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1

[Analysis of benzodiazepine derivative mixture by gas-liquid chromatography].  

PubMed

The analysis of mixture of benzodiazepine derivates (chlordiazepoxide, flunitrazepam, medazepam, nitrazepam, oxazepam and tetrazepam) by gas--liquid chromatography (GLC) in purpose to separate and identify these psychotropic drugs in mixture is presented in this article. The experiment was carried out in vitro, accommodating this method for identification and separation of drugs, isolated from biological objects (blood and urine). Referring to data of annual reports of chemical investigations (1) above-mentioned psychotropic drugs are very frequent among drug intoxication. In most cases they are detected in the mixture of the same or different pharmacological group, and this causes difficulty for separation and identification. The analysis of the mixture was carried out by GLC, which is widely used in practice of forensic-chemical examination. Adsorbents and stationery phases were changed; the conditions and parameters of chromatography were modified, in purpose totally separate preparations in the mixture. For the separation and identification of all three preparation the column packed with Inerton Super with stationary phase 3% OV-17 is suitable. The column temperature-290 degrees C. The mixture of these drugs was excreted from body fluids (blood and urine) in vitro and investigated by GLC under these conditions. The results of investigation were similar. PMID:12474705

Zevzikovas, Andrejus; Kiliuviene, Guoda; Ivanauskas, Liudas; Dirse, Vidmantas

2002-01-01

2

Analysis of serum bile acids by capillary gas--liquid chromatography--mass spectrometry.  

PubMed

A method for quantitative analysis of serum bile acids by capillary gas--liquid chromatography--mass spectrometry is described. The main features of this method are a Grob-type barium carbonate/polyethyleneglycol 20,000 glass capillary column, an all-glass capillary interface, use of the lipophilic anion exchanger DEAP-Sephadex-LH-20 for purification of the serum extract, and chenodeoxycholic-11,12-d2 acid as internal standard. Linearity of the response (ratio of intensities of the fragment ions diagnostic for the bile acid to be measured and for the internal standard) was demonstrated for four different bile acids. The method is sufficiently sensitive for measurement of bile acids in serum of healthy humans. PMID:7381330

Karlaganis, G; Schwarzenbach, R P; Paumgartner, G

1980-03-01

3

Computerised gas-liquid chromatography of bacterial cellular fatty acids in analysis of bacterial mixtures  

Microsoft Academic Search

Gas-liquid chromatography (GLC) of bacterial cellular fatty acids (CFA) was tested as a method to obtain species-specific information directly from multimicrobial samples. The CFA spectra of 145 mixtures containing 3, 4, 6 or 8 microbial species were produced by GLC. The idea of direct GLC of multibacterial samples is based on the assumption that the CFA composition of a sample

Leena Lehtonen; Reijo Peltonen; Erkki Eerola

1996-01-01

4

Quantitative fatty acid analysis of vegetable oils by gas-liquid chromatography  

Microsoft Academic Search

Summary  The fatty acid composition of a number of vegetable oils and of two synthetic mixtures of methyl esters are compared by gas-liquid\\u000a chromatography and by standard methods. The calculated iodine values from G.L.P.C. results are in good agreement with measured\\u000a iodine values and are indicative of the reliability of the G.L.P.C. values. Standard methods gave lower values for linoleic\\u000a acid

B. M. Craig; N. L. Murty

1959-01-01

5

Profile Analysis of Total Mycolic Acids from Skin Corynebacteria and from Named Corynebacterium Strains by Gas-Liquid Chromatography and Gas-Liquid  

Microsoft Academic Search

Gas-liquid chromatography (g.1.c.) was investigated as a potential tool in the classification and identification of Corynebacterium strains isolated from human skin, on the basis of the g.1.c. profile of the trimethylsilyl derivatives of their mycolic acid methyl esters. The g.1.c. patterns of five skin corynebacteria were compared with those of reference strains Coryne- bacterium diphtheriae PW8 and Corynebacteriurn xerosis NCTC

1980-01-01

6

Gas-liquid chromatography of glycerides  

Microsoft Academic Search

Available techniques are reviewed for gas-liquid chromatography of mono-, di- and triglycerides and their chemical modification\\u000a products. Major emphasis is placed upon optimum separation and quantitative estimation of the recorded peaks. Nonlinear rates\\u000a of temp programming are shown to be superior to linear rates for maximum resolution of complex glyceride mixtures. The use\\u000a of short columns improves the recoveries of

Arnis Kuksis

1965-01-01

7

Analysis of high-molecular alkyl phenols by liquid and gas-liquid chromatography and nuclear magnetic resonance  

Microsoft Academic Search

Conclusions 1Using liquid-adsorption chromatography on silica gel under selected optimum conditions, the authors separated the > 150°C (1 mm Hg) wide-cut alkyl phenol fraction into a paraffinic-olefinic part, dialkyl, ortho-alkyl, and para-alkyl phenols.It was found that a single liquid-adsorption separation gives only concentrates of these alkyl phenols. Sharper separation is obtainable by repeated chromatography.2The authors propose optimum conditions for gas-liquid

V. A. Zakupra; V. S. Dobrov; L. Ya. Grona; A. P. Lizogub

1970-01-01

8

Analysis of cis - and trans -fatty acid isomers in hydrogenated and refined vegetable oils by capillary gas-liquid chromatography  

Microsoft Academic Search

For quantitation ofcis- andtrans-fatty acid isomers, infrared (IR) spectroscopy, gas-liquid chromatography (GLC) on highly polar stationary phases or the\\u000a combination (GLC-IR) may be used. IR offers the advantage of simplicity and speed, but the lower determination limit of 5%\\u000a and the lack of detailed information limit its use. Detailed fatty acid information, required for, e.g., food-labeling purposes,\\u000a can only be

G. S. M. J. E. Duchateau; H. J. van Oosten; M. A. Vasconcellos

1996-01-01

9

Analysis of alpha-linolenic acid geometrical isomers in deodorized oils by capillary gas-liquid chromatography on cyanoalkyl polysiloxane stationary phases: A note of caution  

Microsoft Academic Search

Analysis of alpha-linolenic acid geometrical isomers in deodorized or heated oils by capillary gas-liquid chromatography (GLC)\\u000a on polar cyanoalkyl polysiloxane stationary phases requires some care to avoid interferences with other fatty acids. Depending\\u000a on the temperature of the column, thecis-11 20?1 acid may elute before, with or after thecis-9,cis-12,cis-15 18?3 acid during GLC. In some instances [temperature higher than 180C

Robert L. Wolff

1994-01-01

10

21 CFR 862.2250 - Gas liquid chromatography system for clinical use.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Gas liquid chromatography system for clinical use. ...§ 862.2250 Gas liquid chromatography system for clinical use. ...Identification. A gas liquid chromatography system for clinical...

2009-04-01

11

21 CFR 862.2250 - Gas liquid chromatography system for clinical use.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Gas liquid chromatography system for clinical use. ...§ 862.2250 Gas liquid chromatography system for clinical use. ...Identification. A gas liquid chromatography system for clinical...

2010-04-01

12

21 CFR 862.2250 - Gas liquid chromatography system for clinical use.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Gas liquid chromatography system for clinical use. ...§ 862.2250 Gas liquid chromatography system for clinical use. ...Identification. A gas liquid chromatography system for clinical...

2013-04-01

13

Analysis of Fecal Bile Acids and Neutral Steroids Using Gas-Liquid Chromatography  

Microsoft Academic Search

In the present pilot study, for investigating the physiological effects of different types of nondigestible oligosaccharides, we have validated the application of methodologies for the analysis of bile acids and neutral steroids in feces of human subjects. The accuracy of the extraction and chromatographic procedures for the analyses of bile acids and neutral steroids was determined by recovery of added

T. S. Srikumar; B. Wezendonk; W. van Dokkum

1998-01-01

14

Analysis of fats and oils by gas-liquid chromatography and by ultraviolet spectrophotometry  

Microsoft Academic Search

Summary  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a Known mixtures of pure fatty acid methyl esters and a number of fats and oils as their methyl esters have been analyzed by\\u000a conventional GLC with thermal conductivity detectors.\\u000a \\u000a \\u000a \\u000a \\u000a 2. \\u000a \\u000a Percentage of fatty acid distribution determined by GLC agreed well with known percentages in model mixtures and with analysis\\u000a by the spectrophotometric method for fats and oils.\\u000a \\u000a \\u000a \\u000a \\u000a 3. 

S. F. Herb; Paul Magidman; R. W. Riemenschneider

1960-01-01

15

Extraction and liquid-solid chromatography cleanup procedures for the direct analysis of four pyrethroid insecticides in crops by gas--liquid chromatography.  

PubMed

The extraction of four pyrethroid insecticides, fenpropanate (WL 41706, S-3206), permethrin (WL 43479, FMC-33297, PP 557, NRDC-143), cypermethrin (WL 43467, NRDC 149), and fenvalerate (WL 43775, S-5602) from carrots, tomatoes celery, and onions with acetone followed by extraction of the resulting acetone--water mixture with hexane, was investigated and found suitable for residue analysis. The elution of the four materials from two types of silica and alumina absorbents with mixtures of organic solvents of varying polarity was examined. The elution patterns and recoveries from silica gel, aluminum oxide, and water deactivated Florisil indicated potential utility in cleanup. Florisil was found to provide cleanup for asparagus, carrots, tomatoes, tobacco, and onions permitting analyses to less than 0.01 ppm for most of the insecticides by electron capture gas--liquid chromatography, at extract concentrations of 1 g/ml. The other adsorbents, singly or in combination, were found to provide the cleanup required for radishes and those cases involving other crops where Florisil cleanup was insufficient. PMID:748360

Chapman, R A; Harris, C R

1978-12-11

16

Evaluation of gas-liquid chromatography for the rapid diagnosis of Clostridium difficile associated disease.  

PubMed Central

Direct gas-liquid chromatography of faecal specimens with isocaproic acid as a marker was used for the rapid diagnosis of Clostridium difficile associated diarrhoeal diseases. Ninety stools were examined and results were compared with conventional culture on selective medium and cytotoxin assay in tissue culture. Using a combined analysis of isocaproic acid and butyric acid peak heights we defined three categories: positive, negative, and indeterminate. When the indeterminate group was excluded, the positive and negative predictive values of gas-liquid chromatography analysis were 86.9% and 85% respectively compared with culture and 71.4% and 95% respectively compared with cytotoxin assay.

Gianfrilli, P; Pantosti, A; Luzzi, I

1985-01-01

17

Gas chromatographic comparison of peptone yeast glucose and gas liquid chromatography growth media for anaerobic bacteria  

Microsoft Academic Search

The growth media peptone yeast extract glucose broth and gas liquid chromatography broth were compared with respect to their suitability for anaerobic bacteria, using 63 strains belonging to 12 species. After incubation for 24 and 48 h the broth cultures were subjected to viable counts and gas Chromatographic analysis of short-chain alcohols and fatty acids in head-space vapours and ether

E. Holst; L. Larsson

1987-01-01

18

Coupled assay of sphingomyelin and ceramide molecular species by gas liquid chromatography  

Microsoft Academic Search

This study reports a single-step analysis of the molecular species of endogenous ceramides and of the cer- amide moiety of sphingomyelins in biological samples, using gas liquid chromatography (GLC). Silylated sphingo- myelins were quantitatively converted to monosilylated cer- amide upon injection into GLC, whereas the free ceramides were di-silylated on the primary and secondary alcohol function, as confirmed by mass

Claude Vieu; François Tercé; Françoise Chevy; Corinne Rolland; Ronald Barbaras; Hugues Chap; Claude Wolf; Bertrand Perret; Xavier Collet

19

Gas-liquid chromatography of fecal neutral steriods.  

PubMed

A method is described for the analysis of fecal neutral steriods with a dual-column gas-liquid chromatography (GLC) system. After saponification of the fecal slurry, the neutral steroids were extracted with hexane. The GLC separation of the compounds and quantitation were achieved by simultaneous injection of the derivatized and derivatized aliquots of the extract onto dual colmuns under identical conditions. The neutral steroids of interest were than identified by matching the retention times with those of known standards, and identification was confirmed by use of an interfaced GLC high-resolution mass spectrometry system. The detection limit was 0.003 mg of steroid/g of fecal slurry. The pricision of the method is illustrated by a relative standard diviation of 2-10% and a recovery of neutral steroids from 73-96%. The method was applied to the determination of fecal neutral steroids in a "High protein diet in colon cancer study". A considerably larger level of coprostanone than of coprostanol was observed. Data on neutral steroids in fecal samples from subjects on different diets are the subject of a separate publication. PMID:326802

Gerhardt, K O; Gehrke, C W; Rogers, I T; Flynn, M A; Hentges, D J

1977-05-21

20

Faster identification of mycobacteria using gas liquid and thin layer chromatography  

Microsoft Academic Search

Gas liquid chromatography (GLC) and thin layer chromatography (TLC) analysis of cell wall content was used for identification of mycobacteria isolated in primary cultures. GLC permitted determination of the fatty acid and alcohol profiles ofMycobacterium simiae andMycobacterium marinum and detection of a peak inMycobacterium ulcerans formerly described forMycobacterium malmoense. Using the data obtained to fill some of the gaps in

J. J. Parez; M. Fauville-Dufaux; J. L. Dossogne; E. de Hoffmann; F. Pouthier

1994-01-01

21

Use of gas liquid chromatography/mass spectrometry for triazine herbicide residues analysis in forage and milk.  

PubMed

Residual s-triazines were isolated from forage and milk samples by methanol/chloroform extraction followed by column purification. The evaporated extracts were dissolved in acetone and analysed by gas chromatography with NPD detection and mass spectrometry. The detection limits for both methods were found to be about 5 approximately 10 ng of each s-triazine. The selective ions of the 10 s-triazines investigated (simazine, atrazine, propazine, terbuthylazine, cyanazine, desmetryne, ametryne, prometryne, terbutryne and methoprotryne) were chosen on the basis of an electron impact mass spectrometry study of the s-triazine standards and the whole mass spectra are given. Special attention was paid to the fragmentation of cyanazine and the general cleavage pathways of the s-triazines under investigation. PMID:3660950

Víden, I; Rathouská, Z; Davídek, J; Hajslová, J

1987-08-01

22

Identification of Clinical Isolates of Mycobacteria with Gas-Liquid Chromatography Alone  

PubMed Central

Identification of 18 mycobacterial species was performed by analysis of profiles obtained by using gas-liquid chromatography. Organisms were saponified in methanolic NaOH, and the reaction mixture was treated with BF3 in methanol and extracted with a hexane-chloroform mixture. An identification scheme was developed from 128 stock strains and tested against a collection of 79 clinical isolates. By using gas-liquid chromatographic profiles alone, 58% of specimens were correctly identified to species level, and an additional 41% were correctly identified to a group of two or three organisms. Use in a clinical laboratory over a 2-month period proved chromatography to be as accurate as and more rapid than concurrent biochemical testing. Of 81 isolates tested, 64% were identified to species level by chromatography alone. An additional 35% were differentiated to the same groups of two or three organisms as found in our analysis of stock strains. These groups consisted of: Mycobacterium tuberculosis, M. bovis, and M. xenopi; M. avium complex, M. gastri, and M. scrofulaceum; or M. fortuitum and M. chelonei. Identification to species level from these groups could usually be done by colonial morphology alone and could always be done by the addition of one selected biochemical test. This study demonstrated the practical application of gas-liquid chromatography in the identification of mycobacteria in a clinical laboratory. In particular, all strains of M. gordonae and M. kansasii were identified to species level. M. tuberculosis was definitively identified in 85% of cases. When it could not be definitely identified, the only alternatives were M. bovis and M. xenopi, both of which are rare causes of infection.

Tisdall, Philip A.; Roberts, Glenn D.; Anhalt, John P.

1979-01-01

23

Characterization of Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis, and Bacillus amyloliquefaciens by Pyrolysis Gas-Liquid Chromatography, Deoxyribonucleic Acid-Deoxyribonucleic Acid Hybridization, Biochemical Tests, and API Systems  

Microsoft Academic Search

Eight strains each of Bacillus subtilis, Bacillus pumilus, Bacillus lichenifor- mis, and Bacillus amyloliquefaciens were analyzed by using pyrolysis gas-liquid chromatography. Statistical analysis with canonical variates gave four well-sep- arated groups, which represented the four species. Further analysis of the same strains by deoxyribonucleic acid-deoxyribonucleic acid hybridization and API identification systems confirmed the discrimination obtained with pyrolysis gas- liquid chromatography.

A. G. O'DONNELL; J. R. NORRIS; R. C. W. BERKELEY; D. CLAUS; T. KANEK; N. A. LOGAN

24

Quantitative Estimation of Peak Areas in Gas-Liquid Chromatography  

Microsoft Academic Search

QUANTITATIVE estimation of peak areas on gas-liquid chromatograms has been carried out by a variety of methods, which include triangulation, cutting out the peak areas and weighing the cut paper, planimeter tracing and use of an integrator built into the recorder. A new method recently proposed by Bartlet and Smith1 is based on evidence that the peaks obtained with a

K. K. Carroll

1961-01-01

25

Fecal short-chain fatty acid (SCFA) analysis by capillary gas-liquid  

Microsoft Academic Search

A new method is described for short-chain fatty acid (SCFA) analysis in stool samples. After sample purification by acid vacuum transfer and concentration by alkaline freeze- drying, SCFAs were measured by gas-liquid chromatography using a capillary column. Peak resolution and reproducibility were superior to SCFA analysis on a conventional glass column. With this new technique SCFA were quantitated in stool

Wolfgang M Scheppach; Claudia E Fabian; Heinrich W Kasper

26

Non-Equilibrium Theory of Gas-Liquid Chromatography  

Microsoft Academic Search

IN a gas-liquid chromatographic column the assumption of equilibrium demands that the rate constants for solute transfer between the gas and the liquid phases must be infinitely large and the flow-rates extremely small. In practical columns neither of these conditions is ever fulfilled; the kinetic rate constants are finite, and the use of extremely slow flow-rates is out of the

M. A. Khan

1960-01-01

27

Fatty acids of cows' milk. A. Techniques employed in supplementing gas-liquid chromatography for identification of fatty acids  

Microsoft Academic Search

Milk fat methyl esters were subjected to distillation and silicic acid column chromatography to provide fractions of less\\u000a complexity for gas-liquid chromatographic analysis. It was still necessary however to employ supplemental techniques for identification.\\u000a Chromatograms were obtained with polyester columns of different polarity on all the fractions and necessary reference samples.\\u000a While many of the components were identified in the

Paul Magidman; S. F. Herb; R. A. Barford; R. W. Riemenschneider

1962-01-01

28

Determination of gas-liquid partition coefficients by automatic equilibrium headspace-gas chromatography utilizing the phase ratio variation method  

Microsoft Academic Search

The new phase ratio variation method is described which represents a convenient way for the determination of gas-liquid partition coefficients for practical purposes, utilizing equilibrium headspace-gas chromatography (EHS-GC). This method is based on the relationship between reciprocal peak area and the phase ratio in the vial containing the sample solution; it involves regression analysis of the EHS-GC measurements of a

L. S. Ettre; C. Welter; B. Kolb

1993-01-01

29

THE DIRECT DETERMINATION OF LACTIC ACID IN CANE MOLASSES BY GAS-LIQUID CHROMATOGRAPHY  

Microsoft Academic Search

A method for the direct determination of lactic acid in cane molasses by gas-liquid chromatography is described. Data has been presented to show that the method is both precise and accurate. The method overcomes the lengthy ion-exchange separation of lactic acid, currently in use. The quantification of lactic acid in molasses is important as a means of determining sugar losses

T. A. CHORN

30

Characterization of unsaturated fatty acids by gas-liquid chromatography  

Microsoft Academic Search

The equivalent chain length (ECL) has been determined on 79 methyl esters of unsaturated fatty acids and on 7 ethyl esters\\u000a by gas chromatography. Ethylene glycol succinate (EGS), diethylene glycol succinate, ?-cyclodextrin acetate and Apiezon L\\u000a were chosen as the liquid phases to be used. For methyl esters of mono- and polyenoic acids, the differences between ECL on\\u000a EGS and

H. H. Hofstetter; N. Sen; R. T. Holman

1965-01-01

31

DETERMINATION OF PENTACHLOROPHENOL IN MARINE BIOTA AND SEA WATER BY GAS-LIQUID CHROMATOGRAPHY AND HIGH-PRESSURE LIQUID CHROMATOGRAPHY  

EPA Science Inventory

A method is described for measuring pentachlorophenol (PCP) in samples from the estuarine environment. Gas-liquid chromatography (GLC) is used to determine PCP residues in tissues as low as 0.01 ppm by formation of the ethyl diazohydrocarbon derivative, followed by Florisil clean...

32

Theoretical and practical aspects of open-tubular columns in gas-liquid chromatography  

SciTech Connect

The basic concepts behind open-tubular gas-liquid chromatography columns were elucidated twenty-five years ago. A comprehensive review of the more practical aspects of fabrication of glass-capillary columns has recently been published by Lee and Wright. Column tube material has changed; various types of glass seem to be favored. Column dimensions have changed. A variety of methods have been used to render glass and fused-silica inert. Stationary phases most useful now appear to be polysiloxane gums. The sample capacity must be of microgram amounts of solute. The use of various carrier gases can have profound effects upon separations as a result of gas-phase interactions. The best method of placement of a plug of solutes onto the column remains on-column injection. There are few problems associated with detection dead volume in open-tubular gas-liquid chromatography columns. Further study and investigation include fabrication techniques pertaining to highly efficient gas-solid and gas-liquid-solid columns using phases in which the adsorbent of choice is suspended in a colloid in a suitable stationary liquid dispersant. Another problem is the use of thinner liquid films. 2 figures. (DP)

Laub, R.J.

1981-11-01

33

Lipid Patterns of Selected Microorganisms as Determined by Gas-Liquid Chromatography1  

PubMed Central

The cellular lipid patterns of seven strains of microorganisms were examined by gas-liquid chromatography in this preliminary study. The chloroform methanol-soluble lipids were extracted by the Soxhlet method from dried cultures which had been grown at 25 ± 2 C for 18 hr with mechanical shaking. The cellular extract was methylated by use of a low temperature sulfuric acid method, and the resulting methyl esters were chromatographed. Considerable differences in the lipid patterns among the seven microorganisms tested indicated that this method might be useful for the identification of closely related microbial genera, and possibly for species differentiation.

Steinhauer, John E.; Flentge, Robert L.; Lechowich, Richard V.

1967-01-01

34

Arabidopsis thaliana Polar Glycerolipid Profiling by Thin Layer Chromatography (TLC) Coupled with Gas-Liquid Chromatography (GLC)  

PubMed Central

Biological membranes separate cells from the environment. From a single cell to multicellular plants and animals, glycerolipids, such as phosphatidylcholine or phosphatidylethanolamine, form bilayer membranes which act as both boundaries and interfaces for chemical exchange between cells and their surroundings. Unlike animals, plant cells have a special organelle for photosynthesis, the chloroplast. The intricate membrane system of the chloroplast contains unique glycerolipids, namely glycolipids lacking phosphorus: monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG)4. The roles of these lipids are beyond simply structural. These glycolipids and other glycerolipids were found in the crystal structures of photosystem I and II indicating the involvement of glycerolipids in photosynthesis8,11. During phosphate starvation, DGDG is transferred to extraplastidic membranes to compensate the loss of phospholipids9,12. Much of our knowledge of the biosynthesis and function of these lipids has been derived from a combination of genetic and biochemical studies with Arabidopsis thaliana14. During these studies, a simple procedure for the analysis of polar lipids has been essential for the screening and analysis of lipid mutants and will be outlined in detail. A leaf lipid extract is first separated by thin layer chromatography (TLC) and glycerolipids are stained reversibly with iodine vapor. The individual lipids are scraped from the TLC plate and converted to fatty acyl methylesters (FAMEs), which are analyzed by gas-liquid chromatography coupled with flame ionization detection (FID-GLC) (Figure 1). This method has been proven to be a reliable tool for mutant screening. For example, the tgd1,2,3,4 endoplasmic reticulum-to-plastid lipid trafficking mutants were discovered based on the accumulation of an abnormal galactoglycerolipid: trigalactosyldiacylglycerol (TGDG) and a decrease in the relative amount of 18:3 (carbons : double bonds) fatty acyl groups in membrane lipids 3,13,18,20. This method is also applicable for determining enzymatic activities of proteins using lipids as substrate6.

Wang, Zhen; Benning, Christoph

2011-01-01

35

Separation of conjugated methyl octadecadienoate and trienoate geometric isomers by silver-resin column and preparative gas-liquid chromatography  

Microsoft Academic Search

Silver-resin column chromatography, preceded by preparative gas-liquid chromatography to remove unconjugated esters, has been\\u000a used to separate conjugated methyl octadecadienoates intocis,cis-, cis,trans-, andtrans,trans- isomers, also methyl eleostearate into a- and ?-isomers in 91 to 100% purity.

E. A. Emken; C. R. Scholfield; V. L. Davison; E. N. Frankel

1967-01-01

36

Detection of Clostridium difficile in faeces by direct gas liquid chromatography.  

PubMed Central

Stool specimens examined for the presence of Clostridium difficile and its cytotoxin were screened by gas liquid chromatography for the presence of volatile fatty acids and p-cresol. Twenty seven of 110 (25%) stools yielded C difficile or cytotoxin; iso-valeric acid was detected in 63/110 (57%) and iso-caproic acid in 18/110 (16%) stools. Para-cresol was found in 24/71 (34%) stools examined. Iso-valeric acid was detected in 85% of stools positive for C difficile, whereas iso-caproic acid (41%) and p-cresol (52%) were found in much lower numbers of C difficile-positive stools. It is concluded that gas chromatographic detection of volatile fatty acids or p-cresol in faeces are not satisfactory screening tests for the presence of C difficile.

Levett, P N

1984-01-01

37

Gas-Liquid Chromatography of Terpenes. Part XI. The Volatile Oil of the Leaves of Juniperus Scopulorum Sarg.  

National Technical Information Service (NTIS)

The neutral leaf oil of Rocky Mountain juniper was analyzed by gas-liquid chromatography. d-Sabinene was found to be the major constituent (45.7%) and smaller amounts of d-limonene (11.4%), d-alpha-pinene (4.2%), gama-terpinene (1.15%), p-cymene (1.4%), l...

E. Von Rudlof F. M. Couchman

1964-01-01

38

Oxidized plant sterols in human serum and lipid infusions as measured by combined gas-liquid chromatography-mass spectrometry  

Microsoft Academic Search

Some oxidized forms of cholesterol (oxysterols) are thought to be atherogenic and cytotoxic. Because plant sterols are structurally related to cholesterol, we examined whether oxidized plant sterols (oxyphytosterols) could be identified in human serum and soy-based lipid emulsions. We first prepared both deuterated and nondeuterated reference compounds. We then analyzed by gas-liquid chromatography- mass spectrometry the oxyphytosterol concentrations in serum

Jogchum Plat; Harald Brzezinka; Dieter Lütjohann; Ronald P. Mensink; Klaus von Bergmann

39

Adsorption and Solution of Weakly Polar Vapors with Thin Layers of Water as Studied by Gas-Liquid Chromatography.  

National Technical Information Service (NTIS)

The paper continues a study on the adsorption and solution of weakly polar vapors with thin layers of water by means of gas-liquid chromatography. In particular 7 new solutes were examined: CH2Cl2, CHCl3, CCl4, cis and trans-2-octene, isopropyl ether, and...

B. L. Karger

1971-01-01

40

Estimation of chlorpyriphos and cypermethrin residues in chilli (Capsicum annuum L.) by gas-liquid chromatography.  

PubMed

Dissipation of chlorpyriphos and cypermethrin in chilli was studied following three applications of a combination formulation of Nurelle-D 505 (chlorpyriphos 50%?+?cypermethrin 5%) at 1 and 2 L?ha(-1) at an interval of 15 days. Residues of chlorpyriphos and cypermethrin in chilli were estimated by gas-liquid chromatography and confirmed by gas chromatography-mass spectrometry. Half-life periods for chlorpyriphos were found to be 4.43 and 2.01 days, whereas for cypermethrin these values were observed to be 2.51 and 2.64 days at single and double the application rates, respectively. Residues of chlorpyriphos dissipated to more than 80% after 10 days at both the dosages. However, residues of cypermethrin dissipated to the extent of more than 70% in 7 days. Soil samples collected after 15 days of the last application did not show the presence of chlorpyriphos and cypermethrin at their respective determination limit of 0.01 mg?kg(-1). The use of chlorpyriphos and cypermethrin mixture at the recommended dosage does not seem to pose any hazards to the consumers, and a waiting period of 1 day is suggested to reduce the risk before consumption of green chilli. PMID:23114920

Jyot, Gagan; Mandal, Kousik; Battu, R S; Singh, Balwinder

2012-11-01

41

Identification of Neisseria by electron capture gas-liquid chromatography of metabolites in a chemically defined growth medium.  

PubMed Central

A dual-purpose study was carried out in an attempt to develop a rapid, sensitive method to identify Neisseria species by gas chromatography and to learn more about the metabolism of these organisms. Sixty-nine isolates of Neisseria were grown in a chemically defined fluid medium; the spent medium was extracted sequentially at pH 2 with diethyl ether and at pH 10 with chloroform. The pH 10 extracts were derivatized with heptafluorobutyric anhydride and analyzed by electron capture gas-liquid chromatography. The resulting spent culture medium electron capture gas-liquid chromatography profiles showed several qualitative and significant quantitative differences among the Neisseria species potentially useful in separating and identifying these organisms. Putrescine and cadaverine which were present in the spent culture medium of some Neisseria, including N. gonorrhoeae, were tentatively identified. Substituting carbohydrates for the chemically defined medium containing glucose in the base medium produced altered profiles with increased quantitative and qualitative differences.

Morse, C D; Brooks, J B; Kellogg, D S

1977-01-01

42

Determination of trans octadecenoic acids by silver-ion chromatography-gas liquid chromatography: an intercomparison of methods.  

PubMed

Several silver-ion chromatography-gas liquid chromatography (GLC) techniques for the determination of trans octadecenoic acids in partially hydrogenated vegetable fats were collaboratively evaluated. Twelve laboratories participated in the study. All collaborators used high polarity fused silica capillary columns for the separation of fatty acid methyl esters by GLC; 7 collaborators isolated trans monoenes by silver-ion liquid chromatography (Ag-LC) and the remainder used silver-ion thin-layer chromatography (Ag-TLC). Eight artificially prepared materials [soybean oil spiked with either methyl elaidate, trielaidin, or trans octadecenoates isolated from partially hydrogenated sunflower oil (PHSO)] and 2 matrix materials (PHSO and a blend of PHSO and palm oil) served as test samples. Ag-TLC and Ag-LC proved to be equivalent techniques for the prefractionation of trans monoenes. Recovery of methyl elaidate, trielaidin, or trans octadecenoates isolated from PHSO varied between 97.9-103.7% over a concentration range of 1 to 30 g trans fatty acids/100 g. Reproducibility relative standard deviation (RSDR) for the spiked samples were in the range of 3.1-8.6% for 30-1% trans monoene content. For the 2 matrix samples (mean 3.75 and 19.08% trans monoene content) RSDR was 13.2 and 3.6%. The hyphenated techniques tested proved to be highly accurate and sufficiently precise methods for the determination of trans monoenes in partially hydrogenated vegetable fats. Procedural variations of the silver-ion chromatography prefractionation step (separation mode, mobile phase, and detection systems) did not significantly influence the results of the test. Therefore, silver-ion chromatography is a robust method, which does not need rigorous standardization to achieve high precision of test results. A further benefit of the hyphenated technique is that any type of efficient polar capillary column can be used. PMID:11601469

Buchgraber, M; Ulberth, F

43

Amino acid composition of human nail, as measured by gas-liquid chromatography.  

PubMed

We describe a quantitative method for determination of histidine and 16 other amino acids in a nail hydrolysate. This is based on the formation of trifluoroacetyl amino acid methyl esters and gas-liquid chromatographic analysis with use of two columns of mixed stationary phases. Histidine is determined as a triple derivative Nalpha-trifluroacetyl-Nim-carbethoxy methyl histidinate. The specificity and reproducibility of the method are illustrated. As little as 1 mg of amino acid per gram of nail can be determined, and 15 hydrolysates can be completely analyzed in 10 working days. Data obtained from multiple analyses of 10 nail hydrolysates by the method described closely parallel those obtained in another laboratory, in which an amino acid analyzer was used. PMID:975504

Greaves, M; Moll, J M

1976-10-01

44

Determination of organic substances with different boiling points in aqueous media by capillary gas-liquid chromatography  

Microsoft Academic Search

Studies were conducted on separation of organic substances with different boiling points and polarity when simultaneously\\u000a present in water by capillary gas-liquid chromatography on a Kristall 2000 m chromatograph. The effect of the column phase\\u000a and temperature conditions on the separation factor and component exit time was investigated. Column temperature programming\\u000a was used to reduce the component, especially heavy component,

E. A. Rogova; O. A. Roshchina; T. I. Samsonova; A. V. Genis

2009-01-01

45

Photochemical technique for the elimination of chlorinated aromatic interferences in the gas-liquid chromatographic analysis for chlorinated paraffins.  

PubMed

A method is described for eliminating chlorinated aromatic interferences in the analysis for the more volatile chlorinated paraffins. Sample extracts are irradiated in aliphatic hydrocarbon solvents with high intensity ultraviolet light prior to detection of the chlorinated paraffin by microcoulometric gas-liquid chromatography. Chlorinated aromatic and unsaturated materials, including DDT and polychlorinated biphenyls, are selectively degraded to compounds containing little or no chlorine. Cycloaliphatic pesticides such as toxaphene, chlordane, and mirex are only partially degraded. Analysis of fish fillets fortified with 1 and 5 ppm of a chlorinated paraffin gave recoveries greater than 90%. PMID:807552

Freidman, D; Lombardo, P

1975-07-01

46

THE ANALYSIS OF SOME VOLATILE PHOSPHORUS COMPOUNDS BY GAS-LIQUID CHROMATOGRAPHY. Includes Papers: GAS CHROMATOGRAPHIC ANALYSIS OF SOME VOLATILE PHOSPHORUS COMPOUNDS. REACTIONS OF TRITIUM ATOMS WITH FROZEN HYDROCARBONS  

Microsoft Academic Search

In the first paper, a gas chromatographic method for the analysis of ; mixtures of (CHâO)âPOH - (CâHâO)âPOH, PC1â ; PSC1\\/sub 3, and PC13\\/ - POC1â was developed. Pyrex glass was used as the ; column and body of the thermal conductivity cell, and tantalum wire was employed ; for the sensing elements. In the second paper, tritium atoms generated

S. H. Shipotofsky; H. C. Moser; R. D. Shores

1960-01-01

47

Gas-liquid chromatography for evaluating polysaccharide degradation by Ruminococcus flavefaciens C94 and Bacteroides succinogenes S85.  

PubMed Central

Two predominant rumen cellulolytic bacteria, Ruminococcus flavefaciens C94 and Bacteroides succinogenes S85, were incubated with ground filter paper (Whatman no. 1), cattle manure fiber, wheat straw, Kentucky bluegrass, alfalfa, and corn silage as substrates. Analyses of the initial substrate and the recovered residue after 48 h of static incubation showed that R. flavefaciens C94 was quantitatively more effective than B. succinogenes S85 in degrading total dry matter (32.3% versus 16.1%). However, B. succinogenes S85 demonstrated a qualitative advantage in degrading the hemicellulose and hemicellulosic sugars of particular substrates. R. flavefaciens degraded a mean 29.7% of the cellulose and 35.6% of the hemicellulose in the various substrates, whereas B. succinogenes degraded a mean 17.9 and 31.6% of these fractions, respectively. Gas-liquid chromatography was an important aid in characterizing the polysaccharide-degrading capabilities of these rumen species.

Collings, G F; Yokoyama, M T

1980-01-01

48

Gas-liquid chromatographic analysis of the monosaccharide composition of acid glycosaminoglycans (mucopolysaccharides) derived from animal tissues.  

PubMed

Quantitative, gas-liquid chromatography was investigated for analysis of the monosaccharide composition of acid mucopolysaccharides from animal tissues. The method entailed the analysis of the trimethylsillyl (Me3Si) derivatives of methyl glycosides on two liquid phases. Good resolution of monosaccharides was achieved by use of columns of SE-30 and Apiezon-M. The procedure was tested with chondroitin 4-sulfate, and the results were slightly different from those of Mathews et al. When the analysis is performed according to this method, important points are: (1) absolutely anhydrous, methanolic hydrogen chloride is necessary, to ensure detection of hexosamines and sialic acid; and (2) high moisture in the air obstructs high recovery of methyl glycosides and their Me3Si derivatives, except in the case of neutral sugars. PMID:603870

Yokota, M; Mori, T

1977-12-01

49

Simultaneous determination of neopynamine and piperonyl butoxide by capillary column gas-liquid chromatography.  

PubMed

A method is developed for the simultaneous determination of neopynamine and piperonyl butoxide by chromatography on a quartz capillary column using flame ionization detection. Benzyl mandelate is used as an internal standard. Calibration graphs are linear down to at least 3.75 mg% and 3 mg% for neopynamine and piperonyl butoxide, respectively. PMID:6725494

Richard, A; Andermann, G

1984-05-01

50

Gas-liquid chromatographic analysis of synovial fluid: volatile short-chain fatty acids in septic arthritis  

Microsoft Academic Search

Volatile short-chain fatty acids (SCFA) in synovial fluid from 80 patients were quantified by gas-liquid chromatography (GLC). Characteristic patterns of volatile SCFA could not be associated with septic, nonseptic inflammatory, or noninflammatory groups. Mean concentrations of pentanoic and hexanoic acids were similar in all groups studied. In the septic arthritis group 3 of 4 patients with acetic acid and of

D G Borenstein; C A Gibbs; R P Jacobs

1983-01-01

51

Use of gas-liquid chromatography as a screening test for toxigenic Clostridium difficile in diarrhoeal stools.  

PubMed Central

In order to determine if gas-liquid chromatography (GLC) on concentrated stool extracts could be substituted to cell culture assay for cytotoxicity, we prospectively studied 154 diarrhoeal stools submitted for detection of Clostridium difficile toxin. Isocaproic-positive samples were cultured on egg yolk agar supplemented with cycloserine, cefoxitin and fructose for isolation of C difficile, and on egg yolk agar plus kanamycin for isolation of other clostridium species. Of the 154 samples, 129 were GLC-negative (height of the isocaproic peak less than 1.2 cm) and were toxin-negative. Twenty-five stools yielded isocaproic acid; C difficile isolated from 13 of them, six of which were also toxin-positive. Four other isocaproic-positive samples yielded C bifermentans and C sordellii; all were toxin-negative. These results indicate that a negative GLC is an excellent screening test for excluding C difficile infection; positive results must be checked by toxin testing and culture since they are not necessarily associated with the presence of C difficile or its toxin.

Pepersack, F; Labbe, M; Nonhoff, C; Schoutens, E

1983-01-01

52

Simulating Retention in Gas-Liquid Chromatography: Benzene, Toluene, and Xylene Solutes  

SciTech Connect

Accurate predictions of retention times, retention indices, and partition constants are a long sought-after goal for theoretical studies in chromatography. Although advances in computational chemistry have improved the understanding of molecular interactions, little attention has been focused on chromatography, let alone calculations of retention properties. Configurational-bias Monte Carlo simulations in the isobaric-isothermal Gibbs ensemble were used to investigate the partitioning of benzene, toluene, and the three xylene isomers between a squalane liquid phase and a helium vapor phase. The united-atom representation of the TraPPE (Transferable Potentials for Phase Equilibria) force field was used for all solutes and squalane. The Gibbs free energies of transfer and Kovats retention indices of the solutes were calculated directly from the partition constants (which were averaged over several independent simulations). While the calculated Kovats indices of benzene and toluene at T = 403 K are significantly higher than their experimental counterparts, much better agreement is found for the xylene isomers at T = 365 K.

WICK,COLLIN D.; MARTIN,MARCUS G.; SIEPMANN, J. ILJA; SCHURE,MARK R.

2000-07-12

53

Quantitative Determination of Epinephrine and Norepinephrine in the Picogram Range by Flame Ionization Gas-Liquid Chromatography.  

National Technical Information Service (NTIS)

A gas-liquid chromatographic method has been developed using the hydrogen flame detector for the determination of epinephrine and norepinephrine in blood plasma, red blood cells, serum and urine. The chromatographic method presents several advantages over...

H. G. Lovelady H. A. Schwertner L. L. Foster

1974-01-01

54

Determination of brominated vegetable oils in soft drinks by gas liquid chromatography  

Microsoft Academic Search

A method is described for the qualitative and quantitative determination of brominated vegetable oils in soft drinks. The\\u000a procedure involves treatment of the brominated oils with sodium methoxide followed by GLC analysis of the resulting methyl\\u000a esters using methyl pentadecanoate as internal standard. Recoveries on known amounts of these oils ranged between 93.7% and\\u000a 102.4%. The technique, applied to several

H. B. S. Conacher; R. K. Chadha; M. R. Sahasrabudhe

1969-01-01

55

Analysis of spatial and temporal spectra of liquid film surface in annular gas-liquid flow  

NASA Astrophysics Data System (ADS)

Wavy structure of liquid film in annular gas-liquid flow without liquid entrainment consists of fast long-living primary waves and slow short-living secondary waves. In present paper, results of spectral analysis of this wavy structure are presented. Application of high-speed LIF technique allowed us to perform such analysis in both spatial and temporal domains. Power spectra in both domains are characterized by one-humped shape with long exponential tail. Influence of gas velocity, liquid Reynolds number, liquid viscosity and pipe diameter on frequency of the waves is investigated. When gravity effect is much lesser than the shear stress, similarity of power spectra at different gas velocities is observed. Using combination of spectral analysis and identification of characteristic lines of primary waves, frequency of generation of secondary waves by primary waves is measured.

Alekseenko, Sergey; Cherdantsev, Andrey; Heinz, Oksana; Kharlamov, Sergey; Markovich, Dmitriy

2013-09-01

56

Simplified determination of serum cholesterol sulfate by gas-liquid chromatography combined with cyclohexylsilane-bonded phase column purification  

Microsoft Academic Search

A new gas-liquid chromatographic (GLC) determination of cholesterol sulfate (CS) and dehydroepiandrosterone sulfate (DHEAS) for a biochemical diagnosis of recessive X-linked ichthyosis (RXLI) is described. Although the GLC method for determination of CS is known to be more sensitive than the thin layer chromatographic (TLC) method, the former method has not been widely employed because of its complicated pre-purification steps.

S. Serizawa; T. Nagai; M. Ito; Y. Sato

1989-01-01

57

Effect of inoculum size on ampicillin and amoxycillin susceptibility determined by gas-liquid chromatography for members of the family Enterobacteriaceae.  

PubMed Central

Inoculum size had only a small effect on the results for ampicillin and amoxycillin susceptibility testing of Escherichia coli. In contrast, a difference in inoculum size from 10(6) to 10(8) CFU/ml profoundly affected the results for ampicillin and amoxycillin susceptibility testing of Proteus mirabilis, causing a change from susceptibility to complete resistance. These different effects of inoculum size were observed both when susceptibility was determined by the suppression of a characteristic metabolic product analyzed by head-space gas-liquid chromatography (HS-GLC) and when it was determined by MIC testing in broth. Inoculum size affected the results for ampicillin susceptibility of P. mirabilis determined concurrently with the rapid HS-GLC urine test, because 10(8) CFU/ml may occur in urine specimens. In the rapid test, significant numbers of Escherichia, Klebsiella, Citrobacter, Proteus, Morganella, and Providencia spp. in urine specimens are detected within 4 h by HS-GLC analysis for characteristic metabolic products in cultures. Most P. mirabilis in urine specimens appeared to be ampicillin resistant in the rapid HS-GLC test but were reported to be ampicillin susceptible in hospital laboratory agar dilution tests 2 days later. However, ampicillin susceptibility results for Escherichia, Klebsiella, and Citrobacter spp. agreed with hospital laboratory reports. It was concluded that reports of ampicillin susceptibility or resistance for the commonest cause of urinary tract infections, E. coli, within 4 h of receipt of the specimen would be clinically valuable and that a provisional report of ampicillin resistance for P. mirabilis would not lead to ineffective therapy.

Hayward, N J

1986-01-01

58

Fatty acids of cows' milk. B. Composition by gas-liquid chromatography aided by other methods of fractionation  

Microsoft Academic Search

A fresh sample of cows' milk was converted directly to the methyl esters by methanolysis and the esters were fractionated\\u000a into eleven distilled fractions and an undistilled portion. The latter, which contained the bulk of the polyunsaturated and\\u000a long chain esters, was further fractionated by adsorption chromatography on a silicic acid column. Each fraction from the\\u000a distillation and adsorption chromatography

S. F. Herb; Paul Magidman; Francis E. Luddy; R. W. Riemenschneider

1962-01-01

59

Thermal fluid dynamics analysis of gas–liquid flow on a distillation sieve tray  

Microsoft Academic Search

Conventional models for distillation columns are based on equilibrium and non-equilibrium stage concepts, and both consider the fluid dynamics in a macroscopic point of view. The main objective of this work is to apply a CFD model under Eulerian-Eulerian framework for gas–liquid flows, with capability to predict the momentum and thermal phenomena of the multiphase flows. A three-dimensional and transient

D. Noriler; H. F. Meier; A. A. C. Barros; M. R. Wolf Maciel

2008-01-01

60

Partitioning and adsorption in gas-liquid-solid chromatography: Models of temporal moments for retention and variance  

Microsoft Academic Search

The resolution of gaseous chemical species in gasliquid-solid chromatography is influenced by absorption (partitioning) in the liquid and adsorption at the liquid-solid interface. We consider fundamental mass transfer models with adsorption and partitioning effects for solid chromatographic supports covered with thin films of stationary liquid. The dynamic models, based on mass-balance partial-differential equations, include the significant phenomena: convection, axial dispersion,

B. J. McCoy

1993-01-01

61

Numerical analysis of gas-liquid mixed transport process in a multiphase rotodynamic pump  

NASA Astrophysics Data System (ADS)

One of the main challenges in developing multiphase rotodynamic pump is how to avoid gas-liquid separation in high IGVF (inlet gas volume fraction) condition. In this study, the two-fluid model was used to analyse the unsteady gas-liquid two-phase transport process with three-dimensional structure mesh. The turbulence was modelled by SST model and the drag force and added mass force were accounted for in the interfacial momentum transfer terms. The simulation was carried out in five working conditions with different flow rate but same IGVF. The results show that the region of impeller inlet can active the formation of air mass due to the abrupt change of flow passage and the rotation effect of the impeller; in the transport process, the field of gas volume fraction will fluctuate and lead to the fluctuation of the pressure field and the pump head. Also, by comparing the head performance with the experiment, the reliability of the current numerical model and methods in most working conditions is validated.

Yu, Z. Y.; Zhang, Q. Z.; Huang, R.; Cao, S. L.

2012-11-01

62

Rapid confirmation of enzyme multiplied immunoassay technique (EMIT) cocaine positive urine samples by capillary gas-liquid chromatography/nitrogen phosphorus detection (GLC/NPD).  

PubMed

A rapid gas-liquid chromatographic (GLC) method was developed for the confirmation of benzoylecgonine (BE) positive urine samples screened by the enzyme multiplied immunoassay technique (EMIT) assay. The procedure is performed by solvent extraction of BE from 0.1 or 0.2 mL of urine, followed by an aqueous wash of the solvent and evaporation. The dried residue was derivatized with 50 microL of pentafluoropropionic anhydride and 25 microL of pentafluoropropropanol at 90 degrees C for 15 min. The derivatizing reagents were evaporated to dryness, and the derivatized BE, and cocaine if present, were reconstituted and injected into the gas chromatograph. The column was a 15-m by 0.2-mm fused silica capillary column, coated with 0.25 micron of DB-1, terminating in a nitrogen phosphorus detector (NPD). Cocaine and the pentafluoro BE derivatives retention times were 3.2 and 2.6 min, respectively. Nalorphine was used as reference or internal standard with a retention time of 4.78 min. The complete procedure can be performed in approximately 1.5 h. The EMIT cutoff between positive and negative urine samples is 300 ng/mL of BE. The lower limit of sensitivity of this method is 25 ng of BE extracted from urine. Validation studies resulted in confirmation of 101 out of 121 EMIT cocaine positive urine samples that could not be confirmed by thin-layer chromatography (TLC). This represents 84% confirmation efficiency. PMID:2645381

Verebey, K; DePace, A

1989-01-01

63

Effect of cavitation on the properties of coal-tar pitch as studied by gas-liquid chromatography  

SciTech Connect

The applicability of the cavitation-wave effect to coal-tar pitch processing is considered. The results of the GLC analysis of the test material before and after rotor-pulsation cavitation treatment are given. The organic matter of coal-tar pitch was found to degrade upon cavitation; as a result of this, the yields of light and medium fractions considerably increased. 5 refs., 2 figs., 4 tabs.

M.I. Baikenov; T.B. Omarbekov; S.K. Amerkhanova (and others) [Buketov State University, Karaganda (Kazakhstan)

2008-02-15

64

Analysis of short chain fatty acids from different intestinal samples by capillary gas chromatography  

Microsoft Academic Search

Summary  A capillary gas-liquid chromatography method for the analysis of free short chain fatty acids in intestinal samples was developed. Analytical results obtained with intestinal samples are influenced not only by high molecular mass matrix constituents but also by matrix components with a molecular weight smaller than 5000 daltons. To achieve a faithful transfer of SCFA into the chromatographic system it

K. Schfifer

1995-01-01

65

Quantitative isolation and gas-liquid chromatographic analysis of total fecal bile acids  

Microsoft Academic Search

SUMMARY A method for isolation and quantification of fecal bile acids is described which allows sterol balance studies to be made in man or in small laboratory animals without re- quiring the use of radioisotopes in vivo. Bile acids are purified by column and thin-layer chromatography, converted to the trimethylsilyl ethers of their methyl esters, and quantified by GLC with

SCOTT M. GRUNDY; E. H. AHRENS; TATU A. MIETTINEN

66

In vitro oxidation of IV lipid emulsions in different all-in-one admixture bags assessed by an iodometric assay and gas-liquid chromatography  

Microsoft Academic Search

Polyunsaturated fatty acids (FAs) of intravenous (IV) lipid emulsions can peroxidize to potentially harmful lipid hydroperoxides. In order to assess in vitro peroxidation of IV fat emulsions in all-in-one (AIO) admixture bags, an iodometric titration to determine lipid hydroperoxide content expressed by the peroxide value (PV) and a gas-liquid chromatographic (GLC) assay to determine changes of the FA pattern were

Patrick J. K. Steger; Stefan F. Mühlebach

1997-01-01

67

Rapid determination of methadone and its major metabolite in biological fluids by gas–liquid chromatography with thermionic detection for maintenance treatment of opiate addicts  

Microsoft Academic Search

A rapid gas–liquid chromatographic assay is developed for the quantification of methadone (Mtd) and its major metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), in biological fluids of opiate addicts. After alkaline extraction from samples with lidocaine hydrochloride as internal standard, Mtd and EDDP are separated on SP-2250 column at 220°C and detected with a thermionic detector. The chromatographic time is about 6 min. The

Nassima Chikhi-Chorfi; Chuong Pham-Huy; Hervé Galons; Nathalie Manuel; William Lowenstein; Jean-Michel Warnet; Jean-Roger Claude

1998-01-01

68

Modal Wavelets Analysis to Gas-Liquid Two Phase Flow PIV Images  

SciTech Connect

A modal wavelet transform, which overcomes the intrinsic data number limitation of power of two to conventional wavelet transform, has been applied to analysis of pseudo and real bubbly flow PIV images. The modal wavelet transform is compared with the discrete wavelet transform in order to select the best base function among Neumann, Dirichlet and Green function types base functions. Consequently, it is verified that Neumann type base function is the best because the correlation of Neumann type base function is the highest. From the result of wavelet analysis of the real bubbly flow PIV image, as the relative velocity is higher, the dominant eddy scale becomes smaller. The extraction modal wavelet level depends on the base function. (authors)

Masahiro Takei [Nihon University, 1866 Kameino, Fujisawa-Shi, Kanagawa 252-8510 (Japan); Hassan, Yassin A. [Texas A and M University, College Station, Texas 77843 (United States); Ortiz-Villafuerte, J. [National Institute for Nuclear Research, Carretera Mexico Toluca Km.36.5, 52045 Municipio de Ocoyoacac, Salazar. Edo. de Mexico, C.P.52046 Mexico (Mexico); Tomomasa Uemura [Kansai University, Suita-shi, Osaka 564 (Japan)

2006-07-01

69

Compact gas liquid separator  

Microsoft Academic Search

Compact gas-liquid separator comprising a cylindrical separation chamber including an inlet head and a degasifying vessel. The inlet head comprises an inlet tube supporting a nozzle positioned adjacent to the inner wall of a cover situated within the axis of the separation chamber. The cover includes a cylindrical portion closed by a convex cap and extends toward the bottom by

J. Y. J. Deysson; A. P. L. Potiron

1984-01-01

70

Boolean logic analysis for flow regime recognition of gas-liquid horizontal flow  

NASA Astrophysics Data System (ADS)

In order to develop a flowmeter for the accurate measurement of multiphase flows, it is of the utmost importance to correctly identify the flow regime present to enable the selection of the optimal method for metering. In this study, the horizontal flow of air and water in a pipeline was studied under a multitude of conditions using electrical resistance tomography but the flow regimes that are presented in this paper have been limited to plug and bubble air-water flows. This study proposes a novel method for recognition of the prevalent flow regime using only a fraction of the data, thus rendering the analysis more efficient. By considering the average conductivity of five zones along the central axis of the tomogram, key features can be identified, thus enabling the recognition of the prevalent flow regime. Boolean logic and frequency spectrum analysis has been applied for flow regime recognition. Visualization of the flow using the reconstructed images provides a qualitative comparison between different flow regimes. Application of the Boolean logic scheme enables a quantitative comparison of the flow patterns, thus reducing the subjectivity in the identification of the prevalent flow regime.

Ramskill, Nicholas P.; Wang, Mi

2011-10-01

71

Analysis of metabolic profiles of bile acids in urine using a lipophilic anion exchanger and computerized gas-liquid chromatorgaphy-mass spectrometry.  

PubMed

A method is described for quantitative analysis of bile acids in urine. Urine is acidified and bile acids are extracted on an Amberlite XAD-2 column. Bile salts are converted to acids on an Amberlyst A-15 column and are separated into groups of unconjugated, glycine, taurine, monosulfated, and polysulfated conjugates using the lipophilic anion exchanger diethylaminohydroxypropyl Sephadex LH-20 (DEAP-LH-20). After solvolysis and hydrolysis, the deconjugated bile acids are purified on DEAP-LH-20, and are converted to methyl ester trimethylsilyl ether derivatives. Identification and quantitation of the individual bile acids is accomplished by computerized gas-liquid chromatography-mass spectrometry. The daily excretion of bile acids in urine from healthy subjects was 6.4-11 micro moles. The mixture of bile acids was quite complex and differed from that in bile. About 30 bile acids were identified or partially characterized. Three of these were monosubstituted: lithocholic, allolithocholic, and 3beta-hydroxy-5-cholenoic acids. Fourteen disubstituted bile acids included epimers of deoxycholic, allodeoxycholic, chenodeoxycholic, allochenodeoxycholic, and hyodeoxycholic acids. 3alpha-Hydroxy-12-keto-5beta-cholanoic acid was the major ketonic bile acid and 3beta,12alpha-dihydroxy-5-cholenoic acid was the major unsaturated bile acid in this group. Nine trihydroxy bile acids included cholic and allocholic acids, epimers of these compounds, hyocholic acid, and a 1-hydroxylated bile acid tentatively characterized as 1,3,12-trihydroxycholanoic acid. Cholestatic subjects excreted tetrahydroxycholanoates carrying hydroxyl groups in positions 1, 3, 6, 7, 12, or 23. All monohydroxy and the predominant part of dihydroxy bile acids were present in the monosulfate fraction. Exceptions were 3alpha,12beta-dihydroxy- and 3alpha-hydroxy-12-keto-5beta-cholanoic acids, which were found mainly in the glycine conjugate fraction. Most of the trihydroxy bile acids were nonsulfated, and cholic and norcholic acids were the major unconjugated bile acids. The tetrahydroxy bile acids and hyocholic acid were present mainly in the taurine conjugate fraction, while 1,3,12-trihydroxycholanoic acid was predominantly found in the glycine conjugate fraction. Sulfation of trihydroxy bile acids was increased in patients with marked cholestasis. All bile acids in the monosulfate fraction were conjugated and carried the sulfate ester group at C-3. Significant amounts of di- and trisulfates were not found. The results indicate selective mechanisms for sulfation, hydroxylation, and renal elimination of bile acid conjugates. Analysis of metabolic profiles of bile acids in urine may be a useful method in studies of the function of organs involved in bile acid metabolism. PMID:864325

Almé, B; Bremmelgaard, A; Sjövall, J; Thomassen, P

1977-05-01

72

In vitro oxidation of i.v. lipid emulsions in different all-in-one admixture bags assessed by an iodometric assay and gas-liquid chromatography.  

PubMed

Polyunsaturated fatty acids (FAs) of intravenous (IV) lipid emulsions can peroxidize to potentially harmful lipid hydroperoxides. In order to assess in vitro peroxidation of IV fat emulsions in all-in-one (AIO) admixture bags, an iodometric titration to determine lipid hydroperoxide content expressed by the peroxide value (PV) and a gas-liquid chromatographic (GLC) assay to determine changes of the FA pattern were established. A long-chain triglyceride (LCT) and medium-chain triglyceride-LCT emulsion were compared for the PV and the pH during storage at room temperature and daylight in AIO bags made of ethylvinylacetate (EVA) and polypropylene:polyamide 7:3 (V90). In contrast to storage in glass bottles, significant peroxidation was detected in both emulsions with 0.5-3.4 mmol peroxides/L after 28 d (150 times the control PV). A pH drop of at least 0.3 (EVA) and 1.2 (V90) units was measured. Initial PVs and peroxidation kinetics of the emulsions were different; V90 material showed better barrier properties against oxygen. PV was increased by higher temperature and light exposure. The FA pattern of an LCT emulsion with a PV > 6 (storage: 40 degrees C in a dark room for 28 d in AIO bags) assayed by GLC remained unchanged. The iodometric peroxide and the GLC assay were reproducible and easy to handle. Only the iodometric method was sensitive enough to detect peroxidation effects (detection limit: 0.02 mmol peroxides/L). IV fat emulsions can be checked for lipid hydroperoxide content with the rapid iodometric assay to guarantee optimal quality of IV lipids used for AIO admixtures. To prevent peroxidation, lipids in AIO bags should be stored light-protected in a refrigerator an oxygen-tight overwrap is mandatory for extended periods. PMID:9106791

Steger, P J; Mühlebach, S F

1997-02-01

73

Gas-liquid flows -- 1993  

Microsoft Academic Search

This symposium was sponsored by the Multiphase Flow Committee of the ASME Fluids Engineering Division. The objective of the symposium was to bring together researchers, and practicing engineers in the area of gas-liquid flows, to share their knowledge and discuss the state of the art. Gas-liquid flows appear in a multitude of settings, some natural and some designed to achieve

J. H. Kim; T. OHern; M. P. Sharma; M. Shoukri

1993-01-01

74

Differentiation of Corynebacterium amycolatum, C. minutissimum, C. striatum and related species by pyrolysis-gas-liquid chromatography with atomic emission detection  

Microsoft Academic Search

We report here the application of pyrolysis-gas chromatography followed by atomic emission detection (AED) for the characterisation of Corynebacterium amycolatum and related species (i.e., C. striatum, C. minutissimum, C. xerosis and the recently described C. freneyi). This phenotypic method, which analyses the whole chemical composition of bacteria, clearly separates C. amycolatum from other species. Moreover, this C. amycolatum group is

Sébastien Voisin; Daniel Deruaz; Jean Freney; François N. R. Renaud

2002-01-01

75

Separation of petroselinic ( cis -6 18:1) and oleic ( cis -9 18:1) acids by gas-liquid chromatography of their isopropyl esters  

Microsoft Academic Search

Petroselinic (cis-6 18:1) and oleic (cis-9 18:1) acids that occur together in Umbelliferae seeds can be resolved by gasliquid chromatography (GLC) of their methyl\\u000a or isopropyl esters on a 50 m 0.25 mm fused-silica capillary column coated with a 100% cyanopropyl polysiloxane stationary\\u000a phase (CP Sil 88). The use of isopropyl esters instead of methyl esters increases the difference between

Robert L. Wolff; Frederic F. Vandamme

1992-01-01

76

Gas-liquid chromatography-tandem mass spectrometry methodology for the quantitation of estrogenic contaminants in bile of fish exposed to wastewater treatment works effluents and from wild populations.  

PubMed

Fish can be exposed to a complex mixture of chemical contaminants arising from the exposure to wastewater treatment works (WwTWs) effluents. Some of these contaminants are estrogenic and have been associated with feminisation of male fish and the presence of populations containing intersex individuals. However the detection of trace levels (ng/L) of estrogenic chemicals surface waters can be difficult and does not give information on the exposure of aquatic organisms to these contaminants. In this study we assessed whether the analysis of estrogenic substances that bioconcentrate in fish bile can be used to detect the exposure of fish to feminising contaminants in receiving waters and effluents, and thus facilitate their monitoring of these substances in aquatic environments. Estrogenic metabolites in bile were deconjugated using enzymatic hydrolysis and partially purified by solid phase extraction. Steroidal and xenoestrogens were derivatized to their trimethylsilyl ethers and quantified by gas-liquid chromatography-mass spectrometry (GC-MS/MS) using multiple reaction monitoring. The method was validated using spiked bile samples from immature female rainbow trout (Oncorhynchus mykiss) as well as bile from sexually mature roach (Rutilus rutilus) that had been exposed to either tap water or an undiluted estrogenic effluent for 10 days or captured from a river site downstream of a WwTWs effluent discharge. The mean recovery of target analytes from spiked bile was between 86 and 99% and the limit of detection was between 0.1 and 0.7ng/mL bile for bisphenol A (BPA), 17beta-estradiol (E2), estrone (E1) and 17alpha-ethinylestradiol (EE2), and 11, 60 and 327ng/mL bile for branched nonyl chain isomeric mixtures of 4-nonylphenolethoxylate (NP1EO), 4-nonylphenol (NP) and 4-nonylphenoldiethoxylate (NP2EO), respectively. All target analytes were detected in bile from roach exposed directly to a WwTWs effluent, with concentrations between 6-13microg/mL bile for NP, 18-21microg/mL for NP1EO, 75-135microg/mL for NP2EO, 0.7-2.5microg/mL for BPA, E2 and E1 and 17-29ng/mL for EE2. With the exception of NP2EO, all analytes were detected in at least 2 out of the 5 fish sampled from the River Thames. BPA and NP1EO were detected in all three reference fish held in tap water indicating possible contamination from laboratory plastics. The work shows that analysis of 20-100microL quantities of bile could be a useful approach in detecting exposure to mixtures of estrogenic contaminants taken up by fish from WwTW effluents and has the potential for monitoring the efficacy of remediation strategies that may be adopted for reduction of these endocrine disrupting chemicals in the aquatic environment. PMID:19932485

Fenlon, Kate A; Johnson, Andrew C; Tyler, Charles R; Hill, Elizabeth M

2009-10-30

77

Gas-liquid chromatographic determination of chloramphenicol in agricultural crops.  

PubMed

A method is presented for the gas-liquid chromatographic determination of chloramphenicol in agricultural crops. Chloramphenicol is extracted with ethyl acetate, cleaned up by silicic acid column chromatography, acetylated with acetic anhydride and pyridine, and then measured by gas-liquid chromatography with electron capture detection. Two stationary phases, DEGS + phosphoric acid and Reoplex 400, were used. The sensitivity was ca 8 ng (40% full scale deflection). The efficicency of the analytical method was evaluated by analyzing crops fortified with chloramphenicol. The average recovery ranged from 72% in unpolished rice to 86% in Chinese radishes. PMID:965336

Sasaki, K; Takeda, M; Uchiyama, M

1976-09-01

78

A method for the confirmation and identification of drugs of misuse in urine using solid phase extraction and gas-liquid chromatography with mass spectrometry.  

PubMed Central

A method is described for the confirmation/identification of a range of commonly misused drugs in urine samples. The method has been used for two years without problems for a range of purposes including hospital/clinic drugs of misuse screening and for toxicology in coroner's cases. Urine samples which have given a positive result on immunochemical screening for a particular drug group or groups (for example, opiates) can be processed with identification of the drugs present using a single procedure. Bond ElutCertify columns are used for the extraction of drugs from the samples followed by propionylation and gas chromatography with mass selective detection.

Galloway, J H; Ashford, M; Marsh, I D; Holden, M; Forrest, A R

1998-01-01

79

Differentiation of Corynebacterium amycolatum, C. minutissimum, C. striatum and related species by pyrolysis-gas-liquid chromatography with atomic emission detection.  

PubMed

We report here the application of pyrolysis-gas chromatography followed by atomic emission detection (AED) for the characterisation of Corynebacterium amycolatum and related species (i.e., C. striatum, C. minutissimum, C. xerosis and the recently described C. freneyi). This phenotypic method, which analyses the whole chemical composition of bacteria, clearly separates C. amycolatum from other species. Moreover, this C. amycolatum group is subdivided into two distinct subgroups. We cannot differentiate the C. minutissimum strains from those of C. striatum. On the other hand, C. freneyi and C. xerosis are clearly distinct from the other species. PMID:12160322

Voisin, Sébastien; Deruaz, Daniel; Freney, Jean; Renaud, François N R

2002-06-01

80

Diversity of Aeromonas sp. in Flemish drinking water production plants as determined by gas-liquid chromatographic analysis of cellular fatty acid methyl esters (FAMEs).  

PubMed

Gas-liquid chromatography of cellular fatty acid methyl esters (FAMEs) was used to determine the phenotypic and genotypic diversity among 489 presumptive Aeromonas strains isolated from five Flemish drinking water production plants. FAME profiles were compared with the predetermined library profiles of a representative database, AER48C, which contains the mean FAME data of all 14 currently established hybridization groups (HGs) or genospecies within Aeromonas. Using AER48C, more than 93% (457 strains) of all presumptive aeromonads isolated on ampicillin-dextrin agar were unequivocally identified as belonging to this genus. Moreover, 85.5% and 73.5% of these strains could be assigned to a particular phenospecies or HG, respectively. Raw and treated surface water samples were dominated by members of the Aer. hydrophila complex (38.8%, comprising HGs 1-3), followed by the Aer. caviae complex (22.7%, comprising HGs 4-6) and the Aer. sobria complex (16.7%, comprising HGs 7-9). HGs 3, 5A/B and 8 were the most prominent genospecies in this type of water. On the other hand, it was found that raw and treated phreatic groundwater samples displayed a much more limited species diversity since these were almost entirely dominated (95.8%) by strains belonging to HGs 2 and 3 of the Aer. hydrophila complex. In general, flocculation-decantation and sand filtration were not shown to influence the overall species distribution in any of the plants examined. PMID:7744729

Huys, G; Kersters, I; Vancanneyt, M; Coopman, R; Janssen, P; Kersters, K

1995-04-01

81

Air analysis by gas chromatography  

Microsoft Academic Search

This review of gas chromatographic air analysis considers approximately 170 research articles published in the literature from 1995 to 1998. The focus is on sample collection, injection, separation and detection techniques, with special emphasis on capillary gas chromatography details. These parameters are summarized in two tables, the first one ordered by the chemical groups of compounds analyzed and the second

Detlev Helmig

1999-01-01

82

Sperm whale oil analysis by gas chromatography and mass spectrometry  

Microsoft Academic Search

Gas liquid chromatography of winterized sperm oil showed that its wax esters with even carbon numbers range from C24 to C42 and are present in quantities resembling a normal distribution curve with C34 as the mean. Between these even-numbered wax esters, ones with odd chain lengths were eluted. Triglycerides, similarly present\\u000a in a normal distribution pattern, ranged from C42 to

G. F. Spencer; W. H. Tallent

1973-01-01

83

An analysis of critical simultaneous gas\\/liquid flow through a restriction and its application to flowmetering  

Microsoft Academic Search

Summary  A theoretical analysis is presented of the mechanism of simultaneous flow of gas and liquid through a restriction at critical\\u000a speed. The study shows that a relationship exists between the mass flows of gas and liquid, restriction size and upstream\\u000a pressure. Comparison of this relationship with measurements showed a reasonable agreement. It has therefore been concluded\\u000a that a restriction can

N. C. J. Ros

1960-01-01

84

Advances in gas-liquid flows 1990  

SciTech Connect

Gas-liquid two-phase flows commonly occur in nature and industrial applications. Rain, clouds, geysers, and waterfalls are examples of natural gas-liquid flow phenomena, whereas industrial applications can be found in nuclear reactors, steam generators, boilers, condensers, evaporators, fuel atomization, heat pipes, electronic equipment cooling, petroleum engineering, chemical process engineering, and many others. The household-variety phenomena such as garden sprinklers, shower, whirlpool bath, dripping faucet, boiling tea pot, and bubbling beer provide daily experience of gas-liquid flows. The papers presented in this volume reflect the variety and richness of gas-liquid two-phase flow and the increasing role it plays in modern technology. This volume contains papers dealing with some recent development in gas-liquid flow science and technology, covering basic gas-liquid flows, measurements and instrumentation, cavitation and flashing flows, countercurrent flow and flooding, flow in various components and geometries liquid metals and thermocapillary effects, heat transfer, nonlinear phenomena, instability, and other special and general topics related to gas-liquid flows.

Kim, J.M. (Texas Univ., Austin, TX (United States). Nuclear Reactor Lab.); Rohatgi, U.S. (Brookhaven National Lab., Upton, NY (United States)); Hashemi, A. (Lockheed Missiles and Space Company (US))

1990-01-01

85

Gas chromatography-mass spectrometry (GC-MS) analysis of ...  

Treesearch

Title: Gas chromatography-mass spectrometry (GC-MS) analysis of ... trial using Gas Chromatography-Mass Spectrometry (GC-MS) detected differences in fatty acid ... methanol, chloroform, fatty acids, mass spectrometry, gas chromatography , ...

86

Advances in gas-liquid flows 1990  

Microsoft Academic Search

Gas-liquid two-phase flows commonly occur in nature and industrial applications. Rain, clouds, geysers, and waterfalls are examples of natural gas-liquid flow phenomena, whereas industrial applications can be found in nuclear reactors, steam generators, boilers, condensers, evaporators, fuel atomization, heat pipes, electronic equipment cooling, petroleum engineering, chemical process engineering, and many others. The household-variety phenomena such as garden sprinklers, shower, whirlpool

J. M. Kim; A. Hashemi

1990-01-01

87

Supercritical fluid chromatography in food analysis.  

PubMed

In the last years, supercritical fluid chromatography (SFC) has increased its acceptance between scientists. The unique selectivity, short analysis times, low consumption of organic solvents as well as the improvements in instrumentation have contributed to expand its use. These characteristics make SFC a powerful tool when food analysis requires individualized evaluation of several compounds in very complex samples. In this work, the advantages and main applications of SFC in food analysis are reviewed, focusing special attention onto analytical and preparative separations. PMID:23891212

Bernal, José L; Martín, María T; Toribio, Laura

2013-07-09

88

Analysis of complex lipid mixtures by thin-layer chromatography and complementary methods  

Microsoft Academic Search

Conclusion  Further work has been done on the application of thin-layer adsorption chromatography to the fractionation of complex lipid\\u000a mixtures into classes.\\u000a \\u000a New methods, the use of siliconized silicic acid plates and the application of thin-layer adsorption chromatography combined\\u000a with the complementary techniques of gas-liquid chromatography and paper chromatography, are presented for the resolution\\u000a of classes of lipids into their constituents.

Donald C. Malins; Helmut K. Mangold

1960-01-01

89

FSU's natural gas liquids business needs investment  

SciTech Connect

Production of natural gas liquids has fallen seriously behind its potential in the former Soviet Union (FSU). Restoration of the gas liquids business thus represents a rich investment opportunity. Capital, however, must come from international sources, which remain uncertain about the FSU's legal, commercial, and political systems. If these hurdles can be overcome, FSU output of liquid petroleum gas alone might double between 1990 and 2010. In the FSU, LPG is produced from associated and nonassociated natural gas, condensate, and refinery streams. It also comes from what is known in the FSU as ShFLU--a mixture of propane, butane, pentane, and hexane produced at gas processing plants in Western Siberia and fractionated elsewhere. The paper reviews FSU production of gas liquids focusing on West Siberia, gives a production outlook, and describes LPG use and business development.

Plotnikov, V.S.; Berman, M.; Angerinos, G.F. (Poten and Partners Inc., New York, NY (United States))

1995-03-13

90

Gas-liquid contacting in mixing vessels  

SciTech Connect

This report by Dr. R. Mann of UMIST presents a critical survey of literature on the contacting of gases with liquids in stirred vessels. Research undertaken in the last fifteen years in analysed, and promising areas for future research are identified. The report deals with physical contacting, mass transfer between the gas and liquid phases and the utilisation of the stirred vessel as a gas-liquid reactor. Three sections are given on gas-liquid contacting: physical aspects; interphase mass transfer; and chemical reactions. It also discusses recent new approaches and includes a summary of conclusions, nomenclature and references.

Mann, R.

1983-01-01

91

Gas-Liquid Processing in Microchannels  

Microsoft Academic Search

Processing gases and liquids together in microchannels having at least one dimension <1 mm has unique advantages for rapid heat and mass transfer. One approach for managing the two phases is to use porous structures as wicks within microchannels to segregate the liquid phase from the gas phase. Gas-liquid processing is accomplished by providing a gas flow path and inducing

Ward E. TeGrotenhuis; Victoria S. Stenkamp; Alvin Twitchell

2005-01-01

92

Chromatography coupled atomic fluorescence spectrometry for mercury species analysis  

Microsoft Academic Search

Pretreatment and determination for mercury species based on coupled chromatography techniques especially the combination of liquid chromatography with atomic fluorescence spectrometry were reviewed in this paper with 17 references, and the new trends for trace and ultra-trace of mercury species analysis in the future was also carried out. Keywords-Envionment, pretreatment, mercury speciation analysis; liquid chromatography, atomic fluorescence spectrometry. I. INTRODUCTION

Juan Chen; Xiaoping Yu; Yafei Guo; Tianlong Deng

2011-01-01

93

Chromatography.  

ERIC Educational Resources Information Center

|This booklet presents some activities on chromatography. Directions for preparing leaf pigment extracts using alcohol are given, and paper chromatography and thin-layer chromatography are described as modifications of the basic principles of chromatography. (KHR)|

Brantley, L. Reed, Sr.; Demanche, Edna L.; Klemm, E. Barbara; Kyselka, Will; Phillips, Edwin A.; Pottenger, Francis M.; Yamamoto, Karen N.; Young, Donald B.

94

Chirospecific analysis of plant volatiles  

Microsoft Academic Search

Characteristic features of the analysis of plant volatiles by enantioselective gas (gas-liquid) chromatography and gas chromatography\\/mass spectrometry are discussed. The most recent advances in the design of enantioselective stationary phases are surveyed. Examples of the preparation of the most efficient phases based on modified cyclodextrins are given. Current knowledge on the successful analytical resolution of different types of plant volatiles

A. V. Tkachev

2007-01-01

95

Electron capture gas-liquid chromatographic-mass spectral identification of acids produced by Neisseria meningitidis in a defined medium.  

PubMed

The acid metabolites and the cellular fatty acids of three strains of Neisseria meningitidis grown in a chemically defined liquid medium were determined with computerized frequency-pulsed electron capture gas-liquid chromatography. Five acids not previously reported were subsequently identified: isobutyric, octanoic, decenoic (C10:1), dodecenoic (C12:1), and tetradecenoic (C14:1). These acids were produced during active metabolism and were not detected as cellular constituents. The frequency-pulsed electron capture gas-liquid chromatography methods which we used provide a rapid, reliable, sensitive means of detecting both these and other metabolic and cellular acids in spent culture medium. PMID:107187

Alley, C C; Brooks, J B; Kellogg, D S

1979-01-01

96

Ion Chromatography Analysis of Dibutyl Phosphoric Acid  

SciTech Connect

Analysis of dibutyl phosphate (DBP), a degradation product of tributyl phosphate (TBP), has long been a problem analysis by Ion Chromatography at the Savannah River Site. Due to the presence of UO{sub 2}{sup +2} and high NO{sub 3}{sup {minus}1} concentrations, inadequate recovery and separation of DBP on the chromatographic column had rendered the analysis undependable and very inconsistent, thus causing high uncertainties in the data. The method presented here by the Savannah River Technology Center (SRTC)/Analytical Development Section (ADS) addresses the sample preparation problems encountered when analyzing for DBP in the presence of uranium and nitrate. The data presented reflects the improvements made to decrease data uncertainty and increase data accuracy and precision.

Ray, R.J.

1998-12-04

97

Novel Gas-Liquid-Solid Reactors  

Microsoft Academic Search

Multiphase reactors involving gas, liquid, and solid phases have several important applications in the chemical industry, particularly in catalytic processes. Some of the well-known examples are: hydrogenation and oxidation of organic compounds, hydro-processing coal-derived and petroleum oils, Fischer-Tropsch synthesis, and methanation reactions. Due to the presence of three phases, the problem of reactor design is often important to achieve effective

R. V. Chaudhari; Y. T. Shah; N. R. Foster

1986-01-01

98

Adsorption potential of hydrocarbons at the gas-liquid interface of water  

Microsoft Academic Search

In this work, the adsorption potential of 5 hydrocarbons is calculated at the gas-liquid interface of water and compared to the minimum value with the experimental adsorption energy obtained at zero surface coverage by gas chromatography. For 3 of the molecules (n-pentane, n-hexane, and n-heptane), the calculation consisted of dispersion and induction interactions between solute and liquid adsorbent. For 2

Claire Vidal-Madjar; Georges Guiochon; Barry L. Karger

1976-01-01

99

Hydrodynamics of stirred gas-liquid dispersions  

NASA Astrophysics Data System (ADS)

Results of an investigation of the gas-liquid hydrodynamics of stirred tanks equipped with (profiled) axial flow impellers are reported. Three different flow regimes are distinguished. Only at low gas flow rates, when the gas-liquid flow is dominated by the liquid flow pattern as induced by the impeller, the flow pattern is steady state and the gas well dispersed. The mass transfer performance of these axial flow impellers was compared with that of disc turbines. Results of a computational study on the single phase flow with both radial pumping and axial pumping impellers are described. All computations were carried out with the fluid flow code FLUENT and the results were validated with experimental LDV (Laser Doppler Velocimetry) data. These single phase flow patterns serve as a basis for further study of the gas dispersion process in those hydrodynamic regimes where the flow is stable. The development of a predictive model for the gas-liquid flow in stirred vessels is considered. This model is incorporated in a code named GHOST (Gas Holdup Simulation Tool) which calculates local values of gas holdup, bubble size, and mass transfer rate on the basis of conservation equations and the single phase flow patterns computed earlier. The computational results are validated against experimental data gathered with optical fiber probes. A qualitative description of the spatial distribution of the gas holdup, the bubble size, and the mass transfer rate in stirred mixing vessels is given. This description results from using a combination of experimental data and GHOST results. Conclusions about further possible optimization of gassed stirred tanks are drawn.

Bakker, Andries

100

Novel Mesogenic Polysiloxane Solvents for Gas-Liquid Chromatography.  

National Technical Information Service (NTIS)

The open-tubular column gas-chromatographic properties of a member of a new class of mesogenic polysiloxane (PMMS) phases are described and compared with those of a polymethylphenylsiloxane solvent (SE-52). The former is shown to yield high column efficie...

H. Finkelmann R. J. Laub

1982-01-01

101

Observation of the fluid pulsation behind a prism in gas-liquid annular flow  

NASA Astrophysics Data System (ADS)

The fluid pulsation behind a prism is closely concerned with the design and operation of gas-liquid two-phase flow systems. This paper explored the property of such fluid pulsations in a horizontal pipe using air and water as the tested media. The pressure difference between the upstream and downstream of the prism was adopted to represent the characteristics of the fluid pulsation. Based on the experimental results, it is found that there exit obvious pulsations in the fluid behind the prism in annular flows, and this pulsation is more marked at low gas mass qualities than those at high gas mass qualities. Furthermore, the average pressure basically decreases with the gas mass quality and increases with the gas-liquid total mass flowrate. These findings could be useful for the analysis of flowing characteristics in gas-liquid annular flow across a prism.

Sun, Zhiqiang; Sang, Wenhui; Zhang, Hongjian

2009-02-01

102

Mass transfer during gas absorption in a vertical gas-liquid slug flow with small bubbles in liquid plugs  

Microsoft Academic Search

A model is developed for the analysis of mass transfer during isothermal absorption in a vertical gas-liquid slug flow at\\u000a large Reynolds numbers with liquid plugs containing small bubbles. Simple formulas for mass flux from the N-th unit cell of gas-liquid slug flow and for total mass flux from N unit cells are derived. In the limiting case the derived

T. Elperin; A. Fominykh

1998-01-01

103

Gas-liquid chromatographic determination of sulfamethazine in swine and cattle tissues.  

PubMed

A gas-liquid chromatographic (GLC) method is described for determining sulfonamide residues in animal tissues, with specificity for 7 sulfonamides. Residues are extracted from tissues with acetone-chloroform, fatty substances are removed, and the sulfonamide residue is methylated with diazomethane in acetone-ether to render it amenable to determination by gas-liquid chromatography on an all-glass column suitable for direct on-column injection and a Ni electron-capture detector. Quantitation is achieved by external standardization. The method has a validated limit of sensitivity of 0.10 ppm with the corresponding control values for all tissues being less than 0.01 ppm. Satisfactory recoveries have been obtained for sulfamethazine in swine and cattle tissues. Specificity for sulfamethazine in the presence of sulfathiazole, sulfaquinoxaline, sulfadimethoxine, sulfabromomethazine, sulfaethoxypyridazine, and sulfachloropyrazine is attained by resolution of the respective methyl derivatives on the GLC column. PMID:7275892

Manuel, A J; Steller, W A

1981-07-01

104

Thermal transistor utilizing gas-liquid transition.  

PubMed

We propose a simple thermal transistor, a device to control heat current. In order to effectively change the current, we utilize the gas-liquid transition of the heat-conducting medium (fluid) because the gas region can act as a good thermal insulator. The three terminals of the transistor are located at both ends and the center of the system, and are put into contact with distinct heat baths. The key idea is a special arrangement of the three terminals. The temperature at one end (the gate temperature) is used as an input signal to control the heat current between the center (source, hot) and another end (drain, cold). Simulating the nanoscale systems of this transistor, control of heat current is demonstrated. The heat current is effectively cut off when the gate temperature is cold and it flows normally when it is hot. By using an extended version of this transistor, we also simulate a primitive application for an inverter. PMID:21405731

Komatsu, Teruhisa S; Ito, Nobuyasu

2011-01-25

105

Thermal transistor utilizing gas-liquid transition  

NASA Astrophysics Data System (ADS)

We propose a simple thermal transistor, a device to control heat current. In order to effectively change the current, we utilize the gas-liquid transition of the heat-conducting medium (fluid) because the gas region can act as a good thermal insulator. The three terminals of the transistor are located at both ends and the center of the system, and are put into contact with distinct heat baths. The key idea is a special arrangement of the three terminals. The temperature at one end (the gate temperature) is used as an input signal to control the heat current between the center (source, hot) and another end (drain, cold). Simulating the nanoscale systems of this transistor, control of heat current is demonstrated. The heat current is effectively cut off when the gate temperature is cold and it flows normally when it is hot. By using an extended version of this transistor, we also simulate a primitive application for an inverter.

Komatsu, Teruhisa S.; Ito, Nobuyasu

2011-01-01

106

Development of a new temperature measuring system for gas–liquid flow in spraying field  

Microsoft Academic Search

Based on previous work, a new temperature measuring system for gas–liquid flow, composed of shielded and unshielded thermocouples, on-line laser detection device for liquid droplets, vacuum pump and wavelet analysis data processor, is developed in this work. The necessity of vacuum pump and the criterion of mesh size selection are also described. Through an application of measuring temperature in saturator,

Yixing Li; Yuzhang Wang; Shilie Weng; Yonghong Wang

2007-01-01

107

Gas-Liquid Jets under Reduced Gravity Conditions.  

National Technical Information Service (NTIS)

Experimental drafts for the investigation of the behavior of gas-liquid jets under microgravity conditions and a conception of a facility to use inside the capsule of the drop tower Bremen are presented. Gas-liquid jets are very important subjects of flui...

O. Pamperin H. J. Rath

1992-01-01

108

Thin Layer Chromatography for the Analysis of Glycosaminoglycan Oligosaccharides  

PubMed Central

Thin layer chromatography was used to analyze glycosaminoglycan oligosaccharides obtained through the use of polysaccharide lyases. This method allows for the rapid, semi-quantitative analysis of a wide variety of glycosaminoglycan oligosaccharides.

Zhang, Zhenqing; Xie, Jin; Zhang, Fuming; Linhardt, Robert J.

2007-01-01

109

Characterization of Horizontal Gas-Liquid Two-Phase Flow Using Markov Model-Based Complex Network  

NASA Astrophysics Data System (ADS)

Horizontal gas-liquid two-phase flow widely exists in many physical systems and chemical engineering processes. Compared with vertical upward gas-liquid two-phase flow, investigations on dynamic behavior underlying horizontal gas-liquid flows are quite limited. Complex network provides a powerful framework for time series analysis of complex dynamical systems. We use a network generation method based on Markov transition probability to infer directed weighted complex networks from signals measured from horizontal gas-liquid two-phase flow experiment and find that the networks corresponding to different flow patterns exhibit different network structure. To investigate the dynamic characteristics of horizontal gas-liquid flows, we construct a number of complex networks under different flow conditions, and explore the network indices for each constructed network. In addition, we investigate the sample entropy of different flow patterns. Our results suggest that the network statistic can well represent the complexity in the transition among different flow patterns and further allows characterizing the interface fluctuation behavior in horizontal gas-liquid two-phase flow.

Hu, Li-Dan; Jin, Ning-De; Gao, Zhong-Ke

2013-05-01

110

Micellar electrokinetic chromatography Perspectives in drug analysis  

Microsoft Academic Search

Micellar electrokinetic chromatography (MEKC) has become a popular mode among several capillary electromigration techniques. Most drug analyses can be performed by using MEKC because of its wide applicability. Enantiomer separation, separation of closely related peptides and isotopic compounds, separation of very complex mixtures, determination of drugs in the biological samples, etc., can be succesfully achieved by MEKC. This review surveys

Nishi Hiroyuki; Shigeru Terabe

1996-01-01

111

Thin layer chromatography analysis of photocopy toners  

Microsoft Academic Search

Sixteen photocopy toners, consisting of different brands, as well as different models of the same brand, were analyzed with the help of thin layer chromatography (TLC). Dye components as well as resin components were analyzed and the results are presented. A modified technique to lift the toner from the photocopy is also described.

G. Tandon; O. P. Jasuja; V. N. Sehgal

1995-01-01

112

Targeted analysis of glycomics liquid chromatography\\/mass spectrometry data  

Microsoft Academic Search

Hydrophilic interaction chromatography (HILIC) liquid chromatography\\/mass spectrometry (LC\\/MS) is appropriate for all native\\u000a and reductively aminated glycan classes. HILIC carries the advantage that retention times vary predictably according to oligosaccharide\\u000a composition. Chromatographic conditions are compatible with sensitive and reproducible glycomics analysis of large numbers\\u000a of samples. The data are extremely useful for quantitative profiling of glycans expressed in biological tissues.

Jonathan M. Dreyfuss; Christopher Jacobs; Yevgeniy Gindin; Gary Benson; Gregory O. Staples; Joseph Zaia

2011-01-01

113

Separation and IR Analysis of a Mixture of Organic Compounds.  

ERIC Educational Resources Information Center

Presents an experiment which includes fractional distillation with gas-liquid chromatography (GLC) and infrared analysis. Objectives are to introduce students to fractional distillation and analysis of each fraction by GLC, to induce them to decide if each fraction is sufficient for infrared analysis, and to identify unknowns. (Author/JN)

Thompson, Evan M.; Almy, John

1982-01-01

114

Separation and IR Analysis of a Mixture of Organic Compounds.  

ERIC Educational Resources Information Center

|Presents an experiment which includes fractional distillation with gas-liquid chromatography (GLC) and infrared analysis. Objectives are to introduce students to fractional distillation and analysis of each fraction by GLC, to induce them to decide if each fraction is sufficient for infrared analysis, and to identify unknowns. (Author/JN)|

Thompson, Evan M.; Almy, John

1982-01-01

115

Gas-liquid separator and method of operation  

DOEpatents

A system for gas-liquid separation in electrolysis processes is provided. The system includes a first compartment having a liquid carrier including a first gas therein and a second compartment having the liquid carrier including a second gas therein. The system also includes a gas-liquid separator fluidically coupled to the first and second compartments for separating the liquid carrier from the first and second gases.

Soloveichik, Grigorii Lev (Latham, NY); Whitt, David Brandon (Albany, NY)

2009-07-14

116

Backmixing in gas-liquid reactors. [233 references  

Microsoft Academic Search

This review evaluates the present state of the art on backmixing in gas-liquid and gas-liquid-solid reactors. A brief outline of numerous techniques for measuring residence time distribution (RTD) of various phases in a multiphase reactor is presented. This is followed by a brief description of differential and stagewise models for characterizing backmixing from RTD measurements. Both simple (that is, single-parameter

Y. T. Shah; G. J. Stiegel; M. M. Sharma

1978-01-01

117

Mass transfer in gas-liquid slurry reactors  

Microsoft Academic Search

A critical review is presented on the mass transfer characteristics of gas¿liquid slurry reactors. The recent findings on the influence of the presence of solid particles on the following mass transfer parameters in slurry reactors are discussed: volumetric gas¿liquid mass transfer coefficients (kLa, kGa), liquid-side mass transfer coefficients (kL and kS) and specific gas¿slurry contact area (a). The second part

A. A. C. M. Beenackers; Swaaij van W. P. M

1993-01-01

118

AcidBase Equlibria in Open Atmospheric Gas-Liquid Systems  

Microsoft Academic Search

Analysis of acid-base equilibria in open atmospheric gas-liquid systems was performed. Usually acid-base equilibria are considered as a function of hydrogen ion concentration as an independent variable. In this work the analysis was performed including the dependence of hydrogen ion concentration on the composition of a system. Such an approach allowed us to find the important, from the point of

I. Wilkosz

2005-01-01

119

Chromatography  

NSDL National Science Digital Library

The North Carolina Community College System BioNetwork's interactive eLearning tools (IETs) are reusable chunks of training that can be deployed in a variety of courses or training programs. IETs are designed to enhance, not replace hands-on training. Learners are able to enter a hands-on lab experience better prepared and more confident. This particular IET delves into chromatography including the basics, the three types (affinity, ion exchange, size exclusion), and the parts and functions associated with chromatography.

2011-11-29

120

Chromatography  

NSDL National Science Digital Library

In this chemistry activity, learners will separate a mixture of FD&C dyes (colors certified and allowed by the US for the Food, Pharmaceutical, Cosmetics & Personal Care industry) to practice chromatography, a separation technique for mixtures. Learners will record their observations on a data table and note trends. This resource includes questions for learners and instructions for preparing the colors from M&Ms, Orange Kool-Aid, and food coloring.

House, The S.

2013-05-15

121

Aroma analysis of coffee brew by gas chromatography-olfactometry  

Microsoft Academic Search

During the study of coffee flavor, the processes of brewing, extraction and sampling cause losses of the aroma compounds present in coffee grounds. In this study, coffees from two brewing methods were extracted, serially diluted and each dilution sniffed twice using the gas chromatography-olfactometry (GCO) technique called CharmAnalysis™. Among the hundreds of volatile chemicals present, 18 of the thirty most

K. D. Deibler; T. E. Acree; E. H. Lavin

1998-01-01

122

Using Single Drop Microextraction for Headspace Analysis with Gas Chromatography  

ERIC Educational Resources Information Center

|Headspace (HS) gas chromatography (GC) is commonly used to analyze samples that contain non-volatiles. In 1996, a new sampling technique called single drop microextraction, SDME, was introduced, and in 2001 it was applied to HS analysis. It is a simple technique that uses equipment normally found in the undergraduate laboratory, making it ideal…

Riccio, Daniel; Wood, Derrick C.; Miller, James M.

2008-01-01

123

Discussion of jump condition at gas-liquid interface  

NASA Astrophysics Data System (ADS)

A modeling of gas-liquid interface is one of key issues of the numerical research on multiphase flow. Currently, the Continuum Surface Force model (CSF: Brackbill et al., 1992) is popular to model a gas-liquid interface in computational fluid dynamics. However, the CSF model cannot explain the physics of the gas-liquid interface because this model is derived by a mechanical energy balance at the interface. As a practical matter, we must consider the physics of bubble coalescence or breakup, soap bubble and so on. In this study, assuming that the interface is a thin membrane and has a finite thickness, we develop a new mathematical model of the gas-liquid interface based on thermodynamics and mathematical approach. In particular, we derive the equation of free energy based on Lattice gas model including both influences of the electric double layer caused by a contamination and the jump condition at gas-liquid interface treated by thermodynamics. Finally, we compare this thermodynamic jump condition with the conventional one.

Yonemoto, Yukihiro; Kunugi, Tomoaki

2006-11-01

124

DEVELOPMENT AND VALIDATION OF A MULTIFIELD MODEL OF CHURN-TURBULENT GAS/LIQUID FLOWS  

SciTech Connect

The accuracy of numerical predictions for gas/liquid two-phase flows using Computational Multiphase Fluid Dynamics (CMFD) methods strongly depends on the formulation of models governing the interaction between the continuous liquid field and bubbles of different sizes. The purpose of this paper is to develop, test and validate a multifield model of adiabatic gas/liquid flows at intermediate gas concentrations (e.g., churn-turbulent flow regime), in which multiple-size bubbles are divided into a specified number of groups, each representing a prescribed range of sizes. The proposed modeling concept uses transport equations for the continuous liquid field and for each bubble field. The overall model has been implemented in the NPHASE-CMFD computer code. The results of NPHASE-CMFD simulations have been validated against the experimental data from the TOPFLOW test facility. Also, a parametric analysis on the effect of various modeling assumptions has been performed.

Elena A. Tselishcheva; Steven P. Antal; Michael Z. Podowski; Donna Post Guillen

2009-07-01

125

Investigation on a gas-liquid ejector using three-dimensional CFD model  

NASA Astrophysics Data System (ADS)

This paper is focusing on the numeral study of a gas-liquid ejector used for ballast water treatment. The gasliquid ejector is investigated through steady three-dimensional multiphase CFD analysis with commercial software ANSYS-CFX 13.0. Water as the primary fluid is driven through the driving nozzle and air is ejected into as the second gas instead of the ozone in real application. Several turbulence models such as Standard k-? model, RNG k-? model, SST model and k-? model, and different mesh size and compared extensively with the experimental results to eliminate the influence of the auxiliary system, turbulence models and mesh generation. The appropriate numerical model in terms of the best combination of turbulence model and mesh size are used in the subsequent research the study the influence of the operating condition such as the driving pressure/velocity and the back pressure of the ejector on its performance. The results provide deep insight on the influence of various factors on the performance of gas-liquid ejector. And the proposed numerical model will be very helpful in the further design optimization of the gas-liquid ejectors.

Kang, S. H.; Song, X. G.; Park, Y. C.

2012-11-01

126

[Hydrophilic interaction chromatography and its recent applications in environmental analysis].  

PubMed

Hydrophilic interaction chromatography (HILIC) has been used as a supplement method of reversed-phase liquid chromatography (RPLC) for the separation of the polar and hydrophilic compounds, and has been received more and more attention in recent years. One reason is that the separation problems of strongly polar compounds are rising in various fields. Another is that there are some obvious advantages of HILIC compared with RPLC in the separation of polar compounds, such as low viscosity of mobile phase, good permeability of the column, high sensitivity when coupled to mass spectrometry and low back pressure. In this review, the development history, characteristics and retention mechanism of HILIC are summarized. The main attention in this review is on the applications of HILIC in environmental analysis. In addition, the advantages and disadvantages of HILIC and RPLC in the separation of pollutants are discussed, and the development trends of HILIC applications in environmental analysis are proposed. PMID:22715686

Guo, Yali; Yuan, Qin; Li, Ruiping; Huang, Yingping

2012-03-01

127

Quantitative analysis of lipids by thin-layer chromatography  

Microsoft Academic Search

A procedure is described for the quantitative analysis of neutral and phospholipids by thinlayer chromatography (TLC) employing\\u000a densitometry. The chromatophates are prepared with the usual solvent systems. The spots are charred under standard conditions\\u000a and analyzed with a Photovolt Corp. densitometer equipped with a special stage designed for holding 20×20 cm chromatoplates.\\u000a Each spot on the chromatoplate gives a peak

M. L. Blank; J. A. Schmit; O. S. Privett

1964-01-01

128

Chlorophyll Analysis by New High Performance Liquid Chromatography Methods  

Microsoft Academic Search

The improvements in high performance liquid chromatography (HPLC) analysis of chlorophylls (Chls) and bacteriochlorophylls\\u000a (BChls) during the last decade rely mainly on the application of newly developed stationary phases combined with new mobile\\u000a phases developed with special regard to the nature of the ionpairing agents employed for achieving the retention of free acid\\u000a forms, which is especially important for the

José L. Garrido; Manuel Zapata

129

Quantitative analysis of thuringiensin by micellar electrokinetic capillary chromatography  

Microsoft Academic Search

A method for quantitative analysis of thuringiensin is established using micellar electrokinetic capillary chromatography (MEKC). Tryptophan was used as an internal standard. The running buffer contained phosphate–borate (20 mM) and sodium dodecyl sulfate (100 mM) with 10% acetonitrile. Electrophoresis was conducted under a voltage of 15 kV for 20 min. The peak area ratio of thuringiensin to tryptophan was calculated

Cheng-Ming Liu; Yew-Min Tzeng

1998-01-01

130

Analysis of proanthocyanidins by high-performance gel permeation chromatography  

Microsoft Academic Search

A high-performance gel permeation chromatography method was developed for the analysis of proanthocyanidins. The isocratic method consisted of two porous polystyrene–divinylbenzene columns (300×7.5 mm each, 5 ?m, 100 and 500 Å individual pore size) and a mobile phase consisting of N,N-dimethylformamide containing 1% (v\\/v) acetic acid, 5% (v\\/v) water and 0.15 M lithium chloride. The flow-rate was maintained at 1

James A Kennedy; Alan W Taylor

2003-01-01

131

Speciation analysis by gas chromatography with plasma source spectrometric detection  

Microsoft Academic Search

State-of-the-art species-selective analysis by gas chromatography (GC) with plasma source spectrometric detection is discussed for organometal and organometalloid compounds. Various plasmas, inductively coupled plasma, microwave induced plasma, capacitatively coupled plasma, direct current plasma and alternating current plasma, are characterized and critically compared as sources of radiation for atomic emission spectrometry and sources of ions for mass spectrometry. Interfaces between gas

Ryszard ?obi?ski; Freddy C. Adams

1997-01-01

132

Trace analysis for metals in aerospace materials by gas chromatography. Final report, 1 Feb 1972--1 Jan 1975  

Microsoft Academic Search

Topics discussed are: analysis for beryllium in the environment by gas chromatography (analysis for beryllium in ambient air particulates by gas chromatography, analysis for beryllium in soil, coal fly ash, coal, and wheat straw); analysis for chromium by gas chromatography, (analysis for chromium in lunar material by gas chromatography, chromium extraction studies, analysis for chromium in nbs coal and fly

W. D. Ross; L. Parts; M. S. Black; M. T. Winninger

1975-01-01

133

Evaluation of Methods for Predictions Natural Gas Liquid Density  

Microsoft Academic Search

Due to the importance of liquid density in process design, this study was undertaken to evaluate the accuracy of available correlations, equations of state, and process simulation programs. The study covers natural gas liquid (NGL), liquefied natural gas (LNG) and light hydrocarbons mixtures containing nitrogen. More than 25 binary and multicomponent systems were studies. The accuracy of several correlations, EoSs,

Hameeda Dashti; Ali Moshfeghian; Mahmood Moshfeghian

134

The cyclone gas–liquid separator: operation and mechanistic modeling  

Microsoft Academic Search

A research program was aimed to develop the cyclone gas–liquid separator. The program focused on testing scaled-down models and prototypes and developing mechanistic modeling for the phase separation and flow hydrodynamic processes. This paper describes the operational principles of the cyclone separator, discloses laboratory and field data and presents the modeling foundations. The laboratory tests were performed in downsized models

E. S Rosa; F. A França; G. S Ribeiro

2001-01-01

135

A Lab Experiment to Introduce Gas/Liquid Solubility  

ERIC Educational Resources Information Center

|A simplified version of a volumetric apparatus for gas/liquid solubility measurements is proposed. The procedure familiarizes undergraduate students with the experimental study of the solubility of a gas in a liquid and contributes to the understanding of this important phase equilibrium concept. The experimental results report the determination…

Fonsecaa, I. M. A.; Almeida, J. P. B.; Fachada, H. C.

2008-01-01

136

Simulation of the test stand gas-liquid ejector operation  

Microsoft Academic Search

Based on the data of numerical simulation of the test stand gas-liquid ejector operation, the fields of gasodynamic flow parameters\\u000a in the gas flue channel are determined. The test stand operation in real time and processes of interaction between the flow\\u000a of combustion products and neutralizing liquid are also analyzed.

V. Ya. Modorskii; A. V. Kozlova

2008-01-01

137

Design of gas-liquid injectors and ejectors  

Microsoft Academic Search

the mixing chamber inlet separately forming at the outlet a uniform gas-liquid flow with an equal and uniform velocity of both phases, it will be found that with the increasing coefficient of injection the experimental values of pressure in the device begin to exceed markedly the calculated values. This can be attributed to the nonuniformity of the velocity and density

A. B. Cheskis

1967-01-01

138

Potential of Microbore HPLC (High Performance Liquid Chromatography) for Trace Organic Analysis in the Ocean.  

National Technical Information Service (NTIS)

The adaptation of modern chromatographic techniques, especially capillary gas chromatography and high performance liquid chromatography (HPLC), to seawater analysis has lead to new insights into chemical and biological oceanographic processes. In this pro...

K. Mopper

1986-01-01

139

Analysis of amphetamines by supercritical fluid chromatography, high-performance liquid chromatography, gas chromatography and capillary zone electrophoresis; a preliminary comparison  

Microsoft Academic Search

A supercritical fluid chromatographic method with UV detection (SFC–UV) for the quantitative separation of phenylisothiocyanate (PITC)-derivatised amphetamines is described and compared to high-performance liquid chromatography–diode array detection (HPLC–DAD), gas chromatography–flame ionisation detection (GC–FID) and capillary zone electrophoresis–diode array detection (CZE–DAD) analyses of amphetamine and related compounds. Difficulties in the analysis of common amphetamines by SFC are discussed. Of the methods

Y McAvoy; M. D Cole; O Gueniat

1999-01-01

140

Comprehensive supercritical fluid chromatography × reversed phase liquid chromatography for the analysis of the fatty acids in fish oil  

Microsoft Academic Search

The separation of the phenacyl esters of the fatty acids originating from a fish oil extract by means of a comprehensive analysis using silver-ion (SI) supercritical fluid chromatography (SFC) and reversed phase liquid chromatography (RP-LC) in the first and second dimensions, respectively, is described. The combination ensured a high orthogonality and peak capacity, particularly when compared to the comprehensive RP-LC×2RP-LC

Isabelle François; Pat Sandra

2009-01-01

141

Targeted analysis of glycomics liquid chromatography/mass spectrometry data.  

PubMed

Hydrophilic interaction chromatography (HILIC) liquid chromatography/mass spectrometry (LC/MS) is appropriate for all native and reductively aminated glycan classes. HILIC carries the advantage that retention times vary predictably according to oligosaccharide composition. Chromatographic conditions are compatible with sensitive and reproducible glycomics analysis of large numbers of samples. The data are extremely useful for quantitative profiling of glycans expressed in biological tissues. With these analytical developments, the rate-limiting factor for widespread use of HILIC LC/MS in glycomics is the analysis of the data. In order to eliminate this problem, a Java-based open source software tool, Manatee, was developed for targeted analysis of HILIC LC/MS glycan datasets. This tool uses user-defined lists of compositions that specify the glycan chemical space in a given biological context. The program accepts high-resolution LC/MS data using the public mzXML format and is capable of processing a large data file in a few minutes on a standard desktop computer. The program allows mining of HILIC LC/MS data with an output compatible with multivariate statistical analysis. It is envisaged that the Manatee tool will complement more computationally intensive LC/MS processing tools based on deconvolution and deisotoping of LC/MS data. The capabilities of the tool were demonstrated using a set of HILIC LC/MS data on organ-specific heparan sulfates. PMID:20953780

Dreyfuss, Jonathan M; Jacobs, Christopher; Gindin, Yevgeniy; Benson, Gary; Staples, Gregory O; Zaia, Joseph

2010-10-16

142

Relationships between gas-liquid interfacial surface area, liquid saturation, and light transmission in variably saturated porous media  

NASA Astrophysics Data System (ADS)

Liquid saturation and gas-liquid interfacial area are important parameters for evaluating the transport and fate of contaminants in unsaturated subsurface environments. Recent findings indicate that interfacial surface area controls the relative degree of transmitted light in laboratory systems containing translucent porous media. Equations are derived to estimate the specific gas-liquid interfacial area from the area under the primary-drainage branch of the Seff-h characteristic curve as parameterized using common water retention functions. The total area under the curve provides the maximum available specific gas-liquid interfacial area available at residual saturation, which can be incorporated into the relationship to determine the gas-liquid interfacial area at intermediate degrees of saturation via light transmission. Experimental results, and analysis of external data sets, support these findings. Closed-form relationships are presented as enhancements to a recent method for determination of liquid saturations above residual using light transmission. A physically based model is developed and tested for the quantification of liquid contents below residual saturation.

Niemet, Michael R.; Rockhold, Mark L.; Weisbrod, Noam; Selker, John S.

2002-08-01

143

Capillary gas-liquid chromatographic separation of bile alcohols.  

PubMed

Gas-liquid chromatographic separation of C23, C24, C25, C26, and C27 bile alcohols with either 3 alpha, 7 alpha-dihydroxylated or 3 alpha, 7 alpha, 12 alpha-trihydroxylated ring system on two capillary columns, CP-Sil-19 CB and CP-Sil-5 CB, is described. Bile alcohols with two ring hydroxyl groups at 3 alpha- and 7 alpha-positions consistently showed larger retention times on CP-Sil-19 CB columns and smaller retention times on CP-Sil-5 CB columns than the corresponding bile alcohols with three ring hydroxyl groups at 3 alpha-, 7 alpha-, and 12 alpha-positions. Resolutions of all bile alcohols were better on CP-Sil-19 CB columns; however, we hope that the gas-liquid chromatographic characteristics on the two columns will be useful for better identification of bile alcohols in biological fluids. PMID:1402407

Batta, A K; Aggarwal, S K; Mirchandani, R; Shefer, S; Salen, G

1992-09-01

144

Computational fluid dynamics applied to gas-liquid contactors  

Microsoft Academic Search

In this paper a ‘hierarchy of models’ is discussed to study the fluid dynamic behaviour of gas-liquid bubble columns. This ‘hierarchy of models’ consists of a Eulerian-Eulerian two fluid model, a Eulerian-Lagrangian discrete bubble model and a Volume Tracking or Marker Particle model. These models will be briefly reviewed and their advantages and disadvantages will be highlighted. In addition, a

E. Delnoij; J. A. M. Kuipers; W. P. M. van Swaaij

1997-01-01

145

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

A new project was initiated this quarter to develop gas/liquid membranes for natural gas upgrading. Efforts have concentrated on legal agreements, including alternative field sites. Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50-70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. Kvaerner and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project.

Howard S. Meyer

2002-06-01

146

CFD simulation of gas–liquid contacting in tubular reactors  

Microsoft Academic Search

Gas–liquid contacting in tubular reactors was simulated using an Eulerian–Eulerian CFD approach in which accurate interphase momentum closure relations are incorporated, bubble-induced turbulence is accounted for, and population balance equations are used to describe bubble breakage and coalescence. The ability of two breakup kernels (Luo, H., Svendsen, H.F., 1996. Theoretical model for drop and bubble breakup in turbulent dispersions. A.I.Ch.E.

K. Podila; A. M. Al Taweel; M. Koksal; A. Troshko; Y. P. Gupta

2007-01-01

147

Acoustic probe for solid-gas-liquid suspensions. 1997 annual progress report  

SciTech Connect

'Acoustic probes have shown promise to be quite effective in determining the solid content in solid-liquid suspensions. However, the presence of small amounts of gas in the waste slurries stored in tanks across the DOE complex prevents straightforward application for characterization of these slurries. The proposed research will develop an acoustic probe for monitoring particle size and volume fraction in slurries in the absence and the presence of gas bubbles. Theoretical Analysis Accomplished: Attenuation of sound waves depends on the size distribution of the solids and the volume fraction of solids. These can in principle be calculated from attenuation measured over a range of frequencies. However, small amounts of bubbles distort the measured attenuation. A typical result from theoretical analysis for the attenuation of solid- gas-liquid systems is given in Figure 1. The total attenuation of a sound wave v(o) equals the sum of contributions by a large number of ''bins'' of particle sizes. This notion yields the following equation for the (hitherto) unknown number density of solid particles as a function of particle radius N(a): j k(o,a)N(a)da = v(o), where the kernel k(o,a) is obtained from analysis. If N(a) is given, the above equation is used to calculate the attenuation v(o). This is referred to as solving the ''forward problem''. Solving for N(a) with v(o) given is the ''inverse problem''. A complication that one faces when trying to solve the inverse problem is that the stated problem is mathematically ill-posed, i.e., small fluctuations in v(o) cause large fluctuations in the result for the number density. Therefore the problem needs to be ''regularized'', i.e., the stated problem needs to be changed slightly such as to make it well-posed. This has been done by others for gas-liquid systems in the past. This approach is currently being applied in the present project to solid-liquid systems. As is shown in Figure 2, it successfully recovers the number density that has been used in the forward problem to generate attenuation data. Having this solution technique giving reliable results for the inverse problems of both gas-liquid and solid-liquid systems, the authors shall apply this method in the near future to solid-gas-liquid systems.'

Tavlarides, L.L.; Sangani, A.S.

1997-01-01

148

Evaluation of eight extraction methods and their effects upon total fat and gas liquid chromatographic fatty acid composition analyses of food products  

Microsoft Academic Search

Samples of corn beef hash, frozen turkey pie, frozen beef pie, and beef stew were extracted by eight methods. Methyl esters\\u000a of the fatty acids contained in the extracted fat residue were prepared with BF3-methanol reagent and measured quantitatively by gas liquid chromatography. A 4N HCl digest followed by ethyl ether extraction\\u000a was the most effective extraction method. Total lipid

A. J. Sheppard; W. D. Hubbard; A. R. Prosser

1974-01-01

149

Field gas chromatography-mass spectrometry for fast analysis.  

PubMed

The objective of this presentation is to demonstrate the original device and procedure for fast gas chromatography-mass spectrometry (GC-MS) analysis of gaseous and liquid samples and to discuss its features and capabilities. The concept was developed in order to expand the range of compounds suitable for GC separation and to reduce the time of analysis. Field GC-MS, consisting of original "concentrator-thermodesorber" (CTD) unit, multiple module GC system and compact magnetic mass spectrometer with powerful two-stage vacuum system and multicollector ion detector, is represented. The whole weight of the device is 90 kg. Power consumption is 250 W. The device and analytical procedures allow high speed screening of toxic substances in air and extracts within 100 s per sample. The examples of applications are described, including fast screening of tributyl phosphate (TBP) in air at low ppt level at the rate 1 sample/min. PMID:14698236

Makas, Alexei L; Troshkov, Mikhail L

2004-02-01

150

Modified electrokinetic sample injection method in chromatography and electrophoresis analysis  

SciTech Connect

A sample injection method for horizontal configured multiple chromatography or electrophoresis units, each containing a number of separation/analysis channels, that enables efficient introduction of analyte samples. This method for loading when taken in conjunction with horizontal microchannels allows much reduced sample volumes and a means of sample stacking to greatly reduce the concentration of the sample. This reduction in the amount of sample can lead to great cost savings in sample preparation, particularly in massively parallel applications such as DNA sequencing. The essence of this method is in preparation of the input of the separation channel, the physical sample introduction, and subsequent removal of excess material. By this method, sample volumes of 100 nanoliter to 2 microliters have been used successfully, compared to the typical 5 microliters of sample required by the prior separation/analysis method.

Davidson, J. Courtney (Livermore, CA); Balch, Joseph W. (Livermore, CA)

2001-01-01

151

Serum xylose analysis by gas chromatography/mass spectrometry.  

PubMed

A gas chromatography/mass spectrometric (GC/MS) isotope dilution assay for xylose was developed using tertbutyldimethylsilyl-derivatized xylose and [13C]1xylose, and applied to human serum samples. A calibration curve in serum using this assay showed < 3% variation (< 10 mg/L) for any given point. The correlation coefficient for xylose measurements made on 27 sera between a colorimetric method performed by a national commercial reference laboratory and the GC/MS method developed here was .952. However, xylose determinations of 10 of 27 samples differed by > 10% (up to 150 mg/L) when colorimetric values were compared to GC/MS. Two of these samples had borderline-low xylose values by GC/MS, but were well within the normal range by colorimetric analysis. gas chromatography/mass spectrometric isotope dilution assay appears to be an accurate method to measure xylose in serum. These data also suggest that further prospective studies comparing GC/MS to colorimetric methods are indicated for subjects undergoing oral xylose testing. PMID:7942623

Deutsch, J C; Kolli, V R; Santhosh-Kumar, C R; Kolhouse, J F

1994-11-01

152

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50-70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. Kvaerner and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project. Efforts this quarter have concentrated on legal agreements, including alternative field sites. Preliminary design of the bench-scale equipment continues.

Howard S. Meyer

2003-01-01

153

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

Efforts this quarter have concentrated on legal agreements, including alternative field sites. Preliminary design of the bench-scale equipment continues. Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50--70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. Kvaerner and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project.

Howard S. Meyer

2002-06-30

154

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

Efforts this quarter have concentrated on legal agreements, including alternative field sites. Preliminary design of the bench-scale equipment has been initiated. Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50--70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. Kvaerner and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project.

Howard S. Meyer

2002-06-01

155

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50-70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. KPS and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project. Efforts this quarter have concentrated on legal agreements, including alternative field sites. Preliminary design of the bench-scale equipment continues.

Howard S. Meyer

2002-10-01

156

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50-70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. KPS and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project. Efforts this quarter have concentrated on field site selection. ChevronTexaco has nominated their Headlee Gas Plant in Odessa, TX for a commercial-scale dehydration test. Potting and module materials testing were initiated. Preliminary design of the bench-scale equipment continues.

Howard S. Meyer

2003-04-01

157

Energy transfer at gas-liquid interface: Towards energetic materials  

NASA Astrophysics Data System (ADS)

Physicochemical surface processes have great importance in the different fields of everyday life and science. Computational characterization of collisional energy transfer at a gas-liquid interface is a helpful tool to interpret recent experimental studies and to yield insight into the energy feedback mechanism of multiphase combustion problems. As a first step, a simple Lennard-Jones system was used to investigate the dependence of the collisional energy transfer and the gas atom trapping probabilities on the temperature of the bulk liquid, on the gas/liquid particle mass ratios, on the incident angle of the impinging projectile, and on the gas-liquid interaction strength. We find in accord with the experimental results that the kinematic effects dominate the energy transfer dynamics, but the importance of the role of surface roughening as the temperature of the liquid increases is also seen. The second system, nitromethane was chosen to extend the range of simulations. It is a molecular model system, representing nitramine-type energetic materials. Having had a good potential description for the nitromethane molecule including all internal degrees of freedom, we generated simplified molecular systems based on the original nitromethane model to isolate particular features of the dynamics. We have investigated the effect of the initial incident energy, of the inclusion of the internal degrees of freedom, of the initial incident kinetic energy and of the gas-surface interaction strength. The incorporation of internal degrees of freedom enhanced the collisional energy transfer. These calculations also point to the importance of simple kinematics as it predicts the increase of the ratio of energy transferred with increased initial incident energy of the gas particle.

Szabo, Tamas

158

Direct analysis of mannitol, lactulose and glucose in urine samples by high-performance anion-exchange chromatography with pulse amperometric detection clinical evaluation of intestinal permeability in human immunodeficiency virus infection  

Microsoft Academic Search

Clinically, the ratio of lactulose\\/mannitol excretion in urine after administration of these non-metabolized sugars has been used to evaluate the extent of malabsorption and intestinal permeability disruption in several infections and nutritional diseases, including human immunodeficiency virus (HIV) infection. A range of methodologies have been reported to determine the lactulose\\/mannitol ratio, including enzymatic assay, gas-liquid chromatography (GC), thin-layer chromatography (TLC)

Yongde Bao; Terezinha M. J. Silva; Richard L. Guerrant; Aldo A. M. Lima; Jay W. Fox

1996-01-01

159

Investigation on hydrodynamics and mass transfer characteristics of a gas-liquid ejector using three-dimensional CFD modeling  

Microsoft Academic Search

An investigation of the gas-liquid ejector has been carried out to study the influence of operating conditions and ejector\\u000a geometries on the hydrodynamics and mass transfer characteristics of the ejector by using three-dimensional CFD modeling.\\u000a The CFD results were validated with experimental data. Flow field analysis and prediction of ejector performance were also\\u000a conducted. Variations of the operating conditions were

Tony Utomo; Zhenhua Jin; MSq Rahman; Hyomin Jeong; Hanshik Chung

2008-01-01

160

Vibration-Induced Gas-Liquid Interface Breakup  

NASA Astrophysics Data System (ADS)

Gas-liquid interfaces can be forced to break up when subjected to vibrations within critical ranges of frequency and amplitude. This breakup mechanism was examined experimentally using deep layers of silicone oils over a range of viscosity and sinusoidal, primarily axial vibration conditions that can produce dramatic disturbances at the gas-liquid free surface. Although small-amplitude vibrations produce standing Faraday waves, large-amplitude vibrations produce liquid jets into the gas, droplets pinching off from the jets, gas cavities in the liquid from droplet impact, and bubble transport below the interface. Experiments used several different silicone oils over a range of pressures and vibration conditions. Computational simulations exhibiting similar behavior will be included in the presentation. Applications include liquid fuel rockets, inertial sensing devices, moving vehicles, mixing processes, and acoustic excitation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

O'Hern, Timothy; Torczynski, John; Romero, Ed; Shelden, Bion

2010-11-01

161

Gas–liquid mass transfer in an up-flow cocurrent packed-bed biofilm reactor  

Microsoft Academic Search

Gas–liquid mass transfer was investigated in an up-flow cocurrent packed-bed biofilm reactor. In aerobic processes gas–liquid mass transfer can be considered as a key operational parameter as well as in reactor scale-up. The present paper investigates the influence of the liquid phase mixing in the determination of the volumetric gas–liquid mass transfer coefficient (kLa) coefficient. Residence time distribution (RTD) experiments

Julio Pérez; José Luis Montesinos; Francesc Gòdia

2006-01-01

162

Analysis of soybean lecithin by thin layer and analytical liquid chromatography  

Microsoft Academic Search

The application of thin layer and analytical liquid chromatography to the analysis of two samples of commercial soybean lecithins\\u000a is described. A combination of column chromatography and quantitative thin layer chromatography showed that these products\\u000a consisted of ca. 82% mixture of the major phospholipids of soybeans, phosphatidyl choline, phosphatidyl ethanolamine, and\\u000a phosphatidyl inositol. The remainder of these products contained essentially

W. L. Erdahl; A. Stolyhwo; O. S. Privett

1973-01-01

163

Microemulsion electrokinetic chromatography for analysis of phthalates in soft drinks.  

PubMed

Microemulsion electrokinetic chromatography (MEEKC) is proposed for analysis of di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) in soft drinks. However, the instability of microemulsion is a critical issue. In this research, a novel material, Pluronic® F-127, which has the properties of polymer and surfactant, was added for stabilizing the microemulsion in the MEEKC system. Our data demonstrate that the presence of Pluronic® F-127 (0.05-0.30%) also helps enhance resolution of highly hydrophobic compounds, DBP and DEHP. The electrokinetic injection of sodium dodecyl sulphate (SDS) including sample (-10kV, 20s) was introduced in this MEEKC system and this yielded about 25-fold sensitivity enhancement compared with hydrodynamic injection (1psi, 10s). During method validation, calibration curves were linear (r?0.99), within a range of 75-500ng/mL for DBP and 150-1000ng/mL for DEHP. As the precision and accuracy assays, absolute values of relative standard deviation (RSD) and relative error (RE) in intraday (n=3) and interday (n=5) observations were less than 4.93%. This method was further applied for analyzing six commercial soft drinks and one was found containing 453.67ng/mL of DEHP. This method is considered feasible for serving as a tool for analysis of highly hydrophobic molecules. PMID:23993511

Hsieh, Sung-Yu; Wang, Chun-Chi; Wu, Shou-Mei

2013-06-15

164

The Use of Gas Chromatography for Biogas Analysis  

NASA Astrophysics Data System (ADS)

Energy from natural gas accounts for 24 percent of energy consumed in the US. Natural gas is a robust form of energy which is rich in methane content and is low in impurities. This quality suggests that it is a very clean and safe gas; it can be used in providing heat, a source for cooking, and in powering vehicles. The downside is that it is a non-renewable resource. On the contrary, methane rich gas that is produced by the breakdown of organic material in an anaerobic environment, called biogas, is a renewable energy source. This research focuses on the gas analysis portion of the creation of the anaerobic digestion and verification laboratory where content and forensic analysis of biogas is performed. Gas Chromatography is implemented as the optimal analytical tool for quantifying the components of the biogas including methane, carbon dioxide, hydrogen sulfide and siloxanes. In addition, the problems associated with the undesirable components are discussed. Anaerobic digestion of primary sludge has consistently produced about 55 percent methane; future goals of this research include studying different substrates to increase the methane yield and decrease levels of impurities in the gas.

Andersen, Amanda; Seeley, John; Aurandt, Jennifer

2010-04-01

165

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50-70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. Kvaerner and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project. Efforts this quarter have concentrated on field site selection. ChevronTexaco has nominated their Headlee Gas Plant in Odessa, TX for a commercial-scale dehydration test. Design and cost estimation for this new site are underway. A HazOp review was conducted. Potting and module materials testing continued. Preliminary design of the bench-scale equipment continues. A status meeting was held in Morgantown, WV with the DOE Project Manager.

Howard S. Meyer

2003-10-01

166

GAS/LIQUID MEMBRANES FOR NATURAL GAS UPGRADING  

SciTech Connect

Gas Technology Institute (GTI) is conducting this research program whose objective is to develop gas/liquid membranes for natural gas upgrading to assist DOE in achieving their goal of developing novel methods of upgrading low quality natural gas to meet pipeline specifications. Kvaerner Process Systems (KPS) and W. L. Gore & Associates (GORE) gas/liquid membrane contactors are based on expanded polytetrafluoroethylene (ePTFE) membranes acting as the contacting barrier between the contaminated gas stream and the absorbing liquid. These resilient membranes provide much greater surface area for transfer than other tower internals, with packing densities five to ten times greater, resulting in equipment 50-70% smaller and lower weight for the same treating service. The scope of the research program is to (1) build and install a laboratory- and a field-scale gas/liquid membrane absorber; (2) operate the units with a low quality natural gas feed stream for sufficient time to verify the simulation model of the contactors and to project membrane life in this severe service; and (3) conducted an economic evaluation, based on the data, to quantify the impact of the technology. Chevron, one of the major producers of natural gas, has offered to host the test at a gas treating plant. KPS will use their position as a recognized leader in the construction of commercial amine plants for building the unit along with GORE providing the membranes. GTI will provide operator and data collection support during lab- and field-testing to assure proper analytical procedures are used. Kvaerner and GTI will perform the final economic evaluation. GTI will provide project management and be responsible for reporting and interactions with DOE on this project. Efforts this quarter have concentrated on field site selection. ChevronTexaco has nominated their Headlee Gas Plant in Odessa, TX for a commercial-scale dehydration test. Design and cost estimation for this new site are underway. Potting and module materials testing continued. Preliminary design of the bench-scale equipment continues.

Howard S. Meyer

2003-07-01

167

Application of hydrophilic interaction chromatography for the analysis of polar contaminants in food and environmental samples  

Microsoft Academic Search

For the analysis of highly hydrophilic and polar compounds, Hydrophilic Interaction Chromatography (HILIC) has been established as a valuable complementary approach to reversed-phase liquid chromatography (RPLC). Moreover, the use of mobile phases with a high percentage of organic solvent in HILIC separation is beneficial for mass spectrometric (MS) detection, because of enhanced ionization which results in an increased sensitivity. In

Alexander L. N. van Nuijs; Isabela Tarcomnicu; Adrian Covaci

2011-01-01

168

Quantum gas-liquid condensation in an attractive Bose gas  

SciTech Connect

Gas-liquid condensation (GLC) in an attractive Bose gas is studied on the basis of statistical mechanics. Using some results in combinatorial mathematics, the following are derived. (1) With decreasing temperature, the Bose-statistical coherence grows in the many-body wave function, which gives rise to the divergence of the grand partition function prior to Bose-Einstein condensation. It is a quantum-mechanical analogue to the GLC in a classical gas (quantum GLC). (2) This GLC is triggered by the bosons with zero momentum. Compared with the classical GLC, an incomparably weaker attractive force creates it. For the system showing the quantum GLC, we discuss a cold helium 4 gas at sufficiently low pressure.

Koh, Shun-ichiro [Physics Division, Faculty of Education, Kochi University, Akebono-cho, 2-5-1, Kochi 780 (Japan)

2005-07-01

169

Dual-channel microreactor for gas-liquid syntheses.  

PubMed

A microreactor consisting of two microfluidic channels that are separated by a thin membrane is devised for intimate contact between gas and liquid phases. Gas flowing in one microchannel can diffuse into the liquid flowing in the other microchannel through the thin membrane. An oxidative Heck reaction carried out in the dual-channel (DC) microreactor, in which gaseous oxygen plays a key role in the catalytic reaction, shows the significant improvement that can be made over the traditional batch reactor and the conventional segmental microreactor in terms of yield, selectivity, and reaction time. It also allows independent control of the flow of the gaseous reagent. The proposed DC microreactor should prove to be a powerful tool for fully exploring gas-liquid microchemistry. PMID:20593807

Park, Chan Pil; Kim, Dong-Pyo

2010-07-28

170

CARBON DIOXIDE SEPARATION BY PHASE ENHANCED GAS-LIQUID ABSORPTION  

SciTech Connect

A new process called phase enhanced gas-liquid absorption has been developed in its early stage. It was found that adding another phase into the absorption system of gas/aqueous phase could enhance the absorption rate. A system with three phases was studied. In the system, gas phase was carbon dioxide. Two liquid phases were used. One was organic phase. Another was aqueous phase. By addition of organic phase into the absorption system of CO{sub 2}-aqueous phase, the absorption rate of CO{sub 2} was increased significantly. CO{sub 2} finally accumulated into aqueous phase. The experimental results proved that (1) Absorption rate of carbon dioxide was enhanced by adding organic phase into gas aqueous phase system; (2) Organic phase played the role of transportation of gas solute (CO{sub 2}). Carbon dioxide finally accumulated into aqueous phase.

Liang Hu; Adeyinka A. Adeyiga

2004-05-01

171

CARBON DIOXIDE SEPARATION BY PHASE ENHANCED GAS-LIQUID ABSORPTION  

SciTech Connect

A new process called phase enhanced gas-liquid absorption has been developed in its early stage. It was found that adding another phase into the absorption system of gas/aqueous phase could enhance the absorption rate. A system with three phases was studied. In the system, gas phase was carbon dioxide. Two liquid phases were used. One was organic phase. Another was aqueous phase. By addition of organic phase into the absorption system of CO{sub 2}-aqueous phase, the absorption rate of CO{sub 2} was increased significantly. CO{sub 2} finally accumulated into aqueous phase. The experimental results proved that (1) Absorption rate of carbon dioxide was enhanced by adding organic phase into gas aqueous phase system; (2) Organic phase played the role of transportation of gas solute (CO{sub 2}). Carbon dioxide finally accumulated into aqueous phase.

Liang Hu

2004-09-30

172

Analysis of moniliformin in maize plants using hydrophilic interaction chromatography.  

PubMed

A novel HPLC method was developed for detection of the Fusarium mycotoxin, moniliformin in whole maize plants. The method is based on hydrophilic interaction chromatography (HILIC) on a ZIC zwitterion column combined with diode array detection and negative electrospray mass spectrometry (ESI(-)-MS). Samples were extracted using acetonitrile-water (85:15), and the extracts were cleaned up on strong anion exchange columns. By this procedure we obtained a recovery rate of 57-74% moniliformin with a limit of detection at 48 ng/g and a limit of quantification at 96 ng/g using UV detection at 229 nm, which is comparable to current methods used. Limit of detection and quantification using ESI(-)-MS detection was 1 and 12 ng/g, respectively. Screening of maize samples infected with the moniliformin producing fungi F. avenaceum, F. tricinctum, or F. subglutinans detected moniliformin levels of 1-12 ng/g in 15 of 28 samples using ESI(-)-MS detection. To our knowledge this is the first example of HILIC separation in mycotoxin analysis. PMID:17960879

Sørensen, Jens Laurids; Nielsen, Kristian Fog; Thrane, Ulf

2007-10-26

173

CFD Modeling of Gas-Liquid Flows in Water Electrolysis Units  

Microsoft Academic Search

This paper presents the results of computational fluid dynamics (CFD) modeling of gas - liquid flows in water electrolysis systems. CFD is used as a cost-effective design tool at Stuart Energy Systems Corporation (SESC) to opti mize the performance of different water electrolysis units produced by SESC. General-purpose CFD software is used as a framework for analyzing the gas -liquid

Vladimir AGRANAT; Andrei TCHOUVELEV

174

Flameless atomic absorption (FAA) and gas-liquid chromatographic studies in arsenic bioanalysis.  

PubMed

Procedures for assessment of arsenic in soft tissue by use of flameless atomic absorption (FAA) and gas-liquid chromatography (GLC), have been evolved, with special emphasis on the analytical distinction among inorganic, monomethyl-, and dimethylarsenic in several oxidation states. The chemical bases for such speciation reside in several properties of the arsenicals under consideration: (1) pentavalent inorganic arsenic, methylarsonic, and cacodylic acid are not extracted from tissue matter made strongly acid with hydrochloric acid, while the corresponding trivalent forms (as halides) are extracted; (2) chloroform extracts of samples treated under reducing conditions (HCl-KI) retain organoarsenicals when these extracts are re-extracted with water, but do not when aqueous solutions of oxidants are employed; (3) reduced cacodylate (dimethylarsinous acid) is not detected in the graphite furnace of an FAA unit under conditions selected, while cacodylate can be so detected. For GLC studies, monomethyl- and dimethylarsenic are simultaneously measured as the diethyldithiocarbamate complexes with an instrument equipped for electron-capture detection and containing a glass column packed with silanized 5% OV-17 on Anakrom A.S. PMID:908312

Mushak, P; Dessauer, K; Walls, E L

1977-08-01

175

Supercritical fluid chromatography hyphenated with twin comprehensive two-dimensional gas chromatography for ultimate analysis of middle distillates.  

PubMed

This paper reports the conditions of online hyphenation of supercritical fluid chromatography (SFC) with twin comprehensive two-dimensional gas chromatography (twin-GCxGC) for detailed characterization of middle distillates; this is essential for a better understanding of reactions involved in refining processes. In this configuration, saturated and unsaturated compounds that have been fractionated by SFC are transferred on two different GC x GC columns sets (twin-GCxGC) placed in the same GC oven. Cryogenic focusing is used for transfer of fractions into the first dimension columns before simultaneous GCxGC analysis of both saturated and unsaturated fractions. The benefits of SFC-twin-GC x GC are demonstrated for the extended alkane, iso-alkane, alkene, naphthenes and aromatics analysis (so-called PIONA analysis) of diesel samples which can be achieved in one single injection. For that purpose, saturated and unsaturated compounds have been separated by SFC using a silver loaded silica column prior to GC x GC analysis. Alkenes and naphthenes are quantitatively recovered in the unsaturated and saturated fractions, respectively, allowing their identification in various diesel samples. Thus, resolution between each class of compounds is significantly improved compared to a single GCxGC run, and for the first time, an extended PIONA analysis of diesel samples is presented. PMID:20053407

Adam, Frédérick; Thiébaut, Didier; Bertoncini, Fabrice; Courtiade, Marion; Hennion, Marie-Claire

2009-12-28

176

AN EPA MANUAL FOR ORGANICS ANALYSIS USING GAS CHROMATOGRAPHY-MASS SPECTROMETRY  

EPA Science Inventory

This procedural manual defines the areas of applicability of gas chromatography-mass spectrometry in environmental analysis. The manual includes sample preparation methods specifically adapted to this measurement technique, data processing and interpretation methods, quality cont...

177

Comprehensive Two-Dimensional Gas Chromatography and Chemometrics for the Analysis of Complex Mixtures.  

National Technical Information Service (NTIS)

The main goal of this dissertation is to enhance the analysis capabilities of comprehensive two-dimensional (2-D) gas chromatography (GC x GC) by applying chemometrics to extract component signals in the presence of significant interference, noise, or bot...

C. G. Fraga

2000-01-01

178

VACUUM DISTILLATION COUPLED WITH GAS CHROMATOGRAPHY/MASS SPECTROMETRY FOR THE ANALYSIS OF ENVIRONMENTAL SAMPLES  

EPA Science Inventory

A procedure is presented that uses a vacuum distillation/gas chromatography/mass spectrometry system for analysis of problematic matrices of volatile organic compounds. The procedure compensates for matrix effects and provides both analytical results and confidence intervals from...

179

40 CFR Table Mm-1 to Subpart Mm of... - Default Factors for Petroleum Products and Natural Gas Liquids 1 2  

Code of Federal Regulations, 2011 CFR

...for Petroleum Products and Natural Gas Liquids 1 2 MM Table MM-1 to Subpart MM...for Petroleum Products and Natural Gas Liquids 1 2 Products Column A: density...Other Petroleum Products and Natural Gas Liquids Aviation Gasoline 0.1120...

2011-07-01

180

Structural analysis of amorphous phosphates using high performance liquid chromatography  

Microsoft Academic Search

Determining the atomic-scale structure of amorphous solids has proven to be a formidable scientific and technological problem for the past 100 years. The technique of high-performance liquid chromatography (HPLC) provides unique detailed information regarding the structure of partially disordered or amorphous phosphate solids. Applications of the experimental technique of HPLC to phosphate solids are reviewed, and examples of the type

B. C. Sales; L. A. Boatner; B. C. Chakoumakos; J. C. McCallum; J. O. Ramey; R. A. Zuhr

1993-01-01

181

Analysis of Acetylsalicylic Acid and Its Metabolites by Liquid Chromatography  

Microsoft Academic Search

The salicylates are the most commonly used analgesic, antipyretic and anti-inflammatory drugs. Measurement of serum levels of salicylate is important not only in the diagnosis and management of patients poisoned with salicylate, but also in therapeutic drug monitoring of arthritic patients on high dose salicylate therapy. While high performance liquid chromatography (HPLC) assays for these routine clinical measurements offer no

Tai C. Kwong

1987-01-01

182

Analysis of carbohydrates by anion exchange chromatography and mass spectrometry  

Microsoft Academic Search

A versatile liquid chromatographic platform has been developed for analysing underivatized carbohydrates using high performance anion exchange chromatography (HPAEC) followed by an inert PEEK splitter that splits the effluent to the integrated pulsed amperometric detector (IPAD) and to an on-line single quadrupole mass spectrometer (MS). Common eluents for HPAEC such as sodium hydroxide and sodium acetate are beneficial for the

Cees Bruggink; Rolf Maurer; Heiko Herrmann; Silvano Cavalli; Frank Hoefler

2005-01-01

183

ANALYSIS OF ELECTROLESS NICKEL SOLUTIONS BY ANION CHROMATOGRAPHY  

EPA Science Inventory

The principal appeal of ion chromatography (IC) as analytical technique lies in the ability to rapidly analyze a mixture of ions of widely varying concentrations and properties in a single elution. It is therefore not surprising that IC has been hampered by the similar ion exchan...

184

Qualitative Analysis of Steelworks Materials by Thin Layer Chromatography.  

National Technical Information Service (NTIS)

A published scheme for the identification of cations by thin layer chromatography has been modified to produce a simpler operating procedure. Fifteen cations, viz., Fe, Sn, Cd, Zn, Co, Cu, Mn, V, Pb, Cr, Al, Ca, Mg, Ti and Ni may be detected in a variety ...

H. J. Boniface R. O'Leary R. H. Jenkins

1972-01-01

185

Venera 12 analysis of Venus atmospheric composition by gas chromatography  

Microsoft Academic Search

The Venera 12 descent probe gas-chromatography experiment is described. Eight chemical analyses of the Venus atmosphere were performed, extending from 42-km height to the planet surface. The concentrations measured are: Nâ, (2.5 +- 0.5) % by volume; Ar, 40 +- 20 ppm; CO, 28 +- 14 ppm; SOâ, 130 +- 60 ppm. Upper limits estimated include: Oâ, <20 ppm; HâO,

B. G. Gelman; V. G. Zolotukhin; N. I. Lamonov; B. V. Levchuk; L. M. Mukhin; D. F. Nenarokov; B. P. Okhotnikov; V. A. Rotin; A. I. Lipatov

1979-01-01

186

Evaluation of generic chiral liquid chromatography screens for pharmaceutical analysis  

Microsoft Academic Search

Two different automated generic liquid chromatography screens for the separation of chiral compounds of pharmaceutical interest have been evaluated. The test set comprised 53 chemically diverse chiral compounds involving 55 enantiomeric pairs from the pharmaceutical industry (i.e. starting materials, synthetic intermediates and drug substances). The first screen utilised four polysaccharide-based columns with five mobile phases and showed enantioselectivity for 87%

Margareta E Andersson; David Aslan; Adrian Clarke; Johan Roeraade; Gunnar Hagman

2003-01-01

187

Evolution of flow disturbances in cocurrent gas-liquid flows  

SciTech Connect

Studies of interfacial waves in horizontal gas-liquid flows, close to neutral stability, suggest that the rate of evolution of the interface may be linked to nonlinear interactions between the fundamental mode and the subharmonic -- even if the subharmonic is linearly stable. The rate of evolution increases as the subharmonic becomes more unstable. A comparison of linear stability techniques used to predict the initial behavior of waves reveals similar predictions of growth rates and almost identical speeds between a two layer laminar Orr-Sommerfeld theory and an Orr-Sommerfeld theory when the effect of the (turbulent) gas flow enters as boundary conditions on the liquid layer. However, there is disagreement at small wavenumbers as to the point at which the growth curve crosses 0. This is a significant problem because longwave disturbances, in our case roll waves, form by growth of (initially) small amplitude waves that have frequencies which are 0.5 to 1 Hz, which is in the range where the two theories disagree about the sign of the growth rate. While nonlinear effects are probably involved in the formation of the peak (at least while its amplitude is small), the linear growth rate must play an important role when the amplitude is small.

McCready, M.J.

1992-10-01

188

A systematic analysis of alkaloids by thin layer chromatography  

NASA Astrophysics Data System (ADS)

Fifty-four alkaloids previously divided into four groups on the basis of their behavior in solvents of different compositions using paper chromatography, were subdivided into two groups by thin paper chromatography. The behavior of the alkaloids in different support layers (silica gel, aluminum oxide alkaline, and diatomite G) was examined. It was found that the maximum amount of coating that can be developed without tailing came to a few milligrams on the silica gel plates, a few tenths of a milligram on aluminum oxide, and generally only 25 mg to 50 mg on inactive diatomite plates. The alkaloids could be adequately distinguished from one another by the spraying reagent ince not only color differences but also color changes could be seen during and after spraying. The coloring of the alkaloids by iodine plateate reagent was also determined by the concentration of the alkaloid used. The edge was often a different color from the center.

Waldi, D.

1982-12-01

189

Qualitative analysis of mycotoxins using micellar electrokinetic capillary chromatography  

Microsoft Academic Search

Naturally occurring mycotoxins are separated using micellar electrokinetic capillary chromatography. Trends in the retention of these toxins, resulting from changes in mobile-phase composition and pH, are reported and presented as a means of alleviating coelution problems. Two sets of mobile-phase conditions are determined that provide unique separation selectivity. The facile manner by which mobile-phase conditions can be altered, without changes

Ricky D. Holland; Michael J. Sepaniak

1993-01-01

190

Rapid qualitative analysis of metallic alloys by electrospot chromatography  

Microsoft Academic Search

Summary  Electrography and paper chromatography were combined to analyse rapidly metallic alloys in an almost non destructive technique. Using anodic dissolution the sample is applied on the start point of the chromatographic paper. Known ketones-HCl-water mixtures are usually used as solvents to analyse electrospots of different alloys and metal coatings and a separate electrospottest is recommended for Cr. Results of qualitative

João A. Medeiros; R. N. Damasceno

1979-01-01

191

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2006 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2004, as well as production volumes for the United States and selected States and State subdivisions for the year 2006

Information Center

2007-12-31

192

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2003 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2003, as well as production volumes for the United States and selected States and State subdivisions for the year 2003.

Rafi Zeinalpour

2004-11-01

193

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 1994 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1994, as well as production volumes for the United States and selected States and State subdivisions for the year 1994.

Rafi Zeinalpour

1995-10-01

194

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 1996 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1996, as well as production volumes for the United States and selected States and State subdivisions for the year 1996.

Rafi Zeinalpour

1997-11-01

195

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2002 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2002, as well as production volumes for the United States and selected States and State subdivisions for the year 2002.

Rafi Zeinalpour

2003-12-01

196

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 1999 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1999, as well as production volumes for the United States and selected States and State subdivisions for the year 1999.

Rafi Zeinalpour

2000-12-01

197

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 1993 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1993, as well as production volumes for the United States and selected States and State subdivisions for the year 1993.

Rafi Zeinalpour

1994-11-01

198

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2004 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2004, as well as production volumes for the United States and selected States and State subdivisions for the year 2004.

Rafi Zeinalpour

2005-11-30

199

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 1998 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1998, as well as production volumes for the United States and selected States and State subdivisions for the year 1998.

Rafi Zeinalpour

1999-12-01

200

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 1997 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1997, as well as production volumes for the United States and selected States and State subdivisions for the year 1997.

Rafi Zeinalpour

1998-12-01

201

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2007 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2004, as well as production volumes for the United States and selected States and State subdivisions for the year 2007

Information Center

2009-02-10

202

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2005 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2004, as well as production volumes for the United States and selected States and State subdivisions for the year 2005

Rafi Zeinalpour

2006-12-05

203

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2000 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2000, as well as production volumes for the United States and selected States and State subdivisions for the year 2000.

Rafi Zeinalpour

2001-12-01

204

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2001 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 2001, as well as production volumes for the United States and selected States and State subdivisions for the year 2001.

Rafi Zeinalpour

2002-11-01

205

U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 1995 Annual Report  

EIA Publications

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1995, as well as production volumes for the United States and selected States and State subdivisions for the year 1995.

Rafi Zeinalpour

1996-11-01

206

Continuous gas/liquid-liquid/liquid flow synthesis of 4-fluoropyrazole derivatives by selective direct fluorination  

PubMed Central

Summary 4-Fluoropyrazole systems may be prepared by a single, sequential telescoped two-step continuous gas/liquid–liquid/liquid flow process from diketone, fluorine gas and hydrazine starting materials.

Breen, Jessica R; Yufit, Dmitrii S; Howard, Judith A K; Fray, Jonathan; Patel, Bhairavi

2011-01-01

207

Modeling of gas-liquid reactors. Isothermal semibatch and continuous stirred tank reactors  

Microsoft Academic Search

A computer code for the simulation of isothermal stirred gas-liquid reactors, both continuous and semibatch, has been developed. The models are constituted of two moduli. The first one describes the diffusion-reaction processes at the gas-liquid interphase, and is based on the film model. This modulus is the same for all reactors. The second one describes the time evolution (semibatch reactor)

Massimo Pisu; Massimo Morbidelli

1998-01-01

208

Ultrasound in gas–liquid systems: Effects on solubility and mass transfer  

Microsoft Academic Search

The effect of ultrasound on the pseudo-solubility of nitrogen in water and on gas–liquid mass transfer kinetics has been investigated in an autoclave reactor equipped with a gas induced impeller. In order to use organic liquids and to investigate the effect of pressure, gas–liquid mass transfer coefficient was calculated from the evolution of autoclave pressure during gas absorption to avoid

F. Laugier; C. Andriantsiferana; A. M. Wilhelm; H. Delmas

2008-01-01

209

Flow characteristics near the nozzle of a bubble column with simultaneous gas-liquid injection  

Microsoft Academic Search

Due to their simplicity of construction which precludes the possibility of blockage, simultaneous gas-liquid injectors and liquid ejectors find application to gas-liquid-solid chemical processes such as coal liquefaction. The gas holdup, bubble rising velocity, and bubble diameter near the nozzle in a bubble column with simultaneous gas and liquid injection were measured using an optical fiber probe. A jet-like spouting

Kiyoshi Idogawa; Takashi Fukuda; Hiroshi Nagaishi; Yosuke Maekawa; Tadatoshi Chiba; Shigeharu Morooka

1994-01-01

210

Contact time during impact of a spherical particle against a plane gas-liquid interface: theory  

Microsoft Academic Search

Bubble-particle impact in flotation is usually approximated to the particle approaching against a plane gas-liquid interface. In this paper we theoretically re-investigate this interaction and deal with its non-linear problems.It is evident that the restoring force is a non-linear ‘mixed’ function of the transition angle and the maximum depth of the deformed gas-liquid interface. This ‘mixed’ expression makes analytical prediction

A. V. Nguyen; H. J. Schulze; H. Stechemesser; G. Zobel

1997-01-01

211

Numerical simulation of the gas-liquid-liquid flow in aluminium reduction cells  

Microsoft Academic Search

Flow field in aluminum reduction cells is very important for the heat transfer, the mass transfer and the moment transfer. The gas-liquid-liquid flow in aluminum reduction cells was studied numerically by ANSYS and CFX. The study indicates that the anode bubbles present as a shallow layer. The bath-metal interface deformation of gas- liquid-liquid three-phase flow model is larger than that

Zhiming Liu; Wangxing Li; Jianhong Yang; Yueyong Wang; Xinping Tang

2011-01-01

212

Analysis of uranium isotope separation by redox chromatography  

SciTech Connect

Uranium isotope separation by redox chromatography is analytically studied. The periodic withdrawal of products and tails and the introduction of natural feed are simulated on the assumption of a square cascade for a uranium adsorption band. The influences on the separative power and the lead time until product withdrawal are investigated by varying the magnitude of the isotope separation factor, uranium band length, tails concentration, and so on. Simulating calculations indicate that using ion-exchange resins to achieve uranium isotope separation requires a very long lead time for the production of highly enriched uranium.

Fujine, S.; Naruse, Y.; Shiba, K.

1983-09-01

213

Analysis of enrichment factor of uranium enrichment by Redox chromatography  

SciTech Connect

Experiments and computer simulation show that the uranium enrichment factor in redox chromatography is determined substantially be electron exchange, isotope adsorption-desorption, and oxidation state adsorption-desorption equilibria. Computer simulation utilizing the theoretical model closely predicts the difference between the value of an enrichment factor derived from the solution equilibrium and that observed in the chromatographic isotope separation, which is attributable to a biased distribution of uranium ions between the solid and liquid phases and a nonequilibrium state in the separation column, thus allowing elucidation of the separation mechanism. A theoretical description of the central role of this enrichment factor in determining plant size and economics is presented.

Muyake, T.; Takeda, K.; Onitsuka, H.; Watanabe, T.

1986-04-01

214

Reliable separation of cis and trans fatty acids by gas liquid chromatography on glass capillary columns  

Microsoft Academic Search

Because of the recent progress in lipid research, the availability of an excellent separation method for fatty acid methyl esters has become more and more important. A speical need exists for a good separation of cis and trans isomers, and of isomers with different positions of double-bonds. This goal was achieved by applying a 50 m glass-capillary column with an

H. Jaeger; H.-U. Klör; G. Blos; H. Ditschuneit

1975-01-01

215

Novel mesogenic polysiloxane solvents for gas-liquid chromatography. [Methylchrysene: isomers; sulfur heteronuclear compounds  

Microsoft Academic Search

The open-tubular column gas-chromatographic properties of a member of a new class of mesogenic polysiloxane (PMMS) phases are described and compared with those of a polymethylphenylsiloxane solvent (SE-52). The former is shown to yield high column efficiency commensurate with its gum-like character, yet concomitant high selectivity for positional isomers of methylchrysenes and for polycyclic aromatic and sulfur heteronuclear compounds. The

H. Finkelmann; R. J. Laub

1982-01-01

216

Squalene in oils determined as squalane by gas—liquid chromatography after hydrogenation of methyl esters  

Microsoft Academic Search

Low levels (?0.1%) of squalene were anticipated in oils from the blubber of the harp seal Phoca groenlandica. The traditional roule of saponification and analytical examination of the total unsaponifiables was unattractive. A method\\u000a developed for squalene in olive oil, reportedly present in the range of 0.3–0.7%, was based on total conversion of the oil\\u000a to methyl ester of fatty

R. G. Ackman; E. J. Macpherson; A. Timmins

2000-01-01

217

Insecticide Residues in Baby Food, Animal Feed, and Vegetables by Gas Liquid Chromatography  

Microsoft Academic Search

India is among a few developing countries where organochlorines are still used for controlling pests due to economic constraints. DDT and HCH are still used for controlling pests of public, health especially malaria vector. The residues of these pesticides are known to find their way into milk and milk products (Mukherjee and Gopal 1992a). In our earlier publication (Mukherjee and

I. Mukherjee; M. Gopal

1996-01-01

218

Novel mesogenic polysiloxane solvents for gas-liquid chromatography. [Methylchrysene: isomers; sulfur heteronuclear compounds  

SciTech Connect

The open-tubular column gas-chromatographic properties of a member of a new class of mesogenic polysiloxane (PMMS) phases are described and compared with those of a polymethylphenylsiloxane solvent (SE-52). The former is shown to yield high column efficiency commensurate with its gum-like character, yet concomitant high selectivity for positional isomers of methylchrysenes and for polycyclic aromatic and sulfur heteronuclear compounds. The nematic/isotropic temperature range of the new phase, 70/sup 0/ to 300/sup 0/ C, exceeds by several factors those of previously-described liquid-crystal stationary solvents, as does its upper useful temperature limit of 300/sup 0/C.

Finkelmann, H.; Laub, R.J.

1982-08-01

219

[Thin-layer chromatography and high-pressure liquid chromatography in mycotoxin analysis].  

PubMed

In a discussion of mycotoxin analysis it is concluded that TLC and HPLC methods mutually support each other by guring the opportunity of corroborating values by a second technique. The DC method is preferred when the samples to be analysed are of variable origin while HPLC is the method of choice when samples are uniform or at least similar. PMID:6720083

Majerus, P; Woller, R

1984-01-01

220

Application of micellar electrokinetic capillary chromatography to the analysis of illicit drug seizures  

Microsoft Academic Search

The application of micellar electrokinetic capillary chromatography (MECC) to the analysis of illicit drug seizures is presented. Areas investigated include general screening and qualitative and, in some instances, quantitative analysis of various drugs, including heroin, opium, cocaine, amphetamines, LSD and anabolic steroids. Due to its high efficiency, high selectivity and general applicability, MECC is well suited for forensic drug analyses.

Ira S. Lurie

1997-01-01

221

Digitally Enhanced Thin-Layer Chromatography: An Inexpensive, New Technique for Qualitative and Quantitative Analysis  

ERIC Educational Resources Information Center

|A study conducted shows that if digital photography is combined with regular thin-layer chromatography (TLC), it could perform highly improved qualitative analysis as well as make accurate quantitative analysis possible for a much lower cost than commercial equipment. The findings suggest that digitally enhanced TLC (DE-TLC) is low-cost and easy…

Hess, Amber Victoria Irish

2007-01-01

222

High pH reversed-phase chromatography with fraction concatenation as an alternative to strong-cation exchange chromatography for two-dimensional proteomic analysis  

PubMed Central

Summary Orthogonal high-resolution separations are critical for attaining improved analytical dynamic range and protein coverage in proteomic measurements. High pH reversed-phase liquid chromatography (RPLC) followed by fraction concatenation affords better peptide analysis than conventional strong-cation exchange (SCX) chromatography applied for the two-dimensional proteomic analysis. For example, concatenated high pH reversed-phase liquid chromatography increased identification for peptides (1.8-fold) and proteins (1.6-fold) in shotgun proteomics analyses of a digested human protein sample. Additional advantages of high pH RPLC with fraction concatenation include improved protein sequence coverage, simplified sample processing, and reduced sample losses, making this an attractive alternative to SCX chromatography in conjunction with the second dimension low pH RPLC for two-dimensional proteomics analyses.

Yang, Feng; Shen, Yufeng; Camp, David G.; Smith, Richard D.

2012-01-01

223

Analysis of phenolic compounds by high performance liquid chromatography and ultra performance liquid chromatography.  

PubMed

Two novel chromatographic methods both based on utilization of sub-2-micron particle columns were developed for the analysis of phenolic compounds in this work. An HPLC system was equipped with C(18) silica-based analytical column (50 mm x 4.6 mm, 1.8 microm) and a UPLC system with ethylene-bridged hybrid C(18) analytical column (100 mm x 2.1 mm, 1.7 microm). In total 34 phenolic substances were divided into groups of phenolic acids, flavonoids, catechins and coumarins and were analysed in sequence using different gradient methods. System suitability test data, including repeatability of retention time and peak area, mean values of asymmetry factor, resolution, peak capacity and the height equivalent of a theoretical plate were determined for each gradient method by 10 replicate injections. The developed methods were applied in the analysis of real samples (grape wines, teas). PMID:18585262

Spácil, Zdenek; Nováková, Lucie; Solich, Petr

2008-03-04

224

Improved gas chromatographic analysis of fatty and resin acid mixtures with special reference to tall oil  

Microsoft Academic Search

and Summary  A gas liquid chromatography system for the analysis of complex mixtures of fatty and resin acids has been developed. On 30–40\\u000a m long, 0.3 mm ID glass capillary columns coated with 1,4-butanediol succinate (BDS) and attaining over 90,000 effective theoretical\\u000a plates, all main fatty and resin acids in wood extractives and various tall oil products can be separated and

B. Holmbom

1977-01-01

225

A continuous film-recirculable drop gas-liquid equilibration device. Measurement of trace gaseous ammonia  

PubMed

A miniature gas-liquid equilibrator or a gas collector, intended as a low-volume interface between a soluble gaseous sample and a liquid phase analyzer or between a liquid phase sample and a detector designed for use with gas samples, is described. This paper addresses the application of the device for the measurement of trace atmospheric ammonia. Gas collection occurs solely by diffusive sampling such that aerosol particles are not collected. The device essentially consists of a tube surrounded externally by a jacket. Gas flows through the jacket and contacts a liquid film flowing on the surface of the tube. The flowing film forms a drop at the tube terminus and is aspirated off through the inner bore of the tube. The collected analyte can be (a) directly sent to an analysis system or (b) preconcentrated on a suitable stationary phase; the preconcentrator effluent can be recycled, if desired. With a fluorometric flow injection analysis system harnessed to measure ammonia with such a collector, the limit of detection (LOD, S/N = 3) for a sample drawn for 18 min at 200 mL/min was 4.5 parts per trillion by volume, with the linear range extending up to 30 parts per billion. PMID:10939382

Genfa; Dasgupta

2000-07-15

226

Evaluation of high-efficiency gas-liquid contactors for natural gas processing. Semi-annual report, April--September 1994  

SciTech Connect

Objective was to ensure reliable supply of high-quality natural gas by reducing the cost of treating subquality natural gas containing H{sub 2}O, CO{sub 2}, H{sub 2}S and/or trace quantities of other gaseous impurities by applying high-efficiency rotating and structured packing gas liquid contactors. The work included analysis of base case residence time, viscosity studies on low pressure rotary contactor system, and surface tension studies on the contactor.

NONE

1994-11-01

227

Comprehensive separation and analysis of alkaloids from Stephania yunnanensis by counter-current chromatography coupled with liquid chromatography tandem mass spectrometry analysis.  

PubMed

The polar compounds such as alkaloid compounds are important bioactive components in traditional Chinese medicines. In present study, a comprehensive method for separation and analysis of polar compounds from the polar fraction of traditional Chinese medicine Stephania yunnanensis was established. Both the major components and minor components were analyzed by counter-current chromatography combined with liquid chromatography tandem mass spectrometry (LC-MS(n)). From 50 mg polar fraction of crude extract, 15.2mg corydine and 4.8 mg stepharine with purities over 90% were successfully separated via a polar solvent system n-butanol: methanol: water (4:1:5, v/v) with 10 mM NaOH as an additive in the lower phase, in one step operation. Their structures were further identified by 1H NMR and FTICR-MS. Besides, three minor components were identified by HPLC-MS(n) based on the fragmentation behavior of the purified compounds. PMID:22041142

Dai, Xiaojing; Hu, Ruilin; Sun, Cuirong; Pan, Yuanjiang

2011-10-14

228

Qualitative analysis of mycotoxins using micellar electrokinetic capillary chromatography  

SciTech Connect

Naturally occurring mycotoxins are separated using micellar electrokinetic capillary chromatography. Trends in the retention of these toxins, resulting from changes in mobile-phase composition and pH, are reported and presented as a means of alleviating coelution problems. Two sets of mobile-phase conditions are determined that provide unique separation selectivity. The facile manner by which mobile-phase conditions can be altered, without changes in instrumental configuration, allowed the acquisition of two distinctive, fully resolved chromatograms of 10 mycotoxins in a period of approximately 45 min. By adjusting retention times, using indigenous or added components in mycotoxin samples as normalization standards, it is possible to obtain coefficients of variation in retention time that average less than 1%. The qualitative capabilities of this methodology are evaluated by separating randomly generated mycotoxin-interferent mixtures. In this study, the utilization of normalized retention times applied to separations obtained with two sets of mobile-phase conditions permitted the identification of all the mycotoxins in five unknown samples without any misidentifications. 24 refs., 3 figs., 2 tabs.

Holland, R.D.; Sepaniak, M.J. (Univ. of Tennessee, Knoxville (United States))

1993-05-01

229

Fundamentals of multiphase, gas-solid and gas-liquid flows in porous media  

NASA Astrophysics Data System (ADS)

This thesis is concerned with fundamentals and applications of multiphase and particulate flows. The study contains three parts covering gas-liquid flows through porous media, gas-solid flows and Chemical-Mechanical Polishing (CMP). A continuum model for multiphase fluid flows through poro-elastic media is developed. It is shown that the present theory leads to the extended Darcy's law and contains, as its special case, Biot's theory of saturated poro-elastic media. The capillary pressure formulation derived from the new model is used and the equation governing the evolution of the saturation and its temporal variation in porous media is derived. The resulting nonlinear diffusion equation is then solved numerically. The results show that the capillary hysteresis occurs when the temporal variation of saturation is included. Application of the developed model to CO2 sequestration is discussed. Computer simulations of dilute Gas-Solid flows in complex geometry regions are studied. A procedure for handling particle trajectory analysis in unstructured grid is developed. Examples of particle transport and removal in human lung and hot-gas cleaning systems are presented. The simulation results for the human lung show that the capture efficiency is affected by the turbulence in the upper three bifurcation airways. Computer simulations of gas-solid flows in hot-gas cleaning for a demonstration scale filtration system is studied in details. Alternative designs of the filter vessel are proposed. The corresponding vessel performance are numerically simulated.

Mazaheri, Ali Reza

230

Stereodynamics in state-resolved scattering at the gas-liquid interface.  

PubMed

Stereodynamics at the gas-liquid interface provides insight into the important physical interactions that directly influence heterogeneous chemistry at the surface and within the bulk liquid. We investigate molecular beam scattering of CO(2) from a liquid perfluoropolyether (PFPE) surface in vacuum [incident energy E(inc) = 10.6(8) kcal/mol, incident angle theta(inc) = 60 degrees] to specifically reveal rotational angular-momentum directions for scattered molecules. Experimentally, internal quantum state populations and M(J) distributions are probed by high-resolution polarization-modulated infrared laser spectroscopy. Analysis of J-state populations reveals dual-channel scattering dynamics characterized by a two-temperature Boltzmann distribution for trapping-desorption and impulsive scattering. In addition, molecular dynamics simulations of CO(2) + fluorinated self-assembled monolayers have been used to model CO(2) + PFPE dynamics. Experimental results and molecular dynamics simulations reveal highly oriented CO(2) distributions that preferentially scatter with "top spin" as a strongly increasing function of J state. PMID:18678907

Perkins, Bradford G; Nesbitt, David J

2008-08-04

231

GAS CHROMATOGRAPHY/MATRIX ISOLATION - INFRARED SPECTROMETRY FOR AIR SAMPLE ANALYSIS  

EPA Science Inventory

This report describes the application of gas chromatography/matrix- solation infrared (GC/MI-IR) spectrometry to the analysIs of environmental air sample extracts. Samples that were analyzed include extracts from woodsmoke-impacted air, XAD-2 blanks, indoor air, and carpet sample...

232

Analysis of alkyl sulfonates and carboxylates using high performance ion chromatography  

Microsoft Academic Search

Summary  A simple and general method for the determination of both C1?C10 alkyl sulfonates and alkyl carboxylates using the same basic methodology, based on High Performance ion Chromatography, using\\u000a relatively simple eluent systems allowing fast analysis with both high sensitivity and accuracy is presented.

H. A. J. M. Bevers; R. Hulst

2000-01-01

233

COMPARATIVE EVALUATION OF GC/MS (GAS CHROMATOGRAPHY/MASS SPECTROMETRY) DATA ANALYSIS PROCESSING  

EPA Science Inventory

Mass spectra obtained by fused silica capillary gas chromatography/mass spectrometry/data system (GC/MS/DS) analysis of mixtures of organic chemicals adsorbed on Tenax GC cartridges was subjected to manual and automated interpretative techniques. Synthetic mixtures (85 chemicals ...

234

Optimised determination of clobazam in human plasma with extraction and high-performance liquid chromatography analysis  

Microsoft Academic Search

The analysis of clobazam by high-performance liquid chromatography and UV detection is described herein. After adding an internal standard, 600 ?l of plasma were extracted under basic conditions onto disposable cartridges packed with celite. The organic extract was then evaporated to dryness and the residue reconstituted in 200 ?l of mobile phase. A 20 ?l aliquot was injected into chromatograph.

A. Bolner; F. Tagliaro; A. Lomeo

2001-01-01

235

Advancement and Application of Gas Chromatography Isotope Ratio Mass Spectrometry Techniques for Atmospheric Trace Gas Analysis  

Microsoft Academic Search

The use of gas chromatography isotope ratio mass spectrometry (GC-IRMS) for compound specific stable isotope analysis is an underutilized technique because of the complexity of the instrumentation and high analytical costs. However stable isotopic data, when coupled with concentration measurements, can provide additional information on a compounds production, transformation, loss, and cycling within the biosphere and atmosphere. A GC-IRMS system

Brian M Giebel

2011-01-01

236

Micellar electrokinetic chromatography as a screening method for the analysis of vanilla flavourings and vanilla extracts  

Microsoft Academic Search

As a general example of the potential use of micellar elektrokinetic chromatography (MEKC) in food analysis, a rapid method for the determination of vanillin and related compounds and possible synthetic additives to vanilla flavourings by MEKC is described as a screening method for quality control. Under optimized conditions, baseline separation of nine vanilla constituents and three possible adulterants is possible

Ulf Bütehorn; Ute Pyell

1996-01-01

237

High Performance Liquid Chromatography of Some Analgesic Compounds: An Instrumental Analysis Experiment.  

ERIC Educational Resources Information Center

Background information, procedures, and results are provided for an experiment demonstrating techniques of solvent selection, gradient elution, pH control, and ion-pairing in the analysis of an analgesic mixture using reversed-phase liquid chromatography on an octadecylsilane column. Although developed using sophisticated/expensive equipment, less…

Haddad, Paul; And Others

1983-01-01

238

Trace analysis in the food and beverage industry by capillary gas chromatography: system performance and maintenance.  

PubMed

Gas chromatography (GC) is the most widely used analytical technique in the food and beverage industry. This paper addresses the problems of sample preparation and system maintenance to ensure the most sensitive, durable, and efficient results for trace analysis by GC in this industry. PMID:3379120

Hayes, M A

1988-04-01

239

Analysis of water in liquid and solid samples by headspace gas chromatography  

Microsoft Academic Search

Equilibrium headspace gas chromatography is applied for the analysis of water in liquid and solid samples which are first dissolved in a water miscible solvent. The preferred quantitation technique is the method of standard addition. A particular problem is the water blank, caused by the humidity of the enclosed air in the headspace vial and by the residual water content

B. Kolb; M. Auer

1990-01-01

240

ANALYSIS OF NITRITE IN NO2 DIFFUSION TUBES USING ION CHROMATOGRAPHY  

EPA Science Inventory

An analytical method was developed for the analysis of the NO2 collected by a passive diffusion controlled atmospheric sampling device. The method measured the total amount of nitrite ion using ion chromatography. The precision obtained under field conditions, defined as twice th...

241

Fingerprint Analysis of Flos carthami and Safflower Yellow Pigments by High?Performance Liquid Chromatography  

Microsoft Academic Search

Fingerprint analysis of Flos carthami and safflower yellow pigments were studied by high?performance liquid chromatography (HPLC). A standardized procedure, including preparing and analyzing samples, was first established by a set of experiments. Then the characteristic HPLC fingerprints of both were established by treating 10 batches of genuine Flos carthami from Nanjiang, Xinjiang, China, with the standardized procedure. In succession, the

Jianye Zhang; Yu Ke; Xingang Yang

2005-01-01

242

Analysis and Identification of Acid-Base Indicator Dyes by Thin-Layer Chromatography  

ERIC Educational Resources Information Center

|Thin-layer chromatography (TLC) is a very simple and effective technique that is used by chemists by different purposes, including the monitoring of the progress of a reaction. TLC can also be easily used for the analysis and identification of various acid-base indicator dyes.|

Clark, Daniel D.

2007-01-01

243

Evaluation of Solubility and the Gas-Liquid Equilibrium Coefficient of High Concentration Gaseous Ozone to Water  

Microsoft Academic Search

Solubility and the gas-liquid equilibrium coefficient of gaseous ozone to water were examined under higher concentrations of supplied gaseous ozone up to 100 mg\\/L. The experimental and modeling approach was employed to evaluate the gas-liquid equilibrium coefficients and mass transfer of ozone. The gas-liquid equilibrium coefficients were evaluated as 0.35, 0.31 and 0.25 (mg\\/L-liquid)\\/(mg\\/L-gas) at 15, 20 and 30 °C,

Tadao Mizuno; Hiroshi Tsuno

2010-01-01

244

Stereospecific analysis of triacyl- sn -glycerols by chiral high-performance liquid chromatography  

Microsoft Academic Search

A method for the stereospecific analysis of triacyl-sn-glycerols by high-performance liquid chromatography (HPLC) on a chiral column is described. Triacyl-sn-glycerols were partially degraded with ethyl magnesium bromide, and the monoacylglycerols produced were separated as 1- and\\u000a 2-monoacylglycerol fractions by thin-layer chromatography on boric acid-impregnated silica gel plates. The 1-monoacylglycerols\\u000a were resolved intosn-1 andsn-3 monoacylglycerol fractions by HPLC on a chiral

Toru Takagi; Yasuhiro Ando

1991-01-01

245

Stereolabile chiral compounds: analysis by dynamic chromatography and stopped-flow methods.  

PubMed

Enantiomerization and diastereomerization reactions of chiral compounds play a major role in all aspects of chemistry spanning a wide bridge from drug development to supramolecular chemistry. Traditionally, these reactions are studied by variable-temperature NMR spectroscopy and chiroptical methods such as polarimetry. However, powerful complimentary methods based on chromatography and electrophoresis have been developed and applied to a variety of stereolabile chiral compounds. This tutorial review explains the principles, applications, and limitations of dynamic chromatography and chromatographic and electrophoretic stopped-flow analysis for the investigation of isomerization reactions of chiral compounds. PMID:15965541

Wolf, Christian

2005-04-25

246

Analysis of carbohydrates by anion exchange chromatography and mass spectrometry.  

PubMed

A versatile liquid chromatographic platform has been developed for analysing underivatized carbohydrates using high performance anion exchange chromatography (HPAEC) followed by an inert PEEK splitter that splits the effluent to the integrated pulsed amperometric detector (IPAD) and to an on-line single quadrupole mass spectrometer (MS). Common eluents for HPAEC such as sodium hydroxide and sodium acetate are beneficial for the amperometric detection but not compatible with electrospray ionisation (ESI). Therefore a membrane-desalting device was installed after the splitter and prior to the ESI interface converting sodium hydroxide into water and sodium acetate into acetic acid. To enhance the sensitivity for the MS detection, 0.5 mmol/l lithium chloride was added after the membrane desalter to form lithium adducts of the carbohydrates. To compare sensitivity of IPAD and MS detection glucose, fructose, and sucrose were used as analytes. A calibration with external standards from 2.5 to 1000 pmole was performed showing a linear range over three orders of magnitude. Minimum detection limits (MDL) with IPAD were determined at 5 pmole levels for glucose to be 0.12 pmole, fructose 0.22 pmole and sucrose 0.11 pmole. With MS detection in the selected ion mode (SIM) the lithium adducts of the carbohydrates were detected obtaining MDL's for glucose of 1.49 pmole, fructose 1.19 pmole, and sucrose 0.36 pmole showing that under these conditions IPAD is 3-10 times more sensitive for those carbohydrates. The applicability of the method was demonstrated analysing carbohydrates in real world samples such as chicory inulin where polyfructans up to a molecular mass of 7000 g/mol were detected as quadrupoly charged lithium adducts. Furthermore mono-, di-, tri-, and oligosaccharides were detected in chicory coffee, honey and beer samples. PMID:16106855

Bruggink, Cees; Maurer, Rolf; Herrmann, Heiko; Cavalli, Silvano; Hoefler, Frank

2005-08-26

247

Dynamic and spectroscopic characteristics of atmospheric gliding arc in gas-liquid two-phase flow  

NASA Astrophysics Data System (ADS)

In this study, an atmospheric alternating-current gliding arc device in gas-liquid two-phase flow has been developed for the purpose of waste water degradation. The dynamic behavior of the gas-liquid gliding arc is investigated through the oscillations of electrical signals, while the spatial evolution of the arc column is analyzed by high speed photography. Different arc breakdown regimes are reported, and the restrike mode is identified as the typical fluctuation characteristic of the hybrid gliding arc in air-water mixture. Optical emission spectroscopy is employed to investigate the active species generated in the gas-liquid plasma. The axial evolution of the OH (309 nm) intensity is determined, while the rotational and vibrational temperatures of the OH are obtained by a comparison between the experimental and simulated spectra. The significant discrepancy between the rotational and translational temperatures has also been discussed.

Tu, X.; Yu, L.; Yan, J. H.; Cen, K. F.; Chéron, B. G.

2009-11-01

248

Measurement of pressure fluctuation in gas-liquid two-phase vortex street  

NASA Astrophysics Data System (ADS)

The pressure fluctuation in the wake is an important parameter to characterize the shedding process of gas-liquid two-phase Karman vortex street. This paper investigated such pressure fluctuations in a horizontal pipe using air and water as the tested fluid media. The dynamic signal representing the pressure fluctuation was acquired by the duct-wall differential pressure method. Results show that in the wake of the gas-liquid two-phase Karman vortex street, the frequency of the pressure fluctuation is linear with the Reynolds number when the volume void fraction is within the range of 18%. Moreover, the mean amplitude of the pressure fluctuation decreases with the volume void fraction, and the mean amplitude is larger at higher water flowrates under the same volume void fraction. These findings contribute to an in-depth understanding of the gas-liquid two-phase Karman vortex street.

Sun, Zhiqiang; Sang, Wenhui; Zhang, Hongjian

2009-02-01

249

Gas-liquid phase separation in oppositely charged colloids: Stability and interfacial tension  

NASA Astrophysics Data System (ADS)

We study the phase behavior and the interfacial tension of the screened Coulomb (Yukawa) restricted primitive model (YRPM) of oppositely charged hard spheres with diameter ? using Monte Carlo simulations. We determine the gas-liquid and gas-solid phase transitions using free energy calculations and grand-canonical Monte Carlo simulations for varying inverse Debye screening length ?. We find that the gas-liquid phase separation is stable for ??<=4, and that the critical temperature decreases upon increasing the screening of the interaction (decreasing the range of the interaction). In addition, we determine the gas-liquid interfacial tension using grand-canonical Monte Carlo simulations. The interfacial tension decreases upon increasing the range of the interaction. In particular, we find that simple scaling can be used to relate the interfacial tension of the YRPM to that of the restricted primitive model, where particles interact with bare Coulomb interactions.

Fortini, Andrea; Hynninen, Antti-Pekka; Dijkstra, Marjolein

2006-09-01

250

Flow characteristics near the nozzle of a bubble column with simultaneous gas-liquid injection  

SciTech Connect

Due to their simplicity of construction which precludes the possibility of blockage, simultaneous gas-liquid injectors and liquid ejectors find application to gas-liquid-solid chemical processes such as coal liquefaction. The gas holdup, bubble rising velocity, and bubble diameter near the nozzle in a bubble column with simultaneous gas and liquid injection were measured using an optical fiber probe. A jet-like spouting flow was formed around the nozzle; the height of the jet was independent of the diameter of the nozzle. Bubbles were formed near the side wall and near the top of the jet, with their radial dispersion increasing with increasing height. Beyond {approximately}88 cm from the nozzle, the radial distribution of the gas holdup was uniform and independent of the axial height. The radial dispersion and bubble diameter varied with the nozzle diameter. The effects of simultaneous gas-liquid injection on bubble formation were similar to those of an increase in the pressure.

Idogawa, Kiyoshi; Fukuda, Takashi; Nagaishi, Hiroshi; Maekawa, Yosuke [Government Industrial Development Lab., Sapporo (Japan). Resources and Energy Technology Dept.; Chiba, Tadatoshi [Hokkaido Univ., Sapporo (Japan); Morooka, Shigeharu [Kyushu Univ., Fukuoka (Japan)

1994-10-01

251

High resolution gas chromatography analysis of rice bran oil  

NASA Astrophysics Data System (ADS)

To assess the nutritional value and safety quality of rice bran oil (RBO) ,fatty acids of RBO from 15 species rice come from Hunan Province were analyzed by high resolution gas chromatography (HRGC). Crude RBOs were extracted by hexane 3-times using a solvent-to-rice bran ratio of 3:1 (w/w) at 40°C and composition of RBOs was analyzed by HRGC. The result showed that main fatty acids of 15 kinds of RBO include myristic acid (C14:0), palmitic acid (C16:0), palmitoleic acid (C16:1), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), linolenic acid (C18:3), arachidic acid (C20:0), arachidonic acid (C20:1). It is strange that arachidonic acid (C20:1) is not listed in Chinese standard of RBO (GB11192-2003), and it exists in our samples of RBO. The average value of linolenic acid in RBOs is 1.6304% (range from 1.2425% to 2.131%), and it showed higher level comparing with Chinese standard that linolenic acid is less than 1.0%. The average value of USFA and SFA are 76.81% (range 75.96% to 82.06% ) and 20.15% (range 13.72% to 23.06%) respectively, and USFA content is close to olive oil (83.75%), peanut oil (81.75%) and soybean oil (85.86%). USFA in Jingyou 13 RBO is the highest content. The ratio of USFA to SFA content is 4:1 (range from 3.32 to 5.98:1). The ratio of SFA: MUFA: PUFA of 15 RBOs is 1: 2.2: 1.8, and ?6/?3 ratio is 21.69 (range from16.54 to 27.28) and it is close to the 26:1 which is reported to be helpful to increase SOD activity. The oleic acid /linoleic acid ratio of 15 RBOs is 1.23:1 (rang from 1.04:1 to 1.42:1). Our data analyzed composition of RBOs from 15 species rice of China and will provide new evidence to revise RBO standard. It also helps us to assess nutritional value of RBOs and identify different RBOs from various species rice and places of origin.

Yu, Fengxiang; Lin, Qinlu; Chen, Xu; Wei, Xiaojun

252

SUPERCRITICAL FLUID CHROMATOGRAPHY FOR HIGH MOLECULAR WEIGHT ORGANIC ANALYSIS  

EPA Science Inventory

The report describes a preliminary application of supercritical fluid mass spectrometry (MS) techniques to the analysis of a middle distillate fuel, an emission particulate extract, and the emission particulates themselves. These techniques include capillary column supercritical ...

253

Rapid chemical profiling of saponins in the flower buds of Panax notoginseng by integrating MCI gel column chromatography and liquid chromatography/mass spectrometry analysis.  

PubMed

The flower buds of Panax notoginseng (Notoginseng flower, FBP) are used as the traditional Chinese medicine San-Qi-Hua. In this study, we conducted column chromatography fractionation and liquid chromatography/mass spectrometry (LC/MS) analysis to comprehensively profile bioactive notoginseng saponins (ginsenosides) in FBP. MCI gel column chromatography allowed separation and enrichment of minor saponins. Electrospray ionization tandem mass spectrometry of [M-H](-) and [M+Na](+) precursor ions of the saponins provided reliable structural information for the sapogenin, and sequence of sugar chains. Confirmed by high-accuracy Q-TOF analysis, 170 notoginseng saponins were characterized from FBP, and 91 of them were reported from Panax species for the first time. The new ginsenosides contain acyl groups on ?-chain, malonyl group at 20-OH, or di-malonyl groups. This study also indicated that the flower buds of P. notoginseng contained more protopanaxadiol-type but less protopanaxatriol-type ginsenosides than the roots. PMID:23561171

Yang, Wen-Zhi; Bo, Tao; Ji, Shuai; Qiao, Xue; Guo, De-An; Ye, Min

2013-01-30

254

TRACE ANALYSIS OF FLUORESCEIN-DERIVATIZED PHENOXY ACID HERBICIDES BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY WITH LASER-INDUCTED FLUORESCENCE DETECTION  

EPA Science Inventory

Micellar electrokinetic chromatography (MEKC) with laser-induced fluorescence (LIF) detection was used for the trace analysis of phenoxy acid herbicides. Capillary electrophoresis (CE) with LIF detection, which has not previously been used for pesticide analysis, overcomes the po...

255

The effect of ?-cyclodextrin on liquid chromatography\\/electrospray-mass spectrometry analysis of hydrophobic drug molecules  

Microsoft Academic Search

Cyclodextrins (CDs) are widely used in the pharmaceutical industry for their capability of improving bioavailability, solubility, or stability of drugs via the formation of soluble inclusion complexes. CDs have also been widely used in various chemical analysis methods. In this work, liquid chromatography\\/electrospray mass spectrometry (LC\\/ESI-MS) analysis for four different drugs (imipramine, desipramine, propranolol, and naproxen) that form inclusion complexes

Li Sun; Julie A. Stenken

2007-01-01

256

The Analysis of Insulin-Related Peptides by Reversed-Phase High-Performance Liquid Chromatography  

Microsoft Academic Search

This paper describes the use of high performance liquid chromatography (HPLC) for the rapid analysis and purification of insulin-related peptides prepared by solid-phase synthetic procedures. Examples include the bovine insulin C-peptide (34–45), the porcine insulin C-peptide (41–53) and the insulin B-chain fragment (22–27). Chromatographic elution systems containing reducing reagents like B-mercaptoethanol allow the direct analysis of insulin reduction products. Similar

M. T. W. Hearn; W. S. Hancock; J. G. R. Hurrell; R. J. Fleming; B. Kemp

1979-01-01

257

A liquid chromatography-tandem mass spectrometry method for fluazifop residue analysis in crops  

Microsoft Academic Search

An LC-MS-MS assay is described for fluazifop residue analysis in crops. The residues are extracted with acidified organic\\u000a solvent, the esters and conjugates are hydrolysed with 6 M hydrochloric acid, then the extracts are cleaned-up by solid phase\\u000a extraction using C2(EC) and Si cartridges in tandem. Quantitative analysis is performed by gradient liquid chromatography coupled to triple quadrupole\\u000a mass spectrometer

Elek Bolygo; Andy Boseley

2000-01-01

258

Second derivative solid surface luminescence analysis of two-component liquid chromatography fractions  

SciTech Connect

A single luminescence method is described in which second derivative solid surface phosphorescence and fluorescence were used for the qualitative analysis of two components in high-performance liquid chromatography (HPLC) fractions. The method was applicable to solvents from both normal and reversed-phase HPLC systems. The approach demonstrates how fluorescence and phosphorescence can be combined at room temperature for qualitative analysis. 5 references, 6 figures.

Dalterio, R.A.; Hurtubise, R.J.

1984-06-01

259

US Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2001 Annual Report  

NSDL National Science Digital Library

A newly updated publication is available from the US Energy Information Administration. The report, entitled "US Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2001 Annual Report," contains national and state estimates of proved reserves of crude oil, natural gas, and natural gas liquids in the United States. The over 170-page document has chapters with titles such as National Summaries, New Reservoir Discoveries in Old Fields, Large Reservoir Declines, Natural Gas Plant Liquids, and Top 100 Oil Fields for 2001. Those interested can download the entire report, individual chapters, appendices, a glossary, and even previous reports for links offered by on the site.

2002-01-01

260

Gas Chromatography  

NSDL National Science Digital Library

This is a website from the US Environmental Protection Agency that explains Gas Chromatography for those interested in environmental analysis. The level of the material assumes some user background in the field.

2011-05-19

261

Polymer Analysis by Liquid Chromatography/Electrospray Ionization Time-of-Flight Mass Spectrometry.  

PubMed

Hyphenation of liquid chromatography (LC) techniques with electrospray ionization (ESI) orthogonal acceleration time-of-flight (oa-TOF) mass spectrometry (MS) provides both MS-based structural information and LC-based quantitative data in polymer analysis. In one experimental setup, three different LC modes are interfaced with MS:? size-exclusion chromatography (SEC/MS), gradient polymer elution chromatography (GPEC/MS), and liquid chromatography at the critical point of adsorption (LCCC/MS). In SEC/MS, both absolute mass calibration of the SEC column based on the polymer itself and determination of monomers and end groups from the mass spectra are achieved. GPEC/MS shows detailed chemical heterogeneity of the polymer and the chemical composition distribution within oligomer groups. In LCCC/MS, the retention behavior is primarily governed by chemical heterogeneities, such as different end group functionalities, and quantitative end group calculations can be easily made. The potential of these methods and the benefit of time-of-flight analyzers in polymer analysis are discussed using SEC/MS of a polydisperse poly(methyl methacrylate) sample, GPEC/MS of dipropoxylated bisphenol A/adipic acid polyester resin, LCCC/MS of alkylated poly(ethylene glycol), and LCCC/MS of terephthalic acid/neopentyl glycol polyester resin. PMID:21662820

Nielen, M W; Buijtenhuijs, F A

1999-05-01

262

Analysis of organic/inorganic analytes in environmental samples by packed capillary chromatography  

SciTech Connect

Recent progress in the development of techniques for packing of high efficiency capillary columns has enabled the concept of unified chromatography to be realised. Packed capillary columns offer the advantages of both packed column (high loading capacity, wide range of stationary phases) and capillary column (speed of analysis, high resolution) techniques to produce a versatile and efficient analytical procedure. For the detailed investigation of fossil fuel and environmental samples the rapid growth of packed capillary chromatography offers the unique opportunity to analyse both organic and inorganic components as the column can be operated in both gas chromatography (GC) and supercritical fluid chromatography (SFC) modes. In this study, the use of packing capillary columns, prepared in-house is investigated for both high pressure GC and SFC using helium and CO{sub 2} as the mobile phase respectively. Several spiked and real world samples have been used to demonstrate the potential of packed capillary columns in the analysis of organic and inorganic analytes in fuel and environmental samples.

Burford, M.D.; Robson, M.M.; Mitchell, S.C. [Univ. of Leeds (United Kingdom)] [and others

1995-12-31

263

Concentration effect in hyaluronan analysis by size exclusion chromatography  

Microsoft Academic Search

The concentration effect in size-exclusion chromatographic analysis of hyaluronans of various relative molecular masses (RMM) has been studied. A critical concentration has been found that is negatively dependent on the hyaluronan molecular mass; the higher the biopolymer molecular mass, the smaller the injected sample where the concentration effect should be taken into account for accurate evaluation of molecular mass distribution.

E. Orviský; L. Šoltés; S. Al Assaf

1994-01-01

264

Computerized rapid analysis of complex mixtures by gas chromatography  

Microsoft Academic Search

A computerized rapid analysis system and its application to two research problems are described. The system uses one central minicomputer to gather analog and digital data from several instruments. Various programs calibrate and convert the data into formatted reports. If desired, this computer sends the report to a more powerful mainframe computer for comparison of different reports and establishment of

Demirgian

1984-01-01

265

Comprehensive three-dimensional gas chromatography with parallel factor analysis.  

PubMed

Development of a comprehensive, three-dimensional gas chromatograph (GC3) instrument is described. The instrument utilizes two six-port diaphragm valves as the interfaces between three, in-series capillary columns housed in a standard Agilent 6890 gas chromatograph fitted with a high data acquisition rate flame ionization detector. The modulation periods for sampling column one by column two and column two by column three are set so that a minimum of three slices (more commonly four or five) are acquired by the subsequent dimension resulting in both comprehensive and quantitative data. A 26-component test mixture and quantitative standards are analyzed using the GC3 instrument. A useful methodology for three-dimensional (3D) data analysis is evaluated, based on the chemometric technique parallel factor analysis (PARAFAC). Since the GC3 instrument produces trilinear data, we are able to use this powerful chemometric technique, which is better known for the analysis of two-dimensional (2D) separations with multichannel detection (e.g., GC x GC-TOFMS) or multiple samples (or replicates) of 2D data. Using PARAFAC, we mathematically separate (deconvolute) the 3D data "volume" for overlapped analytes (i.e., ellipsoids), provided there is sufficient chromatographic resolution in each of the three separation dimensions. Additionally, PARAFAC is applied to quantify analyte standards. For the quantitative analysis, it is demonstrated that PARAFAC may provide a 10-fold improvement in the signal-to-noise ratio relative to a traditional integration method applied to the raw, baseline-corrected data. The GC3 instrument obtains a 3D peak capacity of 3500 at a chromatographic resolution of one in each separation dimension. Furthermore, PARAFAC deconvolution provides a considerable enhancement in the effective 3D peak capacity. PMID:17896828

Watson, Nathanial E; Siegler, W Christopher; Hoggard, Jamin C; Synovec, Robert E

2007-09-27

266

Analysis of antibiotics by liquid chromatography–mass spectrometry  

Microsoft Academic Search

The current status of the application of LC–MS in the analysis of antibiotic and antibacterial compounds is reviewed. The main application area of LC–MS in this field is the confirmation of identity in animal food products for human consumption at maximum residue levels, set by the regulatory authorities. LC–MS is found to play an important role in the determination and

W. M. A Niessen

1998-01-01

267

IMPACT OF GROWING ENVIRONMENT ON CHICKASAW BLACKBERRY (RUBUS L.) AROMA EVALUATED BY GAS CHROMATOGRAPHY OLFACTOMETRY DILUTION ANALYSIS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The aroma extract of Chickasaw blackberry ( RubusL.) was separated with silica gel normal phase chromatography into six fractions. Gas chromatography-olfactometry (GCO) was performed on each fraction to identify aroma active compounds. Aroma extraction dilution analysis (AEDA) was employed to charac...

268

Analysis of cyanobacterial hepatotoxins in water samples by microbore reversed-phase liquid chromatography–electrospray ionisation mass spectrometry  

Microsoft Academic Search

A method based on liquid chromatography coupled to mass spectrometry with positive electrospray ionisation was developed for the analysis of cyanobacterial hepatotoxins in environmental samples. The chromatographic separation was performed using two microbore columns, 2 mm and 1 mm I.D. columns, which allowed the coupling of liquid chromatography to mass spectrometry with no flow splitting. Analytes were eluted using two

Mónica Barco; Josep Rivera; Josep Caixach

2002-01-01

269

Gas and liquid chromatography with inductively coupled plasma mass spectrometry detection for environmental speciation analysis — advances and limitations  

Microsoft Academic Search

Recent advances in the coupling of gas chromatography (GC) and high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP MS) and their role in trace element speciation analysis of environmental materials are presented. The discussion is illustrated with three research examples concerning the following topics: (i) development and coupling of multicapillary microcolumn GC with ICP MS for

Joanna Szpunar; Shona McSheehy; Kasia Po?e?; Véronique Vacchina; Sandra Mounicou; Isaac Rodriguez; Ryszard ?obi?ski

2000-01-01

270

Analysis of radioactive mixed hazardous waste using derivatization gas chromatography/mass spectrometry, liquid chromatography, and liquid chromatography/mass spectrometry  

SciTech Connect

Six samples of core segments from Tank 101-SY were analyzed for chelators, chelator fragments, and several carboxylic acids by derivatization gas chromatography/mass spectrometry. The major components detected were ethylenediaminetetraacetic acid, nitroso-iminodiacetic acid, nitrilotriacetic acid, citric acid, succinic acid, and ethylenediaminetriacetic acid. The chelator of highest concentration was ethylenediaminetetraacetic acid in all six samples analyzed. Liquid chromatography was used to quantitate low molecular weight acids including oxalic, formic, glycolic, and acetic acids, which are present in the waste as acid salts. From 23 to 61% of the total organic carbon in the samples analyzed was accounted for by these acids.

Campbell, J.A.; Lerner, B.D.; Bean, R.M.; Grant, K.E.; Lucke, R.B.; Mong, G.M.; Clauss, S.A.

1994-08-01

271

Approach of the critical point of gas-liquid transitions in an electrostatically stabilized colloidal suspension  

Microsoft Academic Search

We report on the study of the critical point of gas-liquid transitions in an electrostatically stabilized colloidal suspension. Suspensions are constituted of spherical magnetic nanoparticles dispersed in water and stabilized by electrostatic repulsions. The coexistence line is constructed on the Pi-V diagram (Pi: osmotic pressure, Phi: volume fraction) by the determination of transitions' threshold by optical microscopy on a large

F. Cousin; E. Dubois; V. Cabuil

2001-01-01

272

Vertically-Vibrated Gas-Liquid Interfaces: Surface Deformation and Breakup  

Microsoft Academic Search

In his pioneering work of 1831, Faraday demonstrated that a vertically\\u000avibrated gas-liquid interface exhibits a period-doubling bifurcation from a\\u000aflat state to a wavy configuration at certain frequencies or amplitudes.\\u000aTypical experiments performed using thin layers of water produce \\

T. J. O'Hern; E. F. Romero; C. F. Brooks; B. Shelden; J. R. Torczynski; A. M. Kraynik; L. A. Romero; G. L. Benavides

2010-01-01

273

Vertically-Vibrated Gas-Liquid Interfaces: Surface Deformation and Breakup  

Microsoft Academic Search

In his pioneering work of 1831, Faraday demonstrated that a vertically vibrated gas-liquid interface exhibits a period-doubling bifurcation from a flat state to a wavy configuration at certain frequencies or amplitudes. Typical experiments performed using thin layers of water produce \\

T. J. O'Hern; E. F. Romero; C. F. Brooks; B. Shelden; J. R. Torczynski; A. M. Kraynik; L. A. Romero; G. L. Benavides

2010-01-01

274

HOLDUP, INTERFACIAL AREA AND POWER REQUIREMENTS IN TURBINE AGITATED GAS-LIQUID CONTACTORS  

Microsoft Academic Search

This paper reports a detailed study of the hydrodynamic variables involved in the operation of 6-blade (flat) turbine agitated gas-liquid contractors. New information is presented regarding the characteristic velocity of the dispersed gas bubbles. Generalized correlations for prediction of power consumption of impellers under aeration conditions, gas phase holdup, characteristic velocity, mean residence time of gas bubbles, interfacial area of

T. MURUGESAN; T. E. DEGALEESAN

1992-01-01

275

Design of a cyclone separator for the separation of gas-liquid mixtures  

Microsoft Academic Search

A procedure has been developed at the MIKhMe for the design of a hollow cyclone separator with a rectangular tangential inlet of the gas-liquid mixture near the bottom. The procedure is based on the results of theoretical and experimental investigations of the cyclone and allows one to determine the geometrical dimensions and the operating regime of the cyclone which corresponds

A. S. Zhikharev; A. M. Kutepov; V. V. Solov'ev

1985-01-01

276

Efficient Synthesis of Gold Nanoparticles Using Ion Irradiation in Gas--Liquid Interfacial Plasmas  

NASA Astrophysics Data System (ADS)

The efficient synthesis of gold nanoparticles using plasma irradiation in gas--liquid interfacial discharges is carried out. The availability of plasma ion irradiation to an ionic liquid on nanoparticle synthesis was revealed by direct comparison with an electron shower system. It was found that the ion irradiation generated hydrogen radicals in the ionic liquid, which were effective for the synthesis of gold nanoparticles.

Baba, Kazuhiko; Kaneko, Toshiro; Hatakeyama, Rikizo

2009-03-01

277

Control and ultrasonic actuation of a gas liquid interface in a microfluidic chip  

Microsoft Academic Search

This paper describes the design and manufacturing of a microfluidic chip, allowing for the actuation of a gas-liquid interface and of the neighboring fluid. The first way to control the interface motion is to apply a pressure difference across it. In this case, the efficiency of three different micro-geometries at anchoring the interface is compared. Also, the critical pressures needed

Jie Xu; Daniel Attinger

2007-01-01

278

Effect of ejector configuration on hydrodynamic characteristics of gas–liquid ejectors  

Microsoft Academic Search

Ejectors are gas–liquid contactors that are reported to provide higher mass transfer rates than conventional contactors. Detailed experiments were performed and computational fluid dynamics (CFD) modeling studies were undertaken to understand the hydrodynamic characteristics of the ejector geometry. The CFD model provides a basis for quantifying the effects of operating conditions on the ejector performance. CFD studies shows that there

S. Balamurugan; V. G. Gaikar; A. W. Patwardhan

2008-01-01

279

Investigation of entrainment behavior and characteristics of gas–liquid ejectors based on CFD simulation  

Microsoft Academic Search

The aim of this paper is to investigate the entrainment behavior and performance of gas–liquid ejectors. computational fluid dynamics (CFD) model and the corresponding algorithm are developed and validation experiment has been carried out over a wide range of operation conditions for ejector with different configurations. Good agreement has been achieved between the predicted values from CFD simulation and the

C. Li; Y. Z. Li

2011-01-01

280

[Chromatography analysis of tobacco smoke condensate in biology tissue].  

PubMed

Specialized analytical instrumentation for detailed analysis of nicotine, benz(alpha)pyrene, pyridine and benzene in tooth enamel and pulp of inveterate tobacco smokers is created. A Waters PPY-24 liquid chromatograph is equipped with Model M660 solvent programmer and a Model U6K sample injector is used. A Model 440 dual-wavelength detector is used to obtain absorbance ratios on dual-pen recorder. Our data show that concentration of tobacco smoke components in tooth cavity of inveterate tobacco smokers is different. The chisel tooth pulp contained considerably more nicotine and pyridine as compared with molars. The level of benzene does not change analyzed structures. The assumption of linearity between calculation of predicted retention times and concentration has been shown to be valid up to about 8,0% for all studied compounds. PMID:20157203

Zurabashvili, D Z; Chanturia, I R; Kapanadze, L R

2010-01-01

281

Analysis of autoxidized fats by gas chromatography-mass spectrometry: III. Methyl linolenate  

Microsoft Academic Search

The gas chromatography-mass spectrometry (GC-MS) method developed in the preceding papers was extended to the analysis of\\u000a autoxidation products of methyl linolenate. Four isomeric hydroxy allylic trienes with a conjugated diene system were identified\\u000a after reduction of the linolenate hydroperoxides. All eight geometrictrans,cis- andtrans, trans-conjugated diene isomers of these hydroxy allylic compounds were identified and partially separated by GC of

E. N. Frankel; W. E. Neff; W. K. Rohwedder; B. P. S. Khambay; R. F. Garwood

1977-01-01

282

Quantitative analysis of cytokinins in plants by liquid chromatography–single-quadrupole mass spectrometry  

Microsoft Academic Search

A sensitive method for the quantitative analysis of all natural isoprenoid cytokinins in plant material by electrospray single-quadrupole mass spectrometry is presented. A baseline chromatographic separation of 20 non-derivatised naturally occurring cytokinins has been developed. Precise analyses of O-glucoside and ribonucleotide fractions were also performed by the high-performance liquid chromatography–mass spectrometry (HPLC–MS) but run separately from the basic cytokinin metabolites.

Ond?ej Novák; Petr Tarkowski; Danuše Tarkowská; Karel Doležal; René Lenobel; Miroslav Strnad

2003-01-01

283

Direct analysis of several Fusarium mycotoxins in cereals by capillary gas chromatography–mass spectrometry  

Microsoft Academic Search

A method for qualitative and quantitative analysis of Fusarium mycotoxins by gas chromatography–mass spectrometry (GC–MS) using cold on-column injection was improved. Eight typical mycotoxins, including deoxynivalenol (DON), 3-acetyldeoxynivalenol (3ADN), fusarenon-X (FX), diacetoxyscirpenol (DAS), 15-monoacetylscirpenol (15MAS), T-2 toxin (T-2), scirpentriol (SCT), and zearalenone (ZEA) were subjected to GC–MS without chemical derivatization by means of the on-column injection technique. Chromatographic separation of

Yoshiki Onji; Yoshinari Aoki; Naoto Tani; Kiyoshi Umebayashi; Yoshimi Kitada; Yoshiko Dohi

1998-01-01

284

Discrimination of genetically modified poplar clones by analytical pyrolysis–gas chromatography and principal component analysis  

Microsoft Academic Search

Analytical pyrolysis combined with gas chromatography and mass spectrometry (Py-GC–MS) is a relatively rapid (1–3h) method for the investigation of polymers. Various wood tissues from transgenic poplar clones and from control samples have been subjected to a screening test by Py-GC–MS. Pyrolysis products from lignin- and carbohydrate-derived pyrolysis products were subjected to multivariate principal component analysis (PCA). The first three

Dietrich Meier; Ingrid Fortmann; Jürgen Odermatt; Oskar Faix

2005-01-01

285

Blind Analysis of Denaturing High-Performance Liquid Chromatography as a Tool for Mutation Detection  

Microsoft Academic Search

Denaturing high-performance liquid chromatography (DHPLC) is a novel high-capacity technique for detecting new mutations. We have evaluated the sensitivity and specificity of this method in a blind analysis of exon H of the factor IX gene and exon 16 of the neurofibromatosis type 1 gene. Under a single set of conditions for each exon, 55\\/55 individuals carrying 48 unique mutations

Michael C. O'Donovan; Peter J. Oefner; Stacy C. Roberts; Jehannine Austin; Bastiaan Hoogendoorn; Carol Guy; Graham Speight; Meena Upadhyaya; Steve S. Sommer; Peter McGuffin

1998-01-01

286

Matrix effects in pesticide multi-residue analysis by liquid chromatography–mass spectrometry  

Microsoft Academic Search

Three sample preparation methods: Luke method (AOAC 985.22), QuEChERS (quick, easy, cheap, effective, rugged and safe) and matrix solid-phase dispersion (MSPD) were applied to different fruits and vegetables for analysis of 14 pesticide residues by high-performance liquid chromatography with electrospray ionization–mass spectrometry (HPLC\\/ESI\\/MS). Matrix effect, recovery and process efficiency of the sample preparation methods applied to different fruits and vegetables

Anneli Kruve; Allan Künnapas; Koit Herodes; Ivo Leito

2008-01-01

287

Quantitative analysis of monosialogangliosides by hig h-performance liquid chromatography of their perbenzoyl derivatives  

Microsoft Academic Search

A quantitative high-performance liquid chro- matographic method for the analysis of monosialogan- gliosides as their perbenzoyl derivatives has been devised. Samples containing as little as 3 nmol were converted to their perbenzoyl derivatives by reaction with 0.1 ml of 10% benzoyl chloride in pyridine at 60°C for 1 hr. The products were purified by silicic acid chromatography and analyzed by

Eric G. Bremer; Sonja K. Gross; Robert H. McCluer

288

Analysis of 5-hydroxymethylfurfural in foods by gas chromatography–mass spectrometry  

Microsoft Academic Search

A new, simple and selective method for the analysis of 5-hydroxymethylfurfural (HMF) in foods by gas chromatography coupled to mass spectrometry (GC–MS) is proposed. Several derivatising procedures based on the formation of an HMF silylated derivative using different reagents were studied. Among the derivatising reagents examined, N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA) provided the best derivatisation yield. Sample clean-up was also optimised, using either

E. Teixidó; F. J. Santos; L. Puignou; M. T. Galceran

2006-01-01

289

Liquid chromatography multi-stage mass spectrometry for the analysis of 5-hydroxymethylfurfural in foods  

Microsoft Academic Search

A new, simple and selective method for the analysis of 5-hydroxymethylfurfural (HMF) in foods by liquid chromatography coupled to ion trap multi-stage mass spectrometry (LC–MSn) is proposed in the present study. Several chromatographic columns were tested and the best results were obtained using a phenyl fluorinated column. MS conditions were established using an atmospheric pressure chemical ionisation (APCI) source in

Erika Teixidó; Encarnación Moyano; F. Javier Santos; M. Teresa Galceran

2008-01-01

290

Gas chromatography-mass spectrometry methods for structural analysis of fatty acids  

Microsoft Academic Search

Procedures for structural analysis of fatty acids are reviewed. The emphasis is on methods that involve gas chromatography-mass\\u000a spectrometry and, in particular, the use of picolinyl ester and dimethyloxazoline derivatives. These should be considered\\u000a as complementing each other, not simply as alternatives. However, additional derivatization procedures can be of value, including\\u000a hydrogenation and deuteration, and preparation of dimethyl disulfide and

William W. Christie

1998-01-01

291

Determination of Urinary Glucose by a Flow Injection Analysis Amperometric Biosensor and Ion-Exchange Chromatography  

Microsoft Academic Search

A practical biosensor system has been developed for the determination of urinary glucose using a flow-injection analysis (FIA)\\u000a amperometric detector and ion-exchange chromatography. Glucose oxidase was immobilized onto porous aminopropyl glass beads\\u000a via glutaraldehyde activation to form an immobilized enzyme column. On the basis of its negative charge at pH 5.5, endogenous\\u000a urate in urine samples was effectively retained by

K. B. Male; J. H. T. Luong

1992-01-01

292

Analysis of volatile organic compounds in groundwater samples by gas chromatography-mass spectrometry  

SciTech Connect

The Savannah River Site contains approximately 1500 monitoring wells from which groundwater samples are collected. Many of these samples are sent off-site for various analyses, including the determination of trace volatile organic compounds (VOCs). This report describes accomplishments that have been made during the past year which will ultimately allow VOC analysis to be performed on-site using gas chromatography-mass spectrometry. Through the use of the on-site approach, it is expected that there will be a substantial cost savings. This approach will also provide split-sample analysis capability which can serve as a quality control measure for off-site analysis.

Bernhardt, J.

1995-08-23

293

Fundamentals of multiphase, gas-solid and gas-liquid flows in porous media  

NASA Astrophysics Data System (ADS)

This thesis is concerned with fundamentals and applications of multiphase and particulate flows. The study contains three parts covering gas-liquid flows through porous media, gas-solid flows and Chemical-Mechanical Polishing (CMP). A continuum model for multiphase fluid flows through poro-elastic media is developed. It is shown that the present theory leads to the extended Darcy's law and contains, as its special case, Biot's theory of saturated poro-elastic media. The capillary pressure formulation derived from the new model is used and the equation governing the evolution of the saturation and its temporal variation in porous media is derived. The resulting nonlinear diffusion equation is then solved numerically. The results show that the capillary hysteresis occurs when the temporal variation of saturation is included. Application of the developed model to CO2 sequestration is discussed. Computer simulations of dilute Gas-Solid flows in complex geometry regions are studied. A procedure for handling particle trajectory analysis in unstructured grid is developed. Examples of particle transport and removal in human lung and hot-gas cleaning systems are presented. The simulation results for the human lung show that the capture efficiency is affected by the turbulence in the upper three bifurcation airways. Computer simulations of gas-solid flows in hot-gas cleaning for a demonstration scale filtration system is studied in details. Alternative designs of the filter vessel are proposed. The corresponding vessel performance are numerically simulated. Chemical mechanical polishing (CMP) has become critical to the fabrication of advanced multilevel integrated circuit in microelectronic industry. The effect of course surface roughness of abrasive particles on the polishing rate in CMP is studied. The effects of slurry pH and double layer attraction and repulsion on chemical-mechanical polishing are also studied. It is shown that the slurry pH and colloidal forces significantly affect the removal rate in chemical mechanical polishing.

Mazaheri, Ali Reza

294

Solidphase microextraction coupled with gas chromatography and gas chromatography—Mass spectrometry for public health pesticides analysis  

Microsoft Academic Search

Summary  Public health pesticides in two-component mixed solutions were analyzed using solid-phase microextraction (SPME) coupled with\\u000a gas chromatography (GC) and gas chromatography—mass spectrometry (GC-MS). The two-component mixed solutions used were allethrin\\u000a mixed with cyfluthrin, cypermethrin mixed with tetramethrin, and transfluthrin mixed with cyfluthrin. Quantitative SPME-GC\\u000a and SPME-GC-MS analyses using calibration and standard addition methods were evaluated. Using SPME pretreatment saved several

C. BorFuh; Y. C. Yang; H. Y. Tsai; L. S. Ho

2003-01-01

295

Mathematical analysis of frontal affinity chromatography in particle and membrane configurations.  

PubMed

The scaleup and optimization of large-scale affinity-chromatographic operations in the recovery, separation and purification of biochemical components is of major industrial importance. The development of mathematical models to describe affinity-chromatographic processes, and the use of these models in computer programs to predict column performance is an engineering approach that can help to attain these bioprocess engineering tasks successfully. Most affinity-chromatographic separations are operated in the frontal mode, using fixed-bed columns. Purely diffusive and perfusion particles and membrane-based affinity chromatography are among the main commercially available technologies for these separations. For a particular application, a basic understanding of the main similarities and differences between particle and membrane frontal affinity chromatography and how these characteristics are reflected in the transport models is of fundamental relevance. This review presents the basic theoretical considerations used in the development of particle and membrane affinity chromatography models that can be applied in the design and operation of large-scale affinity separations in fixed-bed columns. A transport model for column affinity chromatography that considers column dispersion, particle internal convection, external film resistance, finite kinetic rate, plus macropore and micropore resistances is analyzed as a framework for exploring further the mathematical analysis. Such models provide a general realistic description of almost all practical systems. Specific mathematical models that take into account geometric considerations and transport effects have been developed for both particle and membrane affinity chromatography systems. Some of the most common simplified models, based on linear driving-force (LDF) and equilibrium assumptions, are emphasized. Analytical solutions of the corresponding simplified dimensionless affinity models are presented. Particular methods for estimating the parameters that characterize the mass-transfer and adsorption mechanisms in affinity systems are described. PMID:11694270

Tejeda-Mansir, A; Montesinos, R M; Guzmán, R

2001-10-30

296

High Pressure Liquid Chromatography in the Analysis of Fatty Acid Composition of Oral Streptococci and its Comparison to Gas Chromatography.  

National Technical Information Service (NTIS)

In the bacterial strains used, high pressure liquid chromatography (HPLC) was used to find a C20, C22, and C24 present in approximately equal concentrations. Evidence was found of C21, C23, and C25 acids at about 10% of the C20 concentration. These fatty ...

N. E. Bussell R. A. Miller J. A. Setterstrom A. Gross

1977-01-01

297

One- and comprehensive two-dimensional high-performance liquid chromatography analysis of alkylphenol polyethoxylates.  

PubMed

High-performance liquid chromatography (HPLC) analysis of alkylphenol polyethoxylates (APnEOs) in one-dimensional (1-D) mode usually separates either the ethoxy or alkyl moiety distribution and requires different modes for adequate resolution. Simultaneous complete separation of variable ethoxymer chain lengths and variable alkyl end groups using 1-D-HPLC has not been reported and suggests that multidimensional (MDLC) or comprehensive two-dimensional liquid chromatography (LC×LC) might offer a suitable separation approach for this goal. This study compares different separation modes--normal phase LC (NPLC), reversed-phase LC (RPLC) and hydrophilic interaction chromatography (HILIC)--in terms of separation for alkyl and ethoxy distributions. RPLC provided adequate separation of octyl and nonyl APnEOs using an isocratic elution program and was selected as second dimension ((2)D) for LC×LC. NPLC offered better resolution than HILIC; however, non-polar NPLC solvent immiscibility with RPLC mobile phases leads to HILIC being chosen as first dimension ((1)D). The HILIC×RPLC system was evaluated by analysis of four APnEO mixtures. Complete simultaneous separation of APnEOs into individual oligomers, with each alkyl end group resolved, demonstrated the capability of the LC×LC method. Different descriptors and metrics for assessing system orthogonality were investigated to evaluate HILIC×RPLC performance. A relatively high dimensionality of 1.76 was demonstrated. PMID:22083686

Wu, Ze-ying; Marriott, Philip J

2011-11-14

298

Analysis of positional isomers of hydroxylated aromatic cytokinins by micellar electrokinetic chromatography.  

PubMed

A micellar electrokinetic chromatography (MEKC) method was developed for the separation of six positional isomers of hydroxylated aromatic cytokinins (topolin and topolin riboside), including ortho-topolin, meta-topolin, para-topolin, ortho-topolin riboside, meta-topolin riboside, and para-topolin riboside. Optimum resolution and analysis time (ca. 20 min) for the six aromatic cytokinin standards were achieved with a running buffer at pH 8.0 consisting of 20 mM boric acid, 50 mM sodium dodecyl sulfate (SDS), and 20% v/v methanol. The method has good reproducibility and has been successfully applied to detect the presence of a putative ortho-topolin in coconut water extract sample purified using C(18) and mixed-mode solid-phase extraction (SPE) columns. Other advantages of this MEKC method are short analysis time, low solvent consumption, and separation of positional isomers which could be achieved by a simple aqueous buffer system without the use of expensive chromatographic columns. In addition, a high-performance liquid chromatography (HPLC) method with baseline separation of the six topolin and topolin riboside standards was developed for the confirmation of the endogenous ortho-topolin in coconut water sample. Finally, the presence of ortho-topolin was further confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) based on its characteristic fragmentation pattern. PMID:15800967

Ge, Liya; Yong, Jean Wan Hong; Tan, Swee Ngin; Yang, Xin Hao; Ong, Eng Shi

2005-05-01

299

High pH reversed-phase chromatography with fraction concatenation for 2D proteomic analysis  

SciTech Connect

Orthogonal high-resolution separations are critical for attaining improved analytical dynamic ranges of proteome measurements. Concatenated high pH reversed phase liquid chromatography affords better separations than the strong cation exchange conventionally applied for two-dimensional shotgun proteomic analysis. For example, concatenated high pH reversed phase liquid chromatography increased identification coverage for peptides (e.g., by 1.8-fold) and proteins (e.g., by 1.6-fold) in shotgun proteomics analyses of a digested human protein sample. Additional advantages of concatenated high pH RPLC include improved protein sequence coverage, simplified sample processing, and reduced sample losses, making this an attractive first dimension separation strategy for two-dimensional proteomics analyses.

Yang, Feng; Shen, Yufeng; Camp, David G.; Smith, Richard D.

2012-04-01

300

Quantitative analysis of trimethylsilyl derivative of hydroxyurea in plasma by gas chromatography-mass spectrometry.  

PubMed

Hydroxyurea is an antitumor drug widely used in the treatment of sickle cell disease. The drug has been analyzed in biological fluids by a number of high-performance liquid chromatography (HPLC) methods. This paper describes a fast and highly reliable capillary gas chromatography-mass spectrometry (GC-MS) procedure that was developed for the detection and quantitation of hydroxyurea in plasma. The compound and its labeled internal standard were liquid extracted from plasma and derivatized with BSTFA before analysis. The detection limit of the assay was 0.078 microg/ml and the limit of quantitation was 0.313 microg/ml with linearity up to 500 microg/ml. Intra-day variation, as coefficient of variation (C.V., %) over the selected concentration range, was 0.3-8.7% and inter-day variation was 0.4-9.6%. PMID:16378766

James, Hutchinson; Nahavandi, Masoud; Wyche, Melville Q; Taylor, Robert E

2005-12-27

301

[Gas-liquid chromatographic method of studying the migration into cheese of the volatile components of coatings based on aqueous polymer dispersions].  

PubMed

The Moscow Technological Institute of meat packing and dairy industries has developed in cooperation with a number of branch institutes a technology for obtaining coatings based on aqueous dispersions of BXBD-65 (a copolymer of vinyl and vinylidenchloride) but butyl rubber which posses physico-chemical properties required to ensure biochemical processes attending maturing of the cheese. Gas-liquid chromatography showed that the diffusion of the solvent remnants occurs only in the layer of the cheese in immediate contact with its coating and in amounts below the permissible concentration. At the same time, it was found that vinylchloride was absent both in the coating and in the cheese enclosed in the coating. PMID:664553

Tarasova, N A; Snezhko, A G; Dontsova, E P; Venediktova, L V

302

Study on measures to improve gas-liquid phase mixing in a multiphase pump impeller under high gas void fraction  

NASA Astrophysics Data System (ADS)

Rotodynamic multiphase pump can transport crude gas-liquid mixture produced from oil well, and is regarded as the good choice of oil-gas multiphase transportation in offshore product system, for its advantages that compact structure, large flow rate, not sensitive to solid particles in the fluid. However, it is prone to bring about gas-liquid separation within the impeller under high gas void fraction. To solve the problem, this paper presents several measures to break gas packet and inhibit gas-liquid separation, such as, depositing the short blades, opening holes at the blades where gas packets gather, using T-shaped blades, etc. Then, CFD software was used to simulate the flow fields which were added measures to inhibit gas-liquid separation. The results show that streamlines in three new impellers distribute more evenly than in original impeller, the gas-liquid two phases mixed degree was improved, and the gas-liquid separation was inhibited to some extent. However, adding the short blades and using T-blade impeller failed to improve the differential pressure of impellers. So the placement and the geometrical parameters of the measures inhibiting gas-liquid separation should be further optimized.

Zhang, J. Y.; Zhu, H. W.; Ding, K.; Qiang, R.

2012-11-01

303

Flavor characterization of ripened cod roe by gas chromatography, sensory analysis, and electronic nose.  

PubMed

Characterization of the flavors of ripened roe products is of importance to establish a basis for a standardized product. Flavor profiles of commercially processed ripened roe from Iceland and Norway were studied by sensory analysis, gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS), and an electronic nose to characterize the headspace of ripened roe. Sensory analysis showed that ripened roe odor and flavor in combination with caviar flavor and whey/caramel-like odor give the overall positive effect of the complex characteristic roe flavor. Analysis of volatiles by GC-MS and electronic nose confirmed the presence of aroma compounds contributing to the typical ripening and spoilage flavors detected by the sensory analysis. Methional, 1-octen-3-ol, and 2,6-nonadienal were the most important compounds contributing to ripened roe odor. Spoilage flavors were partly contributed by 3-methyl-1-butanol and 3-methylbutanal, which can be measured by the electronic nose and are suggested as quality indicators for objectively assessing the ripening of roe. Principal component analysis of the overall data showed that GC-O correlated well with sensory evaluation and the electronic nose measurements. PMID:15453695

Jonsdottir, Rosa; Olafsdottir, Gudrun; Martinsdottir, Emilia; Stefansson, Gudmundur

2004-10-01

304

Quantitative amino acid analysis of feedstuff hydrolysates by reverse phase liquid chromatography and conventional ion-exchange chromatography.  

PubMed

Corn, soybean meal, and isolated soybean protein samples were acid-hydrolyzed and analyzed for amino acid content by reverse phase liquid chromatography (LC) and by conventional ion-exchange chromatography (IEC) using an amino acid analyzer. The former method employed pre-column derivatization with orthophthalaldehyde (OPTA)/ethanethiol and fluorescence detection. In the LC procedure, glycine and threonine were not resolved, and proline and cyst(e)ine were not detected. In general, amino acid values obtained by LC and IEC compared closely within and across feedstuffs, and both agreed well with published amino acid composition data. The notable exceptions were aspartic acid, glutamic acid, and alanine. Results of this study suggest that reverse phase LC with pre-column OPTA derivatization can be applied to accurately measure primary amino acids in individual feedstuffs. PMID:6501145

Elkin, R G

305

Comparison of different liquid chromatography conditions for the separation and analysis of organotin compounds in mussel and oyster tissue by liquid chromatography–inductively coupled plasma mass spectrometry  

Microsoft Academic Search

In this paper, a new high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICP-MS) methodology for the analysis of organotin compounds in complex matrices is described. Earlier studies had failed to show baseline resolution between dibutyltin (DBT) and triphenyltin (TPhT). The data presented in this paper show that, by using a different C-18 stationary phase material (Ace C-18) with decreased particle

Raimund Wahlen; Tim Catterick

2003-01-01

306

Ion Chromatography.  

ERIC Educational Resources Information Center

Accurate for the analysis of ions in solution, this form of analysis enables the analyst to directly assay many compounds that previously were difficult or impossible to analyze. The method is a combination of the methodologies of ion exchange, liquid chromatography, and conductimetric determination with eluant suppression. (Author/RE)

Mulik, James D.; Sawicki, Eugene

1979-01-01

307

Surface-activated chemical ionization and cation exchange chromatography for the analysis of enterotoxin A.  

PubMed

Surface-activated chemical ionization (SACI) has been widely used in recent years for the analysis of different compounds (e.g. peptides, street drugs, amino acids). The main benefits of this technology are its high sensitivity and its effectiveness under different chromatographic conditions [i.e. ion exchange chromatography and reversed-phase (RP) chromatography]. Here we used SACI in conjunction with quadrupole time-of-flight mass spectrometry to analyze enterotoxin A, which is produced by Staphylococcus aureus, in milk matrix using both RP and ion exchange chromatographies. SACI had increased sensitivity as compared with electrospray ionization. Moreover, the higher quantitation efficiency of this technique, mainly in terms of limit of detection (0.01 ng/ml), limit of quantitation (0.05 ng/ml), linearity range (0.05-50 ng/ml), matrix effect, accuracy (intraday and interday accuracy errors were 9.2% and 10.3%, respectively) and precision (intraday and interday precision errors were 5.3% and 12.8%, respectively), is shown and discussed. PMID:19753553

Cristoni, Simone; Zingaro, Lorenzo; Canton, Cristina; Cremonesi, Paola; Castiglioni, Bianca; Morandi, Stefano; Brasca, Milena; Luzzana, Massimo; Battaglia, Cristina

2009-10-01

308

Practice on high performance liquid chromatography. Applications, equipment, and quantitative analysis  

SciTech Connect

The title of this book suggests yet another general text on the principles and practice of HPLC-of which there are at least a dozen currently available. This is not the case, however. Instead, the editor has assembled a series of more specialized chapters addressed to the experienced chromatographer. That is, it is assumed that the reader has already been exposed to a more general and basic book on HPLC. Thus, there is no general discussion of the principles of separation, extracolumn effects, how an HPLC procedure is developed, column packings and techniques for reversed-phase HPLC, etc. The first five chapters of the book deal with equipment, quantitative analysis, preparative HPLC, column switching, and sample pretreatment. This paper of the book contains useful material not often seen in other books or review articles. The next two chapters deal with liquid-liquid and ion pair chromatography but ignore reversed-phase, normal-phase, and ion exchange chromatography. The final eight chapters deal with applications in different areas: inorganic samples, forensic chemistry, lipids, nucleic acid metabolites, drugs of pharmaceutical interest, amino acids, proteins, and coal and oil products. To summarize, this book is something between a basic text on HPLC and a review series such as Giddings's Advances in Chromatography. Whereas every practicing chromatographer should have a book of the first kind, libraries are the usual customers for the second kind. The author found this book useful in a variety of ways and so should many other reader.

Engelhardt, H. (ed.)

1986-01-01

309

Efficiency and pressure recovery in hydraulic jet pumping of two-phase gas/liquid mixtures  

SciTech Connect

Hydraulic jet pumping of gas/liquid mixtures was studied experimentally, and a mathematical model is proposed to extend the standard single-phase model for predicting efficiency and pressure recovery to suction fluids with gas/liquid ratios up to 2.200 scf/STB. The experimental program comprises 616 low-pressure tests in a plastic model pump designed for flow visualization and measurement of pressure profile along the throat and diffuser, and 373 high-pressure tests on a stock pump. For the high-pressure tests, power fluid was supplied at 200 to 3,000 psi and at 200 to 860 B/D; air was supplied from 0 to 185 Mscf/D. Discharge pressures ranged from 800 to 2,000 psi.

Jlao, B.; Blals, R.N.; Schmidt, Z. (Tulsa Univ., OK (USA))

1990-11-01

310

Static gas-liquid interfacial direct current discharge plasmas using ionic liquid cathode  

SciTech Connect

Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we have succeeded in creating the static and stable gas (plasmas)-liquid (ionic liquids) interfacial field using a direct current discharge under a low gas pressure condition. It is clarified that the ionic liquid works as a nonmetal liquid electrode, and furthermore, a secondary electron emission coefficient of the ionic liquid is larger than that of conventional metal electrodes. The plasma potential structure of the gas-liquid interfacial region, and resultant interactions between the plasma and the ionic liquid are revealed by changing a polarity of the electrode in the ionic liquid. By utilizing the ionic liquid as a cathode electrode, the positive ions in the plasma region are found to be irradiated to the ionic liquid. This ion irradiation causes physical and chemical reactions at the gas-liquid interfacial region without the vaporization of the ionic liquid.

Kaneko, T. [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan); CREST/JST, Tokyo 102-0075 (Japan); Baba, K.; Hatakeyama, R. [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan)

2009-05-15

311

Numerical simulations of gas-liquid two-phase flows in a micro porous structure  

NASA Astrophysics Data System (ADS)

The lattice Boltzmann method for two-phase fluid flows is applied to the simulations of gas-liquid two-phase flows in a micro porous structure for various capillary numbers at low Reynolds numbers. The behaviors of the gas-liquid interface and the velocities of the two-phase fluid in the structure are simulated, and the permeability of gas and liquid through the structure are estimated from the calculated results. By changing the void fraction, the contact angle of the interface on walls, and the surface tension, the effect of these properties on the behaviors and the permeability of the two-phase flows in the micro porous structure is investigated. It is found that the permeability of liquid flows depends on the contact angle and it increases for hydrophobic walls. It is also seen that liquid flows are choked in pores for large void fractions and low capillary numbers.

Tomiyasu, J.; Inamuro, T.

2009-04-01

312

Flow Patterns of Gas-Liquid Two-Phase Flow in Round Tube With Sudden Expansion  

Microsoft Academic Search

Experimental studies were made on the multi-dimensional behavior of upward gas-liquid two-phase flow through the vertical round tube with an axisymmetric sudden expansion, which is one of the typical multi-dimensional channel geometry. The aims of this study are to clarify the multi-dimensional behavior of bubbly or slug flow affected by sudden expansion channel geometry, and to accumulate the experimental data

Koichi Kondo; Kenji Yoshida; Tadayoshi Matsumoto; Tomio Okawa; Isao Kataoka

2002-01-01

313

Drop tower experiment for performance evaluation of gas-liquid equilibrium thruster for small spacecraft  

Microsoft Academic Search

JAXA\\/ISAS is developing the gas-liquid equilibrium thruster for a small spacecraft. In small spacecrafts, the thruster system must be simple and its weight must be light. This thruster system uses HFC-134a (1,1,1,2-tetrafluoroethane) , a kind of liquefied gas, as propellant because of its harmlessness and ease of handling. And this thruster stores propellant as liquid in the tank and ejects

Norizumi Motooka; Takayuki Yamamoto; Osamu Mori; Yoshinobu Okano; Yoshihiro Kishino; Junichiro Kawaguchi

2010-01-01

314

NUMERICAL SIMULATION OF GAS-LIQUID TWO-PHASE FLOW IN SIPHON OUTLETS OF PUMPING PLANTS  

Microsoft Academic Search

Siphon outlets of pump discharge lines are used in pumping plants. It is necessary to evacuate air downstream from siphon outlets as bubble entrainment by water flow after plant start-up. A numerical method has been developed for prediction of gas-liquid two-phase flow dynamics during self-priming of the siphon outlets by using a two-dimensiona l extended two-fluid model. This method is

AKIHIKO MINATO; TAKUJI NAGAYOSHI; KAZUHIDE TAKAMORI; ICHIROU HARADA; MASAHIRO MASE; KENJI OTANI

315

Gas–liquid two-phase flow in microchannels Part I: two-phase flow patterns  

Microsoft Academic Search

Capillary gas–liquid two-phase flow occurs in increasingly more modern industrial applications. The existing relevant data are limited and are inconsistent with respect to the reported flow patterns and their transition boundaries. A systematic experimental investigation of two-phase flow patterns in microchannels was the objective of this study.Using air and water, experiments were conducted in circular microchannels with 1.1 and 1.45mm

K. A. Triplett; S. M. Ghiaasiaan; S. I. Abdel-Khalik; D. L. Sadowski

1999-01-01

316

Two-phase mass transfer in channel electrolyzers with gas-liquid flow  

Microsoft Academic Search

The electrochemical limiting current method was employed to study the mass transfer to a solid electrode in cocurrent gas-liquid flow through a vertical parallel-plate electrolyzer. Three systems were investigated: aqueous ferricyanide, aqueous ferricyanide containing a dispersion of nitrogen bubbles, and aqueous electrolyte containing a dispersion of oxygen bubbles in equilibrium with the liquid phase. The total mass-transfer rate was found

D. J. Economou; R. C. Alkire

1985-01-01

317

Hydrodynamics and mass transfer in a multicell gas?liquid contactor  

Microsoft Academic Search

The EUROPOLL multicell scrubber is a new gas?liquid contactor that is presented as a regular package in three directions of elementary cells in which the gas and the liquid phases are flowing countercurrently and vertically.The scrubber is hydrodynamically characterized by the flow regimes, the liquid holdup, the pressure drop and the operating domain for different air?liquid systems.For the mass transfer,

Souhila Djerid; André Laurent; Christian Belin

1982-01-01

318

Effect of Taylor vortices on calcium carbonate crystallization by gas–liquid reaction  

Microsoft Academic Search

The effects of Taylor vortices on the mean size, size distribution, and morphology of calcium carbonate crystallized by the reaction of gaseous carbon dioxide and aqueous calcium hydroxide were experimentally investigated in a Couette–Taylor reactor. Via the absorption of CO2 gas into pure water, the mass transfer coefficient of CO2 at the gas–liquid interface was measured relative to the rotating

Sung Hoon Kang; Sang Goo Lee; Wang Mo Jung; Min Chan Kim; Woo-Sik Kim; Chang Kyun Choi; Robert S Feigelson

2003-01-01

319

Performance Improvement of Gas Liquid Cylindrical Cyclone Separators Using Integrated Level and Pressure Control Systems  

Microsoft Academic Search

The performance of gas-liquid cylindrical cyclone (GLCC ©1 ) separators for two-phase flow metering loop can be improved by eliminating liquid overflow into the gas leg or gas blow-out through the liquid leg, utilizing suitable integrated control systems. In this study, a new integrated control system has been developed for the GLCC, in which the control is achieved by a

Shoubo Wang; Ram S. Mohan; Ovadia Shoham; Jack D. Marrelli; Gene E. Kouba

2000-01-01

320

Cavitation and gas-liquid flow in fluid machinery and devices. FED-Volume 190  

Microsoft Academic Search

Cavitation and gas-liquid two-phase flow have remained important areas in many industrial applications and constantly provided challenges for academic researchers and industrial practitioners alike. Cavitation and two-phase flow commonly occur in fluid machinery such as pumps, propellers, and fluid devices such as orifices, valves, and diffusers. Cavitation not only degrades the performance of these machines and devices but deteriorates the

J. H. Kim; W. B. Morgan; O. Furuya

1994-01-01

321

Matrix effects in quantitative pesticide analysis using liquid chromatography-mass spectrometry.  

PubMed

Combined liquid chromatography-mass spectrometry using electrospray or atmospheric-pressure chemical ionization has become an important tool in the quantitative analysis of pesticide residues in various matrices in relation to environmental analysis, food safety, and biological exposure monitoring. One of the major problems in the quantitative analysis using LC-MS is that compound and matrix-dependent response suppression or enhancement may occur, the so-called matrix effect. This article reviews issues related to matrix effects, focusing on quantitative pesticide analysis, but also paying attention to expertise with respect to matrix effects acquired in other application areas of LC-MS, especially quantitative bioanalysis in the course of drug development. PMID:16783795

Niessen, W M A; Manini, P; Andreoli, R

322

High-performance anion-exchange chromatography with pulsed amperometric detection for carbohydrate analysis of glycoproteins.  

PubMed

High-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) is an established technique for the carbohydrate analysis of glycoproteins. HPAE-PAD is routinely used for determinations of monosaccharide, sialic acid, mannose-6-phosphate (M-6-P), and oligosaccharide contents of a glycoprotein. This is true for both the initial investigation of a glycoprotein and routine assays of recombinant therapeutic glycoproteins. This contribution reviews the fundamentals of HPAE-PAD, recent technological improvements, and advances in the last ten years in its application to carbohydrate analysis of glycoproteins. The application areas reviewed include monosaccharide determinations, sialic acid determinations, M-6-P determinations, sugar alcohol determinations, analysis of polysialic acids, neutral and charged oligosaccharide analysis, following glycosidase and glycosyltransferase reactions, and coupling HPAE-PAD to mass spectrometry (MS). PMID:24010833

Rohrer, J S; Basumallick, L; Hurum, D

2013-07-01

323

U.S. crude oil, natural gas, and natural gas liquids reserves 1995 annual report  

SciTech Connect

The EIA annual reserves report series is the only source of comprehensive domestic proved reserves estimates. This publication is used by the Congress, Federal and State agencies, industry, and other interested parties to obtain accurate estimates of the Nation`s proved reserves of crude oil, natural gas, and natural gas liquids. These data are essential to the development, implementation, and evaluation of energy policy and legislation. This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1995, as well as production volumes for the US and selected States and State subdivisions for the year 1995. Estimates are presented for the following four categories of natural gas: total gas (wet after lease separation), nonassociated gas and associated-dissolved gas (which are the two major types of wet natural gas), and total dry gas (wet gas adjusted for the removal of liquids at natural gas processing plants). In addition, reserve estimates for two types of natural gas liquids, lease condensate and natural gas plant liquids, are presented. Also included is information on indicated additional crude oil reserves and crude oil, natural gas, and lease condensate reserves in nonproducing reservoirs. A discussion of notable oil and gas exploration and development activities during 1995 is provided. 21 figs., 16 tabs.

NONE

1996-11-01

324

Low-frequency sound transmission through a gas-liquid interface.  

PubMed

Typically, sound speed in gases is smaller and mass density is much smaller than in liquids, resulting in a very strong acoustic impedance contrast at a gas-liquid interface. Sound transmission through a boundary with a strong impedance contrast is normally very weak. This paper studies the power output of localized sound sources and acoustic power fluxes through a plane gas-liquid interface in a layered medium. It is shown that, for low-frequency sound, a phenomenon of anomalous transparency can occur where most of the acoustic power generated by a source in a liquid half-space can be radiated into a gas half-space. The main physical mechanism responsible for anomalous transparency is found to be an acoustic power transfer by inhomogeneous (evanescent) waves in the plane-wave decomposition of the acoustic field in the liquid. The effects of a liquid's stratification and of guided sound propagation in the liquid on the anomalous transparency of the gas-liquid interface are considered. Geophysical and biological implications of anomalous transparency of water-air interface to infrasound are indicated. PMID:18396996

Godin, Oleg A

2008-04-01

325

Annual report of the origin of natural gas liquids production form EIA-64A  

SciTech Connect

The collection of basic, verifiable information on the Nation`s reserves and production of natural gas liquids (NGL) is mandated by the Federal Energy Administration Act of 1974 (FEAA) (Public Law 93-275) and the Department of Energy Organization Act of 1977 (Public Law 95-91). Gas shrinkage volumes reported on Form EIA-64A by natural gas processing plant operators are used with natural gas data collected on a {open_quotes}wet after lease separation{close_quotes} basis on Form EIA-23, Annual Survey of Domestic Oil and Gas Reserves, to estimate {open_quotes}dry{close_quotes} natural gas reserves and production volumes regionally and nationally. The shrinkage data are also used, along with the plant liquids production data reported on Form EIA-64A, and lease condensate data reported on Form EIA-23, to estimate regional and national gas liquids reserves and production volumes. This information is the only comprehensive source of credible natural gas liquids data, and is required by DOE to assist in the formulation of national energy policies.

NONE

1995-12-31

326

Cavitation and gas-liquid flow in fluid machinery and devices. FED-Volume 190  

SciTech Connect

Cavitation and gas-liquid two-phase flow have remained important areas in many industrial applications and constantly provided challenges for academic researchers and industrial practitioners alike. Cavitation and two-phase flow commonly occur in fluid machinery such as pumps, propellers, and fluid devices such as orifices, valves, and diffusers. Cavitation not only degrades the performance of these machines and devices but deteriorates the materials. Gas-liquid two-phase flow has also been known to degrade the performance of pumps and propellers and can often induce an instability. The industrial applications of cavitation and two-phase flow can be found in power plants, ship propellers, hydrofoils, and aerospace equipment, to name but a few. The papers presented in this volume reflect the variety and richness of cavitation and gas-liquid two-phase flow in various flow transporting components and the increasing role they play in modern and conventional technologies. Separate abstracts were prepared for 35 papers in this book.

O`Hern, T.J.; Kim, J.H.; Morgan, W.B.; Furuya, O. [eds.

1994-12-31

327

Toward Unraveling Grape Tannin Composition: Application of Online Hydrophilic Interaction Chromatography × Reversed-Phase Liquid Chromatography-Time-of-Flight Mass Spectrometry for Grape Seed Analysis.  

PubMed

Despite the significant importance of tannins in viticulture and enology, relatively little is known about the detailed chemical composition of these molecules. This is due to challenges associated with the accurate analytical determination of the highly structurally diverse proanthocyanidins which comprise tannins. In this contribution, we address this limitation by demonstrating how online comprehensive two-dimensional liquid chromatography (LC × LC) coupled to high resolution mass spectrometry (HR-MS) can be exploited as a powerful analytical approach for the detailed characterization of grape seed tannins. Hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RP-LC) were employed in the two dimensions to provide complementary information in terms of separation according to hydrophilicity and hydrophobicity, respectively. Online coupling of HILIC × RP-LC with fluorescence detection and electrospray ionization MS delivered high resolution analysis in a practical analysis time, while allowing selective detection and facilitating compound identification. Time-of-flight (TOF) MS provided high acquisition rates and sensitivity coupled to accurate mass information, which allowed detection of procyanidins up to a degree of polymerization (DP) of 16 and a degree of galloylation up to 8 in a red grape seed extract. This analytical methodology promises to shed new light on these important grape constituents and potentially on their evolution during wine production. PMID:23978274

Kalili, Kathithileni M; Vestner, Jochen; Stander, Maria A; de Villiers, André

2013-09-13

328

Microwave-assisted derivatization procedures for gas chromatography\\/mass spectrometry analysis  

Microsoft Academic Search

In this review, published applications of microwave-assisted derivatization procedures for gas chromatography\\/mass spectrometry\\u000a (GC\\/MS) are summarized. Among the broad range of analytical techniques available, GC\\/MS is still the method of choice for\\u000a most high-throughput screening procedures in forensic\\/clinical toxicology, doping control and food and environmental analysis.\\u000a Despite the many advantages of the GC\\/MS method, time-consuming derivatization steps are often required

Sandra L. Söderholm; Markus Damm; C. Oliver Kappe

2010-01-01

329

Determination of Np-237 by radiochemical neutron activation analysis combined with extraction chromatography.  

PubMed

A procedure for determination of 237Np, 238Pu, 239,240Pu and 241Pu in environmental samples is described. Neptunium-237 is determined using radiochemical neutron activation analysis with pre- and post-irradiation chemistry based on solvent extraction and extraction chromatography. 238Pu, 239,240Pu is determined using alpha spectrometry and 241Pu by liquid scintillation spectrometry. The vertical profiles of 237Np, 238Pu, 239,240Pu in bottom sediments from the Black Sea are presented. PMID:14987710

Kalmykov, St N; Aliev, R A; Sapozhnikov, D Yu; Sapozhnikov, Yu A; Afinogenov, A M

330

Comparative evaluation between capillary electrophoresis and high-performance liquid chromatography for the analysis of florfenicol in plasma  

Microsoft Academic Search

A capillary electrophoresis (CE) and a reversed phase high-performance liquid chromatography (RP-HPLC) method with UV detection have been developed for florfenicol analysis in plasma samples. The suitabilities of both methods for quantitative determination of florfenicol were approved through validation specification, such as linearity, precision, selectivity, accuracy, limit of detection and quantification. The capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC)

Piotr Kowalski; Lucyna Konieczna; Aleksandra Chmielewska; Ilona Ol?dzka; Alina Plenis; Micha? Bieniecki; Henryk Lamparczyk

2005-01-01

331

Application of polydivinylbenzene liquid chromatography columns to remove lipid material from fish tissue extracts for the analysis of semivolatile organics  

Microsoft Academic Search

Liquid chromatography columns of 100% polydivinylbenzene (DVB) (packing) were used to remove lipid material from fish extracts before analysis of several semivolatile organic pollutants by gas chromatography–mass spectrometry (GC–MS). This packing material was found to be durable as the columns could be operated to about 900 p.s.i. resulting in high efficiency separation. Recoveries and relative standard deviations for 18 polynuclear

Gerald H Dodo; Margaret M Knight

1999-01-01

332

Analysis of endogenous gibberellins and gibberellin metabolites from Dalbergia dolichopetala by gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry  

Microsoft Academic Search

Qualitative gas chromatography-mass spectrometry (GC-MS) analysis of purified extracts from 4-d-germinated seeds of “jacarandá do cerrodo” (Dalbergia dolichopetala) detected gibberellin A1 GA1, epi-GA1 GA3, GA4, GA5, GA8, GA20 and G28. Quantitative analysis, using deuterated internal standards, showed that the germinated seed contained 29 ng GA1, 0.6 ng G4, 0.08 ng G5 and 1.7 ng GA20 · g-1 fresh weight. In

Thomas Moritz; Ana Maria Monteiro

1994-01-01

333

Interfacial Areas and Mass Transfer Coefficients in Various Types of Gas-Liquid Absorbers and Reactors: Review Paper.  

National Technical Information Service (NTIS)

Results are presented of determinations of interfacial areas and mass transfer coefficients for use in designing or scaling up of all types of gas-liquid absorbers and reactors in industry. 74 references, 18 figures. (ERA citation 01:026202)

A. Laurent J. C. Charpentier

1974-01-01

334

Enantiomeric analysis of limonene and carvone by direct introduction of aromatic plants into multidimensional gas chromatography.  

PubMed

Analysis of chiral compounds in complex mixtures is achieved by multidimensional gas chromatography using heptakis-(2,3,6-tri-O-methyl)-?-cyclodextrin stationary phase as the main column of the system to separate specific selected cuts containing components unresolved in the first dimension. The proposed procedure allows rapid analysis of both solid and liquid matrices by direct introduction, into the programmed temperature vaporizer (PTV) of a gas chromatograph, of either the plant material or the essential oil, respectively. A comparison between enantiomeric excesses data obtained, from plant leaves (or plant seeds) and the corresponding essential oils, by direct injection (i.e., without sample pretreatment or concentration step) into the multidimensional system is also included. Reported data demonstrate that no racemization occurs during analysis as identical enantiomeric excesses are obtained in both cases for specific chiral compounds. PMID:23598101

Barba, C; Toledano, R M; Santa-María, G; Herraiz, M; Martínez, R M

2012-12-19

335

Highly sensitive analysis of iodide anion in seaweed as pentafluorophenoxyethyl derivative by capillary gas chromatography.  

PubMed

A simple and sensitive gas chromatography (GC) method is described for the trace analysis of iodide anion (iodide) in processed seaweed as an organic derivative. The method is based on the derivatization of aqueous iodide extracted from seaweed with 2-(pentafluorophenoxy)ethyl 2-(piperidino)ethanesulfonate in toluene using tetra-n-hexylammonium bromide as a phase-transfer catalyst. The resulting pentafluorophenoxyethyl iodide is highly responsive to an electron-capture detector (ECD) and was analyzed by GC-ECD, giving a low detection limit of approximately 2.7 nM (2.7 fmol/microL injected). Interferences of some common anions in the analysis of iodide were studied and proved to be minimal. Application of the method to the analysis of iodide in processed seaweed was performed. PMID:12568540

Lin, Feng-Min; Wu, Hsin-Lung; Kou, Hwang-Shang; Lin, Shun-Jin

2003-02-12

336

A liquid chromatography-tandem mass spectrometry method for fluazifop residue analysis in crops.  

PubMed

An LC-MS-MS assay is described for fluazifop residue analysis in crops. The residues are extracted with acidified organic solvent, the esters and conjugates are hydrolysed with 6 M hydrochloric acid, then the extracts are cleaned-up by solid phase extraction using C2(EC) and Si cartridges in tandem. Quantitative analysis is performed by gradient liquid chromatography coupled to triple quadrupole mass spectrometer using atmospheric pressure chemical ionisation. All fluazifop-P-butyl, free fluazifop-P and any conjugates are quantified as fluazifop-P. The limit of quantification is 0.01-0.05 mg/kg depending on crop matrices. The clean-up method is also suitable for LC-UV analysis with a compromise in higher limit of quantification 0.05-0.2 mg/kg. PMID:11227569

Bolygo, E; Boseley, A

2000-12-01

337

Multivariate analysis of progressive thermal desorption coupled gas chromatography-mass spectrometry.  

SciTech Connect

Thermal decomposition of poly dimethyl siloxane compounds, Sylgard{reg_sign} 184 and 186, were examined using thermal desorption coupled gas chromatography-mass spectrometry (TD/GC-MS) and multivariate analysis. This work describes a method of producing multiway data using a stepped thermal desorption. The technique involves sequentially heating a sample of the material of interest with subsequent analysis in a commercial GC/MS system. The decomposition chromatograms were analyzed using multivariate analysis tools including principal component analysis (PCA), factor rotation employing the varimax criterion, and multivariate curve resolution. The results of the analysis show seven components related to offgassing of various fractions of siloxanes that vary as a function of temperature. Thermal desorption coupled with gas chromatography-mass spectrometry (TD/GC-MS) is a powerful analytical technique for analyzing chemical mixtures. It has great potential in numerous analytic areas including materials analysis, sports medicine, in the detection of designer drugs; and biological research for metabolomics. Data analysis is complicated, far from automated and can result in high false positive or false negative rates. We have demonstrated a step-wise TD/GC-MS technique that removes more volatile compounds from a sample before extracting the less volatile compounds. This creates an additional dimension of separation before the GC column, while simultaneously generating three-way data. Sandia's proven multivariate analysis methods, when applied to these data, have several advantages over current commercial options. It also has demonstrated potential for success in finding and enabling identification of trace compounds. Several challenges remain, however, including understanding the sources of noise in the data, outlier detection, improving the data pretreatment and analysis methods, developing a software tool for ease of use by the chemist, and demonstrating our belief that this multivariate analysis will enable superior differentiation capabilities. In addition, noise and system artifacts challenge the analysis of GC-MS data collected on lower cost equipment, ubiquitous in commercial laboratories. This research has the potential to affect many areas of analytical chemistry including materials analysis, medical testing, and environmental surveillance. It could also provide a method to measure adsorption parameters for chemical interactions on various surfaces by measuring desorption as a function of temperature for mixtures. We have presented results of a novel method for examining offgas products of a common PDMS material. Our method involves utilizing a stepped TD/GC-MS data acquisition scheme that may be almost totally automated, coupled with multivariate analysis schemes. This method of data generation and analysis can be applied to a number of materials aging and thermal degradation studies.

Van Benthem, Mark Hilary; Mowry, Curtis Dale; Kotula, Paul Gabriel; Borek, Theodore Thaddeus, III

2010-09-01

338

Two Methods for Measurement of Gas-Liquid Flows in Vertical Upward Pipe Using Dual-Plane ERT System  

Microsoft Academic Search

In modern industrial processes, the accurate measurement of two-phase flow is an important task. Process tomography can provide a distribution information of a two-phase pipe flow. In order to carry out instantaneous flowrate measurements of the gas-liquid two-phase flow in a vertical upward pipe, a dual-plane electrical-resistance-tomography (ERT) system is combined with a cross-correlation technique to measure the gas-liquid two-phase

Feng Dong; Yanbin Xu; Lei Hua; Huaxiang Wang

2006-01-01

339

Transport evaluation of a gas-liquid scrubber. [Five-tray, single-bubble-cap, single-downcomer, gas liquid contactor  

SciTech Connect

The hydraulics and the mass-transfer behavior of a five-tray, single-bubble-cap, single-downcomer, gas-liquid contactor were studied for use as a gas scrubber. Flooding was not observed at the maximum available liquid and gas flow rates of 0.32 and 464 L/min, respectively. The maximum liquid entrainment was 33% at a gross liquid flow rate of 0.05 L/min. The Murphree-tray efficiencies for absorption of CO/sub 2/ (5000 ppM in air) into demineralized water ranged from 0.14 to 0.74 for volumetric liquid-to-gas ratios of 4 x 10/sup -4/ and 2 x 10/sup -4/, respectively, for k/sub L/a values ranging from 0.088 to 0.36 min/sup -1/. 12 figures, 10 tables.

Brodner, A.J.; Bistline, J.E.; Weber, S.E.

1982-10-01

340

Analysis of coal conversion recycle solvents by liquid chromatography with nuclear magnetic resonance detection  

SciTech Connect

The analyses of two coal conversion recycle process solvents, one of them hydrotreated, via high-performance liquid chromatography (HPLC) with a continuous flow nuclear magnetic resonance (NMR) detector are reported. The differences between these samples with reference to the role of the solvent in coal liquefaction are discussed. The LC-/sup 1/H NMR technique characterized the hydrocarbons and aromatic ethers with a level of certainty not possible with conventional detectors. In addition, qualitative GC-MS analysis of off-line LC fractions was performed on the recycle solvent sample. LC-/sup 1/H NMR and LC-GC-MS were found to be complementary for volatile samples. Gel permeation chromatography-/sup 1/H nuclear magnetic resonance (GPC-/sup 1/H NMR) analysis of the recycle solvent sample was not as successful as LC-/sup 1/H NMR since class separation is almost essential for this sample. But the introduction of GPC-/sup 1/H NMR is still of interest since GPC is the most appropriate mode of separation for many samples.

Haw, J.F.; Glass, T.E.; Dorn, H.C.

1981-12-01

341

Characterization of commercial soybean products by conventional and perfusion reversed-phase high-performance liquid chromatography and multivariate analysis.  

PubMed

Conventional and perfusion reversed-phase high-performance liquid chromatography are used to characterize commercial soybean products for human consumption. For this purpose, previously optimized methods of conventional and perfusion chromatography applied to the separation of soybean proteins are employed. Sixty different samples corresponding to 26 different trademarks of soybean products [soybean protein isolate, soybean flour, textured soybean, soybean milks (liquid and powdered), and soybean infant formulas] are analyzed. Characterization of soybean products is carried out on the basis of their protein profiles obtained by both chromatographic methods. Data obtained are processed using multivariate methods such as principal components and discriminant analysis. Perfusion chromatography enables a further and faster characterization of commercial soybean products than conventional chromatography, of great value in the quality control of this kind of product. PMID:10905692

García, M C; Torre, M; Marina, M L

2000-06-01

342

Different headspace solid phase microextraction - Gas chromatography/mass spectrometry approaches to haloanisoles analysis in wine.  

PubMed

Three approaches in determination of six haloanisoles (2,4,6-trichloroanisole, 2,3,4-trichloroanisole, 2,3,6-trichloroanisole, tetrachloroanisole, pentachloroanisole and 2,4,6-tribromoanisole) in wine were compared. Comprehensive gas chromatography - time of flight mass spectrometry (GC×GC-ToF-MS) was described for the first time for this application and compared to gas chromatography-tandem mass spectrometry (GC-MS/MS) using triple quadrupole instrument. These techniques were compared with "standard" analytical approach using GC-MS(SIM). SPME method was developed and used for all separation methods (DVB/PDMS fiber, 70°C, 30%NaCl, 20min extraction). Extraction dependence on matrix was discussed using model wines with different ethanol contents (8%, 12%, and 18%) as well as water and different wines (dry white, dry red and sweet liqueur), with the lowest sensitivities obtained for highest ethanol contents in model wine and for liqueur wine. Limits of detection for GC×GC-ToF-MS method were 0.09-2.92ng/L depending on the examined compound and matrix (compared to 0.1-13.3ng/L obtained using GC/MS(SIM)). For GC-MS/MS method lower detection limits were achieved than for the GC×GC method (0.01-0.1ng/L), however comprehensive gas chromatography-mass spectrometry provides full spectral information on analyzed compounds. Both methods had limits of detection far below odor thresholds of haloanisoles in wine, good linearity up to 2000ng/L tested and good precision, what makes them suitable for analysis of these compounds in low ppt levels. PMID:23932370

Jele?, Henryk H; Dziadas, Mariusz; Majcher, Ma?gorzata

2013-07-26

343

High pressure\\/high temperature vapor liquid equilibrium study of light gases in hydrogen-coal liquid model compound systems using perturbation chromatography  

Microsoft Academic Search

Perturbation chromatography or gas-liquid partition chromatography (GLPC) provides a powerful tool for making physicochemical measurements. In this investigation GLPC was applied to study the vapor-liquid equilibrium behavior of light gases in nonvolatile coal liquid model compound solvents at high temperatures and high pressures. Improvements made in existing GLPC techniques include: the use of a high pressure tandem proportioning pump to

Kragas

1983-01-01

344

Green chromatography.  

PubMed

Analysis of organic compounds in samples characterized by different composition of the matrix is very important in many areas. A vast majority of organic compound determinations are performed using gas or liquid chromatographic methods. It is thus very important that these methods have negligible environmental impact. Chromatographic techniques have the potential to be greener at all steps of the analysis, from sample collection and preparation to separation and final determination. The paper summarizes the approaches used to accomplish the goals of green chromatography. While complete elimination of sample preparation would be an ideal approach, it is not always practical. Solventless extraction techniques offer a very good alternative. Where solvents must be used, the focus should be on the minimization of their consumption. The approaches used to make chromatographic separations greener differ depending on the type of chromatography. In gas chromatography it is advisable to move away from using helium as the carrier gas because it is a non-renewable resource. GC separations using low thermal mass technology can be greener because of energy savings offered by this technology. In liquid chromatography the focus should be on the reduction of solvent consumption and replacement of toxic and environmentally hazardous solvents with more benign alternatives. Multidimensional separation techniques have the potential to make the analysis greener in both GC and LC. The environmental impact of the method is often determined by the location of the instrument with respect to the sample collection point. PMID:23932374

P?otka, Justyna; Tobiszewski, Marek; Sulej, Anna Maria; Kupska, Magdalena; Górecki, Tadeusz; Namie?nik, Jacek

2013-08-01

345

Analysis of perchlorate in human urine using ion chromatography and electrospray tandem mass spectrometry.  

PubMed

Because of health concerns surrounding widespread exposure to perchlorate, we developed a sensitive and selective method for quantifying perchlorate in human urine using ion chromatography coupled with electrospray ionization tandem mass spectrometry. Perchlorate was quantified using a stable isotope-labeled internal standard ((18)O(4)-perchlorate) with excellent assay precision (coefficient of variation <5% for repetitively analyzed quality control material). Analytical accuracy was established by blind analysis of certified proficiency testing materials prepared in synthetic urine matrix; calculated amounts deviated minimally from true amounts, with percent differences ranging from 2% to 5%. Selective chromatography and tandem mass spectrometry reduced the need for sample cleanup, resulting in a rugged and rapid method capable of routinely analyzing 75 samples/day. The lowest reportable level (0.025 ng/mL) was sufficiently sensitive to detect perchlorate in all human urine samples evaluated to date, with a linear response range from 0.025 to 100 ng/mL. This selective, sensitive, and rapid method will help elucidate any potential associations between human exposure to low levels of perchlorate and adverse health effects. PMID:15828783

Valentín-Blasini, Liza; Mauldin, Joshua P; Maple, David; Blount, Benjamin C

2005-04-15

346

Quantitative Analysis of Sphingomyelin by High-Performance Liquid Chromatography after Enzymatic Hydrolysis  

PubMed Central

Sphingomyelin is the most abundant sphingolipid in mammalian cells and is mostly present in the plasma membrane. A new analytical method using high-performance liquid chromatography (HPLC) was developed to quantify sphingomyelin in mouse plasma and tissues, 3T3-L1 cells, rat aortic smooth muscle cells, and HT-29 cells. Sphingomyelin and dihydrosphingomyelin, an internal standard, were separated by high-performance thin-layer chromatography and simultaneously hydrolyzed with sphingolipid ceramide N-deacylase and sphingomyelinase to release sphingosine and dihydrosphingosine, respectively. Sphingomyelin content was measured by HPLC following o-phthalaldehyde derivatization. Sphingomyelin concentrations in 3T3-L1 cells, rat aortic smooth muscle cells, and HT-29 cells were 60.10 ± 0.24, 62.69 ± 0.08, and 58.38 ± 0.37?pmol/?g protein, respectively, whereas those in brain, kidney, and liver of ICR mice were 55.60 ± 0.43, 43.75 ± 0.21, and 22.26 ± 0.14?pmol/?g protein. The sphingomyelin concentration in mouse plasma was 407.40 ± 0.31??M. The limits of detection and quantification for sphingomyelin were 5 and 20?pmol, respectively, in the HPLC analysis with fluorescence detection. This sensitivity was sufficient for analyzing sphingomyelin in biological samples. In conclusion, this analytical method is a sensitive and specific technique for quantifying sphingomyelin and was successfully applied to diverse biological samples with excellent reproducibility.

Lee, Seunghyun; Lee, Youn-Sun; Choi, Kyeong-Mi; Yoo, Kwang-Sik; Sin, Dong-Mi; Kim, Wonkyun; Lee, Yong-Moon; Hong, Jin-Tae; Yun, Yeo-Pyo; Yoo, Hwan-Soo

2012-01-01

347

Influence of soil type and extraction conditions on perchlorate analysis by ion chromatography.  

PubMed

Perchlorate is a stable anion that has been introduced into the environment through activities related to its production and use as a solid rocket propellant. Perchlorate is thought to transport through soils without being adsorbed; thus, for determination of perchlorate in soil, samples are typically extracted with water prior to analysis. The completeness of extraction depends on perchlorate existing as a free ion within the soil matrix. In this study, perchlorate extraction efficiency was evaluated with five soil types under two different oxygen states. For each soil, 30% (w/w) slurries were prepared and equilibrated under either oxic or anoxic conditions prior to spiking with a stock solution of sodium perchlorate, and the slurries were then maintained for 1-week or 1-month. At the end of the exposure, slurries were centrifuged and separated into aqueous and soil phases. After phase separation, the soil was washed first with deionized water and then with 50mM NaOH, producing second and third aqueous phases, respectively. Perchlorate concentrations in the three aqueous phases were determined using ion chromatography. The results obtained from this study suggest that matrix interference and signal suppression due to high conductivity have greater effects upon observed perchlorate concentrations by ion chromatography than does perchlorate interaction with soil. Thus, a single water extraction is sufficient for quantitative determination of perchlorate in soil. PMID:17092539

MacMillan, Denise K; Dalton, Shana R; Bednar, Anthony J; Waisner, Scott A; Arora, Prem N

2006-11-07

348

Routine application using single quadrupole liquid chromatography-mass spectrometry to pesticides analysis in citrus fruits.  

PubMed

A rapid and sensitive liquid chromatography-electrospray ionization-mass spectrometry method has been developed for the routine analysis of buprofezin, bupirimate, hexaflumuron, tebufenpyrad, fluvalinate and pyriproxyfen in citrus fruits. Extracts were obtained by matrix solid-phase dispersion (MSPD) using C18 as dispersant and dichloromethane-methanol (80:20, v/v) as eluent. Matrix effects were tested for all matrices by addition of standard to sample blank extracts (samples containing no detectable residues). Mean recoveries obtained at fortification levels between 0.01 and 5 mg kg(-1) were 57-97% with relative standard deviations (RSDs) from 5 to 19%. The limits of quantification (LOQ) were in the range of 0.01-0.2 mg kg(-1) and lower than maximum residue limits (MRLs) established by the Spanish legislation. The MSPD was compared with conventional ethyl acetate extraction, showing equivalent recoveries and precision. Although the sample is more concentrated (5-fold) by solid-liquid extraction (SLE) with ethyl acetate than by MSPD, LOQs obtained by both techniques, were almost equal, because MSPD reduces matrix effects, baseline noise, and interfering peaks from the matrix. The proposed method has been applied to the determination of selected pesticides in real samples. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) with quadrupole ion trap (QIT) and triple quadrupole (TQ) have been used as confirmatory tool for positive samples according to a recent No. SANCO/10476/2003 European Union Guideline. PMID:16130755

Soler, Carla; Mañes, Jordi; Picó, Yolanda

2005-09-23

349

[Analysis of pigments from Rhodotorula glutinis by Raman spectroscopy and thin layer chromatography].  

PubMed

The pigments from Rhodotorula glutinis were separated by using thin layer chromatography, and the result showed that Rhodotorula glutinis cells could synthesize at least three kinds of pigments, which were beta-carotene, torulene, and torularhodin. The Raman spectra based on the three pigments were acquired, and original spectra were preprocessed by background elimination, baseline correction, and three-point-smoothing, then the averaged spectra from different pigments were investigated, and the result indicated that Raman shift which represents C-C bond was different, and the wave number of beta-carotene demonstrated the largest deviation, finally torulene and torularhodin in Rhodotorula glutinis had more content than beta-carotene. Quantitative analysis of Raman peak height ratio revealed that peak height ratio of pigments showed little difference, which could be used as parameters for further research on living cells, providing reference content of pigments. The above results suggest that Raman spectroscopy combined with thin layer chromatography can be applied to analyze pigments from Rhodotorula glutinis, provides abundant information about pigments, and serves as an effective method to study pigments. PMID:22582635

Yuan, Yu-feng; Tao, Zhan-hua; Wang, Xue; Li, Yong-qing; Liu, Jun-xian

2012-03-01

350

Analysis of starch in food systems by high-performance size exclusion chromatography.  

PubMed

Starch has unique physicochemical characteristics among food carbohydrates. Starch contributes to the physicochemical attributes of food products made from roots, legumes, cereals, and fruits. It occurs naturally as distinct particles, called granules. Most starch granules are a mixture of 2 sugar polymers: a highly branched polysaccharide named amylopectin and a basically linear polysaccharide named amylose. The starch contained in food products undergoes changes during processing, which causes changes in the starch molecular weight and amylose to amylopectin ratio. The objective of this study was to develop a new, simple, 1-step, and accurate method for simultaneous determination of amylose and amylopectin ratio as well as weight-averaged molecular weights of starch in food products. Starch from bread flour, canned peas, corn flake cereal, snack crackers, canned kidney beans, pasta, potato chips, and white bread was extracted by dissolving in KOH, urea, and precipitation with ethanol. Starch samples were solubilized and analyzed on a high-performance size exclusion chromatography (HPSEC) system. To verify the identity of the peaks, fractions were collected and soluble starch and beta-glucan assays were performed additional to gas chromatography analysis. We found that all the fractions contain only glucose and soluble starch assay is correlated to the HPSEC fractionation. This new method can be used to determine amylose amylopectin ratio and weight-averaged molecular weight of starch from various food products using as low as 25 mg dry samples. PMID:23330715

Ovando-Martínez, Maribel; Whitney, Kristin; Simsek, Senay

2013-01-18

351

Characterization of Low Temperature Carbonization Products of Neyveli Lignite by Gas Chromatography–Mass Spectroscopy  

Microsoft Academic Search

Neyveli lignites of Indian origin were subjected to low temperature carbonization (LTC) at 600°C to collect tar and middle oil boiling at 200°C. Liquid–liquid extraction of these products has yielded asphalts, phenols, acids, bases, waxes, and neutral oils. Each fraction was analysed by gas liquid chromatography and the constituents were characterized by elucidating the structural composition using mass spectrometry. This

R. Nageswara Rao; B. Krishnamacharyulu

2005-01-01

352

[Preparation and evaluation of in-situ synthesis zeolite gas-liquid modified columns].  

PubMed

A new kind of NaA zeolite column has been prepared by in-situ synthesis technique. In comparing with traditional coating method, the in-situ NaA zeolite carrier is much more uniform and rigid. Several kinds of zeolite gas-liquid modified columns have been prepared with this in-situ technology, which showed satisfactory features in separation property and thermal stability. The successful utilization of mini-length and wide-bore columns showed good practical prospect of this new kind of zeolite column. PMID:12545470

Kou, D M; Wu, J M; Li, Z Y; Liu, M; Xiang, S H

2001-11-01

353

Gas-liquid critical point in model ionic fluids with charge and size asymmetry  

NASA Astrophysics Data System (ADS)

We study the effects of size and charge asymmetry on the gas-liquid critical parameters of a primitive model (PM) of ionic fluids. The model is characterized by the two parameters: hard-sphere diameter-, ? = ?+/?- and charge, z = q+/|q-|, ratios of the two ionic species. Using the collective variables based theory we calculate the critical temperature and the critical density for the two versions of PM: an equisize PM with charge asymmetry (? = 1, z?1 and a monovalent PM with size asymmetry (??1, z = 1). The trends obtained for the both critical parameters of the models under consideration agree qualitatively with Monte Carlo simulation findings.

Patsahan, O. V.; Patsahan, T. M.

2009-12-01

354

Quantitative Analysis of Tetramethylenedisulfotetramine ("Tetramine") Spiked into Beverages by Liquid Chromatography Tandem Mass Spectrometry with Validation by Gas Chromatography Mass Spectrometry  

SciTech Connect

Tetramethylenedisulfotetramine, commonly known as tetramine, is a highly neurotoxic rodenticide (human oral LD{sub 50} = 0.1 mg/kg) used in hundreds of deliberate food poisoning events in China. Here we describe a method for quantitation of tetramine spiked into beverages, including milk, juice, tea, cola, and water and cleaned up by C8 solid phase extraction and liquid-liquid extraction. Quantitation by high performance liquid chromatography tandem mass spectrometry (LC/MS/MS) was based upon fragmentation of m/z 347 to m/z 268. The method was validated by gas chromatography mass spectrometry (GC/MS) operated in SIM mode for ions m/z 212, 240, and 360. The limit of quantitation was 0.10 {micro}g/mL by LC/MS/MS versus 0.15 {micro}g/mL for GC/MS. Fortifications of the beverages at 2.5 {micro}g/mL and 0.25 {micro}g/mL were recovered ranging from 73-128% by liquid-liquid extraction for GC/MS analysis, 13-96% by SPE and 10-101% by liquid-liquid extraction for LC/MS/MS analysis.

Owens, J; Hok, S; Alcaraz, A; Koester, C

2008-11-13

355

Multivariate approach for the enantioselective analysis in micellar electrokinetic chromatography-mass spectrometry  

PubMed Central

A mixture of two molecular micelles polysodium N-undecenoxy carbonyl-l-leucinate, (poly-l-SUCL) and polysodium N-undecanoyl leucylvalinate, (poly-l-SULV) was utilized in micellar electrokinetic chromatography-electrospray ionization-mass spectrometry (MEKC-ESI-MS) to simultaneously separate and detect enantiomers of binaphthyl derivatives. Separation parameters such as background buffer composition, voltage, temperature, and nebulizer pressure were optimized using a multivariate central composite design (CCD).Baseline enantioseparation for both analytes was achieved. The CCD was also used in the optimization of sheath liquid and spray chamber parameters to achieve optimum ESI-MS response. The results demonstrate that CCD is a powerful tool for the optimization of MEKC-MS parameters and the response surface model analysis can provide in-depth statistical understandings of the significant factors required to achieve maximum enantioresolution and ESI-MS sensitivity.

He, Jun; Shamsi, Shahab A.

2009-01-01

356

Mycolic Acid Analysis by High-Performance Liquid Chromatography for Identification of Mycobacterium Species  

PubMed Central

Mycobacterium tuberculosis is the etiologic agent of tuberculosis and can be accurately detected by laboratories using commercial genetic tests. Nontuberculosis mycobacteria (NTM) causing other mycobacterioses can be difficult to identify. The identification processes are confounded by an increasing diversity of newly characterized NTM species. The ubiquitous nature of NTM, combined with their potential to be opportunistic pathogens in immunocompromised as well as nonimmunodeficient patients, further complicates the problem of their identification. Since clinical case management varies depending on the etiologic agent, laboratories must identify the species in a timely manner. However, only a few identification methods can detect the species diversity within the Mycobacterium genus. Over the last decade, high-performance liquid chromatography analysis of the mycolic acids has become an accepted method for identification of mycobacteria. In this review, we assess its development and usefulness as an identification technique for Mycobacterium species.

Butler, W. Ray; Guthertz, Linda S.

2001-01-01

357

High performance size exclusion chromatography (IX) bulk and component analysis of silanol groups in polydimethylsiloxanes  

SciTech Connect

Methods for the bulk and molecular weight component analysis of hydroxyl groups attached to silicon in polydimethylsiloxanes of the Sylgard type have been developed. The infrared (ir) absorbance band of the silanol adduct produced by hydrogen bonding with 1,4-dioxane is used. The determination of hydroxyl content as a function of molecular weight employs an on-line size exclusion chromatography-infrared (SEC-IR) technique. Interference by vinyl or phenyl groups in the sample or by traces of water in the solvent was negligible, but water or compounds containing other types of hydroxyl groups interfered. Sensitivity of the method is about 10 ..mu..g of the silanol, as OH in the polydimethylsiloxane. Primary calibration was by proton nuclear magnetic resonance (PNMR) at a high concentration of hydroxyl groups.

Kohn, E.

1985-01-01

358

A comparative study of the analysis of human urine headspace using gas chromatography-mass spectrometry.  

PubMed

First-void urine samples were obtained from 24 elderly, asymptomatic men (median age 62.9 years). The headspace above pH adjusted urine samples were extracted using a carboxen/polydimethylsiloxane solid phase micro-extraction fibre and the volatile organic compounds analysed by gas chromatography/mass spectrometry. A total of 147 compounds were identified in the headspace of urine. The acidified samples recorded a total of 92 compounds, 27 of which were ubiquitous, basified samples 70 compounds, with 12 ubiquitous and unmodified pH samples 49, with 6 ubiquitous. Five compounds were ubiquitous irrespective of pH: acetone, methylene chloride, 4-heptanone, 2-pentanone and 2-butanone. A comparative analysis of unfrozen and frozen-thawed urine (stored at room temperature for 0, 1 and 8 h) showed that samples retained the same number of compounds although variations in the peak areas for some compounds were observed. PMID:21386182

Smith, S; Burden, H; Persad, R; Whittington, K; de Lacy Costello, B; Ratcliffe, N M; Probert, C S

2008-09-08

359

Multiresidue analysis of neonicotinoids by solid-phase extraction technique using high-performance liquid chromatography.  

PubMed

For routine monitoring of pesticides, a multiresidue analysis through solid-phase extraction technique and using high-performance liquid chromatography (HPLC) in cotton seed cake (CSC) has been developed. Extraction of fortified samples was carried out with aqueous acetone under vacuum. The concentrated extract was loaded onto the solid-phase extraction units, preconditioned with acetonitrile. The extraction units were then washed with hexane and finally eluted with acetonitrile. The pesticide residues were determined using a multiresidue method by reversed-phase HPLC. The average percentage recoveries were found to range between 65.47% and 110% at spiking levels of 10 to 40 mg/kg. The method developed shows a healthy rate of recovery and can successfully be utilized for the extraction and screening of neonicotinoid residues in CSC. The detection limits for imidacloprid, acetamiprid, and thiacloprid using this method were found to be 5, 10, and 20 mg/kg, respectively. PMID:19421881

Mohan, Chander; Kumar, Yogesh; Madan, Jyotsana; Saxena, Navneet

2009-05-07

360

Rapid multi-residue analysis of antibiotics in muscle by liquid chromatography-tandem mass spectrometry.  

PubMed

A way of carrying out simple and rapid multi-residue analysis of antibiotics in porcine and bovine muscle by liquid chromatography-tandem mass spectrometry (LC-MS/MS) is described. The method has previously been published as a screening method, but the scope has now been extended to quantification and confirmation. Nineteen compounds from five different classes of antibiotics, i.e. tetracyclines, sulfonamides, quinolones, (-lactams and macrolides, are included in the method. The samples are extracted by a single extraction using 70% methanol, diluted with water and injected in the LC-MS/MS. The run time is 7min per injection. About 60 samples can be analysed in 24h. By using this method the need for a separate screening step prior to confirmation is eliminated and consequently the total time from sampling to a confirmed result will be considerably reduced. Validation was performed according to Commission Decision 2002/657/EC. PMID:19286016

Granelli, K; Elgerud, Christina; Lundström, Asa; Ohlsson, Anita; Sjöberg, Pernilla

2008-08-28

361

Analysis of different beta-lactams antibiotics in pharmaceutical preparations using micellar electrokinetic capillary chromatography.  

PubMed

The potential of micellar electrokinetic capillary chromatography (MEKC) for analyzing nine beta-lactams antibiotics (cloxacillin, dicloxacillin, oxacillin, penicillin G, penicillin V, ampicillin, nafcillin, piperacillin, amoxicillin) in different pharmaceutical preparations, have been demonstrated. An experimental design strategy has been applied to optimize the main variables: pH and buffer concentration, concentration of the micellar medium, separation voltage and capillary temperature. Borate buffer (26mM) at pH 8.5 containing 100mM sodium dodecyl sulphate (SDS) was used as the background electrolyte. The method was validated. Linearity, limit of detection and quantitation and precision were established for each compound. The analysis of some of the beta-lactams in Orbenin capsules, Britapen tables and in Veterin-Micipen injectable, all used in human and veterinary medicine, have demonstrated the applicability of these technique for quality control in the pharmaceutical industry. PMID:16978821

Pérez, M I Bailón; Rodríguez, L Cuadros; Cruces-Blanco, C

2006-09-15

362

Analysis of anthocyanins in powdered berry extracts by planar chromatography linked with bioassay and mass spectrometry.  

PubMed

Major anthocyanins were extracted with acidified methanol and characterised in powdered berry extracts of bilberry, blueberry, chokeberry, açai berry and cranberry by HPTLC-Vis-MS for the first time. A combined 2-step normal phase separation was applied, first for separation of anthocyanins and secondly of anthocyanidins. Documentation was performed under white light illumination (transmission mode). In the powdered berry extracts, especially the 3-glucosides of delphinidin, cyanidin, malvidin and peonidin, further cyanidin glycosides and respective anthocyanidins were found. Calibration data revealed a good correlation, with r between 0.9988 and 0.9999. The repeatability of the sample analysis (n=3) was ?3.6%. Based on the results obtained, this method can be used for rapid routine quality control of powdered berry extracts. For confirmation of the results or characterisation of unknown anthocyanin zones, mass spectra were recorded. Chromatography was directly linked to the effect using DPPH(?) reagent and luminescent Aliivibrio fischeri bioassay. PMID:24176320

Cretu, Georgiana C; Morlock, Gertrud E

2013-09-13

363

Analysis of Monosodium l-Glutamate in Food Products by High-Performance Thin Layer Chromatography  

PubMed Central

A simple, fast, specific, and precise high-performance thin layer chromatography method has been developed for the estimation of monosodium l-glutamate (MSG) in food products. Aluminum plates precoated with silica gel 60 GF254were used as stationary phase and a mixture of methanol–chloroform–formic acid in the ratio 5:5:1 (v/v) as mobile phase. Quantification was carried out by postchromatographic derivatization using 1% ninhydrin solution, and the developed spots were scanned by using a densitometer in absorbance mode at 485 nM. The Rfvalue of MSG was 0.64. The results of the analysis have been validated statistically and by the recovery studies. Linearity was observed in the concentration range of 400–1000 nG.

Krishna, Veni N; Karthika, D; Surya, Devi M; Rubini, MF; Vishalini, M; Pradeepa, YJ

2010-01-01

364

Basic Principles of Chromatography  

NASA Astrophysics Data System (ADS)

Chromatography has a great impact on all areas of analysis and, therefore, on the progress of science in general. Chromatography differs from other methods of separation in that a wide variety of materials, equipment, and techniques can be used. [Readers are referred to references (1-19) for general and specific information on chromatography.]. This chapter will focus on the principles of chromatography, mainly liquid chromatography (LC). Detailed principles and applications of gas chromatography (GC) will be discussed in Chap. 29. In view of its widespread use and applications, high-performance liquid chromatography (HPLC) will be discussed in a separate chapter (Chap. 28). The general principles of extraction are first described as a basis for understanding chromatography.

Ismail, Baraem; Nielsen, S. Suzanne

365

Analysis of cholesterol oxidation products by Fast gas chromatography/mass spectrometry.  

PubMed

The aim of the present study was to set-up a Fast gas chromatography/mass spectrometry method for the analysis of cholesterol oxidation products (COPs). A silylated mixture of seven oxysterol standards was injected into a Fast GC/MS system. A capillary GC column (10?m×0.1?mm internal diameter×0.1??m film thickness) coated with 95% dimethyl- and 5% diphenyl-polysiloxane, was used. The method gave a fast (total analysis time=3.5?min) and satisfactory resolution (R>1.2) of the COPs standards, with a good repeatability and sensitivity, similar to those of conventional GC/MS; recoveries were tested on mice liver. Fast GC/MS method suitability for COPs analysis in food was also tested on an oxidized sardine fillet, which had been previously saponified and purified by NH(2) solid-phase extraction (SPE); a good repeatability and sensitivity was also obtained. The analytical performance of the Fast GC/MS method for the determination of COPs, together with the consequent significant reduction of the analysis time and consumables, demonstrates that Fast GC/MS represents a valid alternative to conventional GC/MS and evinces the great potential of such an analytical technique, which could be applied for both food and biological samples. PMID:22258809

Cardenia, Vladimiro; Rodriguez-Estrada, Maria T; Baldacci, Elena; Savioli, Stefano; Lercker, Giovanni

2012-02-01

366

Quantitative analysis of dimethyl titanocene by iodometric titration, gas chromatography and NMR.  

PubMed

In this study we report the use of an automated iodometric titration method and a novel gas chromatography (GC) method for the quantitative analysis of dimethyl titanocene (DMT), a key raw material in drug synthesis. Both approaches are based on the reaction of DMT in toluene or tetrahydrofuran solutions with iodine. In the case of iodometric titration, excess iodine is titrated with a standardized aqueous sodium thiosulfate solution to a potentiometric end-point for the determination of DMT concentration. Alternatively, GC is employed to measure the concentration of iodomethane, a product of the reaction between DMT and iodine, in order to determine the concentration of DMT in the solution. Excellent agreement between iodometric titration, GC and NMR results using several DMT samples confirms the accuracy of the two methods and strongly supports the use of either method as a replacement to the expensive NMR for quantitative DMT analysis. The relatively few sources of error associated with the two methods, their ubiquitous nature and ease of application in routine analysis make them the analytical methods of choice, among all. Both methods have been validated according to ICH requirements. The use of iodometric titration method for DMT analysis is demonstrated with a couple of applications. PMID:11377038

Vailaya, A; Wang, T; Chen, Y; Huffman, M

2001-06-01

367

A variational approach to multi-phase motion of gas, liquid and solid based on the level set method  

NASA Astrophysics Data System (ADS)

We propose a simple and robust numerical algorithm to deal with multi-phase motion of gas, liquid and solid based on the level set method [S. Osher, J.A. Sethian, Front propagating with curvature-dependent speed: Algorithms based on Hamilton-Jacobi formulation, J. Comput. Phys. 79 (1988) 12; M. Sussman, P. Smereka, S. Osher, A level set approach for capturing solution to incompressible two-phase flow, J. Comput. Phys. 114 (1994) 146; J.A. Sethian, Level Set Methods and Fast Marching Methods, Cambridge University Press, 1999; S. Osher, R. Fedkiw, Level Set Methods and Dynamics Implicit Surface, Applied Mathematical Sciences, vol. 153, Springer, 2003]. In Eulerian framework, to simulate interaction between a moving solid object and an interfacial flow, we need to define at least two functions (level set functions) to distinguish three materials. In such simulations, in general two functions overlap and/or disagree due to numerical errors such as numerical diffusion. In this paper, we resolved the problem using the idea of the active contour model [M. Kass, A. Witkin, D. Terzopoulos, Snakes: active contour models, International Journal of Computer Vision 1 (1988) 321; V. Caselles, R. Kimmel, G. Sapiro, Geodesic active contours, International Journal of Computer Vision 22 (1997) 61; G. Sapiro, Geometric Partial Differential Equations and Image Analysis, Cambridge University Press, 2001; R. Kimmel, Numerical Geometry of Images: Theory, Algorithms, and Applications, Springer-Verlag, 2003] introduced in the field of image processing.

Yokoi, Kensuke

2009-07-01

368

Measurement of bubble size distribution in a gas-liquid foam using pulsed-field gradient nuclear magnetic resonance.  

PubMed

Pulsed-field gradient nuclear magnetic resonance, previously used for measuring droplet size distributions in emulsions, has been used to measure bubble size distributions in a non-overflowing pneumatic gas-liquid foam that has been created by sparging propane into an aqueous solution of 1.5g/l (5.20mM) SDS. The bubble size distributions measured were reproducible and approximated a Weibull distribution. However, the bubble size distributions did not materially change with position at which they were measured within the froth. An analysis of foam coarsening due to Ostwald ripening in a non-overflowing foam indicates that, for the experimental conditions employed, one would not expect this to be a significant effect. It is therefore apparent that the eventual collapse of the foam is due to bubble bursting (or surface coalescence) rather than Ostwald ripening. This surface coalescence occurs because of evaporation from the free surface of the foam. An analytical solution for the liquid fraction profile for a certain class of non-overflowing pneumatic foam is given, and a mean bubble size that is appropriate for drainage calculations is suggested. PMID:20832808

Stevenson, Paul; Sederman, Andrew J; Mantle, Mick D; Li, Xueliang; Gladden, Lynn F

2010-08-10

369

Kinetics of gas-liquid reaction between NO and Co(NH3)6(2+).  

PubMed

Wet ammonia desulphurization process can be retrofitted for combined removal of SO2 and NO from the flue gas by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The Co(NH3)6(2+) formed by ammonia binding with Co2+ is the active constituent of scrubbing NO from the flue gas streams. A stirred vessel with a plane gas-liquid interface was used to measure the chemical absorption rates of nitric oxide into the Co(NH3)6(2+) solution under anaerobic and aerobic conditions separately. The experiments manifest that the nitric oxide absorption reaction can be regarded as instantaneous when nitric oxide concentration levels are parts per million ranges. The gas-liquid reaction becomes gas film controlling as Co(NH3)6(2+) concentration exceeds 0.02 mol/l. The NO absorption rate is proportional to the nitric oxide inlet concentration. Oxygen in the gas phase is favorable to the absorption of nitric oxide. But it is of little significance to increase the oxygen concentration above 5.2%. The NO absorption rate decreases with temperature. The kinetic equation of NO absorption into the Co(NH3)6(2+) solution under aerobic condition can be written as. PMID:15869841

Long, Xiang-li; Xiao, Wen-De; Yuan, Wei-kang

2005-08-31

370

Experimental Study of Gas-Liquid Two-Phase Flow in Glass Micromodels  

NASA Astrophysics Data System (ADS)

To estimate the most important flow variables in reservoir engineering, such as the relative permeability, it is required to know with high precision, other variables such as saturation, pressure drop of each phase, and porous media data such as porosity and absolute permeability. In this study, experimental tests were performed inside a glass micromodel using gas-liquid two-phase flow in steady-state conditions. The liquid-phase flow and the pressure drop of the porous media were determined. Additionally, the flow development inside the porous media was visualized using a high-speed video camera system. These pictures were recorded at 500 fps, and they were used to compute the phase saturation and the gas velocity in the glass micromodel. The visualization was performed in three regions of the glass micromodel demonstrating that saturation gradients were not present. The effect of the capillary number was studied over the gas-liquid relative permeability curves and on the flow mechanisms. It was concluded that high flow rates minimize edge effects, that the capillary number modifies the relative permeability values and the flow patterns inside the micromodel, and that the high-speed visualization is an efficient and accurate technique to determine saturation values and to study the flow patterns in transparent porous media such as glass micromodels.

Gutiérrez, B.; Juarez, F.; Ornelas, L.; Zeppieri, S.; de Ramos, A. López

2008-12-01

371

Gas-liquid two-phase flow through packed bed reactors in microgravity  

NASA Astrophysics Data System (ADS)

Experimental results on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed bed reactors in microgravity is presented and analyzed. The pulse flow regime is shown to exist over a much wider range of gas and liquid flow rates when under microgravity conditions. A new model is developed to predict the transition from bubble flow to pulse flow based on the dimensionless Suratman number. The Suratman number is shown to represent the balance of forces at the pore level which determine the conditions necessary for the onset of pulse flow in the column. This model is then extended to normal gravity flows in the downward direction for fixed Bond numbers. A model to predict pressure drop in the absence of gravity is also presented. An additional pressure drop term is developed to extend the applicability of the Ergun equation to gas-liquid flow. This term represents the losses resulting from the dynamic interaction between the two phases and is superposed with the liquid viscous and inertia terms to represent the total pressure loss through a reactor bed in a microgravity environment. The modified two-phase Ergun equation is shown to provide good agreement with the experimental results.

Motil, Brian Joseph

372

Evaluation of high-efficiency gas liquid contactors for natural gas processing  

SciTech Connect

The objectives of this program are to develop and evaluate advanced processing technologies that can reduce the cost of upgrading sub quality natural gas to pipeline standards. The successful application of cost-effective, new technologies will facilitate the production of sub quality natural gas that otherwise would be too expensive to produce. The overall program is focused on the following activities: evaluation of the potential of structured packing for the removal of acid gases from natural gases, and expansion of the currently available database of the fluid dynamics of rotating gas liquid contactors. The natural gas sweetening, structured packing field tests are scheduled to be conducted in calendar year 1995. Design, procurement and construction of the field test unit. Expansion of the available data base on the hydraulic characteristics of a rotating gas-liquid contactor is being pursued through a series of laboratory experiments. A 100 GPM, low pressure rotary contactor system has been assembled at IGT`s Energy Development Center to examine the fluid dynamic behavior of this type of contactor. The studies are determining the effects of liquid viscosity, liquid surface tension and operating conditions on liquid residence times and flooding limits.

Palla, N.; Lee, A.L.

1995-06-01

373

Chemical Speciation Analysis of Sports Drinks by Acid-Base Titrimetry and Ion Chromatography: A Challenging Beverage Formulation Project  

ERIC Educational Resources Information Center

|Students have standardized a sodium hydroxide solution and analyzed commercially available sports drinks by titrimetric analysis of the triprotic citric acid, dihydrogen phosphate, and dihydrogen citrate and by ion chromatography for chloride, total phosphate and citrate. These experiments are interesting examples of analyzing real-world food and…

Drossman, Howard

2007-01-01

374

Complementary use of capillary zone electrophoresis and micellar electrokinetic capillary chromatography for mutual confirmation of results in forensic drug analysis  

Microsoft Academic Search

The purpose of this work was to compare different CE separation modes, namely capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC), for the analysis of drugs of forensic interest in order to assess the mutual degree of independence and consequently the possibility of complementary use for mutual confirmation of results. A panel of drugs including caffeine, morphine, barbital,

F. Tagliaro; F. P. Smith; S. Turrina; V. Equisetto; M. Marigo

1996-01-01

375

Chemical Speciation Analysis of Sports Drinks by Acid-Base Titrimetry and Ion Chromatography: A Challenging Beverage Formulation Project  

ERIC Educational Resources Information Center

Students have standardized a sodium hydroxide solution and analyzed commercially available sports drinks by titrimetric analysis of the triprotic citric acid, dihydrogen phosphate, and dihydrogen citrate and by ion chromatography for chloride, total phosphate and citrate. These experiments are interesting examples of analyzing real-world food and…

Drossman, Howard

2007-01-01

376

Liquid chromatography\\/time-of-flight\\/mass spectrometry (LC\\/TOF\\/MS) for the analysis of emerging contaminants  

Microsoft Academic Search

In this review, we focus on the importance of unequivocally detecting emerging contaminants, as well as establishing their presence in the environment by accurate mass spectrometric measurement techniques. The environmental issue of emerging contaminants is tied to the analysis of wastewater samples using the new analytical methods of the last decade, especially liquid chromatography coupled to tandem mass spectrometry (LC\\/MS\\/MS)

E. Michael Thurman

2003-01-01

377

DEVELOPMENT OF A FINGERPRINT METHOD FOR ANIMAL HORN CLASSIFICATION BY LIQUID CHROMATOGRAPHY COUPLED WITH HIERARCHICAL CLUSTERING ANALYSIS  

Microsoft Academic Search

A validated liquid chromatography (LC) method coupled with hierarchical clustering analysis (HCA) has been established for investigating the fingerprint chromatograms of ten kinds of animal horns. The method showed good performances in terms of precision, repeatability, linearity, accuracy, and stability. The results showed that the LC fingerprint method coupled with HCA could be used to classify animal horns, which could

Rui Liu; Jin-ao Duan; Sheng Guo; Jian-ming Guo; Da-wei Qian; Yu-ping Tang

2012-01-01

378

Direct liquid sample introduction for flow injection analysis and liquid chromatography with inductively coupled argon plasma spectrometric detection  

Microsoft Academic Search

The coupling of flow injection analysis (FIA) or high-performance liquid chromatography (HPLC) techniques to inductively coupled plasma atomic emission spectrometry (ICP-AES) offers new and attractive approaches for the determination of elemental concentrations in a wide variety of sample matrices. One of the most attractive features that FIA offers is a rapid and precise means of automating sample introduction into an

Kimberly E. Lawrence; Gary W. Rice; Velmer A. Fassel

1984-01-01

379

Development of Method for Ochratoxin A Analysis in Coffee by Liquid Chromatography\\/Electrospray Tandem Mass Spectrometry  

Microsoft Academic Search

Coffee constitutes an extremely complex food matrix and has an important role in the world's economy, especially in producing and exporting countries like Brazil. High Performance Liquid Chromatography coupled to mass spectrometry with selective monitoring reaction (LC-MS\\/MS-SMR) was used for the development of a method for the analysis of ochratoxin A (OTA) in roasted coffee samples, the extraction step was

Raquel Duarte da C. C. Bandeira; Thais Matsue Uekane; Carolina Passos da Cunha; Debora Andrade; Valnei Smarçaro Cunha; Janaína M. Rodrigues

380

DETERMINATION OF VOLATILE ORGANIC COMPOUNDS IN SOILS USING EQUILIBRIUM HEADSPACE ANALYSIS AND CAPILLARY COLUMN GAS CHROMATOGRAPHY/MASS SPECTROMETRY  

EPA Science Inventory

Existing methods for determination of volatile organic compounds (VOCs) in soil matrices using the purge and trap technique with gas chromatography/mass spectrometry (GC/MS) have several problems, which include preserving sample integrity from collection to analysis and efficient...

381

Computer-assisted high-performance liquid chromatography method development with applications to the isolation and analysis of phytoplankton pigments  

Microsoft Academic Search

We used chromatography modeling software to assist in HPLC method development, with the goal of enhancing separations through the exclusive use of gradient time and column temperature. We surveyed nine stationary phases for their utility in pigment purification and natural sample analysis. For purification, a complex algal matrix was separated on an efficient monomeric column, from which partially purified fractions

Laurie Van Heukelem; Crystal S Thomas

2001-01-01

382

Differentiation of Mycobacterium genavense and Mycobacterium simiae by automated mycolic acid analysis with high-performance liquid chromatography.  

PubMed Central

Mycobacterium genavense, a fastidious opportunist in patients with AIDS, cannot be identified by conventional biochemical methods. Computerized mycolic acid analysis by high-performance liquid chromatography offers an alternative that distinguishes the mycolic acid profile of M. genavense from those of all other organisms in the database developed at the Centers for Disease Control and Prevention.

Ritter, D; Carlson, L D; Logan, B K; Ramos, L S; Kilburn, J O; Coyle, M B

1996-01-01

383

Lipid methodology — Chromatography and beyond. Part I. GC\\/MS and LC\\/MS of glycerolipids  

Microsoft Academic Search

This paper reviews recent examples of the application of combined high temperature gas-liquid chromatography (GLC) and reversed\\u000a phase high pressure liquid chromatography (HPLC) with electron impact and chemical ionization mass spectrometry for structural\\u000a studies of natural diacyl and triacylglycerols. It was concluded that the combination of reversed phase HPLC with direct liquid\\u000a inlet chemical ionization mass spectrometry provides the most

A. Kuksis; J. J. Myher; L. Marai

1984-01-01

384

Gas chromatography-olfactometry analysis of the volatile compounds of two commercial Irish beef meats  

Microsoft Academic Search

The volatile flavour compounds of two commercial Irish beef meats (labelled as conventional and organic) were evaluated by gas chromatography-olfactometry and were identified by gas chromatography-mass spectrometry. The volatile compounds were isolated in a model mouth system. Gas chromatography-olfactometry was performed by a group of eight assessors using the detection frequency methodology. The odours of the detected compounds were described

David Machiels; Saskia M. van Ruth; Maarten A. Posthumus; Louis Istasse

2003-01-01

385

Chirospecific analysis of plant volatiles  

NASA Astrophysics Data System (ADS)

Characteristic features of the analysis of plant volatiles by enantioselective gas (gas-liquid) chromatography and gas chromatography/mass spectrometry are discussed. The most recent advances in the design of enantioselective stationary phases are surveyed. Examples of the preparation of the most efficient phases based on modified cyclodextrins are given. Current knowledge on the successful analytical resolution of different types of plant volatiles (aliphatic and aromatic compounds and mono-, sesqui- and diterpene derivatives) into optical antipodes is systematically described. Chiral stationary phases used for these purposes, temperature conditions and enantiomer separation factors are summarised. Examples of the enantiomeric resolution of fragrance compounds and components of plant extracts, wines and essential oils are given.

Tkachev, A. V.

2007-10-01

386

Identification of Dactylopius cochineal species with high-performance liquid chromatography and multivariate data analysis.  

PubMed

Identification of American cochineal species (Dactylopius genus) can provide important information for the study of historical works of art, entomology, cosmetics, pharmaceuticals and foods. In this study, validated species of Dactylopius, including the domesticated cochineal D. coccus, were analysed by high-performance liquid chromatography with a diode array detector (HPLC-DAD) and submitted to multivariate data analysis, in order to discriminate the species and hence construct a reference library for a wide range of applications. Principal components analysis (PCA) and partial least squares discriminant analysis (PLSDA) models successfully provided accurate species classifications. This library was then applied to the identification of 72 historical insect specimens of unidentified species, mostly dating from the 19th century, and belonging to the Economic Botany Collection, Royal Botanic Gardens, Kew, England. With this approach it was possible to identify anomalies in how insects were labelled historically, as several of them were revealed not to be cochineal. Nevertheless, more than 85% of the collection was determined to be species of Dactylopius and the majority of the specimens were identified as D. coccus. These results have shown that HPLC-DAD, in combination with suitable chemometric methods, is a powerful approach for discriminating related cochineal species. PMID:23961534

Serrano, Ana; Sousa, Micaela; Hallett, Jessica; Simmonds, Monique S J; Nesbitt, Mark; Lopes, João A

2013-10-21

387

Rapid Separation, Identification and Analysis of Astragalus membranaceus Fisch Using Liquid Chromatography-Tandem Mass Spectrometry.  

PubMed

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) method has been developed for the rapid separation and structural identification of constituents in Astragali Radix (AR) The analysis was conducted on an ACQUITY HPLC chromatographic instrument and a mass spectrometer using positive electrospray ionization. Using a fast HPLC system with an ACQUITY HPLC BEH C18 column, the total analysis time for this complex herb was less than 30 min. The method used a column with 1.7 µm particle packing, which allowed a higher speed of analysis, peak capacity, greater resolution and increased sensitivity. With various fragmentor voltage levels in MS, accurate mass measurements (less than 5 ppm error) for molecular ions and characteristic fragment ions represented reliable identification criteria for these compounds. The constituents of AR were identified or tentatively characterized based on their retention times, mass fragmentation behavior, MS-MS fragment ions, literature reports and the establishment of an in-house molecular formula database. With this method, a total of 22 compounds of AR were tentatively identified based on MS data and comparison with available databases. In conclusion, fast HPLC with MS is a highly useful and efficient technique to separate and identify constituents in complex matrices of herbal medicines. PMID:23519564

Du, Hong-Wei; Zhao, Xin-Lei; Zhang, Ai-Hua; Yao, Lin; Zhang, Yan-Yan

2013-03-21

388

Application of polydivinylbenzene liquid chromatography columns to remove lipid material from fish tissue extracts for the analysis of semivolatile organics.  

PubMed

Liquid chromatography columns of 100% polydivinylbenzene (DVB) (packing) were used to remove lipid material from fish extracts before analysis of several semivolatile organic pollutants by gas chromatography-mass spectrometry (GC-MS). This packing material was found to be durable as the columns could be operated to about 900 p.s.i. resulting in high efficiency separation. Recoveries and relative standard deviations for 18 polynuclear aromatic hydrocarbons fortified into a fish extract and cleaned up by multiple DVB columns in series were in the range of 86 to 123% and 4 to 11%, respectively. PMID:10574216

Dodo, G H; Knight, M M

1999-10-29

389

Technical advance: simultaneous analysis of metabolites in potato tuber by gas chromatography-mass spectrometry.  

PubMed

A new method is presented in which gas chromatography coupled to mass spectrometry (GC-MS) allows the quantitative and qualitative detection of more than 150 compounds within a potato tuber, in a highly sensitive and specific manner. In contrast to other methods developed for metabolite analysis in plant systems, this method represents an unbiased and open approach that allows the detection of unexpected changes in metabolite levels. Although the method represents a compromise for a wide range of metabolites in terms of extraction, chemical modification and GC-MS analysis, for 25 metabolites analysed in detail the recoveries were found to be within the generally accepted range of 70-140%. Further, the reproducibility of the method was high: the error occurring in the analysis procedures was found to be less than 6% for 30 out of 33 compounds tested. Biological variability exceeded the systematic error of the analysis by a factor of up to 10. The method is also suited for upscaling, potentially allowing the simultaneous analysis of a large number of samples. As a first example this method has been applied to soil- and in vitro-grown tubers. Due to the simultaneous analysis of a wide range of metabolites it was immediately apparent that these systems differ significantly in their metabolism. Furthermore, the parallel insight into many pathways allows some conclusions to be drawn about the underlying physiological differences between both tuber systems. As a second example, transgenic lines modified in sucrose catabolism or starch synthesis were analysed. This example illustrates the power of an unbiased approach to detecting unexpected changes in transgenic lines. PMID:10929108

Roessner, U; Wagner, C; Kopka, J; Trethewey, R N; Willmitzer, L

2000-07-01

390

Analysis of lipid particles from yeast.  

PubMed

Quantitative analysis of components from different subcellular fractions is a key to the understanding of metabolic function as well as to the origin, the biogenesis, and the crosstalk of organelles. The yeast is an excellent model organism to address such questions from the biochemical, molecular biological, and cell biological viewpoints. A yeast organelle which gained much interest during the last decade is the lipid particle/droplet (LP), a storage compartment for nonpolar lipids but at the same time an organelle actively contributing to cellular metabolism. In this chapter, we describe methods and techniques that are commonly used to analyze lipids from LP at the molecular level by thin-layer chromatography, gas-liquid chromatography, and mass spectrometry. We provide an easy to follow guideline for the isolation of these organelles, the qualitative and quantitative analysis of lipid components and show results obtained with these methods. PMID:19763485

Connerth, Melanie; Grillitsch, Karlheinz; Köfeler, Harald; Daum, Günther

2009-01-01

391

Analysis of 18 perfluorinated compounds in river waters: comparison of high performance liquid chromatography-tandem mass spectrometry, ultra-high-performance liquid chromatography-tandem mass spectrometry and capillary liquid chromatography-mass spectrometry.  

PubMed

In this work, the performance of ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and capillary liquid chromatography-mass spectrometry (CLC-MS) has been studied for the analysis of eighteen perfluorinated compounds in water samples. UHPLC-MS/MS and CLC-MS analysis were carried out using a Zorbax C-18 column (50 mm × 2.1 mm, 1.8 ?m) and a Zorbax SB-C18 column (150 mm × 0.5 mm, 3.5 ?m), respectively, in gradient elution mode with a mobile phase of ammonium formate and methanol. Both techniques were compared with conventional LC-MS/MS in terms of speed, sensitivity, selectivity and resolution. Water samples were extracted by solid phase extraction (SPE). Mean absolute recoveries at two concentration levels, 6 and 60 ng L?¹, calculated from the eighteen compounds were: 77 ± 12(s) and 82 ± 12(s), respectively. Relative standard deviation (RSD) was lower than 16% for each perfluorinated compound. The results obtained showed that UHPLC-MS/MS and CLC-MS allow the determination of perfluorinated compounds in water samples with satisfactory sensitivity and resolution and reduced analysis time. Therefore, both techniques were employed for the analysis of water samples to determine the target analytes at low concentration levels and with lower analysis times than using HPLC-MS/MS. Similar statistical values were obtained from both techniques at 95% confidence level. Several compounds have been detected, but perfluorooctanoic acid (PFOA) (171 ng L?¹ and 148 ng L?¹ by UHPLC-MS/MS and CLC-MS, respectively) showed the highest concentration. PMID:22633866

Onghena, Matthias; Moliner-Martinez, Y; Picó, Yolanda; Campíns-Falcó, P; Barceló, Damià

2012-05-08

392

Processing of Aroma Chemicals and Fragrance Materials, Socialist Republic of Viet Nam. Technical Report: Application of Gas Liquid Chromatography.  

National Technical Information Service (NTIS)

Vietnam has been a producer of natural essential oils. The government through the agency of UNDP and UNIDO has provided the industry with R & D backup in the form of a project titled: Processing of Vietnamese essential oils and related natural products. T...

M. L. Maheshwari

1992-01-01

393

Determination of neutral and acidic sugars in soil by capillary gas-liquid chromatography after trifluoroacetic acid hydrolysis  

Microsoft Academic Search

A new method for the simultaneous, quantitative determination of neutral and acidic sugars liberated from non-cellulosic soil carbohydrates is described. A single hydrolytic step with 4 M trifluoroacetic acid (TFA) at 105°C for 4 h is suggested to be more effective in releasing sugar monomers from soil than other recommended hydrolysis procedures (2.5 M H2SO4 reflux for 20 min followed

Wulf Amelung; Martin V. Cheshire; Georg Guggenberger

1996-01-01

394

Analyses of pecan, peanut, and other oils by gas-liquid chromatography and ultra-violet spectrophotometry  

Microsoft Academic Search

Comparative analyses of oils obtained from 12 varieties of pecans, 11 of peanuts, two of avocados and one each of citrus seed,\\u000a Wesson oil, corn, and of lard by GLC and UV procedures showed good agreement except for Wesson oil, corn oil, and lard. Iodine\\u000a values computed from GLC results checked Wijs values closely. Oleic acid ranged from 51 to

R. B. French

1962-01-01

395

Flow characteristics of gas–liquid two phase plunging jet absorber–gas holdup and bubble penetration depth  

Microsoft Academic Search

A gas-liquid two phase plunging jet is formed through a gas sucking type multi-jet ejector nozzle. In this study, the effects\\u000a of various conditions in the multi-jet ejector nozzle, the column diameter, and the liquid jet length on penetration depth\\u000a of air bubblesl\\u000a \\u000a B\\u000a and gas holdup hG in a gas-liquid two phase plunging jet absorber were studied experimentally. Consequently,

Mitsuharu Ide; Hiroki Uchiyama; Toshifumi Ishikura

1999-01-01

396

On-line analysis of volatile organics in water using head space gas chromatography: evaluation of five head space techniques  

Microsoft Academic Search

Many industrial effluent streams require monitoring for volatile organic carbon (VOC) at part per billion concentration levels. Head-space gas chromatography (GC) is a suitable on-line technique for this analysis (the VOCs are stripped from the water prior to analysis by GC). This paper evaluates five dynamic head-space systems for sensitivity, linearity, response time and simplicity. One of the head-space systems

Don Schieck; Fred Brown

1996-01-01

397

Rapid analysis of a Chinese herbal prescription by liquid chromatography–time-of-flight tandem mass spectrometry  

Microsoft Academic Search

A rapid method, using liquid chromatography coupled with time-of-flight tandem mass spectrometry was developed for the analysis of Chinese herbal prescription. The analysis was performed on a Waters UPLC BEH C18 column using gradient elution system. A hybrid quadrupole time-of-flight analyzer was used for the determination of accurate mass of the protonated or deprotonated molecule and fragment ion. The constituents

Xintian Zheng; Peiying Shi; Yiyu Cheng; Haibin Qu

2008-01-01

398

Rapid, quantitative analysis of americium, curium and plutonium isotopes in Hanford samples using extraction chromatography and precipitation plating  

Microsoft Academic Search

Recently developed methods for the rapid, quantitative analysis of americium (Am), curium (Cm), and plutonium (Pu) isotopes in Hanford soil, sludge, and waste-tank samples are described. After dissolution, dilutions are made as necessary based on alpha-energy analysis of a small aliquot of the original solution. Isotopic tracers are then added and Am-Cm and Pu are separated by extraction chromatography, coprecipitated

J. H. Kaye; R. S. Strebin; R. D. Orr

1995-01-01

399

Townsend discharge nitric oxide chemical ionization gas chromatography/mass spectrometry for hydrocarbon analysis of the middle distillates  

SciTech Connect

Hydrocarbon type analysis of petroleum distillates (350-860 {degrees}F fraction) was performed using Townsend discharge nitric acid chemical ionization gas chromatography/mass spectrometry (TDNOCI GC/MS). Both n and z in the chemical formula, C{sub n}H{sub 2n + z} can be determined. GC separation allows quantification of heteroatom compounds in the presence of aromatics of the same mass. Results are presented for the analysis of feedstocks and hydrotreated products.

Dzidic, I.; Petersen, H.A.; Wadsworth, P.A.; Hart, H.V. [Westhollow Research Center, Houston, TX (United States)

1992-10-01

400

Analysis of volatile components in Curcuma rhizome by microemulsion electrokinetic chromatography.  

PubMed

Volatile chemicals are a group of very important compounds in natural products. Curcuma rhizome, which contains many bioactive volatile compounds, is a traditional Chinese medicine that has long been used for the treatment of several diseases. In the present study, a microemulsion electrokinetic chromatography (MEEKC) method was developed for the analysis of four volatile components in Curcuma rhizome, including germacrone, furanodiene, curcumenol and curdione. Experimental parameters, including the pH, type and concentrations of background electrolyte, and microemulsion compositions (type and concentrations of surfactant, co-surfactant and oil phase) were intensively investigated. Finally, the primary compounds in the methanol extract of Curcuma rhizome were separated within 30 min using a running buffer composed of 2.31% w/v (80 mmol/L) sodium dodecyl sulfate (SDS), 0.91% w/v (80 mmol/L) 1-octane, 6.95% w/v (937.5 mmol/L) 1-butanol and 1.88% w/v (312.5 mmol/L) propanol in a 5-mM borate buffer (pH 8.1). The contents of the four investigated compounds were determined in the rhizome from C. phaeocaulis. The results showed that the developed MEEKC method provided an alternative tool for the analysis of volatile components, especially those of heat-sensitive compounds from natural products. PMID:22824329

Yang, Feng-Qing; Yang, Jing; Zhang, Xue-Mei; Xu, Pan; Xia, Zhi-Ning

2012-07-23

401

Trace analysis of sulfamethazine in animal feed, human urine, and wastewater by electron capture gas chromatography  

SciTech Connect

Sulfamethazine, a widely used antibacterial drug additive in feeds for swine, chickens, and cattle, was scheduled for toxicological evaluation because of potential human health hazards associated with its residues in edible animal tissues. Analytical chemical procedures that would ensure proper concentration, homogeneity, and stability of the drug in dosed feed and its safe usage during the animal studies were prerequisites for such toxicological tests. Electron capture gas chromatographic (EC/GC) methods were therefore devised for the analysis of sulfamethazine residues in animal feed, human urine, and wastewater at levels as low as 100, 10, and 10 ppb, respectively. Sample extracts were cleaned up by using liquid/liquid partitioning, and the extracts were subjected to two derivatizations followed by cleanup on a silica gel column. The derivatizations of sulfamethazine consisted of methylation followed by trifluoroacetylation of the primary amine function. Ancillary data concerning stability of the compound in animal feed, water, and as a dry residue on glass, extraction efficiencies, partition values with various solvents, and the analysis of residues in feed by high pressure liquid chromatography (HPLC) at levels as low as 1.0 ppm are presented.

Holder, C.L.; Thompson, H.C. Jr.; Bowman, M.C.

1981-12-01

402

Ultra Performance Liquid Chromatography and High Resolution Mass Spectrometry for the Analysis of Plant Lipids  

PubMed Central

Holistic analysis of lipids is becoming increasingly popular in the life sciences. Recently, several interesting, mass spectrometry-based studies have been conducted, especially in plant biology. However, while great advancements have been made we are still far from detecting all the lipids species in an organism. In this study we developed an ultra performance liquid chromatography-based method using a high resolution, accurate mass, mass spectrometer for the comprehensive profiling of more than 260 polar and non-polar Arabidopsis thaliana leaf lipids. The method is fully compatible to the commonly used lipid extraction protocols and provides a viable alternative to the commonly used direct infusion-based shotgun lipidomics approaches. The whole process is described in detail and compared to alternative lipidomic approaches. Next to the developed method we also introduce an in-house developed database search software (GoBioSpace), which allows one to perform targeted or un-targeted lipidomic and metabolomic analysis on mass spectrometric data of every kind.

Hummel, Jan; Segu, Shruthi; Li, Yan; Irgang, Susann; Jueppner, Jessica; Giavalisco, Patrick

2011-01-01

403

High-resolution fractionation after gas chromatography for effect-directed analysis.  

PubMed

This research presents an analytical technology for highly efficient, high-resolution, and high-yield fractionation of compounds after gas chromatography (GC) separations. The technology is straightforward, does not require sophisticated cold traps or adsorbent traps, and allows collecting large numbers of fractions during a GC run. The technology is based on direct infusion of a carrier solvent at the end of the GC column, where infusion takes place in the GC oven. Pentane and hexane used as carrier solvent showed good results. Acetonitrile also showed good results as a more polar carrier solvent. Development and optimization of the technology is described, followed by demonstration in a high-throughput effect directed analysis setting toward dioxin receptor bioactivity. The GC fractionation setup was capable of collecting fractions in the second range. As a result, fractionated compounds could be collected into one or two fractions when 6.5 s resolution fractionation was performed. Subsequently, mixtures containing polycyclic aromatic hydrocarbons, of which some are bioactive toward the dioxin receptor, were profiled with a mammalian gene reporter assay. After fractionation into 96-well plates, we used our new approach for direct cell seeding onto the fractions prior to assaying which allowed dioxin receptor bioactivity to be measured directly after fractionation. The current technology represents a great advance in effect directed analysis for environmental screening worldwide as it allows combining the preferred analytical separation technology for often non-polar environmental pollutants with environmentally relevant bioassays, in high resolution. PMID:23919657

Pieke, Eelco; Heus, Ferry; Kamstra, Jorke H; Mladic, Marija; van Velzen, Martin; Kamminga, Dik; Lamoree, Marja H; Hamers, Timo; Leonards, Pim; Niessen, Wilfried M A; Kool, Jeroen

2013-08-22

404

Two-phase electromembrane extraction followed by gas chromatography-mass spectrometry analysis.  

PubMed

A two-phase electromembrane extraction (EME) was developed and directly coupled with gas chromatography mass spectrometry (GC-MS) analysis. The proposed method was successfully applied to the simultaneous determination of imipramine, desipramine, citalopram and sertraline. The model compounds were extracted from neutral aqueous sample solutions into the organic phase filled in the lumen of the hollow fiber. This method was accomplished with 1-heptanol as organic phase, by means of 60 V applied voltage and with the extraction time of 15 min. Experiments reported recoveries in the range of 69-87% from 1.2 mL neutral sample solution. The compounds were quantified by GC-MS instrument, with acceptable linearity ranging from 1 to 500 ng mL(-1) (R(2) in the range of 0.989 to 0.998), and repeatability (RSD) ranging between 7.5 and 11.5% (n = 5). The estimated detection limits (S/N ratio of 3:1) were less than 0.25 ng mL(-1). This novel approach based on two-phase EME brought advantages such as simplicity, low-costing, low detection limit and fast extraction with a total analysis time less than 25 min. These experimental findings were highly interesting and demonstrated the possibility of solving ionic species in the organic phase at the presence of electrical potential. PMID:23339011

Davarani, Saied Saeed Hosseiny; Morteza-Najarian, Amin; Nojavan, Saeed; Pourahadi, Ahmad; Abbassi, Mojtaba Beigzadeh

2013-01-22

405

Phthalate analysis by gas chromatography-mass spectrometry: blank problems related to the syringe needle.  

PubMed

For the analysis of the most commonly encountered phthalates by gas chromatography-mass spectrometry (GC-MS), absorption of phthalates from the laboratory air on the outer wall of the syringe needle is shown to be an important contribution to the blank problems. It was investigated for programmed temperature vapourizing (PTV) injection. Cleaning of the needle in automated injection is of modest efficiency, since the needle cannot be immersed deeply enough into the wash vial. Two approaches were studied to minimize the transfer into the column: (i) cleaning of the needle in the injector prior to splitless injection by inserting the needle in split mode while the precolumn is backflushed, which presupposes a high injector temperature to be efficient; (ii) injection under conditions minimizing thermal desorption from the needle wall, i.e. fast injection at low injector temperature (e.g. 40 °C). Both approaches resulted in blank levels of around 0.1 pg for diisobutyl phthalate (DIBP) and dibutyl phthalate (DBP), and of around 1 pg for di(2-ethylhexyl) phthalate (DEHP). They could be useful tools in existing or future methods for the analysis of phthalates or other compounds causing blank problems through contamination of the laboratory air. PMID:23265992

Marega, Milena; Grob, Konrad; Moret, Sabrina; Conte, Lanfranco

2012-12-03

406

Ultra performance liquid chromatography tandem mass spectrometry performance evaluation for analysis of antibiotics in natural waters.  

PubMed

An ultra performance liquid chromatography electrospray tandem mass spectrometry (UPLC/MS/MS) method was developed and validated for the determination of 17 antibiotics in natural waters in one single extraction and chromatographic procedure. Gradient separation conditions were optimised for 17 compounds belonging to five different antibiotic groups: quinolones (oxolinic acid, nalidixic acid, pipemidic acid, flumequine), fluoroquinolones (enoxacin, ciprofloxacin, norfloxacin, ofloxacin, enrofloxacin, sarafloxacin, danofloxacin, difloxacin, lomefloxacin), sulphonamides (sulphamethoxazole, sulphamethazine), nitro-imidazole (ornidazole) and diaminopyrimidine (trimethoprim). The separation of all compounds, obtained using a 1.7 microm particle size column (100 mm x 2.1 mm), was achieved within 10 min time. Water samples were adjusted to pH 7 and extracted using Oasis hydrophilic-lipophilic balance (HLB) solid phase extraction cartridges. After elution with methanol and concentration, extracts were injected in a C18 column (Acquity UPLC BEH C18) and detected by tandem mass spectrometry. Average recovery from 100 ng L(-1) fortified samples was higher than 70% for most of the compounds, with relative standard deviations below 20%. Performances of the method (recoveries, detection limit, quantification limit and relative standard deviation) and matrix effects were studied, and results obtained showed that method was suitable for routine analysis of antibiotics in surface water. Samples analysis from Seine River (France) confirmed the interest of antibiotic contamination evaluation in that area. PMID:19148627

Tamtam, Fatima; Mercier, Fabien; Eurin, Joëlle; Chevreuil, Marc; Le Bot, Barbara

2009-01-16

407

Hyphenation of optimized microfluidic sample preparation with nano liquid chromatography for faster and greener alkaloid analysis.  

PubMed

A glass liquid-liquid extraction (LLE) microchip with three parallel 3.5cm long and 100?m wide interconnecting channels was optimized in terms of more environmentally friendly (greener) solvents and extraction efficiency. In addition, the optimized chip was successfully hyphenated with nano-liquid chromatography with ultraviolet and mass spectrometric detection (nanoLC-UV-MS) for on-line analysis. In this system, sample pretreatment, separation and detection are integrated, which significantly shortens the analysis time, saves labor and drastically reduces solvent consumption. Strychnine was used as model analyte to determine the extraction efficiency of the optimized 3-phase chip. Influence of organic solvent, pH of feed phase, type of alkaloid, and flow rates were investigated. The results demonstrated that the 3-phase chip nanoLC-UV/MS hyphenation combines rapid (?25s) and efficient (extraction efficiency >90%) sample prep, with automated alkaloid analyses. The method was applied to real samples including Strychnos nux-vomica seeds, Cephaelis ipecacuanha roots, Atropa belladonna leaves, and Vinca minor leaves. PMID:24050669

Shen, Yao; van Beek, Teris A; Zuilhof, Han; Chen, Bo

2013-08-27

408

Collection of airborne fluorinated organics and analysis by gas chromatography/chemical ionization mass spectrometry.  

PubMed

The ubiquitous detection of perfluorooctane sulfonate (PFOS) in humans and animals has produced a need for sensitive and compound-specific analytical methods to determine the environmental distribution of fluorinated organic contaminants. A suite of potential PFOS precursors (sulfonamides) and fluorotelomer alcohols (FTOHs) were separated by gas chromatography and detected by chemical ionization mass spectrometry (GC/CI-MS). Full-scan spectra were collected in both positive and negative chemical ionization (PCI and NCI, respectively) mode to determine retention time windows and fragmentation patterns. In selected ion monitoring (SIM) mode, instrumental detection limits ranged from 0.2 to 20 pg for individual analytes, depending on ionization mode. PCI mode was preferred for routine analysis because of the simple mass spectra produced, typified by the presence of a major molecular ion [M + H]+. High-volume air samplers collected gaseous and particle-bound fluoroorganics on composite media consisting of XAD-2, polyurethane foam (PUF), and quartz-fiber filters. The combined collection efficiency for individual analytes was 87 to 136% in breakthrough experiments. Application of the method to the analysis of ambient air from urban and rural sites confirmed the presence of six novel fluorinated atmospheric contaminants at picogram per meter3 concentrations. Low concentrations of fluoroorganics were consistently detected in blanks (<4 pg m(-3)); however, this did not prevent confirmation or quantification of environmental concentrations. PMID:11842814

Martin, Jonathan W; Muir, Derek C G; Moody, Cheryl A; Ellis, David A; Kwan, Wai Chi; Solomon, Keith R; Mabury, Scott A

2002-02-01

409

Analysis of imazaquin in soybeans by solid-phase extraction and high-performance liquid chromatography.  

PubMed

An analytical method for the determination imazaquin residues in soybeans was developed. The developed liquid/liquid partition and strong anion exchange solid-phase extraction procedures provide the effective cleanup, removing the greatest number of sample matrix interferences. By optimizing mobile-phase pH water/acetonitrile conditions with phosphoric acid, using a C-18 reverse-phase chromatographic column and employing ultraviolet detection, excellent peak resolution was achieved. The combined cleanup and chromatographic method steps reported herein were sensitive and reliable for determining the imazaquin residues in soybean samples. This method is characterized by recovery >88.4%, precision <6.7% CV, and sensitivity of 0.005 ppm, in agreement with directives for method validation in residue analysis. Imazaquin residues in soybeans were further confirmed by high performance liquid chromatography-mass spectrometry (LC-MS). The proposed method was successfully applied to the analysis of imazaquin residues in soybean samples grown in an experimental field after treatments of imazaquin formulation. PMID:18183337

Guo, C; Hu, J-Y; Chen, X-Y; Li, J-Z

2008-01-09

410

Post-column labeling techniques in amino acid analysis by liquid chromatography.  

PubMed

Amino acid analysis (AAA) has always presented an analytical challenge in terms of sample preparation, separation, and detection. Because of the vast number of amino acids, various separation methods have been applied taking into consideration the large differences in their chemical structures, which span from nonpolar to highly polar side chains. Numerous separation methods have been developed in the past 60 years, and impressive achievements have been made in the fields of separation, derivatization, and detection of amino acids (AAs). Among the separation methods, liquid chromatography (LC) prevailed in the AAA field using either pre-column or post-column labeling techniques in order to improve either separation of AAs or selectivity and sensitivity of AAA. Of the two approaches, the post-column technique is a more rugged and reproducible method and provides excellent AAs separation relatively free from interferences. This review considers current separations combined with post-column labeling techniques for AAA, comparison with the pre-column methods, and the strategies used to develop effective post-column methodology. The focus of the article is on LC methods coupled with post-column labeling techniques and studying the reactions to achieve optimum post-column derivatization (PCD) conditions in order to increase sensitivity and selectivity using various types of detectors (UV-Vis, fluorescence, electrochemical etc.) and illustrating the versatility of the PCD methods for practical analysis. PMID:24013667

Rigas, Pantelis G

2013-09-08

411

Proteomic analysis of the organ of corti using nanoscale liquid chromatography coupled with tandem mass spectrometry.  

PubMed

The organ of Corti (OC) in the cochlea plays an essential role in auditory signal transduction in the inner ear. For its minute size and trace amount of proteins, the identification of the molecules in pathophysiologic processes in the bone-encapsulated OC requires both delicate separation and a highly sensitive analytical tool. Previously, we reported the development of a high resolution metal-free nanoscale liquid chromatography system for highly sensitive phosphoproteomic analysis. Here this system was coupled with a LTQ-Orbitrap XL mass spectrometer to investigate the OC proteome from normal hearing FVB/N male mice. A total of 628 proteins were identified from six replicates of single LC-MS/MS analysis, with a false discovery rate of 1% using the decoy database approach by the OMSSA search engine. This is currently the largest proteome dataset for the OC. A total of 11 proteins, including cochlin, myosin VI, and myosin IX, were identified that when defective are associated with hearing impairment or loss. This study demonstrated the effectiveness of our nanoLC-MS/MS platform for sensitive identification of hearing loss-associated proteins from minute amount of tissue samples. PMID:22942697

Peng, Hong; Liu, Miao; Pecka, Jason; Beisel, Kirk W; Ding, Shi-Jian

2012-07-02

412

Global Analysis of the Membrane Subproteome of Pseudomonas aeruginosa using Liquid Chromatography-Tandem Mass Spectrometry  

SciTech Connect

Pseudomonas aeruginosa is one of the most significant opportunistic bacterial pathogens in humans causing infections and premature death in patients with cystic fibrosis, AIDS, severe burns, organ transplants or cancer. Liquid chromatography coupled online with tandem mass spectrometry (LC-MS/MS) was used for the large-scale proteomic analysis of the P. aeruginosa membrane subproteome. Concomitantly, an affinity labeling technique, using iodoacetyl-PEO biotin to tag cysteinyl-containing proteins, permitted the enrichment and detection of lower abundance membrane proteins. The application of these approaches resulted in the identification of 786 proteins. A total of 333 proteins (42%) had a minimum of one transmembrane domain (TMD; ranging from 1 to 14) and 195 proteins were classified as hydrophobic based on their positive GRAVY values (ranging from 0.01 to 1.32). Key integral inner and outer membrane proteins involved in adaptation and antibiotic resistance were conclusively identified, including the detection of 53% of all predicted opr-type porins (outer integral membrane proteins) and all the components of the mexA-mexB-oprM transmembrane protein complex. This work represents the most comprehensive qualitative proteomic analysis of the membrane subproteome of P. aeruginosa and for prokaryotes in general to date.

Blonder, Josip; Goshe, Michael B.; Xiao, Wenzhong; Camp, David G.; Wingerd, Mark A.; Davis, Ronald W.; Smith, Richard D.

2004-05-30

413

[Analysis of aliphatic carboxylic acids in anaerobic digestion process waters by ion-exclusion chromatography].  

PubMed

The analysis of seven aliphatic carboxylic acids (formic, acetic, propionic, iso-butyric, n-butyric, iso-valeric and n-valeric acid) in anaerobic digestion process waters for biogas production was examined by ion-exclusion chromatography with dilute acidic eluents (benzoic acid, perfluorobutyric acid (PFBA) and sulfuric acid) and non-suppressed conductivity/ultraviolet (UV) detection. The columns used were a styrene/divinylbenzene-based strongly acidic cation-exchange resin column (TSKgel SCX) and a polymethacrylate-based weakly acidic cation-exchange resin column (TSKgel Super IC-A/C). Good separation was performed on the TSKgel SCX in shorter retention times. For the TSKgel Super IC-A/C, peak shape of the acids was sharp and symmetrical in spite of longer retention times. In addition, the mutual separation of the acids was good except for iso- and n-butyric acids. The better separation and good detection was achieved by using the two columns (TSKgel SCX and TSKgel Super IC-A/C connected in series), lower concentrations of PFBA and sulfuric acid as eluents, non-suppressed conductivity detection and UV detection at 210 nm. This analysis was applied to anaerobic digestion process waters. The chromatograms with conductivity detection were relatively simpler compared with those of UV detection. The use of two columns with different selectivities for the aliphatic carboxylic acids and the two detection modes was effective for the determination and identification of the analytes in anaerobic digestion process waters containing complex matrices. PMID:22799193

Ito, Kazuaki; Sakamoto, Jun; Nagaoka, Kazuya; Takayama, Yohichi; Kanahori, Takashi; Sunahara, Hiroshi; Hayashi, Tsuneo; Sato, Shinji; Hirokawa, Takeshi; Tanaka, Kazuhiko

2012-04-01

414

Two-column sequential injection chromatography--new approach for fast and effective analysis and its comparison with gradient elution chromatography.  

PubMed

This work presents novel approach in low-pressure chromatography flow systems--two-column Sequential Injection Chromatography (2-C SIC) and its comparison with gradient elution chromatography on the same instrument. The system was equipped with two different chromatographic columns (connected to selection valve in parallel design) for isocratic separation and determination of all components in composed anti-inflammatory pharmaceutical preparation (tablets). The sample was first injected on the first column of length 30 mm where less retained analytes were separated and then the sample was injected on the second column of length 10 mm where more retained analytes were separated. The SIC system was based on a commercial SIChrom manifold (8-port high-pressure selection valve and medium-pressure syringe pump with 4 mL reservoir) (FIAlab, USA) with two commercially available monolithic columns the "first column" Chromolith Flash RP-18e (25 mm x 4.6 mm i.d. with guard column 5 mm x 4.6 mm i.d.) and the "second column" Chromolith RP-18e (10 mm x 4.6 mm i.d.) and CCD UV-vis detector USB 4000 with micro-volume 1.0 cm Z flow cell. Two mobile phases were used for analysis (one for each column). The mobile phase 1 used for elution of paracetamol, caffeine and salicylic acid (internal standard) was acetonitrile/water (10:90, v/v, the water part of pH 3.5 adjusted with acetic acid), flow rate was 0.9 mL min(-1) (volume 3.0 mL of mobile phase per analysis). The mobile phase 2 used for elution of propyphenazone was acetonitrile/water (30:70, v/v); flow rate was 1.2 mL min(-1) (volume 1.5 mL of mobile phase per analysis). Absorbance was monitored at 210 nm. Samples were prepared by dissolving of one tablet in 30% acetonitrile and 10 microL of filtered supernatant was injected on each column (2 x 10 microL). The chromatographic resolution between all compounds was >1.45 and analysis time was 5.5 min under the optimal conditions. Limits of detection were determined at 0.4 microg mL(-1) for paracetamol, at 0.5 microg mL(-1) for caffeine and at 0.7 microg mL(-1) for propyphenazone. The new two-column chromatographic set-up developed as an alternative approach to gradient elution chromatography shows evident advantages (time and solvent reduction more than one-third) as compared with single-column gradient SIC method with Chromolith Flash RP-18 (25 mm x 4.6 mm i.d. with guard column 5 mm x 4.6 mm i.d.). PMID:20457303

Chocholous, Petr; Satínský, Dalibor; Sklenárová, Hana; Solich, Petr

2010-01-18

415

Analysis of polychlorinated biphenyls in transformer oils by automated on-line coupling reversed phase liquid chromatography-gas chromatography using the through oven transfer adsorption desorption (TOTAD) Interface  

Microsoft Academic Search

An automated method for the direct analysis of polychlorinated biphenyls (PCBs) in transformer oil is presented. The proposed method uses the TOTAD (through oven transfer adsorption desorption) interface for the on-line coupling of reversed phase liquid chromatography and gas chromatography (RPLC-GC). In this fully automated system, the oil is injected directly with no sample pre-treatment step other than dilution with

José Manuel Cortés; Juan C. Andini; Rosa M. Toledano; Carlos Quintero; Jesús Villén; Ana Vázquez

2012-01-01

416

Targeted multidimensional gas chromatography for the quantitative analysis of suspected allergens in fragrance products.  

PubMed

Two approaches are described and compared for the analysis of suspected allergens (SAs) in fragrance products, which are defined by the Scientific Committee of Cosmetics and Non-Food Products (SCCNFP). The first consists of a comprehensive two-dimensional gas chromatography (GC x GC) experiment using both a "conventional" non-polar/polar column combination and an "inverse" polar/non-polar column set. The second approach uses a targeted multidimensional gas chromatography (MDGC) system employing a Deans type pneumatic switch and a longitudinally modulated cryogenic system (LMCS). It was found that the conventional and inverse column sets complement each other well, providing identification of SAs present. Compounds well retained on the second dimension of one column set were the first to be eluted from the other. In some instances SAs co-eluting with matrix components on the second dimension for a given column set were clearly resolved on the other, although this has the disadvantage of requiring two analytical runs. Targeted MDGC with a non-polar/polar column set, successfully separated all SAs identified within a fragrance product. The instrument is set up in a similar fashion to a GC x GC system though with longer second dimension ((2)D) column, a cryogenic trap at the beginning of the second column, and a pneumatic switch coupling both columns. The data are easier to process than for a GC x GC experiment. The targeted MDGC method has the capacity to deliver far greater efficiency to targeted regions of a primary separation than a GC x GC experiment, whilst still maintaining overall run times similar to those of a conventional one-dimensional (1D) GC experiment. Cryogenic focussing at the beginning of the (2)D column delivers enhanced sensitivity, accurate (2)D retention times and narrow peak widths; these are responsible for an increased resolution obtained from the fast, relatively short (approximately 5 m) (2)D column. The two column set GC x GC analysis provided a quick and effective means to qualitatively determine the presence of six SAs in a commercially available air freshener, however all were not adequately resolved from matrix components. In contrast, quantitation was straightforward using the targeted MDGC method. PMID:16934274

Dunn, Michael S; Vulic, Natalie; Shellie, Robert A; Whitehead, Simon; Morrison, Paul; Marriott, Philip J

2006-08-24

417

Synthesis of Water-Soluble Gold Nanoparticles Covered with DNA Using Gas-Liquid Interfacial Plasma  

NASA Astrophysics Data System (ADS)

Water-soluble gold nanoparticles (AuNPs) covered with DNA are desired for the application to a novel DNA delivery system. A gas-liquid interfacial discharge plasma (GLIDP) in association with DNA is used for the rapid synthesis of a DNA-AuNP conjugate, where the synthesis is free from the elaborate reaction control usually required in conventional methods. Moreover, the size and morphology of the AuNPs are simply tuned by varying the concentration and type of DNA which acts as a stabilizer through conjugating on the AuNPs. The DNA conjugation prevents the AuNPs from a further coalescence, resulting in the formation of small-sized AuNPs. These small-sized DNA-AuNP conjugates are encapsulated into carbon nanotubes which work as a capsule for the delivery to a diseased part.

Kaneko, Toshiro; Chen, Qiang; Hatakeyama, Rikizo

2011-11-01

418

Controllable gas/liquid/liquid double emulsions in a dual-coaxial microfluidic device.  

PubMed

This article presents a simple and novel approach to prepare monodispersed gas-in-oil-in-water (G/O/W) and gas-in-water-in-oil (G/W/O) double-emulsions in the same dual-coaxial microfluidic device. The effects of three phase flow rates on the sizes of microbubbles and droplets and the number of the encapsulated microbubbles were systematically studied. We successfully synthesized two different types of gas/liquid/liquid (G/L/L) double emulsions with different inner structures in the same geometry by adjusting the flow rates sequentially. Mathematical models were developed to predict the size and structures of the double emulsions. This simple approach gives a new idea for preparing hollow and porous microspheres with microbubbles as the direct core/pores templates. PMID:22508390

Xu, Jian-Hong; Chen, Ran; Wang, Yun-Dong; Luo, Guang-Sheng

2012-04-16

419

Stratified gas-liquid two-phase electrohydrodynamics in horizontal pipe flow  

SciTech Connect

Stratified gas-liquid two-phase electrohydrodynamics in pipe flow has been studied experimentally and numerically. Experimental studies are conducted using 1.27 and 1.9 {times} 10 {sup {minus} 2} m inner diameter horizontal tubes with air-water two-phase flow for the range of gas superficial velocity of 10 {plus minus} {sup 2} {minus} 10 m/s, liquid superficial velocity of 10 {sup {minus} 2} {minus} 2 {times} 10 {minus} 1 m/s, and applied voltage of 0-20 kV. Experimental results are analyzed by an area-averaged two-fluid one-dimensional model. The results show that the effect of the applied electric field is significantly influenced by the flow regime transition boundaries in between the stratified smooth-to-wavy and stratified wavy-to-intermittent flow. However, the time-averaged void fraction was not observed to be significantly influenced by applied electric fields.

Chang, J.S. (Dept. of Engineering Physics, McMaster Univ., Hamilton, ON (CA))

1989-03-01

420

Gas-liquid mass transfer characteristics in a bubble column with suspended sparingly soluble fine particles  

SciTech Connect

(To investigate the influence of suspended particles on mass transfer characteristics in a slurry bubble column, physical and chemical absorptions were performed into aqueous slurries of fine calcium hydroxide particles ca. 7 ..mu..m in average size. Such mass transfer parameters as volumetric liquid-side mass transfer coefficient, specific gas-liquid interfacial area, and hence liquid-side mass transfer coefficient were determined under various electrolyte concentrations, solid concentrations, and gas flow rates.) and K /SUB L/ /SUP o/ a could be correlated by the gas flow rate. (The volumetric gas-side mass transfer coefficient was determined and correlated by the gas flow rate. The enhancement factors during absorption of dilute carbon dioxide into aqueous calcium hydroxide slurries were compared with the theoretical predictions based on the film theoryincorporating a finite slurry concept.)

Sada, E.; Fujiwara, N.; Kumazawa, M.; Lee, C.

1985-04-01

421

New Thruster System for Small Satellite : Gas-Liquid Equilibrium Thruster  

NASA Astrophysics Data System (ADS)

In the proposed gas-liquid equilibrium thruster, fuel is mainly stored in the liquid phase in the tank and is ejected in the gas phase, powered by the vapor pressure of the fuel. As compared to conventional thrusters, the thrust level of this thruster is low. However, the system configuration of this thruster is simple because components such as combustors or high-pressure reservoirs are not required. Further, this thruster is lighter than other thrusters. Fuels with low toxicity and that are easily available can be selected in this thruster from many kinds of fuel candidates. As a result, this thruster can be easily handled. This thruster can be used as an actuator for controlling the attitude and maneuvering the orbit of small satellites.

Yamamoto, Takayuki; Mori, Osamu; Kawaguchi, Jun'ichiro

422

Studies of momentum and energy transfer across wavy gas-liquid interfaces  

NASA Astrophysics Data System (ADS)

Two phase gas-liquid flow and its associated interfaces exist in a wide variety of situations of importance to the Navy and this has prompted the study of the basic flow mechanics which underlie this complex process. The existence of wind-wave interactions over large bodies of water have long been recognized as a special case of two phase flow where the presence of the deformable interface plays a complex role in the generation of waves due to the action of the wind. Less well recognized, but of great importance, are situations of two phase flow which are found in component of power systems such as condensers, boiler refrigeration loops, and cryogen lines. Here the characteristics of two phase flow are critical to the reliable design and safe operation of such systems.

Dukler, A. E.

1993-06-01

423

Effect of impeller geometry on gas-liquid mass transfer coefficients in filamentous suspensions.  

PubMed

Volumetric gas-liquid mass transfer coefficients were measured in suspensions of cellulose fibers with concentrations ranging from 0 to 20 g/L. The mass transfer coefficients were measured using the dynamic method. Results are presented for three different combinations of impellers at a variety of gassing rates and agitation speeds. Rheological properties of the cellulose fibers were also measured using the impeller viscometer method. Tests were conducted in a 20 L stirred-tank fermentor and in 65 L tank with a height to diameter ratio of 3:1. Power consumption was measured in both vessels. At low agitation rates, two Rushton turbines gave 20% better performance than the Rushton and hydrofoil combination and 40% better performance than the Rushton and propeller combination for oxygen transfer. At higher agitation rates, the Rushton and hydrofoil combination gave 14 and 25% better performance for oxygen transfer than two Rushton turbines and the Rushton and hydrofoil combination, respectively. PMID:18576095

Dronawat, S N; Svihla, C K; Hanley, T R

1997-01-01

424

Multivariate data analysis of UV spectra in monitoring elution and determining endpoint of chromatography using polyamide column.  

PubMed

Chromatography using polyamide column is one of the most critical purification operations that affect the safety and efficacy of traditional Chinese medicine (TCM) products. To ensure successful operation and reduce time and solvent consumption, UV spectroscopy combined with multivariate data analysis as an online analytical tool was developed for monitoring the polyamide column chromatography of the TCM Danshen. The process trajectories were established by principal component analysis of the UV spectra and used to determine the endpoint of the washing stage and investigate the impacts of the process conditions. The online analysis method developed determined the concentration of salvianolic acid B (an important compound in Danshen) in the effluent rapidly and precisely with a coefficient of determination of 0.9963 and helped to collect salvianolic acid B quantitatively for determining the endpoint of elution. The methodology proposed is an effective approach applicable in guiding successful operations in the chromatographic separation. PMID:23423990

Yan, Binjun; Qu, Haibin

2013-02-19

425

The inactivation of Chlorella spp. with dielectric barrier discharge in gas-liquid mixture  

NASA Astrophysics Data System (ADS)

The inactivation of Chlorella spp. with high voltage and frequency pulsed dielectric barrier discharge in hybrid gas-liquid reactor with a suspension electrode was studied experimentally. In the hybrid gas-liquid reactor, a steel plate was used as high voltage electrode while a quartz plate as a dielectric layer, another steel plate placing in the aqueous solution worked as a whole ground electrode. A suspension electrode is installed near the surface of solution between high voltage and ground electrode to make the dielectric barrier discharge uniform and stable, the discharge gap was between the quartz plate and the surface of the water. The effect of peak voltage, treatment time, the initial concentration of Chlorella spp. and conductivity of solution on the inactivation rate of Chlorella spp. was investigated, and the inactivation mechanism of Chlorella spp. preliminarily was studied. Utilizing this system inactivation of Chlorella spp., the inactivation rate increased with increasing of peak voltage, treatment time and electric conductivity. It was found that the inactivation rate of Chlorella spp. arrived at 100% when the initial concentration was 4 × 106 cells mL-1, and the optimum operation condition required a peak voltage of 20 kV, a treatment time of 10 min and a frequency of 7 kHz. Though the increasing of initial concentration of the Chlorella spp. contributed to the addition of interaction probability between the Chlorella spp. and O3, H2O2, high-energy electrons, UV radiation and other active substances, the total inactivation number raise, but the inactivation rate of the Chlorella spp. decreased.

Song, Dan; Sun, Bing; Zhu, Xiaomei; Yan, Zhiyu; Liu, Hui; Liu, Yongjun

2013-03-01

426

Determinations of gas-liquid partition coefficients using capillary chromatographic columns. Alkanols in squalane.  

PubMed

This study focused on an investigation into the experimental quantities inherent in the determination of partition coefficients from gas-liquid chromatographic measurements through the use of capillary columns. We prepared several squalane - (2,6,10,15,19,23-hexamethyltetracosane) - containing columns with very precisely known phase ratios and determined solute retention and hold-up times at 30, 40, 50 and 60°C. We calculated infinite dilution partition coefficients from the slopes of the linear regression of retention factors as a function of the reciprocal of the phase ratio by means of fundamental chromatographic equations. In order to minimize gas-solid and liquid-solid interface contributions to retention, the surface of the capillary inner wall was pretreated to guarantee a uniform coat of stationary phase. The validity of the proposed approach was first tested by estimating the partition coefficients of n-alkanes between n-pentane and n-nonane, for which compounds data from the literature were available. Then partition coefficients of sixteen aliphatic alcohols in squalane were determined at those four temperatures. We deliberately chose these highly challenging systems: alcohols in the reference paraffinic stationary phase. These solutes exhibited adsorption in the gas-liquid interface that contributed to retention. The corresponding adsorption constant values were estimated. We fully discuss here the uncertainties associated with each experimental measurement and how these fundamental determinations can be performed precisely by circumventing the main drawbacks. The proposed strategy is reliable and much simpler than the classical chromatographic method employing packed columns. PMID:23659974

Tascon, Marcos; Romero, Lílian M; Acquaviva, Agustín; Keunchkarian, Sonia; Castells, Cecilia

2013-04-18

427

NASA Li/CF(X) Cell Problem Analysis: Anion Exchange Chromatography Analysis.  

National Technical Information Service (NTIS)

An analysis was made of wiper samples used to wipe down lithium/carbon fluorine battery components and production equipment. These components and equipment were potentially exposed to thionyl chloride vapors. In the presence of moisture, thionyl chloride ...

J. Bytella

1991-01-01

428

EVALUATION OF GEL PERMEATION CHROMATOGRAPHY FOR CLEAN UP OF HUMAN ADIPOSE TISSUE SAMPLES FOR GC/MS ANALYSIS OF PESTICIDES AND OTHER CHEMICALS  

EPA Science Inventory

Gel permeation chromatography (GPC) has been evaluated for clean up of human adipose tissue sample extracts in preparation for confirmatory analysis by gas chromatography-mass spectrometry (GC/MS). Studies were conducted with standard solutions, fortified chicken fat, and actual ...

429

Direct analysis of several Fusarium mycotoxins in cereals by capillary gas chromatography-mass spectrometry.  

PubMed

A method for qualitative and quantitative analysis of Fusarium mycotoxins by gas chromatography-mass spectrometry (GC-MS) using cold on-column injection was improved. Eight typical mycotoxins, including deoxynivalenol (DON), 3-acetyldeoxynivalenol (3ADN), fusarenon-X (FX), diacetoxyscirpenol (DAS), 15-monoacetylscirpenol (15MAS), T-2 toxin (T-2), scirpentriol (SCT), and zearalenone (ZEA) were subjected to GC-MS without chemical derivatization by means of the on-column injection technique. Chromatographic separation of the toxins extracted from barley was achieved as a single peak, and the specific EI mass spectra of each toxin were obtained. The fatty acids in the extract that interfere with measurements of the toxins on the gas chromatogram were removed by precipitation as an insoluble metal soap with zinc acetate. Additional clean-up was accomplished using a Bond Elut Florisil cartridge. The quantitative detection limit in barley ranged from 0.1 to 0.5 micrograms/g. The average recoveries of 93.1% for DON, 3ADN, 15MAS, DAS, T-2 and ZEA, and 46.0% for FX and SCT added to barley at the level of 1 microgram/g were obtained. PMID:9718707

Onji, Y; Aoki, Y; Tani, N; Umebayashi, K; Kitada, Y; Dohi, Y

1998-07-31

430

Nano-liquid chromatography in nutraceutical analysis: Determination of polyphenols in bee pollen.  

PubMed

In this study, a nano-liquid chromatography based method for the simultaneous separation of 16 polyphenols employing UV-vis detection has been developed. A 100?m I.D. capillary column packed with C18 core-shell particles (2.6?m particle size, 100?) for 10cm was employed. The separation of analytes was performed with a step gradient in less than 20min, using 0.5% formic acid aqueous solution and acetonitrile as eluents. The optimized analytical method was validated and the resulting RSD% for intra-day and inter-day repeatability, related to retention time, retention factor and peak area, were below 4.68 and 5.57%, respectively. LOD and LOQ values were as low as 0.78 and 3.12?g/mL, while linearity, assessed in the concentration range of interest for all analytes, gave R(2)?0.990. The method was finally applied to the analysis of polyphenols extracted from a collected bee pollen. Nine polyphenols, namely o-, p-coumaric acid, ferulic acid, myricetin, cinnamic acid, quercetin, naringenin, hesperitin and kaempferol, were identified. All analytes, with the exception of p-coumaric acid and myricetin, which partially co-eluted with other pollen components, were also quantified in the sample. PMID:23880468

Fanali, Chiara; Dugo, Laura; Rocco, Anna

2013-06-28

431

Proteomic analysis of endodontic infections by liquid chromatography-tandem mass spectrometry  

PubMed Central

Introduction Endodontic infections are very prevalent and have a polymicrobial etiology characterized by complex interrelationships between endodontic microorganisms and the host defenses. Proteomic analysis of endodontic infections can provide global insights into the invasion, pathogenicity mechanisms, and multifactorial interactions existing between root canal bacteria and the host in the initiation and progression of apical periodontitis. The purpose of this study was to apply proteomic techniques such as liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the identification of proteins of bacterial origin present in endodontic infections. Methods Endodontic specimens were aseptically obtained from seven patients with root canal infections. Protein mixtures were subjected to tryptic in-solution digestion and analysed by reverse-phase nano-LC–MS/MS followed by a database search. Results Proteins, mainly of cell wall or membrane origin, from endodontic bacteria especially Enterococcus faecalis, Enterococcus faecium, Porphyromonas gingivalis, Fusobacterium nucleatum, and Treponema denticola were identified from all the samples tested. Identified proteins included adhesins, autolysins, proteases, virulence factors, and antibiotic-resistance proteins. Conclusions LC–MS/MS offers a sensitive analytical platform to study the disease processes in the root canal environment. The array of proteins expressed in endodontic infections reflects the complex microbial presence and highlights the bacterial species involved in the inflammatory process.

Nandakumar, R.; Madayiputhiya, N.; Fouad, A.F.

2009-01-01

432

A validated method for analysis of Swerchirin in Swertia longifolia Boiss. by high performance liquid chromatography  

PubMed Central

Swertia spp. (Gentianaceae) grow widely in the eastern and southern Asian countries and are used as traditional medicine for gastrointestinal disorders. Swerchirin, one of the xanthones in Swertia spp., has many pharmacological properties, such as, antimalarial, antihepatotoxic, and hypoglycemic effects. Because of the pharmacological importance of Swerchirin in this investigation, it was purified from Swertia longifolia Boiss. as one of the main components and quantified by means of a validated high performance liquid chromatography (HPLC) technique. Aerial parts of the plant were extracted with acetone 80%. Phenolic and non-phenolic constituents of the extract were separated from each other during several processes. The phenolic fraction was injected into the semi-preparative HPLC system, which consisted of a C18 column and a gradient methanol: 0.1% formic acid mode. Using this method, we were able to purify six xanthones from the plant, in order to use them as standard materials. The analytical method was validated for Swerchirin as one of the most important components of the plant, with more pharmacological activities according to the validation parameters, such as, selectivity, linearity (r2 > 0.9998), precision (?3.3), and accuracy, which were measured by the determination of recovery (98-107%). The limits of detection and quantization were found to be 2.1 and 6.3 ?g/mL, respectively. On account of the speed and accuracy, the UV-HPLC method may be used for quantitative analysis of Swerchirin.

Shekarchi, M.; Hajimehdipoor, H.; Khanavi, M.; Adib, N.; Bozorgi, M.; Akbari-Adergani, B.

2010-01-01

433

Liquid chromatography-mass spectrometric analysis of lipids present in human meibomian gland secretions.  

PubMed

The purpose of the study was to qualitatively characterize the major lipid species present in human meibomian gland secretions (MGS) by means of high-performance liquid chromatography with atmospheric pressure ionization mass spectrometric detection of the analytes (NP HPLC-MS). Two different NP HPLC-MS methods have been developed to analyze lipid species that were expected to be present in MGS. The first method was optimized for the analysis of relatively nonpolar lipids [wax esters (WE), di- and triacyl glycerols (DAG and TAG), cholesterol (Chl) and its esters (Chl-E), and ceramides (Cer)], while the second method was designed to separate and detect phospholipids. The major lipid species in MGS were found to be WE, Chl-E, and TAG. A minor amount of free Chl (less then 0.5% of the Chl-E fraction) was detected in MGS. No appreciable amounts of DAG and Cer were found in MGS. The second NP HPLC-MS method, capable of analyzing model mixtures of authentic phospholipids (e.g. phosphatidylglycerol, phosphatidylethanolamine, phosphatidic acid, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, and sphingomyelin) in submicrogram/mL concentrations, showed little or no presence of these species in the MGS samples. These observations suggest that MGS are a major source of the nonpolar lipids of the WE and Chl-E families for the tear film lipid layer (TFLL), but not of the previously reported phospholipid components of the TFLL. PMID:17605062

Butovich, Igor A; Uchiyama, Eduardo; Di Pascuale, Mario A; McCulley, James P

2007-06-29

434

Analysis of carbofuran, carbosulfan, isoprocarb, 3-hydroxycarbofuran, and 3-ketocarbofuran by micellar electrokinetic chromatography.  

PubMed

We developed an analytical method for the detection and quantitation of five pesticides and some of their metabolites - 3-hydroxycarbofuran, 3-ketocarbofuran, carbofuran, carbosulfan, and isoprocarb - using micellar electrokinetic chromatography coupled with a UV-Vis detector. The optimum separation conditions were 20 mM phosphate buffer (pH 8.0) containing 15 mM sodium dodecyl sulfate. The detection wavelength was set at 200 nm and the applied voltage was 12.5 kV. Under these conditions, baseline separation of five pesticides was achieved in 15 min, and the detection limits (S/N = 3) of 3-hydroxycarbofuran, 3-ketocarbofuran, carbofuran, carbosulfan, and isoprocarb were 0.3, 0.3, 0.3, 4.0, and 0.3 ?M, respectively. The linear ranges for 3-hydroxycarbofuran, 3-ketocarbofuran, carbofuran, and isoprocarb were between 1.0 and 50.0 ?M and that for carbosulfan was between 10.0 and 100.0 ?M, with R(2) larger than 0.995. When applied to the analysis of a carbofuran-spiked rice sample, this approach yielded results with excellent repeatability (3.3%, n = 5), reproducibility (4.5%, n = 5), separation efficiency (>2.1 × 10(4) theoretical plates), and recovery (95.5 ± 1.4%, n = 5). PMID:22733517

Hsu, Chien-Hua; Hu, Cho-Chun; Chiu, Tai-Chia

2012-06-01

435

Simple and rapid analysis of methyldibromo glutaronitrile in cosmetic products by gas chromatography mass spectrometry.  

PubMed

A simple and rapid gas chromatography (GC) method with mass spectrometry (MS) detection has been developed for the determination of methyldibromo glutaronitrile (MDBGN) in cosmetic products. The presence of this preservative in commercial cosmetic samples is prohibited since 2007 because of its allergenic properties. The analyzed products were opportunely diluted in methanol and MDBGN was separated by fused silica capillary column and detected by electron impact (EI)-MS in positive ionization mode with a total run time of 7 min. The assay was validated in the range 0.005-0.100 mg MDBGN per g of examined product with good determination coefficients (r(2)?0.99) for the calibration curves. At three concentrations spanning the linear dynamic range of the calibration curves, mean recoveries were always higher than 95% for MDBGN in the tested cosmetics. This method was successfully applied to the analysis of cleansing gels, shampoo and solar waters to disclose the eventual presence of MDBGN illegally added in cosmetic products. PMID:21871753

Pellegrini, Manuela; Bossù, Elena; Rotolo, Maria Concetta; Pacifici, Roberta; Pichini, Simona

2011-08-04

436

Analysis of Fluconazole in Human Urine Sample by High Performance Liquid Chromatography Method  

NASA Astrophysics Data System (ADS)

A method for determination of fluconazole, antifungal drug in human urine by using reversed-phased high performance liquid chromatography (RP-HPLC) with ultraviolet (UV) detector was developed. Optimization HPLC conditions were carried out by changing the flow rate and composition of mobile phase. The optimum separation conditions at a flow rate 0.85 mL/min with a composition of mobile phase containing methanol:water (70:30, v/v) with UV detection at a wavelength 254 nm was able to analyze fluconazole within 3 min. The excellent linearity was obtained in the range of concentration 1 to 10 ?g/mL with r2 = 0.998. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.39 ?g/mL and 1.28 ?g/mL, respectively. Solid phase extraction (SPE) method using octadecylsilane (C18) as a sorbent was used to clean-up and pre-concentrated of the urine sample prior to HPLC analysis. The average recoveries of fluconazole in spiked urine sample was 72.4% with RSD of 3.21% (n=3).

Hermawan, D.; Ali, N. A. Md; Ibrahim, W. A. Wan; Sanagi, M. M.

2013-04-01

437

Liquid Chromatography-Tandem Mass Spectrometry for Analysis of Intestinal Permeability of Loperamide in Physiological Buffer  

PubMed Central

Analysis of in vitro samples with high salt concentrations represents a major challenge for fast and specific quantification with liquid chromatography-tandem mass spectrometry (LC-MS/MS). To investigate the intestinal permeability of opioids in vitro employing the Ussing chamber technique, we developed and validated a fast, sensitive and selective method based on LC–MS/MS for the determination of loperamide in HEPES-buffered Ringer's solution. Chromatographic separation was achieved with an Atlantis dC18 column, 2.1 mm×20 mm, 3 µm particle size and a gradient consisting of methanol/0.1% formic acid and ammonium acetate. The flow rate was 0.7 ml/min, and the total run time was 3 min. For quantification, two mass transitions for loperamide and a deuterated internal standard (methadone-d3) were used. The lower limit of loperamide quantification was 0.2 ng/ml. This new LC-MS/MS method can be used for the detection of loperamide in any experimental setup using HEPES-buffered Ringer's solution as a matrix compound.

Rubelt, Miriam S.; Amasheh, Salah; Grobosch, Thomas; Stein, Christoph

2012-01-01

438

Analysis of Dyes Extracted from Millimeter-Size Nylon Fibers by Micellar Electrokinetic Chromatography  

SciTech Connect

The Learning Objective is to present to the forensic community a potential qualitative/quantitative method for trace-fiber color comparisons using micellar electrokinetic chromatography (MEKC). Developing a means of analyzing extracted dye constituents from millimeter-size nylon fiber samples was the objective of this research initiative. Aside from ascertaining fiber type, color evaluation and source comparison of trace-fiber evidence plays a critical role in forensic-fiber examinations. Literally thousands of dyes exist to date, including both natural and synthetic compounds. Typically a three-color-dye combination is employed to affect a given color on fiber material. The result of this practice leads to a significant number of potential dye combinations capable of producing a similar color and shade. Since a typical forensic fiber sample is 2 mm or less in length, an ideal forensic dye analysis would qualitatively and quantitatively identify the extracted dye constituents from a sample size of 1 mm or smaller. The goal of this research was to develop an analytical method for comparing individual dye constituents from trace-fiber evidence with dyes extracted from a suspected source, while preserving as much of the original evidence as possible.

Lewis, L.A.

2001-07-30

439

Analysis of pesticides by gas chromatography/multiphoton ionization/mass spectrometry using a femtosecond laser.  

PubMed

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOFMS) was utilized for analysis of a standard mixture sample containing 49 pesticides and 4 real samples using the third-harmonic emission (267 nm) of a femtosecond Ti:sapphire laser (100 fs) as the ionization source. A sample of a standard mixture of n-alkane was also measured for calibration of the retention time indices of the pesticides. Two photons are required for the excitation of n-alkane due to an absorption band located in the far ultraviolet region (140 nm). The n-alkane molecule in the excited state was subsequently ionized either directly or by absorbing another photon because of a high ionization potential. Due to a large excess of energy, the molecular ion was decomposed and formed many fragment ions. Compared to n-alkanes, most of the pesticides were softly ionized by the femtosecond laser; one photon was used for excitation and another was used for the subsequent ionization. The pesticides with no conjugated double bond had a lower ionization efficiency. The present analytical instrument was applied to several samples prepared from a variety of vegetables and a single fruit after pretreatment with solid-phase extraction. Three pesticides were found in these samples, although some of them were not detected by conventional GC/EI/MS-MS due to insufficient sensitivity and selectivity. PMID:21763808

Li, Adan; Imasaka, Tomoko; Uchimura, Tomohiro; Imasaka, Totaro

2011-06-13

440

Simultaneous analysis of serotonin, melatonin, piceid and resveratrol in fruits using liquid chromatography tandem mass spectrometry.  

PubMed

An analytical method was developed for the simultaneous quantification of serotonin, melatonin, trans- and cis-piceid, and trans- and cis-resveratrol using reversed-phase high performance liquid chromatography coupled to mass spectrometry (HPLC-MS) with electrospray ionization (ESI) in both positive and negative ionization modes. HPLC optimal analytical separation was achieved using a mixture of acetonitrile and water with 0.1% formic acid as the mobile phase in linear gradient elution. The mass spectrometry parameters were optimized for reliable quantification and the enhanced selectivity and sensitivity selected reaction monitoring mode (SRM) was applied. For extraction, the direct analysis of initial methanol extracts was compared with further ethyl acetate extraction. In order to demonstrate the applicability of this analytical method, serotonin, melatonin, trans- and cis-piceid, and trans- and cis-resveratrol from 24 kinds of commonly consumed fruits were quantified. The highest serotonin content was found in plantain, while orange bell peppers had the highest melatonin content. Grape samples possessed higher trans- and cis-piceid, and trans- and cis-resveratrol contents than the other fruits. The results indicate that the combination of HPLC-MS detection and simple sample preparation allows the rapid and accurate quantification of serotonin, melatonin, trans- and cis-piceid, and trans- and cis-resveratrol in fruits. PMID:21570690

Huang, Xin; Mazza, Giuseppe

2011-04-27

441

Mass Spectrometric Analysis of Intact Human Monoclonal Antibody Aggregates Fractionated by Size-Exclusion Chromatography  

PubMed Central

ABSTRACT Purpose The aim of this study was to develop a method to characterize intact soluble monoclonal IgG1 antibody (IgG) oligomers by mass spectrometry. Methods IgG aggregates (dimers, trimers, tetramers and high-molecular-weight oligomers) were created by subjecting an IgG formulation to several pH jumps. Protein oligomer fractions were isolated by high performance size exclusion chromatography (HP-SEC), dialyzed against ammonium acetate pH 6.0 (a mass spectrometry-compatible volatile buffer), and analyzed by native electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS). Results Monomeric and aggregated IgG fractions in the stressed IgG formulation were successfully isolated by HP-SEC. ESI-TOF MS analysis enabled us to determine the molecular weight of the monomeric IgG as well as the aggregates, including dimers, trimers and tetramers. HP-SEC separation and sample preparation proved to be necessary for good quality signal in ESI-TOF MS. Both the HP-SEC protocol and the ESI-TOF mass spectrometric technique were shown to leave the IgG oligomers largely intact. Conclusions ESI-TOF MS is a useful tool complementary to HP-SEC to identify and characterize small oligomeric protein aggregates.

Kukrer, Basak; Filipe, Vasco; van Duijn, Esther; Kasper, Piotr T.; Vreeken, Rob J.; Heck, Albert J. R.

2010-01-01

442

[Analysis of six acidic components in hops extracts by high performance liquid chromatography].  

PubMed

A method of high performance liquid chromatography (HPLC) was developed for the separation and determination of six acidic components (cohumulone, humulone, adhumulone, colupulone, lupulone and adlupulone) in hops extracts. The effects of several important factors, such as the addition of acid, the organic solvent of elution solution and the column temperature, were investigated to acquire the optimum conditions. The separation was carried out on a Hypersil ODS2 column (250 mm x 4. 6 mm, 5 microm). A mixture of acetonitrile-0. 1% (v/v) phosphoric acid solution (pH 2. 2) (65: 35, v/v) was used as the mobile phase at a flow rate of 1. 0 mL/min in isocratic elution mode. The column temperature was kept at room temperature, and the detection wavelength was set at 315 nm. The six acidic components reached baseline separation, and were identified by ultraviolet spectroscopy, infrared spectroscopy and mass spectrometry. The results show that this method is suitable for the analysis of acidic components in hops extracts owing to the stable and simple performance. PMID:22268354

Cai, Xiaoming; Xia, Lu; Sun, Yuanshe; Li, Tong; Xia, Mingzhu

2011-10-01

443

[Analysis of organochlorine pesticides in buckwheat using pressurized liquid extraction and gas chromatography].  

PubMed

Seven organochlorine pesticides (OCPs) in buckwheat were extracted by a homemade 24 cells auto-pressurized liquid extraction instrument (APLE) and then analyzed by gas chromatography with electronic capture detection. The optimal extraction condition was found to be 100 degrees C and 10 MPa for 5 min with acetone/n-hexane (1:1, v/v) as the extraction solvent. The extraction was performed twice for each sample to obtain complete extraction. The buckwheat was mixed with florisil and active carbon before filling into extraction cells. Concentrated sulfuric acid was used in clean up step of the extractant. The standard mixture of OCPs including alpha-benzene hexachloride (BHC), gamma-BHC, delta-BHC, p, p'-dichloro-diphenyl-dichloroethylene (p,p'-DDE), p,p'-dichloro-diphenyl-dichloroethane (p, p'-DDD), o, p-dichloro-diphenyl trichloro-ethane (o,p-DDT), p,p'-DDT was used for the identification and quantification in gas chromatographic analysis. The absolute recoveries of the 7 organochlorine pesticides were between 68%-126% with the relative standard deviations lower 14.7%. The detection limits were between 0.051 - 0.18 ng/g. The relative recoveries were as high as 116%-148% compared with Soxhlet extraction. It shows that the recoveries of APLE are much better than Soxhlet extraction, and the time of extraction for APLE is only about 15 min which is much less than conventional extraction methods. PMID:18959247

Lian, Mei; Xu, Feng; Guan, Wenna; Xu, Yuan; Guan, Yafeng

2008-07-01

444

Analysis of the estrogenic components in kudzu root by bioassay and high performance liquid chromatography.  

PubMed

The estrogenic activity of the Chinese herb kudzu root was investigated by a recombinant yeast screening assay (YES). Isoflavones are the main components in the plant, of which puerarin is the most abundant one. The kudzu root extract was separated into four fractions according to the polarity. The crude extract and its sub-fractions, except the water fraction, showed clear estrogenic activity and the potencies were in the range of 10(-3) to 10(-1)g/l. The ligand potency was used to compare the estrogenic activity of these fractions. The crude extract and its sub-fractions were further analyzed by high performance liquid chromatography (HPLC) to correlate the activity and the active components. Bioassay and chemical analysis showed that theoretical estrogenic activity expressed as equivalent 17beta-estradiol concentration or the cumulative effects are comparable to that experimentally determined by YES. The results showed that the high content of isoflavones as well as the high estrogenic activity could make kudzu root extract an interesting candidate for hormone replacement therapy. PMID:15857757

Zhang, Yan; Chen, Jiping; Zhang, Chunzhi; Wu, Wenzhong; Liang, Xinmiao

2005-01-26

445

Gas-liquid chromatographic determinaion of chlorinated benzenes and phenols in selected biological matrices  

SciTech Connect

The determination of higher chlorinated benzenes and chlorinated phenols at parts per billion or parts per million levels in biological samples is described. The method includes sulfuric acid digestion, silica gel column chromatography, methylation, alumina column chromatography, and detection by electron capture gas chromatography. Recoveries are reported for fish flesh, rabbit tissues, and duck tissues with etection limits of 10 to 15 ppb (ng/g tissue).

Lamparski, L.L.; Langhorst, M.L.; Nestrick, T.J.; Cutie, S.

1980-01-01

446

US Crude Oil, Natural Gas, and Natural Gas Liquids Reserves Annual Report 1996: Energy Information Administration (EIA)  

NSDL National Science Digital Library

The EIA has published "the estimates of proved reserves of crude oil, natural gas, and natural gas liquids in the United States as of December 31, 1996, compiled from EIA's oil and gas operator survey." The report shows that while reserves of natural gas have increased, crude oil reserves have declined.

447

A Novel Process for Natural Gas Liquids Recovery from Oil Field Associated Gas with Liquefied Natural Gas Cryogenic Energy Utilization  

Microsoft Academic Search

A novel process to recovery natural gas liquids from oil field associated gas with liquefied natural gas (LNG) cryogenic energy utilization is proposed. Compared to the current electric refrigeration process, the proposed process uses the cryogenic energy of LNG and saves 62.6% of electricity. The proposed process recovers ethane, liquid petroleum gas (propane and butane) and heavier hydrocarbons, with total

Haijun BIAN; Wendong XU; Xiuxi LI; Yu QIAN

2011-01-01

448

Influence of the ejector configuration, scale and the gas density on the mass transfer characteristics of gas–liquid ejectors  

Microsoft Academic Search

For the design and scale-up of gas–liquid ejectors, reliable data are required which describe the mass transfer characteristics as a function of the physical fluid properties, geometrical design and the process related parameters. Therefore, the mass transfer characteristics of various ejector geometries and scales were investigated using the desorption of oxygen from water, by means of an inert gas, as

P. H. M. R Cramers; A. A. C. M Beenackers

2001-01-01

449

Experimental Study on Gas-Liquid Two-Phase Flows in an Areation Tank by Using Image Treatment Method  

Microsoft Academic Search

Particle Image Velocimetry (PIV) technique was employed to study experimentally gas-liquid two-phase flow in an aeration tank. In terms of the PIV principles, an algorithm of PIV based on the Fast Fourier Transformation (FFT) was worked out. The PIV program was developed and verified, and then was used to measure three kinds of states in the testing device. The program

Wen CHENG; Wen-hong LIU; Bao-wei HU; Tian WAN

2008-01-01

450

Working process study of a novel scroll type multiphase pump for the transportation of gas-liquid mixtures  

NASA Astrophysics Data System (ADS)

A novel scroll type multiphase pump was proposed to transport gas-liquid two-phase mixture. There is a pressure unloading gap from compression chambers to the discharge port by constructing scroll wrap profile with variational meshing clearance in this scroll multiphase pump. In the working process when the volume of working chamber decreases, the pressure of gas-liquid mixtures increases gradually, at the same time small amounts of gas-liquid mixture are pushed to the discharge port from compression chambers through the pressure unloading gap. Therefore, this multiphase pump has an advantage of unloading pressure method automatically, and the frequently problem of liquid impacting in volume multiphase pump is solved. The safety and reliability of volumetric multiphase pump are improved, and the scope of multiphase pump of the gas-liquid ratio is expanded. The working process and the performance characteristics of scroll multiphase pump were analyzed too, and the generation method of scroll wrap profile with variational meshing clearance was investigated. The equations of the profile were obtained, and the changing principle of the working volume and the meshing clearance were analyzed. The geometric theory of scroll multiphase pump was formed. All of that lay the theoretical foundation for engineering design of this novel scroll.

Wang, J.; Zha, H. B.; Zhang, X. H.; Zhang, D. H.

2012-11-01

451

A Rapid Analysis of Surface Waters by High Pressure Liquid Chromatography.  

National Technical Information Service (NTIS)

A simple rapid method for obtaining fingerprint traces of nonpolar organic contaminants in water samples by trace enrichment and high pressure liquid chromatography (HPLC) has been evolved. Samples of 30-1000 ml of river water were filtered through precol...

K. Huibregtse

1979-01-01

452

Recycle Gel Permeation Chromatography. Part I. Recycle Principle and Design. Part Ii. Analysis of Epoxy Resins.  

National Technical Information Service (NTIS)

A new recycle circuit for Gel Permeation Chromatography (GPC), named alternate pumping (AP), is described and applied to the fractionation of epoxy resins. Conceptual as well as design details for AP recycle are presented. Advantages and limitations of AP...

J. A. Biesenberger M. Tan I. Duvdevani T. Maurer

1970-01-01

453

Experimental and theoretical study of acetic-acid decomposition by a pulsed dielectric-barrier plasma in a gas-liquid two-phase flow  

NASA Astrophysics Data System (ADS)

Decomposition of acetic acid as a persistent material in water was demonstrated using a pulsed dielectric-barrier plasma in a gas-liquid two-phase flow. The plasma was driven by 35 kV, 200 Hz pulsed voltages and generated in oxygen bubbles in 20 ml solution having a concentration of 10-40 mgTOC l-1. The concentrations of ion species and hydrogen peroxide in the solution were analyzed by ion chromatography and absorptiometry, respectively. After 60 min of operation, the acetic acid was completely decomposed by the plasma. Optical measurements of the emission intensities of OH, H and O radicals suggest that the generated OH radicals are in the ground state in this study. A numerical calculation was carried out to analyze the radical generation processes in the gas phase and decomposition in the liquid phase. O-radical-induced generation of OH radical needed to be considered in the calculation of total organic carbon (TOC) and H2O2 concentrations in the solution. By considering such plasma-water interaction processes, data for the decomposition of acetic acid, which were in good agreement with experimental results, were obtained.

Matsui, Y.; Takeuchi, N.; Sasaki, K.; Hayashi, R.; Yasuoka, K.

2011-06-01

454

Sensitive and specific gas-liquid chromatographic-spectrophotometric screening procedure for trace levels of five sulfonamides in liver, kidney, and muscle tissue.  

PubMed

Free and conjugated sulfonamides are extracted from edible animal tissue with acetone. Carbohydrate is precipitated and removed, and the acetone is evaporated. The residue is transferred to a separatory funnel with ethyl ether and 1N HCl. The acid layer is drawn off and a portion of the 1N HCl is screened, using the Bratton-Marshall reaction. If this portion is positive, the remaining portion is buffered to pH 6.5 and extracted with methylene chloride. The residue is methylated with diazomethane and then acylated with pentafluoropropionic anhydride. The resulting derivatives are detected by gas-liquid chromatography, using electron capture (63Ni) detection and a column packed with 3% OV-17 on Gas-Chrom Q. This method has been validated by recovering sulfathiazole, sulfachloropyrazine, sulfamethazine, sulfadimethoxine, and sulfabromomethazine from liver, kidney, and muscle at levels of 0.1, 0.5, and 1.0 ppm. The 5 sulfonamides were recovered in excess of 60%, with an average mean recovery of 81.5% at the 0.1 ppm level, 79.1% at the 0.5 ppm level, and 76.0% at the 1.0 ppm level. PMID:721719

Goodspeed, D P; Simpson, R M; Ashworth, R B; Shafer, J W; Cook, H R

1978-09-01

455

Analysis of the acidic microenvironment in murine tumours by high-performance ion chromatography  

Microsoft Academic Search

High-performance ion chromatography (HPIC) has been utilised to probe the biochemistry associated with changes in tumour pH following total vascular occlusion. Samples from the tumour extracellular compartment were obtained by insertion of a microdialysis probe and analysed by HPIC with conductivity detection. Separations were carried out by ion-exclusion chromatography using an IonPac ICE AS1 weak-acid column. The eluent (0.5 mM

M. R. L. Stratford; C. S. Parkins; S. A. Everett; M. F. Dennis; M. Stubbs; S. A. Hill

1995-01-01

456

Gas chromatography positive chemical ionization and tandem mass spectrometry for the analysis of organic high explosives  

Microsoft Academic Search

The characteristic ions or the parent ion resulting from ionization can be isolated in an ion trap and subjected to further fragmentation during a gas chromatography–tandem mass spectrometry (GC\\/MS\\/MS) experiment. This approach can improve the selectivity and sensitivity of explosive compounds over gas chromatography–mass spectrometry (GC\\/MS) by improving the differentiation of the target compounds from interfering and co-eluting compounds and

Jeannette M. Perr; Kenneth G. Furton; José R. Almirall

2005-01-01

457

Use of multiwavelength spectrodensitometric thin layer chromatography for the analysis of multicomponent mixtures  

SciTech Connect

The use of spectrodensitometric thin layer chromatography (SDTLC) with multiwavelength scanning and differential signal resolution allows one to solve a series of problems associated with compounds which cannot be sufficiently resolved by chromatography. In this work, the analytical possibilities of SDTLC with the use of a microcomputer to process the obtained data are demonstrated using as an example the determination of several compounds which are potential components of the waste water form the production of the herbicide Nitran.

Kofman, I.Sh.; Linetskii, M.D.; Sokolov, D.A.

1987-12-10

458

Analysis of pyrene metabolites in marine snails by liquid chromatography using fluorescence and mass spectrometry detection.  

PubMed

As part of a study of the metabolism of aromatic compounds in marine gastropods, a sensitive and selective method was developed to detect, identify and quantify pyrene (PY) and four of its metabolites in tissues: 1-hydroxypyrene (PYOH), pyrene sulfate (PYOS), pyrene glucuronide (PYOG) and pyrenediol disulfate (PYDS). Liquid chromatography (LC) with fluorescence detection was first used to detect the PY derivatives in the visceral mass of whelks exposed to PYOH. The identification of metabolites was accomplished through a combination of retention time and spectral matching with standards, enzymatic hydrolysis, solid phase extraction and LC coupled with electrospray ionization mass spectrometry. In addition to four known PY derivatives, two novel metabolites were identified as pyrenediol glucuronide sulfate and a second isomer of PYDS. The methanol extraction of metabolites from tissue gave excellent mean recoveries, ranging from 67 to 97%, for the available standards PY, PYOH, PYOS and PYOG spiked in both the muscle and visceral mass of Buccinum spp. The mean recoveries of a surrogate standard, 2-hydroxyfluorene, spiked in all tissue samples were 100% and 95% for visceral and muscle tissue samples, respectively. The method limits of detection for these compounds were all below 0.2 ng/g of wet tissue, low enough to detect metabolites in reference animals. Results from the application of this method to the quantitative analysis of biotransformation products in the visceral mass of the whelk Neptunia lyrata exposed to PYOH contaminated food are also presented. This method will be useful to apply to the analysis of PY metabolites in soft tissues of other animals. PMID:19553165

Beach, Daniel G; Quilliam, Michael A; Hellou, Jocelyne

2009-06-13

459

Direct plasma metabolite analysis of positron emission tomography radioligands by micellar liquid chromatography with radiometric detection.  

PubMed

Determination of radio-metabolites in plasma samples taken during a positron emission tomography (PET) study is an important component in the pharmacokinetic evaluation of PET radioligands. We have developed and validated a new analytical procedure for the plasma metabolite analysis of PET radioligands based on micellar liquid chromatography using an anionic surfactant mobile phase. Chromatographic separation was performed on an octadecyl semipreparative column (10 mm I.D. × 160 mm, 10 ?m) using 100 mM sodium dodecyl sulfate (SDS) and 1-butanol in 10 mM sodium-phosphate (pH 7.2) at a flow rate of 5 mL/min. The samples taken from monkey or human plasma during PET measurements were directly injected into a liquid chromatographic (LC) system coupled to an online radiometric detector under micellar conditions using 1-2% (v/v) 1-butanol mobile phase to remove plasma proteins and concentrate the analytes at the column head. At 2 min, mobile phase was changed to elute and separate PET radioligand and its radiometabolites with high peak capacity under high submicellar conditions (10-25% 1-butanol). This procedure allowed direct plasma injection (up to 2 mL) into the LC column without any pretreatment with a short analysis-time of 8-10 min. Satisfactory reproducibility, linearity, sensitivity, accuracy and recovery were obtained in the validation study. The developed method was successfully applied to study the metabolism for diverse groups of PET radioligands and provided reliable determination of PET radioligands in human and monkey plasma. This method is advantageous in terms of simplifying and shortening the processes required to analyze short-lived radioligands as well as in providing a more accurate estimation of the metabolite corrected input function, especially for the radioligands with lower recoveries or degradation potential during the deproteination process in a conventional procedure. PMID:22409870

Nakao, Ryuji; Schou, Magnus; Halldin, Christer

2012-03-22

460

Corona-charged aerosol detection in supercritical fluid chromatography for pharmaceutical analysis.  

PubMed

In this paper we describe the coupling of a corona-charged aerosol detector (CAD) to packed column supercritical fluid chromatography (pSFC). The CAD can be coupled to pSFC by connecting the outlet of the back pressure regulator (BPR) directly to the inlet of the detector. To reduce the noise and increase the reproducibility, the transfer line (1 m x 0.25 mm i.d. stainless steel) was placed in a thermostatic bath at 45 degrees C. Limits of detection (LODs) ranged from 3 to 11.5 ng loaded on column, with an average value of 4.5 ng (from 0.6 to 2.3 mg/L, with an average value of 0.9 mg/L for 5 microL injection). To reduce differences in response at different mobile-phase compositions, mobile-phase flow compensation was performed by placing a T-piece before the BPR. In this way, the differences in response were significantly reduced from a factor of 2-3 to a factor of 1.2-1.7. Compared to CAD application without flow compensation, the average LOD was higher by a factor of approximately 1.8. However, the nearly uniform response in gradient analysis with mobile-phase flow compensation far outweighed the slight increase in the LOD. The performance of the pSFC-CAD combination was illustrated by the analysis of selected pharmaceutically related compounds. In addition, a comparison with UV detection was made. Measurement of analytes at a relative concentration of 0.05% versus the main component was demonstrated. PMID:17302387

Brunelli, C; Górecki, T; Zhao, Y; Sandra, P

2007-02-16

461

Rapid analysis of benzoylecgonine in urine by fast gas chromatography-mass spectrometry.  

PubMed

A novel fast gas chromatography-mass spectrometry (FGC-MS) analytical method for benzoylecgonine (BZE) has been developed to improve the efficiency of specimen analysis without diminishing the reliability of metabolite identification and quantification. Urine specimens were spiked with deuterated internal standard (BZE-d8), subjected to solid-phase extraction, and derivatized with pentafluoropropionic anhydride (PFPA) and pentafluoropropanol (PFPOH). The pentafluoropropyl ester derivative of BZE was identified and quantified using both a standard GC-MS method and the newly developed FGC-MS method. Shorter GC analyte retention times were made possible in the FGC-MS method by employing a 220-volt GC oven controller, which allowed an increased temperature ramp rate. The FGC-MS method was linear between 25 and 10,000 ng/mL of BZE yielding a correlation coefficient of 0.9994. The intra-assay precision of a 100 ng/mL BZE standard (n=15) yielded an average concentration of 99.7 ng/mL and a coefficient of variation of 1.2%. The interassay precision of 21 sets of 50, 100, and 125 ng/mL BZE controls was found to be acceptable, with coefficients of variation less than 2.4%. No interference was observed when the FGC-MS method was challenged with cocaine, ecgonine, ecgonine methyl ester, and nine other drugs of abuse. Analysis of presumptively positive specimens (n=146) by both analytical methods yielded comparable results with a correlation coefficient of 0.996. The FGC-MS method, when compared with a standard GC-MS method, reduces total assay time by approximately 50% while demonstrating comparable reliability. PMID:17132251

Romberg, Robert W; Jamerson, Matthew H; Klette, Kevin L

2006-10-01

462

Pitfalls encountered during quantitative determination of 3-alkyl-2-methoxypyrazines in grape must and wine using gas chromatography-mass spectrometry with stable isotope dilution analysis. Comprehensive two-dimensional gas chromatography-mass spectrometry and on-line liquid chromatography-multidimensional gas chromatography-mass spectrometry as potential loopholes.  

PubMed

The analysis of 3-alkyl-2-methoxypyrazines in Vitis vinifera grape must or wine at the low nanogram per liter level failed in several situations when applying a one-dimensional gas chromatographic analysis with mass spectrometric detection (GC-MS). Sample preparation methods such as headspace solid phase microextraction or solid phase extraction were convenient procedures, however lacking extraction selectivity for complex matrices. Analysis by comprehensive two-dimensional gas chromatography with mass spectrometric detection clearly demonstrated the potential for co-elution in such matrices and the risk for erroneous results when applying one-dimensional GC-MS. In one example, matrix problems would have been a challenge even for a comprehensive two-dimensional chromatographic approach with MS detection (GC×GC-MS). A solution to matrix problems was found by protonating the 3-alkyl-2-methoxypyrazines in acidic pH and sample clean-up using solid phase extraction with a mixed-mode polymeric cation-exchange sorbent. Quantification was performed by a stable isotope dilution assay, following analysis by on-line coupled high performance liquid chromatography with multidimensional gas chromatography and detection with mass spectrometry (on-line LC-MDGC-MS). This new approach allowed trace-level analysis of 3-alkyl-2-methoxypyrazines in grape musts and wines and is described for V. vinifera Sauvignon blanc, following 3-alkyl-2-methoxypyrazines concentrations during ripening and in the processed wines. PMID:20637469

Schmarr, Hans-Georg; Ganss, Sebastian; Koschinski, Stefan; Fischer, Ulrich; Riehle, Carmen; Kinnart, Julian; Potouridis, Theodoros; Kutyrev, Maria

2010-06-25

463

Applying Chromatography.  

ERIC Educational Resources Information Center

|Presents three experiments to introduce students to different kinds of chromatography: (1) paper chromatography; (2) gel filtration chromatography; and (3) reverse-phase liquid chromatography. Written in the form of a laboratory manual, explanations of each of the techniques, materials needed, procedures, and a glossary are included. (PVD)|

Klein, Jessie W.; Patev, Paul

1998-01-01

464

Screening of antioxidant phenolic compounds in Chinese rhubarb combining fast counter-current chromatography fractionation and liquid chromatography/mass spectrometry analysis.  

PubMed

In this paper, an effective method combing fast elution-extrusion counter-current chromatography (CCC) and LC/MS for rapid screening of antioxidative phenolic compounds in Chinese Rhubarb is presented. An integrated three-coil CCC column (40 mL each coil) was used to accomplish the optimization of biphasic liquid system. In a single run (approximately 40 min), the solvent system composed of n-hexane/ethyl acetate/methanol/water (1:1:1:1, v/v) was selected as optimum CCC liquid system for fast fractionation of the crude ethanol extract. With a 140 mL-capacity CCC instrument, 100 mg Chinese Rhubarb extract was separated under the optimized conditions, producing six fractions in only 100 min. The quantities of each fraction were approximately 15 mg. In addition, each fraction was subjected to antioxidant activity assay and characterized by LC/MS analysis. Fifty compounds, including phenolic acids, phenolic glucosides and hydroxyanthraquinones, were detected by LC/MS/MS analysis. As a result, gallic acid together with Fr I showed excellent antioxidant activity, which was well consistent with previous studies and exhibited great potential for natural drug discovery program of the present method. PMID:20405489

Hu, Ruilin; Lu, Yanbin; Dai, Xiaojing; Pan, Yuanjiang

2010-06-01

465

Analysis of commercial ceramides by non-aqueous reversed-phase liquid chromatography with evaporative light-scattering detection  

Microsoft Academic Search

Summary  This paper describes the development of a chromatographic system for analysis of commercial ceramides structurally similar\\u000a to those found in the stratum corneum. The ceramides used in this study contain different amine based (phytosphingosine, sphingosine\\u000a and dihydrosphingosine) and fatty acids of different chain lengths and with different functional groups (hydroxylated and\\u000a unsaturated). Non-aqueous reversed-phase (NARP) liquid chromatography with evaporative light-scattering

K. Gaudin; P. Chaminade; D. Ferrier; A. Baillet; A. Tchapla

1999-01-01

466

SIMULTANEOUS DETERMINATION OF PARABENS IN PHARMACEUTICAL PREPARATIONS USING HIGH-PERFORMANCE THIN-LAYER CHROMATOGRAPHY AND IMAGE ANALYSIS  

Microsoft Academic Search

A study for quantitative evaluation of thin layer chromatographic plates by using, for the first time, the BioDit Thin Layer Chromatography (TLC) Scanner device in UV mode was developed for simultaneous determination of the parabens (methyl, ethyl, propyl, and butylparaben) in pharmaceutical preparations. ImageDecipher-TLC software and Sorbfil TLC Videodensitometer were used for image processing analysis. After their chromatographic separation, the

Dorina Casoni; Ioana Anamaria Tuhu?iu; Costel Sârbu

2011-01-01

467

Simultaneous analysis of tea catechins, caffeine, gallic acid, theanine and ascorbic acid by micellar electrokinetic capillary chromatography  

Microsoft Academic Search

A micellar electrokinetic capillary chromatography (MEKC) method for the simultaneous analysis of five tea catechins, theanine, caffeine, gallic acid and ascorbic acid has been developed. The catechins are (?)-epicatechin, (+)-catechin, (?)-epigallocatechin, (?)-epicatechin gallate and (?)-epigallocatechin gallate. p-Nitrophenol serves as both reference and internal standard. All the components are separated within 13 min with a 57 cm uncoated fused-silica column. On-column

J. P Aucamp; Y Hara; Z Apostolides

2000-01-01