristic curves of ?-,?- and?-FeOOH are discussed, based on the crystallographic structure which governs the sites for physisorbed H2O as well as OH groups producing H2O by dehydration. Examinations are also made of the variations of the desorption spectra with the

T. Ishikawa; K. Inouye



Environmental trace gas detection using laser spectroscopy  

NASA Astrophysics Data System (ADS)

This special issue of Applied Physics B - Lasers and Optics attempts to document the current status and trends of environmental trace gas detection through a collection of 32 invited papers motivated in part by the need for and importance of a detailed understanding of our environment. Although numerous traditional optical methods, gas chromatography, and mass spectrometry have served us extremely well in atmospheric and environmental trace gas detection, promising new sensing and precise measurement techniques based on laser spectroscopy have emerged and been successfully used in numerous applications. The concept and timing of this special issue has been stimulated to some extent by recent exciting developments of several novel technologies, such as diode and fiber lasers for the optical communications industry, diode-pumped solid-state lasers, and novel bulk and waveguide infrared nonlinear materials. These can be applied to the ultra-sensitive, highly selective detection and real-time analysis of a large number of trace gas species by means of absorption spectroscopy in the mid-infrared fingerprint region, which contains virtually all the fundamental vibrational modes of molecules. Reduction of cost and complexity makes such spectroscopic sources more universally available and user friendly to both established and new fields that include air quality, atmospheric chemistry, industrial, traffic, and rural emissions, chemical analysis and process control, and medical applications.This issue, consisting of two parts, chronicles some of the most significant and representative current research trends. It is hoped that this issue will inspire new directions to both specialists and newcomers in which to drive this exciting field and envision future applications of environmental sensing.

Tittel, Frank K.



A photoacoustic spectrometer for trace gas detection  

NASA Astrophysics Data System (ADS)

A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO2 laser emission lines (9,2-10,9 ?m: 920-1086 cm-1). The CO2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell Q-factor and cell constant are measured close to 50 and 28 mVcmW-1, respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O_3). The ethylene (C_2H_4) from papaya fruit is also investigated using N2 as carrier gas at a constant flow rate.

Telles, E. M.; Bezerra, E.; Scalabrin, A.



Limits of classical detection for gas  

NASA Astrophysics Data System (ADS)

The L.P.M. effect has to be taken into account in UHE-?-ray Astronomy above 1018 eV; at 1020 eV a ?-induced shower has only twice the electron size of a ?-shower with 10 times lower energy. This reduces considerably the intensity ``observed'' near 1020 eV. The e.m. component in proton induced Giant Air Showers (GAS) will be reduced according to our preliminary approach by a non Monte Carlo simulation) by 24% at 1020 eV at sea level; this implies up to those energies that spectrum measurements have to be corrected, but that the classical detection of the e.m. component is still possible. In the same time, the detection of the muon component is also considered. A realistic situation with a giant array ditributed over 104 Km2 at sea level is analysed: the equilateral triangle of the pine forest ``Landes de Gascogne'' (sides of 150 Km, Hossegor-Nerac-Carcans, centered in the south of Bordeaux).

Capdevielle, J. N.; Attallah, R.



33 CFR 127.1203 - Gas detection.  

Code of Federal Regulations, 2010 CFR

...portable gas detectors, or a fixed gas detector, available in the...Z-1 or Z-2. (c) Each gas detector required by paragraph...leaks, check structures for gas accumulations, and indicate workers' exposure to toxic gases in the area. [CGD...




EPA Science Inventory

A gas chromatography/atomic emission detector (GC/AED) system has been evaluated for its applicability to environmental analysis. Detection limits, elemental response factors, and regression analysis data were determined for 58 semivolatile environmental contaminants. Detection l...


Towards aerial natural gas leak detection system based on TDLAS  

NASA Astrophysics Data System (ADS)

Pipeline leakage is a complex scenario for sensing system due to the traditional high cost, low efficient and labor intensive detection scheme. TDLAS has been widely accepted as industrial trace gas detection method and, thanks to its high accuracy and reasonable size, it has the potential to meet pipeline gas leakage detection requirements if it combines with the aerial platform. Based on literature study, this paper discussed the possibility of applying aerial TDLAS principle in pipeline gas leak detection and the key technical foundation of implementing it. Such system is able to result in a high efficiency and accuracy measurement which will provide sufficient data in time for the pipeline leakage detection.

Liu, Shuyang; Zhou, Tao; Jia, Xiaodong



Gas microchromatograph for detection of gas and/or fire hazard in mining  

NASA Astrophysics Data System (ADS)

The paper presents fire and gas hazards occurring in underground hard coal mines; methods of hazard detection and methods of gas concentration measurement used while monitoring and/or mine rescue operations. Chromatographs applied to measurement of atmosphere in mine underground and construction of the own-design gas chromatograph; functional examination of the microchromatograph and analyses of gas mixtures are discussed.

Mroz, Jerzy; Szczygielska, Malgorzata; Malachowski, M.; Dziuban, Jan




EPA Science Inventory

The purpose of this SOP is to describe the methods used for detection and quantification by gas chromatography electron capture detector (GC/ECD) of pesticides in a variety of matrices, including air, house dust, soil, handwipes, and surface wipes. Other SOP's detail the extract...



EPA Science Inventory

An inhibition enzyme-linked immunosorbent assay (ELISA) was used to determine polychlorinated biphenyls (PCBs) in house dust and soil. Soil and house dust samples were analyzed for PCB by both gas chromatography/electron capture detection (GC/ECD) and ELISA methods. A correlati...


46 CFR 154.1350 - Flammable gas detection system.  

Code of Federal Regulations, 2010 CFR alarms, that indicate that one of the alarm conditions under...detection system must have at least one connection for injecting zero gas and span gas into the system...detection system must have at least one flow meter capable of...



Flammable Gas Detection for the D-Zero Gas System  

SciTech Connect

The use of flammable gas and high voltage in detector systems is common in many experiments at Fermilab. To mitigate the hazards associated with these systems, Fermilab Engineering Standard SD-45B (Ref. 1) was adopted. Since this note is meant to be a guide and not a mandatory standard, each experiment is reviewed for compliance with SD-45B by the flammable gas safety subcommittee. Currently, there are only two types of flammable gas in use, ethane (Appendix A) and methane (Appendix B). The worst flammable-gas case is C2H6 (ethane), which has an estimated flow rate that is 73% of the CH4 (methane) flow but a heat of combustion (in kcal/g-mole) that is 173% of that of methane. In the worst case, if ethane were to spew through its restricting orifice into its gas line at 0 psig and then through a catastrophic leak into Room 215 (TRD) or Room 511 (CDC/FDCNTX), the time that would be required to build up a greater than Class 1 inventory (0.4kg H2 equivalent) would be 5.2 hours (Ref. 2). Therefore a worst-case flammable gas leak would have to go undetected for over 5 hours in order to transform a either mixing room to an environment with a Risk Class greater than Class 1. The mixing systems, gas lines, and detectors themselves will be thoroughly leak checked prior to active service. All vessels that are part of the mixing systems will be protected from overpressure by safety valves vented outside the building. Both the input and output of all detector volumes are protected from overpressure in the same way. The volume immediately outside the central tracking detectors is continuously purged by nitrogen from boiloff from the main nitrogen dewar at the site. However, if flammable gas were to build up in the mixing rooms or particular detector areas, no matter how unlikely, flammable gas detectors that are part of the interlock chain of each gas mixing system will shut down the appropriate system. This includes shutting off the output of flammable gas manifolds within the gas shed. Similarly, if a fire were to break out anywhere in the D-ZERO Hall, fire sensors would stop the output of all flammable gas manifolds within the gas shed, by unpowering electrically controlled solenoid valves that are normally closed in the event of a power failure. Fire sensor contacts have not yet been installed.

Spires, L.D.; Foglesong, J.; /Fermilab



Detecting Changes of a Distant Gas Source with an Array of MOX Gas Sensors  

PubMed Central

We address the problem of detecting changes in the activity of a distant gas source from the response of an array of metal oxide (MOX) gas sensors deployed in an open sampling system. The main challenge is the turbulent nature of gas dispersion and the response dynamics of the sensors. We propose a change point detection approach and evaluate it on individual gas sensors in an experimental setup where a gas source changes in intensity, compound, or mixture ratio. We also introduce an efficient sensor selection algorithm and evaluate the change point detection approach with the selected sensor array subsets. PMID:23443385

Pashami, Sepideh; Lilienthal, Achim J.; Trincavelli, Marco



Detecting gas molecules via atomic magnetization.  


Adsorptions of gas molecules were found to alter the directions and magnitudes of magnetic moments of transition metal (Co, Fe) atoms adsorbed on graphene. Using first-principles calculations, we demonstrated that magnetism of surface atoms can be used to identify the kind of existing gas molecules via spin-reorientation and/or demagnetizations caused by the reconfigurations of 3d electron energy levels of Co and Fe. We suggest for the first time that magnetic properties of transition metal-embedded nanostructures can be used in highly selective gas-sensing applications. PMID:25036241

Choi, Heechae; Lee, Minho; Kim, Seungchul; Lee, Kwang-Ryeol; Chung, Yong-Chae



Detection of Greenhouse-Gas-Induced Climatic Change  

SciTech Connect

The objective of this report is to assemble and analyze instrumental climate data and to develop and apply climate models as a basis for (1) detecting greenhouse-gas-induced climatic change, and (2) validation of General Circulation Models.

Jones, P.D.; Wigley, T.M.L.



Gas chromatography with surface ionization detection of nitro pesticides  

Microsoft Academic Search

A surface ionization gas chromatographic detector, based upon positive surface ionization, was used in capillary gas chromatography\\u000a to sensitively and selectively detect nitro pesticides: pendimethalin, trifluralin, flumetralin. Higher sensitivity (better\\u000a detection limit), substance specificity, and advantageous applicability are reported. Sensitivity to pendimethalin, trifluralin,\\u000a and flumetralin was 1.4 C g?1, 1.1 C g?1, and 1.0 C g?1, respectively, with the linear

Seiji Takahashi; Futoshi Nagamura; Miki Sasaki; Toshihiro Fujii



Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

The goal of the work this quarter has been to partition and high-grade the Greater Green River basin for exploration efforts in the Upper Cretaceous tight gas play and to initiate resource assessment of the basin. The work plan for the quarter of July 1-September 30, 1998 comprised three tasks: (1) Refining the exploration process for deep, naturally fractured gas reservoirs; (2) Partitioning of the basin based on structure and areas of overpressure; (3) Examination of the Kinney and Canyon Creek fields with respect to the Cretaceous tight gas play and initiation of the resource assessment of the Vermilion sub-basin partition (which contains these two fields); and (4) Initiation analysis of the Deep Green River Partition with respect to the Stratos well and assessment of the resource in the partition.




Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

Building upon the partitioning of the Greater Green River Basin (GGRB) that was conducted last quarter, the goal of the work this quarter has been to conclude evaluation of the Stratos well and the prototypical Green River Deep partition, and perform the fill resource evaluation of the Upper Cretaceous tight gas play, with the goal of defining target areas of enhanced natural fracturing. The work plan for the quarter of November 1-December 31, 1998 comprised four tasks: (1) Evaluation of the Green River Deep partition and the Stratos well and examination of potential opportunity for expanding the use of E and P technology to low permeability, naturally fractured gas reservoirs, (2) Gas field studies, and (3) Resource analysis of the balance of the partitions.




Gas Chromatography for Detection of Viral Infections  

Microsoft Academic Search

Gas chromatograms of serum extracts of dogs inoculated with canine infectious hepatitis virus showed two metabolites not observed in uninoculated animals. Chromatograms of extracts of tissue cultures of dog kidney, inoculated with viruses causing canine hepatitis, herpes, and distemper, and a parainfluenza virus similar to simian virus-5, each showed two or more different metabolites. Two of the distinguishing products from

B. M. Mitruka; M. Alexander; L. E. Carmichael



Detection of Individual Gas Molecules Absorbed on Graphene  

Microsoft Academic Search

The ultimate aspiration of any detection method is to achieve such a level of sensitivity that individual quanta of a measured value can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity.

F. Schedin; A. K. Geim; S. V. Morozov; D. Jiang; E. H. Hill; P. Blake; K. S. Novoselov



Naturally fractured tight gas reservoir detection optimization  

SciTech Connect

During this quarter, work began on the regional structural and geologic analysis of the greater Green River basin (GGRB) in southwestern Wyoming, northwestern Colorado and northeastern Utah. The ultimate objective of the regional analysis is to apply the techniques developed and demonstrated during earlier phases of the project to sweet-spot delineation in a relatively new and underexplored play: tight gas from continuous-type Upper Cretaceous reservoirs of the GGRB. The primary goal of this work is to partition and high-grade the greater Green River basin for exploration efforts in the Cretaceous tight gas play. The work plan for the quarter of January 1, 1998--March 31, 1998 consisted of three tasks: (1) Acquire necessary data and develop base map of study area; (2) Process data for analysis; and (3) Initiate structural study. The first task and second tasks were completed during this reporting period. The third task was initiated and work continues.




Detection system for a gas chromatograph  


A method and apparatus are described for the quantitative analysis of vaporizable compounds, and in particular of polycyclic aromatic hydrocarbons which may be induced to fluoresce. The sample to be analyzed is injected into a gas chromatography column and is eluted through a narrow orifice into a vacuum chamber. The free expansion of the eluted sample into the vacuum chamber creates a supersonic molecular beam in which the sample molecules are cooled to the extent that the excited vibrational and rotational levels are substantially depopulated. The cooled molecules, when induced to fluoresce by laser excitation, give greatly simplified spectra suitable for analytical purposes. The laser induced fluorimetry provides great selectivity, and the gas chromatograph provides quantitative transfer of the sample to the molecular beam.

Hayes, John M. (Ames, IA); Small, Gerald J. (Ames, IA)



Optical detection of gas in producing oil wells  

NASA Astrophysics Data System (ADS)

A new production logging device has been field tested that uses innovative sensing technology to enable the direct detection and quantification of gas in multiphase flows. Four optical probes, deployed 90 degrees apart on the arms of a centralizer-like tool, measure the optical reflectance of the surrounding fluid. The probes are evenly spaced in the pipe cross section, and their orientation in space is accurately known through use of an integrated relative- bearing sensor. In gas-liquid mixtures, the optical signal reflected by the probe is used to determine gas holdup and a gas bubble count, which is related to gas flow rate. In addition, the individual sensor measurements are used to build an image of the gas flow in the well. These images are particularly useful in deviated and horizontal wells for better understanding the multiphase flow patterns and interpreting their inherent phase segregation occurring at such deviations. The new tool has been successfully field tested in wells throughout the world and the tool's capabilities are illustrated by example form both field and laboratory data sets. The new tool has been designed to detect the presence of gas, and hence its major application is to identify gas entries in oil/water wells or water/oil/condensate in gas wells. Because of its high sensitivity to minute amounts of gas, the tool can also be used to locate the bubble point when logging in the tubing. The introduction of optical sensing technology in this new tool represents an innovation in production logging. The provided data enable the direct detection and quantification of gas or liquid in multiphase mixtures, allowing the precise diagnosis of well problems and helping design of production enhancement interventions.

Cens, Fabien; Theron, Bernard; Vuhoang, D.; Faur, Marian; Rezgui, Fadhel; McKeon, D.



Metal oxide nanostructures for gas detection  

NASA Astrophysics Data System (ADS)

Currently, most of gas sensors on the market are produced in thin or thick film technologies with the use of ceramic substrates. It is expected that the miniature sensors needed in portable applications will be based on one-dimensional structures due to their low power consumption, fast and stable time response, small dimensions and possibility of embedding in integrated circuit together with signal conditioning electronics. The authors manufactured resistance type gas sensors based on ZnO and WO3 nanostructures. ZnO:Al nanorods with good cristallinity were obtained with electrodeposition method, while ZnO:Al nanofibres with varying diameters were obtained by electrospinning method. The sensors were built as a nanowire network. WO3 films with nanocrystalline surface were manufactured by deposition of a three layer WO3/W/WO3 structure by RF sputtering and successive annealing of the structure in appropriate temperature range. In effect a uniform nanostructurized metal oxide layer was formed. Investigation of sensors characteristics revealed good sensitivity to nitrogen dioxide at temperatures lower than these for conventional conductometric type sensors.

Maziarz, Wojciech; Pisarkiewicz, Tadeusz; Rydosz, Artur; Wysocka, Kinga; Czyrnek, Grzegorz



Temperature detection in a gas turbine  


A temperature detector includes a first metal and a second metal different from the first metal. The first metal includes a plurality of wires and the second metal includes a wire. The plurality of wires of the first metal are connected to the wire of the second metal in parallel junctions. Another temperature detector includes a plurality of resistance temperature detectors. The plurality of resistance temperature detectors are connected at a plurality of junctions. A method of detecting a temperature change of a component of a turbine includes providing a temperature detector include ing a first metal and a second metal different from the first metal connected to each other at a plurality of junctions in contact with the component; and detecting any voltage change at any junction.

Lacy, Benjamin; Kraemer, Gilbert; Stevenson, Christian



Wide-band gas leak imaging detection system using UFPA  

NASA Astrophysics Data System (ADS)

The leakage of toxic or hazardous gases not only pollutes the environment, but also threatens people's lives and property safety. Many countries attach great importance to the rapid and effective gas leak detection technology and instrument development. However, the gas leak imaging detection systems currently existing are generally limited to a narrow-band in Medium Wavelength Infrared (MWIR) or Long Wavelength Infrared (LWIR) cooled focal plane imaging, which is difficult to detect the common kinds of the leaking gases. Besides the costly cooled focal plane array is utilized, the application promotion is severely limited. To address this issue, a wide-band gas leak IR imaging detection system using Uncooled Focal Plane Array (UFPA) detector is proposed, which is composed of wide-band IR optical lens, sub-band filters and switching device, wide-band UFPA detector, video processing and system control circuit. A wide-band (3µm~12µm) UFPA detector is obtained by replacing the protection window and optimizing the structural parameters of the detector. A large relative aperture (F#=0.75) wide-band (3?m~12?m) multispectral IR lens is developed by using the focus compensation method, which combining the thickness of the narrow-band filters. The gas leak IR image quality and the detection sensitivity are improved by using the IR image Non-Uniformity Correction (NUC) technology and Digital Detail Enhancement (DDE) technology. The wide-band gas leak IR imaging detection system using UFPA detector takes full advantage of the wide-band (MWIR&LWIR) response characteristic of the UFPA detector and the digital image processing technology to provide the resulting gas leak video easy to be observed for the human eyes. Many kinds of gases, which are not visible to the naked eyes, can be sensitively detected and visualized. The designed system has many commendable advantages, such as scanning a wide range simultaneously, locating the leaking source quickly, visualizing the gas plume intuitively and so on. The simulation experiment shows that the gas IR imaging detection has great advantages and widely promotion space compared with the traditional techniques, such as point-contact or line-contactless detection.

Jin, Wei-qi; Li, Jia-kun; Dun, Xiong; Jin, Minglei; Wang, Xia



Compressive hyperspectral sensor for LWIR gas detection  

NASA Astrophysics Data System (ADS)

Focal plane arrays with associated electronics and cooling are a substantial portion of the cost, complexity, size, weight, and power requirements of Long-Wave IR (LWIR) imagers. Hyperspectral LWIR imagers add significant data volume burden as they collect a high-resolution spectrum at each pixel. We report here on a LWIR Hyperspectral Sensor that applies Compressive Sensing (CS) in order to achieve benefits in these areas. The sensor applies single-pixel detection technology demonstrated by Rice University. The single-pixel approach uses a Digital Micro-mirror Device (DMD) to reflect and multiplex the light from a random assortment of pixels onto the detector. This is repeated for a number of measurements much less than the total number of scene pixels. We have extended this architecture to hyperspectral LWIR sensing by inserting a Fabry-Perot spectrometer in the optical path. This compressive hyperspectral imager collects all three dimensions on a single detection element, greatly reducing the size, weight and power requirements of the system relative to traditional approaches, while also reducing data volume. The CS architecture also supports innovative adaptive approaches to sensing, as the DMD device allows control over the selection of spatial scene pixels to be multiplexed on the detector. We are applying this advantage to the detection of plume gases, by adaptively locating and concentrating target energy. A key challenge in this system is the diffraction loss produce by the DMD in the LWIR. We report the results of testing DMD operation in the LWIR, as well as system spatial and spectral performance.

Russell, Thomas A.; McMackin, Lenore; Bridge, Bob; Baraniuk, Richard



Derivatizations for Improved Detection of Alcohols by Gas Chrohatography and Photoionization Detection (GC-PID)  

Microsoft Academic Search

Pentafluorophenyldimethylsilyl chloride (flophemesyl chloride, F1) is a well known derivatization reagent for improved electron capture detection (ECD) in gas chromatography (GC)(GC-ECD), but it has never been utilized for improved detectability and sensitivity in GC-photoionization detection (GC-PID). We have now utilized a wide variety of flophemesyl alcohol derivatives in order to show a new approach for realizing greatly reduced minimum detection

I. S. Kruil; M. Swartz; J. N. Driscoll



Predicting detection probabilities for gas mixtures over HSI backgrounds  

SciTech Connect

Detecting and identifying weak gaseous plumes using thermal image data acquired by airborne detectors is an area of ongoing research. This contribution investigates the relative detectability of gas mixtures over different backgrounds and a range of plume temperatures that are warmer and cooler than the ground. The focus of this analysis to support mission planning. When the mission is intended to collect evidence of particular chemicals, the analysis presented is this report can be used to determine conditions under which useful data can be acquired. Initial analyses can be used to determine whether LWIR is useful for the anticipated gas, temperature, and background combination.

Tardiff, Mark F.; Walsh, Stephen J.; Anderson, Kevin K.; Chilton, Lawrence




SciTech Connect

The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting in corrosion fractures, presents an important aspect of our national security policy. The National Energy Technology Laboratory Strategic Center for Natural Gas (SCVG) is and has been funding research on various applicable techniques. The WVU research team has focused on monitoring pipeline background acoustic signals generated and transmitted by gas flowing through the gas inside the pipeline. In case of a pipeline infringement, any mechanical impact on the pipe wall, or escape of high-pressure gas, generates acoustic signals traveling both up and down stream through the gas. Sudden changes in flow noise are detectable with a Portable Acoustic Monitoring Package (PAMP), developed under this contract. It incorporates a pressure compensating microphone and a signal- recording device. Direct access to the gas inside the line is obtained by mounting such a PAMP, with a 1/2 inch NPT connection, to a pipeline pressure port found near most shut-off valves. An FFT of the recorded signal subtracted by that of the background noise recorded one-second earlier appears to sufficiently isolate the infringement signal to allow source interpretation. Using cell phones for data downloading might allow a network of such 1000-psi rated PAMP's to acoustically monitor a pipeline system and be trained by neural network software to positively identify and locate any pipeline infringement.

John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning




SciTech Connect

The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting in corrosion fractures, presents an important aspect of our national security policy. The National Energy Technology Laboratory Strategic Center for Natural Gas (SCVG) is and has been funding research on various applicable techniques. The WVU research team has focused on monitoring pipeline background acoustic signals generated and transmitted by gas flowing through the gas inside the pipeline. In case of a pipeline infringement, any mechanical impact on the pipe wall, or escape of high-pressure gas, generates acoustic signals traveling both up and down stream through the gas. Sudden changes in flow noise are detectable with a Portable Acoustic Monitoring Package (PAMP), developed under this contract. It incorporates a pressure compensating microphone and a signal- recording device. Direct access to the gas inside the line is obtained by mounting such a PAMP, with a 1/2 inch NPT connection, to a pipeline pressure port found near most shut-off valves. An FFT of the recorded signal subtracted by that of the background noise recorded one-second earlier appears to sufficiently isolate the infringement signal to allow source interpretation. Using cell phones for data downloading might allow a network of such 1000-psi rated PAMP's to acoustically monitor a pipeline system and be trained by neural network software to positively identify and locate any pipeline infringement.

John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning



Regional distribution of organochlorine insecticide residues in human milk from Egypt  

Microsoft Academic Search

The organochlorine insecticide residues in 60 human milk samples from 20 Egyptian governorates were analyzed by gas chromatography\\/electron capture and gas chromatography\\/mass spectrometry. The results showed that the main detected organochlorine insecticides were p,p'?DDE and lindane. Other HCH isomers, p,p‘?DDT and endosulfan I residues were detected in some samples, but aldrin and endrin were not detected in most of the

Mahmoud Saleh; Alaa Kamel; Awad Ragab



Detection of Smoldering Fire Using Tin Oxide Gas Sensors  

Microsoft Academic Search

Detecting technique of smoldering fire was examined using tin oxide gas sensors. Eight sensors were installed in a room. They were same type. Four kinds of materials were adopted as a fire-source material. The materials were cotton cloth, wallpaper, curtain cloth and woodchip, which were main smoldering fire-source materials in an indoor environment. The sensor outputs to gases evolved upon

Tsubasa Higashino; Ayako Sawada; Takashi Oyabu; Yoshinori Takei; Hidehito Nanto; Kiyoshi Toko



Gas sensor array for blueberry fruit disease detection and classification  

Microsoft Academic Search

A conducting polymer gas sensor array (electronic nose) was evaluated for detecting and classifying three common postharvest diseases of blueberry fruit: gray mold caused by Botrytis cinerea, anthracnose caused by Colletotrichum gloeosporioides, and Alternaria rot caused by Alternaria sp. Samples of ripe rabbiteye blueberries (Vaccinium virgatum cv. Brightwell) were inoculated individually with one of the three pathogens or left non-inoculated,

Changying Li; Gerard W. Krewer; Pingsheng Ji; Harald Scherm; Stanley J. Kays



Position sensitive radioactivity detection for gas and liquid chromatography  


A method and apparatus are provided for the position sensitive detection of radioactivity in a fluid stream, particularly in the effluent fluid stream from a gas or liquid chromatographic instrument. The invention represents a significant advance in efficiency and cost reduction compared with current efforts.

Cochran, Joseph L. (Knoxville, TN); McCarthy, John F. (Loudon, TN); Palumbo, Anthony V. (Oak Ridge, TN); Phelps, Tommy J. (Knoxville, TN)



An ALMA detection of circumnuclear molecular gas in M87  

NASA Astrophysics Data System (ADS)

We present the detection of circumnuclear molecular gas in M87 using the Atacama Large Millimeter/submillimeter Array (ALMA).M87 (3C 274) is an archetypal giant elliptical galaxy at the centre of the Virgo cluster and is a unique object in which to study the origin and properties of the interstellar medium (ISM) in a radio galaxy located in a dense environment. While a very well-known object across most of the electromagnetic spectrum, M87 has long lacked a detailed study in the (sub)millimeter range, requiring the advance in both sensitivity and angular resolution only now made possible by ALMA.Molecular gas in the inner part of M87 has previously been detected in single-dish observations, suggesting that the molecular gas likely resides in a circumnuclear disk-like structure. However, the unique ALMA capabilities now allow us to make the first detailed, interferometric, investigation of the properties of the ISM around the galaxy's supermassive black hole.Here, we present results of ALMA band 3 and 7 data which we have used to map the CO J=1-0 and CO J=3-2 lines, respectively. With this data we are able to trace the bulk of the molecular gas, the warmer denser gas, and the continuum emission, at an angular resolution of 1 arcsecond (~80 pc), providing the deepest and highest spatial resolution image yet of the molecular gas content of this giant elliptical galaxy.

Vlahakis, Catherine E.; Leon, Stephane; Martin, Sergio



Nonlinear preprocessing method for detecting peaks from gas chromatograms  

PubMed Central

Background The problem of locating valid peaks from data corrupted by noise frequently arises while analyzing experimental data. In various biological and chemical data analysis tasks, peak detection thus constitutes a critical preprocessing step that greatly affects downstream analysis and eventual quality of experiments. Many existing techniques require the users to adjust parameters by trial and error, which is error-prone, time-consuming and often leads to incorrect analysis results. Worse, conventional approaches tend to report an excessive number of false alarms by finding fictitious peaks generated by mere noise. Results We have designed a novel peak detection method that can significantly reduce parameter sensitivity, yet providing excellent peak detection performance and negligible false alarm rates from gas chromatographic data. The key feature of our new algorithm is the successive use of peak enhancement algorithms that are deliberately designed for a gradual improvement of peak detection quality. We tested our approach with real gas chromatograms as well as intentionally contaminated spectra that contain Gaussian or speckle-type noise. Conclusion Our results demonstrate that the proposed method can achieve near perfect peak detection performance while maintaining very small false alarm probabilities in case of gas chromatograms. Given the fact that biological signals appear in the form of peaks in various experimental data and that the propose method can easily be extended to such data, our approach will be a useful and robust tool that can help researchers highlight valid signals in their noisy measurements. PMID:19922615



Low-Cost Resonant Cavity Raman Gas Probe for Multi-Gas Detection  

NASA Astrophysics Data System (ADS)

Raman based gas sensing can be attractive in several industrial applications, due to its multi-gas sensing capabilities and its ability to detect O_2 and N_2. In this article, we have built a Raman gas probe, based on low-cost components, which has shown an estimated detection limit of 0.5 % for 30 second measurements of N_2 and O_2. While this detection limit is higher than that of commercially available equipment, our estimated component cost is approximately one tenth of the price of commercially available equipment. The use of a resonant Fabry-Pérot cavity increases the scattered signal, and hence the sensitivity, by a factor of 50. The cavity is kept in resonance using a piezo-actuated mirror and a photodiode in a feedback loop. The system described in this article was made with minimum-cost components to demonstrate the low-cost principle. However, it is possible to decrease the detection limit using a higher-powered (but still low-cost) laser and improving the collection optics. By applying these improvements, the detection limit and estimated measurement precision will be sufficient for e.g. the monitoring of input gases in combustion processes, such as e.g. (bio-)gas power plants. In these processes, knowledge about gas compositions with 0.1 % (absolute) precision can help regulate and optimize process conditions. The system has the potential to provide a low-cost, industrial Raman sensor that is optimized for specific gas-detection applications.

Thorstensen, J.; Haugholt, K. H.; Ferber, A.; Bakke, K. A. H.; Tschudi, J.



Calibration methods of carbon nanotube gas sensor for partial discharge detection in SF\\/sub 6  

Microsoft Academic Search

The authors proposed a new type of gas sensor for high sensitive detection of decomposition products generated by partial discharge (PD) in SF\\/sub 6\\/ gas. The sensor employed carbon nanotubes (CNTs) as gas sensing transducer and was fabricated by electrokinetic manipulation of CNTs using dielectrophoresis. Due to complicated gas decomposition process of SF\\/sub 6\\/ gas, calibration of the CNT gas

Weidong Ding; Ryota Hayashi; Junya Suehiro; Guangbin Zhou; Kiminobu Imasaka; Masanori Hara



Study for Blade Ceramic Coating Delamination Detection for Gas Turbine  

NASA Astrophysics Data System (ADS)

The component of the hot gas path in gas turbines can survive to very high temperatures because they are protected by ceramic Thermal Barrier Coating (TBC); the failure of such coating can dramatically reduce the component life. A reliable assessment of the Coating integrity and/or an Incipient TBC Damage Detection can help both in optimizing the inspection intervals and in finding the appropriate remedial actions. This study gives the TBC integrity; so other methods are required, like thermography to obtain indications of TBC delamination. Pulsed Thermography detects coating detachments and interface defects, with a large area of view but a spatial resolution of few mm. The mentioned techniques as a whole constitute a powerful tool for the life assessment of thermal barrier coating.

Choi, Choul-Jun; Choi, Seung Hyun; Kim, Jae-Yeol


Development of trace gas detection instrumentation. [using the heterodyne principle  

NASA Technical Reports Server (NTRS)

Breadboard hardware was constructed to demonstrate detection of a gaseous species by the heterodyne principle. The characteristics of the component parts were investigated and preliminary measurements were made to establish the sensitivity and selectivity of the method for gas analysis of CO, CO2, and N2O. A prototype heterodyne gas analyzer was designed, built, and brought into operational condition. Performance parameters of the prototype analyzer were investigated and its sensitivity to CO2 measured. Further development was undertaken for both the optical bench and the electronic processor components. A three-gas prototype analyzer, capable of measuring the gases CO, CO2, and CH4 was also constructed and tested. Detailed descriptions of the work and results are presented.



An industrial sensor for reliable ice detection in gas turbines  

SciTech Connect

Ice formation in the intake duct and compressor blading is a constant risk on gas turbines operating in regions where there are unfavorable ambient conditions. If allowed to continue there is a clear danger that pieces of ice will be ingested by the machine causing substantial damage. To protect the machine from possible damage, if ice is suspected by the operator the de-icing system is activated, injecting hot bleed air from the last compressor stages into the cold inlet air, naturally causing a decrease in power and efficiency. There exists a requirement for an ice detection system which will reliably detect the presence of ice and therefore optimize the use of bleed air for de-icing and reduce unnecessary power and efficiency losses. This paper discusses the necessary conditions for icing and describes a robust industrial sensor for reliable ice detection. The system, which is suitable for ground based gas turbines, has been installed on a 130MW gas turbine in Holland for the last three years and some of the results are presented here together with the economic advantages to be gained from installing such a system.

Freestone, J.W.; Weber, M. [Vibro-Meter SA, Fribourg (Switzerland). Dept. of Machinery Monitoring and Diagnostics



Photoacoustic detection and localization of small gas leaks.  


Leak detection and localization are critical manufacturing quality-control processes. Many industrial and domestic machines use or convey pressurized gases or liquids. Unintended leaks from machine components may be detrimental to consumers, manufacturers, and the environment. This paper describes a leak detection technique based on photoacoustic sounds produced by the interaction of a carbon dioxide (CO2) laser tuned to 10.6 micrometers and a photoactive tracer gas, sulfur hexaflouride (SF6), emitted by calibrated leak sources. Acoustic signals generated by a high-speed scan of the laser beam through the cloud of tracer gas formed near the leak are recorded in a bandwidth from 3 to 52 kHz by multiple microphones. From the recorded signals, the presence or absence of a leak may be deduced by comparison with the background noise level at the signal frequencies, which occur at the harmonics of the scan rate. When a leak is present, its location is determined from a simple model of the acoustic environment and matched field processing (MFP). Current results show that a gas leak of 1 cm3 per day can be detected and localized to within +/- 3 mm in a few seconds using four microphones, placed 0.41 m from the leak location, and an incoherent average of the MFP ambiguity surfaces at eight signal frequencies. Comparisons of the Bartlett and minimum-variance-distortionless matched field processors are also presented. PMID:10335619

Yönak, S H; Dowling, D R



Sensitive gas chromatographic detection of acetaldehyde and acetone using a reduction gas detector  

NASA Technical Reports Server (NTRS)

The response of a newly available mercuric oxide Reduction Gas Detector (RGD-2) to subpicomole and larger quantities of acetaldehyde and acetone is tested. The RGD-2 is found to be capable of subpicomole detection for these carbonyls and is more sensitive than an FID (Flame Ionization Detector) by an order of magnitude. Operating parameters can be further optimized to make the RGD-2 some 20-40 times more sensitive than an FID. The detector is linear over a wide range and is easily adapted to a conventional gas chromatograph (GC). Such a GC-RGD-2 system should be suitable for atmospheric carbonyl measurements in clean as well as polluted environments.

O'Hara, Dean; Singh, Hanwant B.




SciTech Connect

The West Virginia University natural gas transmission line leak detection research is only considering using readily available 1/2 inch pipeline access ports for the detection of leak generated signals. The main problem with leak signals is the low signal to noise ratio. One of the acoustic signals associated with gas escaping through a leak is only temporary and is in the form of a rarefaction wave originating when the leak is formed. Due to pipeline friction, over distance such a step function transitions to a ramp function. The ability to identify a leak by pipeline monitoring and signal processing depends a great deal on the quality and signal to noise ratio of the characteristics of the detectors used. Combinations of sensing devices are being used for the WVU sensor package and are contained in a removable sensor housing. The four sensors currently installed are a 1/2 inch 3 Hz-40 Khz microphone, an audible range moving coil sensor, a piezo-electric pressure transducer, and the WVU designed floating 3 inch diameter diaphragm to detect flow transient induced pressure ramp type signals. The WVU diaphragm sensor, which is currently under development, uses the same diaphragm principle as a high quality capacitance type microphone, but utilizes aerodynamic signal amplification. This type of amplification only amplifies the ramp-signal itself, not the random pipeline noise.

John L Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra



Naturally fractured tight gas reservoir detection optimization. Final report  

SciTech Connect

This DOE-funded research into seismic detection of natural fractures is one of six projects within the DOE`s Detection and Analysis of Naturally Fractured Gas Reservoirs Program, a multidisciplinary research initiative to develop technology for prediction, detection, and mapping of naturally fractured gas reservoirs. The demonstration of successful seismic techniques to locate subsurface zones of high fracture density and to guide drilling orientation for enhanced fracture permeability will enable better returns on investments in the development of the vast gas reserves held in tight formations beneath the Rocky Mountains. The seismic techniques used in this project were designed to capture the azimuthal anisotropy within the seismic response. This seismic anisotropy is the result of the symmetry in the rock fabric created by aligned fractures and/or unequal horizontal stresses. These results may be compared and related to other lines of evidence to provide cross-validation. The authors undertook investigations along the following lines: Characterization of the seismic anisotropy in three-dimensional, P-wave seismic data; Characterization of the seismic anisotropy in a nine-component (P- and S-sources, three-component receivers) vertical seismic profile; Characterization of the seismic anisotropy in three-dimensional, P-to-S converted wave seismic data (P-wave source, three-component receivers); and Description of geological and reservoir-engineering data that corroborate the anisotropy: natural fractures observed at the target level and at the surface, estimation of the maximum horizontal stress in situ, and examination of the flow characteristics of the reservoir.




Atypical Applications for Gas-coupled Laser Acoustic Detection  

NASA Astrophysics Data System (ADS)

Gas-coupled laser acoustic detection (GCLAD) was primarily developed to sense laser-generated ultrasound in composite materials. In a typical setup, a laser beam is directed parallel to the material surface. Radiated ultrasound waves deflect or displace the probe beam resulting from changes in the air's index of refraction. A position-sensitive photodetector senses the beam movement, and produces a signal proportional to the ultrasound wave. In this paper, we discuss three applications of GCLAD that take advantage of the unique detection characteristics. Directivity patterns of ultrasound amplitude in water demonstrate the use of GCLAD as a directional hydrophone. We also demonstrate the sensing of waveforms from a gelatin. The gelatin mimics ultrasound propagation through skin tissues. Lastly, we show how GCLAD can be used as a line receiver for continuous laser generation of ultrasound. CLGU may enable ultrasound scanning at rates that are orders of magnitude faster than current methods.

Caron, J. N.; Kunapareddy, P.



Tunnel-field-effect-transistor based gas-sensor: Introducing gas detection with a quantum-mechanical transducer  

E-print Network

Tunnel-field-effect-transistor based gas-sensor: Introducing gas detection with a quantum; published online 17 January 2013) A gas-sensor based on tunnel-field-effect-transistor (TFET) is proposed that leverages the unique current injection mechanism in the form of quantum-mechanical band-to-band tunneling


Microfluidic gas flow profiling using remote detection NMR  

SciTech Connect

Miniaturized fluid handling devices have recently attracted considerable interest in many areas of science1. Such microfluidic chips perform a variety of functions, ranging from analysis of biological macromolecules2,3 to catalysis of reactions and sensing in the gas phase4,5. To enable precise fluid handling, accurate knowledge of the flow properties within these devices is important. Due to low Reynolds numbers, laminar flow is usually assumed. However, either by design or unintentionally, the flow characteristic in small channels is often altered, for example by surface interactions, viscous and diffusional effects, or electrical potentials. Therefore, its prediction is not always straight-forward6-8. Currently, most microfluidic flow measurements rely on optical detection of markers9,10, requiring the injection of tracers and transparent devices. Here, we show profiles of microfluidic gas flow in capillaries and chip devices obtained by NMR in the remote detection modality11,12. Through the transient measurement of dispersion13, NMR is well adaptable for non-invasive, yet sensitive determination of the flow field and provides a novel and potentially more powerful tool to profile flow in capillaries and miniaturized flow devices.

Hilty, Christian; McDonnell, Erin; Granwehr, Josef; Pierce,Kimberly; Han, Song-I Han; Pines, Alexander



Microplasma mass spectrometric detection in capillary gas chromatography.  


A simple and miniaturized 350-kHz helium discharge for plasma mass spectrometric detection in gas chromatography (GC) has been developed. The plasma was sustained at low pressure within the end of the capillary GC column (0.32-mm i.d.) inside the ion source housing of a quadrupole mass spectrometer. This allowed direct introduction of ions from the plasma to the mass analyzer using only a repeller and electrostatic lenses to focus the ions. The plasma was sustained in only 25 mL min(-)(1) of helium, which was accepted by the mass spectrometer vacuum system. This low gas flow also served to enhance the energy density of the discharge and to produce a narrow spray of ions toward the mass analyzer. Due to the miniaturized nature of the plasma, it was operated at a low power level (2.0 W), and traces of oxygen were added to avoid deposition of carbon. With this new concept for GC plasma mass spectrometric detection, chlorine was successfully monitored down to the 2.2 pg s(-)(1) level without interference from elements like C, S, P, O, F, and N. PMID:21644750

Brede, C; Pedersen-Bjergaard, S; Lundanes, E; Greibrokk, T



Microfabricated planar glass gas chromatography with photoionization detection.  


We report the development of a microfabricated gas chromatography system suitable for the separation of volatile organic compounds (VOCs) and compatible with use as a portable measurement device. Hydrofluoric acid etching of 95x95mm Schott B270 wafers has been used to give symmetrical hemi-spherical channels within a glass substrate. Two matching glass plates were subsequently cold bonded with the channels aligned; the flatness of the glass surfaces resulted in strong bonding through van der Waals forces. The device comprised gas fluidic interconnections, injection zone and 7.5 and 1.4m long, 320microm internal diameter capillaries. Optical microscopy confirmed the capillaries to have fully circular channel profiles. Direct column heating and cooling could be achieved using a combination of resistive heaters and Peltier devices. The low thermal conductivity of glass allowed for multiple uniform temperature zones to be achieved within a single glass chip. Temperature control over the range 10-200 degrees C was achieved with peak power demand of approximately 25W. The 7.5m capillary column was static coated with a 2microm film of non-polar dimethylpolysiloxane stationary phase. A standard FID and a modified lightweight 100mW photoionization detector (PID) were coupled to the column and performance tested with gas mixtures of monoaromatic and monoterpene species at the parts per million concentration level. The low power GC-PID device showed good performance for a small set of VOCs and sub ng detection sensitivity to monoaromatics. PMID:20022335

Lewis, Alastair C; Hamilton, Jacqueline F; Rhodes, Christopher N; Halliday, Jaydene; Bartle, Keith D; Homewood, Philip; Grenfell, Robin J P; Goody, Brian; Harling, Alice M; Brewer, Paul; Vargha, Gergely; Milton, Martin J T



Hydrocarbon gas detection with microelectromechanical Fabry-Perot interferometer  

NASA Astrophysics Data System (ADS)

VTT Technical Research Centre of Finland has developed microelectromechanical (MEMS) Fabry-Perot interferometer (FPI) for hydrocarbon measurements. Fabry-Perot interferometer is a structure where is two highly reflective surfaces separated by a tunable air gap. The MEMS FPI is a monolithic device, i.e. it is made entirely on one substrate in a batch process, without assembling separate pieces together. The gap is adjusted by moving the upper mirror with electrostatic force, so there are no actual moving parts. The manufactured MEMS FPIs have been characterized. The tuning wavelength range of the MEMS FPI is 2.8-3.5 ?m and its spectral resolution is 50-60 nm. VTT has designed and manufactured a handheld size demonstrator device based on the technology presented in this abstract. This device demonstrates gas detecting by measuring cigarette lighter gas and various plastic materials transmission spectra. The demonstrator contains light source, gas cell, MEMS FPI, detector and control electronics. It is connected to a laptop by USB connection, additional power supply or connection is not needed.

Mannila, Rami; Tuohiniemi, Mikko; Mäkynen, Jussi; Näkki, Ismo; Antila, Jarkko



Detection of atmospheric trace gas species by DOAS gas-analyzer  

NASA Astrophysics Data System (ADS)

A differential optical absorption spectroscopy (DOAS) gas-analyzer was successfully tested. A high pressure 150-W Xe arc lamp was employed as a light source This system consisted of a coaxial telescope, a spectrometer, an analyzer and retroreflector. In order to record the spectra, a monochrometer with a grating and photodiode array was adopted. Gas analyzer spectral data bank includes more than 30 moleculas absorbed in UV spectral region. The measured absorption spectra were evaluated by using a least-squares fit to determine the average mixing ratio of each species in the atmosphere. A number of air pollutants concentrations: SO2, NO2, O3, etc were trace measured. Minimally detected concentration on pathlength 400 m is the unit of ppb at the time of accumulation of 2 min. The results of the field test measurements of pollutants in Tomsk are presented.

Geiko, Pavel P.; Smirnov, Sergey S.; Samokhvalov, Ignatii V.



The development of a pulsed laser imaging system for natural gas leak detection  

Microsoft Academic Search

The detection of gas leaks represents a critical operation performed regularly by the gas industry to maintain the integrity and safety of its vast network of piping, both above and below the ground. We are developing a technology that allows the real-time imaging of gas plumes in a television format. Termed backscatter absorption gas imaging (BAGI), the technique operates by

Thomas J. Kulp



Liquefied Noble Gas (LNG) detectors for detection of nuclear materials  

NASA Astrophysics Data System (ADS)

Liquefied-noble-gas (LNG) detectors offer, in principle, very good energy resolution for both neutrons and gamma rays, fast response time (hence high-count-rate capabilities), excellent discrimination between neutrons and gamma rays, and scalability to large volumes. They do, however, need cryogenics. LNG detectors in sizes of interest for fissionable material detection in cargo are reaching a certain level of maturity because of the ongoing extensive R&}D effort in high-energy physics regarding their use in the search for dark matter and neutrinoless double beta decay. The unique properties of LNG detectors, especially those using Liquid Argon (LAr) and Liquid Xenon (LXe), call for a study to determine their suitability for Non-Intrusive Inspection (NII) for Special Nuclear Materials (SNM) and possibly for other threats in cargo. Rapiscan Systems Laboratory, Yale University Physics Department, and Adelphi Technology are collaborating in the investigation of the suitability of LAr as a scintillation material for large size inspection systems for air and maritime containers and trucks. This program studies their suitability for NII, determines their potential uses, determines what improvements in performance they offer and recommends changes to their design to further enhance their suitability. An existing 3.1 liter LAr detector (microCLEAN) at Yale University, developed for R&}D on the detection of weakly interacting massive particles (WIMPs) was employed for testing. A larger version of this detector (15 liters), more suitable for the detection of higher energy gamma rays and neutrons is being built for experimental evaluation. Results of measurements and simulations of gamma ray and neutron detection in microCLEAN and a larger detector (326 liter CL38) are presented.

Nikkel, J. A.; Gozani, T.; Brown, C.; Kwong, J.; McKinsey, D. N.; Shin, Y.; Kane, S.; Gary, C.; Firestone, M.



Silicon Carbide-Based Hydrogen and Hydrocarbon Gas Detection  

NASA Technical Reports Server (NTRS)

Hydrogen and hydrocarbon detection in aeronautical applications is important for reasons of safety and emissions control. The use of silicon carbide as a semiconductor in a metal-semiconductor or metal-insulator-semiconductor structure opens opportunities to measure hydrogen and hydrocarbons in high temperature environments beyond the capabilities of silicon-based devices. The purpose of this paper is to explore the response and stability of Pd-SiC Schottky diodes as gas sensors in the temperature range from 100 to 400 C. The effect of heat treating on the diode properties as measured at 100 C is explored. Subsequent operation at 400 C demonstrates the diodes' sensitivity to hydrogen and hydrocarbons. It is concluded that the Pd-SiC Schottky diode has potential as a hydrogen and hydrocarbon sensor over a wide range of temperatures but further studies are necessary to determine the diodes' long term stability.

Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, D.; Liu, C. C.; Wu, Q. H.R



On-Column Micro Gas Chromatography Detection with Capillary-Based Optical Ring Resonators  

E-print Network

On-Column Micro Gas Chromatography Detection with Capillary-Based Optical Ring Resonators Siyka I their utility. In contrast, in gas chromatography (GC), gaseous samples are separated based on their interaction

Fan, Xudong "Sherman"


Environmental applications of gas chromatography/atomic emission detection.  


A gas chromatograph/atomic emission detector (GC/AED) system has been evaluated for its applicability to environmental analysis. Detection limits, elemental response factors, and regression analysis data were determined for 58 semivolatile environmental contaminants. Detection limits for injected analytes ranged from 0.17 to 3.0 ng on the hydrogen 486-nm channel, from 1.0 to 5.0 ng on the nitrogen 174-nm channel, from 0.65 to 11.7 ng on the oxygen 777-nm channel, from 0.071 to 3.0 ng on the chlorine 479-nm channel, and from 0.023 to 0.038 ng on the sulfur 181-nm channel. Mean elemental response factors (ERFs) measured on these channels, relative to the carbon 496-nm channel, were hydrogen, 0.084 (mean %RSD = 6.6); nitrogen, 0.246 (mean %RSD = 19); oxygen, 0.459 (mean %RSD = 16); and chlorine, 0.417 (mean %RSD = 3.6). The higher precision obtained for hydrogen and chlorine, relative to that for nitrogen and oxygen, is attributed to the ability to scan these elemental channels in the same GC run as the carbon 496-nm channel (diode array wavelength range limitation of ?40 nm/run). Mean ERFs of standard compounds were used to determine the molecular formulas of chlorinated hydrocarbons and chlorinated organosulfur compounds in a contaminated environmental soil sample. These formulas are in good agreement with the molecular weights and chlorine isotopic data obtained from low-resolution gas chromatography/mass spectrometry. PMID:21639376

Gurka, D F; Pyle, S; Titus, R



Detection of Smoldering Fire Using Tin Oxide Gas Sensors  

NASA Astrophysics Data System (ADS)

Detecting technique of smoldering fire was examined using tin oxide gas sensors. Eight sensors were installed in a room. They were same type. Four kinds of materials were adopted as a fire-source material. The materials were cotton cloth, wallpaper, curtain cloth and woodchip, which were main smoldering fire-source materials in an indoor environment. The sensor outputs to gases evolved upon the smoldering fire of the materials were measured. The differential characteristic of the output was derived to analyze. As for the results, it became obvious that the sensor locating at higher position had a higher sensitivity and it could sense the fire instantaneously. It is thought that the generated gases rise up directly toward the ceiling and reflect downward. A small type of electric cooking stove was used as a fire-source. The surface temperature of the stove plate arrived at 340 °C. A bar was adopted to set the sensors freely. In this experiment, three bars were adopted and the heights of the sensor position were 50, 100, 150 and 200 cm from the floor. It is effective to locate the sensor at higher position in detecting a smoldering fire. The sensor characteristics were analyzed using principal component analysis (PCA). The system could discriminate source materials among wallpaper, woodchip and curtain for smoldering fire by utilizing the result of PCA. But, the smoldering fire of cotton cloth could not be distinguished from that of curtain by this system. Each fire could be identified in four minutes.

Higashino, Tsubasa; Sawada, Ayako; Oyabu, Takashi; Takei, Yoshinori; Nanto, Hidehito; Toko, Kiyoshi


Detection methods for atoms and radicals in the gas phase  

NASA Astrophysics Data System (ADS)

This report lists atoms and free radicals in the gas phase which are of interest for environmental and flame chemistry and have been detected directly. The detection methods which have been used are discussed with respect to their range of application, specificity and sensitivity. In table 1, detection methods for the five atoms of group IV (C, Si, Ge, Sn, Pb) and about 60 radicals containing at least one atom of group IV are summarized (CH, Cd, Cf, CC1, CBr, Cn, Cs, CSe, CH2, CD2, Chf, Cdf, CHC1, CHBr, CF2, CC12, CBr2, CFC1, CFBr, CH3, CD3, CF3, CH2F, CH2C1, CH2Br, CHF2, CHC12, CHBr2, Hco, Fco, CH30, CD30, CH2OH, CH3S, Nco, CH4N, CH302, CF302; C2, C2N, C2H, C20, C2HO, C2H3, C2F3, C2H5, C2HsO, C2H4OH, CH3CO, CD3CO, C2H3O, C2H502, CH3COO2, C2H4N, C2H6N, C3; Si, SiF, SiF2, SiO, SiC, Si2; Ge, GeC, GeO, GeF, GeF2, GeCl2, Sn, SnF, SnO, SnF2, Pb, PbF, PbF2, PbO, PbS). In table 2 detection methods for about 25 other atoms and 60 radicals are listed: (H, D, O, O2, Oh, Od, HO2, DO2, F, Ci, Br, I, Fo, Cio, BrO, Io, FO2, C1O2, Li, Na, K, Rb, Cs, N, N3, Nh, Nd, Nf, Nci, NBr, NH2, ND2, Nhd, Nhf, NF2, NC12, N2H3, No, NO2, NO3, Hno, Dno, P, Ph, Pd, Pf, Pci, PH2, PD2, PF2, Po, As, AsO, AsS, Sb, Bi, S, S2, Sh, Sd, Sf, SF2, So, Hso, Dso, Sn, Se, Te, Se2, SeH, SeD, SeF, SeO, SeS, SeN, TeH, TeO, Bh, BH2, Bo, Bn, B02, Cd, Hg, UF5). The tables also cite some recent kinetic applications of the various methods.

Hack, W.


Recent Developments in Modulation Spectroscopy for Trace Gas Detection Using Tunable Diode Lasers  

Microsoft Academic Search

The need for higher sensitive detection technology for trace gas samples, either in the laboratory setup or in the atmospheric remote sensing has been a goal for several decades. The development of the tunable diode laser has propelled the progress of trace detection technology, and modulation technology enables the improvement of the detection sensitivity. As a result, the detection of

Kyuseok Song; Euo Chang Jung



Fault detection and isolation in aircraft gas turbine engines. Part 1: underlying concept  

E-print Network

of the blade-tip clearance in the turbine, labyrinth seal leakage, wear and erosion, and corrosion in the hot307 Fault detection and isolation in aircraft gas turbine engines. Part 1: underlying concept: aircraft propulsion, gas turbine engines, fault detection and isolation, statistical pattern recognition 1

Ray, Asok


Figure 1. Principle of wireless detection of gas centration with a chipless sensor.  

E-print Network

flexible and can be done with less effort, in comparison with a wired sensor network. In some special casesFigure 1. Principle of wireless detection of gas centration with a chipless sensor. A Novel Inkjet Printed Carbon Nanotube-Based Chipless RFID Sensor for Gas Detection Arnaud Vena#1 , Lauri Sydänheimo#2

Tentzeris, Manos


Naturally fractured tight gas: Gas reservoir detection optimization. Quarterly report, January 1--March 31, 1997  

SciTech Connect

Economically viable natural gas production from the low permeability Mesaverde Formation in the Piceance Basin, Colorado requires the presence of an intense set of open natural fractures. Establishing the regional presence and specific location of such natural fractures is the highest priority exploration goal in the Piceance and other western US tight, gas-centered basins. Recently, Advanced Resources International, Inc. (ARI) completed a field program at Rulison Field, Piceance Basin, to test and demonstrate the use of advanced seismic methods to locate and characterize natural fractures. This project began with a comprehensive review of the tectonic history, state of stress and fracture genesis of the basin. A high resolution aeromagnetic survey, interpreted satellite and SLAR imagery, and 400 line miles of 2-D seismic provided the foundation for the structural interpretation. The central feature of the program was the 4.5 square mile multi-azimuth 3-D seismic P-wave survey to locate natural fracture anomalies. The interpreted seismic attributes are being tested against a control data set of 27 wells. Additional wells are currently being drilled at Rulison, on close 40 acre spacings, to establish the productivity from the seismically observed fracture anomalies. A similar regional prospecting and seismic program is being considered for another part of the basin. The preliminary results indicate that detailed mapping of fault geometries and use of azimuthally defined seismic attributes exhibit close correlation with high productivity gas wells. The performance of the ten new wells, being drilled in the seismic grid in late 1996 and early 1997, will help demonstrate the reliability of this natural fracture detection and mapping technology.




Gas sensor array based on surface acoustic wave devices for vapors detection and analysis  

Microsoft Academic Search

We have developed a new electronic nose based on a gas sensor array to detect organic vapors. The gas sensor array is based on 2×2 non-continuously working oscillators equipped with differently polymer-coated surface acoustic wave (SAW) sensors. The SAW detection system which is employed to detect various organic molecules in a static system was prepared using 99.8 MHz two-port SAW

Da-Jeng Yao; Hsu-Chao Hao; Mei-Ching Chen; Je-Shin Chao



Evaluation of Gas Chromatography/Mini-IMS to Detect VOCs  

NASA Technical Reports Server (NTRS)

The Toxicology Laboratory at Johnson Space Center (JSC) has pioneered the use of gas chromatography-ion mobility spectrometry (GC/IMS) for measuring target volatile organic compounds (VOCs) aboard spacecraft. Graseby Dynamics, under contract to NASA/Wyle, has built several volatile organic analyzers (VOA) based on GC/IMS. Foremost among these have been the volatile organic analyzer-risk mitigation unit and the two flight VOA units for International Space Station (ISS). The development and evaluation of these instruments has been chronicled through presentations at the International Conference on Ion Mobility Spectrometry over the past three years. As the flight VOA from Graseby is prepared for operation on ISS at JSC, it is time to begin evaluations of technologies for the next generation VOA, Although the desired instrument characteristics for the next generation unit are the same as the current unit, the requirements are much more stringent. As NASA looks toward future missions beyond Earth environs, a premium will be placed upon small, light, reliable, autonomous hardware. It is with these visions in mind that the JSC Toxicology Laboratory began a search for the next generation VOA. One technology that is a candidate for the next generation VOA is GC/IMS. The recent miniaturization of IMS technology permits it to compete with other, inherently small, technologies such as chip-sized sensor arrays. This paper will discuss the lessons learned from the VOA experience and how that has shaped the design of a potential second generation VOA based upon GC/IMS technology. Data will be presented from preliminary evaluations of GC technology and the mini-IMS when exposed to VOCs likely to be detected aboard spacecraft. Results from the evaluation of an integrated GC/mini-IMS system will be shown if available.

Limero, Thomas; Reese, Eric; Peters, Randy; James, John T.; Billica, Roger (Technical Monitor)



Leakage detection of Marcellus Shale natural gas at an Upper Devonian gas monitoring well: a 3-d numerical modeling approach.  


Potential natural gas leakage into shallow, overlying formations and aquifers from Marcellus Shale gas drilling operations is a public concern. However, before natural gas could reach underground sources of drinking water (USDW), it must pass through several geologic formations. Tracer and pressure monitoring in formations overlying the Marcellus could help detect natural gas leakage at hydraulic fracturing sites before it reaches USDW. In this study, a numerical simulation code (TOUGH 2) was used to investigate the potential for detecting leaking natural gas in such an overlying geologic formation. The modeled zone was based on a gas field in Greene County, Pennsylvania, undergoing production activities. The model assumed, hypothetically, that methane (CH4), the primary component of natural gas, with some tracer, was leaking around an existing well between the Marcellus Shale and the shallower and lower-pressure Bradford Formation. The leaky well was located 170 m away from a monitoring well, in the Bradford Formation. A simulation study was performed to determine how quickly the tracer monitoring could detect a leak of a known size. Using some typical parameters for the Bradford Formation, model results showed that a detectable tracer volume fraction of 2.0 × 10(-15) would be noted at the monitoring well in 9.8 years. The most rapid detection of tracer for the leak rates simulated was 81 days, but this scenario required that the leakage release point was at the same depth as the perforation zone of the monitoring well and the zones above and below the perforation zone had low permeability, which created a preferred tracer migration pathway along the perforation zone. Sensitivity analysis indicated that the time needed to detect CH4 leakage at the monitoring well was very sensitive to changes in the thickness of the high-permeability zone, CH4 leaking rate, and production rate of the monitoring well. PMID:25144442

Zhang, Liwei; Anderson, Nicole; Dilmore, Robert; Soeder, Daniel J; Bromhal, Grant



Analog signal-selector circuit for quick gas detection from gas-sensor arrays  

Microsoft Academic Search

A Sixteen Input Maximum\\/Minimum Analog signal-selector Circuit (SIMMAC) is designed, simulated, and implemented using 2 ?m p-well (Orbit) CMOS technology. The circuit is useful in recognition of gas types from measurements of thin-film gas-sensor arrays. The output signal of each thin-film gas detector is typically a function of bias voltages, temperature and pressure, film type, frequency, and gas type. Gas

Hoda S. Abdel-ALy-Zohdy; Fatma A. El-Licy




EPA Science Inventory

The Lockheed Gas Analysis System (LGAS) grab-sampling method and the PETREX Static Surface Trapping Pyrolysis/Mass Spectrometry (SST-Py/MS) passive sampling technique for soil-gas measurement have been field tested at the Pittman Lateral near Henderson, Nevada. This site has unco...


Portable instrument and method for detecting reduced sulfur compounds in a gas  


A portable real time instrument for detecting concentrations in the part per billion range of reduced sulfur compounds in a sample gas. Ozonized air or oxygen and reduced sulfur compounds in a sample gas stream react to produce chemiluminescence in a reaction chamber and the emitted light is filtered and observed by a photomultiplier to detect reduced sulfur compounds. Selective response to individual sulfur compounds is achieved by varying reaction chamber temperature and ozone and sample gas flows, and by the use of either air or oxygen as the ozone source gas.

Gaffney, J.S.; Kelly, T.J.; Tanner, R.L.



Gas hydrate detection and mapping on the US east coast  

SciTech Connect

Project objectives are to identify and map gas hydrate accumulations on the US eastern continental margin using remote sensing (seismic profiling) techniques and to relate these concentrations to the geological factors that-control them. In order to test the remote sensing methods, gas hydrate-cemented sediments will be tested in the laboratory and an effort will be made to perform similar physical tests on natural hydrate-cemented sediments from the study area. Gas hydrate potentially may represent a future major resource of energy. Furthermore, it may influence climate change because it forms a large reservoir for methane, which is a very effective greenhouse gas; its breakdown probably is a controlling factor for sea-floor landslides; and its presence has significant effect on the acoustic velocity of sea-floor sediments.

Ahlbrandt, T.S.; Dillon, W.P.



Gas sensors for refractive index detection using surface plasmon resonance on nanosystem  

NASA Astrophysics Data System (ADS)

A plasmonic device for gas sensor is investigated for refractive index detection using surface plasmon resonance (SPR). The sensor device consists of nano-cavity antennas formed by metallic rectangular nanostrip array over a metal film, which monitors the changes of the refractive index by measuring the spectral shift of the resonance angle dip. The average detection sensitivity of the gas sensor is about 136 ° / RIU (refractive index units) for SPR excitation at 1550 nm telecommunication wavelength.

Zhao, Hua-Jun; Tian, Yong-You; Lei, Ju-Hua



Trace gas detection based on off-beam quartz enhanced photoacoustic spectroscopy: Optimization and performance evaluation  

E-print Network

the detection sensitivity to H2O vapor in ambient air at normal atmospheric pressure. A normalized noise control.1­4 In many cases, highly sensitive, compact, robust, and cost effective trace gas sensors are needed. Such a sensor can be realized using an innovative, sensitive trace gas sensor platform based


Lung cancer detection by proton transfer reaction mass-spectrometric analysis of human breath gas  

Microsoft Academic Search

BackgroundDetermination of the diagnostic usefulness of proton transfer reaction mass spectrometry (PTR-MS) for detecting primary lung cancer through analysis of volatile organic compounds (VOCs) in exhaled human breath was demonstrated in this investigation. Unlike, for example, gas-chromatographic analyses, PTR-MS can be used without time-consuming preconcentration of the gas samples.

Andreas Wehinger; Alex Schmid; Sergei Mechtcheriakov; Maximilian Ledochowski; Christoph Grabmer; Guenther A. Gastl; Anton Amann



Gas detection using low-temperature reduced graphene oxide sheets Ganhua Lu,1  

E-print Network

Gas detection using low-temperature reduced graphene oxide sheets Ganhua Lu,1 Leonidas E. Ocola,2 demonstrate a high-performance gas sensor using partially reduced graphene oxide GO sheets obtained through. A potential method to cost-effectively mass produce graphene-based devices is to first produce graphene oxide

Chen, Junhong



E-print Network

1 SELECTIVE FILTER FOR SnO2 BASED GAS SENSOR : APPLICATION TO HYDROGEN TRACE DETECTION G Saint-Etienne, France email: ABSTRACT The main drawback of the SnO2 based gas sensors sensitivity to ethanol, methane, carbon monoxide and hydrogen sulfide. Thick film SnO2 sensors are treated

Paris-Sud XI, Université de


Evaluating Gas-Phase Transport And Detection Of Noble Gas Signals From Underground Nuclear Explosions Using Chemical Tracers  

NASA Astrophysics Data System (ADS)

The 1993 Non-Proliferation Experiment (NPE) involved detonating 1 kiloton of chemical explosive in a subsurface cavity which also contained bottles of tracer gases (ref 1). That experiment provided an improved understanding of transport processes relevant to the detection of noble gas signals at the surface emanating from a clandestine underground nuclear explosion (UNE). As an alternative to performing large chemical detonations to simulate gas transport from UNEs, we have developed a test bed for subsurface gas transport, sampling and detection studies using a former UNE cavity. The test bed site allows for the opportunity to evaluate pathways to the surface created by the UNE as well as possible transport mechanisms including barometric pumping and cavity pressurization (ref 2). With the test bed we have monitored long-term chemical tracers as well as newly injected tracers. In order to perform high temporal resolution tracer gas monitoring, we have also developed a Subsurface Gas Smart Sampler (SGSS) which has application during an actual On Site Inspection (OSI) and is available for deployment in OSI field exercises planned for 2014. Deployment of five SGSS at the remote test bed has provided unparalleled detail concerning relationships involving tracer gas transport to the surface, barometric fluctuations and temporal variations in the natural radon concentration. We anticipate that the results of our tracer experiments will continue to support the development of improved noble gas detection technology for both OSI and International Monitoring System applications. 1. C.R. Carrigan et al., 1996, Nature, 382, p. 528. 2. Y. Sun and C.R. Carrigan, 2012, Pure Appl. Geophys., DOI 10.1007/s00024-012-0514-4.

Carrigan, C. R.; Hunter, S. L.; Sun, Y.; Wagoner, J. L.; Ruddle, D.; Anderson, G.; Felske, D.; Myers, K.; Zucca, J. J.; Emer, D. F.; Townsend, M.; Drellack, S.; Chipman, V.; Snelson, C. M.



Fiber-Optic Based Compact Gas Leak Detection System  

NASA Technical Reports Server (NTRS)

A propellant leak detection system based on Raman scattering principles is introduced. The proposed system is flexible and versatile as the result of the use of optical fibers. It is shown that multiple species can be monitored simultaneously. In this paper oxygen, nitrogen, carbon monoxide, and hydrogen are detected and monitored. The current detection sensitivity for both hydrogen and carbon monoxide is 1% partial pressure at ambient conditions. The sensitivity for oxygen and nitrogen is 0.5% partial pressure. The response time to changes in species concentration is three minutes. This system can be used to monitor multiple species at several locations.

deGroot, Wim A.



Quantitative thermal analysis technique for combustible gas detection  

Microsoft Academic Search

The Reaction Coulometer gas chromatograph detector was adapted for thermal analysis of solids. Response is predictable for pure standards and is easily calibrated. A quantitative analysis is obtained by measuring the methods of oxygen required for combustion of gases produced by pyrolysis, even though the mixture has unknown or complex products. Therefore, the technique is suited to thermal studies of

R. A. Susott; F. Shafizadeh; T. W. Aanerud



Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection  

PubMed Central

A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. PMID:22408500

Kanan, Sofian M.; El-Kadri, Oussama M.; Abu-Yousef, Imad A.; Kanan, Marsha C.



Temperature and pressure measurement based on tunable diode laser absorption spectroscopy with gas absorption linewidth detection  

NASA Astrophysics Data System (ADS)

A gas temperature and pressure measurement method based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) detecting linewidth of gas absorption line was proposed in this paper. Combined with Lambert-Beer Law and ideal gas law, the relationship between temperature, pressure and gas linewidth with Lorentzian line shape was investigated in theory. Taking carbon monoxide (CO) at 1567.32 nm for example, the linewidths of gas absorption line in different temperatures and pressures were obtained by simulation. The relationship between the linewidth of second harmonic and temperature, pressure with the coefficient 0.025 pm/K and 0.0645 pm/kPa respectively. According to the relationship of simulation results and detected linewidth, the undefined temperature and pressure of CO gas were measured. The gas temperature and pressure measurement based on linewidth detection, avoiding the influence of laser intensity, is an effective temperature and pressure measurement method. This method also has the ability to detect temperature and pressure of other gases with Lorentzian line shape.

Meng, Yunxia; Liu, Tiegen; Liu, Kun; Jiang, Junfeng; Wang, Tao; Wang, Ranran



Limit of detection of 15{sub N} by gas-chromatography atomic emission detection: Optimization using an experimental design  

SciTech Connect

This paper deals with the optimal conditions for the detection of {sup 15}N determined using a four-factor experimental design from [2{sup 13}C,-1,3 {sup 15}N] caffeine measured with an atomic emission detector (AED) coupled to gas chromatography (GC). Owing to the capability of a photodiodes array, AED can simultaneously detect several elements using their specific emission lines within a wavelength range of 50 nm. So, the emissions of {sup 15}N and {sup 14}N are simultaneously detected at 420.17 nm and 421.46 nm respectively. Four independent experimental factors were tested (1) helium flow rate (plasma gas); (2) methane pressure (reactant gas); (3) oxygen pressure; (4) hydrogen pressure. It has been shown that these four gases had a significant influence on the analytical response of {sup 15}N. The linearity of the detection was determined using {sup 15}N amounts ranging from 1.52 pg to 19 ng under the optimal conditions obtained from the experimental design. The limit of detection was studied using different methods. The limits of detection of {sup 15}N was 1.9 pg/s according to the IUPAC method (International-Union of Pure and Applied Chemistry). The method proposed by Quimby and Sullivan gave a value of 2.3 pg/s and that of Oppenheimer gave a limit of 29 pg/s. For each determination, and internal standard: 1-isobutyl-3.7 dimethylxanthine was used. The results clearly demonstrate that GC AED is sensitive and selective enough to detect and measure {sup 15}N-labelled molecules after gas chromatographic separation.

Deruaz, D.; Bannier, A.; Pionchon, C.



A solenoid failure detection system for cold gas attitude control jet valves  

NASA Technical Reports Server (NTRS)

The development of a solenoid valve failure detection system is described. The technique requires the addition of a radioactive gas to the propellant of a cold gas jet attitude control system. Solenoid failure is detected with an avalanche radiation detector located in the jet nozzle which senses the radiation emitted by the leaking radioactive gas. Measurements of carbon monoxide leakage rates through a Mariner type solenoid valve are presented as a function of gas activity and detector configuration. A cylindrical avalanche detector with a factor of 40 improvement in leak sensitivity is proposed for flight systems because it allows the quantity of radioactive gas that must be added to the propellant to be reduced to a practical level.

Johnston, P. A.



Optical methods and systems for detecting a constituent in a gas containing oxygen in harsh environments  


A method for detecting a gas phase constituent such as carbon monoxide, nitrogen dioxide, hydrogen, or hydrocarbons in a gas comprising oxygen such as air, includes providing a sensing material or film having a metal embedded in a catalytically active matrix such as gold embedded in a yttria stabilized zirconia (YSZ) matrix. The method may include annealing the sensing material at about C., exposing the sensing material and gas to a temperature above C., projecting light onto the sensing material, and detecting a change in the absorption spectrum of the sensing material due to the exposure of the sensing material to the gas in air at the temperature which causes a chemical reaction in the sensing material compared to the absorption spectrum of the sensing material in the absence of the gas. Systems employing such a method are also disclosed.

Carpenter, Michael A. (Scotia, NY); Sirinakis, George (Bronx, NY)



Detecting gas hydrate behavior in crude oil using NMR.  


Because of the associated experimental difficulties, natural gas hydrate behavior in black oil is poorly understood despite its grave importance in deep-water flow assurance. Since the hydrate cannot be visually observed in black oil, traditional methods often rely on gas pressure changes to monitor hydrate formation and dissociation. Because gases have to diffuse through the liquid phase for hydrate behavior to create pressure responses, the complication of gas mass transfer is involved and hydrate behavior is only indirectly observed. This pressure monitoring technique encounters difficulties when the oil phase is too viscous, the amount of water is too small, or the gas phase is absent. In this work we employ proton nuclear magnetic resonance (NMR) spectroscopy to observe directly the liquid-to-solid conversion of the water component in black oil emulsions. The technique relies on two facts. The first, well-known, is that water becomes essentially invisible to liquid state NMR as it becomes immobile, as in hydrate or ice formation. The second, our recent finding, is that in high magnetic fields of sufficient homogeneity, it is possible to distinguish water from black oil spectrally by their chemical shifts. By following changes in the area of the water peak, the process of hydrate conversion can be measured, and, at lower temperatures, the formation of ice. Taking only seconds to accomplish, this measurement is nearly direct in contrast to conventional techniques that measure the pressure changes of the whole system and assume these changes represent formation or dissociation of hydrates - rather than simply changes in solubility. This new technique clearly can provide accurate hydrate thermodynamic data in black oils. Because the technique measures the total mobile water with rapidity, extensions should prove valuable in studying the dynamics of phase transitions in emulsions. PMID:16570953

Gao, Shuqiang; House, Waylon; Chapman, Walter G



False-alarm characterization in hyperspectral gas-detection applications  

NASA Astrophysics Data System (ADS)

Chemical cloud detection using long-wave infrared (LWIR) hyperspectral-imaging sensors has many civilian and military applications, including chemical warfare threat mitigation, environmental monitoring, and emergency response. Current capabilities are limited by variation in background clutter as opposed to the physics of photon detection, and this makes the statistical characterization of clutter and clutter-induced false alarms essential to the design of practical systems. In this exploratory work, we use hyperspectral data collected both on the ground and in the air to spectrally and spatially characterize false alarms. Focusing on two widely-used detectors, the matched filter (MF) and the adaptive cosine estimator (ACE), we compare empirical false-alarm rates to their theoretical counterparts - detector output under Gaussian, t and t-mixture distributed data - and show that these models often underestimate false-alarm rates. Next, we threshold real detection maps and show that true detections and false alarms often exhibit very different spatial behavior. To exploit this difference and understand how spatial processing affects performance, the spatial behavior of false alarms must be understood. We take a first step in this direction by showing that, although the behavior may `look' quite random, it is not well captured by the complete-spatial-randomness model. Finally, we describe how our findings impact the design of real detection systems.

DiPietro, Robert S.; Truslow, Eric; Manolakis, Dimitris G.; Golowich, Steven E.; Lockwood, Ronald B.



Application of different analytical methods for determination of volatile chlorination by-products in drinking water  

Microsoft Academic Search

Four analytical methods have been applied for the determination of volatile chlorination by-products in drinking water, based on the following techniques: liquid–liquid extraction–gas chromatography–electron capture detection (LLE–GC–ECD); liquid–liquid extraction–gas chromatography–mass spectrometry (LLE–GC–MS); purge and trap–gas chromatography–mass spectrometry (purge and trap–GC–MS); and headspace-gas chromatography–mass spectrometry (headspace–GC–MS). The compounds studied were trihalomethanes, haloacetonitriles, haloketones, chloral hydrate and chloropicrin. LLE–GC–ECD method proved to

Anastasia D Nikolaou; Themistokles D Lekkas; Spyros K Golfinopoulos; Maria N Kostopoulou



Detection of Artificial Musk in Xihuangwan by Gas Chromatography-mass Spectrometery.  


Objective To control the quality of Xihuangwan by improving the qualitative detection of artificial musk inside this pill. Method The qualitative detection of artificial musk was carried out by gas chromatography-mass spectrometery(GC-MS). Result The established GC-MS successfully detected artificial musk in Xihuangwan. Conclusion GC-MS is reliable,accurate,and practical in the identification of artificial must inside Xihuangwan. PMID:25556729

Liu, Wei; Zou, Qin-Wen; Cheng, Xian-Long; Zhang, Ping; Shi, Yan; Wei, Feng; Zhang, Shu; Lun, Li-Jun; Yu, De-Quan



Recent developments in remote gas detection using molecular dispersion sensing  

NASA Astrophysics Data System (ADS)

In this paper we study signal amplitude in Chirp-modulated Chirped Laser Dispersion Spectroscopy (CM-CLaDS). CLaDS is a laser-based spectroscopic technique for molecular sensing that uses heterodyne detection to measure optical dispersion caused by molecular transitions. With baseline-free nature and high-immunity to optical power fluctuations CLaDS is well suited to long distance remote, open-path monitoring and stand-off chemical detection. In this work we analyze CM-CLaDS performance. We show that for certain conditions using proper modulation waveform can provide increase in the signal amplitude with respect to previously presented configurations.

Nikodem, Michal




EPA Science Inventory

Infrared (IR) imaging is the best method for detecting leaks of pollutant gases, but current technology based on cooled IR imagers is far too expensive ($75,000 to $150,000) for everyday field use by those who need it to meet regulatory limits—electric and petrochemical ...


Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers  

PubMed Central

Numerous medical studies show that tumor growth is accompanied by protein changes that may lead to the peroxidation of the cell membrane with consequent emission of volatile organic compounds (VOCs) by breath or intestinal gases that should be seen as biomarkers for colorectal cancer (CRC). The analysis of VOCs represents a non-invasive and potentially inexpensive preliminary screening technique. An array of chemoresistive gas sensors based on screen-printed metal oxide semiconducting films has been selected to discriminate gases of oncological interest, e.g., 1-iodononane and benzene, widely assumed to be biomarkers of colorectal cancer, from those of interference in the gut, such as methane and nitric oxide. PMID:25313496

Malagù, Cesare; Fabbri, Barbara; Gherardi, Sandro; Giberti, Alessio; Guidi, Vincenzo; Landini, Nicolò; Zonta, Giulia



Determination of dimethylselenide and dimethyldiselenide by gas chromatography–photoionization detection  

Microsoft Academic Search

A simple method for the determination of volatile selenium compounds employing a gas chromatograph equipped with a photoionization detector is described. The method involves the direct injection of dimethylselenide (DMS) or dimethyldiselenide (DMDS) into the gas chromatograph; no derivatization of the sample was required. The photoionization detector was capable of detecting 60pg (0.55pmol) of DMS and 150pg (0.80pmol) DMDS. Sensitivity

William J. Hunter; L. David Kuykendall



Research and Development of Non-Spectroscopic MEMS-Based Sensor Arrays for Targeted Gas Detection  

Microsoft Academic Search

The ability to monitor the integrity of gas volumes is of interest to the stockpile surveillance community. Specifically, the leak detection of noble gases, at relevant concentration ranges and distinguished from other chemical species that may be simultaneously present, is particularly challenging. Aside from the laboratory-based method of gas chromatography-mass spectrometry (GC-MS), where samples may be collected by solid-phase microextraction

A Loui; S K McCall



Determination of paroxetine levels in human plasma using gas chromatography with electron-capture detection.  


A simple, rapid and sensitive procedure using gas chromatography with electron-capture detection to measure paroxetine levels in human plasma has been developed. The analyte was extracted from plasma with ethyl acetate after basification of the plasma and then derivatized with heptafluorobutyric anhydride before gas chromatographic separation. The calibration curves were linear, with typical r2 values >0.99. The assay was highly reproducible and gave peaks with excellent chromatographic properties. PMID:11145064

Lai, C T; Gordon, E S; Kennedy, S H; Bateson, A N; Coutts, R T; Baker, G B



Some unique properties of gas chromatography coupled with atomic-emission detection.  


The atomic-emission detector in gas chromatography is enormously versatile in applications in analytical chemistry. Its unique properties of high selectivity for most elements and low limits of detection combine to make it the preferred detector for many analytical problems. In this review the stress is laid on the possibility of using it for compound-independent calibration, for determination of the empirical formula of an unknown analyte, for isotope-selective detection, and on derivatization to give AED-active derivatives with advantageous detection properties. Both metals and non-metals are considered and examples of the use of atomic emission detection in real-world analysis are discussed. PMID:12172669

Andersson, Jan T



Compact Resonance ?-Shaped Photoacoustic Cell for Gas Detection  

NASA Astrophysics Data System (ADS)

A compact resonance photoacoustic cell with a ?-shaped internal cavity and a volume of ~0.2 cm3 is developed. The design of the cell and an experimental setup for testing its operational capabilities are described. Results are presented from tests of the photoacoustic cell in experiments to detect light absorption by ammonia in nitrogen flows using a single-mode diode laser with a wavelength of ~1.53 ?m. The amplitude-frequency characteristics of the photoacoustic absorption response with and without ammonia are analyzed. The operation of the cell under conditions of resonance with the second longitudinal acoustic mode of the inner cavity of the cell (resonant frequency 4.38 kHz, Q-factor 13.9) is analyzed. The measured background signal level from the cell windows corresponds to an absorption coefficient of ~2.8·10-7 cm-1. The microphone-noise limited minimum detectable absorption is ~1.44·10-9 cm-1·W·Hz1/2.

Ulasevich, A. L.; Gorelik, A. V.; Kouzmouk, A. A.; Starovoitov, V. S.



Sensor Array Devices Utilizing Nano-structured Metal-oxides for Hazardous Gas Detection  

NASA Astrophysics Data System (ADS)

Methane and carbon monoxide are two hazardous gases which require continuous monitoring by gas sensors in underground coal mines for explosion prevention and toxicity, respectively. This work explored implementing miniaturized gas sensors in this area to simultaneously detect both gases for benefits of increased portability and reduced power consumption of the chemiresistive gas sensor device. The focus of this research was to understand how the particle size, morphology, and microstructure of the metaloxide film affected the gas sensor performance to the two gases of interest on miniaturized gas sensor devices in the form of microhotplate platforms. This was done through three main research studies. The first was conducted by growing SnO2 nanowires from SnO 2 particles using an Au-catalyst. Growth conditions including temperature, time, and oxygen partial pressure were explored to determine the formation aspects of the SnO2 nanowires. Gas sensor studies were completed that provided evidence that the SnO2 nanowires increased detection to a fixed concentration of carbon monoxide compared to SnO2 particles without nano-structure formation. A second research study was performed to compare the gas sensor performance of SnO2 nanoparticles, hierarchical particles, and micron-size particles. The nanoparticles were developed into an ink and deposited via ink-jet printing on the microhotplate substrates to control the microstructure of the metal-oxide film. By preventing agglomeration of the nanoparticle film, the SnO2 nanoparticles displayed similar gas sensor performance to methane and carbon monoxide as the hierarchical particles. Both nano-structures had much higher gas sensor response than the micron-size particles which confirms the surface area of the metal-oxide film is critical for reaction of the analyte gas at the surface. The last research study presented in the dissertation describes an oxide nanoparticle array developed for detecting methane and carbon monoxide in the presence of one another. A design of experiments was constructed and principal component analysis was used for determining the optimum temperatures of the metal-oxide elements. A four element array was developed with the SnO 2 and TiO2 sensor elements able to detect methane concentrations of interest and the ZnO and NiO sensor elements able to detect the carbon monoxide concentrations. A linear based prediction model was developed and tested for accuracy and reproducibility of the model to a series of random gas concentrations.

Andio, Mark A.


TREFEX: trend estimation and change detection in the response of MOX gas sensors.  


Many applications of metal oxide gas sensors can benefit from reliable algorithms to detect significant changes in the sensor response. Significant changes indicate a change in the emission modality of a distant gas source and occur due to a sudden change of concentration or exposure to a different compound. As a consequence of turbulent gas transport and the relatively slow response and recovery times of metal oxide sensors, their response in open sampling configuration exhibits strong fluctuations that interfere with the changes of interest. In this paper we introduce TREFEX, a novel change point detection algorithm, especially designed for metal oxide gas sensors in an open sampling system. TREFEX models the response of MOX sensors as a piecewise exponential signal and considers the junctions between consecutive exponentials as change points. We formulate non-linear trend filtering and change point detection as a parameter-free convex optimization problem for single sensors and sensor arrays. We evaluate the performance of the TREFEX algorithm experimentally for different metal oxide sensors and several gas emission profiles. A comparison with the previously proposed GLR method shows a clearly superior performance of the TREFEX algorithm both in detection performance and in estimating the change time. PMID:23736853

Pashami, Sepideh; Lilienthal, Achim J; Schaffernicht, Erik; Trincavelli, Marco



Detection of individual atoms in helium buffer gas and observation of their real-time motion  

NASA Technical Reports Server (NTRS)

Single atoms are detected and their motion measured for the first time to our knowledge by the fluorescence photon-burst method in the presence of large quantities of buffer gas. A single-clipped digital correlator records the photon burst in real time and displays the atom's transit time across the laser beam. A comparison is made of the special requirements for single-atom detection in vacuum and in a buffer gas. Finally, the probability distribution of the bursts from many atoms is measured. It further proves that the bursts observed on resonance are due to single atoms and not simply to noise fluctuations.

Pan, C. L.; Prodan, J. V.; Fairbank, W. M., Jr.; She, C. Y.



A Micro Gas Sensor Using TiO2 Nanotubes to Detect Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

To develop a portable gas sensor with low power consumption, we deposited a micro size sensing film (100×100 µm2) on a Si substrate with an integrated micro heater and electrodes constructed using micro-electro-mechanical system (MEMS) technology. TiO2 nanotubes ca. 500 nm long with a 50 nm diameter were used to sense and detect volatile organic compounds (VOCs). We demonstrate that the MEMS sensor responded well to ethanol and toluene in air at elevated temperatures, such as 500 °C, which suggests that it is a promising battery-operable micro gas sensor for detecting VOCs.

Kida, Tetsuya; Seo, Min-Hyun; Suematsu, Koichi; Yuasa, Masayoshi; Kanmura, Yuichi; Shimanoe, Kengo



Naturally fractured tight gas reservoir detection optimization. Quarterly report, January--March 1995  

SciTech Connect

This report describes progress in the following five projects: (1) Geologic assessment of the Piceance Basin; (2) Regional stratigraphic studies, Upper Cretaceous Mesaverde Group, southern Piceance Basin, Colorado; (3) Structurally controlled and aligned tight gas reservoir compartmentalization in the San Juan and Piceance Basins--Foundation for a new approach to exploration and resource assessments of continuous type deposits; (4) Delineation of Piceance Basin basement structures using multiple source data--Implications for fractured reservoir exploration; and (5) Gas and water-saturated conditions in the Piceance Basin, western Colorado--Implications for fractured reservoir detection in a gas-centered coal basin.




Combined raman and IR fiber-based sensor for gas detection  


A double-pass fiber-optic based spectroscopic gas sensor delivers Raman excitation light and infrared light to a hollow structure, such as a hollow fiber waveguide, that contains a gas sample of interest. A retro-reflector is placed at the end of this hollow structure to send the light back through the waveguide where the light is detected at the same end as the light source. This double pass retro reflector design increases the interaction path length of the light and the gas sample, and also reduces the form factor of the hollow structure.

Carter, Jerry C; Chan, James W; Trebes, James E; Angel, Stanley M; Mizaikoff, Boris



A Hazardous Gas Detection System for Aerospace and Commercial Applications  

NASA Technical Reports Server (NTRS)

The detection of explosive conditions in aerospace propulsion applications is important for safety and economic reasons. Microfabricated hydrogen, oxygen, and hydrocarbon sensors as well as the accompanying hardware and software are being developed for a range of aerospace safety applications. The development of these sensors is being done using MEMS (Micro ElectroMechanical Systems) based technology and SiC-based semiconductor technology. The hardware and software allows control and interrogation of each sensor head and reduces accompanying cabling through multiplexing. These systems are being applied on the X-33 and on an upcoming STS-95 Shuttle mission. A number of commercial applications are also being pursued. It is concluded that this MEMS-based technology has significant potential to reduce costs and increase safety in a variety of aerospace applications.

Hunter, G. W.; Neudeck, P. G.; Chen, L. - Y.; Makel, D. B.; Liu, C. C.; Wu, Q. H.; Knight, D.



A Hazardous Gas Detection System for Aerospace and Commercial Applications  

NASA Technical Reports Server (NTRS)

The detection of explosive conditions in aerospace propulsion applications is important for safety and economic reasons. Microfabricated hydrogen, oxygen, and hydrocarbon sensors as well as the accompanying hardware and software are being, developed for a range of aerospace safety applications. The development of these sensors is being done using MEMS (Micro ElectroMechanical Systems) based technology and SiC-based semiconductor technology. The hardware and software allows control and interrocation of each sensor head and reduces accompanying cabling through multiplexing. These systems are being, applied on the X-33 and on an upcoming STS-95 Shuttle mission. A number of commercial applications are also being pursued. It is concluded that this MEMS-based technology has significant potential to reduce costs and increase safety in a variety of aerospace applications.

Hunter, G. W.; Neudeck, P. G.; Chen, L.-Y.; Makel, D. B.; Liu, C. C.; Wu, Q. H.; Knight, D.



[Long optical path gas detection based on MEMS infrared light source].  


According to the requirements of infrared gas sensor for the light source, a broad wavelength, high modulation frequency, low power consumption and small size MEMS infrared light source is chosen as the radiation source, whose performance meets the requirements of infrared sensing system for the light source greatly. However, the infrared light source with the lamberation radiation characteristics is a surface light source, which is still with a large numerical aperture after shaping. It is difficult to increase the detection sensitivity by using a traditional long optical gas cell in a MEMS infrared light source detection system. Based on the dual-wavelength single beam differential detection method, an integrating sphere as the gas cell for long optical path is designed, which is able to realize long optical path for high sensitivity gas detection. The physical dimension is deduced for the equivalent optical path according to the flux conservation principle in the process of light transmission, solving the calculation problem of equivalent optical path of the integrating sphere cell. Using FPGA control chip, the MEMS infrared light source is droved at high frequency modulation and the detector output signal is processed, which makes the external circuit design much simple and flexible. It turns out that 166.7 cm equivalent optical path and the minimum concentration of methane of 0.001 x 10(-6) are achieved by the use of a 5 cm diameter integrating sphere in the research, improving the sensitivity of infrared detection system greatly. PMID:25007612

Du, Bin-Bin; Zhang, Peng; Gao, Wen-Hong; Shi, Yun-Bo; Zhu, Lin-Quan



IV-VI semiconductor lasers for gas phase biomarker detection  

NASA Astrophysics Data System (ADS)

A promising absorption spectroscopy application for mid-IR lasers is exhaled breath analysis where sensitive, selective, and speedy measurement of small gas phase biomarker molecules can be used to diagnose disease and monitor therapies. Many molecules such as nitric oxide, ethane, formaldehyde, acetaldehyde, acetone, carbonyl sulfide, and carbon disulfide have been connected to diseases or conditions such as asthma, oxidative stress, breast cancer, lung cancer, diabetes, organ transplant rejection, and schizophrenia. Measuring these and other, yet to be discovered, biomarker molecules in exhaled breath with mid-IR lasers offers great potential for improving health care since such tests are non-invasive, real-time, and do not require expensive consumables or chemical reagents. Motivated by these potential benefits, mid-IR laser spectrometers equipped with presently available cryogenically-cooled IV-VI lasers mounted in compact Stirling coolers have been developed for clinical research applications. This paper will begin with a description of the development of mid-IR laser instruments and their use in the largest known exhaled breath clinical study ever performed. It will then shift to a description of recent work on the development of new IV-VI semiconductor quantum well materials and laser fabrication methods that offer the promise of low power consumption (i.e. efficient) continuous wave emission at room temperature. Taken together, the demonstration of compelling clinical applications with large market opportunities and the clear identification of a viable pathway to develop low cost mid-IR laser instrumentation can create a renewed focus for future research and development efforts within the mid-IR materials and devices area.

McCann, Patrick; Namjou, Khosrow; Roller, Chad; McMillen, Gina; Kamat, Pratyuma




SciTech Connect

This report summarizes work performed by Physical Sciences Inc. (PSI) to advance the state-of-the-art of surveying for leaks of natural gas from transmission and distribution pipelines. The principal project goal was to develop means of deploying on an automotive platform an improved version of the handheld laser-based standoff natural gas leak detector previously developed by PSI and known as the Remote Methane Leak Detector or RMLD. A laser beam which interrogates the air for methane is projected from a spinning turret mounted upon a van. As the van travels forward, the laser beam scans an arc to the front and sides of the van so as to survey across streets and to building walls from a moving vehicle. When excess methane is detected within the arc, an alarm is activated. In this project, we built and tested a prototype Mobile RMLD (MRMLD) intended to provide lateral coverage of 10 m and one lateral scan for every meter of forward motion at forward speeds up to 10 m/s. Using advanced detection algorithms developed as part of this project, the early prototype MRMLD, installed on the back of a truck, readily detected simulated gas leaks of 50 liters per hour. As a supplement to the originally planned project, PSI also participated in a DoE demonstration of several gas leak detection systems at the Rocky Mountain Oilfield Testing Center (RMOTC) during September 2004. Using a handheld RMLD upgraded with the advanced detection algorithms developed in this project, from within a moving vehicle we readily detected leaks created along the 7.4 mile route of a virtual gas transmission pipeline.

Michael B. Frish; B. David Green; Richard T. Wainner; Francesca Scire-Scappuzzo; Paul Cataldi; Matthew C. Laderer



Detection of chlorinated pesticides on the surface of fungus using ToF-SIMS  

NASA Astrophysics Data System (ADS)

Chlorinated organic compounds are commonly used as pesticides (e.g. Lindane or DDT); unfortunately these compounds have the ability to be concentrated in aquatic and terrestrial food chains causing environmental problems due to their toxicity. Therefore there is a need for their removal using wastewater treatment plants. It is known that these pollutants adsorb on to the surface of the fungi Rhizopus arrizus from a water solution. However the actual mode of biosorption is unknown. We aim to investigate this interaction further using time-of-flight (ToF)-SIMS. Samples of fungus were grown in aqueous solutions containing Lindane then freeze-dried, the presence of Lindane was independently quantified by a gas chromatography-electron capture detector technique. The samples were then subjected to ToF-SIMS analysis. Evidence for Lindane was seen on the surface of the fungus, however it became apparent that the Lindane was too volatile for such an analysis. This rapid deterioration of signal is preventing a more in depth study of the interaction between Lindane and R. arrhizus. However it is anticipated that by utilising a frozen-hydrated sample preparation technique, of a type currently being developed at UMIST, that these challenges would be overcome.

Cliff, B.; Weibel, D. E.; Lockyer, N. P.; Jungnickel, H.; Stephens, G.; Vickerman, J. C.



A highly selective and sensitive "turn-on" fluorescence chemodosimeter for the detection of mustard gas.  


A new chemodosimetric protocol based on a tandem S-alkylation followed by desulfurisation reaction of rhodamine-thioamide with mustard gas is reported. The chemodosimeter is highly selective for potential DNA alkylating agents like sulfur mustard, over other simple alkyl halides with the limit of detection of 4.75 ?M. PMID:25186207

Raghavender Goud, D; Purohit, Ajay Kumar; Tak, Vijay; Dubey, Devendra Kumar; Kumar, Pravin; Pardasani, Deepak



Radioactivity detection in capillary gas chromatography of 3 H- and 14 C-labelled compounds  

Microsoft Academic Search

Radio gas chromatography (RGC) is a valuable tool for the analysis of radioactively labelled compounds. Recent advances in capillary GC, especially in column technology and instrumentation have also induced new possibilities in this field. With regard to the preservation of the achieved separation efficiency, radioactivity detection is the main problem in capillary RGC. Based on published data and on our

M. Matucha



First results from a marine controlled-source electromagnetic survey to detect gas hydrates offshore Oregon  

E-print Network

offshore Oregon K. A. Weitemeyer, S. C. Constable, K. W. Key, and J. P. Behrens Scripps Institution is a hazard to drilling, a potential hydrocarbon resource, and has been implicated as a factor in both from a marine controlled-source electromagnetic survey to detect gas hydrates offshore Oregon, Geophys

Key, Kerry


Sinking cities in Indonesia: ALOS PALSAR detects rapid subsidence due to groundwater and gas extraction  

E-print Network

Sinking cities in Indonesia: ALOS PALSAR detects rapid subsidence due to groundwater and gas and Atmospheric Science, University of Miami, USA b Institute of Technology, Bandung (ITB), Indonesia c Korea online xxxx Keywords: Subsidence Interferometric synthetic aperture radar SBAS time-series Indonesia We

Amelung, Falk


Optical gas sensor based on MgTPP thin film for the detection of alcohol vapors  

Microsoft Academic Search

Electronic nose devices are of increasing interest for the quality control of beverage and food processing. Optical gas sensors that require low electrical power are in great need for such devices. Magnesium 5, 10, 15, 20-tetraphenylporphyrin thin film sensors have been fabricated by spin coating onto glass substrates for detecting specific alcoholic volatile organic compounds (VOCs). Responses of the films

Johannes Mensing; Sumana Kladsomboon; Teerakiat Kerdcharoen



Naturally fractured tight gas reservoir detection optimization. Quarterly technical progress report, April 1995--June 1995  

SciTech Connect

Research continued on methods to detect naturally fractured tight gas reservoirs. This report contains a seismic survey map, and reports on efforts towards a source test to select the source parameters for a 37 square mile compressional wave 3-D seismic survey. Considerations of the source tests are discussed.




Naturally fractured tight gas reservoir detection optimization. Quarterly report, January 1 - March 31, 1996  

SciTech Connect

The objective is to determine methods for detection and mapping of naturally fractured systems for economic production of natural gas from fractured reservoirs. This report contains: 3D P-wave alternate processing; down hole 3C geophone analysis; fracture pattern analysis of the Fort Union and Wind River Basin; 3D-3C seismic processing; and technology transfer.




Self-heated silicon nanowires for high performance hydrogen gas detection.  


Self-heated silicon nanowire sensors for high-performance, ultralow-power hydrogen detection have been developed. A top-down nanofabrication method based on well-established semiconductor manufacturing technology was utilized to fabricate silicon nanowires in wafer scale with high reproducibility and excellent compatibility with electronic readout circuits. Decoration of palladium nanoparticles onto the silicon nanowires enables sensitive and selective detection of hydrogen gas at room temperature. Self-heating of silicon nanowire sensors allows us to enhance response and recovery performances to hydrogen gas, and to reduce the influence of interfering gases such as water vapor and carbon monoxide. A short-pulsed heating during recovery was found to be effective for additional reduction of operation power as well as recovery characteristics. This self-heated silicon nanowire gas sensor will be suitable for ultralow-power applications such as mobile telecommunication devices and wireless sensing nodes. PMID:25670503

Ahn, Jae-Hyuk; Yun, Jeonghoon; Moon, Dong-Il; Choi, Yang-Kyu; Park, Inkyu



A Detection of Molecular Gas Emission in the Host Galaxy of GRB 080517  

NASA Astrophysics Data System (ADS)

We have observed the host galaxy of the low-redshift, low-luminosity Swift GRB 080517 at 105.8 GHz using the IRAM Plateau de Bure interferometer. We detect an emission line with integrated flux S?? = 0.39 ± 0.05 Jy km s-1—consistent both spatially and in velocity with identification as the J = 1-0 rotational transition of carbon monoxide (CO) at the host galaxy redshift. This represents only the third long gamma-ray burst (GRB) host galaxy with molecular gas detected in emission. The inferred molecular gas mass, MH_2˜ 6.3× 10^8 M ?, implies a gas consumption timescale of ~40 Myr if star formation continues at its current rate. Similar short timescales appear characteristic of the long GRB population with CO observations to date, suggesting that the GRB in these sources occurs toward the end of their star formation episode.

Stanway, E. R.; Levan, A. J.; Tanvir, N. R.; Wiersema, K.; van der Laan, T. P. R.



Zeolite-based Impedimetric Gas Sensor Device in Low-cost Technology for Hydrocarbon Gas Detection  

PubMed Central

Due to increasing environmental concerns the need for inexpensive selective gas sensors is increasing. This work deals with transferring a novel zeolite-based impedimetric hydrocarbon gas sensor principle, which has been originally manufactured in a costly combination of photolithography, thin-film processes, and thick-film processes to a low-cost technology comprising only thick-film processes and one electroplating step. The sensing effect is based on a thin chromium oxide layer between the interdigital electrodes and a Pt-loaded ZSM-5 zeolite film. When hydrocarbons are present in the sensor ambient, the electrical sensor impedance increases strongly and selectively. In the present work, the chromium oxide film is electroplated on Au screen-printed interdigital electrodes and then oxidized to Cr2O3. The electrode area is covered with the screen-printed zeolite. The sensor device is self-heated utilizing a planar platinum heater on the backside. The best sensor performance is obtained at a frequency of 3 Hz at around 350 °C. The good selectivity of the original sensor setup could be confirmed, but a strong cross-sensitivity to ammonia occurs, which might prohibit its original intention for use in automotive exhausts.

Reiß, Sebastian; Hagen, Gunter; Moos, Ralf



Sensitive assay of methadone in plasma by using capillary gas chromatography with photoionization detection.  


A new gas chromatographic assay for methadone, utilizing a fused-silica capillary column, is presented. Extreme sensitivity was reached, compared to nitrogen-phosphorus and mass spectrometry detection, by employing a photoionization detector. Plasma concentrations of methadone as low as 1 ng/ml can easily be detected and, by further optimization, 0.1 ng/ml was reached. The minimum detectable amount of methadone reaching the detector was 70 fg. The results indicate that the photoionization detector has potential as a tool in drug monitoring. PMID:3700556

Norlander, B; Carlsson, B; Bertler, A




SciTech Connect

Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. The scope of the work involved designing and developing an airborne, optical remote sensor capable of sensing methane and, if possible, ethane for the detection of natural gas pipeline leaks. Flight testing using a custom dual wavelength, high power fiber amplifier was initiated in February 2005. Ophir successfully demonstrated the airborne system, showing that it was capable of discerning small amounts of methane from a simulated pipeline leak. Leak rates as low as 150 standard cubic feet per hour (scf/h) were detected by the airborne sensor.

Jerry Myers



Gas chromatography with flame photometric detection of 31 organophosphorus pesticide residues in Alpinia oxyphylla dried fruits.  


A simple, rapid and effective gas chromatography-flame photometric detection method was established for simultaneous multi-component determination of 31 organophosphorus pesticides (OPPs) residues in Alpinia oxyphylla, which is widely consumed as a traditional medicine and food in China. Sample preparation was completed in a single step without any clean-up procedure. All pesticides expressed good linear relationships between 0.004 and 1.0 ?g/mL with correlation coefficients higher than 0.9973. The method gave satisfactory recoveries for most pesticides. The limits of detection varied from 1 to 10 ng/mL, and the limits of quantification (LOQs) were between 4 and 30 ng/mL. The proposed method was successfully applied to 55 commercial samples purchased from five different areas. Five pesticide residues were detected in four (7.27%) samples. The positive samples were confirmed by gas chromatography with tandem mass spectrometry (GC-MS/MS). PMID:24874387

Zhao, Xiangsheng; Kong, Weijun; Wei, Jianhe; Yang, Meihua



Generalized average of signals (GAS) - a new method for denoising and phase detection  

NASA Astrophysics Data System (ADS)

A novel method called Generalized Average of Signals (GAS) was developed and tested during the last two years (Málek et al., in press). This method is designed for processing of seismograms from dense seismic arrays and is convenient mainly for denoising and weak phase detection. The main idea of the GAS method is based on non-linear stacking of seismograms in frequency domain, which considerably improves signal-to-noise ratio of coherent seismograms. Several synthetic tests of the GAS method are presented and the results are compared with the PWS method of Schimell and Paulssen (1997). Moreover, examples of application on real data are presented. These examples were chosen to show a broad applicability of the method in experiments of different scales. The first one shows identification of S-waves on seismograms from shallow seismic. The second one concerns identification of converted waves from local earthquakes registered at the WEBNET local network in western Bohemia. Finally, the third one depicts identification of PKIKP onsets on seismograms of teleseismic earthquakes. Schimmel, M., Paulssen H. (1997): Noise reduction and detection of weak, coherent signals through phase- weighted stacks. Geophys. J. Int. 130, 497-505. Málek J., Kolínský P., Strunc J. and Valenta J. (2007): Generalized average of signals (GAS) - a new method for detection of very weak waves in seismograms. Acta Geodyn. et Geomater., in press.

Malek, J.; Kolinsky, P.; Strunc, J.; Valenta, J.



An integrated GPS-FID system for airborne gas detection of pipeline right-of-ways  

SciTech Connect

Pipeline integrity, safety and environmental concerns are of prime importance in the Canadian natural gas industry. Terramatic Technology Inc. (TTI) has developed an integrated GPS/FID gas detection system known as TTI-AirTrac{trademark} for use in airborne gas detection (AGD) along pipeline right-of-ways. The Flame Ionization Detector (FID), which has traditionally been used to monitor air quality for gas plants and refineries, has been integrated with the Global Positioning System (GPS) via a 486 DX2-50 computer and specialized open architecture data acquisition software. The purpose of this technology marriage is to be able to continuously monitor air quality during airborne pipeline inspection. Event tagging from visual surveillance is used to determine an explanation of any delta line deviations (DLD). These deviations are an indication of hydrocarbon gases present in the plume that the aircraft has passed through. The role of the GPS system is to provide mapping information and coordinate data for ground inspections. The ground based inspection using a handheld multi gas detector will confirm whether or not a leak exists.

Gehue, H.L.; Sommer, P.



Determination of dimethylselenide and dimethyldiselenide by gas chromatography-photoionization detection.  


A simple method for the determination of volatile selenium compounds employing a gas chromatograph equipped with a photoionization detector is described. The method involves the direct injection of dimethylselenide (DMS) or dimethyldiselenide (DMDS) into the gas chromatograph; no derivatization of the sample was required. The photoionization detector was capable of detecting 60 pg (0.55 pmol) of DMS and 150pg (0.80pmol) DMDS. Sensitivity was 10-50 times greater with DMS and 4-20 times greater with DMDS when the photoionization detector was employed than when the flame ionization detector was employed. PMID:15233545

Hunter, William J; Kuykendall, L David



Tunable fiber laser and fiber amplifier based photoacoustic spectrometer for trace gas detection.  


A new wavelength modulated photoacoustic spectrometer based on a near-infrared tunable erbium doped fiber laser (TEDFL) and an erbium doped fiber amplifier (EDFA) is first developed for trace gas detection. This sensor has been applied to the detection of ammonia using a first longitudinal resonant photoacoustic cell with double absorption optical path (L=20cm) and lock-in harmonic detection technique. The minimum detectable limit of 3 parts-per-billion volume (signal-to-noise ratio=1) and response time of approximately 1min is achieved at room temperature and atmospheric pressure with 100ms time constant and 500mW optical power at the 1531.7nm transition line. PMID:19781982

Peng, Yong; Zhang, Wang; Li, Liang; Yu, Qingxu



Periodically porous top electrodes on vertical nanowire arrays for highly sensitive gas detection.  


Nanowires of various materials and configurations have been shown to be highly effective in the detection of chemical and biological species. In this paper, we report a novel, nanosphere-enabled approach to fabricating highly sensitive gas sensors based on ordered arrays of vertically aligned silicon nanowires topped with a periodically porous top electrode. The vertical array configuration helps to greatly increase the sensitivity of the sensor while the pores in the top electrode layer significantly improve sensing response times by allowing analyte gases to pass through freely. Herein, we show highly sensitive detection to both nitrogen dioxide (NO(2)) and ammonia (NH(3)) in humidified air. NO(2) detection down to 10 parts per billion (ppb) is demonstrated and an order-of-magnitude improvement in sensor response time is shown in the detection of NH(3). PMID:21817785

In, Hyun Jin; Field, Christopher R; Pehrsson, Pehr E



Innovative high pressure gas MEM's based neutron detector for ICF and active SNM detection.  

SciTech Connect

An innovative helium3 high pressure gas detection system, made possible by utilizing Sandia's expertise in Micro-electrical Mechanical fluidic systems, is proposed which appears to have many beneficial performance characteristics with regards to making these neutron measurements in the high bremsstrahlung and electrical noise environments found in High Energy Density Physics experiments and especially on the very high noise environment generated on the fast pulsed power experiments performed here at Sandia. This same system may dramatically improve active WMD and contraband detection as well when employed with ultrafast (10-50 ns) pulsed neutron sources.

Martin, Shawn Bryan; Derzon, Mark Steven; Renzi, Ronald F.; Chandler, Gordon Andrew



Optically multiplexed multi-gas detection using quantum cascade laser photoacoustic spectroscopy.  


We report high-throughput, nondispersive optical multiplexing of laser beams using a scanning galvanometer. We have utilized this technique for multispecies trace-gas detection using multiple quantum cascade laser photoacoustic spectroscopy. We demonstrate switching from one laser to another in less than 1 s, a performance level needed for a comprehensive multispecies sensor, and a high signal-to-noise ratio detection of five gaseous components, NH(3), NO(2), dimethyl methyl phosphonate (DMMP, a simulant for nerve agents), acetone, and ethylene glycol, in a room air gas mixture containing approximately 3 ppb of NH(3), approximately 8 ppb of NO(2), approximately 20 ppb of DMMP, approximately 30 ppb of acetone, and approximately 40 ppb of ethylene glycol. PMID:18806847

Mukherjee, Anadi; Prasanna, Manu; Lane, Michael; Go, Rowel; Dunayevskiy, Ilya; Tsekoun, Alexei; Patel, C Kumar N



One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection  

PubMed Central

Recently; one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio; which is an outstanding advantage for gas sensors with high sensitivity and fast response. In addition; the nature of the single crystals is favorable for the studies of the response mechanism. On the other hand; one main merit of the field-effect sensors is to provide an extra gate electrode to realize the current modulation; so that the sensitivity can be dramatically enhanced by changing the conductivity when operating the sensors in the subthreshold regime. This article reviews the recent developments in the field of 1D nanostructure FET for gas detection. The sensor configuration; the performance as well as their sensing mechanism are evaluated. PMID:25090418

Zhao, Xiaoli; Cai, Bin; Tang, Qingxin; Tong, Yanhong; Liu, Yichun



A New Low-Cost Electronic System to Manage Resistive Sensors for Gas Detection  

Microsoft Academic Search

In this paper, a new electronic system for gas detection is presented. Particular attention is focused on electronic noses that employ several resistive sensors. New resistive sensors may have high value due to new substances (TiO2) or to low-cost fabrication process and, supposing to use these sensors together with traditional ones (SnO2), a novel instrument to manage high-value resistive sensors

Alessandro Depari; Matteo Falasconi; Alessandra Flammini; Daniele Marioli; Stefano Rosa; Giorgio Sberveglieri; Andrea Taroni



Detection of disturbances in pulmonary gas exchanges during exercise from arterialized earlobe P O 2  

Microsoft Academic Search

Blood sampling from the arterialized earlobe is widely used in clinical exercise testing but Fajac et al. (1998) (Eur. Respir. J. 11, 712–715) have shown that arterialized PO2(PcCO2) is not a valid surrogate for PaO2. In the present study, in order to detect disturbances in pulmonary gas exchanges during clinical exercise testing from the alveolar-arterial gradient of PO2 (P[Ai­a]O2), a

Bernard Aguilaniu; Jocelyne Maitre; Samia Diab; Hélène Perrault; François Péronnet



Detection of ethanol gas concentration by fuel cell sensors fabricated using a solid polymer electrolyte  

Microsoft Academic Search

Fuel cells using a polymer electrolyte membrane were successfully fabricated and tested for the detection of ethanol gas concentration. Nafion 115 membrane was used for the polymer electrolyte and 10% Pt\\/C sheets with 0.5 mg\\/cm2 Pt loading were used as catalyst electrodes. The peak height of electrical signal obtained from the fuel cells was found to be quite linear with

Ki-Chul Kim; Sung M Cho; Hoo-Gon Choi



Condensed matter photoacoustic spectroscopy and detection using gas phase signal generation  

SciTech Connect

Photoacoustic (PA) spectroscopy and detection involving condensed samples and gas phase signal generation are briefly reviewed. Theoretical considerations, instrumentation, and applications are discussed with emphasis on electronic materials studies. Applications include PA absorption spectroscopy of single crystal CdS and ion implanted GaAs int he bandgap region, PA imaging of compositional variations related to thermal properties in H/sub gl-x/Cd/sub x/Te, and laser heating of Ge.

McClelland, J.F.



Molecular Gas and Nuclear Activity in Radio Galaxies Detected by IRAS  

E-print Network

This paper reports the latest results from a millimeter-wave (CO) spectroscopic survey of IRAS-detected radio galaxies with L_1.4GHz ~ 10^23-28 W/Hz in the redshift range z ~ 0.02-0.15. The IRAS flux-limited sample contains 33 radio galaxies with different radio morphologies and a broad range of infrared luminosities L_IR = 10^9-12 L_sun), allowing for an investigation of (a) whether low-z radio-selected AGN reside in molecular gas-rich host galaxes, and (b) whether the CO properties are correlated with the properties of the host galaxy or the AGN. All of the radio galaxies in Mazzarella et al. (1993) and Mirabel et al. (1989) have been reobserved. Three new CO detections have been made, raising the total number of CO detections to nine and setting the survey detection rate at ~ 25%. Many of the CO lines have double-peaked profiles, and the CO line widths are broad (average Delta v_FWHM ~ 500+/-130 km/s), exceeding the average CO widths of both ultraluminous infrared galaxies (300+/-90 km/s) and Palomar-Green QSOs (260+/-160 km/s), and thus being indicative of massive host galaxies. The CO luminosities translate into molecular gas masses of ~ 0.4-7x10^9 M_sun, however, the 3-sigma CO upper limits for nondetections do not rule out a molecular gas mass as high as that of the Milky Way (~ 3x10^9 M_sun). Optical images of eight out of nine molecular gas-rich radio galaxies show evidence of close companions and/or tidal features. Finally, there is no obvious correlation between radio power and molecular gas mass. However, it is notable that only one F-R II galaxy out of 12 is detected in this CO survey; the remaining detections are of galaxies hosting F-R I and compact radio jets.

A. S. Evans; J. M. Mazzarella; J. A. Surace; D. T. Frayer; K. Iwasawa; D. B. Sanders



Selective detection of volatile aromatic compounds using a compact laser ionization detector with fast gas chromatography.  


We report results for a new gas chromatography detector that is comparatively sensitive and far more selective for aromatic compounds than the traditional photoionization detector. The detection means is multiphoton ionization at atmospheric pressure. The ionization source in these experiments is a diode-pumped passively Q-switched microchip laser operating at 266 nm. Experiments were conducted with the detector interfaced to a fast gas chromatograph. For <20 s elution time, limits of detection were <1 pg for toluene, ethylbenzene, xylenes, and isopropylbenzene; the limit of detection for benzene is approximately 10 pg. Detector response was linear over 5 orders of magnitude, including these low levels. Negligible signals were observed for nonaromatic ketones, aldehydes, ethers, and cycloalkanes at levels as high as 0.1 microg (10 mg/L concentration). Detector efficiency after fast GC separation was 0.002% when using a detector cell with a radius of 1.1 cm and a purge gas flow of 500 mL/min. The advantages of this detector are further illustrated by the fast GC analysis of fuel samples. PMID:15018571

Meyer, Melissa J; Schieffer, Gregg M; Moeker, Eric K; Brodersen, Jeremy J; Swenson, Orven F; Borgerding, Anthony J



Detection of explosive analytes using a fiber-based optical Fabry-Perot gas sensor  

NASA Astrophysics Data System (ADS)

We demonstrate the rapid detection of explosive vapors based on a fiber-based optical Fabry-Pérot (FP) gas sensor. The sensing probe of the FP sensor is composed of a thin metal layer and a vapor-sensitive polymer layer that are deposited sequentially on a cleaved fiber endface to form an FP cavity. The interference spectrum generated from the reflected light at the metal-polymer and polymer-air interfaces changes upon the absorption of gas analyte. By monitoring the interference shift, we are able to obtain quantitative and knetic information of the interaction between the analyte and the polymer layer. We further assemble the FP sensor with a short fused silica capillary into a sensor module, and employ it in a gas chromotgraphy (GC) system for selevtive rapid on-column detection. In this report, we specifically target 2, 4- dinitrotoluene (DNT) and 2, 4, 6-trinitrotoluene (TNT) for their obvious defense applications. This work could lead to a portable sensor capable of detecting low concentrations of DNT, TNT, and other explosive chemicals.

Liu, Jing; Howard, Daniel J.; Whiteside, Paul; Sun, Yuze; Almasri, Mahmoud; Frye-Mason, Greg; Thompson, Aaron; Ja, Shiou-jyh; Fan, Xudong



Prospects of Optical Single Atom Detection in Noble Gas Solids for Measurements of Rare Nuclear Reactions  

NASA Astrophysics Data System (ADS)

Optical detection of single atoms captured in solid noble gas matrices provides an alternative technique to study rare nuclear reactions relevant to nuclear astrophysics. I will describe the prospects of applying this approach for cross section measurements of the ^22Ne,,),25Mg reaction, which is the crucial neutron source for the weak s process inside of massive stars. Noble gas solids are a promising medium for the capture, detection, and manipulation of atoms and nuclear spins. They provide stable and chemically inert confinement for a wide variety of guest species. Because noble gas solids are transparent at optical wavelengths, the guest atoms can be probed using lasers. We have observed that ytterbium in solid neon exhibits intersystem crossing (ISC) which results in a strong green fluorescence (546 nm) under excitation with blue light (389 nm). Several groups have observed ISC in many other guest-host pairs, notably magnesium in krypton. Because of the large wavelength separation of the excitation light and fluorescence light, optical detection of individual embedded guest atoms is feasible. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

Singh, Jaideep; Bailey, Kevin G.; Lu, Zheng-Tian; Mueller, Peter; O'Connor, Thomas P.; Xu, Chen-Yu; Tang, Xiaodong



Research and Development of Non-Spectroscopic MEMS-Based Sensor Arrays for Targeted Gas Detection  

SciTech Connect

The ability to monitor the integrity of gas volumes is of interest to the stockpile surveillance community. Specifically, the leak detection of noble gases, at relevant concentration ranges and distinguished from other chemical species that may be simultaneously present, is particularly challenging. Aside from the laboratory-based method of gas chromatography-mass spectrometry (GC-MS), where samples may be collected by solid-phase microextraction (SPME) or cryofocusing, the other major approaches for gas-phase detection employ lasers typically operating in the mid-infrared wavelength region. While mass spectrometry can readily detect noble gases - the helium leak detector is an obvious example - laser-based methods such as infrared (IR) or Raman spectroscopy are completely insensitive to them as their monatomic nature precludes a non-zero dipole moment or changes in polarizability upon excitation. Therefore, noble gases can only be detected by one of two methods: (1) atomic emission spectroscopies which require the generation of plasmas through laser-induced breakdown, electrical arcing, or similar means; (2) non-spectroscopic methods which measure one or more physical properties (e.g., mass, thermal conductivity, density). In this report, we present our progress during Fiscal Year 2011 (FY11) in the research and development of a non-spectroscopic method for noble gas detection. During Fiscal Year 2010 (FY10), we demonstrated via proof-of-concept experiments that the combination of thermal conductivity detection (TCD) and coating-free damped resonance detection (CFDRD) using micro-electromechanical systems (MEMS) could provide selective sensing of these inert species. Since the MEMS-based TCD technology was directly adapted from a brassboard prototype commissioned by a previous chemical sensing project, FY11 efforts focused on advancing the state of the newer CFDRD method. This work, guided by observations previously reported in the open literature, has not only resulted in a substantially measureable increase in selectivity but has also revealed a potential method for mitigating or eliminating thermal drift that does not require a secondary reference sensor. The design of an apparatus to test this drift compensation scheme will be described. We will conclude this report with a discussion of planned efforts in Fiscal Year 2012 (FY12).

Loui, A; McCall, S K



Quantitation of dissolved gas content in emulsions and in blood using mass spectrometric detection  

PubMed Central

Quantitation of dissolved gases in blood or in other biological media is essential for understanding the dynamics of metabolic processes. Current detection techniques, while enabling rapid and convenient assessment of dissolved gases, provide only direct information on the partial pressure of gases dissolved in the aqueous fraction of the fluid. The more relevant quantity known as gas content, which refers to the total amount of the gas in all fractions of the sample, can be inferred from those partial pressures, but only indirectly through mathematical modeling. Here we describe a simple mass spectrometric technique for rapid and direct quantitation of gas content for a wide range of gases. The technique is based on a mass spectrometer detector that continuously monitors gases that are rapidly extracted from samples injected into a purge vessel. The accuracy and sample processing speed of the system is demonstrated with experiments that reproduce within minutes literature values for the solubility of various gases in water. The capability of the technique is further demonstrated through accurate determination of O2 content in a lipid emulsion and in whole blood, using as little as 20 ?L of sample. The approach to gas content quantitation described here should greatly expand the range of animals and conditions that may be used in studies of metabolic gas exchange, and facilitate the development of artificial oxygen carriers and resuscitation fluids. PMID:21497566

Grimley, Everett; Turner, Nicole; Newell, Clayton; Simpkins, Cuthbert; Rodriguez, Juan



An overview of micromachined platforms for thermal sensing and gas detection  

SciTech Connect

Micromachined hotplates, membranes, filaments, and cantilevers have all been used as platforms for thermal sensing and gas detection. Compared with conventional devices, micromachined sensors are characterized by low power consumption, high sensitivity, and fast response time. Much of these gains can be attributed to the size reductions achieved by micromachining. In addition, micromachining permits easy, yet precise tailoring of the heat transfer characteristics of these devices. By simple alterations in device geometry and materials used, the relative magnitudes of radiation, convection and conduction losses and Joule heat gains can be adjusted, and in this way device response can be optimized for specific applications. The free-standing design of micromachined platforms, for example, reduces heat conduction losses to the substrate, thereby making them attractive as low power, fast-response heaters suitable for a number of applications. However, while micromachining solves some of the heat transfer problems typical of conventionally produced devices, it introduces some of its own. These trade-offs will be discussed in the context of several micromachined thermal and gas sensors present in the literature. These include micromachined flow sensors, gas thermal conductivity sensors, pressure sensors, uncooled IR sensors, metal-oxide and catalytic/calorimetric gas sensors. Recent results obtained for a microbridge-based catalytic/calorimetric gas sensor will also be presented as a means of further illustrating the concepts of thermal design in micromachined sensors.

Manginell, R.P.; Smith, J.H.; Ricco, A.J.



Determination of acoustic speed for improving leak detection and location in gas pipelines  

NASA Astrophysics Data System (ADS)

The commonly used cross-correlation technique for leak location requires that the acoustic speed is known and invariable. In practice, the gas leakage-induced acoustic waves propagate along multiple paths including in-pipe gas and pipe wall, and the acoustic waves in different transmission paths exhibit different acoustic speeds and different dispersive behaviors, which bring a great challenge for leak detection and location in the gas pipelines. In this study, based on the vibration theory of cylindrical elastic thin shell, the wavenumber formulae in different transmission paths are derived to predict the acoustic speeds and the acoustical coupling between the in-pipe gas and the pipe wall is analyzed to determine the dominant transmission path. In addition, the velocity dispersions in the dominant transmission path are suppressed by selection of a characteristic frequency band of the gas leakage-induced acoustic waves. The theoretical predictions are verified in the experiment and the results show that the theoretical acoustic speed is slightly larger than the measured acoustic speed. Thus, the theoretical acoustic speed formula is modified considering the effect of the structural loss factor and consequently the location error using the modified acoustic speed is reduced by two times compared to that using the theoretical acoustic speed.

Li, Shuaiyong; Wen, Yumei; Li, Ping; Yang, Jin; Yang, Lili



Development of a detection sensor for lethal H2S gas.  


The gas which may be lethal to human body with short-term exposure in common industrial fields or workplaces in LAB may paralyze the olfactory sense and impose severe damages to central nervous system and lung. This study is concerned with the gas sensor which allows individuals to avoid the toxic gas that may be generated in the space with residues of organic wastes under 50 degrees C or above. This study investigates response and selectivity of the sensor to hydrogen sulfide gas with operating temperatures and catalysts. The thick-film semiconductor sensor for hydrogen sulfide gas detection was fabricated WO3/SnO2 prepared by sol-gel and precipitation methods. The nanosized SnO2 powder mixed with the various metal oxides (WO3, TiO2, and ZnO) and doped with transition metals (Au, Ru, Pd Ag and In). Particle sizes, specific surface areas and phases of sensor materials were investigated by SEM, BET and XRD analyses. The metal-WO3/SnO2 thick films were prepared by screen-printing method. The measured response to hydrogen sulfide gas is defined as the ratio (Ra/R,) of the resistance of WO3ISnO2 film in air to the resistance of WO3/SnO2 film in a hydrogen sulfide gas. It was shown that the highest response and selectivity of the sensor for hydrogen sulfide by doping with 1 wt% Ru and 10 wt% WO3 to SnO2 at the optimum operating temperature of 200 degrees C. PMID:22966558

Park, Young-Ho; Kim, Yong-Jae; Lee, Chang-Seop



Tunable photonic cavities for in-situ spectroscopic trace gas detection  


Compact tunable optical cavities are provided for in-situ NIR spectroscopy. MEMS-tunable VCSEL platforms represents a solid foundation for a new class of compact, sensitive and fiber compatible sensors for fieldable, real-time, multiplexed gas detection systems. Detection limits for gases with NIR cross-sections such as O.sub.2, CH.sub.4, CO.sub.x and NO.sub.x have been predicted to approximately span from 10.sup.ths to 10s of parts per million. Exemplary oxygen detection design and a process for 760 nm continuously tunable VCSELS is provided. This technology enables in-situ self-calibrating platforms with adaptive monitoring by exploiting Photonic FPGAs.

Bond, Tiziana; Cole, Garrett; Goddard, Lynford



Detection of a noble gas molecular ion, 36ArH+, in the Crab Nebula.  


Noble gas molecules have not hitherto been detected in space. From spectra obtained with the Herschel Space Observatory, we report the detection of emission in the 617.5- and 1234.6-gigahertz J = 1-0 and 2-1 rotational lines of (36)ArH(+) at several positions in the Crab Nebula, a supernova remnant known to contain both molecular hydrogen and regions of enhanced ionized argon emission. Argon-36 is believed to have originated from explosive nucleosynthesis in massive stars during core-collapse supernova events. Its detection in the Crab Nebula, the product of such a supernova event, confirms this expectation. The likely excitation mechanism for the observed (36)ArH(+) emission lines is electron collisions in partially ionized regions with electron densities of a few hundred per centimeter cubed. PMID:24337290

Barlow, M J; Swinyard, B M; Owen, P J; Cernicharo, J; Gomez, H L; Ivison, R J; Krause, O; Lim, T L; Matsuura, M; Miller, S; Olofsson, G; Polehampton, E T



Nonlinear Raman spectroscopy without tunable laser for sensitive gas detection in the atmosphere  

NASA Astrophysics Data System (ADS)

A new technique for photo-acoustic Raman spectroscopy (PARS) and coherent anti-Stokes Raman spectroscopy (CARS) is proposed and demonstrated for the detection of H 2 and CH 4 at atmospheric pressure. Conventionally, these types of nonlinear Raman spectroscopy require two lasers whose frequency difference is tuned to the Raman frequency. In the proposed scheme, only a pulsed Nd:YAG laser is used as a pumping source, and a Raman shifter filled with the same gas to be detected is combined. This allows automatic generation of the Raman-shifted radiation. In the case of CH 4, the measurement with the optimized scheme shows that detection limits up to 1 ppm for PARS and 15 ppm for CARS are achieved. The proposed PARS technique allows the measurement of the CH 4 concentration in the natural air. Although the sensitivity of CARS is lower than that of PARS, the signal to noise ratio (S/N) for higher concentrations is better.

Oki, Yuji; Kawada, Noriyuki; Abe, Yoshiteru; Maeda, Mitsuo



Terrestrial laser scanning for detection of landfill gas: a pilot study  

NASA Astrophysics Data System (ADS)

Methane built up in landfills as a result of breaking down of organic materials can be a renewable energy source if it is taken advantage of. The aim of research presented in this paper is to detect landfill gas (that contains methane) by means of terrestrial laser scanning. The hypothesis is that where no surface leakage has been reported, the landfill gas will expand or migrate. Therefore, it is possible to detect it through repeated scanning of the same area and comparison of Digital Terrain Models (DTMs) generated from the point clouds. Only the most significant movements, i.e. vertical, are of interest in this case. During September-November 2011, a small area at Forsbacka landfill in the vicinity of Gävle was scanned 10 times. Epoch-to-epoch comparisons of the resulting DTMs have shown two significant changes (-27 and +19 mm) in elevation of the surface, and it is not impossible that they are caused by migrating landfill gas. The method tested in this study is deemed to be rigorous and accurate for detecting small-scale swell-shrink behaviour of the ground surface (in our case a landfill surface). However, both data processing and interpretation of the results have been considerably complicated by presence of low vegetation (weeds) on the study site, which was dificult to filter away completely from the data. Based on our pilot study, we recommend that a larger area and a longer period of time are chosen to give basis for more grounded conclusions about presence of landfill gas.

Reshetyuk, Yuriy; Mårtensson, Stig-Göran



2-Methyl-2,4-pentanediol gas sensor properties of nano-SnO2 flat-type coplanar gas sensing arrays at low detection limit  

NASA Astrophysics Data System (ADS)

Nano-SnO2 flat-type coplanar 2-Methyl-2,4-pentanediol (MPD) gas sensor arrays were fabricated by a screen-printing technique based on nano-SnO2 powders prepared by a hydrothermal method. The results show that the fabricated gas sensor arrays have good MPD gas sensing characteristics, such as good selectivity and response-recovery characteristics. Especially, they can be used for detecting the concentration of MPD gas as low as 1 ppm which is much lower than the legal concentration of 20 ppm or 25 ppm. The good sensing properties indicate that the SnO2 gas sensor arrays have great potential for on-line or portable monitoring of MPD gas in practical environments.

Zhu, Chao; Huang, Kaijin; Yuan, Fangli; Xie, Changsheng



Issues Involving The OSI Concept of Operation For Noble Gas Radionuclide Detection  

SciTech Connect

The development of a technically sound protocol for detecting the subsurface release of noble gas radionuclides is critical to the successful operation of an on site inspection (OSI) under the CTBT and has broad ramifications for all aspects of the OSI regime including the setting of specifications for both sampling and analysis equipment used during an OSI. With NA-24 support, we are investigating a variety of issues and concerns that have significant bearing on policy development and technical guidance regarding the detection of noble gases and the creation of a technically justifiable OSI concept of operation. The work at LLNL focuses on optimizing the ability to capture radioactive noble gases subject to the constraints of possible OSI scenarios. This focus results from recognizing the difficulty of detecting gas releases in geologic environments - a lesson we learned previously from the LLNL Non-Proliferation Experiment (NPE). Evaluation of a number of important noble gas detection issues, potentially affecting OSI policy, has awaited the US re-engagement with the OSI technical community. Thus, there have been numerous issues to address during the past 18 months. Most of our evaluations of a sampling or transport issue necessarily involve computer simulations. This is partly due to the lack of OSI-relevant field data, such as that provided by the NPE, and partly a result of the ability of LLNL computer-based models to test a range of geologic and atmospheric scenarios far beyond what could ever be studied in the field making this approach very highly cost effective. We review some highlights of the transport and sampling issues we have investigated during the past year. We complete the discussion of these issues with a description of a preliminary design for subsurface sampling that is intended to be a practical solution to most if not all the challenges addressed here.

Carrigan, C R; Sun, Y



Correlated column micro gas chromatography instrumentation for the vapor detection of contraband drugs in cargo containers  

NASA Astrophysics Data System (ADS)

We have developed an instrument based on Micro Gas Chromatography ((mu) GC) for rapid, handheld detection of vapor signatures from contraband drugs in cargo containers. For this application, a key requirement is the ability to distinguish the vapor signatures of contraband drugs against the highly variable chemical backgrounds encountered in cargo containers. To achieve this, we split the sample and run it simultaneously on two (mu) GCs with different stationary phases using correlated column chromatography. This effectively expands `detection space' and greatly enhances the chemical selectively. As part of this effort, we have also developed an extensive correlated chromatography database of chemical vapor signatures for both contraband drugs and representative backgrounds obtained by sampling incoming cargo containers under the supervision of U.S. Customs inspectors. Our experience shows that significant vapor buildup occurs in these containers resulting in strong and variable chemical backgrounds. Typical GC signatures observed have 10 - 20 strong components with a variable number of weaker components. The signatures reflect the very large variation in the contents and extent of packing of cargo containers, and show that vapor-based chemical detectors will require a large dynamic range to be effective. Gas chromatography is well suited for this. Furthermore it appears that a correlated (mu) GC instrument can provide rapid, handheld detection which fits into existing operational scenarios for the inspection of cargo containers for contraband.

Holland, Paul M.; Mustacich, Robert V.; Everson, James F.; Foreman, William; Leone, Michael; Sanders, Ann H.; Naumann, Walter J.



Nanofiber-net-binary structured membranes for highly sensitive detection of trace HCl gas  

NASA Astrophysics Data System (ADS)

This work describes the detection of trace hydrogen chloride (HCl) gas through analyses of the resonance frequency signal from quartz crystal microbalance (QCM) sensors coated with polyaniline (PANI) functionalized polyamide 6 (PA 6) (PANI-PA 6) nanofiber-net-binary (NNB) structured membranes. The PA 6 NNB substrate comprising nanofibers and spider-web-like nano-nets fabricated by a versatile electro-spinning/netting (ESN) process offered an ideal interface for the uniform PANI functionalization and enhanced sensing performance. Benefiting from the large specific surface area, high porosity, and strong adhesive force to the QCM electrode of the PANI-PA 6 NNB membranes, the developed HCl-selective sensors exhibited a rapid response, good reproducibility and stability, and low detection limit (7 ppb) at room temperature. Additionally, the PANI-PA 6 NNB sensing membranes presented visible color changes upon cycled exposure to HCl and ammonia, suggesting their potential application in the development of colorimetric sensors. The PANI-PA 6 NNB coated QCM sensors are considered to be a promising candidate for trace HCl gas detection in practical applications.

Wang, Xianfeng; Wang, Jialin; Si, Yang; Ding, Bin; Yu, Jianyong; Sun, Gang; Luo, Wenjing; Zheng, Gang



A Cost Effective Multi-Spectral Scanner for Natural Gas Detection  

SciTech Connect

The objective of this project is to design, fabricate and demonstrate a cost effective, multi-spectral scanner for natural gas leak detection in transmission and distribution pipelines. During the first year of the project, a laboratory version of the multi-spectral scanner was designed, fabricated, and tested at EnUrga Inc. The multi-spectral scanner was also evaluated using a blind Department of Energy study at the Rocky Mountain Oilfield Testing Center. The performance of the scanner was inconsistent during the blind study. However, most of the leaks were outside the view of the multi-spectral scanner that was developed during the first year of the project. Therefore, a definite evaluation of the capability of the scanner was not obtained. Despite the results, sufficient number of plumes was detected fully confirming the feasibility of the multi-spectral scanner. During the second year, the optical design of the scanner was changed to improve the sensitivity of the system. Laboratory tests show that the system can reliably detect small leaks (20 SCFH) at 30 to 50 feet. A prototype scanner was built and evaluated during the second year of the project. Only laboratory evaluations were completed during the second year. The laboratory evaluations show the feasibility of using the scanner to determine natural gas pipeline leaks. Further field evaluations and optimization of the scanner are required before commercialization of the scanner can be initiated.

Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan; Seonghyeon Park



Nanofiber-net-binary structured membranes for highly sensitive detection of trace HCl gas.  


This work describes the detection of trace hydrogen chloride (HCl) gas through analyses of the resonance frequency signal from quartz crystal microbalance (QCM) sensors coated with polyaniline (PANI) functionalized polyamide 6 (PA 6) (PANI-PA 6) nanofiber-net-binary (NNB) structured membranes. The PA 6 NNB substrate comprising nanofibers and spider-web-like nano-nets fabricated by a versatile electro-spinning/netting (ESN) process offered an ideal interface for the uniform PANI functionalization and enhanced sensing performance. Benefiting from the large specific surface area, high porosity, and strong adhesive force to the QCM electrode of the PANI-PA 6 NNB membranes, the developed HCl-selective sensors exhibited a rapid response, good reproducibility and stability, and low detection limit (7 ppb) at room temperature. Additionally, the PANI-PA 6 NNB sensing membranes presented visible color changes upon cycled exposure to HCl and ammonia, suggesting their potential application in the development of colorimetric sensors. The PANI-PA 6 NNB coated QCM sensors are considered to be a promising candidate for trace HCl gas detection in practical applications. PMID:23108331

Wang, Xianfeng; Wang, Jialin; Si, Yang; Ding, Bin; Yu, Jianyong; Sun, Gang; Luo, Wenjing; Zheng, Gang



Development of gprs-based leak detection system for pipe pushing crossing part of nature gas pipeline  

Microsoft Academic Search

There would be a sealed space, called culvert box, between the nature gas pipeline and the concrete pipe when the nature gas pipeline crossing highways, railways and rivers using the trenchless pipe pushing technology. To deal with the problem of leak detection and monitoring for these culvert boxes, which were located in the field and scattered, a GPRS-based (GPRS: general

Fujun Liu; Shuai Kong; Zhangwei Ling; Mulin Zheng; Yueqiang Qian



Inflammable Gas Mixture Detection with a Single Catalytic Sensor Based on the Electric Field Effect  

PubMed Central

This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%. PMID:24717635

Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng



Gas-CT cisternography for detection of small acoustic nerve tumors  

SciTech Connect

Gas-CT cisternography is a simple and accurate procedure for detection of small acoustic nerve tumors. Review of one of the largest series in a single institution found that 98% of the studies clearly showed the presence or absence of tumors. The diagnostic pitfalls of the small number of studies in which significant errors were made, or could have been made, are discussed. It is concluded that certain situations appear to call for extra caution: (a) when the filling defect does not show a convex surface, (b) when the amount of cisternal gas is marginal, and (c) when the canal is small. In such situations careful attention to details and healthy skepticism may avert potential errors.

Solti-Bohman, L.G.; Magaram, D.L.; Lo, W.W.M.; Wade, C.T.; Witten, R.M.; Shimizu, F.H.; McMonigle, E.M.; Raja Rao, A.K.



FTIR gas analysis with improved sensitivity and selectivity for CWA and TIC detection  

NASA Astrophysics Data System (ADS)

This presentation describes the use of an FTIR (Fourier Transform Infrared)-based spectrometer designed to continuously monitor ambient air for the presence of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs). The necessity of a reliable system capable of quickly and accurately detecting very low levels of CWAs and TICs while simultaneously retaining a negligible false alarm rate will be explored. Technological advancements in FTIR sensing have reduced noise while increasing selectivity and speed of detection. These novel analyzer design characteristics are discussed in detail and descriptions are provided which show how optical throughput, gas cell form factor, and detector response are optimized. The hardware and algorithms described here will explain why this FTIR system is very effective for the simultaneous detection and speciation of a wide variety of toxic compounds at ppb concentrations. Analytical test data will be reviewed demonstrating the system's sensitivity to and selectivity for specific CWAs and TICs; this will include recent data acquired as part of the DHS ARFCAM (Autonomous Rapid Facility Chemical Agent Monitor) project. These results include analyses of the data from live agent testing for the determination of CWA detection limits, immunity to interferences, detection times, residual noise analysis and false alarm rates. Sensing systems such as this are critical for effective chemical hazard identification which is directly relevant to the CBRNE community.

Phillips, Charles M.; Tan, Huwei



Fission signal detection using helium-4 gas fast neutron scintillation detectors  

NASA Astrophysics Data System (ADS)

We demonstrate the unambiguous detection of the fission neutron signal produced in natural uranium during active neutron interrogation using a deuterium-deuterium fusion neutron generator and a high pressure 4He gas fast neutron scintillation detector. The energy deposition by individual neutrons is quantified, and energy discrimination is used to differentiate the induced fission neutrons from the mono-energetic interrogation neutrons. The detector can discriminate between different incident neutron energies using pulse height discrimination of the slow scintillation component of the elastic scattering interaction between a neutron and the 4He atom. Energy histograms resulting from this data show the buildup of a detected fission neutron signal at higher energies. The detector is shown here to detect a unique fission neutron signal from a natural uranium sample during active interrogation with a (d, d) neutron generator. This signal path has a direct application to the detection of shielded nuclear material in cargo and air containers. It allows for continuous interrogation and detection while greatly minimizing the potential for false alarms.

Lewis, J. M.; Kelley, R. P.; Murer, D.; Jordan, K. A.



Fission signal detection using helium-4 gas fast neutron scintillation detectors  

SciTech Connect

We demonstrate the unambiguous detection of the fission neutron signal produced in natural uranium during active neutron interrogation using a deuterium-deuterium fusion neutron generator and a high pressure {sup 4}He gas fast neutron scintillation detector. The energy deposition by individual neutrons is quantified, and energy discrimination is used to differentiate the induced fission neutrons from the mono-energetic interrogation neutrons. The detector can discriminate between different incident neutron energies using pulse height discrimination of the slow scintillation component of the elastic scattering interaction between a neutron and the {sup 4}He atom. Energy histograms resulting from this data show the buildup of a detected fission neutron signal at higher energies. The detector is shown here to detect a unique fission neutron signal from a natural uranium sample during active interrogation with a (d, d) neutron generator. This signal path has a direct application to the detection of shielded nuclear material in cargo and air containers. It allows for continuous interrogation and detection while greatly minimizing the potential for false alarms.

Lewis, J. M., E-mail:; Kelley, R. P.; Jordan, K. A. [Nuclear Engineering Program, University of Florida, Gainesville, Florida 32611 (United States); Murer, D. [Arktis Radiation Detectors Ltd., 8045 Zurich (Switzerland)



Gas analyzer for continuous monitoring of trace level methanethiol by microchannel collection and fluorescence detection.  


The highly odorous compound methanethiol, CH3SH, is commonly produced in biodegradation of biomass and industrial processes, and is classed as 2000 times more odorous than NH3. However, there is no simple analytical method for detecting low parts-per-billion in volume ratio (ppbv) levels of CH3SH. In this study, a micro gas analysis system (?GAS) was developed for continuous or near real time measurement of CH3SH at ppbv levels. In addition to a commercial fluorescence detector, a miniature high sensitivity fluorescence detector was developed using a novel micro-photomultiplier tube device. CH3SH was collected by absorption into an alkaline solution in a honeycomb-patterned microchannel scrubber and then mixed with the fluorescent reagent, 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F). Gaseous CH3SH was measured without serious interference from other sulfur compounds or amines. The limits of detection were 0.2ppbv with the commercial detector and 0.3ppbv with the miniature detector. CH3SH produced from a pulping process was monitored with the ?GAS system and the data agreed well with those obtained by collection with a silica gel tube followed by thermal desorption-gas chromatography-mass spectrometry. The portable system with the miniature fluorescence detector was used to monitor CH3SH levels in near-real time in a stockyard and it was shown that the major odor component, CH3SH, presented and its concentration varied dynamically with time. PMID:25109855

Toda, Kei; Kuwahara, Haruka; Kajiwara, Hidetaka; Hirota, Kazutoshi; Ohira, Shin-Ichi



Fire Detection Using tin Oxide Gas Sensors Installed in an Indoor Space  

NASA Astrophysics Data System (ADS)

Many lives and facilities were lost by fire. Especially, there are many damages to elderly, toddlers and babies. In Japan, number of deaths over 65 years old reached to 53% in 2004. Number of over 81 years olds went to 20%. It takes for the elderly person more time to sense fire and also to evacuate to safe places. Although it is important to prevent the fire, it also needs to inform the fire breaking as early as possible. Human sense decreases with age and it is difficult to perceive the fire at an early stage. It is desired to develop a higher sensitive element for fire and its system which can detect fire at an early stage. In this experiment, tin oxide gas sensors were adopted to detect a smoldering fire at the early stage. Most common case of fire is the smoldering fire. The reliability of the sensor is higher and it is adopted in a gas alarm detector. The sensor can also detect slight amount of odor molecule. In our previous experiment, it became obvious that it was better to install the sensor to the ceiling to detect odor components generating from smoldering fire. Therefore, five sensors were installed in the ceiling away from each other and the method to detect the fire was examined. As a result, a characteristic was newly derived by adding the sensor outputs for one minute. The sensor output was input every 0.1s. The characteristic is called as the integrated characteristic. After that, the differential characteristic was derived using the integrated characteristic. The fire was determined using the differential characteristics. The materials causing a smoldering fire were woodchip, wallpaper and carpet as subjects. The system could detect the fire in several minutes for whole materials. The sensor is effective to detect the smoldering fire at an early stage. It is necessary to detect a cigarette smoke to distinguish as non fire. In this study, the discrimination was also examined using a quadratic function (ax2+b). The coefficients a and b were effective to identify smoldering fire and cigarette smoke. Principal component analysis for the arrival speed S which meant a kind of odor-speed was also useful to distinguish fire from non fire.

Shibata, Shin-Ichi; Higashino, Tsubasa; Sawada, Ayako; Oyabu, Takashi; Takei, Yoshinori; Nanto, Hidehito; Toko, Kiyoshi


Lyman Alpha Mapping Project (LAMP) Detections of LCROSS Impact Plume Gas  

NASA Astrophysics Data System (ADS)

The Lyman Alpha Mapping Project (LAMP) is an ultraviolet (UV) spectrograph on the Lunar Reconnaissance Orbiter (LRO) that is designed to map the lunar albedo at far-UV wavelengths. LAMP's spectral range of 57.5 nm to 196.5 nm includes emission line features from several known and expected lunar atmosphere constituents, including resonantly scattered Lyman-alpha (121.57 nm) emissions from hydrogen atoms and argon atom emissions at 104.82 nm and 106.67 nm. The LCROSS impact on 9 October 2009 elevated and exposed water ice and other volatiles trapped near the lunar surface (Colaprete et al., submitted, 2010). Observations with LRO/LAMP detected enhancements of volatile species in the plume shortly after impact (Gladstone et al., submitted, 2009). The plume of rapidly expanding gas includes molecular hydrogen gas seen by sunlit fluorescence. Resonantly scattered emissions from atomic Hg, Mg, and Ca in sunlight are also likely detected in a feature near 185 nm. The molecular hydrogen content within permanently shadowed regions (PSRs) is higher than possible through dissociation of water alone, which indicates that trapped hydrogen gas likely contributes to the hydrogen content of the PSRs in addition to the water detected there. The concentration of mercury in PSRs has implications for future exploration and in situ resource utilization in these regions. This investigation addresses how water and other volatiles arrive (or form) at the lunar surface, are transported through the lunar atmosphere, and are deposited within PSRs (or elsewhere), which is closely related to LAMP's primary objectives.

Retherford, Kurt; Gladstone, Randy; Stern, Alan; Hurley, Dana; Feldman, Paul; Pryor, Wayne; Hendrix, Amanda; Goldstein, David; Summy, Dustin



Intelligent hypertext manual development for the Space Shuttle hazardous gas detection system  

NASA Technical Reports Server (NTRS)

This research is designed to utilize artificial intelligence (AI) technology to increase the efficiency of personnel involved with monitoring the space shuttle hazardous gas detection systems at the Marshall Space Flight Center. The objective is to create a computerized service manual in the form of a hypertext and expert system which stores experts' knowledge and experience. The resulting Intelligent Manual will assist the user in interpreting data timely, in identifying possible faults, in locating the applicable documentation efficiently, in training inexperienced personnel effectively, and updating the manual frequently as required.

Lo, Ching F.; Hoyt, W. Andes



Mobile spectroscopic system for trace gas detection using a tunable mid-IR laser  

NASA Astrophysics Data System (ADS)

We describe a mobile spectroscopic system for trace gas analysis based on the open path differential absorption spectrometer and the photoacoustic spectrometer. The first method allows long distance measurements (up to a few kilometers) while the second one provides local in situ detection of pollutants. The open path system is based on the nanosecond (f =10Hz, ? ?5ns) lamp pumped Nd:YAG laser and a tunable two cascade optical parametric generator operating in the 5-12?m spectral region. This source was mounted into the lidar setup based on the coaxial transmitter/receiver. The photoacoustic system was constructed using the same laser as well as a nonresonant photoacoustic cell.

Vai?ikauskas, V.; Kau?ikas, M.; Švedas, V.; Kuprionis, Z.



Electrically Detected Magnetic Resonance of Neutral Donors Interacting with a Two-Dimensional Electron Gas  

SciTech Connect

We have measured the electrically detected magnetic resonance of donor-doped silicon field-effect transistors in resonant X- (9.7 GHz) and W-band (94 GHz) microwave cavities. The two-dimensional electron gas (2DEG) resonance signal increases by two orders of magnitude from X- to W-band, while the donor resonance signals are enhanced by over one order of magnitude. Bolometric effects and spin-dependent scattering are inconsistent with the observations. We propose that polarization transfer from the donor to the 2DEG is the main mechanism giving rise to the spin resonance signals.

Lo, C. C.; Lang, V.; George, R. E.; Morton, J. J. L.; Tyryshkin, A. M.; Lyon, A.; Bokor, J.; Schenkel, T.



Miniaturized Gas Correlation Radiometer for the Detection of Trace Gases in the Martian Atmosphere  

NASA Technical Reports Server (NTRS)

We present a miniaturized and simplified version of a gas correlation radiometer (GCR) capable of simultaneously mapping multiple trace gases and identifying active regions on the Mars surface. Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Reduction of the size and mass of the GCR was achieved by implementing compact, light-weight 1 mm inner diameter hollow-core optical fibers (hollow waveguides) as the gas correlation cells. In a comparison with an Earth orbiting CO2 GCR instrument, exchanging the 10 m multipass cells with hollow waveguide gas correlation cells of equivalent path length reduces the mass from approximately 150 kg to approximately 0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately 1 meter in diameter by 0.05 m in height (mass and volume reductions of greater than 99%). A unique feature of this instrument is its stackable module design, with a single module for each trace gas. Each of the modules is self-contained, and fundamentally identical; differing by the bandpass filter wavelength range and gas mixtures inside the hollow-waveguide absorption cells. The current configuration contains four stacked modules for simultaneous measurements of methane (CH4), formaldehyde (H2CO), water vapor (H2O), and deuterated water vapor (HDO) but could easily be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance. Preliminary results indicate that a 1 ppb detection limit is possible for both formaldehyde and methane with one second of averaging. Using non-optimized components, we have demonstrated an instrument sensitivity equivalent to approximately 30 ppb for formaldehyde, and approximately 500 ppb for methane. We expect custom bandpass filters and 6 m long waveguides to significantly improve these promising results. Ongoing testing is being conducted on water vapor and deuterated water vapor.

Melroy, Hilary R.; Wilson, Emily L.; Georgieva, Elena



Detection of pristine gas two billion years after the Big Bang.  


In the current cosmological model, only the three lightest elements were created in the first few minutes after the Big Bang; all other elements were produced later in stars. To date, however, heavy elements have been observed in all astrophysical environments. We report the detection of two gas clouds with no discernible elements heavier than hydrogen. These systems exhibit the lowest heavy-element abundance in the early universe, and thus are potential fuel for the most metal-poor halo stars. The detection of deuterium in one system at the level predicted by primordial nucleosynthesis provides a direct confirmation of the standard cosmological model. The composition of these clouds further implies that the transport of heavy elements from galaxies to their surroundings is highly inhomogeneous. PMID:22075722

Fumagalli, Michele; O'Meara, John M; Prochaska, J Xavier



Identification of volatiles by headspace gas chromatography with simultaneous flame ionization and mass spectrometric detection.  


Volatiles are frequently abused as inhalants. The methods used for identification are generally nonspecific if analyzed concurrently with ethanol or require an additional analytical procedure that employs mass spectrometry. A previously published technique utilizing a capillary flow technology splitter to simultaneously quantitate and confirm ethyl alcohol by flame ionization and mass spectrometric detection after headspace sampling and gas chromatographic separation was evaluated for the detection of inhalants. Methanol, isopropanol, acetone, acetaldehyde, toluene, methyl ethyl ketone, isoamyl alcohol, isobutyl alcohol, n-butyl alcohol, 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane (Norflurane, HFC-134a), chloroethane, trichlorofluoromethane (Freon®-11), dichlorodifluoromethane (Freon®-12), dichlorofluoromethane (Freon®-21), chlorodifluoromethane (Freon®-22) and 1,2-dichlorotetrafluoroethane (Freon®-114) were validated for qualitative identification by this method. The validation for qualitative identification included evaluation of matrix effects, sensitivity, carryover, specificity, repeatability and ruggedness/robustness. PMID:24005155

Tiscione, Nicholas B; Yeatman, Dustin Tate; Shan, Xiaoqin; Kahl, Joseph H



Determination of clemastine in human plasma by gas chromatography with nitrogen-phosphorus detection.  


A method for the quantitative determination of clemastine in human plasma has been developed and validated. The assay uses gas chromatography with nitrogen-phosphorus detection and a HP-1 capillary column (25 mx0.22 mm, film thickness 0.33 mm) coated with dimethylpolysiloxane. Clemastine (with orphenadrine as internal standard) was isolated from human plasma using liquid-liquid extraction. A linear relationship was observed between 0.1 and 12.8 ng/ml using the peak area ratio of clemastine to orphenadrine with a correlation coefficient greater than 0.99 (the detection limit for clemastine was 0.06 ng/ml). The intra- and inter-day coefficients of variation were less than 11%. The developed method was used for the analysis of plasma samples from healthy volunteers (n = 19) to examine the pharmacokinetics of the antihistamine clemastine after single and multiple oral doses of clemastine fumarate. PMID:10985579

Davydova, N N; Yasuda, S U; Woosley, R L; Wainer, I W



Detection of gas phase combustion products and pollutants via intra-cavity Raman spectroscopy  

SciTech Connect

An intra-cavity Raman spectrometer was employed in the detection of various gas phase pollutants and combustion products. Using the spectrometer, data were collected for sulfur dioxide, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, oxygen, and total hydrocarbons in both noncombustion and combustion environments. Based on the data collected, instrument detection limits were established and calibration curves were constructed. It was found that the intra-cavity Raman system produced a linear calibration curve for sulfur dioxide, nitrogen dioxide, and carbon monoxide in a noncombustion environment, and had a linear response for sulfur dioxide and carbon monoxide during combustion. Various combustion scenarios were also set up to establish combustion efficiency of a lab scale burner system based on oxygen, carbon monoxide, carbon dioxide, and hydrocarbon data.

Underhill-Shanks, K.S.; Hudson, M.K. [Univ. of Arkansas, Little Rock, AR (United States)



Procedure for detecting and confirming pentobarbital residues in dog food by gas chromatography/mass spectrometry.  


The method described detects and confirms presence of pentobarbital residues in dry, extruded feeds at concentrations of 5-20 ppb. Dried feed is ground to a uniform powder and shaken overnight in methanol. A portion of the methanolic extract is evaporated, and the residue is reconstituted in phosphate-buffered saline. The aqueous extract is cleaned with a solid-phase extraction cartridge designed to extract barbiturate residues from biological matrixes. Dimethyl sulfoxide, tetramethylammonium hydroxide, and iodomethane are added to derivatize pentobarbital, 1,3-Dimethyl-pentobarbital is then acidified with dilute hydrochloric acid and extracted with isooctane. The organic layer is transferred and evaporated under a stream of nitrogen. The residue is reconstituted in a small volume of ethyl acetate for analysis by gas chromatography/mass spectrometry. The limit of detection is approximately 0.7 ppb. The method was validated with pentobarbital-fortified feed samples containing high concentrations of meat and bone meal. PMID:9549069

Adam, L A; Reeves, V B



Leakage detection and location in gas pipelines through an LPV identification approach  

NASA Astrophysics Data System (ADS)

A new approach to gas leakage detection in high pressure distribution networks is proposed, where two leakage detectors are modelled as a linear parameter varying (LPV) system whose scheduling signals are, respectively, intake and offtake pressures. Running the two detectors simultaneously allows for leakage location. First, the pipeline is identified from operational data, supplied by REN-Gasodutos and using an LPV systems identification algorithm proposed in [1]. Each leakage detector uses two Kalman filters where the fault is viewed as an augmented state. The first filter estimates the flow using a calculated scheduling signal, assuming that there is no leakage. Therefore it works as a reference. The second one uses a measured scheduling signal and the augmented state is compared with the reference value. Whenever there is a significant difference, a leakage is detected. The effectiveness of this method is illustrated with an example where a mixture of real and simulated data is used.

Lopes dos Santos, P.; Azevedo-Perdicoúlis, T.-P.; Jank, G.; Ramos, J. A.; Martins de Carvalho, J. L.




SciTech Connect

We present 230 realizations of a numerical model of planet formation in systems without gas giants. These represent a scenario in which protoplanets grow in a region of a circumstellar disk where water ice condenses and the surface density of solids is enhanced (the 'ice line'), but fail to accrete massive gas envelopes before the gaseous disk is dispersed. Each simulation consists of a small number of gravitationally interacting oligarchs (protoplanets) and a much larger number of small bodies that represent the natal disk of planetesimals. Time zero of each simulation represents the epoch at which the gas has disappeared, and the dynamics are integrated for 5 billion years (Gyr). We investigate systems with varying initial number of oligarchs, oligarch spacing, location of the ice line, total mass in the ice line, and oligarch mean density. Systems become chaotic in {approx}1 Myr but settle into stable configurations in 10-100 Myr. We find: (1) runs consistently produce a 5-9 M {sub +} planet at a semimajor axis of 0.25-0.6 times the position of the ice line, (2) the distribution of planets' orbital eccentricities is distinct from, and skewed toward lower values than the observed distribution of (giant) exoplanet orbits, (3) Inner systems of two dominant planets (e.g., Earth and Venus) are not stable or do not form because of the gravitational influence of the innermost icy planet. The planets predicted by our model are unlikely to be detected by current Doppler observations. Microlensing is currently sensitive to the most massive planets found in our simulations, and may have already found several analogs. A scenario where up to 60% of stars host systems such as those we simulate is consistent with all the available data. We predict that, if this scenario holds, the NASA Kepler spacecraft will detect about 120 planets by two or more transits over the course of its 3.5 yr mission. Furthermore, we predict detectable transit timing variations exceeding 20 minutes due to the presence of additional outer planets. Future microlensing surveys will detect {approx}130 analogs over a 5 yr survey, including a handful of multiple-planet systems. Finally, the Space Interferometry Mission (SIM-Lite) should be capable of detecting 96% of the innermost icy planets over the course of a 5 yr mission.

Mann, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Gaidos, Eric [Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822 (United States); Gaudi, B. Scott [Department of Astronomy, Ohio State University, 140 W. 18th Avenue, Columbus, OH 43120 (United States)



Constraints from the Detection of Cosmic Topology on the Generalized Chaplygin Gas  

E-print Network

Despite our present-day inability to predict the topology of the universe one may expect that we should be able to detect it in the near future, given the increasing accuracy in the astro-cosmological observations. Motivated by this, we examine to what extent a possible detection of a non-trivial topology of a low curvature (Omega_0 ~ 1) universe, suggested by a diverse set of current observations, may be used to place constraints on the matter content of the universe, focusing our attention on the generalized Chaplgygin gas (GCG) model, which unifies dark matter and dark energy in a single matter component. We show that besides constraining the GCG free parameters, the detection of a nontrivial topology also allows to set bounds on the total density parameter Omega_0. We also study the combination of the bounds from the topology detection with the limits that arise from current data on 194 SNIa, and show that the determination of a given nontrivial topology sets complementary bounds on the GCG parameters (and on Omega_0) to those obtained from the SNIa data.

M. Makler; B. Mota; M. J. Reboucas



Detection of Greenhouse Gas Precursors from Diesel Engines Using Electrochemical and Photoacoustic Sensors  

PubMed Central

Atmospheric pollution is one of the worst threats to modern society. The consequences derived from different forms of atmospheric pollution vary from the local to the global scale, with deep impacts on climate, environment and human health. Several gaseous pollutants, even when present in trace concentrations, play a fundamental role in important processes that occur in atmosphere. Phenomena such as global warming, photochemical smog formation, acid rain and the depletion of the stratospheric ozone layer are strongly related to the increased concentration of certain gaseous species in the atmosphere. The transport sector significantly produces atmospheric pollution, mainly when diesel oil is used as fuel. Therefore, new methodologies based on selective and sensitive gas detection schemes must be developed in order to detect and monitor pollutant gases from this source. In this work, CO2 Laser Photoacoustic Spectroscopy was used to evaluate ethylene emissions and electrochemical analyzers were used to evaluate the emissions of CO, NOx and SO2 from the exhaust of diesel powered vehicles (rural diesel with 5% of biodiesel, in this paper called only diesel) at different engine rotation speeds. Concentrations in the range 6 to 45 ppmV for ethylene, 109 to 1,231 ppmV for carbon monoxide, 75 to 868 ppmV for nitrogen oxides and 3 to 354 ppmV for sulfur dioxide were obtained. The results indicate that the detection techniques used were sufficiently selective and sensitive to detect the gaseous species mentioned above in the ppmV range. PMID:22163437

Mothé, Geórgia; Castro, Maria; Sthel, Marcelo; Lima, Guilherme; Brasil, Laisa; Campos, Layse; Rocha, Aline; Vargas, Helion





... swallow and the breakdown of undigested food by bacteria in the large intestine. Certain foods may cause gas. Foods that produce gas in one person may not cause gas in another. You can reduce the amount of gas you have by Drinking lots of water and non-fizzy drinks Eating more slowly so ...


Development of an Optical Gas Leak Sensor for Detecting Ethylene, Dimethyl Ether and Methane  

PubMed Central

In this paper, we present an approach to develop an optical gas leak sensor that can be used to measure ethylene, dimethyl ether, and methane. The sensor is designed based on the principles of IR absorption spectrum detection, and comprises two crossed elliptical surfaces with a folded reflection-type optical path. We first analyze the optical path and the use of this structure to design a miniature gas sensor. The proposed sensor includes two detectors (one to acquire the reference signal and the other for the response signal), the light source, and the filter, all of which are integrated in a miniature gold-plated chamber. We also designed a signal detection device to extract the sensor signal and a microprocessor to calculate and control the entire process. The produced sensor prototype had an accuracy of ±0.05%. Experiments which simulate the transportation of hazardous chemicals demonstrated that the developed sensor exhibited a good dynamic response and adequately met technical requirements. PMID:23539025

Tan, Qiulin; Pei, Xiangdong; Zhu, Simin; Sun, Dong; Liu, Jun; Xue, Chenyang; Liang, Ting; Zhang, Wendong; Xiong, Jijun



LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Remote laser detection of natural gas leakages from pipelines  

NASA Astrophysics Data System (ADS)

A differential absorption lidar based on a tunable TEA CO2 laser emitting at 42 lines of the 'hot' 0111 — 1110 band in the range from 10.9 to 11.4 ?m is developed for detecting natural gas leakages from oil pipelines by measuring the ethane content in the atmosphere. The ethane detection sensitivity is 0.9 ppm km. The presence of methane does not distort the measurement results. The developed lidar can detect the natural gas leakage from kilometre heights at the flying velocities up to 200 km h-1 and a probe pulse repetition rate of 5 Hz.

Petukhov, V. O.; Gorobets, V. A.; Andreev, Yu M.; Lanskii, G. V.




SciTech Connect

Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. This six-month technical report summarizes the progress for each of the proposed tasks, discusses project concerns, and outlines near-term goals. Ophir has completed a data survey of two major natural gas pipeline companies on the design requirements for an airborne, optical remote sensor. The results of this survey are disclosed in this report. A substantial amount of time was spent on modeling the expected optical signal at the receiver at different absorption wavelengths, and determining the impact of noise sources such as solar background, signal shot noise, and electronic noise on methane and ethane gas detection. Based upon the signal to noise modeling and industry input, Ophir finalized the design requirements for the airborne sensor, and released the critical sensor light source design requirements to qualified vendors. Responses from the vendors indicated that the light source was not commercially available, and will require a research and development effort to produce. Three vendors have responded positively with proposed design solutions. Ophir has decided to conduct short path optical laboratory experiments to verify the existence of methane and absorption at the specified wavelength, prior to proceeding with the light source selection. Techniques to eliminate common mode noise were also evaluated during the laboratory tests. Finally, Ophir has included a summary of the potential concerns for project success and has established future goals.

Jerry Myers



Application of gas-coupled laser acoustic detection to gelatins and underwater sensing  

NASA Astrophysics Data System (ADS)

Gas-coupled Laser Acoustic Detection (GCLAD) has been used as a method to sense ultrasound waves in materials without contact of the material surface. To sense the waveform, a laser beam is directed parallel to the material surface and displaced or deflected when the radiated waveform traverses the beam. We present recent tests that demonstrate the potential of using this technique for detecting ultrasound in gelatin phantoms and in water. As opposed to interferometric detection, GCLAD operates independently of the optical surface properties of the material. This allows the technique to be used in cases where the material is transparent or semi-transparent. We present results on sensing ultrasound in gelatin phantoms that are used to mimic biological materials. As with air-coupled transducers, the frequency response of GCLAD at high frequencies is limited by the high attenuation of ultrasound in air. In contrast, water has a much lower attenuation. Here we demonstrate the use of a GCLAD-like system in water, measuring the directivity response at 1 MHz and sensing waveforms with higher frequency content.

Caron, James N.; Kunapareddy, Pratima



Novelty detection by multivariate kernel density estimation and growing neural gas algorithm  

NASA Astrophysics Data System (ADS)

One of the underlying assumptions when using data-based methods for pattern recognition in diagnostics or prognostics is that the selected data sample used to train and test the algorithm is representative of the entire dataset and covers all combinations of parameters and conditions, and resulting system states. However in practice, operating and environmental conditions may change, unexpected and previously unanticipated events may occur and corresponding new anomalous patterns develop. Therefore for practical applications, techniques are required to detect novelties in patterns and give confidence to the user on the validity of the performed diagnosis and predictions. In this paper, the application of two types of novelty detection approaches is compared: a statistical approach based on multivariate kernel density estimation and an approach based on a type of unsupervised artificial neural network, called the growing neural gas (GNG). The comparison is performed on a case study in the field of railway turnout systems. Both approaches demonstrate their suitability for detecting novel patterns. Furthermore, GNG proves to be more flexible, especially with respect to dimensionality of the input data and suitability for online learning.

Fink, Olga; Zio, Enrico; Weidmann, Ulrich



Application of gas-coupled laser acoustic detection to gelatins and underwater sensing  

SciTech Connect

Gas-coupled Laser Acoustic Detection (GCLAD) has been used as a method to sense ultrasound waves in materials without contact of the material surface. To sense the waveform, a laser beam is directed parallel to the material surface and displaced or deflected when the radiated waveform traverses the beam. We present recent tests that demonstrate the potential of using this technique for detecting ultrasound in gelatin phantoms and in water. As opposed to interferometric detection, GCLAD operates independently of the optical surface properties of the material. This allows the technique to be used in cases where the material is transparent or semi-transparent. We present results on sensing ultrasound in gelatin phantoms that are used to mimic biological materials. As with air-coupled transducers, the frequency response of GCLAD at high frequencies is limited by the high attenuation of ultrasound in air. In contrast, water has a much lower attenuation. Here we demonstrate the use of a GCLAD-like system in water, measuring the directivity response at 1 MHz and sensing waveforms with higher frequency content.

Caron, James N. [Research Support Instruments, Lanham, MD 20706, USA and Quarktet, Silver Spring, MD 20901 (United States); Kunapareddy, Pratima [Research Support Instruments, Lanham, MD 20706 (United States)



Hierarchical Leak Detection and Localization Method in Natural Gas Pipeline Monitoring Sensor Networks  

PubMed Central

In light of the problems of low recognition efficiency, high false rates and poor localization accuracy in traditional pipeline security detection technology, this paper proposes a type of hierarchical leak detection and localization method for use in natural gas pipeline monitoring sensor networks. In the signal preprocessing phase, original monitoring signals are dealt with by wavelet transform technology to extract the single mode signals as well as characteristic parameters. In the initial recognition phase, a multi-classifier model based on SVM is constructed and characteristic parameters are sent as input vectors to the multi-classifier for initial recognition. In the final decision phase, an improved evidence combination rule is designed to integrate initial recognition results for final decisions. Furthermore, a weighted average localization algorithm based on time difference of arrival is introduced for determining the leak point’s position. Experimental results illustrate that this hierarchical pipeline leak detection and localization method could effectively improve the accuracy of the leak point localization and reduce the undetected rate as well as false alarm rate. PMID:22368464

Wan, Jiangwen; Yu, Yang; Wu, Yinfeng; Feng, Renjian; Yu, Ning



Strategies for Detecting Hidden Geothermal Systems by Near-Surface Gas Monitoring  

SciTech Connect

''Hidden'' geothermal systems are those systems above which hydrothermal surface features (e.g., hot springs, fumaroles, elevated ground temperatures, hydrothermal alteration) are lacking. Emissions of moderate to low solubility gases (e.g., CO2, CH4, He) may be one of the primary near-surface signals from these systems. Detection of anomalous gas emissions related to hidden geothermal systems may therefore be an important tool to discover new geothermal resources. This study investigates the potential for CO2 detection and monitoring in the subsurface and above ground in the near-surface environment to serve as a tool to discover hidden geothermal systems. We focus the investigation on CO2 due to (1) its abundance in geothermal systems, (2) its moderate solubility in water, and (3) the wide range of technologies available to monitor CO2 in the near-surface environment. However, monitoring in the near-surface environment for CO2 derived from hidden geothermal reservoirs is complicated by the large variation in CO2 fluxes and concentrations arising from natural biological and hydrologic processes. In the near-surface environment, the flow and transport of CO2 at high concentrations will be controlled by its high density, low viscosity, and high solubility in water relative to air. Numerical simulations of CO2 migration show that CO2 concentrations can reach very high levels in the shallow subsurface even for relatively low geothermal source CO2 fluxes. However, once CO2 seeps out of the ground into the atmospheric surface layer, surface winds are effective at dispersing CO2 seepage. In natural ecological systems in the absence of geothermal gas emissions, near-surface CO2 fluxes and concentrations are primarily controlled by CO2 uptake by photosynthesis, production by root respiration, and microbial decomposition of soil/subsoil organic matter, groundwater degassing, and exchange with the atmosphere. Available technologies for monitoring CO2 in the near-surface environment include (1) the infrared gas analyzer (IRGA) for measurement of concentrations at point locations, (2) the accumulation chamber (AC) method for measuring soil CO2 fluxes at point locations, (3) the eddy covariance (EC) method for measuring net CO2 flux over a given area, (4) hyperspectral imaging of vegetative stress resulting from elevated CO2 concentrations, and (5) light detection and ranging (LIDAR) that can measure CO2 concentrations over an integrated path. Technologies currently in developmental stages that have the potential to be used for CO2 monitoring include tunable lasers for long distance integrated concentration measurements and micro-electronic mechanical systems (MEMS) that can make widespread point measurements. To address the challenge of detecting potentially small-magnitude geothermal CO2 emissions within the natural background variability of CO2, we propose an approach that integrates available detection and monitoring methodologies with statistical analysis and modeling strategies. Within the area targeted for geothermal exploration, point measurements of soil CO2 fluxes and concentrations using the AC method and a portable IRGA, respectively, and measurements of net surface flux using EC should be made. Also, the natural spatial and temporal variability of surface CO2 fluxes and subsurface CO2 concentrations should be quantified within a background area with similar geologic, climatic, and ecosystem characteristics to the area targeted for geothermal exploration. Statistical analyses of data collected from both areas should be used to guide sampling strategy, discern spatial patterns that may be indicative of geothermal CO2 emissions, and assess the presence (or absence) of geothermal CO2 within the natural background variability with a desired confidence level. Once measured CO2 concentrations and fluxes have been determined to be of anomalous geothermal origin with high confidence, more expensive vertical subsurface gas sampling and chemical and isotopic analyses can be undertaken. Integrated analysis of all measurements will d

Lewicki, Jennifer L.; Oldenburg, Curtis M.



Estimation of seismically detectable portion of a gas plume: CO2CRC Otway project case study  

NASA Astrophysics Data System (ADS)

CO2CRC Otway project comprises of several experiments involving CO2/CH4 or pure CO2 gas injection into different geological formations at the Otway test site (Victoria, Australia). During the first stage of the project, which was finished in 2010, more than 64,000 t of gas were injected into the depleted gas reservoir at ~2 km depth. At the moment, preparations for the next stage of the project aiming to examine capabilities of seismic monitoring of small scale injection (up to 15,000 t) into saline formation are ongoing. Time-lapse seismic is one of the most typical methods for CO2 geosequestration monitoring. Significant experience was gained during the first stage of the project through acquisition and analysis of the 4D surface seismic and numerous time-lapse VSP surveys. In order to justify the second stage of the project and optimise parameters of the experiment, several modelling studies were conducted. In order to predict seismic signal we populate realistic geological model with elastic properties, model their changes using fluid substitution technique applied to the fluid flow simulation results and compute synthetic seismic baseline and monitor volumes. To assess detectability of the time-lapse signal caused by the injection, we assume that the time-lapse noise level will be equivalent to the level of difference between the last two Otway 3D surveys acquired in 2009 and 2010 using conventional surface technique (15,000 lbs vibroseis sources and single geophones as the receivers). In order to quantify the uncertainties in plume imaging/visualisation due to the time-lapse noise realisation we propose to use multiple noise realisations with the same F-Kx-Ky amplitude spectra as the field noise for each synthetic signal volume. Having signal detection criterion defined in the terms of signal/time- lapse noise level on a single trace we estimate visible portion of the plume as a function of this criterion. This approach also gives an opportunity to attempt to evaluate probability of the signal detection. The authors acknowledge the funding provided by the Australian government through its CRC program to support this CO2CRC research project. We also acknowledge the CO2CRC's corporate sponsors and the financial assistance provided through Australian National Low Emissions Coal Research and Development (ANLEC R&D). ANLEC R&D is supported by Australian Coal Association Low Emissions Technology Limited and the Australian Government through the Clean Energy Initiative.

Pevzner, Roman; Caspari, Eva; Bona, Andrej; Galvin, Robert; Gurevich, Boris



Detecting Organic Compounds in Martian Soil Analogues Using Gas Chromatography Mass Spectrometry  

NASA Technical Reports Server (NTRS)

One of the primary objectives of the 1976 Viking missions was to determine whether organic compounds, possibly of biological origin, were present in the Martian surface soils. The Viking gas chromatography mass spectrometry (GCMS) instruments found no evidence for any organic compounds of Martian origin above a few parts per billion in the upper 10 cm of surface soil [l], suggesting the absence of a widely distributed Martian biota. However, Benner et d. have suggested that significant amounts of non-volatile organic compounds, possibly including oxidation products of bioorganic molecules (e.g. carboxylic acids) would not have been detected by the Viking GCMS [2]. Moreover, other key organic compounds important to biology, such as amino acids and nucleobases, would also likely have been missed by the Viking GCMS as these compounds require chemical derivatization to be stable in a GC column [3]. Recent pyrolysis experiments with a Mars soil analogue that had been innoculated with Escherichia coli bacteria have shown that amino acid decomposition products (amines) and nucleobases are among the most abundant products generated after pyrolysis of the bacterial cells [4,5]. At the part per billion level (Viking GCMS detection limit), these pyrolysis products generated from several million bacterial cells per gram of Martian soil would not have been detected by the Viking GCMS instruments [4]. Analytical protocols are under development for upcoming in situ lander opportunities to target several important biological compounds including amino acids and nucleobases. For example, extraction and chemical derivatization techniques [3] are being adapted for space flight use to transform reactive or fragile molecules that would not have been detected by the Viking GCMS instruments, into species that are sufficiently volatile to be detected by GCMS. Recent experiments carried out at NASA Goddard have shown that using this derivatization technique all of the targeted compounds mentioned above can be separated on a GC column and detected by MS at sub-picomole (< 10(exp -l2 mole) levels. With these methods, the detection limit for amino acids, carboxylic acids and nucleobases is several orders of magnitude more sensitive than the Viking GCMS instruments for these compounds. Preliminary results using this analytical technique on a variety of Martian soil analogues will be presented.

Glavin, D. P.; Buch, A.; Mahaffy, P. R.



Development of carbon nanotube-based gas sensors for NO x gas detection working at low temperature  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT)-based NO x gas sensors which can operate at room temperature were prepared on Al 2O 3 substrates with interdigitated Pt-electrodes using both dc sputtering method and chemical vapor deposition (CVD) method. In this method, Al buffer layer and Fe catalytic thin film were prepared on the substrate by dc sputtering method and then CNTs were grown by thermal CVD method using ethylene gas. The scanning electron microscope (SEM) images of the CNTs on the substrates indicated that the vertically aligned multi-walled CNT (MWCNT) and the randomly oriented MWCNT were grown selectively by insertion of Al buffer layer. Gas sensing property to NO and NO 2 gases were measured. Resistance of the prepared CNT-based gas sensor decreased with increase of NO and NO 2 gas concentration. UV light irradiation was examined to detach the adsorbed gas molecule at room temperature. In this paper, it is suggested that CNT-based gas sensors have a great possibility to apply innovative NO x gas sensor from the experimental result.

Ueda, T.; Bhuiyan, M. M. H.; Norimatsu, H.; Katsuki, S.; Ikegami, T.; Mitsugi, F.



Possible Detection of Perchlorates by Evolved Gas Analysis of Rocknest Soils: Global Implication  

NASA Technical Reports Server (NTRS)

The Sample Analysis at Mars (SAM) instrument suite on board the Mars Science Laboratory (MSL) recently ran four samples from an aeolian bedform named Rocknest. Rocknest was selected as the source of the first samples analyzed because it is representative of both windblown material in Gale crater as well as the globally-distributed dust. The four samples analyzed by SAM were portioned from the fifth scoop at this location. The material delivered to SAM passed through a 150 m sieve and should have been well mixed during the sample acquisition/ preparation/handoff process. Rocknest samples were heated to 835 C at a 35 C/minute ramp rate with a He carrier gas flow rate of 1.5 standard cubic centimeters per minute and at an oven pressure of 30 mbar. Evolved gases were detected by a quadrupole mass spectrometer (QMS).

Archer, P. D., Jr.; Sutter, B.; Ming, D. W.; McKay, C. P.; Navarro-Gonzalez, R.; Franz, H. B.; McAdam, A.; Mahaffy, P. R.



Sensitive trace gas detection with near-infrared laser diodes and an integrating sphere.  


We describe a simple spectrometer for sensitive trace gas detection in the atmosphere. A communication laser diode is used as a light source, and a commercial integrating sphere is used as a multipass absorption cell. We developed a theoretical formulation of the relative absorption of the optical power by trace gases in the sphere and applied it to two kinds of experimental result: one that is concerned with a structureless broad absorption band of butane with the use of a 1.2-?m multimode laser diode, and one that is related to the study of an isolated and sharp rovibrational line of water vapor in air at atmospheric pressure with the use of an 830-nm single-mode laser diode. With equivalent path lengths of several meters obtained with a 10-cm-i.d. integrating sphere we can demonstrate the usefulness of such a device as a broadband multipass cell for the measurement of small absorptions. PMID:21151310

Tranchart, S; Bachir, I H; Destombes, J L



Rapid, automated gas chromatographic detection of organic compounds in ultra-pure water  

SciTech Connect

An automated gas chromatography was used to analyze water samples contaminated with trace (parts-per-billion) concentrations of organic analytes. A custom interface introduced the liquid sample to the chromatography. This was followed by rapid chromatographic analysis. Characteristics of the analysis include response times less than one minute and automated data processing. Analytes were chosen based on their known presence in the recycle water streams of semiconductor manufacturers and their potential to reduce process yield. These include acetone, isopropanol, butyl acetate, ethyl benzene, p-xylene, methyl ethyl ketone and 2-ethoxy ethyl acetate. Detection limits below 20 ppb were demonstrated for all analytes and quantitative analysis with limited speciation was shown for multianalyte mixtures. Results are discussed with respect to the potential for on-line liquid process monitoring by this method.




Recent Advances in Gas and Chemical Detection by Vernier Effect-Based Photonic Sensors  

PubMed Central

Recently, the Vernier effect has been proved to be very efficient for significantly improving the sensitivity and the limit of detection (LOD) of chemical, biochemical and gas photonic sensors. In this paper a review of compact and efficient photonic sensors based on the Vernier effect is presented. The most relevant results of several theoretical and experimental works are reported, and the theoretical model of the typical Vernier effect-based sensor is discussed as well. In particular, sensitivity up to 460 ?m/RIU has been experimentally reported, while ultra-high sensitivity of 2,500 ?m/RIU and ultra-low LOD of 8.79 × 10?8 RIU have been theoretically demonstrated, employing a Mach-Zehnder Interferometer (MZI) as sensing device instead of an add drop ring resonator. PMID:24618728

La Notte, Mario; Troia, Benedetto; Muciaccia, Tommaso; Campanella, Carlo Edoardo; De Leonardis, Francesco; Passaro, Vittorio M. N.



Damage and sealing of clay rocks detected by measurements of gas permeability  

NASA Astrophysics Data System (ADS)

Various damage and sealing experiments have been performed on samples of the Callovo-Oxfordian argillite and the Opalinus clay in order to enhance the knowledge about the development of the excavation damaged zone around nuclear waste repositories in clay formations. Stress-induced damage and permeability changes were examined in triaxial compression tests. Preliminary criteria were derived for the detection of dilatancy, percolation, and failure boundaries. By measuring the gas permeability changes due to re-compaction and re-saturation, the self-sealing behaviour of strongly damaged clay samples was investigated. Short-term re-compaction by increasing the confining stress up to 15 MPa reduced the permeability by several orders of magnitude to 10 -19-10 -20 m 2. After water re-saturation, the permeability of the damaged samples decreased significantly to 10 -21 m 2. All laboratory observations suggest a high self-sealing capacity of the studied clay rocks.

Zhang, Chun-Liang; Rothfuchs, Tilmann


Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experimentsa)  

NASA Astrophysics Data System (ADS)

A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ?400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ˜400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

Herrmann, H. W.; Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.; Batha, S. H.



Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments  

SciTech Connect

A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ?400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C{sub 2}F{sub 6}, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ?400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

Herrmann, H. W., E-mail:; Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Batha, S. H. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Malone, R. M. [National Security Technologies, LLC, Los Alamos, New Mexico 87544 (United States); Rubery, M. S.; Horsfield, C. J. [Atomic Weapons Establishment, Aldermaston, Berkshire RG7 4PR (United Kingdom); Stoeffl, W. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Zylstra, A. B. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Shmayda, W. T. [Laboratory for Laser Energetics, Rochester, New York 14623 (United States)




SciTech Connect

The objective of this project is to design, fabricate and field demonstrate a cost effective, multi-spectral scanner for natural gas leak detection in transmission and distribution pipelines. During the first six months of the project, the design for a laboratory version of the multispectral scanner was completed. The optical, mechanical, and electronic design for the scanner was completed. The optical design was analyzed using Zeemax Optical Design software and found to provide sufficiently resolved performance for the scanner. The electronic design was evaluated using a bread board and very high signal to noise ratios were obtained. Fabrication of a laboratory version of the multi-spectral scanner is currently in progress. A technology status report and a research management plan was also completed during the same period.

Yudaya Sivathanu; Jongmook Lim; Vinoo Narayanan



Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.  


A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ?400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ?400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds. PMID:25430303

Herrmann, H W; Kim, Y H; Young, C S; Fatherley, V E; Lopez, F E; Oertel, J A; Malone, R M; Rubery, M S; Horsfield, C J; Stoeffl, W; Zylstra, A B; Shmayda, W T; Batha, S H



Low-level detection of ethanol and H 2S with temperature-modulated WO 3 nanoparticle gas sensors  

Microsoft Academic Search

Low-level detection of ethanol and H2S was achieved with thermally modulated WO3 nanoparticle gas sensors. Nanoparticle WO3 films, with a mean grain size of ?5nm and a thickness of ?20?m, were produced by advanced reactive gas evaporation onto alumina substrates. The working temperature of the sensor was periodically modulated between 150 and 250°C, and the response was analysed by fast

R. Ionescu; A. Hoel; C. G. Granqvist; E. Llobet; P. Heszler



Highly selective probe detects Cu2+ and endogenous NO gas in living cell.  


The rapid and highly sensitive detection of extremely short-lived nitric oxide (NO) gas generated in vivo by a water-soluble fluorescein derivative is developed. This assay system comprises of indole-3-carboxaldehyde functionalized fluorescein hydrazone (FI) assay which displays a typically high absorption at 492 and 620 nm in the presence of Cu2+ and also shows FRET induced fluorescence turn-on exclusively with Cu2+. FI selectively detects Cu2+ in vivo and in vitro by the "turn-on" mechanism followed by fluorescence "turn-off" with NO gas generated by the lipopolysaccharide (LPS) action. The in vivo experiment performed in the cellular system indicates that FI loaded RAW264.7 cells showed bright fluorescence in the presence of Cu2+, while other metals did not influence the FI fluorescence. In addition, the fluorescence of FI-Cu2+ was efficiently quenched by NO generated in macrophages through LPS stimulation. FI demonstrates characteristic "turn-on" behavior in the presence of Cu2+ via spirolactom ring-opening, while other metals such as Na+, K+, Ca2+, Cr3+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, and Ag+ did not influence FI fluorescence even at very high concentration. Further, the FI-Cu2+ complex fluorescence was not quenched with any anions or amino acids but totally quenched by NO and the paramagnetic nature of Cu2+ ion converted into the diamagnetic nature when reduced to Cu1+. FI and the FI-Cu2+ complex are nontoxic to the cellular system and have high potential for biomedical applications. PMID:24703409

Muthuraj, Balakrishnan; Deshmukh, Rohitas; Trivedi, Vishal; Iyer, Parameswar Krishnan



Detection of nerve agents using proton transfer reaction mass spectrometry with ammonia as reagent gas.  


The chemical warfare agents (CWA) Sarin, Soman, Cyclosarin and Tabun were characterised by proton transfer mass spectrometry (PTRMS). It was found that PTRMS is a suitable technique to detect nerve agents highly sensitively, highly selectively and in near real-time. Methods were found to suppress molecule fragmentation which is significant under PTRMS hollow cathode ionisation conditions. In this context, the drift voltage (as one of the most important system parameters) was varied and ammonia was introduced as an additional chemical reagent gas. Auxiliary chemicals such as ammonia affect ionisation processes and are quite common in context with detectors for CWAs based on ion mobility spectrometry (IMS). With both, variation of drift voltage and ammonia as the reagent gas, fragmentation can be suppressed effectively. Suppression of fragmentation is crucial particularly concerning the implementation of an algorithm for automated agent identification in field applications. On the other hand, appearance of particular fragments might deliver additional information. Degradation and rearrangement products of nerve agents are not distinctive for the particular agent but for the chemical class they belong to. It was found that switching between ammonia doped and ordinary water ionisation chemistry can easily be performed within a few seconds. Making use of this effect it is possible to switch between fragment and molecular ion peak spectra. Thus, targeted fragmentation can be used to confirm identification based only on single peak detection. PTRMS turned out to be a promising technique for future CWA detectors. In terms of sensitivity, response time and selectivity (or confidence of identification, respectively) PTRMS performs as a bridging technique between IMS and GC-MS. PMID:24308198

Ringer, Joachim M



Detection of exhaled hydrogen sulphide gas in rats exposed to intravenous sodium sulphide  

PubMed Central

Background and purpose: Sodium sulphide (Na2S) disassociates to sodium (Na+) hydrosulphide, anion (HS?) and hydrogen sulphide (H2S) in aqueous solutions. Here we have established and characterized a method to detect H2S gas in the exhaled breath of rats. Experimental approach: Male rats were anaesthetized with ketamine and xylazine, instrumented with intravenous (i.v.) jugular vein catheters, and a tube inserted into the trachea was connected to a pneumotach connected to a H2S gas detector. Sodium sulphide, cysteine or the natural polysulphide compound diallyl disulphide were infused intravenously while the airway was monitored for exhaled H2S real time. Key results: Exhaled sulphide concentration was calculated to be in the range of 0.4–11 ppm in response to i.v. infusion rates ranging between 0.3 and 1.1 mg·kg?1·min?1. When nitric oxide synthesis was inhibited with N?-nitro-L-arginine methyl ester the amount of H2S exhaled during i.v. infusions of sodium sulphide was significantly increased compared with that obtained with the vehicle control. An increase in circulating nitric oxide using DETA NONOate [3,3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene] did not alter the levels of exhaled H2S during an i.v. infusion of sodium sulphide. An i.v. bolus of L-cysteine, 1 g·kg?1, and an i.v. infusion of the garlic derived natural compound diallyl disulphide, 1.8 mg·kg?1·min?1, also caused exhalation of H2S gas. Conclusions and implications: This method has shown that significant amounts of H2S are exhaled in rats during sodium sulphide infusions, and the amount exhaled can be modulated by various pharmacological interventions. PMID:19422378

Insko, Michael A; Deckwerth, Thomas L; Hill, Paul; Toombs, Christopher F; Szabo, Csaba



Fiber-optic photo-acoustic spectroscopy sensor for harsh environment gas detection  

NASA Astrophysics Data System (ADS)

Photo-acoustic spectroscopy (PAS) has been successfully applied to detect various gases and chemicals due to its high selectivity and sensitivity. However, the performance of the conventional acoustic sensors prohibits the application of PAS for harsh environment gas species real-time monitoring. By replacing conventional acoustic sensors, such as microphone and piezo-transducers, with a high-temperature Fiber Bragg Grating (FBG) vibration sensor, we developed a fiber-optic PAS sensing system that can be used in high-temperature and high-pressure harsh environments for gas species identification and concentration measurement. A resonant acoustic chamber is designed, and FBG vibration sensor is embedded in the molybdenum membrane. An OPO laser is used for spectrum scanning. Preliminary test on water vapor has been conducted, and the result is analyzed. This sensing technology can be adapted into harsh environments, such as Integrated Gasification Combined Cycle (IGCC) power plant, and provide on-line real-time monitoring of gases species, such as CO, H IIO, and O II. Presently, our FBG-based vibration sensor can withstand the high temperature up to 800°C.

Wu, Juntao; Deng, Kung-Li; Guida, Renato; Lee, Boon




SciTech Connect

Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. This second six-month technical report summarizes the progress made towards defining, designing, and developing the hardware and software segments of the airborne, optical remote methane and ethane sensor. The most challenging task to date has been to identify a vendor capable of designing and developing a light source with the appropriate output wavelength and power. This report will document the work that has been done to identify design requirements, and potential vendors for the light source. Significant progress has also been made in characterizing the amount of light return available from a remote target at various distances from the light source. A great deal of time has been spent conducting laboratory and long-optical path target reflectance measurements. This is important since it helps to establish the overall optical output requirements for the sensor. It also reduces the relative uncertainty and risk associated with developing a custom light source. The data gathered from the optical path testing has been translated to the airborne transceiver design in such areas as: fiber coupling, optical detector selection, gas filters, and software analysis. Ophir will next, summarize the design progress of the transceiver hardware and software development. Finally, Ophir will discuss remaining project issues that may impact the success of the project.

Jerry Myers



Calorimetric Thermoelectric Gas Sensor for the Detection of Hydrogen, Methane and Mixed Gases  

PubMed Central

A novel miniaturized calorimeter-type sensor device with a dual-catalyst structure was fabricated by integrating different catalysts on the hot (Pd/?-Al2O3) and cold (Pt/?-Al2O3) ends of the device. The device comprises a calorimeter with a thermoelectric gas sensor (calorimetric-TGS), combining catalytic combustion and thermoelectric technologies. Its response for a model fuel gas of hydrogen and methane was investigated with various combustor catalyst compositions. The calorimetric-TGS devices detected H2, CH4, and a mixture of the two with concentrations ranging between 200 and 2000 ppm at temperatures of 100–400 °C, in terms of the calorie content of the gases. It was necessary to reduce the much higher response voltage of the TGS to H2 compared to CH4. We enhanced the H2 combustion on the cold side so that the temperature differences and response voltages to H2 were reduced. The device response to H2 combustion was reduced by 50% by controlling the Pt concentration in the Pt/?-Al2O3 catalyst on the cold side to 3 wt%. PMID:24818660

Park, Nam-Hee; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck



Detecting buried radium contamination using soil-gas and surface-flux radon meaurements  

SciTech Connect

The Technical Measurements Center (TMC) has investigated the effectiveness of using radon soil-gas under surface-flux measurments to locate radium contamination that is buried sufficiently deep to be undetectable by surface gamma methods. At the first test site studied, an indication of a buried source was revealed by mapping anomalous surface-flux and soil-gas concentrations in the near surface overburden. The mapped radon anomalies were found to correspond in rough outline to the shape of the areal extent of the deposit as determined by borehole gamma-ray logs. The 5.9pCi/g radium deposit, buried 2 feet below the surface, went undetected by conventional surface gamma measurements. Similar results were obtained at the second test site where radon and conventional surface gamma measurements were taken in an area having radium concentrations ranging from 13.3 to 341.0 pCi/g at a depth of 4 feet below the surface. The radon methods were found to have a detection limit for buried radium lower than that of the surface gamma methods, as evidenced by the discovery of the 13.3 pCi/g deposit which went undetected by the surface gamma methods. 15 refs., 33 figs., 8 tabs.

Karp, K.E.



CO Gas Detection of Al-Doped ZnO Nanostructures with Various Shapes  

NASA Astrophysics Data System (ADS)

Nanostructure of semiconductor type gas sensors that are high sensitivity, fast response time, inexpensive, and easily fabricated, is suggested. One-dimensional (1D) nanostructures, such as nanorods, and hollow spheres, are attracting particularly great interest because of their large specific surface area and their inherent physical properties. This study combined with ZnCl2 (6.95 g, Sigma-Aldrich), Al(NO3)3.9H2O (Junsei), NaOH, ethanol, and deionized water (DI) by hydrothermal synthesis to manufacture, spherical, hollow, hierarchical, and nanorod. The same Al-doped ZnO (AZO) were prepared by a colloidal template on a Si wafer to make a 3D igloo structure as well. Sensitivity to carbon monoxide at 50 ppm was tested at 250 °C the compare the sensing properties. Gas sensitivity of the hierarchical structure showed the highest sensitivity at 31.8, a figure 7 times that of the packed spherical sphere, whereas the igloo structure gave the fastest response speed of 32 s. The results of various shapes of the AZO nanostructures demonstrated high sensitivity and quick response time, which is useful in the detection of harmful gases in automobiles and the atmosphere.

Wang, Byung-Yong; Lim, Dae-Soon; Oh, Young-Jei



Modeling Noble Gas Transport and Detection for The Comprehensive Nuclear-Test-Ban Treaty  

NASA Astrophysics Data System (ADS)

Detonation gases released by an underground nuclear test include trace amounts of 133Xe and 37Ar. In the context of the Comprehensive Nuclear Test Ban Treaty, On Site Inspection Protocol, such gases released from or sampled at the soil surface could be used to indicate the occurrence of an explosion in violation of the treaty. To better estimate the levels of detectability from an underground nuclear test (UNE), we developed mathematical models to evaluate the processes of 133Xe and 37Ar transport in fractured rock. Two models are developed respectively for representing thermal and isothermal transport. When the thermal process becomes minor under the condition of low temperature and low liquid saturation, the subsurface system is described using an isothermal and single-gas-phase transport model and barometric pumping becomes the major driving force to deliver 133Xe and 37Ar to the ground surface. A thermal test is simulated using a nonisothermal and two-phase transport model. In the model, steam production and bubble expansion are the major processes driving noble gas components to ground surface. After the temperature in the chimney drops below boiling, barometric pumping takes over the role as the major transport process.

Sun, Yunwei; Carrigan, Charles R.



Detecting Methane From Leaking Pipelines and as Greenhouse Gas in the Atmosphere  

NASA Technical Reports Server (NTRS)

Laser remote sensing measurements of trace gases from orbit can provide unprecedented information about important planetary science and answer critical questions about planetary atmospheres. Methane (CH4) is the second most important anthropogenically produced greenhouse gas. Though its atmospheric abundance is much less than that of CO2 (1.78 ppm vs. 380 ppm), it has much larger greenhouse heating potential. CH4 also contributes to pollution in the lower atmosphere through chemical reactions, leading to ozone production. Atmospheric CH4 concentrations have been increasing as a result of increased fossil fuel production, rice farming, livestock, and landfills. Natural sources of CH4 include wetlands, wild fires, and termites, and perhaps other unknown sources. Important sinks for CH4 include non-saturated soils and oxidation by hydroxyl radicals in the atmosphere. Remotely measuring CH4 and other biogenic molecules (such as ethane and formaldehyde) on Mars also has important implications on the existence of life on Mars. Measuring CH4 at very low (ppb) concentrations from orbit will dramatically improve the sensitivity and spatial resolution in the search for CH4 vents and sub-surface life on other planets. A capability has been developed using lasers and spectroscopic detection techniques for the remote measurements of trace gases in open paths. Detection of CH4, CO2, H2O, and CO in absorption cells and in open paths, both in the mid- IR and near-IR region, has been demonstrated using an Optical Parametric Amplifier laser transmitter developed at GSFC. With this transmitter, it would be possible to develop a remote sensing methane instrument. CH4 detection also has very important commercial applications. Pipeline leak detection from an aircraft or a helicopter can significantly reduce cost, response time, and pinpoint the location. The main advantage is the ability to rapidly detect CH4 leaks remotely. This is extremely important for the petrochemical industry. This capability can be used in manned or unmanned airborne platforms for the detection of leaks in pipelines and other areas of interest where a CH4 leak is suspected.

Riris, Haris; Numata, Kenji; Li, Steven; Wu, Stewart; Ramanathan, Anand; Dawsey, Martha



Development of a multiple gas analyzer using cavity ringdown spectroscopy for use in advanced fire detection.  


A portable cavity ringdown spectroscopy (CRDS) apparatus was used to detect effluents from small test fires in the Fire Emulator/Detector Evaluator (FE/DE) and a small room in the Building Fire and Research Laboratory at the National Institute of Standards and Technology (NIST). The output from two lasers is combined to detect four combustion gases, CO, CO(2), HCN, and C(2)H(2), near simultaneously using CRDS. The goal of this work was to demonstrate the feasibility of using a CRDS sensor as a fire detector. Fire effluents were extracted from several test facilities and measurements of CO, CO(2), HCN, and C(2)H(2) were obtained every 25-30 s. In the FE/DE test, peak concentrations of the gases from smoldering paper were 420 parts in 10(6) (ppm) CO, 1600 ppm CO(2), 530 parts in 10(9) (ppb) HCN, and 440 ppb C(2)H(2). Peak gas concentrations from the small room were 270 ppm CO, 2100 ppm CO(2), and 310 ppb C(2)H(2). PMID:19183595

Fallows, Eric A; Cleary, Thomas G; Miller, J Houston



Fingerprinting of vegetable oil minor components by multidimensional comprehensive gas chromatography with dual detection.  


The potentiality of a multidimensional comprehensive gas chromatographic (GC?×?GC) method, employing a simultaneous dual detection (FID and mass spectrometer), to generate peculiar two-dimensional chromatograms to be used as a chemical fingerprint, was investigated to characterize minor compounds in edible oil, particularly olive oil. The best column combination for this application was investigated comparing two column sets (orthogonal or reverse-type), equivalent in terms of theoretical plate number, but differing in stationary phase combination. The apolar?×?mid-polar set gave a superior separation power, thus was used for further characterization. Different levels of information were extrapolated from the two-dimensional chromatogram. Using the FID, reliable quantification of the alkyl esters fatty acids and waxes was obtained, comparable to the results obtained using the official method, as required by the European legislation. However, thanks to a slight modification of the sample preparation method, the increased separation power obtained using the GC?×?GC method, and the support of the mass spectrometer detector, further diagnostic information was extrapolated considering the free sterol and tocopherol fractions. In particular, the profiles of extra virgin olive oil samples were compared with a hazelnut oil sample, highlighting that the latter was characterized by a larger number of compounds, completely absent in the extra virgin olive oil samples, which can be used to detect illegal admixtures. PMID:25209809

Purcaro, Giorgia; Barp, Laura; Beccaria, Marco; Conte, Lanfranco S



Infiltration rate measurement by active perfluorocarbon monitoring  

SciTech Connect

The rate of air infiltration in homes and buildings is a significant factor affecting the magnitude of human exposure to air pollutants in the indoor environment. Several techniques have been utilized for the determination of air infiltration. These include building pressurization and tracer analysis, e.g., SF/sub 6/. Dietz and Cote at Brookhaven National Laboratory (BNL) have developed a simple, steady-state tracer kit that can be utilized by homeowners. This kit includes a source(s) of perfluorocarbon, i.e., perfluoromethylcyclohexane (PMCH) or perfluorodimethylcyclohexane (PDCH), and a passive sampling tube containing Ambersorb XE-347. Typically, the sampling tube is deployed for several days and then returned to a laboratory for analysis by thermal desorption/gas chromatography/electron capture detection. The authors developed an alternative sampling and analysis technique for PMCH/PDCH in homes. In order to facilitate monitoring of short-term infiltration rates (i.e., less than one day) they developed an active sorbent sampling method and solvent desorption/gas chromatography/electron capture detection analytical method. The method is based on the collection of PMCH on charcoal. The method validation, which is discussed in this article, includes analytical method development, selection of a solid sorbent, determination of desorption efficiency, analysis of breakthrough, testing of storage stability, and assessment of precision and accuracy in both the laboratory and field environment.

Menzies, K.T.; Pong, C.M.; Randel, M.A. (Arthur D. Little, Inc., Cambridge, MA (US))



Lung cancer detection by proton transfer reaction mass-spectrometric analysis of human breath gas  

NASA Astrophysics Data System (ADS)

Background Determination of the diagnostic usefulness of proton transfer reaction mass spectrometry (PTR-MS) for detecting primary lung cancer through analysis of volatile organic compounds (VOCs) in exhaled human breath was demonstrated in this investigation. Unlike, for example, gas-chromatographic analyses, PTR-MS can be used without time-consuming preconcentration of the gas samples.Methods By means of PTR-MS, exhaled breath samples from primary lung cancer patients (n = 17) were analyzed and compared with both an overall control collective (controls total, n = 170) and three sub-collectives: hospital personnel (controls hospital, n = 35), age-matched persons (controls age, n = 25), and smokers (controls s, n = 60), respectively.Results Among the VOCs present at reasonably high concentrations, the ones leading to the product ion at m/z = 31 (VOC-31, tentatively protonated formaldehyde) and m/z = 43 (VOC-43, tentatively a fragment of protonated iso-propanol), were found at significantly higher concentrations in the breath gas of the primary lung cancer patients as compared to the healthy controls at the following median concentrations (with interquartile distance, iqr): For VOC-31 the median concentrations were 7.0 ppb (iqr, 15.5 ppb) versus 3.0 ppb (iqr, 1.9 ppb) with P < 10-4. For VOC-43 the median concentrations were 244.1 ppb (iqr, 236.2 ppb) versus 94.1 ppb (iqr, 55.2 ppb) with P < 10-6. The discriminative power between the two collectives was further assessed by ROC-curves obtained upon variation of the chosen threshold concentration and by Fisher's Quadratic Discriminant Method.Conclusions Within the limits of pilot study, VOC-31 and -43 were found to best discriminate between exhaled breath of primary lung cancer cases and healthy controls. Simple and time-saving breath gas analysis by PTR-MS makes this method attractive for a larger clinical evaluation. It may become a new valuable tool for diagnosing primary lung cancer.

Wehinger, Andreas; Schmid, Alex; Mechtcheriakov, Sergei; Ledochowski, Maximilian; Grabmer, Christoph; Gastl, Guenther A.; Amann, Anton



A ground-based trace gas observing system for detection of Arctic and Boreal change  

NASA Astrophysics Data System (ADS)

The large reservoir of below-ground organic carbon in the Arctic and Boreal region (ABR) permafrost, combined with large observed and predicted temperature changes leads to the expectation of increasing surface emissions of CO2 and/or CH4 this century. However, the near-term response of northern ecosystems could be enhanced ecosystem productivity and carbon sequestration via, among other causes, longer growing seasons and encroachment of woody species into Arctic tundra. Regardless of the temporal evolution of carbon (both CO2 and CH4) sources and sinks in the ABR, monitoring these changes at regional (~10^5 - 10^6 km^2) scales using trace gas mixing and isotopic ratios will be a critical complement to detailed process-based studies at the plot scale and remote sensing of the land surface. Turbulent mixing in the lower few kilometers of the atmosphere naturally integrates emissions from all known and unknown processes and can provide a powerful bottom-line constraint on the net result of both sources and sinks. We will present the first year of results of a trace-gas measurement system capable of daily or more frequent observations of more than 50 trace gas species, including CO2, CH4 and their stable and radio isotope ratios. The measurements were initiated as part of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and come from a 30 m tower located on a ridge in central Alaska. Central Alaska is dominated by discontinuous permafrost, which is likely to undergo significant changes in the coming decades. Footprint analysis suggests that mixing ratios measured at the tower are influenced by large swaths of central Alaska, although in winter, anthropogenic emissions form the city of Fairbanks are evident. In summer, as expected, we observe a large drawdown of CO2. The seasonal cycle of CH4 is dominated by the large-scale destruction of methane by hydroxyl radical (OH). However, based on previous measurements from other ABR sites, we expect summer/fall wetland emissions to be evident as a late summer/early fall bulge. Moreover, analysis of ?13C of CH4 has also indicated that methane consumption by OH masks a substantial biogenic (mostly wetland) source in summer. Starting summer 2012, 14C of CH4 measurements were initiated to help determine the age of the biogenic emissions. In addition to biogenic tracers, a large suite of measured anthropogenic tracers can be used to identify periods of transport from both local (i.e. Fairbanks) and mid-latitude sources of pollutant CO, CO2 and CH4. As a whole, our tower measurements represent an important component of detecting trace gas emissions from permafrost.

Karion, A.; Miller, J. B.; Sweeney, C.; Bruhwiler, L.; Newberger, T.; Miller, C. E.; Dinardo, S. J.; Wolter, S.; Ledlow, L.



An investigation of the matrix sensitivity of refinery gas analysis using gas chromatography with flame ionisation detection.  


The response of a flame ionisation detector (FID) on a gas chromatograph to methane, ethane, propane, i-butane and n-butane in a series of multi-component refinery gas standards was investigated to assess the matrix sensitivity of the instrument. High-accuracy synthetic gas standards, traceable to the International System of Units, were used to minimise uncertainties. The instrument response exhibited a small dependence on the component amount fraction: this behaviour, consistent with that of another FID, was thoroughly characterised over a wide range of component amount fractions and was shown to introduce a negligible bias in the analysis of refinery gas samples, provided a suitable reference standard is employed. No significant effects of the molar volume, density and viscosity of the gas mixtures on the instrument response were observed, indicating that the FID is suitable for the analysis of refinery gas mixtures over a wide range of component amount fractions provided that appropriate drift-correction procedures are employed. PMID:25620742

Ferracci, Valerio; Brown, Andrew S; Harris, Peter M; Brown, Richard J C




EPA Science Inventory

The SRI Model 86 1 OC gas chromatograph (GC) is a transportable instrument that can provide on-site analysis of soils for explosives. Coupling this transportable gas chromatograph with a thermionic ionization detector (TID) allows for the determination of explosives in soil matri...


Detection of gas hydrate with downhole logs and assessment of gas hydrate concentrations (saturations) and gas volumes on the Blake Ridge with electrical resistivity log data  

USGS Publications Warehouse

Let 164 of the Ocean Drilling Program was designed to investigate the occurrence of gas hydrate in the sedimentary section beneath the Blake Ridge on the southeastern continental margin of North America. Site 994, and 997 were drilled on the Blake Ridge to refine our understanding of the in situ characteristics of natural gas hydrate. Because gas hydrate is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the gas hydrate-bearing sediments. Downhole logging tool strings deployed on Leg 164 included the Schlumberger quad-combination tool (NGT, LSS/SDT, DIT, CNT-G, HLDT), the Formation MicroScanner (FMS), and the Geochemical Combination Tool (GST). Electrical resistivity (DIT) and acoustic transit-time (LSS/SDT) downhole logs from Sites 994, 995, and 997 indicate the presence of gas hydrate in the depth interval between 185 and 450 mbsf on the Blake Ridge. Electrical resistivity log calculations suggest that the gas hydrate-bearing sedimentary section on the Blake Ridge may contain between 2 and 11 percent bulk volume (vol%) gas hydrate. We have determined that the log-inferred gas hydrates and underlying free-gas accumulations on the Blake Ridge may contain as much as 57 trillion m3 of gas.

Collett, T.S.; Ladd, J.



Imaging Molecular Gas in the Luminous Merger NGC 3256 : Detection of High-Velocity Gas and Twin Gas Peaks in the Double Nucleus  

E-print Network

Molecular gas in the merging starburst galaxy NGC 3256 has been imaged with the Submillimeter Array at a resolution of 1'' x 2'' (170 x 340 pc at 35 Mpc). This is the first interferometric imaging of molecular gas in the most luminous galaxy within z=0.01. There is a large disk of molecular gas (r > 3 kpc) in the center of the merger with a strong gas concentration toward the double nucleus. The gas disk having a mass of ~3*10^9 Msun in the central 3 kpc rotates around a point between the two nuclei that are 850 pc apart on the sky. The molecular gas is warm and turbulent and shows spatial variation of the intensity ratio between CO isotopomers. High-velocity molecular gas is discovered at the galactic center. Its velocity in our line of sight is up to 420 km/s offset from the systemic velocity of the galaxy; the terminal velocity is twice as large as that due to the rotation of the main gas disk. The high-velocity gas is most likely due to a molecular outflow from the gas disk, entrained by the starburst-driven superwind in the galaxy. The molecular outflow is estimated to have a rate of ~10 Msun/yr and to play a significant role in the dispersal or depletion of molecular gas from the galactic center. A compact gas concentration and steep velocity gradient are also found around each of the twin nuclei. They are suggestive of a small gas disk rotating around each nucleus. If these are indeed mini-disks, their dynamical masses are ~10^9 Msun within a radius of 170 pc.

Kazushi Sakamoto; Paul T. P. Ho; Alison B. Peck



Determination of trichothecenes in duplicate diets of young children by capillary gas chromatography with mass spectrometric detection  

Microsoft Academic Search

Trichothecenes are mycotoxins produced by several fungal genera, mainly Fusarium species, that can contaminate a wide range of cereals used for human and animal consumption. They are associated with various adverse health effects in animals and humans such as feed refusal, vomiting and immunotoxic effects. A method based on capillary gas chromatography with mass spectrometric detection was developed and validated

R. C. Schothorst; A. A. Jekel; H. P. Van Egmond; A. de Mul; P. E. Boon; J. D. Van Klaveren



Discovery of a natural CO2 seep in the German North Sea: Implications for shallow dissolved gas and seep detection  

E-print Network

Discovery of a natural CO2 seep in the German North Sea: Implications for shallow dissolved gas and seep detection Daniel F. McGinnis,1 Mark Schmidt,1 Tonya DelSontro,2 Sören Themann,3 Lorenzo Rovelli,1 2010; published 5 March 2011. [1] A natural carbon dioxide (CO2) seep was discovered during

Wehrli, Bernhard


Portal venous gas: detection by gray-scale and Doppler sonography in the absence of correlative findings on computed tomography  

Microsoft Academic Search

Two cases are described in which portal venous gas (PVG) was detectable by ultrasound, but the liver appeared normal on computed tomography (CT). The finding of PVG was associated with ischemic bowel in one case but was a benign finding in the other case. The gray-scale and Doppler ultrasound findings associated with PVG are described. This case report illustrates two

M. M. Maher; B. M. Tonra; D. E. Malone; R. G. Gibney



Factor of merit and minimum detectable activity for 90Sr determinations by gas-flow proportional counting or Cherenkov counting.  


The determination of 90Sr in environmental samples can be done by using a gas-flow proportional counter (beta-counting) or a liquid-scintillation spectrometer (Cherenkov counting). In this work, we present the factor of merit (FOM) and the minimum detectable activity (MDA) for both the counters. Quantitative relationships are proposed for FOM and MDA determination. PMID:11761109

Vaca, F; Manjón, G; Cuéllar, S; García-León, M




EPA Science Inventory

A capillary gas chromatography-atomic emission detection (GC-AED) method was developed for the U. S. Environmental Protection Agency's Environmental Monitoring Systems Laboratory in Las Vegas, NV, for determination of selected organotin compounds. Here we report on an interlabora...



EPA Science Inventory

As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organ...


Part-per-million gas detection from long-baseline THz spectroscopy S. A. Harmon and R. A. Chevillea)  

E-print Network

Part-per-million gas detection from long-baseline THz spectroscopy S. A. Harmon and R. A. Chevillea (Received 10 May 2004; accepted 6 July 2004) We report a long-baseline THz time domain spectrometer based. [DOI: 10.1063/1.1788896] Optically generated pulses of electromagnetic radiation with terahertz THz


Detection of sibutramine administration: a gas chromatography/mass spectrometry study of the main urinary metabolites.  


A gas chromatographic/mass spectrometric (GC/MS) study aimed at identifying the metabolites of sibutramine (1-(4-chlorophenyl)-N,N-dimethyl-alpha-(2-methylpropyl)cyclobutanemethanamine) in urine is described. Urinary excretion of sibutramine metabolites following the oral administration of a single dose of sibutramine was followed by GC/MS analysis. After identification of the chromatographic signals corresponding to the six main urinary metabolites, the fragmentation pattern was studied in electron ionization (EI) mode after derivatization to the corresponding methyl and trimethylsilyl derivatives. Urine samples were pretreated according to a reference procedure (liquid/liquid separation, enzymatic hydrolysis, pre-concentration under a stream of nitrogen and derivatization, either under thermal incubation and by microwave irradiation). All sibutramine metabolites were excreted as glucuroconjugates, and retain the chiral carbon present in the sibutramine skeleton. The metabolites identified included mono-desmethylsibutramine (nor-sibutramine), bi-desmethylsibutramine (nor-nor-sibutramine), and the corresponding hydroxylated compounds, the hydroxylation taking place either on the cyclobutane or on the isopropyl chain. The excretion profiles of the different metabolites were also evaluated. From an analytical point of view, the method can be applied to different fields of forensic analytical toxicology, including anti-doping analysis. Although the lack of certified reference materials does not allow a precise determination of the limits of detection (LODs) of all the sibutramine metabolites, an estimation taking into account the response factor of similar compounds ensures that all metabolites are still clearly detectable in a range of concentrations between 10 and 50 ng/mL, thus satisfying the minimum required performance limits (MRPLs) of the World Anti-Doping Agency (WADA). PMID:17154357

Strano-Rossi, Sabina; Colamonici, Cristiana; Botrè, Francesco



Short-Time-Response measurements of nitrogen dioxide and peroxyacetyl nitrate by fast capillary gas chromatography with luminol detection.  

SciTech Connect

The interaction of hydrocarbons and nitrogen oxides in sunlight to produce photochemical smog has been well studied over the years. In the past, the workhorse for the measurement of NO{sub 2}and NO was the chemiluminescent reaction with ozone. This method has detection limits of approximately 0.5 ppb in most commercial instruments, but it cannot detect NO{sub 2} directly; the instrument detects NO and uses hot catalytic surfaces to decompose all other nitrogen oxides (including NO{sub 2}) to NO for detection (l). The main problem with the method is the inherent difficulty in detecting excited NO{sub 2}, which emits over a broad region beginning at approximately 660 nm and has a maximum at 1270 nm, thus requiring a red-shifted photomultiplier for detection. The use of luminol for direct chemiluminescent detection of NO{sub 2} was demonstrated to have greater inherent sensitivity (detection limits of 5 ppt) than the indirect ozone chemiluminescence detection (2). In the luminol system, a gas-liquid reaction leads to light emission with a maximum at approximately 425 nm, at the maximum sensitivity for most photomultiplier tubes. This emission is responsible for the increased detection sensitivities. The biggest problem with this method for direct measurement of NO{sub 2} has been interference due to other soluble oxidants, particularly peroxyacyl nitrates (PANs).

Marley, N. A.; Gaffney, J. S.; Drayton, P. J.



Application of different analytical methods for determination of volatile chlorination by-products in drinking water.  


Four analytical methods have been applied for the determination of volatile chlorination by-products in drinking water, based on the following techniques: liquid-liquid extraction-gas chromatography-electron capture detection (LLE-GC-ECD); liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS); purge and trap-gas chromatography-mass spectrometry (purge and trap-GC-MS); and headspace-gas chromatography-mass spectrometry (headspace-GC-MS). The compounds studied were trihalomethanes, haloacetonitriles, haloketones, chloral hydrate and chloropicrin. LLE-GC-ECD method proved to be the most sensitive for determination of all compounds studied, followed by LLE-GC-MS. Purge and trap-GC-MS method gave good results in the case of trihalomethanes, but had high detection limits for the other volatile chlorination by-products. Headspace-GC-MS method had acceptable recoveries for trihalomethanes, but the detection limits were higher. PMID:18968548

Nikolaou, Anastasia D; Lekkas, Themistokles D; Golfinopoulos, Spyros K; Kostopoulou, Maria N



Determination of primary active constituents in Cannabis preparations by high-resolution gas chromatography\\/flame ionization detection and high-performance liquid chromatography\\/UV detection  

Microsoft Academic Search

For a complete quantitative analysis of primary active constituents in Cannabis preparations ?9-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN), we have compared two different chromatographic techniques, high-resolution gas chromatography (HRGC)\\/flame ionization detection (FID) and high-performance liquid chromatography (HPLC)\\/UV. The two different methods have been validated using crude drug (hashish) with methyloleate and tetraphenylethylene as internal standard for HRGC\\/FID and HPLC\\/UV,

Veniero Gambaro; Lucia Dell’Acqua; Fiorenza Farè; Rino Froldi; Elisa Saligari; Giovanna Tassoni



Detection of non-milk fat in milk fat by gas chromatography and linear discriminant analysis.  


Gas chromatography was utilized to determine triacylglycerol profiles in milk and non-milk fat. The values of triacylglycerol were subjected to linear discriminant analysis to detect and quantify non-milk fat in milk fat. Two groups of milk fat were analyzed: A) raw milk fat from the central region of Mexico (n = 216) and B) ultrapasteurized milk fat from 3 industries (n = 36), as well as pork lard (n = 2), bovine tallow (n = 2), fish oil (n = 2), peanut (n = 2), corn (n = 2), olive (n = 2), and soy (n = 2). The samples of raw milk fat were adulterated with non-milk fats in proportions of 0, 5, 10, 15, and 20% to form 5 groups. The first function obtained from the linear discriminant analysis allowed the correct classification of 94.4% of the samples with levels <10% of adulteration. The triacylglycerol values of the ultrapasteurized milk fats were evaluated with the discriminant function, demonstrating that one industry added non-milk fat to its product in 80% of the samples analyzed. PMID:19389942

Gutiérrez, R; Vega, S; Díaz, G; Sánchez, J; Coronado, M; Ramírez, A; Pérez, J; González, M; Schettino, B



Direct estimation of carbaryl by gas liquid chromatography with nitrogen phosphorus detection.  


A simple and efficient analytical method was standardized for the estimation of residues of carbaryl in various substrates comprising grape berries, kinnow pulps, kinnow rind and soil. The samples were refluxed using mixture of methanol: 0.5 N HCl (1:1 v/v); diluted with brine solution, partitioned into chloroform and dried over anhydrous sodium sulfate. Further the samples were treated with anhydrous magnesium sulfate and primary secondary amine. Final clear extracts were concentrated under vacuum and reconstituted the volume into acetone. The residues were estimated directly on gas liquid chromatograph equipped with nitrogen phosphorus detection system equipped with a capillary column packed with 5 % diphenyl 95 % dimethyl polysiloxane non-polar phase. A consistent recovery from 82 % to 97 % for carbaryl was observed when samples were spiked at levels ranging from 0.05 to 1.00 mg kg(-1). The limit of quantification of the method was worked out to be 0.05 mg kg(-1) for grape berries, kinnow pulp, kinnow rind and soil. PMID:22487961

Battu, Raminderjit Singh; Mandal, Kousik; Urvashi; Pandher, Suneet; Takkar, Reenu; Singh, Balwinder



Development of Oxide Semiconductor Thick Film Gas Sensor for the Detection of Total Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

After an amendment of Building Standards Law in 2003, the installation of the ventilator is compulsory in the newly built house. Because many persons suffer from indoor-air pollutants caused by the volatile organic compounds (VOCs). The final purpose of this research is to develop the gas sensor which can monitor the gross weight of VOC gases indoors and then to control the ventilator efficiently using the sensor. In order to develop the sensor which detects total VOC, the responses of 4 oxide semiconductor materials to 37 kinds of VOC gases were studied. Those materials showed small responses to halogenated and aliphatic hydrocarbon gases. As a result of improving the response to these gases, among 4 metal oxides examined, SnO2 and WO3 showed high sensitivities by the addition of Pd and Pt. The sensing properties of SnO2 for halogenated hydrocarbon gases were extremely improved by the addition of 0.5wt% Pd. Also, the sensing properties of SnO2 for aliphatic hydrocarbon gases were improved by the addition of 0.7wt% Pt. In addition, the doubly promoted element, Pt(0.5wt%)-Pd(0.5wt%)-SnO2, showed a large response to many kinds of VOC gases examined.

Kadosaki, Masahiro; Sakai, Yuichi; Tamura, Ikuo; Matsubara, Ichiro; Itoh, Toshio


Nonlinear Bayesian Algorithms for Gas Plume Detection and Estimation from Hyper-spectral Thermal Image Data  

SciTech Connect

This paper presents a nonlinear Bayesian regression algorithm for the purpose of detecting and estimating gas plume content from hyper-spectral data. Remote sensing data, by its very nature, is collected under less controlled conditions than laboratory data. As a result, the physics-based model that is used to describe the relationship between the observed remotesensing spectra, and the terrestrial (or atmospheric) parameters that we desire to estimate, is typically littered with many unknown "nuisance" parameters (parameters that we are not interested in estimating, but also appear in the model). Bayesian methods are well-suited for this context as they automatically incorporate the uncertainties associated with all nuisance parameters into the error estimates of the parameters of interest. The nonlinear Bayesian regression methodology is illustrated on realistic simulated data from a three-layer model for longwave infrared (LWIR) measurements from a passive instrument. This shows that this approach should permit more accurate estimation as well as a more reasonable description of estimate uncertainty.

Heasler, Patrick G.; Posse, Christian; Hylden, Jeff L.; Anderson, Kevin K.



Coupling gas chromatography and electronic nose detection for detailed cigarette smoke aroma characterization.  


Aroma characterization of whole cigarette smoke samples using sensory panels or electronic nose (E-nose) devices is difficult due to the masking effect of major constituents and solvent used for the extraction step. On the other hand, GC in combination with olfactometry detection does not allow to study the delicate balance and synergetic effect of aroma solutes. To overcome these limitations a new instrumental set-up consisting of heart-cutting gas chromatography using a capillary flow technology based Deans switch and low thermal mass GC in combination with an electronic nose device is presented as an alternative to GC-olfactometry. This new hyphenated GC-E-nose configuration is used for the characterization of cigarette smoke aroma. The system allows the transfer, combination or omission of selected GC fractions before injection in the E-nose. Principal component analysis (PCA) and discriminant factor analysis (DFA) allowed clear visualizing of the differences among cigarette brands and classifying them independently of their nicotine content. Omission and perceptual interaction tests could also be carried out using this configuration. The results are promising and suggest that the GC-E-nose hyphenation is a good approach to measure the contribution level of individual compounds to the whole cigarette smoke. PMID:25260341

Rambla-Alegre, Maria; Tienpont, Bart; Mitsui, Kazuhisa; Masugi, Eri; Yoshimura, Yuta; Nagata, Hisanori; David, Frank; Sandra, Pat



High Sensitivity Gas Detection Using a Macroscopic Three-Dimensional Graphene Foam Network  

NASA Astrophysics Data System (ADS)

Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH3 and NO2 in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation.

Yavari, Fazel; Chen, Zongping; Thomas, Abhay V.; Ren, Wencai; Cheng, Hui-Ming; Koratkar, Nikhil



High sensitivity gas detection using a macroscopic three-dimensional graphene foam network.  


Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH(3) and NO(2) in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation. PMID:22355681

Yavari, Fazel; Chen, Zongping; Thomas, Abhay V; Ren, Wencai; Cheng, Hui-Ming; Koratkar, Nikhil



Remote detection NMR imaging of gas phase hydrogenation in microfluidic chips.  


The heterogeneous hydrogenation reaction of propene into propane in microreactors is studied by remote detection (RD) nuclear magnetic resonance (NMR). The reactors consist of 36 parallel microchannels (50 × 50 ?m(2) cross sections) coated with a platinum catalyst. We show that RD NMR is capable of monitoring reactions with sub-millimeter spatial resolution over a field-of-view of 30 × 8 mm(2) with a steady-state time-of-flight time resolution in the tens of milliseconds range. The method enables the visualization of active zones in the reactors, and time-of-flight is used to image the flow velocity variations inside the reactor. The overall reaction yields determined by NMR varied from 10% to 50%, depending on the flow rate, temperature and length of the reaction channels. The reaction yield was highest for the channels with the lowest flow velocity. Propane T1 relaxation time in the channels, estimated by means of RD NMR images, was 270 ± 18 ms. No parahydrogen-induced polarization (PHIP) was observed in experiments carried out using parahydrogen-enriched H2, indicating fast spreading of the hydrogen atoms on the sputtered Pt surface. In spite of the low concentration of gases, RD NMR made imaging of gas phase hydrogenation of propene in microreactors feasible, and it is a highly versatile method for characterizing on-chip chemical reactions. PMID:23435499

Zhivonitko, Vladimir V; Telkki, Ville-Veikko; Leppäniemi, Jarmo; Scotti, Gianmario; Franssila, Sami; Koptyug, Igor V



Detection of D-^3He Fusion ?-Rays using Gas Cherenkov Detectors  

NASA Astrophysics Data System (ADS)

The high-energy ?-ray from ^3He(d,?)^5Li reactions has drawn the attention of the nuclear physics and fusion community as a diagnostic signature to study the ^5Li nuclear structure and the D-^3He fusion reaction. In the past, the D-^3He ?-rays have been measured via accelerator-based beam-target experiments and recently in tokamak-based fusion reactors. In this work, we report the detection of D-^3He fusion ?-rays generated from inertial confinement fusion (ICF) implosions at the OMEGA laser facility. The ?-ray signal observed using Gas Cherenkov Detectors (GCD) is proportional to the independently measured 14.7-MeV fusion proton yield and provides a high-bandwidth alternative to fusion protons for D-^3He burn-history measurements. By comparing ?-rays from D-^3He and D-T implosions, we were able to examine (1) similarities in the ?-ray spectra of D-^3He and D-T and (2) disparities in the ?-to-particle branching ratios of D-^3He and D-T. This experimental work motivates further theoretical investigation of the multichannel ^5Li- and ^5He-system.

Kim, Y.; Herrmann, H. W.; Mack, J. M.; Young, C. S.; Hale, G. M.; Evans, S. C.; Sedillo, T. J.; Cahill, A.; Horsfield, C. J.; Rubery, M. S.; Grafil, E.; Stoeffl, W.; Waugh, C.; Rinderknecht, H. G.; Frenje, J. A.; Petrasso, R. D.; Miller, E. Kirk



Multiparametric sensor based on DBR porous silicon for detection of ethanol gas  

Microsoft Academic Search

We are here concerned with fabrication possibility of multiparametric gas sensor based on porous silicon. In order to use the porous silicon as a gas sensor, we made the DBR (distributed Bragg reflector) porous silicon onto silicon wafer and monitored the change of three parameters during exposure of DBR porous silicon to ethanol gas. The sensing parameters were the shift

Han-Jung Kim; Young-You Kim; Ki-Won Lee



Gas Chromatography Analysis with Olfactometric Detection (GC-O) as a Useful Methodology for Chemical Characterization of Odorous Compounds  

PubMed Central

The gas chromatography-olfactometry (GC-O) technique couples traditional gas chromatographic analysis with sensory detection in order to study complex mixtures of odorous substances and to identify odor active compounds. The GC-O technique is already widely used for the evaluation of food aromas and its application in environmental fields is increasing, thus moving the odor emission assessment from the solely olfactometric evaluations to the characterization of the volatile components responsible for odor nuisance. The aim of this paper is to describe the state of the art of gas chromatography-olfactometry methodology, considering the different approaches regarding the operational conditions and the different methods for evaluating the olfactometric detection of odor compounds. The potentials of GC-O are described highlighting the improvements in this methodology relative to other conventional approaches used for odor detection, such as sensoristic, sensorial and the traditional gas chromatographic methods. The paper also provides an examination of the different fields of application of the GC-O, principally related to fragrances and food aromas, odor nuisance produced by anthropic activities and odorous compounds emitted by materials and medical applications. PMID:24316571

Brattoli, Magda; Cisternino, Ezia; Dambruoso, Paolo Rosario; de Gennaro, Gianluigi; Giungato, Pasquale; Mazzone, Antonio; Palmisani, Jolanda; Tutino, Maria



Rapid and selective detection of acetone using hierarchical ZnO gas sensor for hazardous odor markers application.  


Hierarchical nanostructured ZnO dandelion-like spheres were synthesized via solvothermal reaction at 200°C for 4h. The products were pure hexagonal ZnO with large exposure of (002) polar facet. Side-heating gas sensor based on hierarchical ZnO spheres was prepared to evaluate the acetone gas sensing properties. The detection limit to acetone for the ZnO sensor is 0.25ppm. The response (Ra/Rg) toward 100ppm acetone was 33 operated at 230°C and the response time was as short as 3s. The sensor exhibited remarkable acetone selectivity with negligible response toward other hazardous gases and water vapor. The high proportion of electron depletion region and oxygen vacancies contributed to high gas response sensitivity. The hollow and porous structure of dandelion-like ZnO spheres facilitated the diffusion of gas molecules, leading to a rapid response speed. The largely exposed (002) polar facets could adsorb acetone gas molecules easily and efficiently, resulting in a rapid response speed and good selectivity of hierarchical ZnO spheres gas sensor at low operating temperature. PMID:24892776

Jia, Qianqian; Ji, Huiming; Zhang, Ying; Chen, Yalu; Sun, Xiaohong; Jin, Zhengguo



Sputtered gas-phase dianions detected by high-sensitivity mass spectrometry  

NASA Astrophysics Data System (ADS)

The detection of small doubly-charged molecular anions by means of highly sensitive mass spectrometry is discussed. The production of these gas-phase dianions is accomplished by sputtering the specimen with Cs + ions with an energy of a few keV. It is demonstrated that dianions can be detected most easily when the molecular ion has an odd total mass; then, the dianions will show up at half-integral mass numbers in the mass spectrum. In addition, the agreement of the relative abundances of several isotopomers of a dianion with the nominal isotopic pattern corroborates the identification of a dianionic species in the mass spectrum. These features are exemplified by monitoring mixed silicon-oxygen dianions of the general form OO52-[28], Sn2-[29], SiC62-[30], BeCn2-[31], and PtX62- (X = F, Cl, Br) [32]. More recent work of this group investigated the existence of long-lived dianions containing tetrahedrally coordinated oxygen atoms, namely, O(C)42- and O(BN)42-[33], of cyclic carbon cluster dianions [34], of tetraborates [35], of derivatives of the closo-hexaborate dianion BH62-[36], and of aromatic dianions [37]. Apart from identifying (meta)stable dianions, these computations indicated a possible general formation principle: small dianions are expected to be particularly stable if they consist of a central, at least partially positively charged atom and several equivalent negatively charged ligands [2,6,30,38]. Furthermore, it was pointed out [31,39,40] that for multiply charged anions a repulsive Coulomb barrier for electron emission exists which may result in small metastable dianions which can be detected by mass spectrometry. In fact, the existence of such a Coulomb barrier was inferred from various experiments [41-47]. Apart from dianions, Cederbaum and coworkers studied different small MCAs [19,24,25,48-50]. Theoretical work by other groups [51-59] corroborated and diversified these results. Following the experimental detection of Cn2-[12], several different types of other dianions were produced by means of sputtering: SiCn2- ( n = 6, 8, 10) [60], BeCn2- (4 ? n ? 14) [61,62], OCn2- (5 ? n ? 19) [63,64], SCn2- (6 ? n ? 18) [65], BeF42- and, MgF42-[66], CaF42-[67], HfF62-[68], ZrF62-[65], LiF32-[69], BeOn2- ( n = 4, 6), and CuBeO42-[70], as well as a few others [65,71]. However, also a considerable number of unsuccessful searches for dianions were reported [13,65,68,72]. Apart from sputtering, other ways of dianion formation were employed: Oxygen cluster (O)n2- ( n = 3, 5, 7, 9) were formed by electron attachment to an O 2 beam [73]. Electrospray ionization was used to produce various dianions, e.g., SO42-·nHO, SO62-·nHO, and SO82-·nHO[74], MX42- (M = Pd, Pt; X = Cl, Br) [43,44,75], MX62- (M = Re, Os, Ir, Pt; X = Cl, Br) [43,76], ZrF62-[77] or aliphatic dicarboxylate dianions [78-80]. While fullerene dianions (with n = 70-124) [81] and even C603- and C604-[82] could be produced by electrospray mass spectrometry, no C602- dianions were observed in these studies. Doubly-charged C602- and C702- ions have been produced also by laser desorption[83,84] or by collisions with Na atoms [85] whereas CF482-[41], C842-[42], C762-[86], and C702-[87] could be formed by electron attachment. More recently, dianions and even trianions of large metal clusters (some 30 or more constituents) could be produced by laser ablation [88] or by metal evaporation and subsequent electron attachment[89-92]. The aim of the present work is to discuss the production of dianions in the gas phase by sputtering and to describe their detection both in conventional mass spectrometers, operated at ion-beam energies of a few keV and in high-energy mass spectrometry. For the former, the pertinent aspects will be illustrated by means of a new class of molecular dianions, OO72-. Three distinct peaks at half-integral mass numbers are seen in the spectrum, at 98.5, 99.5, and 100.5 amu; their relative intensities are 1:9.0 × 10 -2:1.7 × 10 -3. Following the above argument, we can assume that these are caused by dianions with an odd total mass. Bot

Gnaser, Hubert; Golser, Robin



Warm-Hot Gas in and around the Milky Way: Detection and Implications of OVII Absorption toward LMC X-3  

E-print Network

X-ray absorption lines of highly-ionized species such as OVII at about zero redshift have been firmly detected in the spectra of several active galactic nuclei. However, the location of the absorbing gas remains a subject of debate. To separate the Galactic and extragalactic contributions to the absorption, we have obtained Chandra LETG-HRC and FUSE observations of the black hole X-ray binary LMC X--3. A joint analysis of the detected OVII and Ne IX Kalpha lines, together with the non-detection of the OVII Kbeta and OVIII Kalpha lines, gives the measurements of the temperature, velocity dispersion, and hot oxygen column density. The X-ray data also allow us to place a 95% confidence lower limit to the Ne/O ratio as 0.14. The OVII line centroid and its relative shift from the Galactic OI Kalpha absorption line, detected in the same observations, are inconsistent with the systemic velocity of LMC X--3 ($+310 {\\rm km s^{-1}}$). The far-UV spectrum shows OVI absorption at Galactic velocities, but no OVI absorption is detected at the LMC velocity at $> 3\\sigma$ significance. Both the nonthermal broadening and the decreasing scale height with the increasing ionization state further suggest an origin of the highly-ionized gas in a supernova-driven galactic fountain. In addition, we estimate the warm and hot electron column densities from our detected OVII Kalpha line in the LMC X--3 X-ray spectra and from the dispersion measure of a pulsar in the LMC vicinity. We then infer the O/H ratio of the gas to be $\\gtrsim 8 \\times 10^{-5}$, consistent with the chemically-enriched galactic fountain scenario. We conclude that the Galactic hot interstellar medium should in general substantially contribute to zero-redshift X-ray absorption lines in extragalactic sources.

Q. D. Wang; Y. Yao; T. M. Tripp; T. -T. Fang; W. Cui; F. Nicastro; S. Mathur; R. J. Williams; L. Song; R. Croft



A quartz-enhanced photoacoustic sensor for H2S trace-gas detection at 2.6 ?m  

NASA Astrophysics Data System (ADS)

We report on the realization of a quartz-enhanced photoacoustic (QEPAS) sensor for measurement of H2S gas traces. A distributed feedback diode laser working at 2.64 µm wavelength has been coupled to an acoustic detection module composed of a quartz tuning fork and a micro-resonator system, and the QEPAS signal has been optimized in terms of gas sample pressure and laser frequency modulation depth. The sensor shows a very good linearity with respect to the H2S concentration. We performed an Allan-Werle variance analysis to investigate the sensor long-term stability, and we reached a detection limit of four parts per million for 1-s integration time and 500 parts per billion in 60-s integration time. The realized QEPAS sensor represents a good compromise between performance and handiness, in view of a fully portable device.

Viciani, S.; Siciliani de Cumis, M.; Borri, S.; Patimisco, P.; Sampaolo, A.; Scamarcio, G.; De Natale, P.; D'Amato, F.; Spagnolo, V.



Hyphenation of a near-infrared Echelle spectrometer to a microplasma for element-selective detection in gas chromatography.  


The coupling of a near-infrared Echelle spectrometer (NIRES) with a gas chromatograph for element-selective detection is introduced. The miniaturized capacitive plasma device is operated at a frequency of 40.68 MHz and is mounted directly on an Hewlett-Packard HP6890 GC. First results with a mixture of halogenated standard compounds are presented and discussed in terms of the advantages and problems with this system. PMID:11798094

Cziesla, K; Platzer, B; Okruss, M; Florek, S; Otto, M



Acoustic detection of gas emissions within the submerged section of the North Anatolian Fault Zone in the Sea of Marmara  

Microsoft Academic Search

The 38 kHz, single beam, echo-sounder SIMRAD EK-60 was operated during the Marnaut cruise (May-June 2007) onboard the RV L'Atalante to detect acoustic anomalies related to the presence of gas bubbles in the water column. In the south Cinarcik Basin, strong acoustic anomalies have been found along N140 normal faults within a 3 km wide swath oriented N100. The swath

L. Géli; P. Henry; S. Dupré; D. Voelker; T. Zitter; X. Le Pichon; M. Tryon; N. Cagatay



CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5-4 ?m range TEC mercury-cadmium-telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm-1, a 1 ? minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.

Krzempek, Karol; Jahjah, Mohammad; Lewicki, Rafa?; Stefa?ski, Przemys?aw; So, Stephen; Thomazy, David; Tittel, Frank K.



CW DFB RT diode laser based sensor for trace-gas detection of ethane using novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable laser diode absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS) as the detection technique. TDLAS was performed with an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm. For an interference free C2H6 absorption line located at 2976.8 cm-1 a 1? minimum detection limit of 130 pptv with a 1 second lock-in amplifier time constant was achieved.

Jahjah, Mohammad; Lewicki, Rafal; Tittel, Frank K.; Krzempek, Karol; Stefanski, Przemyslaw; So, Stephen; Thomazy, David



An optical sensor for detecting the contact location of a gas-liquid interface on a body  

NASA Astrophysics Data System (ADS)

An optical sensor for detecting the dynamic contact location of a gas-liquid interface along the length of a body is described. The sensor is developed in the context of applications to supercavitating bodies requiring measurement of the dynamic cavity contact location; however, the sensing method is extendable to other applications as well. The optical principle of total internal reflection is exploited to detect changes in refractive index of the medium contacting the body at discrete locations along its length. The derived theoretical operation of the sensor predicts a signal attenuation of 18 dB when a sensed location changes from air-contacting to water-contacting. Theory also shows that spatial resolution (d) scales linearly with sensor length (Ls) and a resolution of 0.01Ls can be achieved. A prototype sensor is constructed from simple components and response characteristics are quantified for different ambient light conditions as well as partial wetting states. Three methods of sensor calibration are described and a signal processing framework is developed that allows for robust detection of the gas-liquid contact location. In a tank draining experiment, the prototype sensor resolves the water level with accuracy limited only by the spatial resolution, which is constrained by the experimental setup. A more representative experiment is performed in which the prototype sensor accurately measures the dynamic contact location of a gas cavity on a water tunnel wall.

Belden, Jesse; Jandron, Michael



Gas Chromatographic Analysis of Cyclophosphamide in Plasma and Tissues Using Nitrogen-Phosphorus Detection  

Microsoft Academic Search

A gas chromatographic method for the analysis of cyclophosphamide in plasma, blood, and organ tissues is described. This method involves extraction of aliquots of plasma or tissue homo-genate in alkaline condition with ether. The extracted drug is derivatized with heptafluorobutyric anhydride followed by gas chromatographic separation via a glass column of 183 cm × 2 mm i. d. packed with

M. S. Balachandran Nayar; Lo-Yin Lin; Suk Han Wan; Kenneth K. Chan



Gas chromatographic method for detection of urinary sucralose: application to the assessment of intestinal permeability  

Microsoft Academic Search

We developed a capillary column gas chromatography (CCGC) method for the measurement of urinary sucralose (S) and three other sugar probes including, sucrose, lactulose (L) and mannitol (M) for use in in vivo studies of intestinal permeability. We compared the capillary method with a packed column gas chromatography (PCGC) method. We also investigated a possible role for sucralose as a

Ashkan Farhadi; Ali Keshavarzian; Earle W Holmes; Jeremy Fields; Lei Zhang; Ali Banan



Detection and quantification of fugitive emissions from Colorado oil and gas production operations using remote monitoring  

EPA Science Inventory

Western states contain vast amounts of oil and gas production. For example, Weld County Colorado contains approximately 25,000 active oil and gas well sites with associated production operations. There is little information on the air pollutant emission potential from this source...


Fluorescent-dye-doped sol-gel sensor for highly sensitive carbon dioxide gas detection below atmospheric concentrations.  


Optical fluorescence sol-gel sensors have been developed for the detection of carbon dioxide gas in the 0.03-30% range with a detection limit of 0.008% (or 80 ppm) and a quantitation limit of 0.02% (or 200 ppm) CO(2). Sol-gels were spin-coated on glass slides to create an organically modified silica-doped matrix with the 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) fluorescent indicator. The luminescence intensity of the HPTS indicator (513 nm) is quenched by CO(2), which protonates the anionic form of HPTS. An ion pair technique was used to incorporate the lipophilic dye into the hydrophilic sol-gel matrix. TiO(2) particles (<5 microm diameter) were added to induce Mie scattering and increase the incident light interaction with the sensing film, thus increasing the signal-to-noise ratio. Moisture-proof overcoatings have been used to maintain a constant level of water inside the sensor films. The optical sensors are inexpensive to prepare and can be easily coupled to fiber optics for remote sensing capabilities. A fiber-optic bundle was used for the gas detection and shown to work as part of a multianalyte platform for simultaneous detection of multiple analytes. The studies reported here resulted in the development of sol-gel optical fluorescent sensors for CO(2) gas with sensitivity below that in the atmosphere (ca. 387 ppm). These sensors are a complementary approach to current FT-IR measurements for real-time carbon dioxide detection in environmental applications. PMID:20038093

Dansby-Sparks, Royce N; Jin, Jun; Mechery, Shelly J; Sampathkumaran, Uma; Owen, Thomas William; Yu, Bi Dan; Goswami, Kisholoy; Hong, Kunlun; Grant, Joseph; Xue, Zi-Ling



Realization of rapid debugging for detection circuit of optical fiber gas sensor: Using an analog signal source  

NASA Astrophysics Data System (ADS)

An optical fiber gas sensor mainly consists of two parts: optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer (SCM), an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

Tian, Changbin; Chang, Jun; Wang, Qiang; Wei, Wei; Zhu, Cunguang



A New Method for Ultrasound Detection of Interfacial Position in Gas-Liquid Two-Phase Flow  

PubMed Central

Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe. PMID:24858961

Coutinho, Fábio Rizental; Ofuchi, César Yutaka; de Arruda, Lúcia Valéria Ramos; Jr., Flávio Neves; Morales, Rigoberto E. M.



Rapid analysis of ethanol and water in commercial products using ionic liquid capillary gas chromatography with thermal conductivity detection and/or barrier discharge ionization detection.  


Analysis of ethanol and water in consumer products is important in a variety of processes and often is mandated by regulating agencies. A method for the simultaneous quantitation of ethanol and water that is simple, accurate, precise, rapid, and cost-effective is demonstrated. This approach requires no internal standard for the quantitation of both ethanol and water at any/all levels in commercial products. Ionic liquid based gas chromatography (GC) capillary columns are used to obtain a fast analysis with high selectivity and resolution of water and ethanol. Typical run times are just over 3 min. Examination of the response range of water and ethanol with GC, thermal conductivity detection (TCD), and barrier ionization detection (BID) is performed. Quantitation of both ethanol and water in consumer products is accomplished with both TCD and BID GC detectors using a nonlinear calibration. Validation of method accuracy is accomplished by using standard reference materials. PMID:24527961

Weatherly, Choyce A; Woods, Ross M; Armstrong, Daniel W



Development of a Random Field Model for Gas Plume Detection in Multiple LWIR Images.  

SciTech Connect

This report develops a random field model that describes gas plumes in LWIR remote sensing images. The random field model serves as a prior distribution that can be combined with LWIR data to produce a posterior that determines the probability that a gas plume exists in the scene and also maps the most probable location of any plume. The random field model is intended to work with a single pixel regression estimator--a regression model that estimates gas concentration on an individual pixel basis.

Heasler, Patrick G.



Final design review report for the RMCS Flammable Gas Detection Interlock  

SciTech Connect

This report document the completion of the formal design review for the RMCS (Rotary Mode Core Sampling) flammable gas detector interlock. This hydrogen/flammable gas interlock, a proposed addition to the RMCS system portable exhauster, in intended to support core sampling operations in waste tanks requiring flammable gas controls. The objective of this review was to approve new drawings at the 100% design completion state. The conclusion reached by the review committee was that the design was acceptable and efforts should continue toward fabrication and delivery.

Corbett, J.E., Westinghouse Hanford



Detection of Gas Hydrates in Garden Banks and Keathley Canyon from Seismic Data  

E-print Network

(Vogt and Jung, 2002). Furthermore, landslides may set off large tsunamis (Bonde- vik et al., 1997; Ward, 2001) that threaten coastal lowlands. Apart from being a geological hazard, the worldwide presence of gas hydrates in continental margin...

Murad, Idris



Development of an electrical resistivity cone for the detection of gas hydrates in marine sediments  

E-print Network

onshore and offshore environments, as well as in permafrost and tropical regions. The presence of natural gas hydrates in marine sediments are of concern to geotechnical engineers for several reasons, including: (1) their effect on the load bearing...

McClelland, Martha Ann



Method and apparatus for noble gas atom detection with isotopic selectivity  


Apparatus and methods of operation are described for determining, with isotopic selectivity, the number of noble gas atoms in a sample. The analysis is conducted within an evacuated chamber which can be isolated by a valve from a vacuum pumping system capable of producing a pressure of 10.sup.-8 Torr. Provision is made to pass pulses of laser beams through the chamber, these pulses having wavelengths appropriate for the resonance ionization of atoms of the noble gas under analysis. A mass filter within the chamber selects ions of a specific isotope of the noble gas, and means are provided to accelerate these selected ions sufficiently for implantation into a target. Specific types of targets are discussed. An electron measuring device produces a signal relatable to the number of ions implanted into the target and thus to the number of atoms of the selected isotope of the noble gas removed from the gas sample. The measurement can be continued until a substantial fraction, or all, of the atoms in the sample have been counted. Furthermore, additional embodiments of the apparatus are described for bunching the atoms of a noble gas for more rapid analysis, and for changing the target for repetitive cycling of the gas in the chamber. The number of repetitions of the cyclic steps depend upon the concentration of the isotope of interest, the separative efficiency of the mass filter, etc. The cycles are continued until a desired selectivity is achieved. Also described are components and a method of operation for a pre-enrichment operation for use when an introduction of a total sample would elevate the pressure within the chamber to levels in excess of those for operation of the mass filter, specifically a quadrupole mass filter. Specific examples of three noble gas isotope analyses are described.

Hurst, G. Samuel (Oak Ridge, TN); Payne, Marvin G. (Harriman, TN); Chen, Chung-Hsuan (Knoxville, TN); Parks, James E. (Oak Ridge, TN)



Ultrasound detection of foreign body and gas contamination of a penetrating wound.  


We report a case in which ultrasonography (US) examination was used in the Emergency Department to reveal and diagnose gas contamination of a penetrating wound. Air microbubbles are extremely small and their typical distribution and movement are like those of "sparkling-wine microbubbles". US assessment of spontaneous disappearance of the air bubbles can distinguish a harmless traumatic nature of the wound from a life-threatening gas-producing bacterial infection. PMID:23397000

Testa, A; Giannuzzi, R; Zirio, G; La Greca, A; Silveri, N Gentiloni



Ultrasound detection of foreign body and gas contamination of a penetrating wound  

PubMed Central

We report a case in which ultrasonography (US) examination was used in the Emergency Department to reveal and diagnose gas contamination of a penetrating wound. Air microbubbles are extremely small and their typical distribution and movement are like those of “sparkling-wine microbubbles”. US assessment of spontaneous disappearance of the air bubbles can distinguish a harmless traumatic nature of the wound from a life-threatening gas-producing bacterial infection. PMID:23397000

Testa, A.; Giannuzzi, R.; Zirio, G.; La Greca, A.; Silveri, N. Gentiloni



Determination of antimony in environment samples by gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping.  


A novel method for the determination of antimony in environmental samples was developed with gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping. The stibine, generated from samples by borohydride reduction of antimony using flow injection technique, was separated by using a new gas-liquid separator, dried with an ice-salt cryogenic bath and concentrated in a glass U-tube immersed in liquid nitrogen. Re-vaporization of stibine based on its boiling point was achieved by allowing the tube to warm at room temperature. A gas phase chemiluminescence signal was produced during the ozonation of the hydride in a reflective chamber. Under optimal conditions, the proposed method was characterized by a wide linear calibration range from 1.0microgL(-1) to 10.0mgL(-1) with a detection limit of 0.18microgL(-1) (n=11). The relative standard deviation for 10.0microgL(-1) antimony was 3.56% (n=11) and the sampling rate was 15 samples h(-1). Blank signal was reduced by the purification of reagents and the interference from transition metal ions was eliminated by the addition of L-cysteine into samples. The method was applied to the determination of antimony in environmental samples with satisfactory results. PMID:20441930

Ye, Yousheng; Sang, Jianchi; Ma, Hongbing; Tao, Guanhong



Comparison on gas-sensing properties of single- and multi-layered SnO 2 nanostructures in drug-precursors detection  

Microsoft Academic Search

Systematic comparison on gas-sensing properties of single- and multi-layered SnO2 nanomaterials in drug-precursors detection from the aspects of gas-sensing response and kinetic adsorption\\/desorption process was presented for the first time. The SnO2 nanomaterials with single- and multi-layered structures assembled by numerous nanoparticles were prepared via a hydrothermal route using carbonaceous spheres as templates. In gas-sensing measurements, drug-precursors including aether and

Jinyun Liu; Yuteng Wan; Daoyang Yu; Fanli Meng; Zhen Jin; Lingtao Kong; Jinhuai Liu



Multiphase imaging of gas flow in a nanoporous material usingremote detection NMR  

SciTech Connect

Pore structure and connectivity determine how microstructured materials perform in applications such as catalysis, fluid storage and transport, filtering, or as reactors. We report a model study on silica aerogel using a recently introduced time-of-flight (TOF) magnetic resonance imaging technique to characterize the flow field and elucidate the effects of heterogeneities in the pore structure on gas flow and dispersion with Xe-129 as the gas-phase sensor. The observed chemical shift allows the separate visualization of unrestricted xenon and xenon confined in the pores of the aerogel. The asymmetrical nature of the dispersion pattern alludes to the existence of a stationary and a flow regime in the aerogel. An exchange time constant is determined to characterize the gas transfer between them. As a general methodology, this technique provides new insights into the dynamics of flow in porous media where multiple phases or chemical species may be present.

Harel, Elad; Granwehr, Josef; Seeley, Juliette A.; Pines, Alex



Gas sensors based on carbon nanoflake/tin oxide composites for ammonia detection.  


Carbon nanoflake (CNFL) was obtained from graphite pencil by using the electrochemical method and the CNFL/SnO2 composite material assessed its potential as an ammonia gas sensor. A thin film resistive gas sensor using the composite material was manufactured by the drop casting method, and the sensor was evaluated to test in various ammonia concentrations and operating temperatures. Physical and chemical characteristics of the composite material were assessed using SEM, TEM, SAED, EDS and Raman spectroscopy. The composite material having 10% of SnO2 showed 3 times higher sensor response and better repeatability than the gas sensor using pristine SnO2 nano-particle at the optimal temperature of 350°C. PMID:24473403

Lee, Soo-Keun; Chang, Daeic; Kim, Sang Wook



Acoustic detection of gas emissions within the submerged section of the North Anatolian Fault Zone in the Sea of Marmara  

NASA Astrophysics Data System (ADS)

The 38 kHz, single beam, echo-sounder SIMRAD EK-60 was operated during the Marnaut cruise (May-June 2007) onboard the RV L'Atalante to detect acoustic anomalies related to the presence of gas bubbles in the water column. In the south Cinarcik Basin, strong acoustic anomalies have been found along N140 normal faults within a 3 km wide swath oriented N100. The swath trend corresponds to the orientation of a buried fault system identified in MCS data (Carton and Singh, 2007). Ground-truthing of these anomalies with Nautile submersible enables the founding of gas seeps and bubbles emissions at seafloor. Acoustic anomalies are apparently weaker on the main fault scarp on the northern side of the Cinarcik Basin. In the Central High and Kumburgaz Basin, no acoustic anomalies were detected along the main fault trace. Instead, a cluster with very strong amplitude anomalies was identified at about 1 km away from the fault, on top of a broad anticline. On the Western High, a cluster of acoustic anomalies characterizes the top of an anticline located near 40°49'N, 28°46.8'E, where shallow gas hydrates have been sampled at unexpected water depth of 660 m, well outside the methane hydrate stability field. In the Tekirdag and Central basins, EK-60 lines were implemented along the fault scarps and the acoustic records indicate the presence of gas seeps at fault escarpments. This new set of data confirms previous results obtained with RV Le Suroit in September 2000 with a 112 kHz side-scan sonar towed 200 m above seafloor. Most active sites identified in 2000 were still active in 2007. We note that the only place where no acoustic anomaly was found on the main fault trace corresponds to the Central High and Kumburgaz Basin area. This segment did not rupture during the last century.

Géli, L.; Henry, P.; Dupré, S.; Voelker, D.; Zitter, T.; Le Pichon, X.; Tryon, M.; Cagatay, N.; Shipboard Science Party, M.



Detection of greenhouse-gas-induced climatic change. Progress report, 1 December 1992--30 June 1993  

SciTech Connect

The aims of the US Department of Energy`s Carbon Dioxide Research Program are to improve assessments of greenhouse-gas-induced climatic change and to define and reduce uncertainties through selected research. The main research areas covered by this proposal are (b), First Detection and (c) Supporting Data. The project will also include work under area (a), Modeling: specifically, analysis of climate forcing factors, the development and refinement of transient response climate models, and the use of instrumental data in validating General Circulating Models (GCMs).

Wigley, T.M.L.; Jones, P.D.



Fault detection and diagnosis for gas turbines based on a kernelized information entropy model.  


Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms. PMID:25258726

Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei



Fault Detection and Diagnosis for Gas Turbines Based on a Kernelized Information Entropy Model  

PubMed Central

Gas turbines are considered as one kind of the most important devices in power engineering and have been widely used in power generation, airplanes, and naval ships and also in oil drilling platforms. However, they are monitored without man on duty in the most cases. It is highly desirable to develop techniques and systems to remotely monitor their conditions and analyze their faults. In this work, we introduce a remote system for online condition monitoring and fault diagnosis of gas turbine on offshore oil well drilling platforms based on a kernelized information entropy model. Shannon information entropy is generalized for measuring the uniformity of exhaust temperatures, which reflect the overall states of the gas paths of gas turbine. In addition, we also extend the entropy to compute the information quantity of features in kernel spaces, which help to select the informative features for a certain recognition task. Finally, we introduce the information entropy based decision tree algorithm to extract rules from fault samples. The experiments on some real-world data show the effectiveness of the proposed algorithms. PMID:25258726

Wang, Weiying; Xu, Zhiqiang; Tang, Rui; Li, Shuying; Wu, Wei



Rapid, automated gas chromatographic detection of organic compounds in ultra-pure water  

Microsoft Academic Search

An automated gas chromatography was used to analyze water samples contaminated with trace (parts-per-billion) concentrations of organic analytes. A custom interface introduced the liquid sample to the chromatography. This was followed by rapid chromatographic analysis. Characteristics of the analysis include response times less than one minute and automated data processing. Analytes were chosen based on their known presence in the




REVIEW OF METHODS OF OPTICAL GAS Detection by Direct Optical Spectroscopy, with Emphasis on Correlation Spectroscopy  

NASA Astrophysics Data System (ADS)

This chapter reviews the development of optical gas sensors, starting with an initial emphasis on optical-fibre remoted techniques and finishing with a particular focus on our own group's work on highly selective methods using correlation spectroscopy. This latter section includes extensive theoretical modelling of a correlation spectroscopy method, and compares theory with practice for a CO2 sensor.

Dakin, John P.; Chambers, Paul


Detection of soot particles in gas turbine engine combustion gases using nonintrusive FTIR spectroscopy  

Microsoft Academic Search

Fourier transform IR (FTIR) spectroscopy for making non- intrusive measurements of gas turbine exhaust gases and laser induced incandescence for measuring soot content are being evaluated in EU Brite EuRam project AEROJET. Soot concentrations in modern aero-engine exhausts are very low with mean particle sizes < 100 nm. The standard extractive filter paper soot measurement gives results expressed in terms

Moira Hilton; John D. Black



Separation and Detection of Toxic Gases with a Silicon Micromachined Gas Chromatography System  

NASA Technical Reports Server (NTRS)

A miniature gas chromatography (GC) system was designed and fabricated using silicon micromachining and integrated circuit (IC) processing techniques. The silicon micromachined gas chromatography system (SMGCS) is composed of a miniature sample injector that incorporates a 10 microliter sample loop; a 0.9 meter long, rectangular shaped (300 micrometer width and 10 micrometer height) capillary column coated with a 0.2 micrometer thick copper phthalocyanine (CuPc) stationary phase; and a dual detector scheme based upon a CuPc-coated chemiresistor and a commercially available 125 micrometer diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC column, the column itself, and the dual detector cavity. A novel IC thin-film processing technique was developed to sublime the CuPc stationary phase coating on the column walls that were micromachined in the host silicon wafer substrate and Pyrex (r) cover plate, which were then electrostatically bonded together. The SMGCS can separate binary gas mixtures composed of parts-per-million (ppm) concentrations of ammonia (NH3) and nitrogen dioxide (NO2) when isothermally operated (55-80 degrees C). With a helium carrier gas and nitrogen diluent, a 10 microliter sample volume containing ammonia and nitrogen dioxide injected at 40 psi ((2.8 x 10(exp 5)Pa)) can be separated in less than 30 minutes.

Kolesar, Edward S.; Reston, Rocky R.



Methyl mercaptan and dimethyl disulfide production from methionine by Proteus species detected by head-space gas-liquid chromatography.  

PubMed Central

Head-space gas-liquid chromatography and mass spectrometry were used to detect and identify products formed by Proteus vulgaris, P. mirabilis, P. morganii, and P. rettgeri from a defined medium supplemented with either phenylalanine, methionine, valine, leucine, histidine, lysine, ornithine, threonine, asparagine, aspartic acid, or tryptophan. In a detailed study of the products formed by 68 strains of Proteus spp. from L-methionine, the production of large amounts of both dimethyl disulfide and methyl mercaptan was found to be a characteristic of the genus. Both sulfur products appeared within a few hours of inoculation. Dimethyl disulfide was a more sensitive indicator of growth than the spectrometric determination of optical density. This suggests that it could be useful for the rapid, automated detection of any species of Proteus. PMID:332705

Hayward, N J; Jeavons, T H; Nicholson, A J; Thornton, A G



Speciation of organomercurials in biological and environmental samples by gas chromatography with microwave-induced plasma atomic emission detection.  


The applicability of a commercial microwave-induced plasma atomic emission detector with capillary gas chromatography for mercury speciation in environmental samples was examined. The chromatographic conditions were optimized in order to obtain an adequate resolution of the methylmercury peak vs. interfering carbon signals. Under the proposed operational conditions, the detection limit (signal-to-noise ratio = 3) was 1.2 pg with a linear range of 1-40 ng ml-1 (as methylmercury in samples). Certified reference material (DORM-1) was used to evaluate the accuracy. The results of the proposed procedure were compared with those obtained by means of the usual GC method with electron-capture detection. PMID:7952014

Carro-Díaz, A M; Lorenzo-Ferreira, R A; Cela-Torrijos, R



Detection of clenbuterol at trace levels in doping analysis using different gas chromatographic-mass spectrometric techniques.  


This study demonstrates the development of a gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS-MS) assay to detect clenbuterol in human urine and the comparison of this method with GC-MS techniques and gas chromatography-high resolution mass spectrometry (GC-HRMS) techniques. Urine samples were hydrolyzed with ?-glucuronidase, extracted with methyl tert-butyl ether and dried under nitrogen. The derivative reagent was N-methyl-N-(trimethylsilyl)-trifluoroacetamide with NH4I and was analyzed by GC-MS, GC-MS-MS and GC-HRMS. A validation study was conducted by GC-MS-MS. The analyses of clenbuterol using different mass spectrometric techniques were compared. The limit of detection (LOD) for clenbuterol in human urine was 2 ng/mL by GC-MS (selected ion monitoring mode: SIM mode), 0.06 ng/mL by GC-HRMS and 0.03 ng/mL by GC-MS-MS, respectively, while the LOD by GC-HRMS was 0.06. With GC-MS-MS, the intra-assay and inter-assay precisions were less than 15%, the recoveries were 86 to 112% and the linear range was 0.06 to 8.0 ng/mL. The GC-MS under SIM mode can be used as a screening tool to detect clenbuterol at trace levels in human urine. The GC-MS-MS and GC-HRMS methods can confirm clenbuterol when its concentration is below 2 ng/mL. The results demonstrate that the GC-MS-MS method is quite sensitive, specific and reliable for the detection of clenbuterol in doping analysis. PMID:23042839

Yang, Sheng; Liu, Xin; Xing, Yanyi; Zhang, Dapeng; Wang, Shan; Wang, Xiaobing; Xu, Youxuan; Wu, Moutian; He, Zhenwen; Zhao, Jian



On the analysis of in-tube flaw-detection results characterizing the state of a trunk gas pipeline with corrosion flaws  

Microsoft Academic Search

Today, results of in-tube flaw detection (ITFD) are used mainly to solve routine problems of the provision of service reliability of operating gas pipelines (via the removal or selective repair of damaged pipes). However, the task of nondestructive testing consists in not only the detection of flaws but also in the determination of the principal causes of their appearance. This

V. A. Gorchakov; I. A. Dolgov; Yu. P. Surkov; V. G. Rybalko; A. Yu. Surkov



Establishing the limit of detection and the resolution limits of odorous sources in the environment for an array of metal oxide gas sensors  

Microsoft Academic Search

Odour identification with gas sensor arrays relies on two main parameters: the limit of detection, defined as the concentration of the analyte corresponding to the lowest detectable signal for the sensors, and the limit of resolution, defined for pair-wise comparisons of vapours, as the concentration levels below which a vapour can no longer be reliably recognised from another one on

Jacques Nicolas; Anne-Claude Romain



Detection of Potato Storage Disease via Gas Analysis: A Pilot Study Using Field Asymmetric Ion Mobility Spectrometry  

PubMed Central

Soft rot is a commonly occurring potato tuber disease that each year causes substantial losses to the food industry. Here, we explore the possibility of early detection of the disease via gas/vapor analysis, in a laboratory environment, using a recent technology known as FAIMS (Field Asymmetric Ion Mobility Spectrometry). In this work, tubers were inoculated with a bacterium causing the infection, Pectobacterium carotovorum, and stored within set environmental conditions in order to manage disease progression. They were compared with controls stored in the same conditions. Three different inoculation time courses were employed in order to obtain diseased potatoes showing clear signs of advanced infection (for standard detection) and diseased potatoes with no apparent evidence of infection (for early detection). A total of 156 samples were processed by PCA (Principal Component Analysis) and k-means clustering. Results show a clear discrimination between controls and diseased potatoes for all experiments with no difference among observations from standard and early detection. Further analysis was carried out by means of a statistical model based on LDA (Linear Discriminant Analysis) that showed a high classification accuracy of 92.1% on the test set, obtained via a LOOCV (leave-one out cross-validation). PMID:25171118

Rutolo, Massimo; Covington, James A.; Clarkson, John; Iliescu, Daciana



Detection of gaseous compounds by needle trap sampling and direct thermal-desorption photoionization mass spectrometry: concept and demonstrative application to breath gas analysis.  


A fast detection method to analyze gaseous organic compounds in complex gas mixtures was developed, using a needle trap device (NTD) in conjunction with thermal-desorption photoionization time-of-flight mass spectrometry (TD-PI-TOFMS). The mass spectrometer was coupled via a deactivated fused silica capillary to an injector of a gas chromatograph. In the hot injector, the analytes collected on the NTD were thermally desorbed and directly transferred to the PI-TOFMS ion source. The molecules are softly ionized either by single photon ionization (SPI, 118 nm) or by resonance enhanced multiphoton ionization (REMPI, 266 nm), and the molecular ion signals are detected in the TOF mass analyzer. Analyte desorption and the subsequent PI-TOFMS detection step only lasts ten seconds. The specific selectivity of REMPI (i.e., aromatic compounds) and universal ionization characteristics render PI-MS as a promising detection system. As a first demonstrative application, the alveolar phase breath gas of healthy, nonsmoking subjects was sampled on NTDs. While smaller organic compounds such as acetone, acetaldehyde, isoprene, or cysteamine can be detected in the breath gas with SPI, REMPI depicts the aromatic substances phenol and indole at 266 nm. In the breath gas of a healthy, smoking male subject, several xenobiotic substances such as benzene, toluene, styrene, and ethylbenzene can be found as well. Furthermore, the NTD-REMPI-TOFMS setup was tested for breath gas taken from a mechanically ventilated pig under continuous intravenous propofol (2,6-diisopropylphenol, narcotic drug) infusion. PMID:25517186

Kleeblatt, Juliane; Schubert, Jochen K; Zimmermann, Ralf



Detection system for a gas chromatograph. [. cap alpha. -methylnaphthalene,. beta. -methylnapthalene  


A method and apparatus are described for the quantitative analysis of vaporizable compounds, and in particular of polycyclic aromatic hydrocarbons which may be induced to fluoresce. The sample to be analyzed is injected into a gas chromatography column and is eluted through a narrow orifice into a vacuum chamber. The free expansion of the eluted sample into the vacuum chamber creates a supersonic molecular beam in which the sample molecules are cooled to the extent that the excited vibrational and rotational levels are substantially depopulated. The cooled molecules, when induced to fluoresce by laser excitation, give greatly simplified spectra suitable for analytical purposes. The laser induced fluorimetry provides great selectivity, and the gas chromatograph provides quantitative transfer of the sample to the molecular beam. 3 figures, 2 tables.

Hayes, J.M.; Small, G.J.



Detection of greenhouse-gas-induced climatic change. Progress report, 1 December 1991--30 June 1994  

SciTech Connect

In addition to changes due to variations in greenhouse gas concentrations, the global climate system exhibits a high degree of internally-generated and externally-forced natural variability. To detect the enhanced greenhouse effect, its signal must be isolated from the ``noise`` of this natural climatic variability. A high quality, spatially extensive data base is required to define the noise and its spatial characteristics. To facilitate this, available land and marine data bases will be updated and expanded. The data will be analyzed to determine the potential effects on climate of greenhouse gas concentration changes and other factors. Analyses will be guided by a variety of models, from simple energy balance climate models to ocean General Circulation Models. Appendices A--G contain the following seven papers: (A) Recent global warmth moderated by the effects of the Mount Pinatubo eruption; (B) Recent warming in global temperature series; (C) Correlation methods in fingerprint detection studies; (D) Balancing the carbon budget. Implications for projections of future carbon dioxide concentration changes; (E) A simple model for estimating methane concentration and lifetime variations; (F) Implications for climate and sea level of revised IPCC emissions scenarios; and (G) Sulfate aerosol and climatic change.

Wigley, T.M.L.; Jones, P.D.



A method for detecting breakthrough of organic solvent vapors in a charcoal tube using semiconductor gas sensors  

SciTech Connect

This study developed a method for detecting organic vapors that break through charcoal tubes, using semiconductor gas sensors as a breakthrough detector of vapors. A glass column equipped with two sensors was inserted in Teflon tubing, and air containing organic vapor was introduced at a constant flow rate. After the output signal of the sensors became stable, a charcoal tube was inserted into the tubing at the upstream of the sensors. The resistance of the sensors was collected temporally in an integrated circuit (IC) card. The vapor concentration of the air near the sensors was measured with a gas chromatograph (GC) equipped with a flame ionization detector (FID) at intervals of 5 minutes to obtain the breakthrough curve. When the relative humidity was zero, the output signals of the sensors began to change before the breakthrough point (1% breakthrough time). This tendency was almost the same for methyl acetate, ethyl acetate, isopropyl alcohol (IPA), toluene, and chloroform. For dichloromethane and 1,1,1-trichloroethane, the time when the sensor output signals began to rise was almost the same as the breakthrough point. When the relative humidity was 80 percent, the sensors could also detect many vapors before the breakthrough point, but they could not perceive dichloromethane and chloroform vapors. A personal sampling system with a breakthrough detector was developed and its availability is discussed.

Hori, Hajime; Noritake, Yuji; Murobushi, Hisako; Higashi, Toshiaki; Tanaka, Isamu



[Analysis of C4 fluoride compounds in alkylation materials by gas chromatography/flame ionization detection (GC/FID)].  


A method for the analysis of C4 fluoride compounds in alkylation materials was developed by GC/FID. In order to confirm the presence of C4 fluoride compounds in alkylation materials, 1-fluorobutane, 2-fluorobutane and 2-fluoro-2-methylpropane were synthesized and analysed by GC/FID, gas chromatography/atomic emission detection (GC/AED) and gas chromatography/mass spectrometry (GC/MS). The results showed that only 2-fluoro-2-methylpropane existed in the alkylation materials. Based on the properties of element response on GC/AED, the calibration factors of C4 fluoride compounds on GC/FID were calculated. The analysis was performed on OV-225 (50 m x 0.25 mm i. d. x 0.25 microm) and SE-54 (44 m x 0.22 mm i. d. x 0.25 microm) columns, which were connected in series. FID was used as the detector. In quantitative analysis of the alkylation materials the methods of calibration normalization and indirect external standard were suggested. The calibration curves were linear (r = 0.992) in the concentration range of 156 - 700 microL/L. The minimum detection limit of 2-fluoro-2-methylpropane in real samples was 150 microL/L (S/N = 3). The method is simple, reproducible and easy to be applied. The other components in the alkylation materials can also be analyzed if the calibration normalization method is used. PMID:15706940

Han, Jianghua; Yang, Haiying



Detection of soot particles in gas turbine engine combustion gases using nonintrusive FTIR spectroscopy  

NASA Astrophysics Data System (ADS)

Fourier transform IR (FTIR) spectroscopy for making non- intrusive measurements of gas turbine exhaust gases and laser induced incandescence for measuring soot content are being evaluated in EU Brite EuRam project AEROJET. Soot concentrations in modern aero-engine exhausts are very low with mean particle sizes < 100 nm. The standard extractive filter paper soot measurement gives results expressed in terms of SAE smoke number, typically < 10 SAE for modern engines.

Hilton, Moira; Black, John D.



Gas detection with SnO 2 sensors modified by zeolite films  

Microsoft Academic Search

Zeolite films have been grown on top of SnO2 sensors to modify their response to gas phase molecules with the aim of improving their selectivity. To this end SnO2 sensors were first prepared using conventional procedures, and then zeolite layers (silicalite and zeolite A) were grown on the outer SnO2 surface, using different synthesis procedures. The zeolite-modified sensors were tested

Montserrat Vilaseca; Joaquin Coronas; Albert Cirera; Albert Cornet; Joan Ramon Morante; Jesus Santamaria



Pulsed Quantum-Cascade Laser-Based Sensor for Trace-Gas Detection of Carbonyl Sulfide  

Microsoft Academic Search

Simultaneous exhaled carbonyl sulfide (OCS) and carbon dioxide concentration measurements in human breath are demonstrated with a compact pulsed quantum-cascade laser-based gas sensor. We achieved a noise-equivalent sensitivity (1sigma) of 1.2 parts per billion by measuring a well-isolated OCS P(11) absorption line in the nu3 band at 2057.6 cm^-1 using an astigmatic Herriott cell of 36-m optical path length and

Gerard Wysocki; Matt McCurdy; Stephen So; Damien Weidmann; Chad Roller; Robert F. Curl; Frank K. Tittel



GasBench/isotope ratio mass spectrometry: a carbon isotope approach to detect exogenous CO(2) in sparkling drinks.  


A new procedure for the determination of carbon dioxide (CO(2)) (13)C/(12)C isotope ratios, using direct injection into a GasBench/isotope ratio mass spectrometry (GasBench/IRMS) system, has been developed to improve isotopic methods devoted to the study of the authenticity of sparkling drinks. Thirty-nine commercial sparkling drink samples from various origins were analyzed. Values of delta(13)C(cava) ranged from -20.30 per thousand to -23.63 per thousand, when C3 sugar addition was performed for a second alcoholic fermentation. Values of delta(13)C(water) ranged from -5.59 per thousand to -6.87 per thousand in the case of naturally carbonated water or water fortified with gas from the spring, and delta(13)C(water) ranged from -29.36 per thousand to -42.09 per thousand when industrial CO(2) was added. It has been demonstrated that the addition of C4 sugar to semi-sparkling wine (aguja) and industrial CO(2) addition to sparkling wine (cava) or water can be detected. The new procedure has advantages over existing methods in terms of analysis time and sample treatment. In addition, it is the first isotopic method developed that allows (13)C/(12)C determination directly from a liquid sample without previous CO(2) extraction. No significant isotopic fractionation was observed nor any influence by secondary compounds present in the liquid phase. PMID:17879391

Cabañero, Ana I; San-Hipólito, Tamar; Rupérez, Mercedes



Detection of interstellar NH3 in the far-infrared - Warm and dense gas in Orion-KL  

NASA Technical Reports Server (NTRS)

Results of an investigation are presented which show the detection of the (J,K) = a(4,3)-s(3,3) rotation-inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region. The line is found to be in emission and has a FWHM greater than or equal to 30 km/s, while the far-IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3)-s(3,3) line is very optically thick and it is determined that radiative excitation of the (4,3) NH3 level by far-IR emission from dust within the source can be ruled out. It is concluded that the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Densities of approximately 10 to the 7th/cu cm are high enough to explain the observations, while shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

Townes, C. H.; Genzel, R.; Watson, D. M.; Storey, J. W. V.



Detection of low concentration formaldehyde gas by photonic crystal sensor fabricated by nanoimprint process in polymer material  

NASA Astrophysics Data System (ADS)

This paper describes experimental measurement results for photonic crystal sensor devices which have been functionalized for gas sensing applications. The sensor consists of a two dimensional photonic crystal etched into a slab waveguide having a refractive index of 1.7-1.9. Test devices were fabricated from SiON material on silicon / silicon dioxide platform, and also in polymer materials on silicon platform. The inorganic photonic crystals were made using direct write electron-beam lithography and reactive ion etching. The polymeric devices were made by nano-imprint lithography using the SiON structure as the imprint master. The high refractive index polymer was composed of a TiO2 - UV resin nanocomposite having a nanoparticle fraction between 50 and 60 wt%. This resulted in a tunable refractive index between 1.7 and 1.85. Devices were functionalized for gas sensing applications by coating the surface with a chemical receptor. This responsive layer reacts with the target gas and changes its refractive index. This change causes the angle of out-coupling to change slightly. In this paper we report successful detection of formaldehyde in air at sub ppm levels, and discuss details of chemical functionalization of the PC sensor.

Boersma, A.; van Ee, Renz J.; Stevens, Ralph S. A.; Saalmink, Milan; Charlton, Martin D. B.; Pollard, Michael E.; Chen, Ruiqi; Kontturi, Ville; Karioja, Pentti; Alajoki, Teemu



Multi-scale Detection of Organic and Inorganic Signatures Provides Insights into Gas Shale Properties and Evolution  

SciTech Connect

Organic geochemical analyses, including solvent extraction or pyrolysis, followed by gas chromatography and mass spectrometry, are generally conducted on bulk gas shale samples to evaluate their source and reservoir properties. While organic petrology has been directed at unravelling the matrix composition and textures of these economically important unconventional resources, their spatial variability in chemistry and structure is still poorly documented at the sub-micrometre scale. Here, a combination of techniques including transmission electron microscopy and a synchrotron-based microscopy tool, scanning transmission X-ray microscopy, have been used to characterize at a multiple length scale an overmature organic-rich calcareous mudstone from northern Germany. We document multi-scale chemical and mineralogical heterogeneities within the sample, from the millimetre down to the nanometre-scale. From the detection of different types of bitumen and authigenic minerals associated with the organic matter, we show that the multi-scale approach used in this study may provide new insights into gaseous hydrocarbon generation/retention processes occurring within gas shales and may shed new light on their thermal history.

Bernard, S.; Horsfield, B; Schultz, H; Schreiber, A; Wirth, R; Thi AnhVu, T; Perssen, F; Konitzer, S; Volk, H; et. al.



Determination of the volatiles from tobacco by capillary gas chromatography with atomic emission detection and mass spectrometry.  


A new gas chromatograph-atomic emission detector (GC-AED) coupled with Deans switching technique for analyzing volatiles from tobaccos were developed. The detector operating parameters (reagent gas pressure and make-up gas flow rate) were optimized. The detection limits for the elements carbon (193?nm), hydrogen (486?nm) and oxygen (171?nm) ranged 0.05-0.2, 0.05-0.3 and 1-11?ng, respectively, depending on the compound. The sensitivity and linearity for the elements carbon (193?nm), hydrogen (486?nm) and oxygen (171?nm) decreased in the order O>H>C. Calibration curves were obtained by plotting peak area versus concentration, and the correlation coefficients relating to linearity were at least 0.9359. Elemental response factors measured on these channels, relative to the carbon 193-nm channel, were hydrogen, 0.38-0.48 (mean %RSD=5.64), and oxygen, 0.085-0.128 (mean %RSD=14.9). The evaluation was also done for the new technique and for an established GC-MS technique for the same real samples. The results of GC-AED and GC-MS showed that there was a relatively good agreement between the two sets of data. PMID:22180172

Li, Gang; Wu, Da; Wang, Ye; Xie, Wenyan; Zhang, Xiangmin; Liu, Baizhan



Comparison of Cavity Ringdown and Laser-Induced Fluorescence Spectroscopy for Trace Gas Detection: NO2  

NASA Astrophysics Data System (ADS)

In the last decade, Cavity Ringdown Spectroscopy (CRDS) has established itself as a new highly sensitive direct absorption spectroscopic technique. Present applications of CRDS in atmospheric sciences are mainly in the detection of tracer species. However, new technological advances should expand the applicability of CRDS to include other species, such as reactive intermediates and free radicals. For example, Laser-Induced Fluorescence is one of the prevalent methods for detection of NO2 in the atmosphere and has achieved detection limits as low as 1 ppt. Comparison of CRDS with LIF detection of NO2 demonstrates that, even though the sensitivity of the LIF method is superior by approximately one order of magnitude, the CRDS approach is significantly less complex. In many cases, the superior LIF detection limit is not necessary, and CRDS has the advantage of a direct absorption technique with no spectroscopic interferences and a greatly simplified calibration methodology. Furthermore, CRDS should be applicable to various other atmospheric trace species, most significantly those that do not fluoresce. Results and implications of the comparison of the two methods will be discussed.

Keutsch, F. N.; Engel, G. S.; Paul, J. B.; Perkins, K. K.; St. Clair, J. M.; Anderson, J. G.



Molecularly imprinted polymer sensors for detection in the gas, liquid, and vapor phase.  


Fast, reliable, and inexpensive analytical techniques for detection of airborne chemical warfare agents are desperately needed. Recent advances in the field of molecularly imprinted polymers have created synthetic nanomaterials that can sensitively and selectively detect these materials in aqueous environments, but thus far, they have not been demonstrated to work for detection of vapors. The imprinted polymers function by mimicking the function of biological receptors. They can provide high sensitivity and selectivity but, unlike their biological counterparts, maintain excellent thermal and mechanical stability. The traditional imprinted polymer approach is further enhanced in this work by the addition of a luminescent europium that has been introduced into the polymers to provide enhanced chemical affinity as well as a method for signal transduction to indicate the binding event. The europium in these polymers is so sensitive to the bound target; it can distinguish between species differing by a single methyl group. The imprinted polymer technology is fiber optic-based making it inexpensive and easily integratable with commercially available miniature fiber optic spectrometer technologies to provide a shoebox size device. In this work, we will describe efforts to apply these sensors for detection of airborne materials and vapors. Successful application of this technology will provide accurate low level vapor detection of chemical agents or pesticides with little to no false positives. PMID:22641530

Jenkins, Amanda L; Ellzy, Michael W; Buettner, Leonard C



Detection of accreting circumstellar gas around weak emission-line Herbig Ae/Be stars  

NASA Technical Reports Server (NTRS)

Archival and recent International Ultraviolet Explorer (IUE) high dispersion spectra of late B stars which reveal the presence of accreting gas with velocities as high as 350 km/s, collisional ionization of the accreting gas to temperatures above the stellar T(sub eff), and column densities intermediate between those observed toward classical Herbig Ae/Be stars and the nearby proto-planetary system beta Pictoris are presented. One of the stars HD 176386, while lacking obvious optical signatures of youth, is a member of the R CrA star formation region, and with an inferred age of 2.8 Myr has not yet arrived on the zero-age main sequence (ZAMS). The other object, an isolated, field B star with pronounced IR excess due to warm, circumstellar dust, 51 Oph, exhibits only modest H(alpha) emission. The combination of high velocity, accreting gas in systems with IR excesses due to circumstellar dust suggests that not only are these objects candidate proto-planetary systems, but that they may represent an extension to higher stellar masses of the weak-emission pre-main sequence (PMS) stars.

Grady, C. A.; Perez, M. R.; The, P. S.



Laboratory Gas-phase Detection of the Cyclopropenyl Cation (C-C3H3 +)  

NASA Astrophysics Data System (ADS)

The cyclopropenyl cation (c-C3H3 +) is the smallest aromatic hydrocarbon molecule and considered to be a pivotal intermediate in ion-molecule reactions in space. An astronomical identification has been prohibited so far, because of a lack of gas-phase data. Here we report the first high resolution infrared laboratory gas-phase spectrum of the ? 4 (C-H asymmetric stretching) fundamental band of c-C3H3 +. The c-C3H3 + cations are generated in supersonically expanding planar plasma by discharging a propyne/helium gas pulse, yielding a rotational temperature of ~35 K. The absorption spectrum is recorded in the 3.19 ?m region using sensitive continuous-wave cavity ring-down spectroscopy. The analysis of about 130 ro-vibrational transitions results in precise spectroscopic parameters. These constants allow for an accurate comparison with high-level theoretical predictions, and provide the relevant information needed to search for this astrochemically relevant carbo-cation in space.

Zhao, Dongfeng; Doney, Kirstin D.; Linnartz, Harold



Fiber Optic Sensing Technology for Detecting Gas Hydrate Formation and Decomposition  

SciTech Connect

A fiber optic-based distributed sensing system (DSS) has been integrated with a large volume (72 L) pressure vessel providing high spatial resolution, time resolved, 3-D measurement of hybrid temperature-strain (TS) values within experimental sediment gas hydrate systems. Areas of gas hydrate formation (exothermic) and decomposition (endothermic) can be characterized through this proxy by time series analysis of discrete data points collected along the length of optical fibers placed within a sediment system. Data is visualized as a 'movie' of TS values along the length of each fiber over time. Experiments conducted in the Seafloor Processing Simulator (SPS) at Oak Ridge National Laboratory show clear indications of hydrate formation and dissociation events at expected P-T conditions given the thermodynamics of the CH4-H2O system. The high spatial resolution achieved with fiber optic technology makes the DSS a useful tool for visualizing time resolved formation and dissociation of gas hydrates in large-scale sediment experiments.

Rawn, Claudia J [ORNL; Leeman, John R [University of Oklahoma, Norman; Ulrich, Shannon M [ORNL; Alford, Jonathan E [ORNL; Phelps, Tommy Joe [ORNL; Madden, Megan Elwood [University of Oklahoma, Norman



Gold nanoparticles-peptide based gas sensor arrays for the detection of food aromas.  


A gas sensor array based on peptide modified gold nanoparticles deposited onto 20MHz quartz crystal microbalances has been realized. Glutathione and its constituting aminoacids and dipeptides have been used as ligands. A great increase in sensitivity (2 orders of magnitude) was achieved using gold nanoparticles versus monolayer modified QCMs. The sensors have been characterised in terms of sensitivity for hexane, water, trimethylammine and ethanol. Highest sensitivity was found for water. The ability to discriminate typical food aromas as cis-3-hexenol, isopentylacetate, ethylacetate, and terpinen-4-ol dissolved in different solvents was studied using a gas sensor array constituted by gold nanoparticles modified with the glutathione peptides, thioglycolic acid and an heptapeptide. The array was found able to discriminate the food aromas, the response being dependent on the polarity of the solvent used. Tests on real olive oil samples gave a satisfactory separation among samples having defects versus non defected samples demonstrating that this approach has high potential for the development of gas sensor arrays to be used in real samples. PMID:23261699

Compagnone, D; Fusella, G C; Del Carlo, M; Pittia, P; Martinelli, E; Tortora, L; Paolesse, R; Di Natale, C



Selectivity enhancement in photoacoustic gas analysis via phase-sensitive detection at high modulation frequency  

NASA Technical Reports Server (NTRS)

A method for detecting a target fluid in a fluid sample comprising a first fluid and the target fluid using photoacoustic spectroscopy (PAS), comprises a) providing a light source configured to introduce an optical signal having at least one wavelength into the fluid sample; b) modulating the optical signal at a desired modulation frequency such that the optical signal generates an acoustic signal in the fluid sample; c) measuring the acoustic signal in a resonant acoustic detector; and d) using the phase of the acoustic signal to detect the presence of the target fluid.

Kosterev, Anatoliy (Inventor)



Detection of soil microorganism in situ by combined gas chromatography mass spectrometry  

NASA Technical Reports Server (NTRS)

Experimental tests were made to determine whether analysis of volatile metabolic products, formed in situ, is a viable procedure for an extraterrestrial life detection system. Laboratory experiments, carried out under anaerobic conditions with addition of carbon source, extended to include a variety of soils and additional substrates. In situ experiments were conducted without amendment using a vacuum sampling system.

Alexander, M.; Duxbury, J. M.; Francis, A. J.; Adamson, J.



A Method for the Automated Detection of Venous Gas Bubbles in Humans Using Empirical Mode Decomposition  

Microsoft Academic Search

Doppler ultrasound signals are widely used to grade the quantity of circulating venous bubbles in divers. Current techniques rely on trained observers, making the grading process both time-consuming and subjective. The automated detection of bubbles, however, is confounded by the presence of other signals, primarily those arising from blood motion. Empirical Mode Decomposition was used here to calculate the intrinsic

M. A. Chappell; S. J. Payne



Gas chromatography for detection of citrus infestation by tephritid fruit flies  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tephritid fruit flies are serious economic pests worldwide. As larvae, they feed and develop within the pulp of host fruits, making infestation difficult to detect by visual inspection. At U.S. ports of entry, incoming produce shipments are checked for infestation by manually cutting open a small ...


Systems and methods of monitoring acoustic pressure to detect a flame condition in a gas turbine  


A method may detect a flashback condition in a fuel nozzle of a combustor. The method may include obtaining a current acoustic pressure signal from the combustor, analyzing the current acoustic pressure signal to determine current operating frequency information for the combustor, and indicating that the flashback condition exists based at least in part on the current operating frequency information.

Ziminsky, Willy Steve (Simpsonville, SC); Krull, Anthony Wayne (Anderson, SC); Healy, Timothy Andrew (Simpsonville, SC), Yilmaz, Ertan (Glenville, NY)



Gas chromatography for detection of citrus infestation by fruit fly larvae (Diptera: Tephritidae)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tephritid fruit flies are serious economic pests worldwide. As larvae, they feed and develop within the pulp of host fruits, making infestation difficult to detect by visual inspection. At U.S. ports of entry, incoming produce shipments are checked for infestation by manually cutting open a small ...


Creation and Detection of a Mesoscopic Gas in a Nonlocal Quantum Superposition  

SciTech Connect

We investigate the scattering of a quantum matter wave soliton on a barrier in a one-dimensional geometry, and we show that it can lead to mesoscopic quantum superposition states, where the atomic gas is in a coherent superposition of being in the half-space to the left of the barrier and being in the half-space to the right of the barrier. We propose an interferometric method to reveal the coherent nature of this superposition, and we discuss in detail the experimental feasibility.

Weiss, Christoph; Castin, Yvan [Laboratoire Kastler Brossel, Ecole Normale Superieure, UPMC and CNRS, 24 rue Lhomond, 75231 Paris Cedex 05 (France)



Tunable fiber laser based photoacoustic gas sensor for early fire detection  

NASA Astrophysics Data System (ADS)

A photoacoustic gas sensor using a near-infrared tunable fiber laser and based on wavelength modulation spectroscopy technique is developed. This sensor is capable of quasi-simultaneous quantification of water vapour, acetylene, carbon dioxide, and carbon monoxide (H2O, C2H2, CO and CO2) concentrations in the fire emulator. The feasibility of using this sensor as an early fire detector was demonstrated. The fire warning gases from smoldering paper were measured. The peak concentrations of gases from smoldering paper were 20,300 ppm H2O, 2.1 ppm C2H2, 756 ppm CO, and 1612 ppm CO2 after 400 s.

Wang, Jianwei; Wang, Huili



Low-Dimensional Palladium Nanostructures for Fast and Reliable Hydrogen Gas Detection  

PubMed Central

Palladium (Pd) has received attention as an ideal hydrogen sensor material due to its properties such as high sensitivity and selectivity to hydrogen gas, fast response, and operability at room temperature. Interestingly, various Pd nanostructures that have been realized by recent developments in nanotechnologies are known to show better performance than bulk Pd. This review highlights the characteristic properties, issues, and their possible solutions of hydrogen sensors based on the low-dimensional Pd nanostructures with more emphasis on Pd thin films and Pd nanowires. The finite size effects, relative strengths and weaknesses of the respective Pd nanostructures are discussed in terms of performance, manufacturability, and practical applicability. PMID:22346605

Noh, Jin-Seo; Lee, Jun Min; Lee, Wooyoung



CO-laser-based photoacoustic trace-gas detection: applications in postharvest physiology  

NASA Astrophysics Data System (ADS)

A sensitive CO-laser-based photoacoustic trace-gas detector has been applied to study physiological processes in biological samples. A continuous flow-through system at atmospheric pressure leads the released trace gases from the sample to the photoacoustic resonator cells at flow rates where these processes can be studied with high time resolution. We focus here on transient effects that were found during fermentation of red bell peppers and apples, yielding in particular ethanol and acetaldehyde. Results are discussed also in the light of simultaneous O2 measurements using polarographic oxygen sensors.

Oomens, J.; Zuckermann, H.; Persijn, S.; Parker, D. H.; Harren, F. J. M.



Determination of ten pyrethroids in various fruit juices: comparison of dispersive liquid-liquid microextraction sample preparation and QuEChERS method combined with dispersive liquid-liquid microextraction.  


Dispersive liquid-liquid microextraction (DLLME) sample preparation and the quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with DLLME were developed and compared for the analysis of ten pyrethroids in various fruit juices using gas chromatography-electron capture detection (GC-ECD). QuEChERS-DLLME method has found its widespread applications to all the fruit juices including those samples with more complex matrices (orange, lemon, kiwi and mango) while DLLME was confined to the fruit juices with simpler matrices (apple, pear, grape and peach). The two methods provided acceptable recoveries and repeatability. In addition, the applicabilities of two methods were demonstrated with the real samples and further confirmed by gas chromatography-mass spectrometry (GC-MS). PMID:24767068

Zhang, Yaohai; Zhang, Xuelian; Jiao, Bining



Persistence behaviour of deltamethrin on tea and its transfer from processed tea to infusion.  


The dynamics and residues of deltamethrin in a tea grown in an open field ecosystem were investigated. The quantification was performed using gas chromatography-electron capture detection (GC-ECD) and confirmed by gas chromatograph-mass spectrometry (GC-MS) in selective ion monitoring (SIM) mode. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 87% to 101% with relative standard deviations (RSD) ranging of 0.7-7.1%. The residues of deltamethrin were found to dissipate following first order kinetics with half-life ranging between 3.04 and 3.54d for two different rates of foliar application. The deltamethrin residues are present in the processed tea are not transferred into the tea infusion during the infusion process, since their water solubility is extremely low. These results can be utilized in formulating the spray schedule and safety evaluation on deltamethrin tea crop. PMID:24997931

Paramasivam, M; Chandrasekaran, S



Derivatization of organophosphorus nerve agent degradation products for gas chromatography with ICPMS and TOF-MS detection.  


Separation and detection of seven V-type (venomous) and G-type (German) organophosphorus nerve agent degradation products by gas chromatography with inductively coupled plasma mass spectrometry (GC-ICPMS) is described. The nonvolatile alkyl phosphonic acid degradation products of interest included ethyl methylphosphonic acid (EMPA, VX acid), isopropyl methylphosphonic acid (IMPA, GB acid), ethyl hydrogen dimethylamidophosphate sodium salt (EDPA, GA acid), isobutyl hydrogen methylphosphonate (IBMPA, RVX acid), as well as pinacolyl methylphosphonic acid (PMPA), methylphosphonic acid (MPA), and cyclohexyl methylphosphonic acid (CMPA, GF acid). N-(tert-Butyldimethylsilyl)-N-methyltrifluroacetamide with 1% TBDMSCl was utilized to form the volatile TBDMS derivatives of the nerve agent degradation products for separation by GC. Exact mass confirmation of the formation of six of the TBDMS derivatives was obtained by GC-time of flight mass spectrometry (TOF-MS). The method developed here allowed for the separation and detection of all seven TBDMS derivatives as well as phosphate in less than ten minutes. Detection limits for the developed method were less than 5 pg with retention times and peak area precisions of less than 0.01 and 6%, respectively. This method was successfully applied to river water and soil matrices. To date this is the first work describing the analysis of chemical warfare agent (CWA) degradation products by GC-ICPMS. PMID:17356819

Richardson, Douglas D; Caruso, Joseph A




SciTech Connect

Recent high-redshift surveys for 21 cm absorption in damped Ly{alpha} absorption systems (DLAs) take the number of published searches at z{sub abs} > 2 to 25, the same number as at z{sub abs} < 2, although the detection rate at high redshift remains significantly lower (20% compared to 60%). Using the known properties of the DLAs to estimate the unknown profile widths of the 21 cm non-detections and including the limits via a survival analysis, we show that the mean spin temperature/covering factor degeneracy at high redshift is, on average, double that of the low-redshift sample. This value is significantly lower than the previous factor of eight for the spin temperatures and is about the same factor as in the angular diameter distance ratios between the low- and high-redshift samples. That is, without the need for the several pivotal assumptions, which lead to an evolution in the spin temperature, we show that the observed distribution of 21 cm detections in DLAs can be accounted for by the geometry effects of an expanding universe. That is, as yet there is no evidence of the spin temperature of gas-rich galaxies evolving with redshift.

Curran, S. J., E-mail: [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)



Mesenchymal stem cells detect and defend against gammaherpesvirus infection via the cGAS-STING pathway  

PubMed Central

Mesenchymal stem cells (MSCs) are widely used in clinical settings to treat tissue injuries and autoimmune disorders due to their multipotentiality and immunomodulation. Long-term observations reveal several complications after MSCs infusion, especially herpesviral infection. However, the mechanism of host defense against herpesviruses in MSCs remains largely unknown. Here we showed that murine gammaherpesvirus-68 (MHV-68), which is genetically and biologically related to human gammaherpesviruses, efficiently infected MSCs both in vitro and in vivo. Cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) was identified as the sensor of MHV-68 in MSCs for the first time. Moreover, the cytosolic DNA sensing pathway mediated a potent anti-herpesviral effect through the adaptor STING and downstream kinase TBK1. Furthermore, blockade of IFN signaling suggested that cytosolic DNA sensing triggered both IFN-dependent and -independent anti-herpesviral responses. Our findings demonstrate that cGAS-STING mediates innate immunity to gammaherpesvirus infection in MSCs, which may provide a clue to develop therapeutic strategy. PMID:25592282

Yang, Kun; Wang, Jinli; Wu, Minhao; Li, Meiyu; Wang, Yi; Huang, Xi



Continuous-wave terahertz by photomixing: applications to gas phase pollutant detection and quantification  

NASA Astrophysics Data System (ADS)

Recent advances in the development of monochromatic continuous-wave terahertz sources suitable for high resolution gas phase spectroscopy and pollution monitoring are reviewed. Details of a source using an ultra fast opto-electronic photomixing element are presented. The construction of a terahertz spectrometer using this source has allowed spectroscopic characterisation and application studies to be completed. Analysis of H 2S and OCS under laboratory conditions are used to demonstrate the spectrometer performance, and the determination of the transition line strengths and pressure self broadening coefficients for pure rotational transitions of OCS. The spectral purity 5 MHz, tunability 0.3 to 3 THz, and long wavelength ?200 ?m of this source have been exploited to identify and quantify numerous chemical species in cigarette smoke. The key advantages of this frequency domain are its high species selectivity and the possibility to make reliable measurements of gas phase samples heavily contaminated by aerosols and particles. To cite this article: F. Hindle et al., C. R. Physique 9 (2008).

Hindle, Francis; Cuisset, Arnaud; Bocquet, Robin; Mouret, Gaël



Mesenchymal stem cells detect and defend against gammaherpesvirus infection via the cGAS-STING pathway.  


Mesenchymal stem cells (MSCs) are widely used in clinical settings to treat tissue injuries and autoimmune disorders due to their multipotentiality and immunomodulation. Long-term observations reveal several complications after MSCs infusion, especially herpesviral infection. However, the mechanism of host defense against herpesviruses in MSCs remains largely unknown. Here we showed that murine gammaherpesvirus-68 (MHV-68), which is genetically and biologically related to human gammaherpesviruses, efficiently infected MSCs both in vitro and in vivo. Cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) was identified as the sensor of MHV-68 in MSCs for the first time. Moreover, the cytosolic DNA sensing pathway mediated a potent anti-herpesviral effect through the adaptor STING and downstream kinase TBK1. Furthermore, blockade of IFN signaling suggested that cytosolic DNA sensing triggered both IFN-dependent and -independent anti-herpesviral responses. Our findings demonstrate that cGAS-STING mediates innate immunity to gammaherpesvirus infection in MSCs, which may provide a clue to develop therapeutic strategy. PMID:25592282

Yang, Kun; Wang, Jinli; Wu, Minhao; Li, Meiyu; Wang, Yi; Huang, Xi



Detection of ethene and other hydrocarbons in gas turbine engine exhaust using non-intrusive FTIR spectroscopy  

NASA Astrophysics Data System (ADS)

As part of the EU funded project AEROJET2, a number of gas turbine engine tests were performed in different facilities around Europe. At Farnborough, UK a Spey engine was used to test a suite of prototype optically based instrumentation designed to measure exhaust gas emissions without using extractive probe systems. In addition to the AEROJET 2 prototype instrumentation, a Bruker Equinox 55 Fourier transform infrared (FTIR) spectrometer was used to obtain infrared spectra of the exhaust plume both in emission and absorption mode. The Bruker FTIR spectrometer was fitted with a periscope system so that different lines of sight could be monitored in the plume in a vertical plane 25 cm downstream from the nozzle exit and 20 cm upstream of the center line of sight of the AEROJET 2 prototype instrumentation. DERA (now QinetiQ) provided exhaust gas analysis data for different engine running conditions using samples extracted from the plume with an intrusive probe. The probe sampled along a horizontal plane across the centerline of the engine 45 cm downstream of the nozzle exit. The Bruker spectrometer used both InSb (indium antimonide) and MCT (mercury-cadmium-telluride) detectors to maximize the sensitivity across the IR range 600-4000 cm-1. Typically, CO2 and H2O IR signatures dominate the observed spectra of the plume. However, the engine tests showed that at low power engine conditions spectral features associated with CO around 2147 cm-1 and with hydrocarbons could be observed at around 3000 cm-1. In particular the presence of ethene (C2H2) was detected from observation of its characteristic in and out of plane vibration mode at 949 cm-1. At high engine powers the presence of NO was detected at 1900.3 cm-1. Species concentrations were calculated using a slab model for each line of sight compared against reference spectra. The engine plume was assumed to be symmetric about the centerline. On this basis, data from the extractive sampling gas analysis that had been obtained by traversing the probe across a horizontal plane through the centerline could be compared with non-intrusive measurements made by scanning vertically. Adjustments have been made to account for the 20 cm downstream offset in measurement planes of the probe and the spectrometer behind the nozzle exit.

Arrigone, Giovanni M.; Welch, Michael A.; Hilton, Moira; Miller, Michael N.; Wilson, Christopher W.



Near infrared frequency comb vernier spectrometer for broadband trace gas detection.  


We present a femtosecond frequency comb vernier spectrometer in the near infrared with a femtosecond Er doped fiber laser, a scanning high-finesse cavity and an InGaAs camera. By utilizing the properties of a frequency comb and a scanning high-finesse cavity such a spectrometer provides broad spectral bandwidth, high spectral resolution, and high detection sensitivity on a short time scale. We achieved an absorption sensitivity of ~8 × 10(-8) cm(-1)Hz(-1/2), corresponding to a detection limit of ~70 ppbv for acetylene, with a resolution of ~1.1 GHz in single images taken in 0.5 seconds and covering a frequency range of ~5 THz. Such measurements have broad applications for sensing greenhouse gases in this fingerprint near infrared region with a simple apparatus. PMID:25321773

Zhu, Feng; Bounds, James; Bicer, Aysenur; Strohaber, James; Kolomenskii, Alexandre A; Gohle, Christoph; Amani, Mahmood; Schuessler, Hans A



Gas chromatographic method using photoionization detection for the determination of breath pentane.  


Lipid peroxidation is thought to be an important event in the pathogenesis of atherosclerosis. It has been suggested that pentane, which can be formed during the oxidation of omega-6 fatty acids, is a marker of lipid peroxidation. Previous studies have reported elevated breath pentane and serum markers of lipid peroxidation in smokers. However, chromatographic separation of pentane from isoprene in virtually all of these studies was incomplete and the methods used did not resolve pentane into its isomers, n-pentane and isopentane. Additionally, most current methods are complicated, requiring trapping and concentrating steps to obtain adequate sensitivity prior to hydrocarbon analysis. The purpose of the current study was to develop a gas chromatographic system to analyze breath pentane, that addresses the above technical problems and that would provide a simple in vivo method for measuring lipid. n-Pentane and isopentane standards were easily separated from isoprene with a Al2O3/KCI capillary column contained in a portable gas chromatograph equipped with a photoionization detector. The analysis of repeated measures showed a low coefficient of variation for measurements of n-pentane (10%) and isopentane (9%). We measured breath pentane in 27 subjects (15 smokers, 12 non-smokers). There were no significant difference between the baseline and 4 week interval measurements of n-pentane for smokers both before and after cigarette smoking. The within-subject variability data showed that the assay is highly reproducible for both low and high pentane levels in smokers. Smokers were found to have higher levels of both n-pentane and isopentane than non-smokers (P < 0.001). In addition, smokers had further significant elevation of pentane levels 10 min after smoking (P < 0.001), which returned to baseline by 1 h. These studies demonstrate that measurement of breath pentane, using a gas chromatograph with a photoionization detector, is simple and reproducible. Additionally, these results suggest that pentane elevation associated with smoking is secondary to the oxidant effects of cigarette smoke and an important temporal relationship exists between cigarette smoking and breath sample analysis. PMID:8953161

Mohler, E R; Reaven, P; Stegner, J E; Fineberg, N S; Hathaway, D R



A survey and measurement of residues of lindane (organochlorine pesticides) in four species of the most consumed fish in the Caspian Sea (Iran).  


In this study, samples of four species of the most consumed fish (sefid, koli, kilca and kafal fish) were analysed for concentrations of lindane (organochlorine pesticides). Fish were caught using electric fishing at four sites (Chalous and Babolsar cities, Khazar Abad and Miankaleh regions) in the Mazandaran provinces of Iran. Quantitative determination of the lindane was performed by gas chromatography electron-capture detection (GC-ECD). Samples contained detectable concentrations of lindane, but at concentrations below the maximum residue limit (MRL). No differences were found in the lindane concentrations between the types of fish at each site, but there were two groups of sites that were significantly different from one another in terms of lindane concentrations: sites II-IV < site I (P <0.05). However, the concentrations of lindane residues in the muscle were found to be less than the FAO/WHO (1993) recommended permissible intake and should not be of public concern in Mazandaran province. PMID:16572712

Ebadi, A G; Shokrzadeh, M



Naturally fractured tight gas reservoir detection optimization. Quarterly report, July--September 1994  

SciTech Connect

This report details the field work undertaken by Coleman Energy and Environmental Systems--Blackhawk Geosciences Division (CEES-BGD) and Lynn, Inc. during the summer of 1994 at a gas field in the Wind River Basin in central Wyoming. The field work described herein consisted of two parts: multicomponent feasibility studies during the 3D P-wave survey on the site, and 9C VSP in a well at the site. The objectives of both surveys were to characterize the nature of anisotropy in the reservoir. With the 9C VSP, established practices were used to achieve this objective in the immediate vicinity of the well. With the multicomponent studies, tests were conducted to establish the feasibility of surface recording of the anisotropic reservoir rocks.




Evaluation of the backpressure technique for blockage detection in gas flowlines  

SciTech Connect

As longer, full well-stream flowlines are utilized to reduce the costs of deep water and satellite developments, routine production monitoring attains a new level of importance. Of particular interest is the operational impact that blocking agents such as paraffins, asphaltenes, hydrates, and scale can have on the flowlines. Because blockages can reduce and even disrupt production, monitoring flowline performance becomes an economic necessity. This paper considers the application of the backpressure technique as a means of monitoring the growth of blockages in gas flowlines. Using only routine production data, this method quantifies partial blockages by comparing production data to a baseline performance curve. Experimental verification was performed using the LSU 9,460 ft. flowloop of 4-1/2 inch drillpipe. Multirates tests were conducted using methane at 450--610 psig with partial blockages placed in the flowloop. Good agreement with the backpressure model was observed.

Scott, S.L.; Satterwhite, L.A. [Louisiana State Univ., Baton Rouge, LA (United States). Petroleum Engineering Dept.



Elemental speciation analysis by multicapillary gas chromatography with microwave-induced plasma atomic spectrometric detection.  


Multicapillary column gas chromatography (MC-GC)/microwave-induced plasma atomic emission spectrometry (MIP AES) was developed for fast speciation analysis of organotin compounds in the environment. Ethylated butyltin compounds could be separated isothermally within less than 30 s (instead of ?5-10 min) without sacrificing either the resolution or the sample capacity of conventional capillary GC with oven temperature gradient programming. Careful optimization of the pressure and temperature GC program allowed a comprehensive organotin speciation analysis including phenyltin compounds within less than 2.5 min, increasing the sample throughput 6-fold. Compatibility of MC-GC with an MIP atomic emission detector (MIP-AED) was discussed. MC-GC/MIP-AES was validated for the analysis of sediment (PACS-1 and BCR 462) and biological (NIES11) certified reference materials. PMID:21639152

Rodriguez Pereiro, I; Schmitt, V O; Lobi?ski, R



Sample preparation methods for beeswax characterization by gas chromatography with flame ionization detection.  


New and simpler methods of sample preparation to determine several families of compounds in beeswax by conventional and high temperature gas chromatography are proposed. To analyze hydrocarbons and palmitates, a dilution of sample is enough whereas for the total acid content, a hydrolysis and simultaneous methylation with BF3-methanol results more effective than the usual methods; for the total content of alcohols, a further acetylation with acetic anhydride is necessary. Free alcohols are directly acetylated in a sample dissolution but for free acids and monoesterified 1,2,3-propanetriols analysis, a previous extraction with acetonitrile is required. The concentrations of all the compounds studied are expressed in weight percentage referred only to one standard: octadecyl octadecanoate. The precision of the analytical methods has been evaluated showing its importance in the analysis of beeswaxes used in apiculture. PMID:16854423

Jiménez, J J; Bernal, J L; del Nozal, M A J; Martín, M A T; Bernal, J



A Protocol for Detecting and Scavenging Gas-phase Free Radicals in Mainstream Cigarette Smoke  

PubMed Central

Cigarette smoking is associated with human cancers. It has been reported that most of the lung cancer deaths are caused by cigarette smoking 5,6,7,12. Although tobacco tars and related products in the particle phase of cigarette smoke are major causes of carcinogenic and mutagenic related diseases, cigarette smoke contains significant amounts of free radicals that are also considered as an important group of carcinogens9,10. Free radicals attack cell constituents by damaging protein structure, lipids and DNA sequences and increase the risks of developing various types of cancers. Inhaled radicals produce adducts that contribute to many of the negative health effects of tobacco smoke in the lung3. Studies have been conducted to reduce free radicals in cigarette smoke to decrease risks of the smoking-induced damage. It has been reported that haemoglobin and heme-containing compounds could partially scavenge nitric oxide, reactive oxidants and carcinogenic volatile nitrosocompounds of cigarette smoke4. A 'bio-filter' consisted of haemoglobin and activated carbon was used to scavenge the free radicals and to remove up to 90% of the free radicals from cigarette smoke14. However, due to the cost-ineffectiveness, it has not been successfully commercialized. Another study showed good scavenging efficiency of shikonin, a component of Chinese herbal medicine8. In the present study, we report a protocol for introducing common natural antioxidant extracts into the cigarette filter for scavenging gas phase free radicals in cigarette smoke and measurement of the scavenge effect on gas phase free radicals in mainstream cigarette smoke (MCS) using spin-trapping Electron Spin Resonance (ESR) Spectroscopy1,2,14. We showed high scavenging capacity of lycopene and grape seed extract which could point to their future application in cigarette filters. An important advantage of these prospective scavengers is that they can be obtained in large quantities from byproducts of tomato or wine industry respectively11,13 PMID:22230844

Yu, Long-Xi; Dzikovski, Boris G.; Freed, Jack H.



Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305.  


Integral field optical spectroscopy with the INTEGRAL fiber-fed system and Hubble Space Telescope optical imaging are used to map the complex stellar and warm ionized gas structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images reconstructed from wavelength-delimited extractions of the integral field spectra reveal that the observed ionized gas distribution is decoupled from the stellar main body of the galaxy, with the dominant continuum and emission-line regions separated by projected distances of up to 7.5 kpc. The two optical nuclei are detected as apparently faint emission-line regions, and their optical properties are consistent with being dust-enshrouded weak [O i] LINERs. The brightest emission-line region is associated with a faint (mI=20.4), giant H ii region of 600 pc diameter, in which a young ( approximately 5 Myr) massive cluster of about 2x107 M middle dot in circle dominates the ionization. Internal reddening toward the line-emitting regions and the optical nuclei ranges from 1 to 8 mag in the visual. Taking the reddening into account, the overall star formation in IRAS 12112+0305 is dominated by starbursts associated with the two nuclei and corresponds to a star formation rate of 80 M middle dot in circle yr-1. PMID:10727379

Colina; Arribas; Borne; Monreal



SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars  

NASA Technical Reports Server (NTRS)

We present a review of precursor observing programs for the SIM PlanetQuest Key project devoted to detecting Jupiter mass planets around young stars. In order to ensure that the stars in the sample are free of various sources of astrometric noise that might impede the detection of planets, we have initiated programs to collect photometry, high contrast images, interferometric data and radial velocities for stars in both the Northern and Southern hemispheres. We have completed a high contrast imaging survey of target stars in Taurus and the Pleiades and found no definitive common proper motion companions within one arcsecond (140 AU) of the SIM targets. Our radial velocity surveys have shown that many of the target stars in Sco-Cen are fast rotators and a few stars in Taurus and the Pleiades may have sub-stellar companions. Interferometric data of a few stars in Taurus show no signs of stellar or sub-stellar companions with separations of <5 mas. The photometric survey suggests that approximately half of the stars initially selected for this program are variable to a degree (1(sigma) >0.1 mag) that would degrade the astrometric accuracy achievable for that star. While the precursor programs are still a work in progress, we provide a comprehensive list of all targets ranked according to their viability as a result of the observations taken to date. By far, the observable that removes the most targets from the SIM-YSO program is photometric variability.

Tanner, Angelle; Beichman, Charles; Akeson, Rachel; Ghez, Andrea; Grankin, Konstantin N.; Herbst, William; Hillenbrand, Lynne; Huerta, Marcos; Konopacky, Quinn; Metchev, Stanimir; Mohanty, Subhanjoy; Prato, L.; Simon, Michal



Detecting "Temperate" Jupiters: The Prospects of Searching for Transiting Gas Giants in Habitability Zones  

E-print Network

This paper investigates the effects of observing windows on detecting transiting planets by calculating the fraction of planets with a given period that have zero, one (single), two (double), or $\\ge$3 (multiple) transits occurring while observations are being taken. We also investigate the effects of collaboration by performing the same calculations with combined observing times from two wide-field transit survey groups. For a representative field of the 2004 observing season, both XO and SuperWASP experienced an increase in single and double transit events by up to 20-40% for planets with periods 14 planets with periods 14-150 days should have been observed at least once. For the SuperWASP Project, 50-90% of planets with periods between 14-150 days should have been observed at least once. If XO and SuperWASP combined their observations, 50-100% of planets with periods less than 20 days should be observed three or more times. We find that in general wide-field transit surveys have selected appropriate observing strategies to observe a significant fraction of transiting giant planets with semimajor axes larger than the Hot Jupiter regime. The actual number of intermediate-period transiting planets that are detected depends upon their true semimajor axis distribution and the signal-to-noise of the data.

S. W. Fleming; S. R. Kane; P. R. McCullough; F. R. Chromey



SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars  

E-print Network

We present a review of precursor observing programs for the SIM PlanetQuest Key project devoted to detecting Jupiter mass planets around young stars. In order to ensure that the stars in the sample are free of various sources of astrometric noise that might impede the detection of planets, we have initiated programs to collect photometry, high contrast images, interferometric data and radial velocities for stars in both the Northern and Southern hemispheres. We have completed a high contrast imaging survey of target stars in Taurus and the Pleiades and found no definitive common proper motion companions within one arcsecond (140 AU) of the SIM targets. Our radial velocity surveys have shown that many of the target stars in Sco-Cen are fast rotators and a few stars in Taurus and the Pleiades may have sub-stellar companions. Interferometric data of a few stars in Taurus show no signs of stellar or sub-stellar companions with separations of 0.1 mag) that would degrade the astrometric accuracy achievable for that star. While the precursor programs are still a work in progress, we provide a comprehensive list of all targets ranked according to their viability as a result of the observations taken to date. By far, the observable that moves the most targets from the SIM-YSO program is photometric variability.

Angelle Tanner; Charles Beichman; Rachel Akeson; Andrea Ghez; Konstantin N. Grankin; William Herbst; Lynne Hillenbrand; Marcos Huerta; Quinn Konopacky; Stanimir Metchev; Subhanjoy Mohanty; L. Prato; Michal Simon}



Photoionization/flame-ionization detection of atmospheric hydrocarbons after capillary gas chromatography  

SciTech Connect

A ''gastight, low-volume'' photoionization detector (PID) has been constructed for the purpose of detecting trace hydrocarbons in atmospheric samples. This modified PID, in tandem with an FID (flame-ionization detector), was tested by use of a standard gaseous mixture of aromatics, alkenes, and alkanes. The average minimum detectable amounts for the PID were found to be 1.2 pg for aromatics, 2.0 pg for alkenes, and 8.6 pg for alkanes. When the detector was operated in tandem with a standard flame ionization detector, PID/FID response ratios normalized to toluene produced values that could be used to classify hydrocarbons according to their degree of saturation. Normalized PID/FID ratios for alkanes were found to range from 0 to 43, alkenes from 44 to 88, and aromatics from 75 to 158. Using this ratio criteria an ambient air sample was detemined to contain 52% alkanes, 14% alkenes, and 34% aromatics by weight excluding C/sub 2/ hydrocarbons. 4 figures, 2 tables.

Nutmagul, W. (Washington State Univ., Pullman); Cronn, D.R.; Hill, H.H. Jr.



Gas chromatography/ion mobility spectrometry as a hyphenated technique for improved explosives detection and analysis  

NASA Technical Reports Server (NTRS)

Ion Mobility Spectrometry (IMS) is currently being successfully applied to the problem of on-line trace detection of plastic and other explosives in airports and other facilities. The methods of sample retrieval primarily consist of batch sampling for particulate residue on a filter card for introduction into the IMS. The sample is desorbed into the IMS using air as the carrier and negative ions of the explosives are detected, some as an adduct with a reagent ion such as Cl(-). Based on studies and tests conducted by different airport authorities, this method seems to work well for low vapor pressure explosives such as RDX and PETN, as well as TNT that are highly adsorptive and can be found in nanogram quantities on contaminated surfaces. Recently, the changing terrorist threat and the adoption of new marking agents for plastic explosives has meant that the sample introduction and analysis capabilities of the IMS must be enhanced in order to keep up with other detector developments. The IMS has sufficient analytical resolution for a few threat compounds but the IMS Plasmogram becomes increasingly more difficult to interpret when the sample mixture gets more complex.

Mercado, AL; Marsden, Paul



Mitigation of Memory Effects in Beta Scintillation Cells for Radioactive Gas Detection  

SciTech Connect

The Automated Radioxenon Sampler/Analyzer (ARSA) developed at PNNL measures the relative concentrations of xenon isotopes using a ?-? coincidence system. Previous tests of the ARSA system have shown that latent radioactivity remains in the plastic cells after evacuation of the gases, leading to a “memory effect” in which the background count rate is dependent on the sample history. The increased background results in lower detection sensitivity. Two possible solutions to the memory effect are explored in this work: depositing a thin layer of metal on the plastic cell (“metallization”), and using an inorganic scintillating cell composed of yttrium aluminum perovskite (YAP). In both cases, the presence of inorganic material at the surface is intended to inhibit the diffusion of gases into the cell walls.

Seifert, Carolyn E.; McIntyre, Justin I.; Antolick, Kathryn C.; Carman, April J.; Cooper, Matthew W.; Hayes, James C.; Heimbigner, Tom R.; Hubbard, C. W.; Litke, Kevin E.; Ripplinger, Mike D.; Suarez, Reynold



Feasibility of an on-line fission-gas-leak detection system  

NASA Technical Reports Server (NTRS)

Calculations were made to determine if a cladding failure could be detected in a 100-kW zirconium hydride reactor primary system by monitoring the highly radioactive NaK coolant for the presence of I-131. The system is to be completely sealed. A leak of 0.01 percent from a single fuel pin was postulated. The 0.364-MeV gamma of I-131 could be monitored on an almost continuous basis, while its presence could be varified by using a longer counting time for the 0.638-MeV gamma. A lithium-drifted germanium detector would eliminate radioactive corrosion product interference that could occur with a sodium iodide scintillation detector.

Lustig, P. H.



Gas sensor based on nano ZSM-5 zeolite films for the nerve agent simulant dimethylmethylphosphonate detection  

NASA Astrophysics Data System (ADS)

The piezoelectric sensor device coated with nanosize ZSM-5 zeolite films has beem fabricated. The Nerve agent simulant Dimethylmethylphosphonate has been tested with this piezoelectric sensor devices. The frequency shifts to time at 1 ppm, 5ppm and 20ppm DMMP are examined respectively. The minimum detection concentration of 1ppm DMMP has been obtained in the N2 at 293K. 1 ppm is lower than the EC50 concentration value (where EC50 is the airborne concentration sufficient to induce severe effects in 50% of those exposed for 30 min). The frequency sensitivity was found to be about 60HZ / ppm. The effect of acetone on the ZSM-5 zeolite film was also investigated for the selectivity test. Using principle component analysis (PCA), we can qualify and quantify these testing gases.

Xie, Haifen; Ting, Yu; Sun, Xiaoxiang; Jia, Zhou; Huang, Yiping



Determination of free amino compounds in betalainic fruits and vegetables by gas chromatography with flame ionization and mass spectrometric detection.  


Amino acids and amines are the precursors of betalains. Therefore, the profiles of free amino compounds in juices obtained from cactus pears [Opuntia ficus-indica (L.) Mill. cv. Bianca, cv. Gialla, and cv. Rossa], pitaya fruits [Selenicereus megalanthus (K. Schumann ex Vaupel) Moran, Hylocereus polyrhizus (Weber) Britton & Rose, and Hylocereus undatus (Haworth) Britton & Rose], and in extracts from differently colored Swiss chard [Beta vulgaris L. ssp. cicla (L.) Alef. cv. Bright Lights] petioles and red and yellow beets (B. vulgaris L. ssp. vulgaris var. conditiva Alef. cv. Burpee's Golden) were investigated for the first time. Amino compounds were derivatized with propyl chloroformate. While gas chromatography (GC) with mass spectrometry was used for peak assignment, GC flame ionization detection was applied for quantification of individual compounds. Whereas proline was the major free amino compound of cactus pear and pitaya fruit juices, glutamine dominated in Swiss chard stems and beets, respectively. Interestingly, extremely high concentrations of dopamine were detected in Swiss chard stems and beets. Furthermore, the cleavage of betaxanthins caused by derivatization in alkaline reaction solutions is demonstrated for the first time. Amino acids and amines thus released might increase the actual free amino compound contents of the respective sample. To evaluate the contribution of betaxanthin cleavage to total amino acid and amine concentration, isolated betaxanthins were derivatized according to the "EZ:faast" method prior to quantification of the respective amino compounds released. On a molar basis, betaxanthin contribution to overall amino compound contents was always below 6.4%. PMID:16756361

Kugler, Florian; Graneis, Stephan; Schreiter, Pat P-Y; Stintzing, Florian C; Carle, Reinhold



Determination of physiological levels of volatile organic compounds in blood using static headspace capillary gas chromatography with serial triple detection.  


A static capillary gas chromatographic method using three different detectors [photoionization detector (PID), electron capture detector (ECD) and flame ionization detector (FID)] switched in series is presented for the determination of volatile organic compounds (VOCs) in sub microgram l-1 levels. The method was applied for the analysis of selected environmentally and occupationally relevant non-halogenated and chlorinated aromatic hydrocarbons (e.g., benzene, toluene, xylenes, dichlorobenzenes) as well as chlorinated aliphatic hydrocarbons (e.g., trichloroethene, tetrachloroethene) in blood samples. Detailed investigations, in respect to the figures of merit were carried out. For most of the selected VOCs detection limits (calculated as the three-fold standard deviation of low level calibration standards) in the range from 26 (benzene) to 67 ng l-1 (m/p-xylene) were achieved which are comparable with those reported for dynamic headspace techniques in combination with mass spectrometric detection. For the individual VOCs the within-series precision varied from 4 to 19% and the day-to-day precision from 11 to 28%. Regarding PID as well as FID the calibration graphs for all substances were linear up to at least 10 micrograms l-1 while the ECD response was linear up to concentrations of about 0.6 microgram l-1 for the halogenated compounds. Our method is applicable for the quantitative determination of VOCs in blood in the occupationally as well as in the physiologically relevant (normal) concentration range. PMID:9684406

Schroers, H J; Jermann, E; Begerow, J; Hajimiragha, H; Chiarotti-Omar, A M; Dunemann, L




PubMed Central

We develop a novel peak detection algorithm for the analysis of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOF MS) data using normal-exponential-Bernoulli (NEB) and mixture probability models. The algorithm first performs baseline correction and denoising simultaneously using the NEB model, which also defines peak regions. Peaks are then picked using a mixture of probability distribution to deal with the co-eluting peaks. Peak merging is further carried out based on the mass spectral similarities among the peaks within the same peak group. The algorithm is evaluated using experimental data to study the effect of different cut-offs of the conditional Bayes factors and the effect of different mixture models including Poisson, truncated Gaussian, Gaussian, Gamma, and exponentially modified Gaussian (EMG) distributions, and the optimal version is introduced using a trial-and-error approach. We then compare the new algorithm with two existing algorithms in terms of compound identification. Data analysis shows that the developed algorithm can detect the peaks with lower false discovery rates than the existing algorithms, and a less complicated peak picking model is a promising alternative to the more complicated and widely used EMG mixture models. PMID:25264474

Kim, Seongho; Ouyang, Ming; Jeong, Jaesik; Shen, Changyu; Zhang, Xiang



Detection of an Extended Human Volatome with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry  

PubMed Central

Background Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF MS) has been proposed as a powerful new tool for multidimensional analysis of complex chemical mixtures. We investigated GCxGC-TOF MS as a new method for identifying volatile organic compounds (VOCs) in normal human breath. Methods Samples of alveolar breath VOCs and ambient room air VOC were collected with a breath collection apparatus (BCA) onto separate sorbent traps from 34 normal healthy volunteers (mean age = 40 yr, SD = 17 yr, male/female = 19/15). VOCs were separated on two serial capillary columns separated by a cryogenic modulator, and detected with TOF MS. The first and second dimension columns were non-polar and polar respectively. Results BCA collection combined with GC×GC-TOF MS analysis identified approximately 2000 different VOCs in samples of human breath, many of which have not been previously reported. The 50 VOCs with the highest alveolar gradients (abundance in breath minus abundance in ambient room air) mostly comprised benzene derivatives, acetone, methylated derivatives of alkanes, and isoprene. Conclusions Collection and analysis of breath VOCs with the BCA-GC×GC-TOF MS system extended the size of the detectable human volatile metabolome, the volatome, by an order of magnitude compared to previous reports employing one-dimensional GC-MS. The size of the human volatome has been under-estimated in the past due to coelution of VOCs in one-dimensional GC analytical systems. PMID:24086492

Phillips, Michael; Cataneo, Renee N.; Chaturvedi, Anirudh; Kaplan, Peter D.; Libardoni, Mark; Mundada, Mayur; Patel, Urvish; Zhang, Xiang



Improved analysis of volatile halogenated hydrocarbons in water by purge-and-trap with gas chromatography and mass spectrometric detection.  


An analytical system composed of a purge-and-trap injection system coupled to gas chromatography with mass spectrometric detection (PTI-GC-MS) specific for the analysis of volatile chlorinated hydrocarbons (VCHCs) (chloroform; 1,1,1-trichloroethane; tetrachloromethane; 1,1,2-trichloroethylene; tetrachloroethylene) and trihalomethanes (THMs) (chloroform; bromodichloromethane; dibromochloromethane; bromoform) in water was optimised. Samples were purged and trapped in a cold trap (-100 degrees C) fed with liquid nitrogen (cryo-concentration). In order to make this method suitable also for only slightly contaminated waters, some modifications were made to PTI sample introduction, in order to avoid any air intake into the system. PTI, GC and MS conditions were optimised for halogenated compound analysis and limits of detection (LOD) were evaluated. The proposed method allows analysis of samples whose concentrations range from microg/L to ng/L. It is, therefore, applicable to drinking waters, in analyses required by law, and to slightly contaminated aqueous matrices, such as those found in remote areas, in environmental monitoring. Moreover, by changing cold trap temperature, even sparkling mineral waters can be analysed, thus avoiding CO2 interference during the cryo-concentration phase. Our method has been successfully used on real samples: tap water, mineral water and Antarctic snow. PMID:16001554

Zoccolillo, Lelio; Amendola, Luca; Cafaro, Claudia; Insogna, Susanna



Fish freshness detection by a computer screen photoassisted based gas sensor array.  


In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be "portable" and "simple". In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8 h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30 min. The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities. PMID:17386509

Alimelli, Adriano; Pennazza, Giorgio; Santonico, Marco; Paolesse, Roberto; Filippini, Daniel; D'Amico, Arnaldo; Lundström, Ingemar; Di Natale, Corrado



Selective detection of gas-phase TNT by integrated optical waveguide spectrometry using molecularly imprinted sol-gel sensing films.  


A chemical sensor was developed to detect the explosive 2,4,6-trinitrotoluene (TNT) utilizing planar integrated optical waveguide (IOW) attenuated total reflection spectrometry. Submicron thick films of organically modified sol-gel polymers were deposited on the waveguide surface as the sensing layer. Sol-gels were molecularly imprinted for TNT using covalently bound template molecules linked to the matrix through 1 or 2 carbamate linkages. Upon chemical cleavage of the template and displacement of the TNT-like pendant groups from the matrix, shape-selective binding sites were created that possess a primary amine group. The amine was used to deprotonate bound TNT yielding an anionic form that absorbs visible light. Binding of TNT and subsequent conversion to the anion results in the attenuation of light propagating through the waveguide, thus creating a spectrophotometric device. Sensitivity can be achieved by taking advantage of the substantial pathlength provided by the use of single mode IOWs. The limit-of-detection to gas-phase TNT was found to be five parts-per-billion (ppbV) in ambient air at a flow rate of 40 mL min(-1) given a 60 s sampling time. The sensor is highly selective for TNT due to the selectivity of binding site recognition of TNT and the subsequent generation of the TNT anion. Response to TNT is not reversible which results in an integrating sensor device which, in theory, can improve the ability to detect small amounts of the explosive if the exposure time is sufficient in length. PMID:17531827

Walker, Natalie R; Linman, Matthew J; Timmers, Margaret M; Dean, Stacey L; Burkett, Colleen M; Lloyd, Julie A; Keelor, Joel D; Baughman, Brandi M; Edmiston, Paul L



Detection of designer steroid methylstenbolone in "nutritional supplement" using gas chromatography and tandem mass spectrometry: elucidation of its urinary metabolites.  


The use of "nutritional supplements" containing unapproved substances has become a regular practice in amateur and professional athletes. This represents a dangerous habit for their health once no data about toxicological or pharmacological effects of these supplements are available. Most of them are freely commercialized online and any person can buy them without medical surveillance. Usually, the steroids intentionally added to the "nutritional supplements" are testosterone analogues with some structural modifications. In this study, the analyzed product was bought online and a new anabolic steroid known as methylstenbolone (2,17?-dimethyl-17?-hydroxy-5?-androst-1-en-3-one) was detected, as described on label. Generally, anabolic steroids are extensively metabolized, thus in-depth knowledge of their metabolism is mandatory for doping control purposes. For this reason, a human excretion study was carried out with four volunteers after a single oral dose to determine the urinary metabolites of the steroid. Urine samples were submitted to enzymatic hydrolysis of glucuconjugated metabolites followed by liquid-liquid extraction and analysis of the trimethylsilyl derivatives by gas chromatography coupled to tandem mass spectrometry. Mass spectrometric data allowed the proposal of two plausible metabolites: 2,17?-dimethyl-16?,17?-dihydroxy-5?-androst-1-en-3-one (S1), 2,17?-dimethyl-3?,16?,17?-trihydroxy-5?-androst-1-ene (S2). Their electron impact mass spectra are compatible with 16-hydroxylated steroids O-TMS derivatives presenting diagnostic ions such as m/z 231 and m/z 218. These metabolites were detectable after one week post administration while unchanged methylstenbolone was only detectable in a brief period of 45 h. PMID:23200734

Cavalcanti, Gustavo de Albuquerque; Leal, Felipe Dias; Garrido, Bruno Carius; Padilha, Monica Costa; de Aquino Neto, Francisco Radler




SciTech Connect

From the first published z {approx}> 3 survey of 21 cm absorption within the hosts of radio galaxies and quasars, Curran et al. found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to have a {lambda} = 1216 A continuum luminosity in excess of L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}, a critical value above which 21 cm has never been detected at any redshift. At these wavelengths, and below, hydrogen is excited above the ground state so that it cannot absorb in 21 cm. In order to apply the equation of photoionization equilibrium, we demonstrate that this critical value also applies to the ionizing ({lambda} {<=} 912 A) radiation. We use this to show, for a variety of gas density distributions, that upon placing a quasar within a galaxy of gas, there is always an ultraviolet luminosity above which all of the large-scale atomic gas is ionized. While in this state, the hydrogen cannot be detected or engage in star formation. Applying the mean ionizing photon rate of all of the sources searched, we find, using canonical values for the gas density and recombination rate coefficient, that the observed critical luminosity gives a scale length (3 kpc) similar that of the neutral hydrogen (H I) in the Milky Way, a large spiral galaxy. Thus, this simple yet physically motivated model can explain the critical luminosity (L {sub 912} {approx} L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}), above which neutral gas is not detected. This indicates that the non-detection of 21 cm absorption is not due to the sensitivity limits of current radio telescopes, but rather that the lines of sight to the quasars, and probably the bulk of the host galaxies, are devoid of neutral gas.

Curran, S. J. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Whiting, M. T., E-mail: [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)



Membrane oxygenator heat exchanger failure detected by unique blood gas findings.  


Failure of components integrated into the cardiopulmonary bypass circuit, although rare, can bring about catastrophic results. One of these components is the heat exchanger of the membrane oxygenator. In this compartment, unsterile water from the heater cooler device is separated from the sterile blood by stainless steel, aluminum, or by polyurethane. These areas are glued or welded to keep the two compartments separate, maintaining sterility of the blood. Although quality control testing is performed by the manufacturer at the factory level, transport presents the real possibility for damage. Because of this, each manufacturer has included in the instructions for use a testing procedure for testing the integrity of the heat exchanger component. Water is circulated through the heat exchanger before priming and a visible check is made of the oxygenator bundle to check for leaks. If none are apparent, then priming of the oxygenator is performed. In this particular case, this procedure was not useful in detecting communication between the water and blood chambers of the oxygenator. PMID:24779125

Hawkins, Justin L



Parameter optimization of a microfabricated surface acoustic wave sensor for inert gas detection  

SciTech Connect

This work is related to designing, fabricating, and testing a surface acoustic wave sensor to be used for detecting metastable inert gases, particularly helium. The assembly consists of two microsensor configurations: (a) a reference device with no deposition at the delay line and (b) a sensing device with an Au-activated TiO{sub 2} e-beam-deposited thin film on the delay line. The interdigitated transducers and delay lines are fabricated by photolithography techniques on a single Y-cut LiNbO{sub 3} substrate oriented for Z-propagation of the acoustic waves. Variation in electrical conductivity of the Au-activated TiO{sub 2} film due to exposure to metastable He is translated as a frequency change in the assembly. Various characteristics of the surface acoustic microsensor have been studied to better understand and optimize the variation of acoustic wave velocity and the operating frequency of the microdevice. Methods for the TiO{sub 2} thin-film deposition are discussed.

Ahuja, S.; Ross, C.; Chien, H.T.; Raptis, A.C. [and others



Study of chlorothalonil photodegradation in natural waters and in the presence of humic substances.  


Photodegradation of chlorothalonil was studied in different natural waters (sea, river and lake) as well as in distilled water under natural and simulated solar irradiation. The effect of dissolved organic matter (DOM) such as humic and fulvic substances on the photodegradation rate of chlorothalonil was also studied in simulated sunlight. The presence of DOM enhanced the photodegradation of chlorothalonil with the exception of seawater. The kinetics were determined through gas chromatography electron capture detection (GC/ECD) and the photodegradation proceeds via pseudo-first-order reaction in all cases. Half-life ranged from 1 to 48 h. In natural and humic water chlorothalonil photodegradation gave rise to two different intermediates compared to distilled water demonstrating that the transformation of chlorothalonil depend on the constitution of the irradiated media and especially from DOM. The byproducts identified by GC/MS techniques were: chloro-1,3-dicyanobenzene, dichloro-1,3-dicyanobenzene, trichloro-1,3-dicyanobenzene and benzamide. PMID:12222789

Sakkas, Vasilios A; Lambropoulou, Dimitra A; Albanis, Triantafyllos A



Determination of Pyrethroids through Liquid-Liquid Extraction and GC-ECD  

NASA Astrophysics Data System (ADS)

Storm water samples from various locations in San Diego Creek and Newport Bay watershed, southern California, were taken to study the occurrence and fate of pyrethroids. This study focused on four commonly used pyrethroids: bifenthrin, cypermethrin, permethrin, and fenpropathrin. Since the ban of DDT, usage of pyrethroids became an effective second choice. However, pyrethroids are extremely toxic to fish and aquatic organisms. They can pass through secondary wastewater treatment system, causing the final effluent to be in lethal doses to aquatic invertebrates and some insects such as mayflies. Hence, it is necessary to monitor the amount of pyrethroid concentration in storm water. As a part of this study, I attended the RISE internship program at Stanford University in this summer. In the seven weeks, I learned liquid-liquid extraction, water-bath evaporation, nitrogen evaporation, and gas chromatography-electron capture detector techniques to extract and detect the pyrethroid residues in the water sample.

Ding, B.



Effects of washing, peeling, storage, and fermentation on residue contents of carbaryl and mancozeb in cucumbers grown in greenhouses.  


Cucumbers grown in two different greenhouses were exposed to mancozeb and carbaryl at different times. The effects of 10-day preharvest period, water and detergent washing, peeling, predetermined storage period at 4°C (refrigeration), and fermentation on the reduction of residue levels in the plant tissues were investigated. Mancozeb and carbaryl residues in cucumbers were determined by gas chromatography-electron capture detection. Results showed that residue levels in samples, which were collected after 10 days following the pesticide application, were significantly lower than the samples collected after 2 h subsequent to the pesticide application. The culinary applications were effective in reducing the residue levels of the pesticides in cucumbers. As a result, non-fermentative pickling in sodium chloride and acetic acid was the most effective way to reduce the mancozeb and carbaryl residues of the cucumbers. PMID:25342670

Saravi, Ss Saeedi; Shokrzadeh, M



Lindane residues in cultivated cucumber and in the most consumed fish in Caspian Sea (Iran).  


In this study, the concentrations of lindane residues (organochlorine pesticides) were analyzed in samples of cultivated cucumbers (Cucumis sativus L.) and four species of most consumed fish (Sefid, Koli, Kilca and Kafal fish). Samples of cucumber were collected from five sites in Sari city (north, south, east, west and central areas) and samples of fish were caught using electric fishing from four major fishing centers (Chalous and Babolsar cities, Khazar Abad and Miankaleh regions) in Mazandaran province of Iran. Quantitative determination of the lindane content was performed by gas chromatography electron-capture detection (GC-ECD). The results showed that the concentration of lindane in cucumber samples and in the dorsal muscle of the selected fish were less than the Food and Agriculture Organization/World Health Organization (FAO/WHO) recommended intake. PMID:19825858

Shokrzadeh, M; Saeedi Saravi, S S; Zehtab Yazdi, Y



Determination of PCBs in fish using enzyme-linked immunosorbent assay (ELISA)  

USGS Publications Warehouse

Polychlorinated biphenyls (PCBs) were determined in fish tissue using an enzyme-linked immunosorbent assay (ELISA). Standard curves for Aroclor 1248, 1254, and 1260 in catfish tissue were developed with ranges from 0.05 to 0.5 ppm and 0.5 to 5.0 ppm. Wild fish were initially analyzed using gas chromatography/electron-capture detection (GC/ECD) and those having residues within the standard curve ranges were analyzed with ELISA. Results obtained using ELISA and GC/ECD were not significantly different (p < 0.05) from 0.05 to 0.5 ppm. From 0.5 to 5.0 ppm, the standard curve for Aroclor 1254 was the best predictor of total PCB in wild fish samples.

Lasrado, J.A.; Santerre, C.R.; Zajicek, J.L.; Stahl, J.R.; Tillitt, D.E.; Deardorff, D.



Simultaneous determination of anthraquinones in radix Polygoni multiflori by capillary gas chromatography coupled with flame ionization and mass spectrometric detection.  


A rapid, accurate and reliable analytical method was developed for the simultaneous determination of five major anthraquinones, aloe-emodin, chrysophanol, emodin, physcion, and rhein, in radix Polygoni multiflori, a traditional Chinese herbal medicine. The method comprises a fast ultrasonic extraction with methanol and derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)+1% trimethylchlorosilane (TMCS) followed by capillary gas chromatographic (GC) separation. The effect of reaction time on the derivatization of anthraquinones was examined. A baseline separation of the anthraquinone and internal standard derivatives was achieved in 15min. The detection limits range from 0.22 to 0.60microg/mL for the five anthraquinones. The calibration curves are linear over the concentration range studied (from the detection limits to 40.0microg/mL) with the squares of correlation coefficients, R2, greater than 0.998. The developed method was successfully applied to the simultaneous determination of anthraquinones in radix P. multiflori samples. The peak identification was confirmed using GC-MS. The contents of anthraquinones in radix P. multiflori samples studied were 27.41, 289.6, 64.22, 202.1, 288.6microg/g for chrysophanol, emodin, aloe-emodin, physcion, rhein, respectively. All relative standard deviations are less than 3.2%. The recoveries range from 80.2% to 119.3% for the five analytes. To the authors' best knowledge, this is the first GC method reported for the simultaneous determination of the five anthraquinones in radix P. multiflori. PMID:18262194

Zuo, Yuegang; Wang, Chengjun; Lin, Yuejuan; Guo, Jinwen; Deng, Yiwei



Gas chromatographic-mass spectrometry method for the detection of busulphan and its metabolites in plasma and urine.  


Busulphan is an alkylating agent used as conditioning regimen prior to stem cell transplantation. Busulphan is metabolized in the liver and four major metabolites have been identified. The first metabolite is tetrahydrothiophene which is oxidized to tetrahydrothiophene 1-oxide, then sulfolane and finally 3-hydroxy sulfolane. Despite the low molecular weight and wide polarity range of busulphan and its four metabolites, the use of a fused silica non-polar column significantly enhanced the automated gas chromatography-mass spectrometry of their detection in one simple method. The limit of quantification was 0.5?M for busulphan and all its metabolites except 3-OH sulfolane, which was 1.25?M. This method was validated for all the compounds in both human plasma and urine. Lower limits of quantifications (LLOQs) were run in pentaplicate per compound and all results were within 20% of the nominal values. The recovery was determined by comparing the peak area of two quality control (QC) samples, before and after extraction in plasma and urine, in triplicate. Acceptable precision and accuracy have been obtained; at least 3 standard curves have been run for each compound using three different QCs covering the calibration curve in triplicate. The QC values were within 15% (SD) of the nominal values. Selectivity and sensitivity of all compounds have been measured. Compounds were stable up to 50 days after extraction in -20°C and 48h at RT. Moreover, the compounds were stable for three cycles of freezing and thawing. The method was applied in a clinical case where the patient received high dose busulphan; all the compounds have been detected, identified and quantified both in plasma and urine. PMID:23286981

El-Serafi, Ibrahim; Terelius, Ylva; Twelkmeyer, Brigitte; Hagbjörk, Ann-Louise; Hassan, Zuzana; Hassan, Moustapha




E-print Network

In this work, we focus on the mainly detection of buildings.. As input data, we use LIDAR data and multispectral aerial images of two different test sites. One is from Zurich airport and the other one is from Vaihingen region close to Stuttgart. Quality assessment has been performed by comparing our results with existing reference data which are generated using commercial photogrammetric software and manual stereo measurement. 1.

unknown authors


Determination of polycyclic aromatic sulfur heterocycles in diesel particulate matter and diesel fuel by gas chromatography with atomic emission detection.  


The sulfur content of diesel fuel is of environmental concern because sulfur can facilitate the formation of diesel particulate matter (DPM) and sulfur dioxide (SO2) in the exhaust can poison catalytic converters. The US Environmental Protection Agency (EPA) has established more stringent regulations to reduce the sulfur content of diesel fuels in the near future. In this study, various types of organosulfur compounds in DPM extracts and the corresponding fuels have been determined by gas chromatography with atomic emission detection. The diesel fuels used have sulfur contents of 2284 and 433 ppm, respectively, and are labeled as high-sulfur and low-sulfur diesel fuels. The compounds identified are mainly polycyclic aromatic sulfur heterocycles (PASHs). In the fuels tested, trimethylbenzothiophenes (TMBTs), dibenzothiophenes (DBTs), and 4-methyldibenzothiophene (4-MDBT) were the most abundant sulfur compounds, while larger PASH compounds were more abundant in DPM extracts. The high-sulfur diesel fuel contained a larger proportion of PASHs with one or two rings (lighter PASHs). In DPM, the concentrations of total organic sulfur and individual PASHs are higher for the high-sulfur diesel fuel, and the relative percentage of one or two-ring PASHs is higher as well. The influence of engine load on the DPM composition was also examined. With increasing load, the PASH concentration in DPM decreased for lighter PASHs, increased for heavier PASHs, and had a bell-shaped distribution for PASHs in between. PMID:16574137

Liang, Fuyan; Lu, Mingming; Birch, M Eileen; Keener, Tim C; Liu, Zifei



Field detection of bacillus spore aerosols with stand-alone pyrolysis-gas chromatography and ion mobility spectrometry  

NASA Astrophysics Data System (ADS)

A commercially available, hand-held chemical vapor detector was modified to detect Gram-positive Bacillus subtilis var. globigii spores (BG) in outdoor field scenarios. An Airborne Vapor Monitor (AVM) ion mobility spectrometry (IMS) vapor detector was interfaced to a biological sample processing and transfer introduction system. The biological sample processing was accomplished by quartz tube pyrolysis (Py), and the resultant vapor was transferred by gas chromatography (GC) to the IMS detector. The Py-GC/IMS system can be described as a hyphenated device where two analytical dimensions, in series, allow the separation and isolation of individual components from the pyrolytic decomposition of biological analytes. Gram positive spores such as BG contain 5 - 15% by weight of dipicolinic acid (DPA), and picolinic acid is a pyrolysis product of DPA. Picolinic acid has a high proton affinity, and it is detected in a sensitive fashion by the atmospheric pressure-based IMS device. Picolinic acid occupies a unique region in the GC/IMS data domain with respect to other bacterial pyrolysis products. A 1000 to 1, air-to-air, aerosol concentrator was interfaced to the Py-GC/IMS instrument, and the system was placed in an open-air, Western United States desert environment. The system was tested with BG spore aerosol releases, and the instrument was remotely operated during a trial. A Met-One aerosol particle counter was placed next to the Py-GC/IMS so as to obtain a real-time record of the ambient and bacterial aerosol challenges. The presence/absence of an aerosol event, determined by an aerosol particle counter and a slit sampler-agar plate system, was compared to the presence/absence of a picolinic acid response in a GC/IMS data window at selected times in a trial with respect to a BG challenge. In the 21 BG trials, the Py-GC/IMS instrument experienced two true negatives, no false positives, and the instrument developed a software failure in one trial. The remaining 18 trials were true positive determinations for the presence of BG aerosol, and a limit of detection for the Py-GC/IMS instrument was estimated at approximately 3300 BG spore-containing particles.

Snyder, A.; Maswadeh, Waleed M.; Parsons, John A.; Tripathi, Ashish; Meuzelaar, Henk L. C.; Dworzanski, Jacek P.; Kim, Man-Goo



Sensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas Detection  

E-print Network

research effort has been directed toward the development of hydrogen gas sensors. A number of gas sensorsSensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas, Department of Mechanical Engineering, and Center for Hydrogen and Electrochemical Studies (CHES), University

Mandelis, Andreas


Silicon-micromachined gas chromatography system used to separate and detect ammonia and nitrogen dioxide. I. Design, fabrication, and integration of the gas chromatography system  

Microsoft Academic Search

A miniature gas chromatography (GC) system was designed and developed using silicon micromachining and integrated circuit (IC) processing techniques. The micromachined gas chromatography (MMGC) system is composed of a miniature sample injector incorporating a 10-?m-long sample loop; a 0.9-m-long, rectangular-shaped (300 ?m width and 10 ?m height) capillary column coated with a 0.2-?m-thick copper phthalocyanine (CuPc) stationary phase, and a

Rocky R. Reston; Edward S. Kolesar



The selective detection of C 2H 5OH using SnO 2–ZnO thin film gas sensors prepared by combinatorial solution deposition  

Microsoft Academic Search

Sensing materials for selective detection of C2H5OH were designed using combinatorial solution deposition of SnO2–ZnO thin films. The SnO2–ZnO composite sensor prepared by alternate deposition of 10 droplets of SnO2 and ZnO sols (S50Z50 sensor) showed a high response to 200ppm C2H5OH (S(ethanol)=Ra\\/Rg=4.69, Ra: resistance in air, Rg: resistance in gas) at 300°C, while the gas responses to 100ppm C3H8,

Ki-Won Kim; Pyeong-Seok Cho; Sun-Jung Kim; Jong-Heun Lee; Chong-Yun Kang; Jin-Sang Kim; Seok-Jin Yoon



Intracavity CO laser photoacoustic trace gas detection: cyclic CH 4 , H 2 O and CO 2 emission by cockroaches and scarab beetles  

NASA Astrophysics Data System (ADS)

A liquid-nitrogen-cooled CO laser and an intracavity resonant photoacoustic cell are employed to monitor trace gases. The setup was designed to monitor trace gas emissions of biological samples on line. The arrangement offers the possibility to measure gases at the 10 9 by volume (ppbv) level (e.g., CH 4 , H 2 O) and to detect rapid changes in trace gas emission. A detection limit of 1 ppbv for CH 4 in N 2 equivalent to a minimal detectable absorption of 3 10 9 cm 1 can be achieved. Because of the kinetic cooling effect we lowered the detection limit for CH 4 in air is decreased to 10 ppbv. We used the instrument in a first application to measure the CH 4 and H 2 O emission of individual cockroaches and scarab beetles. These emissions could be correlated with CO 2 emissions that were recorded simultaneously with an infrared gas analyzer. Characteristic breathing patterns of the insects could be observed; unexpectedly methane was also found to be released.

Bijnen, F. G. C.; Harren, F. J. M.; Hackstein, J. H. P.; Reuss, J.



Nanoparticle engineering for gas sensor optimisation: improved sol–gel fabricated nanocrystalline SnO 2 thick film gas sensor for NO 2 detection by calcination, catalytic metal introduction and grinding treatments  

Microsoft Academic Search

The control of the technological steps such as calcination temperature and introduction of catalytic additives are accepted to be key points in the obtaining of improved sol–gel fabricated SnO2 thick film gas sensors with different sensitivity to NO2 and CO. In this work, after proving that the undoped material calcined at 1000°C is optimum for NO2 detection, grinding is added

A. Diéguez; A. Romano-Rodr??guez; J. R. Morante; J. Kappler; N. Bârsan; W. Göpel



Comparison of two derivatization reagents for the simultaneous determination of organolead and organomanganese compounds using solid-phase microextraction followed by gas chromatography with atomic emission detection.  


Two procedures for the simultaneous determination of organolead (tetraethyllead, triethyllead and trimethyllead) and organomanganese compounds (cyclopentadienyl manganese tricarbonyl (CMT) and methylcyclopentadienyl manganese tricarbonyl (MMT)) are studied. Both procedures involve sample preconcentration by solid-phase microextraction and capillary gas chromatography coupled to atomic emission detection, the main difference being the derivatizing agent used for the ionic alkylated lead species: sodium tetrapropylborate (NaBPr(4)) and sodium tetraphenylborate (NaBPh(4)). The parameters affecting the derivatization and preconcentration steps, chromatographic separation as well as detection of the compounds were optimized. Higher sensitivity was attained for all compounds with the method involving propylation derivatization. In this case, detection limits ranged between 0.04 and 0.1 ng L(-1), depending on the compound. Detection limits of between 0.1 and 24.5 ng L(-1) were obtained, when using phenylation derivatization. A low CMT concentration was found in one of the seawater samples analyzed. PMID:22099678

Peñalver, Rosa; Campillo, Natalia; Hernández-Córdoba, Manuel



Quantification of chloroanisoles in cork using headspace solid-phase microextraction and gas chromatography with electron capture detection.  


Chloroanisoles can migrate from the cork stopper in wine bottles to the wine and give it a musty taint so it is important to find a method by which they can be determined. The aim of this paper is to develop a method for quantifying 2,4-dichloroanisole, 2,6-dichloroanisole, 2,4,6-trichloroanisole, 2,3,4,6-tetrachloroanisole and 2,3,4,5,6-pentachloroanisole in cork using headspace solid-phase microextraction and gas chromatography with electron capture detection. After we had prepared the cork standards that were so essential to the work we optimised the parameters that most influence headspace solid-phase microextraction: fibre coating, vial volume, cork, kind and volume of solvent to help the extraction, extraction temperature and time, ionic strength and stirring. The method quantifies the total amount of chloroanisoles in cork stoppers (natural, agglomerated, agglomerated with disks and sparkling wine stoppers), at suitable concentrations so that the capacity of these compounds to give wine a musty taint can be evaluated. The quantification limits are: 2,6-dichloroanisole (8.6 ng/g), 2,4,6-trichloroanisole (0.8 ng/g), 2,4-dichloroanisole (3.5 ng/g), 2,3,4,6-tetrachloroanisole (0.6 ng/g), 2,3,4,5,6-pentachloroanisole (0.8 ng/g). The other quality parameters are: recoveries (90.3-105.8%), repeatability (4-13% (RSD expressed)) and intermediate precision (5-14% (RSD expressed)). PMID:16405979

Riu, M; Mestres, M; Busto, O; Guasch, J



Absorption-line Detections of 105-106 K Gas in Spiral-rich Groups of Galaxies  

NASA Astrophysics Data System (ADS)

Using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, the COS Science Team has conducted a high signal-to-noise survey of 14 bright QSOs. In a previous paper, these far-UV spectra were used to discover 14 "warm" (T >= 105 K) absorbers using a combination of broad Ly? and broad O VI absorptions. A reanalysis of a few of this new class of absorbers using slightly relaxed fitting criteria finds as many as 20 warm absorbers could be present in this sample. A shallow, wide spectroscopic galaxy redshift survey has been conducted around these sight lines to investigate the warm absorber environment, which is found to be spiral-rich groups or cluster outskirts with radial velocity dispersions ? = 250-750 km s-1. While 2? evidence is presented favoring the hypothesis that these absorptions are associated with the galaxy groups and not with the individual, nearest galaxies, this evidence has considerable systematic uncertainties and is based on a small sample size so it is not entirely conclusive. If the associations are with galaxy groups, the observed frequency of warm absorbers (d {N}/dz = 3.5-5 per unit redshift) requires them to be very extended as an ensemble on the sky (~1 Mpc in radius at high covering factor). Most likely these warm absorbers are interface gas clouds whose presence implies the existence of a hotter (T ~ 106.5 K), diffuse, and probably very massive (>1011 M ?) intra-group medium which has yet to be detected directly. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Stocke, John T.; Keeney, Brian A.; Danforth, Charles W.; Syphers, David; Yamamoto, H.; Shull, J. Michael; Green, James C.; Froning, Cynthia; Savage, Blair D.; Wakker, Bart; Kim, Tae-Sun; Ryan-Weber, Emma V.; Kacprzak, Glenn G.



Identification and quantification of alkene-based drilling fluids in crude oils by comprehensive two-dimensional gas chromatography with flame ionization detection.  


Comprehensive two-dimensional gas chromatography with flame ionization detection (GC x GC-FID) was used to measure alkene-based drilling fluids in crude oils. Compared to one-dimensional gas chromatography, GC x GC-FID is more robust for detecting alkenes due to the increased resolution afforded by second dimension separations. Using GC x GC-FID to analyze four oil samples from one reservoir contaminated with the same drilling fluid, C(15), C(16), C(17), C(18) and C(20) alkenes were identified. The drilling fluid that contaminated these samples also differed from another commercially obtained fluid, which only contained C(16) and C(18) alkenes. These results should motivate the petroleum industry to consider GC x GC-FID for measuring drilling fluids. PMID:17376464

Reddy, Christopher M; Nelson, Robert K; Sylva, Sean P; Xu, Li; Peacock, Emily A; Raghuraman, Bhavani; Mullins, Oliver C



Characterization of Volatile Compounds in Chilled Cod (Gadus morhua) fillets by gas chromatography and detection of quality indicators by an electronic nose  

Microsoft Academic Search

Volatile compounds in cod fillets packed in Styrofoam boxes were analyzed during chilled storage (0.5 C) by gas chromatography (GC)-mass spectrometry and GC-olfactometry to screen potential quality indicators present in concentrations high enough for detection by an electronic nose. Photobacterium phosphoreum dominated the spoilage bacteria on day 12 when the fillets were rejected by sensory analysis. Ketones, mainly 3-hydroxy-2-butanone, were

Gudrun Olafsdottir; Rosa Jonsdottir; Hélène L. Lauzon; Joop Luten; Kristberg Kristbergsson



A Multiresidue Method for 20 Pesticides in Radix paeoniae Alba of Chinese Herb by Gas Chromatography with Electron-capture Detection  

Microsoft Academic Search

A rapid multiresidue method was developed for the determination of 20 pesticides in Radix paeoniae Alba of Chinese herb by ultrasonic wave extraction, silica gel column chromatography and gas chromatography (GC) with electron-capture\\u000a detection (ECD) in this study, Mean recoveries of the method ranged from 74.45 to 115.14%. The validation of the proposed\\u000a approach was verified on Isatis indigotica Fort,

Gao Qian; Hua Rimao; Tang Feng; Wu Xiangwei; Li Xuede; Cao Haiqun; Shi Yanhong; Tang Jun



Volatile organo-selenium speciation in biological matter by solid phase microextraction–moderate temperature multicapillary gas chromatography with microwave induced plasma atomic emission spectrometry detection  

Microsoft Academic Search

Microwave induced plasma atomic emission spectrometry (MIP-AES) in combination with multicapillary (MC) gas chromatography could be proven to be useful for element specific detection of volatile species. Solid phase microextraction (SPME) was used for preconcentration and sample-matrix separation. The fiber desorption unit as well as the heating control for the MC column were in-house developed and multicapillary column was operated

C. Dietz; J. Sanz Landaluze; P. Ximénez-Embún; C. Cámara



The study of flow characteristic of gas-liquid two-phase flow based on the near-infrared detection device  

NASA Astrophysics Data System (ADS)

With the importance of the two-phase flow, many scholars pay attention on it; and for the so many parameters in the gas-liquid two-phase flow, flow characteristic is the basis. For the four flow patterns in the vertical direction, slug flow, bubbly flow, annular flow, and milk foam-like flow, the paper used the laser diode of 980nm and the silicon photodiode to detect the flow status. The absorption coefficients of the infrared in the gas and the liquid are very different; at the meantime, the infrared is affected by the interface obviously. As a result, it can reflect the fluctuation of the gas-liquid two-phase flow with the detection by the infrared. By analyzing the experiment data, four characteristic parameters are extracted, such as the average value, the variance, the kurtosis, and the frequency center of gravity. They can not only reflect the change of the different flow patterns, but also can reflect the fluctuation in the same flow pattern. The feature vector constituted of the four characteristic parameters can identify the flow pattern correctly in this system. What's more, it can achieve an accurate measurement of the real-time online, providing a basis for the other parameters' analysis in the gas-liquid two-phase flow.

Fang, Lide; Liang, Yujiao; Zhang, Yao; Zhang, Chen; Gao, Jingzhe



Laboratory Evaluation of an Electrochemical Noise System for Detection of Localized and General Corrosion of Natural Gas Transmission Pipelines  

SciTech Connect

Gas transmission pipelines are susceptible to both internal (gas side) and external (soil side) corrosion attack. Internal corrosion is caused by the presence of salt laden moisture, CO{sub 2}, H{sub 2}S, and perhaps O{sub 2} in the natural gas. Internal corrosion usually manifests itself as general corrosion. However, the presence of chlorides in entrained water also can lead to pitting corrosion damage. The electrochemical noise technique can differentiate general from localized corrosion and provide estimates of corrosion rates without external perturbation of the corroding system. It is increasingly being applied to field and industrial installations for in situ corrosion monitoring. It has been used here to determine its suitability for monitoring internal and external corrosion damage on gas transmission pipelines. Corrosion measurements were made in three types of environments: (1) aqueous solutions typical of those found within gas pipelines in equilibrium with th e corrosive components of natural gas; (2) biologically-active soils typical of wetlands; and (3) a simulated, unpressurized, internal gas/liquid gas pipeline environment. Multiple sensor designs were evaluated in the simulated pipe environment. Gravimetric measurements were conducted in parallel with the electrochemical noise measurements to validate the results.

Bullard, S.J.; Covino, B.S., Jr.; Russell, J.H.; Holcomb, G.R.; Cramer, S.D.; Ziomek-Moroz, M.; Eden, D.



Detection of ethene and other hydrocarbons in gas turbine engine exhaust using non-intrusive FTIR spectroscopy  

Microsoft Academic Search

As part of the EU funded project AEROJET2, a number of gas turbine engine tests were performed in different facilities around Europe. At Farnborough, UK a Spey engine was used to test a suite of prototype optically based instrumentation designed to measure exhaust gas emissions without using extractive probe systems. In addition to the AEROJET 2 prototype instrumentation, a Bruker

Giovanni M. Arrigone; Michael A. Welch; Moira Hilton; Michael N. Miller; Christopher W. Wilson



Gas burner control system  

Microsoft Academic Search

An improved gas burner control system which eliminates the need for a pilot light for operation of a gas burner is described. The system includes a pair of gapped electrical conductors forming a set of ignition points disposed adjacent to a gas burner, a sensor for detecting the presence of the gas to be burned via the gas burner adjacent



Molecular Gas in 3C 293: The First Detection of CO Emission and Absorption in an F-R II Radio Galaxy  

E-print Network

The first detection of CO emission in a Fanaroff-Riley Class II (i.e., edge-brightened radio morphology) radio galaxy is presented. Multi- wavelength (0.36-2.17 micron) imaging of 3C 293 shows it to be a disk galaxy with an optical jet or tidal tail extending towards what appears to be a companion galaxy 28 kpc away via a low surface brightness envelope. The molecular gas appears to be distributed in an asymmetric disk rotating around an unresolved continuum source, which is presumably emission from the AGN. A narrow (approx 60 km/s) absorption feature is also observed in the CO spectrum and is coincident with the continuum source. Using the standard CO conversion factor, the molecular gas mass is calculated to be 1.5x10^10 M_sun, several times the molecular gas mass of the Milky Way. The high concentration of molecular gas within the central 3 kpc of 3C 293, combined with the multiwavelength morphological peculiarities, support the idea that the radio activity has been triggered by a gas-rich galaxy-galaxy interaction or merger event.

A. S. Evans; D. B. Sanders; J. A. Surace; J. M. Mazzarella



Detection of [SiLL] (34.8 micron) emission in Orion-KL: A measurement of the silicon abundance in dense interstellar gas  

NASA Technical Reports Server (NTRS)

The first detection of the ground state fine structure transition of Si+ at a rest wavelength determined to be 34.815 + or - 0.004 micron are reported. These observations were obtained with the facility spectrometer on NASA's Kuiper Airborne Observatory. A 6' NW-SE strip scan across the Orion-KL region shows SiII emission from both the extended photodissociation region surrounding theta 1 Ori C and from the shocked gas NW of BN-KL. The inferred gas-phase silicon elemental abundance relative to hydrogen in the dense 10 to the 5/cc primarily neutral photodissociation region is approximately 2.6 x to the -6, a factor of 0.075 times the solar value and 3.4 times greater than the abundance in the moderate density approx. 10 to the 3/cc cloud toward zeta Oph. The silicon abundance in the shocked gas is approximately solar, indicating that any pre-existing grains have been destroyed in the shock wave or that the preshock gas carries a near solar abundance of gas phase silicon. The shock-excited SiII (34.8 micron) emission may arise from shocked wind material in the outflow around IRc2, with wind velocities approx. 100 km/s.

Haas, M. R.; Hollenbach, D. J.; Erickson, E. F.



Silicon-micromachined gas chromatography system used to separate and detect ammonia and nitrogen dioxide. II. Evaluation, analysis, and theoretical modeling of the gas chromatography system  

Microsoft Academic Search

A miniature gas chromatography (GC) system was designed and developed using silicon micromachining and integrated circuit (IC) processing techniques. The MMGC system can separate parts-per-million (ppm) ammonia and nitrogen dioxide concentrations in less than 30 minutes when isothermally operated (80°C) at 40 psi. The heat of adsorption of nitrogen dioxide (0.38 eV) on a CuPc thin film (0.2 ?m thick)

Edward S. Kolesar; Rocky R. Reston



Detection of optical asymmetry in amino acids by gas chromatography for extraterrestrial space exploration - Results of a new soil processing scheme with breadboard instrumentation  

NASA Technical Reports Server (NTRS)

The life-detection experiments of the Viking spacecraft are of an active biology type that will attempt to elicit metabolic responses from soil samples. Because bioresponses may be difficult to stimulate, it is desirable also to devise a purely chemical life-detection experiment. The unique chemical property of living systems on which such an experiment could be based is the optical activity of the amino acids that compose its protein. We have devised a new soil processing scheme which has been laboratory tested and for which we have built semi-automated breadboard instrumentation. The system involves the operations of heating, filtering, evaporation, conversion of the isolated amino acids to volatile diastereomers, injection onto a gas chromatographic column, and detection using a flame ionization detector. The breadboard form of the soil processing scheme and instrumentation has been successfully end-to-end tested.

Pollock, G. E.; Day, R.; Kinsey, S.; Miller, S. L.



Analytical Method for the Detection of Ozone Depleting Chemicals (ODC) in Commercial Products Using a Gas Chromatograph with an Electron Capture Detector (GC-ECD)  

SciTech Connect

This document describes an analytical procedure that was developed for the trace level detection of residual ozone depleting chemicals (ODC) associated with the manufacture of selected commercial products. To ensure the United States meets it obligation under the Montreal Protocol, Congress enacted legislation in 1989 to impose an excise tax on electronic goods imported into the United States that were produced with banned chemicals. This procedure was developed to technically determine if residual ODC chemicals could be detected on electronic circuit boards. The analytical method utilizes a “purge and trap” technique followed by gas chromatography with electron capture detection to capture and analyze the volatile chemicals associated with the matrix. The method describes the procedure, the hardware, operating conditions, calibration, and quality control measures in sufficient detail to allow the capability to be replicated. This document corresponds to internal Standard Operating Procedure (SOP) EFL-130A, Rev 4.

Lee, Richard N.; Dockendorff, Brian P.; Wright, Bob W.



Comparison of enzyme-linked immunosorbent assay and gas chromatography procedures for the detection of cyanazine and metolachlor in surface water samples  

USGS Publications Warehouse

Enzyme-linked immunosorbent assay (ELISA) data from surface water reconnaissance were compared to data from samples analyzed by gas chromatography for the pesticide residues cyanazine (2-[[4-chloro-6-(ethylamino)-l,3,5-triazin-2-yl]amino]-2-methylpropanenitrile ) and metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide). When ELISA analyses were duplicated, cyanazine and metolachlor detection was found to have highly reproducible results; adjusted R2s were 0.97 and 0.94, respectively. When ELISA results for cyanazine were regressed against gas chromatography results, the models effectively predicted cyanazine concentrations from ELISA analyses (adjusted R2s ranging from 0.76 to 0.81). The intercepts and slopes for these models were not different from 0 and 1, respectively. This indicates that cyanazine analysis by ELISA is expected to give the same results as analysis by gas chromatography. However, regressing ELISA analyses for metolachlor against gas chromatography data provided more variable results (adjusted R2s ranged from 0.67 to 0.94). Regression models for metolachlor analyses had two of three intercepts that were not different from 0. Slopes for all metolachlor regression models were significantly different from 1. This indicates that as metolachlor concentrations increase, ELISA will over- or under-estimate metolachlor concentration, depending on the method of comparison. ELISA can be effectively used to detect cyanazine and metolachlor in surface water samples. However, when detections of metolachlor have significant consequences or implications it may be necessary to use other analytical methods.

Schraer, S.M.; Shaw, D.R.; Boyette, M.; Coupe, R.H.; Thurman, E.M.




EPA Science Inventory

Photofragment fluorescence (PFF) spectroscopy offers real-time monitoring capability with high-analytical sensitivity and selectivity for volatile mercury compounds found in process gas streams, such as incinerator stacks. In this work, low concentrations (6 ppb to...


Detection and quantification of methane and VOC emissions from oil and gas production operations using remote measurements, Interim report  

EPA Science Inventory

Improved understanding of air pollutant emissions from oil and gas production operations is needed. With a steadily increasing number of production sources, the impact of emitted volatile organic compounds (VOCs) on regional ozone is potentially significant. As the separation dis...


Detection of hydrocarbon microseepage in a rain forest environment (Jurua Gas field, northern Brazil) using Landsat MSS data  

SciTech Connect

The Jurua gas field is the first important hydrocarbon accumulation found in the jungle-covered Solimoes basin. The tectonic framework in this area is characterized by a right-lateral transpressional zone (Jurua structural trend). Hydrocarbon traps are anticlines developed along the upthrown block of a reverse fault. The prospective 2,200-m-thick Paleozoic section is unconformably covered by a 2,800-m-thick pile of Mesozoic and Cenozoic continental sediments. Anomalous concentrations of hydrocarbons (C{sub 2}-C{sub 4}) in soil samples are concordantly aligned with the trace of the reverse fault crossing the gas field, indicating that this feature acted as a conduit for hydrocarbon microseepage. Gas-producing wells are located over a tabular watershed which coincides with the northeast-southwest Jurua structural trend. An unsupervised classification of Landsat MSS data over the gas field area reveals that one spectral class of vegetation is aligned with the Jurua structural trend. Field checking shows that the vegetation near the gas-producing well 1-JR-1-AM is not as dense as the forest outside the limits of the Jurua gas field. Two geologic factors may account for the vegetation anomaly over the gas field. (1) The northeast-southwest tabular watershed corresponds to a Pleistocene erosional surface associated with weathering products such as bauxite and laterite. The resulting soil is impermeable and low in nutrients. (2) The spectral behavior of vegetation may represent the response of plants to long-term anaerobic soil conditions brought about by gas leakage from the Paleozoic reservoir.

Miranda, F.P.; Cunha, F.M.B. (Petrobras, New York, NY (USA))



Differentiation of wines according to grape variety using multivariate analysis of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection data.  


Headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GC×GC/TOFMS) was used to analyse the volatiles in five types of wines elaborated with grapes of Cabernet Sauvignon, Merlot, Chardonnay, Sauvignon Blanc and Pinot Noir varieties. Fisher ratio, principal component analysis (PCA) and stepwise linear discriminant analysis (SLDA) were used to develop a discriminant model and, as a result, 12 volatile compounds enabled differentiation and classification of wines according to grape cultivars. A detailed examination of GC×GC/TOFMS data showed that the use of one-dimensional gas chromatography with a mass spectrometric detector (1D-GC/MS) would probably result in misidentification of some of these 12 compounds, as they showed partial coelution with other components in the first chromatographic dimension. PMID:23993563

Welke, Juliane Elisa; Manfroi, Vitor; Zanus, Mauro; Lazzarotto, Marcelo; Alcaraz Zini, Cláudia



Determination of Low Concentrations of Acetochlor in Water by Automated Solid-Phase Extraction and Gas Chromatography with Mass-Selective Detection  

USGS Publications Warehouse

A sensitive and reliable gas chromatographic/mass spectrometric (GC/MS) method for determining acetochlor in environmental water samples was developed. The method involves automated extraction of the herbicide from a filtered 1 L water sample through a C18 solid-phase extraction column, elution from the column with hexane-isopropyl alcohol (3 + 1), and concentration of the extract with nitrogen gas. The herbicide is quantitated by capillary/column GC/MS with selected-ion monitoring of 3 characteristic ions. The single-operator method detection limit for reagent water samples is 0.0015 ??g/L. Mean recoveries ranged from about 92 to 115% for 3 water matrixes fortified at 0.05 and 0.5 ??g/L. Average single-operator precision, over the course of 1 week, was better than 5%.

Lindley, C.E.; Stewart, J.T.; Sandstrom, M.W.



Detection of Urinary Metabolomics before and after Pringle Maneuver-Induced Liver Ischemia and Reperfusion Injury in Rats Using Gas Chromatography-Mass Spectrometry  

PubMed Central

Background. Metabolomics studies can quantitatively detect the dynamic metabolic response of living systems. Objective. To detect urinary metabolomics after hepatic ischemia/reperfusion (I/R) injury induced by the Pringle maneuver using gas chromatography-mass spectrometry (GC-MS). Methods. Male Sprague-Dawley rats (N = 80) were randomly divided into 4 groups (n = 20/group): sham operation, day 1, day 3, and day 5. Rats in the day 1, day 3, and day 5 groups underwent the Pringle maneuver. Serum alanine transaminase (ALT) and total bilirubin (TBIL) were measured, and hematoxylin and eosin (HE) staining of the liver tissue was performed. GC-MS was used to detect urinary metabolomics. Results. Compared with the sham group, the serum ALT and TBIL levels at day 1 were significantly elevated (P < 0.01) and then decreased and reached close to normal levels at day 5. GC-MS detected 7 metabolites which had similar changes as those of liver tissue revealed by histological examination. Significant differences in lactic acid, pyruvic acid, alanine, serine, and glycerol-3-phosphate were found among the groups (P < 0.001). Principle component analysis showed that 7 metabolites distinguished the day 1 and day 3 groups from the sham group. Conclusions. Noninvasive urinary metabolomic analysis is a potential means for the early detection and diagnosis of hepatic I/R injury. PMID:24191128

Chen, Liyan; Luo, Zhenchao; Fu, Wenguang; Liao, Xinxin; Cui, Zhonglin



HST/COS detection of a Ne VIII absorber towards PG 1407+265: an unambiguous tracer of collisionally ionized hot gas?  

NASA Astrophysics Data System (ADS)

We report the detection of Ne VIII in a zabs = 0.599 61 absorber towards the QSO PG1407+265 (zem= 0.94). Besides Ne VIII, absorption from H I Lyman series lines (H I ?1025-?915), several other low (C II, N II, O II and S II), intermediate (C III, N III, N IV, O III, S IV and S V) and high (S VI, O VI and Ne VIII) ionization metal lines are detected. Disparity in the absorption line kinematics between different ions implies that the absorbing gas comprises of multiple ionization phases. The low and the intermediate ions (except S V) trace a compact (˜410 pc), metal-rich (Z ˜ Z?) and overdense (log nH ˜ -2.6) photoionized region that sustained star formation for a prolonged period. The high ions, Ne VIII and O VI, can be explained as arising in a low density (-5.3 ? log nH ? -5.0), metal-rich (Z ? Z?) and diffuse (˜180 kpc) photoionized gas. The S V, S VI and C IV [detected in the Faint Object Spectrograph (FOS) spectrum] require an intermediate photoionization phase with -4.2 < log nH < -3.5. Alternatively, a pure collisional ionization model, as used to explain the previous known Ne VIII absorbers, with 5.65 < log T < 5.72, can reproduce the S VI, O VI and Ne VIII column densities simultaneously in a single phase. However, even such models require an intermediate phase to reproduce any observable S V and/or C IV. Therefore, we conclude that when multiple phases are present, the presence of Ne VIII is not necessarily an unambiguous indication of collisionally ionized hot gas.

Hussain, T.; Muzahid, S.; Narayanan, A.; Srianand, R.; Wakker, B. P.; Charlton, J. C.; Pathak, A.



222Rn detection at the microBq/m3 range in nitrogen gas and a new Rn purification technique for liquid nitrogen  


For the Borexino solar neutrino experiment a concentration line for 222Rn from a large volume of nitrogen gas has been constructed. It is based on cryo-adsorption in a charcoal trap of very low intrinsic 226Ra contamination. Consequently, the blank for activity from the daughter nuclide 222Rn is very low. 222Rn is recorded with proportional counters. This allows the detection of Rn at concentrations below the microBq/m3 level in gaseous nitrogen. The removal of radon from liquid nitrogen is achieved by direct adsorption in the liquid phase. 222Rn-measurements on evaporated nitrogen with and without previous purification are reported. PMID:10724427

Heusser; Rau; Freudiger; Laubenstein; Balata; Kirsten



Identification and confirmation of traces of chlorinated fatty acids in fish downstream of bleached kraft pulp mills by gas chromatography with halogen-specific detection.  


Methyl esters of threo-9,10-dichlorooctadecanoic, threo-7,8-dichlorohexadecanoic, and threo-5,6-dichlorotetradecanoic acids, present in transesterified extracts of filets, gonad, intestinal fat and carcass of white sucker (Catostomus commersoni) sampled in receiving waters of bleached kraft pulp mill effluents, were identified by gas chromatography with halogen-specific detection (XSD). Identification was based on (1) a comparison of the retention times of a sample peak with a prospective reference standard on two stationary phases of very different polarities by spiking, and (2) elution behavior of configurational and positional isomers of dichloro fatty acid methyl esters. PMID:12779225

Zhuang, Wenshan; McKague, Bruce; Reeve, Douglas; Carey, John



Autoionization-detected infrared spectroscopy of jet-cooled aromatic cations in the gas phase: CH stretching vibrations of isolated p-ethylphenol cations  

NASA Astrophysics Data System (ADS)

The first observation of CH stretching vibrations of isolated aromatic molecular cations in the gas phase was performed by using autoionization-detected infrared (ADIR) spectroscopy. Aromatic and alkyl CH stretching vibrations of p-ethylphenol ( p-EP) in the cationic ground state were observed and compared with those of the neutral ground state. Distinct high-frequency shifts of these vibrations upon ionization were found. CH stretching vibrations of the p-EP-Ar cluster cation were also measured by infrared photodissociation (IRPD) spectroscopy, providing essentially the same vibrational spectrum as that of the bare cation.

Fujii, Asuka; Fujimaki, Eiji; Ebata, Takayuki; Mikami, Naohiko



High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection  

NASA Astrophysics Data System (ADS)

We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303 cm-1 (˜24% of the center wavelength) at 8 ?m, with a maximum optical output power of 200 mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10-8 cm-1 Hz-1/2 was obtained.

Centeno, R.; Marchenko, D.; Mandon, J.; Cristescu, S. M.; Wulterkens, G.; Harren, F. J. M.



Determination of organotin compounds by headspace solid-phase microextraction–gas chromatography–pulsed flame-photometric detection (HS-SPME–GC–PFPD)  

Microsoft Academic Search

A method based on Headspace solid-phase microextraction (HS-SPME, with a 100 ?m PDMS-fiber) in combination with gas-chromatography\\u000a and pulsed flame-photometric detection (GC-PFPD) has been investigated for simultaneous determination of eight organotin compounds.\\u000a Monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), and the semi-volatile diphenyltin (DPhT), triphenyltin\\u000a (TPhT), monooctyltin (MOcT), and dioctyltin (DOcT) were determined after derivatization with sodium tetraethylborate. The\\u000a conditions

Manuel Bravo; Gaëtane Lespes; Ida De Gregori; Hugo Pinochet; Martine Potin Gautier



The estimation of 3,4-dihydroxyphenylacetic acid, homovanillic acid and homo-isovanillic acid in nervous tissue by gas-liquid chromatography and electron capture detection.  

PubMed Central

1 A gas chromatographic method using electron capture detection is described for the estimation of three acidic metabolites of dopamine, 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid, HVA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-hydroxy-4-methoxyphenylacetic acid (homo-isovanillic acid, iso-HVA). The method is based on the formation of the trifluoroacetyl-hexafluoroisopropyl derivatives of the three acids. 2 The method has been applied to the estimation of DOPAC, HVA and iso-HVA in tissues from the central and peripheral nervous systems. PMID:164966

Pearson, J D; Sharman, D F



A multiresidue method for 20 pesticides in Radix paeoniae Alba of Chinese herb by gas chromatography with electron-capture detection.  


A rapid multiresidue method was developed for the determination of 20 pesticides in Radix paeoniae Alba of Chinese herb by ultrasonic wave extraction, silica gel column chromatography and gas chromatography (GC) with electron-capture detection (ECD) in this study, Mean recoveries of the method ranged from 74.45 to 115.14%. The validation of the proposed approach was verified on Isatis indigotica Fort, Pltycodon grandiflorum, Cotex mouta and Poria cocos of Chinese herbs; good recoveries were also obtained in the range of 72.51-113.47%, respectively. PMID:20431860

Qian, Gao; Rimao, Hua; Feng, Tang; Xiangwei, Wu; Xuede, Li; Haiqun, Cao; Yanhong, Shi; Jun, Tang



[Detection of bacterial molecular markers in the tissue of cardiac valves in normal and pathological states by gas chromatography and mass spectrometry].  


Samples from cardiac valves of 31 patients were analyzed by gas chromatography and mass spectrometry. The algorithm of mass spectrometric parameters was developed, which permitted the determination of about 200 known microbial fatty acids, aldehydes and sterols, sufficient for the detection and quantitative determination of more that 170 taxons of clinically significant microorganisms on the genus or species levels. The quantitative and qualitative differences in the composition of microbial markers of endocardial valves in normal and pathological states, particularly in cases of infectious endocarditis, were detected. The participation of 37 microbial taxons in the process was confirmed. The level of endocardium colonization in infectious endocarditis reached from 2 to 7 x 10(9) microbial cells/g of v