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1

Analysis of chemically synthesized oleoylethanolamide by gas-liquid chromatography.  

PubMed

Oleoylethanolamide (OEA) is known to potentially have beneficial biological effects on weight management by controlling food intake and activating lipid catabolism. In biological fluids, OEA and other endogenously biosynthesized fatty acid ethanolamides are usually analyzed by liquid chromatography-mass spectrometry (LC-MS). The present study provides analytical method to routinely assess the quality of OEA prepared for biological studies by gas-liquid chromatography (GLC). The preparation of OEA for biomedical studies can be performed by N-acylation of oleic acid/esters or using oleoyl chloride. In the present study, OEA was prepared by transamidation of triolein. The analysis of the synthesized OEA has been performed by gas-liquid chromatography of its trimethylsilyl ether (TMS) derivatives. Free OEA cannot be analyzed as such because dehydration of the ethanolamide moiety promptly happens in the GLC injection. This thermal degradation reaction gives rise to the formation of an oxazoline derivative. The TMS moiety prevents the reaction, and the structure of the formed derivative was assessed by mass spectrometry. We show here that OEA prepared for biological studies can be routinely analyzed by GLC after TMS derivative preparation. PMID:18644599

Thabuis, Clémentine; Tissot-Favre, Delphine; Bezelgues, Jean-Baptiste; Martin, Jean-Charles; Cruz-Hernandez, Cristina; Dionisi, Fabiola; Destaillats, Frédéric

2008-08-22

2

Simultaneous Extraction and Derivatization of Carbohydrates from Green Plant Tissues for Analysis by Gas–Liquid Chromatography  

Microsoft Academic Search

Simultaneous extraction and derivatization of carbohydrates was performed by mixing dry ground plant tissue with derivatization reagents in pyridine; trimethylsilyl derivatives were analyzed by gas–liquid chromatography. This “direct analysis” was compared to analysis of samples prepared by exhaustive ethanol extraction of the same ground plant tissues. Comparisons included leaf blades from apple, grape, corn, and tomato and leaf blade, petiole,

John G. Streeter; C. Elliott Strimbu

1998-01-01

3

Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.  

ERIC Educational Resources Information Center

Describes a laboratory technique for use in an undergraduate instrumental analysis course that, using the interpretation of window diagrams, prepares a mixed liquid phase column for gas-liquid chromatography. A detailed procedure is provided. (BT)

Koury, Albert M.; Parcher, Jon F.

1979-01-01

4

Gas chromatography in qualitative analysis. Part 13. An alternative to a scale of temperature for use in isothermal gas-liquid chromatography  

Microsoft Academic Search

The problem of measuring meaningful column temperatures in isothermal gas-liquid chromatography is considered in the light of discussions at a recent meeting of the Chromatography Discussion Group [1]. In order to overcome the present difficulties, it is proposed that a chromatographic alternative to a scale of temperature should be adopted, namely the slope of the n-alkane ‘log plot’ (b). Methods

M. B. Evans

1973-01-01

5

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

6

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

7

Application of gas-liquid chromatography to the analysis of essential oils. Part XVII. Fingerprinting of essential oils by temperature-programmed gas-liquid chromatography using capillary columns with non-polar stationary phases. Analytical methods committee.  

PubMed

Problems in obtaining reproducible results when 'fingerprinting' essential oils by temperature-programmed gas-liquid chromatography have been reported on in Parts VII and VIII of this series. Those reports were concerned with the general problems and the use of packed columns. This report is concerned with the use of capillary columns and non-polar stationary phases. A collaborative study using capillary columns with non-polar stationary phases has resulted in a method which specifies the 'g-pack value' of a column and gives reproducible relative retention indices for the test compounds limonene, acetophenone, linalol, naphthalene, linalyl acetate and cinnamyl alcohol. The method has been applied successfully to the examination of oil of rosemary. A recommended method is given for the reproducible temperature-programmed gas-liquid chromatographic fingerprinting of essential oils using capillary columns with non-polar stationary phases. PMID:9463975

1997-10-01

8

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

9

Amino acid analysis by gas-liquid chromatography of N-heptafluorobutyryl isobutyl esters. Complete resolution using a support-coated open-tubular capillary column.  

PubMed

Amino acids have been separated by gas-liquid chromatography as their N-heptafluorobutyryl isobutyl esters. Complete resolution of derivatives of all the common amino acids has been achieved using a high-performance support-coated open-tubular capillary column. The analysis time was 30 min. Modifications to the derivatization procedure of MacKenzie and Tenaschuk have been introduced. Acylation by heating at 150 degrees was shown to be destructive; 110 degrees has been selected for routine preparation. To obtain a volatile histidine derivative it has been found necessary to add an antioxidant and to heat samples with ethoxyformic anhydride prior to injection. Amino acid analysis of beta-lactoglobulin after 6 N HCl digestion yielded results in good agreement with those obtained by the conventional ion-exchange method. The method has also been successfully applied to estimation of the different caseins in whole casein and in purified fractions by amino acid analysis of residues liberated by carboxy-peptidase digestion. PMID:885953

Pearce, R J

1977-06-01

10

An uncooked vegan diet shifts the profile of human fecal microflora: computerized analysis of direct stool sample gas-liquid chromatography profiles of bacterial cellular fatty acids.  

PubMed Central

The effect of an uncooked extreme vegan diet on fecal microflora was studied by direct stool sample gas-liquid chromatography (GLC) of bacterial cellular fatty acids and by quantitative bacterial culture by using classical microbiological techniques of isolation, identification, and enumeration of different bacterial species. Eighteen volunteers were divided randomly into two groups. The test group received an uncooked vegan diet for 1 month and a conventional diet of mixed Western type for the other month of the study. The control group consumed a conventional diet throughout the study period. Stool samples were collected. Bacterial cellular fatty acids were extracted directly from the stool samples and measured by GLC. Computerized analysis of the resulting fatty acid profiles was performed. Such a profile represents all bacterial cellular fatty acids in a sample and thus reflects its microflora and can be used to detect changes, differences, or similarities of bacterial flora between individual samples or sample groups. GLC profiles changed significantly in the test group after the induction and discontinuation of the vegan diet but not in the control group at any time, whereas quantitative bacterial culture did not detect any significant change in fecal bacteriology in either of the groups. The results suggest that an uncooked extreme vegan diet alters the fecal bacterial flora significantly when it is measured by direct stool sample GLC of bacterial fatty acids.

Peltonen, R; Ling, W H; Hanninen, O; Eerola, E

1992-01-01

11

Combining NMR Spectroscopy and Gas-Liquid Chromatography for Analysis of the Fatty Acid Composition of Fenugreek Seed Oil (Trigonella foenum graecum L.)  

NASA Astrophysics Data System (ADS)

1H and 13C NMR spectroscopy established that fenugreek seed oil consists mainly of triacylglycerides. Oleic and linoleic acids are found preferentially in the 2 position and ?-linolenic acid is found preferentially in the 1,3 positions of the glycerol backbone. By combining NMR and gas-liquid chromatography, we have shown that fenugreek seeds contain 5.5 %-6.8 % oil, consisting mainly of unsaturated fatty acids (68.2 %-82.1 %): linoleic (31.3 %-46.8 %), ?-linolenic (15.1 %-36.6 %), and oleic (11.6 %-21.3 %). The highest unsaturated fatty acid content is found in the cultivars D-19, Ovary Gold, Blidet, Ovary 4 and the lowest fatty acid content is found in the Metha cultivar. The percentage of polyunsaturated fatty acids is higher in oils of fenugreek cultivars from northern regions (Belarus, Hungary, France).

Skakovskii, E. D.; Tychinskaya, L. Yu.; Mauchanava, V. A.; Karankevich, E. G.; Lamotkin, S. A.; Ahabalayeva, A. D.; Reshetnikov, V. N.

2013-11-01

12

Gas-liquid chromatography with a volatile "stationary" liquid phase.  

PubMed

A unique type of gas-liquid chromatography is described in which both mobile and "stationary" phases are composed of synthetic mixtures of helium and carbon dioxide. At temperatures below the critical point of the binary mixture and pressures above the vapor pressure of pure liquid carbon dioxide, helium and carbon dioxide can form two immiscible phases over extended composition ranges. A binary vapor phase enriched in helium can act as the mobile phase for chromatographic separations, whereas a CO2-rich liquid in equilibrium with the vapor phase, but condensed on the column wall, can act as a pseudostationary phase. Several examples of chromatographic separations obtained in "empty" capillary columns with no ordinary stationary liquid phase illustrate the range of conditions that produce such separations. In addition, several experiments are reported that confirm the proposed two-phase hypothesis. The possible consequences of the observed chromatographic phenomenon in the field of supercritical fluid chromatography with helium headspace carbon dioxide are discussed. PMID:12033313

Wells, P S; Zhou, S; Parcher, J F

2002-05-01

13

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

14

[Development of methods for determining acrylamide in food products by gas-liquid chromatography].  

PubMed

The method of determination of acrylamide in various food (milk powder, potato chips, instant coffee) by gas-liquid chromatography after pre-bromination was developed. Studies have shown the possibility of using bromination of acrylamide to give it the necessary properties for better extraction, purification and detection. Also revealed the possibility of qualitative and quantitative determine a acrylamide in food by gas-liquid chromatography with detection by electron capture detector. PMID:22232888

Bessonov, V V; Malinkin, A D; Perederiaev, O I; Bogachuk, M N; Volkovich, S V; Medvedev, Iu V

2011-01-01

15

Use of prototype automated blood culture system and gas-liquid chromatography for the analysis of continuous ambulatory peritoneal dialysis associated infection.  

PubMed Central

AIMS: (1) To compare the recovery of organisms from continuous ambulatory peritoneal dialysis (CAPD) effluent fluid obtained from patients with clinical evidence of peritonitis, with an automated system (AS) and the Septichek blood culture system; (2) to evaluate the times to detection of organisms with the two systems; (3) to identify anaerobes from CAPD samples by extended anaerobic culture and gas-liquid chromatography (GLC). METHODS: 168 CAPD effluent fluid samples were studied, representing 157 episodes of peritonitis in 97 patients. CAPD samples were inoculated into two AS bottles-one anaerobic, one aerobic-and a Septichek bottle; samples were also examined for cell count, Gram stain, and direct culture. Culture bottles were then subcultured onto various media, and any organisms isolated were identified. After routine culture, GLC was performed on culture fluid in the anaerobic AS and Septichek bottles. When volatile fatty acids were detected, the broths were cultured anaerobically on specialised medium for a further five days. RESULTS: 147 organisms were isolated from the 168 samples: 96 (57%) yielded growth of significant organisms by direct culture, as compared to 129 (76.8%) by both AS and Septichek. There was no significant difference in isolation rates between AS and Septichek, but time to detection was more rapid with the AS system (p < 0.002). GLC showed volatile fatty acid in 15 specimens; of these, 14 subsequently grew anaerobic organisms. CONCLUSIONS: AS was comparable to Septichek for numbers of isolations. Speed to detection was faster with the AS, which may be an advantage in management of patients with CAPD peritonitis. GLC showed anaerobes in several cases which would not have been detected without prolonged anaerobic culture; thus anaerobic cultures are recommended for patients who are unresponsive to antimicrobials or who have evidence of bowel perforation.

Catchpole, C R; Macrae, F; Brown, J D; Palmer, M; Healing, D E; Richards, N T; Elliott, T S

1997-01-01

16

[Use of gas-liquid chromatography for the study of nitrilases and amidases (author's transl)].  

PubMed

A gas-liquid chromatographic procedure is described for the determination of nitrilasic and amidasic activities. This method allows to monitor the kinetics of the hydrolysis of volatile nitriles and amides and because of its sensitivity, to determine the Michaelis constants Km of the acetonitrilase and the acetamidase of Brevibacterium R 312. For these enzymes, a correlation is shown between the kinetics monitored by proton nuclear magnetic resonance spectroscopy and gas-liquid chromatography. PMID:744778

Jallageas, J C; Arnaud, A; Galzy, P

1978-12-01

17

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

18

Analysis of C 18:1 cis and trans fatty acid isomers by the combination of gas-liquid chromatography of 4,4-dimethyloxazoline derivatives and methyl esters  

Microsoft Academic Search

Trans fatty acids in foods are usually analyzed by gas-liquid chromatography (GLC) of fatty acid methyl esters (FAME). However,\\u000a this method may produce erroneously low values because of insufficient separation between cis and trans isomers. Separation can be optimized by preceding silver-ion thin-layer chromatography (Ag-TLC), but this is laborious. We\\u000a have developed an efficient method for the separation of 18-carbon

Antti Aro; Truus Kosmeijer-Schuil; Peter van de Bovenkamp; Paul Hulshof; Peter Zock; Martijn B. Katan

1998-01-01

19

The differentiation and assay of vitamins D2 and D3 by gas-liquid chromatography  

PubMed Central

1. A method is described for the differentiation and determination of as little as 0·2?g. of vitamins D2 and D3 by gas–liquid chromatography. 2. The vitamins are converted by treatment with antimony trichloride into isovitamins D2 and D3, which show single, separate peaks on gas–liquid chromatography, unlike the unmodified vitamins, which give twin peaks due to the formation of pyro and isopyro derivatives. 3. Since isovitamins D2 and D3 remain together in all steps of the procedure except during gas–liquid chromatography, one may be used as an internal standard for the other. 4. The use of an internal standard reduces the importance of loss during sample preparation and increases precision. 5. The application of the method to biological materials is demonstrated.

Murray, T. K.; Day, K. C.; Kodicek, E.

1966-01-01

20

Gas-Liquid Chromatographic Analysis of Milk Fatty Acids: A Review1  

Microsoft Academic Search

Application of gas-liquid chromatography (GLC) to the analysis of milk fatty acids has allowed the rapid separation and identi- fication of these acids. To date, at least 142 acids have been reported, though many are present only in trace amounts. Sat- urated, unsaturated (cis and trans), branched-chain, hydroxy, and keto acids, as well as a cyclic acid, have been discov-

R. G. Jensen; J. G. Quinn; D. L. Carpenter; J. Sampugna

1967-01-01

21

The Separation and Identification of Straight Chain Hydrocarbons: An Experiment Using Gas-Liquid Chromatography.  

ERIC Educational Resources Information Center

An experiment using gas-liquid chromatography is discussed, introducing the student to concept of dead volume and its measurement, idea and use of an internal reference compound, and to linear relationship existing between measurements of a separation on two different stationary phases. (Author/SK)

Benson, G. A.

1982-01-01

22

Determination of reducing end sugar residues in oligo- and polysaccharides by gas–liquid chromatography  

Microsoft Academic Search

Reducing end sugar residues in maltodextrins and arabinoxylans are determined as alditol acetates by gas–liquid chromatography following reduction, acid hydrolysis and acetylation of the samples. After this conversion to alditol acetates, the reducing end sugars are thus separated from their acetylated aldose counterparts. The method allows to identify individual reducing end sugars quantitatively and is a good alternative for colorimetric

C. M. Courtin; H. Van den Broeck; J. A. Delcour

2000-01-01

23

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...

24

Investigation of the composition of coking naphthalene impurities by gas-liquid chromatography  

SciTech Connect

An investigation of the impurities present in marketable naphthalene was presented. The concentrations of the impurities were determined by gas-liquid chromatography. Three different types of naphthalene fractions were tested--fusion, pressed, and centrifuged. It was determined that the total concentration of impurities reached 0.20-0.25 wt.%. Also, the pressed and fusion naphthalenes contained benzonitrile, dimethylnaphthalenes, diphenyl, acenaphthene, and diphenyleneoxide, which were not present in the centrifuged naphthalene.

Nabivach, V.M.; Gerasimenko, V.A.; Ryabozad, A.S.; Voitenko, B.I.; Grumberg, L.R.; Chernyshov, Y.A.; Shvarts, S.G.

1982-01-01

25

Optimizing methylation conditions for gas liquid chromatography assay of lactic and succinic acid in biological samples  

Microsoft Academic Search

Aqueous standard solutions of lactic and succinic acids were methylated for assay by gas-liquid chromatography. The efficiency of methylation using boron trifluoridemethanol reagent was compared to methylation using a sulfuric acid-methanol mixture; the ratio of sulfuric acid and methanol was also varied. Reactions were done at 100°C\\/5 min and at room temperature\\/20 hours. We found the sulfuric acid-methanol was most

K. S. Bricknell; I. Brook; S. M. Finegold

1979-01-01

26

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

27

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

28

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

2013-07-01

29

Determination of pinazepam and its metabolites in serum, urine and brain by gas-liquid chromatography and mass spectrometry.  

PubMed

A sensitive and specific assay, involving electron capture gas-liquid chromatography, has been developed for the identification of pinazepam and its metabolites in serum, urine and brain samples from dogs and rats after single or repeated oral administration of the drug. Serum and urine samples from healthy humans after a single oral administration have also been analysed. The identity of gas-liquid chromatographic peaks has been established by mass spectrometry. In blood serum and brain, only pinazepam and its N-depropargylated product (demethyldiazepam) were found; from urine, 3-hydroxypinazepam and oxazepam were also recovered. The sensitivity of the gas-liquid chromatographic method is of the order of 5-10 ng of pinazepam and 15-20 ng of the other three benzodiazepines per ml of serum. PMID:1150839

Trebbi, A; Gervasi, G B; Comi, V

1975-07-16

30

Scaling analysis of gas-liquid two-phase flow pattern in microgravity  

NASA Technical Reports Server (NTRS)

A scaling analysis of gas-liquid two-phase flow pattern in microgravity, based on the dominant physical mechanism, was carried out with the goal of predicting the gas-liquid two-phase flow regime in a pipe under conditions of microgravity. The results demonstrated the effect of inlet geometry on the flow regime transition. A comparison of the predictions with existing experimental data showed good agreement.

Lee, Jinho

1993-01-01

31

Quantitative gas liquid chromatographic analysis of butterfat triglycerides  

Microsoft Academic Search

Gas liquid chromatographic triglyceride separation by carbon number, and integration of the area response obtained in the\\u000a hydrogen flame ionization detector, has permitted the calculation of the following molar proportions for the various triglyceride\\u000a types in a blended butterfat sample: C24 0.5, C25 0.08, C26 0.57, C27 0.18, C28 0.81, C29 0.17, C30 1.15, C31 0.2, C32 3.1, C33 0.34,

A. Kuksis; M. J. McCarthy; J. M. R. Beveridge

1963-01-01

32

Multi-scale analysis of gas–liquid interaction and CFD simulation of gas–liquid flow in bubble columns  

Microsoft Academic Search

The ratio of effective drag coefficient to bubble diameter is of critical importance for CFD simulation of gas–liquid flow in bubble columns. In this study, a novel model is proposed to calculate the ratio on the basis of the Dual-Bubble-Size (DBS) model. The motivation of the study is that a stability condition reflecting the compromise between different dominant mechanisms can

Ning Yang; Zongying Wu; Jianhua Chen; Yuhua Wang; Jinghai Li

2011-01-01

33

Gas-liquid chromatography-mass spectrometry investigation of tropane alkaloids in Hyoscyamus albus L. from Morocco.  

PubMed

Thirty-four alkaloids were identified in the organs of Hyoscyamus albus L. by gas-liquid chromatography-mass spectrometry (GLC-MS). Eight new compounds for the roots, eleven for the stems, twelve for the leaves, nineteen for the flowers, and seven for the seeds were detected. The alkaloids 5-(2-oxopropyl)-hygrine (8) and phygrine (20) are new for this species and 3-(hydroxyacetoxy)tropane (9), 6,7-dehydro-3-phenylacetoxytropane (15), 3-(2'-phenylpropionyloxy)tropane (17), 6,7-dehydro-3-apotropoyloxytropane (18), 3-(3'-methoxytropoyloxy)tropane (23), and aponorscopolamine (25) are described for the first time for the genus Hyoscyamus. Hyoscyamine was the main alkaloid in the plant organs. PMID:23198403

El Bazaoui, Ahmed; Bellimam, My Ahmed; Lançar, Ibn Toumert; Soulaymani, Abdelmajid

2012-01-01

34

Chromatographic studies on fatty acid dinners: Gas-liquid chromatography, high performance liquid chromatography and thin-layer chromatography  

Microsoft Academic Search

Methods for separation of various structural entities of dimers from heated fats and oils are not yet available. A series\\u000a of dimers, representative of these, which may be formed in thermal oxidative reactions of fats and oils have recently been\\u000a made available. In this study, the results of the analysis of a mixture of standard synthetic dimers, differing in polarity

C. N. Chrlslopoulouo; E. G. Perklnsb

1989-01-01

35

Radiometric studies with gas-liquid and thin-layer chromatography for rapid demonstration of hemin dependence and characterization of Mycobacterium haemophilum  

Microsoft Academic Search

Eight isolates of Mycobacterium haemophilum were evaluated by radiometric methods to determine whether this test system could support the growth of these organisms as well as demonstrate their growth requirements for iron complexes such as hemin, ferric ammonium citrate, and blood. In addition, gas-liquid and thin-layer chromatography were evaluated to determine whether these procedures could further differentiate M. haemophilum from

J. J. Damato; M. T. Collins

1984-01-01

36

Determination and Speciation of Mercury in a Dental WorkPlace by Cold Vapour Atomic Absorption Spectrometry and Gas-Liquid Chromatography  

Microsoft Academic Search

Cold Vapour Atomic Absorption Spectrometry (CVAAS) and Gas-Liquid Chromatography (GLC) have been used for determination and speciation of mercury. Total mercury, methylmercury, ethylmercury and phenylmercury concentrations in urine samples taken from students and staff of a dental work-place were investigated. Air samples were also analyzed. Detection limits, as three times the standard deviation, and in units of ng analyte per

M. Akif; Eçkin; Sezer Aygün; O. Yavuz Ataman

1986-01-01

37

Gas-liquid chromatography of cellular fatty acids for identification of staphylococci.  

PubMed Central

A commercially available, computer-assisted microbial identification system (MIS) employs gas-liquid chromatographic analyses of bacterial fatty acids. The MIS was used to identify 470 isolates of Staphylococcus species. The accuracy of the MIS was compared with the accuracies of conventional methods. There was a complete agreement between the MIS and conventional methods in the identification of 413 (87.8%) strains. For 36 of 45 misidentified strains, the correct identification was listed by the MIS as a choice but not as the first choice. Twelve strains could not be matched. All strains of Staphylococcus cohnii, S. epidermidis, S. intermedius, S. lugdunensis, S. schleiferi, S. sciuri, S. simulans, and S. xylosus were correctly identified. Two species, S. hominis and S. saprophyticus, accounted for 52.6% (30 of 57) of the misidentifications. Seventy-eight organisms were retested. Identification of 73 organisms remained unchanged, and for five organisms, the second choice became first and vice versa. The overall performance of the MIS is acceptable, and the system can be used as an alternate identification method for staphylococci.

Stoakes, L; John, M A; Lannigan, R; Schieven, B C; Ramos, M; Harley, D; Hussain, Z

1994-01-01

38

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

PubMed

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

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

2012-07-01

39

Gas-Liquid Chromatographic Analysis of Indole-3-acetic Acid Myoinositol Esters in Maize Kernels 1  

PubMed Central

An improved method of fractionating the myoinositol esters of indoleacetic acid (IAA) from maize kernels by gas-liquid chromatography has been developed. Mass spectrometry was employed as an aid in identification of the esters. Maize kernels contain three groups of esters of IAA: (a) IAA myoinositols, (b) IAA myoinositol arabinosides, and (c) IAA myoinositol galactosides. Each group has three chromatographically distinguishable isomers. The glycosylinositols described are unique in that carbon 1 of the sugar is attached to the hydroxyl at C-5 of the myoinositol.

Ueda, Minoru; Ehmann, Axel; Bandurski, Robert S.

1970-01-01

40

Differentiation of Escherichia coil and Aerobacter aerogenes by Gas Liquid Chromatography  

Microsoft Academic Search

Six isolates of Aerobacter aerogenes; one Pseudomonas aergenoidcs ; five Escherichia coli; one Escherichia freundii; and one Escherichia intermedia were obtained from different sources and classified according to Bergey's 5(anual. Cultures of each were prepared in heat- and vacuum-treated milk and incubated 30 hr at 35 C. An attempt was made to differentiate these species by gas chromatography (GLC) of

R. E. BAWDON; R. BASSETTE

41

DETERMINATION OF THE INSECT GROWTH REGULATOR METHOPRENE IN NATURAL WATERS BY CAPILLARY GAS-LIQUID CHROMATOGRAPHY  

EPA Science Inventory

Residues of methoprene were measured in natural waters by capillary as liquid chromatography (GLG). Methoprene was extracted in the field by liquid-liquid partitioning with dichloromethane, transPorted to the laboratory, and extracted a second time with hexane. The extracts were ...

42

Rapid Analysis of Antifreeze Using Gas-Liquid Chromatography.  

National Technical Information Service (NTIS)

Glycols and glycol ethers are used as freezing point depressants in permanent type antifreeze formulations, the type and amount being dictated by environmental conditions. The formulation and maintenance of a suitable antifreeze for automotive application...

G. G. Esposito R. C. Jamison

1969-01-01

43

Elevated mannose levels detected by gas-liquid chromatography in hydrolysates of serum from rats and humans with candidiasis.  

PubMed Central

We have developed a gas-liquid chromatographic method for identification of mannose in serum hydrolysates by utilizing peracetylated aldononitrile derivatives. Experimentally infected rats and human subjects with candidiasis were studied. Peaks in unknown samples were identified by co-chromatography of reference carbohydrates. Inositol was used as an internal standard. Mannose was identified in hydrolysates of normal rat (391.85 +/- 66.18 micrograms/ml) and human (297.87 +/- 77.81 micrograms/ml) sera. Significantly increased concentrations of mannose (greater than 526.21 micrograms/ml) were demonstrated in hydrolysates of sera from 26 of 36 (72%) experimentally infected rats tested 1 or more days after onset of infection. Significant increases (greater than 453.49 micrograms/ml) were also seen in humans with localized (6/15), transient (2/2), and disseminated (5/7) candidiasis. The concentrations were highest in patients with candidemia occurring either transiently or as part of disseminated infection. The concentrations in patients with localized candidiasis were lower but were still significantly greater than control. These data suggest that changes in mannose concentration, as measured, may serve as markers of candidiasis. The amount of mannose present may be in part a function of the extent of the infection.

Marier, R L; Milligan, E; Fan, Y D

1982-01-01

44

Gas-liquid chromatography-mass spectrometry of the 4,4-dimethyloxazoline derivatives of ?5-unsaturated polymethylene-interrupted fatty acids from conifer seed oils  

Microsoft Academic Search

The fatty acids from the seed oils of three Conifer species (one Pinaceae,Pinus pinaster, and two Cupressaceae,Chamaecyparis lawsoniana andBiota orientalis) have been analyzed as their 4,4-dimethyloxazoline (DMOX) derivatives by gas-liquid chromatography coupled with mass spectrometry.\\u000a The structures of six ?5-unsaturated polymethylene-interrupted fatty acids (?5-UPIFA) were established, confirming previous\\u000a studies in which they were identified by their equivalent chainlengths (ECL) and

Olivier Berdeaux; Robert L. Wolff

1996-01-01

45

Characterization of Mycobacterium paratuberculosis of bovine, caprine, and ovine origin by gas-liquid chromatographic analysis of fatty acids in whole-cell extracts.  

PubMed

The cellular fatty acid composition of Mycobacterium paratuberculosis from bovine, ovine, and caprine origin (grown on Herrold's egg yolk medium) was determined by gas-liquid chromatography (GLC) and mass spectrometry and was compared with that of 19 other Mycobacterium spp. A species-specific fatty acid of M paratuberculosis was not demonstrable. Gas-liquid chromatographic analysis of cellular fatty acids was used to develop flow charts for the rapid identification of M paratuberculosis and other Mycobacterium spp. Two charts for distinguishing organisms were developed; one chart was based on GLC alone and the other based on GLC, growth rate, and chromogenicity. Seemingly, the GLC was reliable for detecting Mycobacterium spp rapidly. PMID:4051303

Chiodini, R J; Van Kruiningen, H J

1985-09-01

46

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

47

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

48

[Study fo sterols from brown seaweeds of the genus Cytoseira. Identification by gas-liquid chromatography coupled with mass spectrometry (author's transl)].  

PubMed

All the samples of brown seaweeds (Cystoseria) that we have studied present the same deltas sterols fucosterol, 22 trans-dehydrocholesterol, brassicasterol, 24-methylene cholesterol as well as cystosterol, a new C27 sterol. This sterol has been submitted to gas-liquid chromatographic-mass spectrometric analysis. PMID:857897

Francisco, C; Combaut, G; Teste, J; Maume, B F

1977-04-26

49

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

50

Qualitative and quantitative evaluation of mono- and disaccharides in d-fructose, d-glucose and sucrose caramels by gas–liquid chromatography–mass spectrometry  

Microsoft Academic Search

The monosaccharide (d-fructose, d-glucose, anhydrosugars), disaccharide (glucobioses) and pseudodisaccharide (di-d-fructose dianhydrides) content of d-fructose, d-glucose and sucrose caramels has been determined by gas–liquid chromatography–mass spectrometry (GLC–MS) of their trimethylsilyl (TMS) or TMS–oxime derivatives. The chromatographic profiles revealed significant differences in the disaccharide\\/pseudodisaccharide distribution depending on the caramel source: a d-fructose caramel contains prominent proportions of di-d-fructose dianhydrides, a d-glucose caramel

Valérie Ratsimba; José Manuel Garc??a Fernández; Jacques Defaye; Henri Nigay; Andrée Voilley

1999-01-01

51

High-performance liquid and gas-liquid chromatography of isomeric phenoxathiins. Use of organo-clay to increase selectivity  

Microsoft Academic Search

Bentone-34, a selective adsorbent, has been studied for use in high-performance liquid chromatography (HPLC) to separate isomeric phenoxathiin derivatives. We have compared the performance of this adsorbent in gas chromatography and liquid chromatography. We have obtained better and faster analyses of these isomeric phenoxathiins by high-pressure liquid-solid chromatography. This method is more flexible, as we have the choice of a

M. Lafosse; G. Keravis; J. P. Coïc; G. Saint-Ruf

1978-01-01

52

Modification of the gas-liquid chromatography procedure and evaluation of a new column packing material for the identification of anaerobic bacteria.  

PubMed Central

Gas-liquid chromatography has become a useful aid for the identification of anaerobic bacteria in the clinical laboratory. When many extracted samples are to be analyzed, time is of prime importance. By altering the operating conditions of the chromatograph, we have decreased the total elution time of the volatile fatty acids examined to approximately 12 min. There is, however, a decrease in the ability to resolve propionic and isobutyric acids. A new column packing material, SP-1220 (Supelco), was found to give excellent separation of propionic and isobutyric acids as well as demonstrating the presence of formic acid which was not seen with the previously used Resoflex. Extracts of clinical isolates of anaerobic organisms were processed using the altered conditions and new column packing material with excellent resolution of all acids. The use of SP-1220 in the clinical laboratory will facilitate the identification of anaerobic bacteria.

Hauser, K J; Zabransky, R J

1975-01-01

53

Statistical analysis of the phase holdup characteristics of a gas-liquid-solid fluidized bed  

Microsoft Academic Search

Experiments have been carried out to study the individual phase holdup characteristics in a cocurrent three-phase fluidized bed. An antenna type modified air sparger has been used in the gas-liquid distributor section, for uniform mixing of the fluids with the gas moving as fine bubbles to the fluidizing section. This arrangement also reduces the pressure drop encountered through a conventional

H. M. Jena; B. K. Sahoo; G. K. Roy; B. C. Meikap

2009-01-01

54

Experimental Analysis and Computational Modelling of Gas–Liquid Stirred Vessels  

Microsoft Academic Search

The aim of this work is to investigate the turbulent hydrodynamics of a gas–liquid stirred tank of standard geometry through experiments and simulations. The 2-D velocity fields are obtained by a two-phase PIV technique, consisting of a pulsed Nd:YAG laser, emitting light at 532nm, and two cameras, each provided with a filter, that allow to discriminate between the light scattered

G. Montante; A. Paglianti; F. Magelli

2007-01-01

55

Characteristic Analysis of Gas\\/Liquid Two-Phase Flow Regimes Based on Wavelet Packet Entropy  

Microsoft Academic Search

The identification of flow regime is the basis for measuring flow parameters in two-phase flow accurately. Because of the complexity of phase interaction in gas-liquid two-phase flow, it is difficult to discern its flow regime objectively. In this paper, the 208 measured data from electrical resistance tomography (ERT) are arranged into series based on section to investigate the dynamic characteristics

Chun Fu; Feng Dong

2010-01-01

56

Gas?liquid chromatographic analysis of oxadiazon residues in turfgrass thatch and soil using a solid?phase extraction technique  

Microsoft Academic Search

A simple and inexpensive technique for analysis of oxadiazon (5?tert?butyl?3?(2,4?dichloro?5?isopropoxyphenyl)?1,3,4,?oxadiazol?2(3H)?=one) residues in thatch and soil involving solid?phase extraction\\/purification and final gas?liquid chromatographic determination with nitrogen?phosphorus specific detection has been developed. The method, sensitive to 0.08ppm for thatch and 0.04ppm for soil, significantly reduces the use of organic solvents and labor, and allows simultaneous analysis of multiple samples.

A. A. Krause; H. D. Niemczyk

1990-01-01

57

Lagrangian coherent structures analysis of gas-liquid flow in a bubble column  

NASA Astrophysics Data System (ADS)

The objective of this paper is to apply a new identifying method to investigating the gas-liquid two-phase flow behaviors in a bubble column with air injected into water. In the numerical simulations, the standard k-? turbulence model is employed to describe the turbulence phenomenon occurring in the continuous fluid. The Finite-Time Lyapunov Exponent (FTLE) and Lagrangian Coherent Structures (LCS) are applied to analyze the vortex structures in multiphase flow. Reasonable agreements are obtained between the numerical and experimental data. The numerical results show that the evolution of gas-liquid in the column includes initial and periodical developing stages. During the initial stage, the bubble hose is forming and extending along the vertical direction with the vortex structures formed symmetrically. During the periodical developing stage, the bubble hose starts to oscillate periodically, and the vortexes move along the bubble hose to the bottom of column alternately. Compared to the Euler-system-based identification criterion of a vortex, the FTLE field presents the boundary of a vortex without any threshold defined and the LCS represents the divergence extent of infinite neighboring particles. During the initial stage, the interfaces between the forward and backward flows are highlighted by the LCS. As for the periodical developing stage, the LCS curls near the vortex centers, providing a method of analyzing a flow field from a dynamical system perspective.

Wu, Qin; Wang, GuoYu; Huang, Biao; Bai, ZeYu

2014-04-01

58

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

59

Lagrangian coherent structures analysis of gas-liquid flow in a bubble column  

NASA Astrophysics Data System (ADS)

The objective of this paper is to apply a new identifying method to investigating the gas-liquid two-phase flow behaviors in a bubble column with air injected into water. In the numerical simulations, the standard k- ? turbulence model is employed to describe the turbulence phenomenon occurring in the continuous fluid. The Finite-Time Lyapunov Exponent (FTLE) and Lagrangian Coherent Structures (LCS) are applied to analyze the vortex structures in multiphase flow. Reasonable agreements are obtained between the numerical and experimental data. The numerical results show that the evolution of gas-liquid in the column includes initial and periodical developing stages. During the initial stage, the bubble hose is forming and extending along the vertical direction with the vortex structures formed symmetrically. During the periodical developing stage, the bubble hose starts to oscillate periodically, and the vortexes move along the bubble hose to the bottom of column alternately. Compared to the Euler-system-based identification criterion of a vortex, the FTLE field presents the boundary of a vortex without any threshold defined and the LCS represents the divergence extent of infinite neighboring particles. During the initial stage, the interfaces between the forward and backward flows are highlighted by the LCS. As for the periodical developing stage, the LCS curls near the vortex centers, providing a method of analyzing a flow field from a dynamical system perspective.

Wu, Qin; Wang, GuoYu; Huang, Biao; Bai, ZeYu

2014-06-01

60

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

61

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

62

Hilbert–Huang transform based signal analysis for the characterization of gas–liquid two-phase flow  

Microsoft Academic Search

This paper reports the application of the Hilbert–Huang Transform (HHT) to the dynamic characterization of gas–liquid two-phase flow in a horizontal pipeline. A differential pressure fluctuation signal of gas–liquid two-phase flow is adaptively decomposed into Intrinsic Mode Functions (IMFs) through the use of Empirical Mode Decomposition (EMD) methods. Based on the EMD, the associated time–frequency–energy distribution, i.e., the Hilbert spectrum,

Hao Ding; Zhiyao Huang; Zhihuan Song; Yong Yan

2007-01-01

63

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

64

Gas/Liquid and Liquid/Liquid Solvent Extraction in Flow Analysis with the Chromatomembrane Cell  

PubMed Central

Since twelve years the Chromatomembrane Cell has been proposed as a new and versatile device for extraxtion procedures in the flow based analysis. In the meantime a remarkable number of papers was submitted dealing with applications of the novel method to all the conceivable varieties of flow injection and sequential injection analysis. The device supports important analytical procedures such as sampling, sample preparation, and preconcentration each being combined with a phase transfer of the analyte. The Chromatomembrane Cell can be coupled to most of the modern detectors which work computer aided in the laboratories of today. Centrepiece of the cell is a block made from biporous hydrophobic PTFE, inside which polar (in the macropores) and nonpolar (in the micropores) solvents come into a close contact with each other and might flow independently with different flow rates. Microporous PTFE membranes prevent polar phases from their flowthrough into directions which are reserved for nonpolar fluids only. Thus, a strict control over the fluxes can be established at the analysts request. Especially, that PTFE block offers outstanding possibilities as a sampling unit for air monitoring.

Moskvin, Leonid N.; Simon, Juergen

2006-01-01

65

Determination of partition coefficients of refrigerants by gas liquid chromatographic headspace analysis.  

PubMed

Gas-water partition coefficients, K(w), and gas-solvent partition coefficients, K(s), have been determined for chlorodifluoromethane and for 1,1,1,3,3,3-hexafluoropropane by headspace analysis, using a very simple experimental procedure. These partition coefficients then yield water-solvent partition coefficients, P(s). Where comparisons can be made there is excellent agreement with literature values for K(w) and P(s). The obtained values of K(s) and P(s) can be used to obtain physicochemical properties, or descriptors, for the refrigerants. Combination of these descriptors with previous equations we have developed enables partition coefficients to be obtained for a host of systems. PMID:23089519

Abraham, Michael H; Gil-Lostes, Javier; Corr, Stuart; Acree, William E

2012-11-23

66

Quantitative Analysis of Urine Vapor and Breath by Gas-Liquid Partition Chromatography  

Microsoft Academic Search

When a human being is placed for several days on a completely defined diet, consisting almost entirely of small molecules that are absorbed from the stomach into the blood, intestinal flora disappear because of lack of nutrition. By this technique, the composition of body fluids can be made constant (standard deviation about 10%) after a few days, permitting significant quantitative

Linus Pauling; Arthur B. Robinson; Roy Teranishi; Paul Cary

1971-01-01

67

The analysis of alkyl aryl sulfonates by micro desulfonation and gas chromatography  

Microsoft Academic Search

The structural analysis of micro quantities of alkyl aryl sulfonates by presently known chemical and spectroscopic techniques\\u000a has been an exceedingly difficult task. The formidable nature of such analyses is due largely to the essential nonvolatility\\u000a of the sulfonates, a fact which precludes the application of gas-liquid chromatography and mass spectrometric techniques.\\u000a \\u000a The present paper describes an approach wherein gas

E. A. Setzkorn; A. B. Carel

1963-01-01

68

Qualitative and quantitative evaluation of mono- and disaccharides in D-fructose, D-glucose and sucrose caramels by gas-liquid chromatography-mass spectrometry. Di-D-fructose dianhydrides as tracers of caramel authenticity.  

PubMed

The monosaccharide (D-fructose, D-glucose, anhydrosugars), disaccharide (glucobioses) and pseudodisaccharide (di-D-fructose dianhydrides) content of D-fructose, D-glucose and sucrose caramels has been determined by gas-liquid chromatography-mass spectrometry (GLC-MS) of their trimethylsilyl (TMS) or TMS-oxime derivatives. The chromatographic profiles revealed significant differences in the disaccharide/pseudodisaccharide distribution depending on the caramel source: a D-fructose caramel contains prominent proportions of di-D-fructose dianhydrides, a D-glucose caramel mainly D-glucobioses, and a sucrose caramel similar proportions of both disaccharide/pseudodisaccharide series. It is noteworthy that di-D-fructose dianhydrides are found in all three types of caramels and might then be used as specific tracers of the authenticity of caramel, i.e., a product resulting from the controlled heat treatment of food-grade carbohydrates for use as food additives. PMID:10399331

Ratsimba, V; García Fernández, J M; Defaye, J; Nigay, H; Voilley, A

1999-06-01

69

Wavelet packet entropy feature extraction and characteristics analysis for gas\\/liquid two-phase flow regimes  

Microsoft Academic Search

Identification of flow regime is the basis for measuring flow parameters in two-phase flow accurately. Because of the complexity of phase interaction in gas-liquid two-phase flow, it is difficult to discern its flow regime objectively. The 208 measured data from electrical resistance tomography (ERT) are arranged into series based on section to derive the wavelet packet entropy and investigate the

Chun Fu; Feng Dong

2011-01-01

70

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

71

Gas-liquid chromatographic and gas-liquid-mass spectometric determination of fenvalerate and permethrin residues in grasshoppers and duck tissue samples  

USGS Publications Warehouse

A procedure is described for determining fenvalerate and permethrin residues in grasshoppers and duck tissues. Samples are Soxhlet-extracted with hexane and cleaned up by gel permeation chromatography with an in-line alumina column. Samples are analyzed by gas-liquid chromatography with electron capture detection, and confirmed by gas-liquid chromatography-mass spectrometry. The average recovery from fortified tissues was 97%.

Reichel, W.L.; Kolbe, E.J.; Stafford, C.J.

1981-01-01

72

Determination of solute partition behavior with room-temperature ionic liquid based micellar gas-liquid chromatography stationary phases using the pseudophase model.  

PubMed

The use of micelles in ionic liquid based gas-chromatography stationary phases was evaluated using equations derived for a "three-phase" model. This model allows the determination of all three partition coefficients involved in the system, and elucidates the micellar contribution to retention and selectivity. Four types of micellar-ionic liquid columns were examined in this study: 1-butyl-3-methylimidazolium chloride with sodium dodecylsulfate or dioctyl sulfosuccinate, and 1-butyl-3-methylimidazolium hexafluorophosphate with polyoxyethylene-100-stearyl ether or polyoxyethylene-23-lauryl ether. The partition coefficients were measured for a wide range of probe molecules capable of a variety of types and magnitudes of interactions. In general, most probe molecules preferentially partitioned to the micellar pseudophase over the bulk ionic liquid component of the stationary phase. Therefore, addition of surfactant to the stationary phase usually resulted in greater solute retention. It is also shown that the selectivity of the stationary phase is significantly altered by the presence of micelles, either by enhancing or lessening the separation. The effects of surfactant on the interaction parameters of the stationary phase are determined using the Abraham solvation parameter model. The addition of sodium dodecylsulfate and dioctyl sulfosuccinate to 1-butyl-3-methylimidazolium chloride stationary phases generally increased the phase's hydrogen bond basicity and increased the level of dispersion interaction. Polyoxyethylene-100-stearyl ether and polyoxyethylene-23-lauryl ether surfactants, however, enhanced the pi-pi/n-pi, polarizability/dipolarity, and hydrogen bond basicity interactions of 1-butyl-3-methylimidazolium hexafluorophosphate to a greater degree than the ionic surfactants with 1-butyl-3-methylimidazolium chloride. However, these nonionic surfactants appeared to hinder the ability of the stationary phase to interact with solutes via dispersion forces. Therefore, it is possible to effectively predict which analytes will be most highly retained by these micellar-ionic liquid stationary phases. PMID:16569411

Lantz, Andrew W; Pino, Verónica; Anderson, Jared L; Armstrong, Daniel W

2006-05-19

73

Initiation of roll waves in gas-liquid flows  

SciTech Connect

Measurements of the effect of liquid viscosity on the initiation of roll waves in a horizontal gas-liquid flow are presented. These results are interpreted by an analysis based on the calculation of the growth of long wavelength disturbances.

Andreussi, P.; Asali, J.C.; Hanratty, T.J.

1985-01-01

74

Quantitative gas-liquid chromatography of triglycerides  

Microsoft Academic Search

To determine optimum operating conditions, an extensive study was made of the variables affecting quantitative recovery and\\u000a resolution of model triglyceride mixtures. Parameters investigated included: flash heater temperature, carrier gas flow rate,\\u000a type of carrier gas, column length, glass and metal columns, temperature program rate, linearity of detector response, physical\\u000a design of gas chromatograph, and molecular species of triglyceride.\\u000a \\u000a Results

Carter Litchfield; R. D. Harlow; Raymond Reiser

1965-01-01

75

An electron-capture gas-liquid-chromatographic method for the determination of prostaglandin F2? in biological fluids  

PubMed Central

A sensitive electron-capture gas–liquid-chromatographic method for the determination of sub-nanogram quantities of prostaglandin F2? was developed. The method is based on the sub-microgram scale conversion of the prostaglandin into the electron-capturing pentafluorobenzyl ester, and analysis of the latter as the tris-trimethylsilyl ether. The lower limit of detection was 12.5pg of the ester injected `on-column' as the silylated product. The method was successfully applied to the determination of prostaglandin F2? in monkey plasma. The specificity of the analytical procedure was increased by incorporating a thin-layer chromatographic fractionation before gas–liquid chromatography. The utility of the analytical methodology developed was demonstrated by its application to the determination of plasma concentrations of intact prostaglandin F2? in a Rhesus monkey, after subcutaneous administration of a single dose of prostaglandin F2?. The electron-capture gas–liquid-chromatographic assay is compared with the radioimmunoassay and the gas–liquid-chromatographic–mass-spectrometry assay for the determination of prostaglandin F2?.

Wickramasinghe, Asoka J. F.; Shaw, Robert S.

1974-01-01

76

STUDIES ON THE IDENTIFICATION OF HARMFUL RADIOLYTIC PRODUCTS OF 30% TBP-N-DODECANE-HNO3 BY GAS-LIQUID CHROMATOGRAPHY. II. FORMATION AND CHARACTERIZATION OF HIGH MOLECULAR WEIGHT ORGANOPHOSPHATES  

Microsoft Academic Search

Gamma radiolysis of Purex solvent, 30% tri-n-butylphosphate-n-dodecane-HNO3 is observed to yield many undesirable metal complexing species. A method for identifying the gas-liquid chromatographic (GLC) signatures of high molecular weight organophosphates (HMPs) through a nitrogen- and phosphorous-selective detector is described. Fractionation of the radiolyzed solvent by vacuum distillation resulted in the enrichment of HMP species in the high boiling, viscous residue

S. C. Tripathi; A. Ramanujam; K. K. Gupta; P. Bindu

2001-01-01

77

Supersonic Gas-Liquid Cleaning System  

NASA Technical Reports Server (NTRS)

The Supersonic Gas-Liquid Cleaning System Research Project consisted mainly of a feasibility study, including theoretical and engineering analysis, of a proof-of-concept prototype of this particular cleaning system developed by NASA-KSC. The cleaning system utilizes gas-liquid supersonic nozzles to generate high impingement velocities at the surface of the device to be cleaned. The cleaning fluid being accelerated to these high velocities may consist of any solvent or liquid, including water. Compressed air or any inert gas is used to provide the conveying medium for the liquid, as well as substantially reduce the total amount of liquid needed to perform adequate surface cleaning and cleanliness verification. This type of aqueous cleaning system is considered to be an excellent way of conducting cleaning and cleanliness verification operations as replacements for the use of CFC 113 which must be discontinued by 1995. To utilize this particular cleaning system in various cleaning applications for both the Space Program and the commercial market, it is essential that the cleaning system, especially the supersonic nozzle, be characterized for such applications. This characterization consisted of performing theoretical and engineering analysis, identifying desirable modifications/extensions to the basic concept, evaluating effects of variations in operating parameters, and optimizing hardware design for specific applications.

Kinney, Frank

1996-01-01

78

Ion Chromatography Analysis of Dibutyl Phosphoric Acid.  

National Technical Information Service (NTIS)

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) concentra...

R. J. Ray

1998-01-01

79

Isolation and purification of deoxynivalenol and a new trichothecene by high pressure liquid chromatography  

Microsoft Academic Search

Deoxynivalenol (3,7,15-trihydroxy-12,l3-epoxytrichothec-9-ene-8-one) was extracted from corn with methanol\\/water (80:20, v\\/v)\\u000a and purified by liquid:liquid partitioning and by preparative high pressure liquid chromatography (HPLC). This procedure was\\u000a used to prepare mg quantities of toxin from field-inoculated corn for reference standards. Analysis of the isolated deoxynivalenol\\u000a by analytical HPLC, gas liquid chromatography (GLC) and gas liquid chromatography\\/mass spectroscopy (GLC\\/MS) indicated the\\u000a presence

G. A. Bennett; R. E. Peterson; R. D. Plattner; O. L. Shotwell

1981-01-01

80

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.

81

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

82

Gas-liquid chromatographic separation and spectrometric identification of nitrogen bases in hydrocracked shale oil naphtha  

Microsoft Academic Search

A tar-base concentrate from a hydrocracked shale oil naphtha was separated by gas-liquid partition chromatography using nonpolar and polar columns. Final cuts were analyzed by mass, infrared, and nuclear magnetic resonance spectrometry. Fifty individual compounds were identified and eight additional structures are proposed as possible components of the concentrate. Alkylpyridines comprised about 64% of the bases and alkylanilines about 33%;

K. B. Brown; P. G. Earnshaw; F. R. McDonald; H. B. Jensen

1970-01-01

83

Modelling Local Gas–Liquid Mass Transfer in Agitated Vessels  

Microsoft Academic Search

A rigorous gas–liquid mass transfer model based on Maxwell–Stefan diffusion and two-film theory was validated against dynamic oxygen transfer experiments and exit gas analysis with mass spectrometry. A multiblock stirred tank model, which consists of 21 ideally mixed subregions, was used to consider non-ideal mixing in the model validation. Mass transfer areas were obtained from population balances for bubbles with

M. Laakkonen; P. Moilanen; V. Alopaeus; J. Aittamaa

2007-01-01

84

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

85

Natural gas liquids remain strong petrochemical feedstock  

SciTech Connect

The supply of petrochemical feedstocks in the USA are discussed. The US petrochemical network starts with three main sources, i.e., olefins, aromatics, and natural gas. Petrochemical technology has been pushed to lower costs and improve yields in the face of a determined market drive from new petrochemical producing regions with vast supplies of low-cost gas liquids.

Greek, B.F.

1984-03-12

86

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

PubMed Central

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.

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

1979-01-01

87

Chromatography  

MedlinePLUS

... high pressure liquid, or ion exchange chromatography. In general, chromatography takes advantage of the differences in the chemicals you want to separate, such as their size, electric charge, or ability to stick to (bind) to ...

88

Chromatography  

NSDL National Science Digital Library

This site provides fundamental background information about chromatography, including plate theory, rate theory, the mechanisms of separations, and qualitative and quantitative aspects of chromatography. The format is a series of PowerPoint-like presentations available in PDF format.

Hardy, James K.

2011-05-16

89

Gas-liquid chromatography of the heptafluorobutyrate derivatives of the O-methyl-glycosides on capillary columns: a method for the quantitative determination of the monosaccharide composition of glycoproteins and glycolipids.  

PubMed

We have developed a method involving the formation of hepta-fluorobutyrate derivatives of O-methyl-glycosides liberated from glycoproteins and glycolipids following methanolysis. The stable derivatives of the most common monosaccharides of these glycoconjugates (Ara, Rha, Xyl, Fuc, Gal, Man, Glc, GlcNAc, GalNAc, Neu5Ac, KDN) can be separated and quantitatively and reproducibly determined with a high degree of sensitivity level (down to 25 pmol) in the presence of lysine as an internal standard. The GlcNAc residue bound to Asn in N-glycans is quantitatively recovered as two peaks. The latter were easily distinguished from the other GlcNAc residues of N-glycans, thus allowing a considerable improvement of the data on structure of N-glycans obtained from a single carbohydrate analysis. The most common contaminants present in buffers commonly used for the isolation of soluble or membrane-bound glycoproteins (SDS, Triton X-100, DOC, TRIS, glycine, and polyacrylamide or salts, as well as monosaccharide constituents of proteoglycans or degradation products of nucleic acids) do not interfere with these determinations. A carbohydrate analysis of glycoproteins isolated from a SDS/PAGE gel or from PDVF membranes can be performed on microgram amounts without significant interferences. Since fatty acid methyl esters and sphingosine derivatives are separated from the monosaccharide peaks, the complete composition of gangliosides can be achieved in a single step starting from less than 1 microg of the initial compound purified by preparative Silicagel TLC. Using electron impact ionization mass spectrometry, reporter ions for the different classes of O-methyl-glycosides (pentoses, deoxy-hexoses, hexoses, hexosamines, uronic acids, sialic acid, and KDN) allow the identification of these compounds in very complex mixtures. The mass of each compound can be determined in the chemical ionization mode and detection of positive or negative ions. This method presents a considerable improvement compared to those using TMS derivatives. Indeed the heptafluorobutyrate derivatives are stable, and acylation of amino groups is complete. Moreover, there is no interference with contaminants and the separation between fatty acid methyl-esters and O-methyl glycosides is achieved. PMID:10024663

Zanetta, J P; Timmerman, P; Leroy, Y

1999-03-01

90

Sampling and analysis of some aromatic, aliphatic and chlorinated hydrocarbon vapours in air, a gas-liquid chromatographic and colorimetric method  

Microsoft Academic Search

This paper describes the sampling of air and its analysis for mixtures of organic solvent vapours by personal and room air samplers. The application of a potassium carbonate to remove water vapour, and silica gel adsorption tube cooled by dry ice for collection of organic solvents were investigated. The development of a method for the extraction of organic solvents from

Masana Ogata; Hiroko Asahara; Takao Saeki

1975-01-01

91

Evaluation of fast gas chromatography and gas chromatography–mass spectrometry in the analysis of lipids  

Microsoft Academic Search

Fast and conventional gas chromatography (GC) techniques were applied to nine different lipidic matrices (butter, lard, tallow, and peanut, corn, sunflower, soya, olive, menhaden oils). Simultaneous methylic transesterification was performed on all samples prior to GC analysis. Several practical aspects concerning high speed analysis were investigated, such as the great increase in linear velocity, the use of fast temperature ramps,

Luigi Mondello; Alessandro Casilli; Peter Quinto Tranchida; Rosaria Costa; Biagina Chiofalo; Paola Dugo; Giovanni Dugo

2004-01-01

92

ANALYSIS OF TECHNICAL CHLORDANE BY GAS CHROMATOGRAPHY MASS SPECTROMETRY  

EPA Science Inventory

The composition of technical chlordane has been investigated by combined gas chromatography/mass spectrometry, employing a column commonly used for pesticide residue analysis. Partial or complete structure identification have been assigned to some 45 individual constituents. Many...

93

Phytanic acid: measurement of plasma concentrations by gas-liquid chromatography-mass spectrometry analysis and associations with diet and other plasma fatty acids.  

PubMed

Epidemiological data suggest that a diet rich in animal foods may be associated with an increased risk of several cancers, including cancers of the prostate, colorectum and breast, but the possible mechanism is unclear. It is hypothesised that phytanic acid, a C20 branched-chain fatty acid found predominantly in foods from ruminant animals, may be involved in early cancer development because it has been shown to up regulate activity of alpha-methylacyl-coenzyme A racemase, an enzyme commonly found to be over-expressed in tumour cells compared with normal tissue. However, little is known about the distribution of plasma phytanic acid concentrations or its dietary determinants in the general population. The primary aim of the present cross-sectional study was to determine circulating phytanic acid concentrations among ninety-six meat-eating, lacto-ovo-vegetarian and vegan women, aged 20-69 years, recruited into the Oxford component of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Meat-eaters had, on average, a 6.7-fold higher geometric mean plasma phytanic acid concentration than the vegans (5.77 v. 0.86 micromol/l; P < 0.0001) and a 47 % higher mean concentration than the vegetarians (5.77 v. 3.93 micromol/l; P = 0.016). The strongest determinant of plasma phytanic acid concentration appeared to be dairy fat intake (r 0.68; P < 0.0001); phytanic acid levels were not associated with age or other lifestyle factors. These data show that a diet high in fat from dairy products is associated with increased plasma phytanic acid concentration, which may play a role in cancer development. PMID:17868488

Allen, Naomi E; Grace, Philip B; Ginn, Annette; Travis, Ruth C; Roddam, Andrew W; Appleby, Paul N; Key, Timothy

2008-03-01

94

Supersonic gas-liquid cleaning system  

NASA Technical Reports Server (NTRS)

A system to perform cleaning and cleanliness verification is being developed to replace solvent flush methods using CFC 113 for fluid system components. The system is designed for two purposes: internal and external cleaning and verification. External cleaning is performed with the nozzle mounted at the end of a wand similar to a conventional pressure washer. Internal cleaning is performed with a variety of fixtures designed for specific applications. Internal cleaning includes tubes, pipes, flex hoses, and active fluid components such as valves and regulators. The system uses gas-liquid supersonic nozzles to generate high impingement velocities at the surface of the object to be cleaned. Compressed air or any inert gas may be used to provide the conveying medium for the liquid. The converging-diverging nozzles accelerate the gas-liquid mixture to supersonic velocities. The liquid being accelerated may be any solvent including water. This system may be used commercially to replace CFC and other solvent cleaning methods widely used to remove dust, dirt, flux, and lubricants. In addition, cleanliness verification can be performed without the solvents which are typically involved. This paper will present the technical details of the system, the results achieved during testing at KSC, and future applications for this system.

Caimi, Raoul E. B.; Thaxton, Eric A.

1994-01-01

95

Chromatography  

NSDL National Science Digital Library

In this activity, explore chromatography and the various colors that make up the ink in markers. Use this activity to investigate cohesion and adhesion. The online version of this activity is set up so that learners solve a mystery.

Boston, Wgbh

2002-01-01

96

Displacement chromatography applied to trace component analysis  

SciTech Connect

Displacement chromatography has been used primarily for the isolation of relatively large quantities of materials in preparative scale separations. The authors show that it also offers advantages for the enrichment of trace components. During displacement development, significant compression of the trace component bands occurs. This enrichment is studied both experimentally and theoretically. The theoretical model is based on the solution of the mass balance equations for nonlinear chromatography, assuming competitive Langmuir isotherms. The system studied experimentally consisted of parts-per-million levels of {beta}-naphthylamine and an impurity of the naphthylamine as the sample and diethyl phthalate as the displacer. The band profiles of the trace components were monitored by fluorescence detection while the displacer was monitored by UV absorbance. Wavelengths were chosen such that the profiles of the sample and the displacer could be monitored independently. Trace enrichment by band compression was achieved by increasing the displacer concentration. Experimental results show very narrow bands at enhanced concentrations as compared to the relatively broad Gaussian-shaped profiles observed in linear elution chromatography. The experimental results are in agreement with theoretical predictions of peak shape.

Ramsey, R.; Katti, A.M.; Guiochon, G. (Univ. of Tennessee, Knoxville (USA) Oak Ridge National Laboratory, TN (USA))

1990-12-01

97

High Performance Liquid Chromatography–Size Exclusion Chromatography for Rapid Analysis of Total Polar Compounds in Used Frying Oils  

Microsoft Academic Search

Analysis of used frying oil samples by high performance liquid chromatography–size exclusion chromatography (HPLC–SEC or HPSEC)\\u000a was compared to AOCS Official Method Cd 20-91 (silica gel column chromatography) for the purpose of developing a rapid analysis\\u000a of total polar compounds (TPC). In a direct comparison of the two analytical methods using four different sets of used frying\\u000a oils (21 total

J. D. CaldwellB; B. S. Cooke; M. K. Greer

98

Continuous analysis of helium in natural gas by chromatography  

Microsoft Academic Search

In extracting helium from natural gas at Bureau of Mines helium plants, a continuous analysis of the helium content of inlet and outlet gas streams is required to determine extraction efficiency. An analyzer, using established principles of gas chromatography to effect the analysis, has been developed to meet this need. It will record the helium content of inlet or discharge

C. L. Klingman; J. D. Marshall

1960-01-01

99

Polymer analysis by supercritical fluid chromatography.  

PubMed

Synthetic polymers always have distributions of the degrees of polymerization. Supercritical fluid chromatography (SFC) is almost only one technique to be able to separate pure polymer that has exactly unique degree of polymerization. For typical examples of SFC separation of polymers, four kinds of polymers: polystyrene, poly(ethylene glycol), some nonionic surfactants, and polyprenol are described about the conditions of SFC. Separated pure polymers which have no molecular weight distribution, are called uniform polymer. Uniform polymers are really useful to calibrate or validate various detectors. Here, the applications of calibrating ultraviolet detector, evaporative light scattering detector, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry are summarized. These detectors have strong molecular weight dependence of their sensitivity coefficient, in contrast to the good linearity of sample concentration. PMID:23465511

Takahashi, Kayori

2013-08-01

100

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

101

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

102

Gas-Liquid Flow in Pipelines  

SciTech Connect

A research program was carried out at the University of Illinois in which develops a scientific approach to gas-liquid flows that explains their macroscopic behavior in terms of small scale interactions. For simplicity, fully-developed flows in horizontal and near-horizontal pipes. The difficulty in dealing with these flows is that the phases can assume a variety of configurations. The specific goal was to develop a scientific understanding of transitions from one flow regime to another and a quantitative understanding of how the phases distribute for a give regime. These basic understandings are used to predict macroscopic quantities of interest, such as frictional pressure drop, liquid hold-up, entrainment in annular flow and frequency of slugging in slug flows. A number of scientific issues are addressed. Examples are the rate of atomization of a liquid film, the rate of deposition of drops, the behavior of particles in a turbulent field, the generation and growth of interfacial waves. The use of drag-reducing polymers that change macroscopic behavior by changing small scale interactions was explored.

Thomas J. Hanratty

2005-02-25

103

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

104

Gas-liquid chromatographic determination of 3-trifluoromethyl-4-nitrophenol residues in fish  

USGS Publications Warehouse

A procedure for the determination of 3-mftuormethyl-4-nitrophenol (TFM) in fish tissues is described. Homogenized tissues are extracted with hexane-ethyl ether; the extract is cleaned up by partitioning the TFM from the extracting solvent into O.IN NaOB, acidifying the aqueous solution, and partitioning again with hexaneethyl ether. The TFM is methylated with diazomethane and analyzed by gas-liquid chromatography, using electron capture detection. Recoveries ranged from 75 to 1000/., from fish muscles that were spiked with 0.01-2.00 JA#g TFM/g.

Allen, J. L.; Sills, J. B.

1974-01-01

105

Analysis and chromatographic purification of eicosanoids multiply labeled by tritium  

SciTech Connect

We show the possibility of analysis and chromatographic purification of eicosanoids triply labeled by tritium. The described methods allow us to isolate chromatographically pure products obtained by selective hydrogenatin, chemical, and enzyme methods, with radiochemical purity at least 95-97%. The following methods are used to analyze the reaction mixtures and to isolate the tritium-labeled eicosanoids: gas-liquid chromatography, high-efficiency liquid chromatography, and thin-layer chromatography on supports impregnated with silver nitrate.

Shevchenko, V.P.; Nagaev, I.Yu.; Myasoedov, N.F.

1989-01-01

106

Determination of microbial fatty acid profiles at femtomolar levels in human urine and the initial marine microfouling community by capillary gas chromatography-chemical ionization mass spectrometry with negative ion detection  

Microsoft Academic Search

Summary Room temperature esterification with the electron capturing pentafluorobenzyl bromide in glass capillaries, with analysis by capillary gas-liquid chromatography coupled with chemical ionization mass spectrometry and negative ion detection in the selected ion mode, allowed detection and identification of fatty acids from micro- bial biofilms at the femtomolar level. This sensitivity was achieved without loss of specificity of the mass

Goran Odham; Anders Tunlid; Gunilla Westerdahl; Lennart Larsson; James B. Guckert; David C. White

1985-01-01

107

Experimental investigation of gas–liquid distribution in monolith reactors  

Microsoft Academic Search

The present work investigates the influence of gas and liquid flow rates on inlet liquid distribution across monoliths operating in gas–liquid cocurrent downflow mode. Gas and liquid superficial velocities range from 0 to 68 and 1.4 to 8.5cm\\/s, respectively. Gas–liquid distribution was studied using a packed bed liquid distributor and a 12in pipe distributor for the aforementioned range of operating

Mayank Behl; Shantanu Roy

2007-01-01

108

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) [Latham, NY; Whitt, David Brandon (Albany, NY) [Albany, NY

2009-07-14

109

Study of interfacial behavior in concurrent gas-liquid flows  

Microsoft Academic Search

This research is focused on acquiring an understanding of the fundamental processes which occur within the liquid layer of separated (i.e., annular or stratified) gas-liquid flows. Knowledge of this behavior is essential for interpretation of pressure drops, entrainment fraction, transport processes and possibly flow regime transitions in gas-liquid flows. We are examining the qualitative and quantitative nature of the interface,

Mark J. McCready

1989-01-01

110

Analysis of acrylamide in different foodstuffs using liquid chromatography–tandem mass spectrometry and gas chromatography–tandem mass spectrometry  

Microsoft Academic Search

Acrylamide levels over a wide range of different food products were analysed using both liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) and gas chromatography–tandem mass spectrometry (GC–MS–MS). Two different sample preparation methods for HPLC–MS–MS analysis were developed and optimised with respect to a high sample throughput on the one hand, and a robust and reliable analysis of difficult matrices on the other

K. Hoenicke; R. Gatermann; W. Harder; L. Hartig

2004-01-01

111

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

112

Lipid analysis by quantitative thin-layer chromatography  

Microsoft Academic Search

Techniques for the quantitative analysis of lipids using thin-layer chromatography (TLC) are reviewed. The general procedures\\u000a are divided into two groups on the basis of whether or not the methods involve the recovery of substances from chromatoplates.\\u000a \\u000a Recovery methods are elaborated under detection of spots, recovery of substances and quantification. Methods are described\\u000a for the recovery of labile compounds from

O. S. Privett; M. L. Blank; D. W. Codding; E. C. Nickell

1965-01-01

113

RECENT APPLICATIONS OF HYDROPHILIC INTERACTION CHROMATOGRAPHY IN ENVIRONMENTAL ANALYSIS  

Microsoft Academic Search

Hydrophilic interaction chromatography (HILIC) has emerged as a viable option for many applications dealing with polar and hydrophilic analytes. The application of HILIC for the analysis of environmental samples has increased in the last years. Solid-phase extraction (SPE) coupled with HILIC-UV or MS (MS\\/MS) or ICP\\/MS has been utilized to pretreat, separate, and detect the residuals of numerous contaminants (pesticides,

Ruiping Li; Yali Guo; Qin Yuan

2011-01-01

114

Differences in Stability, Gas-Liquid Chromatographic Retention Times, and Esterification Rates for the Diastereoisomers of 2,3-Dimethylsuccinic Acid and Its Esters.  

National Technical Information Service (NTIS)

The report is concerned with the differences that are observed in certain properties of diastereoisomers of 2,3-dimethylsuccinic acid, and its esters, which arise from conformational factors. The analysis of the diastereoisomers was done using gas-liquid ...

P. J. Sniegoski

1970-01-01

115

Principles of Micellar Electrokinetic Capillary Chromatography Applied in Pharmaceutical Analysis  

PubMed Central

Since its introduction capillary electrophoresis has shown great potential in areas where electrophoretic techniques have rarely been used before, including here the analysis of pharmaceutical substances. The large majority of pharmaceutical substances are neutral from electrophoretic point of view, consequently separations by the classic capillary zone electrophoresis; where separation is based on the differences between the own electrophoretic mobilities of the analytes; are hard to achieve. Micellar electrokinetic capillary chromatography, a hybrid method that combines chromatographic and electrophoretic separation principles, extends the applicability of capillary electrophoretic methods to neutral analytes. In micellar electrokinetic capillary chromatography, surfactants are added to the buffer solution in concentration above their critical micellar concentrations, consequently micelles are formed; micelles that undergo electrophoretic migration like any other charged particle. The separation is based on the differential partitioning of an analyte between the two-phase system: the mobile aqueous phase and micellar pseudostationary phase. The present paper aims to summarize the basic aspects regarding separation principles and practical applications of micellar electrokinetic capillary chromatography, with particular attention to those relevant in pharmaceutical analysis.

Hancu, Gabriel; Simon, Brigitta; Rusu, Aura; Mircia, Eleonora; Gyeresi, Arpad

2013-01-01

116

Size-exclusion chromatography system for macromolecular interaction analysis  

DOEpatents

A low pressure, microcomputer controlled system employing high performance liquid chromatography (HPLC) allows for precise analysis of the interaction of two reversibly associating macromolecules such as proteins. Since a macromolecular complex migrates faster than its components during size-exclusion chromatography, the difference between the elution profile of a mixture of two macromolecules and the summation of the elution profiles of the two components provides a quantifiable indication of the degree of molecular interaction. This delta profile is used to qualitatively reveal the presence or absence of significant interaction or to rank the relative degree of interaction in comparing samples and, in combination with a computer simulation, is further used to quantify the magnitude of the interaction in an arrangement wherein a microcomputer is coupled to analytical instrumentation in a novel manner.

Stevens, Fred J. (Downers Grove, IL)

1988-01-01

117

Using Single Drop Microextraction for Headspace Analysis with Gas Chromatography  

NASA Astrophysics Data System (ADS)

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 for instructional use, especially to illustrate HS analysis or as an alternative to solid-phase microextraction (SPME) to which it is very similar. The basic principles and practice of HS-GC using SDME are described, including a complete review of the literature. Some possible experiments are suggested using water and N -methylpyrrolidone (NMP) as solvents.

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

2008-07-01

118

Comparison of reversed-phase liquid chromatography and hydrophilic interaction chromatography for the fingerprint analysis of Radix isatidis.  

PubMed

Radix isatidis is a famous anti-influenza virus herbal medicine traditionally taken as a water decoction. However, the chemical fingerprint analysis of Radix isatidis is dominantly based on RPLC, from which it is difficult to obtain fingerprint information of hydrophilic compounds. Here, we developed the separation of Radix isatidis by RPLC and hydrophilic interaction chromatography, comparing the traditional RPLC fingerprint with the hydrophilic interaction chromatography fingerprint. Besides, an anti-viral assay of Radix isatidis was conducted to evaluate its efficacy. The fingerprint-efficacy relationships between the fingerprints and the anti-viral activity were further investigated with principal component regression analysis. The results showed that the anti-viral activity correlated better with the hydrophilic interaction chromatography fingerprint than with the RPLC fingerprint. This study indicates that hydrophilic interaction chromatography could not only be a complementary method to increase the fingerprint coverage of conventional RPLC fingerprint, but also can better represent the efficacy and quality of Radix isatidis. PMID:24595986

Zhang, Cong-En; Xiong, Yin; Dong, Qin; Gao, Dan; Zhang, Le-Le; Ma, Li-Na; Peng, Cheng; Dong, Xiao-Ping; Yan, Dan

2014-05-01

119

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

120

Phase diagram and universality of the Lennard-Jones gas-liquid system  

NASA Astrophysics Data System (ADS)

The gas-liquid phase transition of the three-dimensional Lennard-Jones particles system is studied by molecular dynamics simulations. The gas and liquid densities in the coexisting state are determined with high accuracy. The critical point is determined by the block density analysis of the Binder parameter with the aid of the law of rectilinear diameter. From the critical behavior of the gas-liquid coexisting density, the critical exponent of the order parameter is estimated to be ? = 0.3285(7). Surface tension is estimated from interface broadening behavior due to capillary waves. From the critical behavior of the surface tension, the critical exponent of the correlation length is estimated to be ? = 0.63(4). The obtained values of ? and ? are consistent with those of the Ising universality class.

Watanabe, Hiroshi; Ito, Nobuyasu; Hu, Chin-Kun

2012-05-01

121

Phase diagram and universality of the Lennard-Jones gas-liquid system.  

PubMed

The gas-liquid phase transition of the three-dimensional Lennard-Jones particles system is studied by molecular dynamics simulations. The gas and liquid densities in the coexisting state are determined with high accuracy. The critical point is determined by the block density analysis of the Binder parameter with the aid of the law of rectilinear diameter. From the critical behavior of the gas-liquid coexisting density, the critical exponent of the order parameter is estimated to be ? = 0.3285(7). Surface tension is estimated from interface broadening behavior due to capillary waves. From the critical behavior of the surface tension, the critical exponent of the correlation length is estimated to be ? = 0.63(4). The obtained values of ? and ? are consistent with those of the Ising universality class. PMID:22667535

Watanabe, Hiroshi; Ito, Nobuyasu; Hu, Chin-Kun

2012-05-28

122

Injector design guidelines for gas/liquid propellant systems  

NASA Technical Reports Server (NTRS)

Injector design guidelines are provided for gas/liquid propellant systems. Information was obtained from a 30-month applied research program encompassing an analytical, design, and experimental effort to relate injector design parameters to simultaneous attainment of high performance and component (injector/thrust chamber) compatibility for gas/liquid space storable propellants. The gas/liquid propellant combination studied was FLOX (82.6% F2)/ ambient temperature gaseous methane. Design criteria that provide for simultaneous attainment of high performance and chamber compatibility are presented for both injector types. Parametric data are presented that are applicable for the design of circular coaxial and like-doublet injectors that operate with design parameters similar to those employed. However, caution should be exercised when applying these data to propellant combinations whose elements operate in ranges considerably different from those employed in this study.

Falk, A. Y.; Burick, R. J.

1973-01-01

123

Targeted analysis of glycomics liquid chromatography/mass spectrometry data  

PubMed Central

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 (RTs) 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 data sets. 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.

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

2012-01-01

124

Globin chain synthesis analysis by high performance liquid chromatography in the screening of thalassemia syndromes.  

PubMed

We applied reversed phase high performance liquid chromatography for globin chain synthesis analysis in screening for beta-thalassemia. The alpha/non-alpha-globin chain synthesis ratios have been determined in alpha-, beta-, and deltabeta-thalassemia carriers using the classical carboxymethyl cellulose chromatography as the reference method. Reversed phase high performance liquid chromatography is fast, accurate, and reproducible, and may be a suitable alternative for the traditional carboxymethyl cellulose chromatography. PMID:9859933

Galanello, R; Satta, S; Pirroni, M G; Travi, M; Maccioni, L

1998-01-01

125

Advances in silver ion chromatography for the analysis of fatty acids and triacylglycerols-2001 to 2011.  

PubMed

An effort is made to critically present the achievements in silver ion chromatography during the last decade. Novelties in columns, mobile-phase compositions and detectors are described. Recent applications of silver ion chromatography in the analysis of fatty acids and triacylglycerols are presented while stressing novel analytical strategies or new objects. The tendencies in the application of the method in complementary ways with reversed-phase chromatography, chiral chromatography and, especially, mass detection are outlined. PMID:22975910

Momchilova, Svetlana M; Nikolova-Damyanova, Boryana M

2012-01-01

126

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

127

Generation of Local Concentration Gradients by Gas-Liquid Contacting  

Microsoft Academic Search

We present a generic concept to create local concentration gradients, based on the absorption of gases or vapors in a liquid. A multilayer microfluidic device with crossing gas and liquid channels is fabricated by micromilling and used to generate multiple gas-liquid contacting regions, separated by a hydrophobic membrane. Each crossing can acts as both a microdosing and microstripping region. Furthermore,

Jong de Jorrit; Pascal W. Verheijden; Rob G. H. Lammertink; Matthias Wessling

2008-01-01

128

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

129

Prediction of gas-liquid two-phase flow regime in microgravity  

NASA Technical Reports Server (NTRS)

An attempt is made to predict gas-liquid two-phase flow regime in a pipe in a microgravity environment through scaling analysis based on dominant physical mechanisms. Simple inlet geometry is adopted in the analysis to see the effect of inlet configuration on flow regime transitions. Comparison of the prediction with the existing experimental data shows good agreement, though more work is required to better define some physical parameters. The analysis clarifies much of the physics involved in this problem and can be applied to other configurations.

Lee, Jinho; Platt, Jonathan A.

1993-01-01

130

Modified electrokinetic sample injection method in chromatography and electrophoresis analysis  

DOEpatents

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

131

Hydrodynamics and gas-liquid mass transfer in liquid-solid and gas-liquid-solid fluidized beds  

Microsoft Academic Search

An operating regime map is constructed based on the minimum fluidization and terminal velocities of solid particles in cocurrent upward gas-liquid-solid systems with liquid as the continuous phase. Common operating ranges for three phase fluidized bed systems and slurry bubble column systems are thus clearly defined. A mechanistic model is also developed to describe the terminal velocity of spherical particles

Jean

1988-01-01

132

Cellular fatty acid analysis as a potential tool for predicting mosquitocidal activity of Bacillus sphaericus strains.  

PubMed Central

Gas-liquid chromatography of fatty acid methyl esters and numerical analysis were carried out with 114 Bacillus sphaericus strains. Since only two clusters harbored mosquitocidal strains, this technique could be developed in screening programs to limit bioassays on mosquito larvae. It also allows differentiation of highly homologous strains.

Frachon, E; Hamon, S; Nicolas, L; de Barjac, H

1991-01-01

133

Glyceride analysis of palm oil after solvent fractionation  

Microsoft Academic Search

A procedure is described for determing the triglyceride composition of palm oil and its fractions by the use of silver nitrate\\u000a thin layer chromatography (TLC) and gas liquid chromatography (GLC). The triglycerides separated by silver nitrate TLC according\\u000a to the number of double bonds are quantified using infrared spectroscopy before further analysis by GLC according to carbon\\u000a number. The results

B. K. Tan; R. J. Hamilton; K. G. Berger

1981-01-01

134

US crude oil, natural gas, and natural gas liquids reserves  

SciTech Connect

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1989, and production volumes for the year 1989 for the total United States and for selected states and state sub-divisions. Estimates are presented for the following four categories of natural gas: total gas (wet after lease separation), its two major components (nonassociated and associated-dissolved gas), and total dry gas (wet gas adjusted for the removal of liquids at natural gas processing plants). In addition, two components of natural gas liquids, lease condensate and natural gas plant liquids, have their reserves and production reported separately. Also included is information on indicated additional crude oil reserves and crude oil, natural gas, and lease condensate reserves in nonproducing reservoirs. 28 refs., 9 figs., 15 tabs.

Not Available

1990-10-05

135

Modeling gas-liquid head performance of electrical submersible pumps  

Microsoft Academic Search

The objectives of this study are to develop a simple and accurate theoretical model and to implement the model into a computational tool to predict Electrical Submersible Pumps (ESP) head performance under two-phase flow conditions. A new two-phase model including a set of one-dimensional mass and momentum balance equations was developed. The derived gas-liquid momentum equations along pump channels has

Datong Sun

2003-01-01

136

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

137

Downward bubbly gas–liquid flow in a vertical pipe  

Microsoft Academic Search

Local characteristics of downward bubbly flow in a 42.3mm i.d. vertical pipe were investigated. An electrochemical technique was used to measure wall shear stress, local void fraction, liquid velocity, wall shear stress and velocity fluctuations. A gas–liquid mixer was used permitting the change in size of gas bubbles for the same gas and liquid flow rates. Special attention was paid

O. N. Kashinsky; V. V. Randin

1999-01-01

138

Gas-liquid bubbly flow in vertical pipes  

Microsoft Academic Search

Gas-liquid bubbly flow was investigated in vertical pipes for different flow conditions: fully developed turbulent downward flow in a 42.3 mm diameter pipe and upward flow in a 14.8 mm diameter pipe with liquid of elevated viscosity. Wall shear stress, local void fraction, and liquid velocity profiles, shear stress, and velocity fluctuations were measured using an electrodiffusional method. Results obtained

V. E. Nakoryakov; O. N. Kashinsky; V. V. Randin; L. S. Timkin

1996-01-01

139

Onset of pulsing in gas–liquid trickle bed filtration  

Microsoft Academic Search

When liquid suspensions containing low concentration of fine solids are treated in catalytic packed bed gas–liquid–solid reactors, which are operated in trickle flow or near the transition between trickle and pulse flow, plugging develops and increases the resistance to two-phase flow. Also due to obstruction, such accumulation of fines in the catalyst bed shifts progressively the flow pattern from trickling

I. Iliuta; F. Larachi

2004-01-01

140

Gas–liquid–solid flow modelling in a bubble column  

Microsoft Academic Search

An alternative approach to the modelling of solid–liquid and gas–liquid–solid flows for a 5:1 height to width aspect ratio bubble column is presented here. A modified transport equation for the volume fraction of a dispersed phase has been developed for the investigation of turbulent buoyancy driven flows (Chem. Eng. Proc., in press). In this study, a modified transport equation has

G. M. Cartland Glover; S. C. Generalis

2004-01-01

141

Gas-Liquid flow characterization in bubble columns with various gas-liquid using electrical resistance tomography  

Microsoft Academic Search

Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup

Haibo Jin; Han Yuhuan; Yang Suohe

2009-01-01

142

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 (-10 kV, 20 s) was introduced in this MEEKC system and this yielded about 25-fold sensitivity enhancement compared with hydrodynamic injection (1 psi, 10 s). During method validation, calibration curves were linear (r?0.99), within a range of 75-500 ng/mL for DBP and 150-1000 ng/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 453.67 ng/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

2013-12-15

143

Jojoba oil analysis by high pressure liquid chromatography and gas chromatography\\/mass spectrometry  

Microsoft Academic Search

Two analytical procedures for determining com-positions of jojoba liquid wax esters are described and compared. One, the more\\u000a tedious, involves separation of wax ester homologs by high pressure liquid chro-matography followed by determination of the\\u000a acid and alcohol moieties from each homolog. The second allows rapid determination of wax ester composition by gas Chromatographic\\u000a separation of hydrogenated jojoba wax esters

Gayland F. Spencer; Ronald D. Plattner; Thomas Miwa

1977-01-01

144

Multiresidue pesticide analysis by capillary gas chromatography-mass spectrometry.  

PubMed

A multiresidue pesticide method using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) procedure and capillary gas chromatography-mass spectrometry (GC-MS) is described for the determination of 166 organochlorine, organophosphorus, and pyrethroid pesticides, metabolites, and isomers in spinach. The pesticides from spinach were extracted using acetonitrile saturated with magnesium sulfate and sodium chloride, followed by solid-phase dispersive cleanup using primary-secondary amine and graphitized carbon black sorbents and toluene. Analysis is performed using different GC-MS techniques emphasizing the benefits of non-targeted acquisition and targeted screening procedures. Non-targeted data acquisition of pesticides in the spinach was demonstrated using GC coupled to a single quadrupole mass spectrometery (GC-MS) in full scan mode or multidimensional GC-time-of-flight mass spectrometery (GC ?× ?GC-TOF/MS), along with deconvolution software and libraries. Targeted screening was achieved using GC-single quadrupole mass spectrometry in selective ion monitoring (GC-MS/SIM) mode or -tandem mass spectrometry (GC-MS/MS) in multiple reaction monitoring mode. The development of these techniques demonstrates the powerful use of GC-MS for the screening, identification, and quantitation of pesticide residues in foods. PMID:21643907

Wong, Jon W; Zhang, Kai; Hayward, Douglas G; Kai-Meng, Chin

2011-01-01

145

Chromatography Theory  

NSDL National Science Digital Library

James Hardy has produced a number of presentation-style lecture modules for analytical chemistry. This is a very good module that covers the introductory theory of chromatography. The material includes information on chromatography along with plate and kinetic theories. It is a colorful and well planned presentation of the introduction to chromatography that could be used as the basis for lectures on chromatography at the introductory analytical chemistry or instrumental analysis level.

2011-04-13

146

Comparison of microemulsion electrokinetic chromatography and micellar electrokinetic chromatography methods for the analysis of phenolic compounds.  

PubMed

In this study, microemulsion electrokinetic chromatography (MEEKC) and micellar electrokinetic chromatography (MEKC) were compared for their abilities to separate and detect thirteen phenolic compounds (syringic acid, p-coumaric acid, vanillic acid, caffeic acid, gallic acid, 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, (-)-epicatechin, and (-)-gallocatechin), and two other ingredients (caffeine and theophylline) in teas and grapes. Separation of phenolic compounds was improved by changing the SDS concentration for MEEKC, but the SDS concentration rarely affected the resolution for MEKC. Organic modifier (acetonitrile or methanol) was found to markedly influence the resolution and selectivity for both MEEKC and MEKC systems. In addition, a higher voltage and a higher column temperature improved the separation efficiency without any noticeable reduction in resolution for MEEKC whereas they caused a poor resolution for the MEKC system. Although separations with baseline resolution were achieved by the optimized MEEKC and MEKC methods, the separation selectivity resulting from the proposed MEEKC method was completely different from that of MEKC. PMID:16013824

Huang, Hsi-Ya; Lien, Wei-Chih; Chiu, Chen-Wen

2005-06-01

147

Effects of inlet blockage of gas-liquid scheme injector on acoustic tuning for acoustic damping in a combustion chamber  

Microsoft Academic Search

In a rocket combustor, purely acoustic tuning of gas-liquid scheme injector is studied numerically for acoustic absorption\\u000a by adopting linear acoustic analysis. Acoustic behavior in the combustor with a single injector is investigated to assure\\u000a the optimum injector length. Acoustic-absorption effect of the injector is evaluated for cold condition by the quantitative\\u000a parameter of damping factor as a function of

Chae Hoon Sohn; I.-Sun Park

2008-01-01

148

Hydrodynamics and gas-liquid mass transfer in liquid-solid and gas-liquid-solid fluidized beds  

SciTech Connect

An operating regime map is constructed based on the minimum fluidization and terminal velocities of solid particles in cocurrent upward gas-liquid-solid systems with liquid as the continuous phase. Common operating ranges for three phase fluidized bed systems and slurry bubble column systems are thus clearly defined. A mechanistic model is also developed to describe the terminal velocity of spherical particles in gas-liquid mediums. The model parameter, the bubble-wake and particle interaction coefficient, is shown to be a function of particle properties only. In the second topic of this work, a fluid-mechanic is proposed to account for the bed voidage-liquid velocity or sedimentation velocity relationship for both liquid-solid fluidization and sedimentation under low Reynolds number conditions. The model is established based on the cell model concept with consideration of drag reduction due to particle alignment and nonuniformity of the local flow field due to distributor effects. It is shown that the model can explain the experimental discrepancy of the bed expansion and sedimentation data reported in the literature. Regarding the final topic of this work, theoretical models for the rising velocity and gas-liquid mass transfer coefficient of a single bubble in liquids and liquid-solid mediums are presented. The model for the bubble rising velocity is based on a force balance on a single bubble taking into account the impaction force due to solid particles. The mass transfer model, on the other hand, considers two different mechanisms, i.e., transfer through both the bubble roof and the bubble base.

Jean, R.H.

1988-01-01

149

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...

150

APPLICATION OF CAPILLARY SUPERCRITICAL FLUID CHROMATOGRAPHY TO THE ANALYSIS OF A MIDDLE DISTILLATE FUEL  

EPA Science Inventory

The paper describes the application of capillary supercritical fluid chromatography (SFC) to the analysis of a middle distillate fuel. Small diameter (50 micrometer i.d.) fused silica capillary columns coated with crosslinked 50% phenyl polymethylsiloxane provided high separation...

151

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...

152

QUANTITATIVE ANALYSIS OF 68 POLAR COMPOUNDS FROM TEN CHEMICAL CLASSES BY DIRECT AQUEOUS INJECTION GAS CHROMATOGRAPHY  

EPA Science Inventory

Porous polymer packings have been used successfully in many applications of direct aqueous injection gas chromatography. The authors have expanded the use of aqueous injection to the quantitative analysis of 68 alcohols, acetates, ketones, ethers, sulfides, aldehydes, diols, dion...

153

Micromixing of miscible liquids in segmented gas-liquid flow.  

PubMed

We present an integrated microfluidic system that achieves efficient mixing between two miscible liquid streams by introducing a gas phase, forming a segmented gas-liquid (slug) flow, and completely separating the mixed liquid and gas streams in a planar capillary separator. The recirculation motion associated with segmented flow enhances advection in straight microchannels without requiring additional fabrication steps. Instantaneous velocity fields are quantified by microscopic particle image velocimetry (muPIV). Velocities in the direction normal to the channel amount to approximately 30% of the bulk liquid velocity inside a liquid segment. This value depends only weakly on the length of a liquid segment. Spatial concentration fields and the extent of mixing (EOM) are obtained from pulsed-laser fluorescence microscopy and confocal scanning microscopy measurements. The mixing length is reduced 2-3-fold in comparison with previously reported chaotic micromixers that use three-dimensional microchannel networks or patterned walls. Segmented gas-liquid microflows allow mixing times to be varied over several orders of magnitude between milliseconds and second time scales. PMID:15697306

Günther, Axel; Jhunjhunwala, Manish; Thalmann, Martina; Schmidt, Martin A; Jensen, Klavs F

2005-02-15

154

New gas-liquid equilibration method: syringe tonometer.  

PubMed

This new apparatus for gas-liquid equilibration (tonometry) in a transportable vessel is designed for tonometry of blood or buffer solution in a specially designed syringe. Gas enters the syringe chamber through small holes in the tip of the syringe plunger and bubbles upward through the sample. The syringe plunger is a second chamber, which is used for warming and humidifying the gas before it enters the tonometer chamber. The entire syringe is housed in a transparent, temperature-controlled environment during equilibration. After equilibration, the sample is easily entered into a blood-gas analyzer. At most, gas-liquid O2/CO2 equilibration for 2.5 mL of buffer or blood requires less than 13 min. Comparisons with a standard thin-film tonometer show good agreement for pO2 and pCO2 over the range 0-93 kPa (0-700 mmHg) and 2-20 kPa (14-150 mmHg), respectively. The syringe tonometer eliminates contamination of the sample during transfer and transport to the analyzer, thus making tonometry more technique-independent. The apparatus is simple and easy to use, with definite advantages over existing methods of tonometry. PMID:6784964

Wallace, W D; Cutler, C A; Clark, J S

1981-05-01

155

Studies of higher alcohol formation by yeasts through gas chromatography  

Microsoft Academic Search

Summary The methods of gas chromatography have made possible significant advances in understanding the pathways of formation of higher alcohols during alcoholic fermentation. The higher alcohols in wines of fermented media were quantitatively concentrated by close fractional distillation coupled with drying and extraction with diethyl ether. Gas-liquid chromatography was employed for determining the percentage of the individual alcohol components as

J. F. Guymon

1964-01-01

156

Micellar liquid chromatography: suitable technique for screening analysis  

Microsoft Academic Search

The screening capability of micellar liquid chromatography (MLC) is discussed using the reported chromatographic data of several sets of compounds (amino acids, ?-blockers, diuretics, phenethylamines, phenols, polynuclear aromatic hydrocarbons, steroids and sulfonamides) and new results (sulfonamides and steroids). The chromatographic data are treated with an interpretive optimisation resolution procedure to obtain the best separation conditions. Usually, the pH and the

M. J Ruiz-Angel; R. D Caballero; E. F Simó-Alfonso; M. C Garc??a-Alvarez-Coque

2002-01-01

157

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...

158

Water extraction of plant tissues for analysis by ion chromatography  

Microsoft Academic Search

High pressure liquid chromatography (HPLC)?grade water was evaluated as an alternative extraction reagent to acid extraction of plant tissue. Green and red bell pepper fruit (Capsium annuum var. annuum L.), cultivar Pip; sweet corn internodes (Zea mays L.), cultivar Florida Staysweet; cabbage wrapper leaves (Brassica oleracea L. Capitata group), cultivar Solid Blue 770; peach leaves [Prunus persica (L.) Batsch], cultivar

V. M. Russo; S. V. Karmarkar

1998-01-01

159

Gas-liquid bubbly flow in vertical pipes  

SciTech Connect

Gas-liquid bubbly flow was investigated in vertical pipes for different flow conditions: fully developed turbulent downward flow in a 42.3 mm diameter pipe and upward flow in a 14.8 mm diameter pipe with liquid of elevated viscosity. Wall shear stress, local void fraction, and liquid velocity profiles, shear stress, and velocity fluctuations were measured using an electrodiffusional method. Results obtained demonstrate the existence of universal near-wall velocity distribution in a downward bubbly flow. The reduction of turbulent fluctuations is observed in downward flow as compared to a single-phase turbulent flow. The development of bubble-induced liquid velocity fluctuations in a laminar bubbly flow was studied.

Nakoryakov, V.E.; Kashinsky, O.N.; Randin, V.V.; Timkin, L.S. [Russian Academy of Sciences, Novosibirsk (Russian Federation). Inst. of Thermophysics

1996-06-01

160

Gas-liquid chromatographic determination of isosorbide dinitrate in tablets.  

PubMed

A gas-liquid chromatographic (GLC) method is described for determining isosorbide dinitrate (ISDN) in tablets. ISDN is extracted from tablet excipients by a 2-phase system composed of water-ethyl ether, and detected and quantitated with a flame ionization detector after separation from the internal standard (glyceryl tributyrate) on a 3% OV-210 column. Ten replicate assays on 2 different batches of tablets, each containing 5 mg ISDN, gave coefficients of variation of 1.16 and 1.48%, respectively. Comparison of results obtained for tablets containing 5, 10, and 40 mg ISDN, and for diluted isosorbide dinitrate raw material containing 25% ISDN, showed good correlation among the GLC, USP colorimetric, and USP polarographic procedures. Assay of synthetic mixtures containing ISDN, isosorbide-2-mononitrate, and isosorbide-5-mononitrate demonstrated that the GLC procedure is specific for ISDN, whereas the USP polarographic procedure is subject to interference from the mononitrates. PMID:924938

Prue, D G; Johnson, R N; Kho, B T

1977-11-01

161

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

162

Modeling gas-liquid head performance of electrical submersible pumps  

NASA Astrophysics Data System (ADS)

The objectives of this study are to develop a simple and accurate theoretical model and to implement the model into a computational tool to predict Electrical Submersible Pumps (ESP) head performance under two-phase flow conditions. A new two-phase model including a set of one-dimensional mass and momentum balance equations was developed. The derived gas-liquid momentum equations along pump channels has improved Sachdeva (1992, 1994)'s model in petroleum industry and generalized Minemura (1998)'s model in nuclear industry. The resulting pressure ODE for frictionless incompressible single-phase flow is consistent with the pump Euler equation. In the two-phase momentum equations, new models for wall frictional losses for each phase, through using gas-liquid stratified assumption and existing correlations for impeller rotating effect, channel curvature effect, and channel cross section effect, have been proposed. New equations for radius of curvature along ESP channels, used in the curvature effect calculation, have been derived. A new shock loss model incorporating rotational speeds has been developed. A new correlation for drag coefficient and interfacial characteristic length effects has been obtained through fitting the model results with experimental data. An algorithm to solve the model equations has been developed and implemented. The model predicts pressure and void fraction distributions along impellers and diffusers and can also be used to predict the pump head performance curve under different fluid properties, pump intake conditions, and rotational speeds. The new two-phase model is validated with air-water experimental data. Results show the model provides a very good prediction for pump head performance under different gas flow rates, liquid flow rates, and different intake pressures. The new model is capable of predicting surging and gas lock conditions.

Sun, Datong

163

The application of a non-thermal plasma generated by gas-liquid gliding arc discharge in sterilization  

NASA Astrophysics Data System (ADS)

Gliding arc discharge has been investigated in recent years as an innovative physicochemical technique for contaminated water treatment at atmospheric pressure and ambient temperature. In this study we tested a gas-liquid gliding arc discharge reactor, the bacterial suspension of which was treated circularly. When the bacterial suspension was passed through the electrodes and circulated at defined flow rates, almost 100% of the bacteria were killed in less than 3.0 min. Experimental results showed that it is possible to achieve an abatement of 7.0 decimal logarithm units within only 30 s. Circulation flow rates and types of feeding gas caused a certain impact on bacteria inactivation, but the influences are not obvious. So, under the promise of sterilization effect, industrial applications can select their appropriate operating conditions. All inactivation curves presented the same three-phase profile showing an apparent sterilization effect. Analysis of the scanning electron microscope images of bacterial cells supports the speculation that the gas-liquid gliding arc discharge plasma is acting under various mechanisms driven essentially by oxidation and the effect of electric field. These results enhance the possibility of applying gas-liquid gliding arc discharge decontamination systems to disinfect bacterial-contaminated water. Furthermore, correlational research indicates the potential applications of this technology in rapid sterilization of medical devices, spacecraft and food.

Du, Chang Ming; Wang, Jing; Zhang, Lu; Xia Li, Hong; Liu, Hui; Xiong, Ya

2012-01-01

164

Simplified and improved methylation analysis of saccharides, using a modified procedure and thin-layer chromatography  

Microsoft Academic Search

Methylation analysis used in determining the positions of glycosidic linkages in oligo- and poly-saccharides has been greatly simplified by eliminating two of the usual reactions, reduction and acetylation of the methylated monosaccharide residues. The saccharides are methylated by the Hakomori procedure, followed by acid hydrolysis and analysis by thin-layer chromatography (TLC). The procedure is illustrated by analysis of four known

Rupendra Mukerjea; Doman Kim; John F. Robyt

1996-01-01

165

A COMPARATIVE STUDY CONCERNING THE IMAGE ANALYSIS IN THIN LAYER CHROMATOGRAPHY OF FLUORESCENT COMPOUNDS  

Microsoft Academic Search

The use of image analysis software for the detection and quantitative evaluation of fluorescent compounds in thin layer chromatography is investigated. Four different image analysis software packages (Sorbfil TLC, Biodit, JustTLC, and Melanie) were applied and compared. The image analysis methods were developed and validated for the simultaneous determination of quercetin and kaempferol in food supplements. The chromatographic separation used

Lucian Alexandru Fazaka?; Rodica Domnica Na?cu-Briciu; Costel Sârbu

2011-01-01

166

Analysis of amprolium by hydrophilic interaction liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

We present a fast liquid chromatography–tandem mass spectrometry (LC–MS\\/MS) method for the analysis of the coccidiostat amprolium in food samples. Tandem mass spectrometry in a triple quadrupole was used for quantitative purposes, and the information from multiple-stage mass spectrometry in an ion-trap mass analyzer contributed to fragmentation studies. Hydrophilic interaction liquid chromatography (HILIC) in a Fused-Core™ column using isocratic elution

Anna Martínez-Villalba; Encarnación Moyano; M. Teresa Galceran

2010-01-01

167

Analysis of thiopurines using aqueous normal phase chromatography.  

PubMed

The chromatography of several thiopurines is investigated using aqueous normal phase (ANP) conditions in conjunction with a silica hydride-based column. Both isocratic and gradient elution modes are tested. Detection of higher concentration samples is done by UV to demonstrate feasibility in this format while lower concentration samples utilize mass spectrometry (MS). Repeatability of successive runs is also tested with particular attention to gradient methods where the equilibration time of the stationary phase can be evaluated. PMID:24657678

Pesek, Joseph J; Matyska, Maria T; Young, Joshua E

2014-07-01

168

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

169

Gas-Liquid Precipitation of Water Dissolved Heavy Metal Ions Using Hydrogen Sulfide Gas  

Microsoft Academic Search

Precipitation of solids promoted by gas-liquid reactions is applied in many industrial processes such as the production of ammonium phosphate, ammonium sulphate, barium carbonate, calcium carbonate, calcium fluoride, ypsum (calcium sulphate), goethite, sodium bicarbonate, strontium carbonate and terephthalic acid. In ddition gas-liquid precipitation can be applied in gas cleaning, heavy metal removal and in biotechnology. Despite the importance of this

Mousa Al-Tarazi

2004-01-01

170

Crude oil and natural gas pricing. Chapters 300 to 499: natural gas liquids, natural gas  

Microsoft Academic Search

This text analyzes the federal statutes and regulations that affect the pricing and allocation of crude oil, natural gas, and natural gas liquids. It does not cover refined products or imported crude oil except where necessary to place major decisions in historical context. Chapter 300 concerns natural gas liquids. For historical rather than logical reasons, these are regulated as an

1980-01-01

171

On The Validity of the Assumed PDF Method for Modeling Binary Mixing/Reaction of Evaporated Vapor in GAS/Liquid-Droplet Turbulent Shear Flow  

NASA Technical Reports Server (NTRS)

An Investigation of the statistical description of binary mixing and/or reaction between a carrier gas and an evaporated vapor species in two-phase gas-liquid turbulent flows is perfomed through both theroetical analysis and comparisons with results from direct numerical simulations (DNS) of a two-phase mixing layer.

Miller, R. S.; Bellan, J.

1997-01-01

172

Analysis of Developing Gas\\/liquid Two-Phase Flows  

Microsoft Academic Search

The goal of this work is to develop a mechanistically based CFD model that can be used to simulate process equipment operating in the churn-turbulent regime. The simulations were performed using a state-of-the-art computational multiphase fluid dynamics code, NPHASECMFD [Antal et al,2000]. A complete four-field model, including the continuous liquid field and three dispersed gas fields representing bubbles of different

Elena A. Tselishcheva; Michael Z. Podowski; Steven P. Antal; Donna Post Guillen; Matthias Beyer; Dirk Lucas

2010-01-01

173

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

PubMed Central

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 CO2 from a liquid perfluoropolyether (PFPE) surface in vacuum [incident energy Einc = 10.6(8) kcal/mol, incident angle ?inc = 60°] to specifically reveal rotational angular-momentum directions for scattered molecules. Experimentally, internal quantum state populations and MJ 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 CO2 + fluorinated self-assembled monolayers have been used to model CO2 + PFPE dynamics. Experimental results and molecular dynamics simulations reveal highly oriented CO2 distributions that preferentially scatter with “top spin” as a strongly increasing function of J state.

Perkins, Bradford G.; Nesbitt, David J.

2008-01-01

174

Classification of natural resins by liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry using chemometric analysis.  

PubMed

Twenty-six resins from six botanical sources belonging to the class Magnoliopsida were compared based on gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry data. The extracts were analysed by GC after silylation and by reversed phase LC combined with atmospheric pressure photoionisation (APPI) mass spectrometry. The chromatograms were re-organized in data matrices, where each sample was represented by a single column comprising 2755 observations (intensity, time, m/z) in GC-MS and 360 observations in LC-MS. A simple comparison of resin fingerprints was attempted by organizing data according to a three dimensional bubble chart (retention time against m/z where each point was a bubble which size represented the ion intensity) where it is possible to easily superimpose the fingerprints. Thus the common and different species can be easily observed enabling to classify the resins. Hierarchical cluster analysis based on characteristics of GC-MS and LC-MS profiles affords a complete description of the classes of the resins and shows that 26 resins are divided into five main clusters Commiphora mukul, Daniella oliveri, Gardenia gummifera, Canarium madagascariensis, Boswellia dalzielii and Boswellia serrata, respectively. In conclusion, the proposed method has been applied to three other resinous samples from the Burseraceae family to evaluate their alteration state. PMID:22885042

Rhourrhi-Frih, B; West, C; Pasquier, L; André, P; Chaimbault, P; Lafosse, M

2012-09-21

175

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

176

Analysis of fire ant pesticides in water by solid-phase microextraction and gas chromatography\\/mass spectrometry or high-performance liquid chromatography\\/mass spectrometry  

Microsoft Academic Search

The analysis of four widely used fire ant pesticides (chlorpyrifos, fenoxycarb, avermectin, and hydramethylnon) in water was accomplished by combining solid-phase microextraction (SPME) with either gas chromatography\\/quadruple ion trap mass spectrometry (GC\\/MS) or high-performance liquid chromatography\\/quadruple ion trap MS (HPLC\\/MS). Solid-phase microextraction is a fast, selective, and solvent-free extraction technique that accomplishes both extraction and pre-concentration events in a single

Michelle L Reyzer; Jennifer S Brodbelt

2001-01-01

177

On-line coupled high performance liquid chromatography-gas chromatography for the analysis of contamination by mineral oil. Part 1: method of analysis.  

PubMed

For the analysis of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH), on-line coupled high performance liquid chromatography-gas chromatography-flame ionization detection (HPLC-GC-FID) offers important advantages: it separates MOSH and MOAH in robust manner, enables direct injection of large aliquots of raw extracts (resulting in a low detection limit), avoids contamination of the sample during preparation and is fully automated. This review starts with an overview of the technology, particularly the fundamentals of introducing large volumes of solvent into GC, and their implementation into various transfer techniques. The main part deals with the concepts of MOSH and MOAH analysis, with a thorough discussion of the choices made. It is followed by a description of the method. Finally auxiliary tools are summarized to remove interfering components, enrich the sample in case of a high fat content and obtain additional information about the MOSH and MOAH composition. PMID:22770383

Biedermann, Maurus; Grob, Koni

2012-09-14

178

Dynamic Modeling Strategy for Flow Regime Transition in Gas-Liquid Two-Phase Flows  

SciTech Connect

In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As twophase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present work aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation of the interfacial area, fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminator s are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.

Xia Wang; Xiaodong Sun; Benjamin Doup; Haihua Zhao

2012-12-01

179

Analysis of anions in hydrofluoro ethers by ion chromatography.  

PubMed

Hydrofluoro ethers (HFES) are considered to be an ideal cleaning solvent in applications like vapor degreasing and wet cleaning. It is also a good solvent replacement for CFCs (chlorofluorocarbons), HCFCs (hydrochlorofluorocarbons), HFCs (hydrofluorocarbons) and chlorinated solvents because they have a short atmospheric lifetime and low global warming potential. Based upon their properties, hydrofluoro ethers are ideally suited for the demands of the electronics industry. However, the electronics industry requires these solvents to have high purity, especially in the area of residual anions. This paper will present information on an extraction methodology for the transfer of anions from the hydrofluoro ether to water. Then, an analytical method utilizing ion chromatography that is capable of detection of 10 anions (fluoride, acetate, formate, chloride, nitrite, bromide, nitrate, sulfate, oxalate, and phosphate) in the part per billion level will be demonstrated. PMID:15250412

Hulteen, John C; Schaible, Sandi M

2004-06-11

180

Evaluation of generic chiral liquid chromatography screens for pharmaceutical analysis.  

PubMed

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% of the test compounds. The second screen employed three macrocyclic glycopeptide columns with two mobile phases and showed enantioselectivity for 65% of the test compounds. Merging of the two screening procedures resulted in an enantioselectivity for 96% of the chiral compounds. It is anticipated that the systematic use of the automated chiral HPLC screens described in this report will substantially reduce the necessary time for method development of pharmaceutically related chiral analytical methods. PMID:12924784

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

2003-07-11

181

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

182

Gas-Liquid Supersonic Cleaning and Cleaning Verification Spray System  

NASA Technical Reports Server (NTRS)

NASA Kennedy Space Center (KSC) recently entered into a nonexclusive license agreement with Applied Cryogenic Solutions (ACS), Inc. (Galveston, TX) to commercialize its Gas-Liquid Supersonic Cleaning and Cleaning Verification Spray System technology. This technology, developed by KSC, is a critical component of processes being developed and commercialized by ACS to replace current mechanical and chemical cleaning and descaling methods used by numerous industries. Pilot trials on heat exchanger tubing components have shown that the ACS technology provides for: Superior cleaning in a much shorter period of time. Lower energy and labor requirements for cleaning and de-scaling uper.ninih. Significant reductions in waste volumes by not using water, acidic or basic solutions, organic solvents, or nonvolatile solid abrasives as components in the cleaning process. Improved energy efficiency in post-cleaning heat exchanger operations. The ACS process consists of a spray head containing supersonic converging/diverging nozzles, a source of liquid gas; a novel, proprietary pumping system that permits pumping liquid nitrogen, liquid air, or supercritical carbon dioxide to pressures in the range of 20,000 to 60,000 psi; and various hoses, fittings, valves, and gauges. The size and number of nozzles can be varied so the system can be built in configurations ranging from small hand-held spray heads to large multinozzle cleaners. The system also can be used to verify if a part has been adequately cleaned.

Parrish, Lewis M.

2009-01-01

183

Study of interfacial behavior in cocurrent gas-liquid flows  

NASA Astrophysics Data System (ADS)

The machanism was examined of formation of solitary waves on gas-liquid flows and found, that these form from existing periodic waves which have sufficiently large (approx. 1.5 to 2 depending upon fluid properties) amplitude to liquid layer thickness ratios. The exact process for the wave shape change is not understood but it does not seem to be related to the wave steepness (amplitude/wavelength) or to separation of gas flow over the waves. The observed confinement of solitary waves to low liquid Reynolds numbers results because the necessary large precursor waves do not form if the wave speed dispersion is too large or if the wavelength of the dominant waves is too short, as occurs for higher Re(sub L). Measurements of interface tracings and calculations of power spectra and bispectra as a function of flow distance for conditions close to neutral stability reveal that the initially, linearly unstable mode is stabilized by formation of overtones which are linearly stable and can dissipate energy. As a result, a stable wave field can occur. Mode equations, which include quadratic nonlinearities, can model this process to the extent of producing some degree of quantitative predictions for the amplitudes of the wave modes. However, a complete picture of the wave field must include sidebands as well because these are observed for some flow conditions.

McCready, Mark J.

1990-01-01

184

Gas-Liquid flow characterization in bubble columns with various gas-liquid using electrical resistance tomography  

NASA Astrophysics Data System (ADS)

Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup and mean holdups are investigated in a 0.160 m i. d. bubble column using ERT with two axial locations (Plane 1 and Plane 2). In all the experiments, air was used as the gas phase, tap water as liquid phase, and a series of experiments were done by adding KCl, ethanol, oil sodium, and glycerol to change liquid conductivity, liquid surface tension and viscosity. The superficial gas velocity was varied from 0.02 to 0.2 m/s. The effect of conductivity, surface tension, viscosity on the mean holdups and radial gas holdup distribution is discussed. The results showed that the gas holdup decrease with the increase of surface tension and increase with the increase of viscosity. Meanwhile, the settings of initial liquid conductivity slightly influence the gas holdup values, and the experimental data increases with the increase of the initial setting values in the same conditions.

Jin, Haibo; Yuhuan, Han; Suohe, Yang

2009-02-01

185

Gas liquid chromatography of the hydroxy-, acetoxy-and oxo-stearic acid methyl esters  

Microsoft Academic Search

Carbon numbers have been determined for all the 17 isomeric methyl hydroxy- and acetoxystearates and for 15 of the 16 isomeric\\u000a methyl oxostearates using silicone SE-30, silicone QF-1, and ethylene glycol succinate (EGS) as liquid phases. The carbon\\u000a numbers of the isomers increase with increasing distance of the point of substitution from the carboxyl end of the fatty acid\\u000a chain

A. P. Tulloch

1964-01-01

186

Quantitative Aging Pattern in Mouse Urine Vapor as Measured by Gas-Liquid Chromatography  

NASA Technical Reports Server (NTRS)

We have discovered a quantitative aging pattern in mouse urine vapor. The diagnostic power of the pattern has been found to be high. We hope that this pattern will eventually allow quantitative estimates of physiological age and some insight into the biochemistry of aging.

Robinson, Arthur B.; Dirren, Henri; Sheets, Alan; Miquel, Jaime; Lundgren, Paul R.

1975-01-01

187

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

188

Ionic liquids as silica deactivating agents in gas chromatography for direct analysis of primary amines in water  

Microsoft Academic Search

Analysis of primary amines in aqueous samples remains a challenging analytical issue. The preferred approach by gas chromatography is hampered by interactions of free silanol groups with the highly reactive amine groups, resulting in inconsistent measurements. Here, we report a method for direct analysis of aliphatic amines and diamines in aqueous samples by gas chromatography (GC) with silanol deactivation using

Agnieszka Krzy?aniak; Wilko Weggemans; Boelo Schuur; André B. de Haan

189

ANALYSIS OF CHLORINATED HERBICIDES BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY  

EPA Science Inventory

A method that uses high performance liquid chromatography/mass spectrometry (HPLC/MS) for the analysis of chlorinated phenoxyacid herbicides is described. uring method development different techniques were used to increase both the sensitivity and the specificity of thermospray H...

190

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...

191

APPLICATION OF HIGH PERFORMANCE LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY TO ENVIRONMENTAL ANALYSIS  

EPA Science Inventory

High performance liquid chromatography (HPLC) coupled with nass spectronetry (MS) is described for the analysis of samples for environmental pollutants. uring the course of this work different techniques were used to increase both the sensitivity and specificity of HPLC/MS. hese ...

192

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 ...

193

NEW TRENDS IN FAST LIQUID CHROMATOGRAPHY FOR FOOD AND ENVIRONMENTAL ANALYSIS  

Microsoft Academic Search

There is an increasing need for applications in food and environmental areas able to cope with a large number of analytes in very complex matrices. The new analytical procedures demand sensitivity, robustness and high resolution within an acceptable analysis time. The purpose of this review is to describe new trends based on fast liquid chromatography applied to the food and

Oscar Núñez; Héctor Gallart-Ayala; Claudia P. B. Martins; Paolo Lucci

194

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

195

ANALYSIS OF FERRIC AND FERROUS IONS IN SOIL EXTRACTS BY ION CHROMATOGRAPHY  

EPA Science Inventory

A method using ion chromatography (IC) for the analysis of ferrous (Fe 2+) and ferric (Fe 3+) ions in soil extracts has been developed. This method uses an ion exchange column with detection at 520 nm after post-column derivatization. Selectivity is achieved by using an anionic...

196

Characterization of fatty acids and triacylglycerols in vegetable oils by gas chromatography and statistical analysis  

Microsoft Academic Search

Fatty acids and triacylglycerols from Argania tree seeds (argania oil) were identified. Common fatty acids and triacylglycerols were quantified using gas chromatography on a capillary column. A frequent adulteration of some kinds of argania oil was determined using statistical methods. Hierarchical cluster analysis clearly distinguished between oil directly isolated from seeds and bought in a pharmacy, and oil bought in

Tomáš ?ezanka; Hana ?ezanková

1999-01-01

197

New trends in fast liquid chromatography for food and environmental analysis.  

PubMed

There is an increasing need for applications in food and environmental areas able to cope with a large number of analytes in very complex matrices. The new analytical procedures demand sensitivity, robustness and high resolution within an acceptable analysis time. The purpose of this review is to describe new trends based on fast liquid chromatography applied to the food and environmental analysis. It includes different column technologies, such as monolithic, sub-2 ?m, porous shell, as well as different stationary phases such as reversed phase (C8 and C18), hydrophilic interaction liquid chromatography (HILIC) and fluorinated columns. Additionally, recent sample extraction and clean-up methodologies applied to reduce sample manipulation and total analysis time in food and environmental analysis--QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe), on line solid phase extraction coupled to ultrahigh pressure liquid chromatography (on line SPE-UHPLC), turbulent flow chromatography (TFC) and molecularly imprinted polymers (MIPs), were also addressed. The advantages and drawbacks of these methodologies applied to the fast and sensitive analyses of food and environmental samples are going to be discussed. PMID:22153282

Núñez, Oscar; Gallart-Ayala, Héctor; Martins, Claudia P B; Lucci, Paolo

2012-03-01

198

Solidphase microextraction coupled to gas chromatography: A new method for the analysis of organics in water  

Microsoft Academic Search

Methods developed for the analysis of organic compounds from aqueous samples by solid-phase microextraction (SPME) coupled to gas chromatography (GC) are reviewed with special emphasis on the determination and monitoring in environmental samples contaminated by organic micropollutants, i.e., benzene, toluene, ethylbenzene and xylene isomers (BTEX), pesticides, phenols and polycyclic aromatic hydrocarbons (PAH).

Ralf Eisert; Karsten Levsen

1996-01-01

199

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

200

Analysis of Pendimethalin Residues in Fruit, Nuts, Vegetables, Grass, and Mint by Gas Chromatography  

Microsoft Academic Search

Pendimethalin (N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine), in the formulation of Prowl (a commercial herbicide), was applied to various crops. Analysis of pendimethalin and its metabolite (4(1-ethylpropyl)amino-2-methyl-3,5-dinitrobenzyl alcohol) was accomplished by utilizing liquid- liquid partitioning, gel permeation chromatography (GPC) for nuts and mint, solid-phase extraction (SPE) cleanup, and gas chromatography (GC) with a nitrogen-phosphorus detector (NPD). Method validation recoveries for fruits, nuts, vegetables, grass, and

J. Engebretson; G. Hall; M. Hengel; T. Shibamoto

2001-01-01

201

Immunoaffinity chromatography for the sample pretreatment of Taxus plant and cell extracts prior to analysis of taxanes by high-performance liquid chromatography.  

PubMed

The application of immunoaffinity chromatography for the purification of Taxus plant and cell extracts prior to the HPLC analysis is described. Polyclonal antibodies raised against 10-deacetylbaccatin III (10-DAB III), paclitaxel's main precursor in plant, were characterised by enzymed-linked immunosorbent assay. Immunoglobulins from selected antisera were immobilised on CNBr-activated Sepharose 4B. The immunoaffinity column was used for the purification of plant and plant cell culture extracts prior to their analysis by HPLC. Immunoaffinity chromatography enabled the selective concentration of taxoids and enhanced sample clean-up. PMID:12831195

Theodoridis, G; Haasnoot, W; Cazemier, G; Schilt, R; Jaziri, M; Diallo, B; Papadoyannis, I N; de Jong, G J

2002-03-01

202

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

203

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

204

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

205

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

206

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

207

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

208

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

209

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

210

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

211

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

212

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

213

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

214

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

215

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

216

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

217

Phytochemical analysis of ethanolic extract of Dichrostachys Cinerea W and Arn leaves by a thin layer chromatography, high performance thin layer chromatography and column chromatography  

PubMed Central

Background: The leaves of Dichrostachys cinerea are used as laxative, diuretic, painkiller. It is also used in the treatment of gonorrhoea, boils, oedema, gout, veneral diseases and nasopharyngeal affections, etc. Materials and Methods: The Phytochemical investigation of ethanolic extract of D. cinerea leaves were performed by standard chemical tests, thin layer chromatography (TLC) by using various solvent systems, and by high performance liquid chromatography (HPTLC). Two compounds were isolated by column chromatography and one of the compounds was identified by various spectral studies. Result: Preliminary phytochemical screening of ethanolic extract of D. cinerea leaves showed the presence of Carbohydrates, proteins, Glycosides, Saponins, Tannins, Aminoacids and Terpenoids. The TLC and HPTLC fingerprint of ethanolic extract were studied and various fractions were isolated by column chromatography and one of the fraction contain ?-amyrin glucoside which was confirmed by Infra Red[IR] Spectroscopy, 1H-Nuclear Magnetic Resonance (NMR), C-13 NMR and Mass spectroscopic (MS) studies.

Vijayalakshmi, M.; Periyanayagam, K.; Kavitha, K.; Akilandeshwari, K.

2013-01-01

218

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

National Technical Information Service (NTIS)

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...

J. A. Campbell B. D. Lerner R. M. Bean K. E. Grant R. B. Lucke

1994-01-01

219

NASA Li/CF(x) cell problem analysis: Anion exchange chromatography analysis  

NASA Astrophysics Data System (ADS)

An analysis was made of wiper samples used to wipe down lithium/chlorine fluorine battery components and production equipment. These components and equipment were potentially exposed to thionyl chloride vapors. In the presence of moisture, thionyl chloride decomposes to sulfur dioxide and hydrogen chloride. The wiper samples were analyzed for soluble chlorides and fluorides by anion exchange chromatography. During the examination of the test chromatographs, fluoride contamination was discovered in wiper samples from the test equipment. An analytical method to determine fluoride was developed. The first 3 extracts from the potentially exposed and clean wiper samples were tested, and the total fluoride from both groups determined. A comparison of the results from both groups was made to determine the extent of fluoride contamination.

Bytella, Joseph

1991-05-01

220

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

221

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

222

OPTICAL MEASUREMENTS OF CHEMICAL REACTION BY GAS DISSOLUTION IN A GAS-LIQUID MICROCHANNEL FLOW  

Microsoft Academic Search

The present study focuses on the mass transfer process through a gas-liquid interface in a microchannel flow. The objective is to investigate the CO2 dissolution process in water as the model of the gas-liquid mass transfer process by a simultaneous measurement of liquid velocity and pH distribution by PTV and LIF with a confocal microscope and a 3CCD color camera.

Issei Tsutsui; Yuriko Senga; Yohei Sato

223

Effect of Different Catalysts in Hybrid Gas-Liquid Discharge for the Removal of Organic Pollutant  

Microsoft Academic Search

Hybrid gas-liquid discharge technology is a promising water treatment technology. The synergic effect of activated alumina and discharge electric field could accelerate the removal of organic pollutants. Effect of loaded catalysts on the organic pollutant removal rate in hybrid gas-liquid discharge was investigated by loading FeOOH and nanosize TiO2 on the surface of activated alumina particles. The results revealed that

Linan Zhu; Ye Gao; Hui Liu; Jun Ma

2008-01-01

224

Gas–liquid flow in stirred reactors: Trailing vortices and gas accumulation behind impeller blades  

Microsoft Academic Search

In a gas–liquid stirred reactor, gas tends to accumulate in low-pressure regions behind the impeller blades. Such gas accumulation significantly alters impeller performance characteristics. We have computationally investigated gas–liquid flow generated by a Rushton (disc) turbine. Rotating Rushton turbine generates trailing vortices behind the blades, which influence the gas accumulation in the impeller region. Characteristics of these trailing vortices were

Vivek V. Ranade; Vaibhav R. Deshpande

1999-01-01

225

Minimum liquid fluidization velocity in gas-liquid-solid fluidized beds  

Microsoft Academic Search

Accurate detection of minimum liquid fluidization is essential to the successful operation of gas-liquid-solid fluidized beds, especially when particle or liquid properties evolve. A gas-liquid-solid system of 3-mm glass beads exhibits three distinct flow regimes as the liquid velocity is increased: compacted, agitated and fluidized-bed regimes. Measurements showed that the bed is not fluidized in the agitated bed regime. Pressure

L. A. Briens; C. L. Briens; A. Margaritis; J. Hay

1997-01-01

226

Flow structure of the solids in a 3-D gas-liquid-solid fluidized bed  

Microsoft Academic Search

Gas-liquid-solid fluidized systems have made inroads into a variety of industrial applications from heavy oil, petroleum resid, and synthetic crude processing to fermentation and aerobic biological wastewater treatment. Local and macroscopic solids flow structure and kinematics in a 3-D gas-liquid-solid fluidized bed were studied using a noninvasive radioactive-particle tracking (RPT) technique. Based on the multisite detection of γ radiations emitted

F. Larachi; M. Cassanello; J. Chaouki; C. Guy

1996-01-01

227

Flow characteristics of gas–liquid two-phase flow in plate heat exchanger  

Microsoft Academic Search

In order to clarify the gas–liquid two-phase flow characteristics in a plate heat exchanger, gas–liquid two-phase flows in simulated heat exchangers with a single channel placed in a vertical plane were visualized by a neutron radiography method. Air–water adiabatic two-phase flows and chlorofluorocarbon R141b boiling two-phase flows were visualized, and two-dimensional void fraction distributions were measured from visualized images via

Hitoshi Asano; Nobuyuki Takenaka; Terushige Fujii

2004-01-01

228

Hydrodynamics of vertical co-current gas-liquid-solid flows  

Microsoft Academic Search

A purpose built facility was used to obtain direct measurements of the phase holdups and velocities for gas-liquid-solid mixtures in vertical co-current upflow and downflow. Experiments were carried out by independently varying the flow rates of the gas, liquid and solid phases. The drift flux model was used to describe three-phase flow, and to correlate the data in terms of

R. S. Douek; G. F. Hewitt; A. G. Livingston

1997-01-01

229

Microporous hydrophobic hollow fiber modules for gas-liquid phase separation in microgravity  

Microsoft Academic Search

Gas-liquid interphase mass transfer operations, such as gas-liquid phase separation, gas absorption into liquid or dissolved gas separation from liquid, gas humidification and drying via liquid contact, and evaporative cooling are readily accomplished on the Earth with settling\\/spray chambers, packed towers, or bubble columns. This paper reports on gas-water mass transfer tests performed utilizing microporous hydrophobic Hollow Fiber Modules (HFMs)

Gary Noyes

1993-01-01

230

Membrane process for separating gases from gas-liquid charge streams  

Microsoft Academic Search

This patent describes the process for separating a gas from a gas-liquid charge. It comprises maintaining, as a non-porous membrane separating layer, a membrane of the polymeric reaction product of a poly oxyalkylene polyamine and a dissocyanate; passing into contact with the charge side of the membrane a gas-liquid charge; maintaining a pressure drop access the membrane whereby maintaining at

M. Pasternak; R. F. Beaupre

1990-01-01

231

Experimental study on hydrodynamic characteristics of upward gas–liquid slug flow  

Microsoft Academic Search

To clarify the impacts of the hydrodynamic boundary layer and the diffusion boundary layer in the near wall zone on gas–liquid two-phase flow induced corrosion in pipelines, the hydrodynamic characteristics of fully developed gas–liquid slug flow in an upward tube are investigated with limiting diffusion current probes, conductivity probes and digital high-speed video system. The Taylor bubble and the falling

Donghong Zheng; Defu Che

2006-01-01

232

Gas–liquid dynamics at low Reynolds numbers in pillared rectangular micro channels  

Microsoft Academic Search

Most heterogeneously catalyzed gas–liquid reactions in micro channels are chemically\\/kinetically limited because of the high\\u000a gas–liquid and liquid–solid mass transfer rates that can be achieved. This motivates the design of systems with a larger surface\\u000a area, which can be expected to offer higher reaction rates per unit volume of reactor. This increase in surface area can be\\u000a realized by using

S. R. A. de Loos; J. van der Schaaf; R. M. Tiggelaar; T. A. Nijhuis; J. C. Schouten

2010-01-01

233

A parametric study for high-efficiency gas-liquid separator design  

Microsoft Academic Search

A gas liquid centrifugal separator is widely used in industry on account of its simple geometry and little maintenance. These\\u000a separators have considerable advantages over filters, scrubbers or precipitators in term of compact design, lower pressure\\u000a drop and higher capacity. A gas liquid centrifugal separator is a device that utilizes centrifugal forces and low pressure\\u000a caused by rotational motion to

S. Nagdewe; J. K. Kwoon; H. D. Kim; D. S. Kim; K. M. Kwak; Toshiaki Setoguchi

2008-01-01

234

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

2013-08-15

235

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

236

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...

237

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

238

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 ...

239

Characterization of Haemophilus paragallinarum by analysis of whole cell carbohydrates, fatty acids and phospholipids.  

PubMed

The whole cell carbohydrate composition of 20 strains of Haemophilus paragallinarum including strains representing all established serotypes and two NAD-independent strains, was determined by capillary gas-liquid chromatography. Selected strains of H. paragallinarum were analysed for their cellular fatty acids and phospholipids compositions. The gas chromatographic analysis in combination with the mass spectrometric identification of the carbohydrate derivatives revealed similar patterns with all strains investigated. PMID:18670922

Mouahid, M; Hinz, K H; Engelhard, E; Mutters, R; Mannheim, W

1992-01-01

240

Enzyme Inhibition and Chromatographic Techniques: Comparative Studies and Application to Pesticide Residue Analysis  

Microsoft Academic Search

The development of enzyme inhibition techniques in relation to pesticide analysis is discussed, along with discussion of (a) principles of thin-layer chromatograph-enzyme inhibition (TLC-EI) technique, (b) general procedures of the technique, (c) the use of enzymes in combination with TLC and colorimetry, and (d) merits and limitations of the techniques. TLC-EI techniques and gas-liquid chromatography are compared based on sensitivity

C. E. Mendoza

1974-01-01

241

A gas-liquid-chromatographic procedure for separating a wide range of metabolites occuring in urine or tissue extracts.  

PubMed

1. A gas-liquid-chromatographic procedure is described which permits separation and identification on the same chromatogram of a wide range of substances occurring in urine or tissue extracts. The method uses hydrogen flame ionization, which detects organic compounds whether free or conjugated with no requirement for specific reactive groups. 2. For chromatography, carboxyl groups are quantitatively converted into methyl esters or trimethylsilyl esters. Phenolic, alcoholic and potential enolic groups are converted into trimethylsilyl ethers. Separations are carried out on a 6ft. column of either 10% F-60 (a polysiloxane) or 1% F-60, temperature programming at 2 degrees /min. being used over such part of the temperature range 30 degrees -260 degrees as is required. Propionyl derivatives of hydroxy compounds can also be used, but only on a non-quantitative basis. Derivatives and columns have been selected for optimum range of usefulness when large numbers of samples are examined by using automated gas chromatography. 3. The method is applicable to: fatty acids above butyric acid; di- and tri-carboxylic acids; hydroxy acids and keto acids; polyhydroxy and alicyclic compounds such as glycerol, inositol, quinic acid, shikimic acid, ascorbic acid and sugar alcohols; aromatic hydroxy and acidic compounds, both benzenoid and indolic; sesquiterpenes; steroids; glycine conjugates; mercapturic acids; glucuronides. It is not satisfactory for sulphate conjugates, iminazoles or polypeptides. 4. Methylene units provide an accurate and reproducible parameter for characterizing peak position. Methylene unit values are reported for a large variety of substances occurring in, or related to those occurring in, urine and tissue extracts. 5. The nature of derivatives was confirmed by combining gas chromatography with mass spectrometry. Combined gas chromatography-mass spectrometry gives a diagnostic tool of great power in the evaluation of metabolic patterns, and various uses are discussed. PMID:16742460

Dalgliesh, C E; Horning, E C; Horning, M G; Knox, K L; Yarger, K

1966-12-01

242

Off-line comprehensive 2-dimensional hydrophilic interaction x reversed phase liquid chromatography analysis of procyanidins.  

PubMed

The development of an off-line comprehensive 2-dimensional liquid chromatography (2-D-LC) method for the analysis of procyanidins is reported. In the first dimension, oligomeric procyanidins were separated according to molecular weight by hydrophilic interaction chromatography (HILIC), while reversed phase LC was employed in the second dimension to separate oligomers based on hydrophobicity. Fluorescence, UV and electrospray ionisation mass spectrometry (ESI-MS) were employed for identification purposes. The combination of these orthogonal separation methods is shown to represent a significant improvement compared to 1-dimensional methods for the analysis of complex high molecular weight procyanidin fractions, by simultaneously providing isomeric and molecular weight information. The low correlation (r(2)<0.2100) between the two LC modes afforded a practical peak capacity in excess of 2300 for the optimal off-line method. The applicability of the method is demonstrated for the analysis of phenolic extracts of apple and cocoa. PMID:19631941

Kalili, Kathithileni M; de Villiers, André

2009-08-28

243

Tryptophan analysis in peptides and proteins, mainly by liquid chromatography  

Microsoft Academic Search

Some of the general problems known in the analysis of tryptophan (both in its free form, alone or together with its metabolites, as well as in hydrolyzates of peptides or proteins, alone or together with all other amino acids) are described. This review includes an exhaustive literature overview using the author's experience with the preparation of derivatives and with various

Ibolya Molnár-Perl

1997-01-01

244

High-throughput simultaneous analysis of pesticides by supercritical fluid chromatography/tandem mass spectrometry.  

PubMed

Combination techniques such as gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) are commonly used for pesticide residue analysis, but there is no reported method for the simultaneous analysis of multiple pesticides in a sample using a single instrument. Supercritical fluid chromatography (SFC) offers high resolution at high flow rates and various separation modes and hence may aid the rapid simultaneous analysis of pesticide. We developed an SFC/MS/MS method and analyzed 17 pesticides with a wide range of polarities (logP(ow)=-4.6 to 7.05) and molecular weights (112.1-888.6) within 11min using a polar-embedded reversed-phase column. To the best of our knowledge, there is no previous report on the SFC analysis of a wide variety of compounds, including highly hydrophilic ones. By SFC, diquat dibromide (logP(ow)=-4.6), together with cypermethrin (logP(ow)=6.6) and tralomethrin (logP(ow)=5.05), could be detected in the presence of various other pesticides using a single mobile phase. SFC/MS allows for the rapid and simultaneous analysis of low concentrations (ng/L levels) of pesticides that typically need to be analyzed by GC/MS and LC/MS separately. PMID:23102524

Ishibashi, Megumi; Ando, Takashi; Sakai, Miho; Matsubara, Atsuki; Uchikata, Takato; Fukusaki, Eiichiro; Bamba, Takeshi

2012-11-30

245

Analysis of trace residues of tetracyclines in animal tissues and fluids using metal chelate affinity chromatography\\/HPLC  

Microsoft Academic Search

A novel method of analysis for the trace residue determination of tetracyclines in animal tissues and fluids has been developed. Clean?up of sample extracts is based upon the specific ability of tetracyclines to chelate with divalent metal ions (metal chelate affinity chromatography, MCAC) and determination made by high?performance liquid chromatography. The method has been tested for the determination of oxytetracycline

W. H. H. Farrington; J. Tarbin; J. Bygrave; G. Shearer

1991-01-01

246

[Quantitative analysis of butachlor, oxadiazon and simetryn by gas chromatography].  

PubMed

The quantitative analysis of the ingredients in 26% B-O-S (butachlor, oxadiazon and simetryn) emulsion by gas chromatographic method was carried out with a 5% SE-30 on Chromosorb AW DMCS, 2 m x 3 mm i.d., glass column at column temperature of 210 degrees C and detector temperature of 230 degrees C. The internal standard is di-n-butyl sebacate. The retentions of simetryn, internal standard, butachlor and oxadiazon were 6.5, 8.3, 9.9 and 11.9 min respectively. This method has a recovery of 98.62%-100.77% and the coefficients of variation of this analysis of butachlor, oxadiazon and simetryn were 0.46%, 0.32% and 0.57% respectively. All coefficients of linear correlation were higher than 0.999. PMID:12549176

Liu, F; Mu, W; Wang, J

1999-03-01

247

A simple gas-liquid chromatographic method with electron capture detection for the determination of progesterone in the blood of humans and domestic animals.  

PubMed

A simple routine method is reported for the determination of progesterone in blood by gas-liquid chromatography. An unlabelled internal standard, testosterone acetate, was added to plasma samples. Following preliminary purification by thin-layer chromatography, progesterone in pregnancy plasma was evaluated as the free steroid with a flame ionization detector. The hormone in the plasma of women during the menstrual cycle and of cycling domestic animals was determined as the 3-enol ester heptafluorobutyrate by electron capture detection. The validity of testosterone acetate as an internal standard was proved by simultaneous processing of [7alpha-3H]progesterone and a [4-14C]testosterone acetate and the determination of the isotope ratio in samples. The results of control experiments and normal values are also presented. PMID:1158996

Fehér, T; Fehér, K G; Bodrogi, L

1975-08-20

248

Quantitative analysis of food fatty acids by capillary gas chromatography  

Microsoft Academic Search

The superior efficiency of capillary columns is desirable for the gas chromatographic analysis of complex mixtures of fatty\\u000a acids, but there have been some reservations regarding quantitation and reproducibility. This paper discusses the use of wall-coated\\u000a glass capillary columns in a semiautomated system for the determination of food fatty acids. Glass columns coated with SP2340\\u000a were used for extended periods

H. T. Slover; E. Lanza

1979-01-01

249

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

PubMed

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 this review, various applications of HILIC are described for a number of environmental and food contaminants together with detailed methodological descriptions and the advantages or drawbacks of HILIC compared to other LC methods are critically discussed. In the first part of the review, an overview is given of the work that has been carried out with HILIC for the analysis of pharmaceuticals and pesticides in environmental samples. HILIC has shown its applicability for polar pharmaceuticals, such as antibiotics, estrogens and their metabolites, drugs of abuse, cytostatics, metformin and contrast agents. In the pesticide group, HILIC chromatography was helpful for polar phenylurea and organophosphorus pesticides. The second part of the review focuses on the analysis of antibiotic residues in food and feed with HILIC, while in the pesticide group, HILIC experiments have been reported for dithiocarbamates and quaternary ammonium compounds. The last chapter gives an overview of the analysis by HILIC of miscellaneous analytes in aquatic and food/feed samples. PMID:21316059

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

2011-09-01

250

Gas chromatography/matrix isolation-infrared spectrometry for air-sample analysis  

SciTech Connect

The report describes the application of gas chromatography/matrix-isolation 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 samples. The emphasis of the report is on the use of GC/MI-IR to identify semivolatile organic compounds in these extracts. The complementarity of GC/MI-IR spectrometry and conventional electron-impact ionization gas chromatography/mass spectrometry (EI-GC-MS) is illustrated. The capability of GC/MI-IR to discriminate between isomeric compounds that are difficult to separate chromatographically and to distinguish by EI-GC/MS is demonstrated. Preliminary results regarding the potential of GC/MI-IR spectrometry for the quantitative analysis of polycyclic aromatic hydrocarbons in air sample extracts are presented. Problem areas and modifications of a commercial GC/MI-IR system are discussed.

Childers, J.W.

1990-10-01

251

Analysis of glucosylceramides from various sources by liquid chromatography-ion trap mass spectrometry.  

PubMed

Liquid chromatography-mass spectrometry is one of the most powerful methods for the identification and detection of chemical structures of lipids. In this study, we attempted to identify the chemical structures of glucosylceramides from maize, rice, mushroom (maitake) and sea cucumber by liquid chromatography-ion trap mass spectrometry. For structural analysis of glucosylceramides, [M+H]+, [M+H-18]+ or [M+H-162]+ in the positive scan mode was used for MS/MS analysis to obtain product ion spectra. The typical signals which are characteristic for the sphingoid base moieties were observed while the isomers could not be distinguished. This method should be useful for the structural determination of diverse glucosylceramide molecular species. PMID:20513973

Sugawara, Tatsuya; Aida, Kazuhiko; Duan, Jingjing; Hirata, Takashi

2010-01-01

252

Solid phase microextraction coupled to liquid chromatography. Analysis of organosulphur compounds avoiding artifacts formation.  

PubMed

This work proposes the novel application of a microextraction technique, solid phase microextraction (SPME), coupled to liquid chromatography with UV detection (HPLC-UV) for the analysis of organosulfur compounds (OSCs) in garlic samples. Additionally, a comparative study of OSCs profiles obtained by SPME coupled to HPLC-UV and gas chromatography with flame photometric detector (GC-FPD), respectively; was carried out. This study provided complementary evidence about OSCs's lability and "artifacts" formation during the analytical process. Raw, cooked and distilled garlic samples were considered. The target analytes were diallyl disulphide (DADS), diallyl sulphide (DAS), diallyl trisulphide (DATS), allicin, 3-vinyl-4H-1,3-dithiin (3-VD), 2-vinyl-4H-1,2-dithiin (2-VD) and (E)- and (Z)-ajoene, which are the most important OSCs with biological activities present in raw and processed garlic. The coupling of SPME and HPLC showed to be reliable, fast, sensible and selective methodology for OSCs analysis. PMID:24679771

Locatelli, Daniela A; Altamirano, Jorgelina C; Luco, Juan M; Norlin, Rikard; Camargo, Alejandra B

2014-08-15

253

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

254

Interfacial gas–liquid transfer area in alkane–aqueous dispersions and its impact on the overall volumetric oxygen transfer coefficient  

Microsoft Academic Search

KLa and gas–liquid interfacial area per unit volume were quantified in 2.5–20% n-C10–13 aqueous dispersions agitated at 600–1200rpm. The interfacial area was quantified using high speed photography and image analysis. Interfacial area correlated strongly with KLa over all agitation rates and alkane concentrations, suggesting that the interfacial area was the major factor defining KLa in these dispersions.The bubble diameter and

L. D. C. Correia; C. Aldrich; K. G. Clarke

2010-01-01

255

Gas chromatography\\/matrix isolation-infrared spectrometry for air-sample analysis  

Microsoft Academic Search

The report describes the application of gas chromatography\\/matrix-isolation 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 samples. The emphasis of the report is on the use of GC\\/MI-IR to identify semivolatile organic compounds in these extracts. The complementarity of GC\\/MI-IR spectrometry and

Childers

1990-01-01

256

Novel detection schemes and automated image analysis algorithms for planar chromatography and gel electrophoresis  

SciTech Connect

After a discussion of charge coupled devices and personal computer capabilities, examples of their applications involving novel analytical techniques are presented: laser-based indirect fluorometric detection in thin-layer chromatography; on-line detection of DNA and proteins in gel electrophoresis by uv absorption; automated image analysis for distortion compensation in sequencing gel electrophoresis; and expert systems for data acquisition to achieve constant signal-to-noise, with application to DNA sequencing slab gels.

Koutney, L.B.

1992-09-09

257

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

Microsoft Academic Search

For routine monitoring of pesticides, a multiresidue analysis through solid-phase extraction technique and using high-performance\\u000a liquid chromatography (HPLC) in cotton seed cake (CSC) has been developed. Extraction of fortified samples was carried out\\u000a with aqueous acetone under vacuum. The concentrated extract was loaded onto the solid-phase extraction units, preconditioned\\u000a with acetonitrile. The extraction units were then washed with hexane and

Chander Mohan; Yogesh Kumar; Jyotsana Madan; Navneet Saxena

2010-01-01

258

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

Microsoft Academic Search

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

Carla Soler; Jordi Mañes; Yolanda Picó

2005-01-01

259

Analysis of brominated compounds in background air by gas chromatography–high-resolution mass spectrometry  

Microsoft Academic Search

The application of a gas chromatography–high-resolution mass spectrometry (GC–HRMS) system to the detection and quantitative analysis of bromine-containing compounds in the Earth’s atmosphere is described. By this technique, air samples are introduced to the HRMS system by GC while the HRMS system is tuned to the exact masses of the ions expected in the electron impact spectrum of each compound.

M. A. Engen; J. A. Culbertson; E. P. Grimsrud

1999-01-01

260

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

261

Sources of variation in the analysis of trichothecenes in cereals by gas chromatography-mass spectrometry  

Microsoft Academic Search

The sources of variation In the analysis of trichothecenes in cereals by gas chromatography mass spectrometry (GC-MS) were\\u000a studied and Identified. Ways to decrease some of the variations identified are presented and discussed. The method Is validated\\u000a for deoxynivalenol, nivalenol, 3-acetyldeoxynivalenol, fusarenon-X, diacetoxyscirpenol, HT-2 toxin and T-2 toxin. The general\\u000a variability in the performance of the GC-MS apparatus itself, as

M Eskola; A Rizzo

2001-01-01

262

Analysis of tropane alkaloids with thermospray high-performance liquid chromatography-mass spectrometry.  

PubMed

A thermospray high-performance liquid chromatography-mass spectrometry method for analysis of hyoscyamine and scopolamine in plant cell culture samples is described. The alkaloids were separated on a polymeric reversed-phase column with an alkaline ammonium acetate buffer-acetonitrile eluent. Selected-ion recording of the protonated molecular ions was used for quantitation of the compounds. The compounds were fragmented by discharge-assisted ionization and elevated thermospray capillary temperatures or ion repeller potentials. PMID:2026736

Auriola, S; Martinsen, A; Oksman-Caldentey, K M; Naaranlahti, T

1991-01-01

263

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

264

Packed-bed liquid-phase dispersion in pulsed gas-liquid downflow  

SciTech Connect

A theoretical analysis of a pulsed gas-liquid downward flow through a packed bed showed that the axial dispersion of the liquid-phase observed in such flows is mainly caused by the difference in velocity and rapid mixing between fast-moving liquid slugs and slow-moving liquid films. This chromatographic behavior was described by a model which considers the liquid phase as consisting of two continuous phases flowing cocurrently at different velocities with continuous material exchange between the two streams. The liquid dispersion in the column may be characterized by a single mixing parameter. Impulse response experiments, in good accord with the model, showed that liquid dispersion decreases with increasing liquid flow rate because of improving mixing, attains a constant asymptotic value at high gas velocities, and is generally smaller in pulsed flow than in the gas-continuous (trickle) flow regime. Additional advantages of pulsed flow operation in catalytic reactors are increased wetting of the pellets, enhanced transport coefficients, and improved flow uniformity through the bed.

Lerou, J.J.; Glasser, D.; Luss, D.

1980-02-01

265

The mechanism for the formation of slug flow in vertical gas liquid two-phase flow  

NASA Astrophysics Data System (ADS)

This paper studies the mechanism for the formation of a slug flow in vertical gas-liquid two-phase flow. By analyzing void fraction waves and their instability, it is proved that the formation of a slug flow regime is due to the increase of void fraction waves, which causes the conglomeration of gas bubbles and the coalescence of bubble clusters in unstable bubbly flow. Experiments and analysis show that intense turbulence can restrain the formation of Taylor bubbles. Therefore, in a large diameter vertical pipe, a Taylor bubble can form under a condition of low continuous volume flux due to the action of void fraction waves. However, the coalescence effect of void fraction waves as it affects bubbles is suppressed in high continuous volume flux, and therefore, a slug flow regime cannot be observed in the evolution of flow patterns. Under a condition of high continuous volume flux ( VL=0.15 m/s) described in the paper, the flow pattern evolution is from cap bubbly flow to cap churn flow, and then gradually to churn flow with the increase of void fraction.

Sun, Baojiang; Wang, Ruihe; Zhao, Xinxin; Yan, Dachun

2002-12-01

266

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

2008-09-01

267

Quantitative analysis of analgoantipyretics in dosage form using planar chromatography.  

PubMed

In the therapy of pain of weaker genesis, frequently used drugs usually represent a mix of analgoantipyretics of different chemical structures, mostly derivatives of salicylic acid, pyrazolone and p-aminophenol as well as derivatives of propionic and acetylsalicylic acid. For the determination of these drugs, different chromatographic methods have been applied, mostly HPLC, due to the the lower polarity (pyrazolones derivatives) and thermolability, as well as nonvolatility of compounds investigated. TLC method, considering advantages which include simplicity, reasonable sensitivity, rapidity, excellent resolving power and low cost has been successfully explored for the determination of analgoantipyretic compounds. The aim of this work was to develop a simple and rapid HPTLC method for the determination of acetylsalicylic acid, paracetamol, caffeine and phenobarbitone in dosage form. The determination of analgoantipyretics were performed on pre-coated HPTLC silica gel plates (10 x 20 cm(2)) by development in the mobile phase dichlormethane-ethyl acetate-cyclohexane-isopropanol-0.1 M HCL-formic acid (9:8:3:1.5:0.2:0.2 v/v/v/v/v/v). Migration distances (68.6+0.2 mm, 54.1+0.1 mm, 36.4+0.14 mm and 85.9+0.11 mm for acetylsalicylic acid, paracetamol, caffeine and phenobarbitone, respectively) with low RSD values (0.13--0.39%) showed a satisfactory reproductivity of the chromatographic system. TLC scanner was used for direct evaluation of the chromatograms in the reflectance/absorbance mode. Established calibration curves (r>0.999), precision (0.3--1.02%) and detection limits, as well as recovery values (96.51--98.1%) were validated and found to be satisfactory. The method was found to be reproducible and convenient for the quantitative analysis of compounds investigated in their dosage forms. PMID:11248516

Franeta, J T; Agbaba, D D; Eric, S M; Pavkov, S P; Vladimirov, S D; Aleksic, M B

2001-03-01

268

Pesticide analysis in rose wines by micellar electrokinetic chromatography.  

PubMed

In this work, the determination of 11 pesticides (pirimicarb, metalaxyl, pyrimethanil, procymidone, nuarimol, azoxystrobin, tebufenozide, fenarimol, benalaxyl, penconazole, and tetradifon) in rose wines by micellar EKC (MEKC) using reversed electrode polarity stacking mode (REPSM) as online preconcentration strategy is described. The MEKC buffer consisted of 100 mM sodium tetraborate and 30 mM SDS at pH 8.5 with 6% v/v 1-propanol. A solid-phase microextraction (SPME) procedure using PDMS/divinylbenzene (PDMS/DVB) fibers was applied to extract the selected pesticides from the rose wine samples. The comparison between the calibration curves obtained from hydroalcoholic solutions (12% v/v ethanol) and from rose wines (matrix matched calibration) showed the existence of a strong matrix effect. Furthermore, a comparison with calibration curves obtained with white wine samples also showed significant differences for most of the analyzed pesticides. As a result, a matrix matched calibration was developed. Quantitative extraction from spiked wine samples was carried out in triplicate at two levels of concentration (range 0.18-6.00 mg/L). LODs between 0.040 and 0.929 mg/L were achieved, which are below the maximum residue limits (MRLs) established for wine grapes (except for pirimicarb) by the EU and Spain legislation as well as by the Codex Alimentarius. The established method - which is solvent free, cost effective, and fast - was also applied to the analysis of several homemade rose wine samples and a commercial one. Two of the selected pesticides were found in some of the analyzed samples. PMID:18027361

Ravelo-Pérez, Lidia M; Hernández-Borges, Javier; Borges-Miquel, Teresa M; Rodríguez-Delgado, Miguel Angel

2007-12-01

269

Importance of instrumentation for fast liquid chromatography in pharmaceutical analysis.  

PubMed

In the last decade, an important technical evolution has occurred in pharmaceutical analysis with numerous innovative supports and advanced instruments that have been proposed to achieve fast or ultra-fast separations in LC with an excellent sensitivity and ease of operation. Among the proposed strategies to increase the throughput, the use of short narrow-bore columns packed with sub-3 ?m core-shell and porous sub-2 ?m particles have emerged as the gold standards. Nevertheless, to take the full benefits of these modern supports, a suitable chromatographic system has to be employed. This review summarizes the instrumental needs and challenges in terms of extra-column variance, dwell volume, maximum system pressure, detector data acquisition rate, and injection cycle time. In addition, because of their reasonable pressure drop, the use of columns packed with sub-3 ?m core-shell particles on a conventional LC instrument is discussed in detail. A methodology is proposed to check the compatibility between stationary phase and instrument, and some solutions are proposed to improve the performance of standard instruments. Finally, because the column technology is evolving faster than instrumentation, it is nowadays possible to purchase short, narrow-bore columns packed with 1.3 ?m core-shell particles. Micro columns (1 mm I.D.) packed with 1.7-1.9 ?m porous particles are also available from several providers, which limit frictional heating effects and reduce solvent and sample consumption. However, it remains difficult to find instruments compatible with such column geometries and a severe loss of performance may be observed due to the system itself. PMID:23571029

Fekete, Szabolcs; Kohler, Isabelle; Rudaz, Serge; Guillarme, Davy

2014-01-01

270

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

SciTech Connect

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. [Center for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Heverlee 3001 (Belgium); Yu, L.; Yan, J. H.; Cen, K. F. [State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027 (China); Cheron, B. G. [CNRS UMR 6614-CORIA, Saint Etienne du Rouvray 76801 (France)

2009-11-15

271

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

272

Emerging liquid chromatography-mass spectrometry technologies improving dried blood spot analysis.  

PubMed

Dried blood spots (DBS), a micro blood sampling technique, has recently gained interest in drug discovery and development due to its inherent advantages over the conventional whole blood, plasma or serum sample collection. Since the regulatory authorities have agreed to the use of blood as an acceptable biological matrix for drug exposure measurements, its applications have been extended not only to therapeutic drug monitoring but also to toxicokinetic and pharmacokinetic studies. The pharmaceutical industry is keen to promote DBS as a prominent tool in bioanalytical applications due to the financial, ethical and organizational issues involved in clinical trials. This could be accomplished due to the latest advances in modern analytical technology, particularly liquid chromatography-mass spectrometry. The present review discusses some of the emerging liquid chromatography-mass spectrometry technologies in improving DBS analysis for its innovative applications in the development of new drugs. PMID:24697571

Nageswara Rao, Ramisetti

2014-08-01

273

Analysis of antimycin A by reversed-phase liquid chromatography/nuclear magnetic-resonance spectrometry  

USGS Publications Warehouse

A mixture of closely related streptomyces fermentation products, antimycin A, Is separated, and the components are identified by using reversed-phase high-performance liquid chromatography with directly linked 400-MHz proton nuclear magnetic resonance detection. Analyses of mixtures of three amino acids, alanine, glycine, and valine, are used to determine optimal measurement conditions. Sensitivity increases of as much as a factor of 3 are achieved, at the expense of some loss in chromatographic resolution, by use of an 80-?L NMR cell, Instead of a smaller 14-?L cell. Analysis of the antimycin A mixture, using the optimal analytical high performance liquid chromatography/nuclear magnetic resonance conditions, reveals it to consist of at least 10 closely related components.

Ha, Steven T. K.; Wilkins, Charles L.; Abidi, Sharon L.

1989-01-01

274

Hydrodynamics and mass transfer in a draft tube gas-liquid solid spouted bed  

SciTech Connect

Experiments were conducted using various types of solid particles to investigate the hydrodynamic properties of a draft tube gas-liquid-solid spouted bed. The hydrodynamic properties under study include flow modes, pressure profile and pressure drop, bubble penetration, depth, overall gas holdup, apparent liquid circulation rate, and bubble size distribution. Three flow modes were classified: a packed bed mode, a fluidized bed mode, and a circulated bed mode. The bubble penetration depth in the annular region, overall gas holdup, and apparent liquid circulation rate increase with an increase in gas or liquid velocity. A model was proposed to describe the liquid circulation behavior in the draft tube gas-liquid-solid spouted bed. The optimal design of a draft tube gas-liquid-solid spouted bed was evaluated by considering four design variables including draft tube diameter, gas-liquid injector, top (above draft tube) spacing, and bottom (below draft tube) spacing. The effects of these design variables on the overall gas holdup were comprehensively examined for various gas and liquid velocities and solid particle properties. The 7.62 cm ID draft tube has highest overall gas holdup. The overall gas holdup increases with decreasing top spacing. The concentric tube gas-liquid injector with the smallest pore size gas distributor plate placed on the top of the outer tube gives rise to the holdup. Dissolution of benzoic acid pellets into water was used to obtain the solid liquid mass transfer coefficient in a draft tube gas-liquid-solid spouted bed. The in-bed benzoic acid concentration was examined to justify the use of the continuous flow stirred tank reactor (CSTR) model in the evaluation of the mass transfer coefficient.

Hwang, S.J.

1985-01-01

275

FBG application in monitoring the liquid-solid and gas-liquid phase transitions of water  

NASA Astrophysics Data System (ADS)

We propose to monitor the liquid-solid and gas-liquid phase transition of water based on FBG sensors. The naked FBGs and the packaged FBG temperature sensors are used to monitoring the liquid-solid phase transition of water at the same time in order to find its characteristics, including the supercooling state and the strain and pressure change introduced by the phase transition. Fourteen FBGs are packaged and arranged in a steam boiler in order to monitor the gas-liquid phase transition, including the temperature and pressure change inside the steam boiler and the strain of the boiler wall. The preliminary experimental results are demonstrated here.

Quan, Chai; Later, Khalil; Yang, Lijie; Peng, Shijun; Zhang, Anna; Hao, Qianqian; Zhang, Jianzhong; Sun, Weimin; Yuan, Libo; Peng, G. D.

2012-01-01

276

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

277

Immunoaffinity chromatography for the sample pretreatment of Taxus plant and cell extracts prior to analysis of taxanes by high-performance liquid chromatography  

Microsoft Academic Search

The application of immunoaffinity chromatography for the purification of Taxus plant and cell extracts prior to the HPLC analysis is described. Polyclonal antibodies raised against 10-deacetylbaccatin III (10-DAB III), paclitaxel’s main precursor in plant, were characterised by enzymed-linked immunosorbent assay. Immunoglobulins from selected antisera were immobilised on CNBr-activated Sepharose 4B. The immunoaffinity column was used for the purification of plant

G. Theodoridis; W. Haasnoot; G. Cazemier; R. Schilt; M. Jaziri; B. Diallo; I. N. Papadoyannis; G. J de Jong

2002-01-01

278

Screening and analysis of polar pesticides in environmental monitoring programmes by coupled-column liquid chromatography and gas chromatography—mass spectrometry  

Microsoft Academic Search

Screening and analysis of polar pesticides based on coupled-column reversed-phase liquid chromatography (LC-LC) and GC- or LC-MS is a powerful tool in the execution of environmental monitoring programmes. This paper presents a unified approach utilising LC-LC screening followed by GC-MS confirmation. As polar pesticides are not generally amenable to GC a widely applicable derivation technique is used. The results demonstrate

E. A. Hogendoorn; R. Hoogerbrugge; R. A. Baumann; H. D. Meiring; A. P. J. M. de Jong; P. van Zoonen

1996-01-01

279

Chemical fingerprint analysis of Fritillaria delavayi Franch. by high-performance liquid chromatography.  

PubMed

Bulbus of Fritillaria delavayi Franch. is the most commonly used antitussive and apophlegmatic in China and commonly prepared by water decoction. In this study, a novel and reliable method of high-performance liquid chromatography (HPLC) was developed both for quantitative analysis of 10 bioactive compounds (uracil, cytidine, inosine, uridine, guanosine, thymidine, adenosine, hypoxanthine, adenine and 2-deoxyadenosine) and chemical fingerprint analysis of F. delavayi Franch. In quantitative analysis, 10 compounds showed good regressions (R(2) > 0.9982) within test ranges and the recovery of the method was in the range of 96.33-104.51%. In the fingerprint analysis, 11 characteristic peaks were selected to evaluate the similarities of F. delavayi Franch. samples, and the HPLC chromatograms of 16 samples from different regions of China showed similar patterns. The results from the experiment demonstrated that the combinations of the quantitative and chromatographic fingerprint analysis offer an efficient way to evaluate the quality consistency of F. delavayi Franch. PMID:22282412

Duan, Baozhong; Huang, Linfang; Chen, Shilin

2012-02-01

280

Multivariate data analysis to characterize gas chromatography columns for dioxin analysis.  

PubMed

Principal component analysis (PCA) was applied for evaluating the selectivity of 22 GC columns for which complete retention data were available for the 136 tetra- to octa-chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Because the hepta- and octa-homologues are easy to separate the PCA was focused on the 128 tetra- to hexa-CDD/Fs. The analysis showed that 21 of the 22 GC columns could be subdivided into four groups with different selectivity. Group I consists of columns with non-polar thermally stable phases (Restek 5Sil MS and Dioxin 2, SGE BPX-DXN, Supelco Equity-5, and Agilent DB-1, DB-5, DB-5ms, VF-5ms, VF-Xms and DB-XLB). Group II includes ionic liquid columns (Supelco SLB-IL61, SLB-IL111 and SLB-IL76) with very high polarity. Group III includes columns with high-percentage phenyl and cyanopropyl phases (Agilent DB-17 and DB-225, Quadrex CPS-1, Supelco SP-2331, and Agilent CP-Sil 88), and Group IV columns with shape selectivity (Dionex SB-Smectic and Restek LC-50, Supelco ?DEXcst, Agilent VF-Xms and DB-XLB). Thus, two columns appeared in both Group I and IV (Agilent VF-Xms and DB-XLB). The selectivity of the other column, Agilent DB-210, differs from those of these four groups. Partial least squares (PLS) regression was used to correlate the retention times of the tetra- to hexa-CDD/Fs on the 22 stationary phases with a set of physicochemical and structural descriptors to identify parameters that significantly influence the solute-stationary phase interactions. The most influential physicochemical parameters for the interaction were associated with molecular size (as reflects in the total energy, electron energy, core-core repulsion and standard entropy), solubility (aqueous solubility and n-octanol/water partition coefficient), charge distribution (molecular polarizability and dipolar moment), and reactivity (relative Gibbs free energy); and the most influential structural descriptors were related to these parameters, in particular, size and dipolar moment. Finally, the PCA and PLS analyses were complemented with linear regression analysis to identify the most orthogonal column combinations, which could be used in comprehensive two-dimensional gas chromatography (GC×GC) to enhance PCDD/F separation and congener profiling. PMID:24813707

Do, Lan; Geladi, Paul; Haglund, Peter

2014-06-20

281

Clinical applications of fast liquid chromatography: a review on the analysis of cardiovascular drugs and their metabolites.  

PubMed

One of the major challenges facing the medicine today is developing new therapies that enhance human health. To help address these challenges the utilization of analytical technologies and high-throughput automated platforms has been employed; in order to perform more experiments in a shorter time frame with increased data quality. In the last decade various analytical strategies have been established to enhance separation speed and efficiency in liquid chromatography applications. Liquid chromatography is an increasingly important tool for monitoring drugs and their metabolites. Furthermore, liquid chromatography has played an important role in pharmacokinetics and metabolism studies at these drug development stages since its introduction. This paper provides an overview of current trends in fast chromatography for the analysis of cardiovascular drugs and their metabolites in clinical applications. Current trends in fast liquid chromatographic separations involve monolith technologies, fused-core columns, high-temperature liquid chromatography (HTLC) and ultra-high performance liquid chromatography (UHPLC). The high specificity in combination with high sensitivity makes it an attractive complementary method to traditional methodology used for routine applications. The practical aspects of, recent developments in and the present status of fast chromatography for the analysis of biological fluids for therapeutic drug and metabolite monitoring, pharmacokinetic studies and bioequivalence studies are presented. PMID:23462623

Baranowska, Irena; Magiera, Sylwia; Baranowski, Jacek

2013-05-15

282

The study of flow characteristic of gas-liquid two-phase flow based on the near-infrared detection device  

NASA Astrophysics Data System (ADS)

With the importance of the two-phase flow, many scholars pay attention on it; and for the so many parameters in the gas-liquid two-phase flow, flow characteristic is the basis. For the four flow patterns in the vertical direction, slug flow, bubbly flow, annular flow, and milk foam-like flow, the paper used the laser diode of 980nm and the silicon photodiode to detect the flow status. The absorption coefficients of the infrared in the gas and the liquid are very different; at the meantime, the infrared is affected by the interface obviously. As a result, it can reflect the fluctuation of the gas-liquid two-phase flow with the detection by the infrared. By analyzing the experiment data, four characteristic parameters are extracted, such as the average value, the variance, the kurtosis, and the frequency center of gravity. They can not only reflect the change of the different flow patterns, but also can reflect the fluctuation in the same flow pattern. The feature vector constituted of the four characteristic parameters can identify the flow pattern correctly in this system. What's more, it can achieve an accurate measurement of the real-time online, providing a basis for the other parameters' analysis in the gas-liquid two-phase flow.

Fang, Lide; Liang, Yujiao; Zhang, Yao; Zhang, Chen; Gao, Jingzhe

2014-04-01

283

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

2013-10-01

284

Thermal behaviour of agitated gas-liquid reactors with a vaporizing solvent\\/air oxidation of hydrocarbons  

Microsoft Academic Search

Many highly exothermic gas-liquid reactions are carried out with a vaporizing solvent, which after condensation is returned to the reactor. In this way the liberated reaction heat for a large part is absorbed by the cooling water flowing through the condenser. In order to determine the influence of this evaporation on the behaviour of an agitated gas-liquid tank reactor a

K. R. Westerterp; P. R. J. J. Crombeen

1983-01-01

285

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Default Factors for Petroleum Products and Natural Gas Liquids 1 2...GREENHOUSE GAS REPORTING Suppliers of Petroleum Products Pt. 98, Subpt. MM, Table...MM of Part 98âDefault Factors for Petroleum Products and Natural Gas Liquids 1...

2013-07-01

286

Study on the gas-liquid interface and polymer melt front in gas-assisted injection molding  

SciTech Connect

The algorithms are developed to predict the gas-liquid interface in gas-assisted injection molding. The simulation of two-dimensional, transient, non-isothermal and high viscous flow between two parallel plates with the generalized Newtonian fluid is presented in detail. The model takes into account the effects of the gas-liquid interface and polymer melt front.

Shen, Y.K. [Chien Hsin Coll. of Technology and Commerce, Chung-Li (Taiwan, Province of China). Dept. of Mechanical Engineering] [Chien Hsin Coll. of Technology and Commerce, Chung-Li (Taiwan, Province of China). Dept. of Mechanical Engineering

1997-03-01

287

Dynamics of gas–liquid flow in a rectangular bubble column: experiments and single\\/multi-group CFD simulations  

Microsoft Academic Search

Several flow processes influence overall dynamics of gas–liquid flow and hence mixing and transport processes in bubble columns. In the present work, we have experimentally as well as computationally studied the effect of gas velocity, sparger design and coalescence suppressing additives on dynamics of gas–liquid flow in a rectangular bubble column. Wall pressure fluctuations were measured to characterize the low

Vivek V. Buwa; Vivek V. Ranade

2002-01-01

288

Detailed analysis of petroleum hydrocarbon attenuation in biopiles by high-performance liquid chromatography followed by comprehensive two-dimensional gas chromatography.  

PubMed

Enhanced bioremediation of petroleum hydrocarbons in two biopiles was quantified by high-performance liquid chromatography (HPLC) followed by comprehensive two-dimensional gas chromatography (GCXGC). The attenuation of 34 defined hydrocarbon classes was calculated by HPLC-GCXGC analysis of representative biopile samples at start-up and after 18 weeks of biopile operation. In general, a-cyclic alkanes were most efficiently removed from the biopiles, followed by monoaromatic hydrocarbons. Cycloalkanes and polycyclic aromatic hydrocarbons (PAHs) were more resistant to degradation. A-cyclic biomarkers farnesane, trimethyl-C13, norpristane, pristane and phytane dropped to only about 10% of their initial concentrations. On the other hand, C29-C31 hopane concentrations remained almost unaltered after 18 weeks of biopile operation, confirming their resistance to biodegradation. They are thus reliable indicators to estimate attenuation potential of petroleum hydrocarbons in biopile processed soils. PMID:19185306

Mao, Debin; Lookman, Richard; Van De Weghe, Hendrik; Van Look, Dirk; Vanermen, Guido; De Brucker, Nicole; Diels, Ludo

2009-02-27

289

Elemental fluorine. Part 13. Gas-liquid thin film microreactors for selective direct fluorination.  

PubMed

Continuous flow gas-liquid thin film microreactors have been effectively used for the selective fluorination of a range of 1,3-dicarbonyl and aromatic substrates and, additionally, the conversion of aromatic disulfides to the corresponding sulfur pentafluorides. Scale-up was demonstrated by the application of a three channel microreactor device fabricated by replication of a single channel system. PMID:15100873

Chambers, R D; Holling, D; Spink, R C; Sandford, G

2001-12-01

290

Flow injection turbidimetric determination of total organic carbon with a gas–liquid transfer microreactor  

Microsoft Academic Search

A procedure for the determination of total organic carbon (TOC) and its fractions in industrial effluent samples is proposed. A flow injection system using a gas–liquid transfer microreactor was developed, and adapted to a turbidimetric spectrophotometer. Samples were decomposed into glass vials in a microwave oven and a fraction of the CO2 was injected into a carrier gas and pumped

José Neri Gottfried Paniz; Érico M. M Flores; Valderi L Dressler; Ayrton F Martins

2001-01-01

291

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

National Technical Information Service (NTIS)

The U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2006 Annual Report is the 30th prepared by the Energy Information Administration (EIA) to fulfill its responsibility to gather and report annual proved reserves estimates. The EIA annual re...

2007-01-01

292

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

National Technical Information Service (NTIS)

The U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2007 Annual Report is the 31st prepared by the Energy Information Administration (EIA) to fulfill its responsibility to gather and report annual proved reserves estimates. The EIA annual re...

2009-01-01

293

Centrifugal Scaling of Isothermal Gas-Liquid Flows in Horizontal Tubes.  

National Technical Information Service (NTIS)

To test the similarity criteria of two-phase gas-liquid flows, arising from the governing equations and boundary conditions, the flow of air and a water-glycerine mixture in a 50 mm diameter horizontal tube is compared with a two-phase flow of helium and ...

J. J. M. Geraets

1986-01-01

294

Effect of feedback and inter-particle collisions in an idealized gas–liquid annular flow  

Microsoft Academic Search

An idealized gas–liquid annular flow in a vertical rectangular channel was considered. Point sources of solid spheres were located on the walls to represent an atomizing wall film. The decrease in the deposition coefficient with increasing volume fraction, observed in laboratory studies, was examined by using a direct numerical simulation, which does not fully resolve scales of the size of

Yoichi Mito; Thomas J. Hanratty

2006-01-01

295

Numerical simulation of a gas-liquid flow in a fixed bed  

Microsoft Academic Search

A countercurrent gas-liquid flow through a fixed bed of spherical particles is examined numerically by solving the particle-scale equations governing the gas and liquid flows. The liquid is assumed to flow along the surface of the particles forming a thin film. The case of small gas flow rates is examined in detail first. In this limit the presence of the

Sangkyun Koo; Ashok S. Sangani

2001-01-01

296

Hydrodynamics in a cocurrent gas-liquid trickle bed at elevated pressures  

Microsoft Academic Search

Data on design and operation of trickle beds at elevated pressures are scarce. In this study the influence of the gas density on the liquid holdup, the pressure drop, and the transition between trickle and pulse flow has been investigated in a tricklebed reactor operating up to 7.5 MPa and with nitrogen or helium as the gas phase. Gas-liquid interfacial

W. J. A. Wammes; J. Middelkamp; W. J. Huisman; Baas de C. M; K. R. Westerterp

1991-01-01

297

Effect of hybrid gas-liquid electrical discharge on liquid foods (milk)  

Microsoft Academic Search

Pulsed high voltage discharges have been recently developed as sterilization method to replace the traditional thermal processes for the sterilization of liquid foods such as milk. The gas-liquid hybrid discharge (HD) reactor consists of plexiglass cylinder containing the liquid of high voltage electrode above liquid's surface and grounded electrode submerged in the liquid. The HD could produce both arc discharge

G. M. El-Aragi; Y. M. Abedel Rahman

2008-01-01

298

Two-Phase Flow Measurement Techniques in Gas-Liquid Systems.  

National Technical Information Service (NTIS)

A detailed summary of two-phase, gas-liquid measurement techniques is presented directed at the graduate engineer or practicing engineer as a refresher. Neither is expected to have any detailed knowledge of the mechanics of multiphase flows, but a working...

O. C. Jones

1980-01-01

299

Characterisation of gas–liquid two-phase flow inside capillaries  

Microsoft Academic Search

Continuous gas sparging inside ultrafiltration hollow fibres (with the feed) has been shown to be effective in enhancing permeate flux by reducing particle deposit on the membrane wall. The present study focuses on the hydrodynamic characterisation of gas–liquid two-phase flow inside glass capillaries in order to understand the mechanisms involved in the process improvement. In capillaries of inner diameter less

S. Laborie; C. Cabassud; L. Durand-Bourlier; J. M. Lainé

1999-01-01

300

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

National Technical Information Service (NTIS)

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. Estimates are p...

D. F. Morehouse J. H. Wood R. M. Zeinalpour R. S. Green S. G. Grape

1999-01-01

301

Energy Data Reports: Crude Petroleum, Petroleum Products, and Natural Gas Liquids, 1979. Final Summary.  

National Technical Information Service (NTIS)

Data are presented on crude oil, refined petroleum products and natural gas liquids supply, disposition and stocks in the US for 1979. Production of crude petroleum (including lease condensate) in the US in 1979 averaged 8,552,000 barrels/day, a decrease ...

M. R. Simmons

1980-01-01

302

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

National Technical Information Service (NTIS)

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 producing States and State subdivisions for the year 2004. Estimates are ...

J. H. Wood R. Zeinalpour R. S. Green S. G. Grape

2005-01-01

303

Velocity field in isothermal turbulent bubbly gas-liquid flow through a pipe  

Microsoft Academic Search

Velocity field was measured by laser Doppler velocimetry in isothermal, turbulent bubbly gas-liquid flow through a 26.6 mm inner diameter vertical pipe. The measurements were made about 33 diameters downstream from the pipe entrance, gas injection being just upstream of the entrance. The gas phase radial distribution at the measurement plane exhibited influence of the injection device in that higher

V. Velidandla; S. Putta; R. P. Roy

1996-01-01

304

Extremely fast gas/liquid reactions in flow microreactors: carboxylation of short-lived organolithiums.  

PubMed

Carboxylation of short-lived organolithiums bearing electrophilic functional groups such as nitro, cyano, and alkoxycarbonyl groups with CO2 to give carboxylic acids and active esters was accomplished in a flow microreactor system. The successful reactions indicate that gas/liquid mass transfer and the subsequent chemical reaction with CO2 are extremely fast. PMID:24863501

Nagaki, Aiichiro; Takahashi, Yusuke; Yoshida, Jun-Ichi

2014-06-23

305

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

National Technical Information Service (NTIS)

The U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2001 Annual Report is the 25th prepared by the Energy Information Administration (EIA) to fulfill its responsibility to gather and report annual proved reserves estimates. The EIA annual re...

2002-01-01

306

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

National Technical Information Service (NTIS)

The U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves 2002 Annual Report is the 26th prepared by the Energy Information Administration (EIA) to fulfill its responsibility to gather and report annual proved reserves estimates. The EIA annual re...

2002-01-01

307

Membrane–solvent selection for CO 2 removal using membrane gas–liquid contactors  

Microsoft Academic Search

Membrane gas–liquid contactors can provide very high interfacial area per unit volume, independent regulation of gas and liquid flows and are insensitive to module orientation, which make them very attractive in comparison with conventional equipments for offshore application. However, the membrane adds an additional resistance in the process of mass transfer. The mass transfer resistance of the membrane is affected

V. Y. Dindore; D. W. F. Brilman; F. H. Geuzebroek; G. F. Versteeg

2004-01-01

308

Development of a mass transfer machine for gas\\/liquid operations in the absence of gravity  

Microsoft Academic Search

The mass transfer machine that was developed for countercurrent gas\\/liquid operations is distinguished by an extremely high mass transfer efficiency per unit volume and by a very small overall volume. The design of the mass transfer machine, the experimental setup, the measuring equipment, and some of the results obtained are discussed. In order to understand the fluid dynamics of the

H. Brauer; W. Gaebelein

1978-01-01

309

Flow pattern and pressure drop in gas-liquid cocurrent downflow through packed beds  

Microsoft Academic Search

Correlations for pressure drop in gas-liquid cocurrent downflow through packed beds are presented, taking into cognizance the flow pattern of the phases and covering a wide range in experimental conditions. Criteria for flow regime discrimination are presented separately for low porosity and for high porosity packings.

J. Shiny; Y. B. G. Varma

1995-01-01

310

Finite element simulation of turbulent bubbly flows in gas-liquid reactors  

Microsoft Academic Search

A mathematical model for turbulent gas-liquid flows is presented. It is shown that bubble-induced buoyancy resembles natural convection and can be readily incor- porated into an incompressible flow solver by using an analog of the Boussinesq approximation. Extra transport equations are introduced to describe the evolution of the gas holdup and compute the turbulent eddy viscosity in the framework of

D. Kuzmin; S. Turek; H. Haario

311

Schlieren visualization of natural convection in binary gas–liquid systems  

Microsoft Academic Search

Natural convection in 23 gas–liquid systems in a quiescent cell is visualized by Schlieren techniques. CO2 absorption and desorption in 16 organic solvents and MEA aqueous solutions, and evaporation and condensation in six binary liquid mixtures are studied. Experimental data on densities and surface tensions of mixtures under investigation is presented. An empirical linear relationship between the density effect of

Andrei Okhotsimskii; Mitsunori Hozawa

1998-01-01

312

Multidimensional analysis of denatured milk proteins by hydrophobic interaction chromatography coupled to a dynamic surface tension detector  

Microsoft Academic Search

Multidimensional analysis of denatured milk proteins is reported using high-performance liquid chromatography (HPLC) combined with dynamic surface tension detection (DSTD). A hydrophobic interaction chromatography (HIC) column (a TSK-Gel® Phenyl-5PW column, TosoBiosep), in the presence of 3.0M guanidine hydrochloride (GdmHCl) as denaturing agent is employed as the mobile phase. Dynamic surface tension is measured through the differential pressure across the liquid–air

Emilia Bramanti; Wes W. C Quigley; Chandra Sortino; Francesca Beni; Massimo Onor; Giorgio Raspi; Robert E Synovec

2004-01-01

313

Determination of organophosphorus pesticide residues in human tissues by capillary gas chromatography–negative chemical ionization mass spectrometry analysis  

Microsoft Academic Search

We describe an analytical method that allows the determination of organophosphorus pesticides (OPs) in different human tissues. It involves an extraction procedure with ethanol–ethyl acetate, followed by gel permeation chromatography clean-up step and analysis by capillary gas chromatography–negative chemical ionization mass spectrometry in the selected ion monitoring mode. The method was tested for 37 OPs and the recoveries obtained vary

Mario Vincenzo Russo; Luigi Campanella; Pasquale Avino

2002-01-01

314

Simple, specific analysis of organophosphorus and carbamate pesticides in sediments using column extraction and gas chromatography  

USGS Publications Warehouse

A simple, specific procedure was developed for the analysis of organophosphorus and carbamate pesticides in sediment. The wet soil was mixed with anhydrous sodium sulfate to bind water and the residues were column extracted in acetone:methylene chloride (1:l,v/v). Coextracted water was removed by additional sodium sulfate packed below the sample mixture. The eluate was concentrated and analyzed directly by capillary gas chromatography using phosphorus and nitrogen specific detectors. Recoveries averaged 93 % for sediments extracted shortly after spiking, but decreased significantly as the samples aged.

Belisle, A.A.; Swineford, D.M.

1988-01-01

315

A Laboratory Experiment in Pharmaceutical Analysis: Analysis of Diazepam Tablets by High Pressure Liquid Chromatography  

ERIC Educational Resources Information Center

The experiment described was developed for the third-year course in inorganic and analytical pharmaceutical chemistry to provide students with "hands-on" experience with high pressure liquid chromatography. Assay procedures are given along with experimental parameters and student results. (LBH)

Bailey, Leonard

1978-01-01

316

Analysis of human serum by liquid chromatography–mass spectrometry: Improved sample preparation and data analysis  

Microsoft Academic Search

Discovery of biomarkers is a fast developing field in proteomics research. Liquid chromatography coupled on line to mass spectrometry (LC–MS) has become a powerful method for the sensitive detection, quantification and identification of proteins and peptides in biological fluids like serum. However, the presence of highly abundant proteins often masks those of lower abundance and thus generally prevents their detection

N. I. Govorukhina; T. H. Reijmers; S. O. Nyangoma; R. C. Jansen; R. Bischoff

2006-01-01

317

Analysis of herbicide Krovar I by liquid chromatography with atmospheric pressure chemical ionization mass spectrometry.  

PubMed

A simple, very efficient method is presented for routine analysis of herbicide Krovar I (active components bromacil and diuron) in water and soil samples. Water samples were extracted by liquid-liquid extraction with dichloromethane (DCM) as extraction solvent. For soil samples two different extraction techniques were compared: microwave-assisted solvent extraction and a shaking technique using a platform shaker. Extracts were analyzed by high performance liquid chromatography using a water:methanol gradient. Liquid chromatography was coupled with atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) for quantification of bromacil and diuron. Optimization of the APCI-MS was done by using standards in the flow injection analysis mode (FIA). Method detection limit for liquid samples for bromacil is 0.04 microg L(-1) and for diuron 0.03 microg L(-1). Method detection limit for soil samples is 0.01 microg g(-1) dry weight for both compounds. Results of analysis of field samples of water and soil are also presented. PMID:15132332

Furtula, Vesna; Kuo, Jen-ni

2004-03-01

318

Liquid-gas-liquid technique for microextraction and preconcentration of short chain fatty acids from aqueous samples.  

PubMed

In this study, an organic solvent-free microextraction technique termed liquid-gas-liquid microextraction (LGLME) was applied for cleanup and preconcentration of volatile short chain fatty acids in beverages and dairy products. Various parameters affecting the extraction efficiency such as extraction time, stirring speed, sodium chloride content, concentration and volume of donor and acceptor phases, and extraction temperature were studied. Repeatability (RSD, 4.2-8.5%), correlation coefficients (0.998-0.999), LODs (10-20 microg/L) and enrichment factors (152-249) were also investigated. Recoveries were achieved in the range of 90-102% in different matrices. The presented method was applied for the analysis of target analytes in some samples such as grape juice, vinegar and dairy products. PMID:19266551

Farajzadeh, Mir Ali; Assadi, Arsalan

2009-04-01

319

BIOINTERACTION ANALYSIS BY HIGH-PERFORMANCE AFFINITY CHROMATOGRAPHY: KINETIC STUDIES OF IMMOBILIZED ANTIBODIES  

PubMed Central

A system based on high-performance affinity chromatography was developed for characterizing the binding, elution and regeneration kinetics of immobilized antibodies and immunoaffinity supports. This information was provided by using a combination of frontal analysis, split-peak analysis and peak decay analysis to determine the rate constants for antibody-antigen interactions under typical sample application and elution conditions. This technique was tested using immunoaffinity supports that contained monoclonal antibodies for 2,4-dichlorophenoxyacetic acid (2,4-D). Association equilibrium constants measured by frontal analysis for 2,4-D and related compounds with the immobilized antibodies were 1.7–12 × 106 M?1 at pH 7.0 and 25°C. Split-peak analysis gave association rate constants of 1.4–12 × 105 M?1s?1 and calculated dissociation rate constants of 0.01–0.4 s?1 under the application conditions. Elution at pH 2.5 for the analytes from the antibodies was examined by peak decay analysis and gave dissociation rate constants of 0.056–0.17 s?1. A comparison of frontal analysis results after various periods of column regeneration allowed the rate of antibody regeneration to be examined, with the results giving a first-order regeneration rate constant of 2.4 × 10?4 s?1. This combined approach and the information it provides should be useful in the design and optimization of immunoaffinity chromatography and other analytical methods that employ immobilized antibodies. The methods described are not limited to the particular analytes and antibodies employed in this study but should be useful in characterizing other targets, ligands and supports.

Nelson, Mary Anne; Moser, Annette; Hage, David S.

2009-01-01

320

Predicting percent composition of blends of biodiesel and conventional diesel using gas chromatography–mass spectrometry, comprehensive two-dimensional gas chromatography–mass spectrometry, and partial least squares analysis  

Microsoft Academic Search

The percent composition of blends of biodiesel and conventional diesel from a variety of retail sources were modeled and predicted using partial least squares (PLS) analysis applied to gas chromatography–total-ion-current mass spectrometry (GC–TIC), gas chromatography–mass spectrometry (GC–MS), comprehensive two-dimensional gas chromatography–total-ion-current mass spectrometry (GCxGC–TIC) and comprehensive two-dimensional gas chromatography–mass spectrometry (GCxGC–MS) separations of the blends. In all four cases, the

Karisa M. Pierce; Stephen P. Schale

2011-01-01

321

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

322

Residual solvent analysis by gas chromatography in radiopharmaceutical formulations containing up to 12% ethanol.  

PubMed

For the detection and quantification of residual solvents in solutions of radiopharmaceuticals for human applications, a new analysis method was set up. With a simple direct gas chromatography injection, no special sample treatments or special injection techniques (such as head-space or solid-phase microextraction) are necessary. This method is especially suited for the fast and quantitative analysis of residual solvents in radiopharmaceutical formulations where 5-12% ethanol is present. The method proved to be both accurate and linear. The quantification limit is in the lower parts-per-million range, which is sufficient given the need for a fast analysis and the maximally allowed concentration for these residual solvents. PMID:17045174

Klok, Robert P; Windhorst, Albert D

2006-10-01

323

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

324

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

325

Streamlined F2-isoprostane analysis in plasma and urine with high-performance liquid chromatography and gas chromatography/mass spectroscopy.  

PubMed

F2-Isoprostanes in plasma and urine are generally determined by labor-intensive methods requiring sample purification by solid-phase extraction and thin-layer chromatography (TLC). A streamlined and more sensitive method for the measurement of esterified plasma F2-isoprostanes was developed by replacing these steps with high-performance liquid chromatography (HPLC) using an amino column with a hexane/2-propanol gradient. Pentafluorobenzyl esters of F2-isoprostanes were prepared and purified by HPLC, silylated, and then analyzed by gas chromatography (GC) with negative chemical ionization mass spectroscopy (NCI-MS). This method permits analysis with lower plasma volumes (100 microL) and greater sensitivity (to 10 pg; allowing detection to 50 pg/mL) than provided by other methods. Urinary F2-isoprostanes can also be efficiently quantified by this method, with 8-iso-PGF2alpha being identified as a major isomer. With this procedure, esterified plasma F2-isoprostanes were found to be 8.3-fold higher in an end-stage renal failure patient on hemodialysis and urinary 8-iso-PGF2alpha was 7.1-fold higher in a cigarette smoker than respective control subjects. This method, particularly the substitution of the TLC step common to other methods with HPLC, results in a more sensitive and reproducible assay. PMID:10805523

Walter, M F; Blumberg, J B; Dolnikowski, G G; Handelman, G J

2000-04-10

326

Analysis of amprolium by hydrophilic interaction liquid chromatography-tandem mass spectrometry.  

PubMed

We present a fast liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of the coccidiostat amprolium in food samples. Tandem mass spectrometry in a triple quadrupole was used for quantitative purposes, and the information from multiple-stage mass spectrometry in an ion-trap mass analyzer contributed to fragmentation studies. Hydrophilic interaction liquid chromatography (HILIC) in a Fused-Core column using isocratic elution (acetonitrile:formic acid/ammonium formate buffer pH 4, 50 mM (60:40)) successfully analyzed this compound in less than 3 min. The HILIC system was coupled to heated electrospray-MS/MS using highly selective-selected reaction monitoring (H-SRM) to improve sensitivity and selectivity for the analysis of amprolium, after a simple sample treatment based on an "extract and shoot" strategy. Accurate mass measurements were performed to identify the interfering compound responsible for causing matrix ion enhancement in the signal of amprolium. The addition of l-carnitine (the interfering compound) (1 microg L(-1)) to standards and sample extracts allowed the use of the external calibration method for quantitative purposes. The LC-MS/MS (H-SRM) method showed good precision (relative standard deviation, RSD, lower than 13%), accuracy and linearity and allowed the determination of amprolium down to the ppb level (LODs between 0.1 and 0.6 microg kg(-1)). PMID:20696436

Martínez-Villalba, Anna; Moyano, Encarnación; Galceran, M Teresa

2010-09-10

327

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

328

Analysis of carbohydrates and amino acids in vegetable waste waters by ion chromatography.  

PubMed

High-performance anion exchange chromatography coupled with pulsed amperometric detection was used for the quantitative determination of total and free sugars in olive oil mill waste waters (OMWW). Automated amino acid ion chromatography was employed to analyse total and free amino acids in the same OMWW. Sugars were analysed in samples pre-purified by means of a three-step purification procedure involving: (i) methanol precipitation of OMWW; (ii) dialysis of the obtained solid and liquid fractions; and (iii) chromatographic purification on RP18 phase followed by Amberlite resin. The amino acids were determined directly in samples obtained from the first two steps performed for sugar analysis. The analysis carried out with the reported methodologies allowed the quantitative determination of total sugars and amino acids and the differentiation between their free and bound forms. The sugars determined were arabinose, fructose, galactose, glucose, rhamnose, xylose, galacturonic and glucuronic acids, and the amino acids were Asp, Glu, Thr, Ser, Pro, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Arg and Cys. Asn, Gin, and Trp were not detected. The technological, biotechnological and environmental advantages arising from this analytical methodology applied to OMWW are briefly discussed. PMID:12693630

Arienzo, Michele; De Martino, Antonio; Capasso, Renato; Di Maro, Antimo; Parente, Augusto

2003-01-01

329

Dynamics of gas-liquid flows in bubble column reactors  

Microsoft Academic Search

Wall pressure fluctuations were measured in bubble columns at different locations and for different gas velocities and height to diameter ratios. Non-linear analysis of the acquired data of pressure fluctuations was carried out to quantify dynamic characteristics. A bubble–bubble interaction model was developed to simulate voidage fluctuations in bubble columns. Dynamic characteristics of the simulated voidage fluctuations were compared with

V. V. Ranade; R. P. Utikar

1999-01-01

330

Peptide-protein analysis and characterization by multidimensional liquid chromatography and capillary electrophoresis  

Microsoft Academic Search

This research was conducted to study the type of multidimensional liquid chromatography utilizing partitioning based chromatography in the first dimension. The “drifting peak” phenomenon was studied from the fundamental theory and practical viewpoint and various solutions were proposed and validated. Various types of two-dimensional HPLC which combine ion-exchange and reversed-phase chromatography or two different reversed-phase chromatography columns were explored to

Gang Huang

1998-01-01

331

[Study on the n-BuOH extract's fingerprint chromatography and bacteriostatic activity of Radix Isatis and correlation analysis].  

PubMed

The fingerprint chromatography and bacteriostatic activity of the n-BuOH extract of Radix Isatis were investigated. The chemical differemce in Radix Isatis from various sources was probed with system cluster analysis and it was co-researched with the bacteriostatic activity using correlation analysis in order to find the baterio static substances in Radix Isatis. PMID:16568664

Zhao, Yanling; Cao, Lin; Wang, Jiab; Jin, Cheng; Xiao, Xiaohe

2005-12-01

332

Multiple compounds determination and fingerprint analysis of Lidanpaishi tablet and keli by high-performance liquid chromatography  

Microsoft Academic Search

The objective of this paper was to establish an efficient method for quality control of Lidanpaishi (LDPS) tablet and keli, two famous traditional Chinese medicines. A simple and reliable high-performance liquid chromatography (HPLC) coupled with photodiode array detector (DAD) method was developed both for fingerprint analysis (FA) and quantitative determination. In quantitative analysis, linear regressions, limit of detection (LOD) and

Lina Xu; Xu Han; Yan Qi; Youwei Xu; Lianhong Yin; Jinyong Peng; Kexin Liu; Changkai Sun

2009-01-01

333

Gas–liquid simulation of an airlift bubble column reactor  

Microsoft Academic Search

The simulation of two-phase flow for an experimental airlift reactor (32-l volume) using commercially available software from Fluent Incorporated is presented here (http:\\/\\/www.fluent.co.uk). Data from the simulation is compared with the experimental data obtained by the tracking of a magnetic particle and analysis of the pressure drop to determine the gas hold-up. Comparisons between vertical velocity and gas hold-up were

M. Blažej; G. M. Cartland Glover; S. C. Generalis; J. Markoš

2004-01-01

334

Gas-liquid simulation of an airlift bubble column reactor  

Microsoft Academic Search

The simulation of two-phase flow for an experimental airlift reactor (32-l volume) using commercially available software from Fluent Incorporated is presented here (http:\\/\\/www.fluent.co.uk ). Data from the simulation is compared with the experimental data obtained by the tracking of a magnetic particle and analysis of the pressure drop to determine the gas hold-up. Comparisons between vertical velocity and gas hold-up

M. Bla; G. M. Cartland Glover; S. C. Generalis; J. Markoš

2004-01-01

335

Steroid receptor analysis by size-exclusion liquid chromatography: considerations for the clinical laboratory.  

PubMed

Steroid receptor activity can be more quickly estimated by size-exclusion chromatography than by conventional analysis on sucrose gradients, and profiles of receptor activity are better resolved. Here we discuss several factors affecting this form of analysis in clinical laboratories. The composition of the elution buffer influences steroid receptor elution and recovery: high ionic strength, neutral pH, and the presence of dimethylformamide are important. Of the TSK-SW (Beckman) size-exclusion chromatographic columns we considered, the TSK-G2000SW column appeared to be the most appropriate. "Reference" elution profiles are presented for several marker proteins and estrogen receptor forms generated under different sample-treatment conditions. In examining the sensitivity of receptor analyses by this method, we used fresh rodent preparations, a commercial receptor reference (Estrocept), and human tumor material obtained by needle biopsy. We also compared frozen and lyophilized receptor preparations with fresh ones. PMID:3978784

Pavlik, E J; Nelson, K; van Nagell, J R; Robinson, J C; Hanson, M B; Donaldson, E S; Flanigan, R C; Kenady, D E

1985-04-01

336

Analysis of nucleosides and nucleotides in infant formula by liquid chromatography-tandem mass spectrometry.  

PubMed

A method for the simultaneous analysis of nucleosides and nucleotides in infant formula using reversed-phase liquid chromatography-tandem mass spectrometry is described. This approach is advantageous for compliance testing of infant formula over other LC-MS methods in which only nucleotides or nucleosides are measured. Following sample dissolution, protein was removed by centrifugal ultrafiltration. Chromatographic analyses were performed using a C18 stationary phase and gradient elution of an ammonium acetate/bicarbonate buffer, mass spectrometric detection and quantitation by a stable isotope-labelled internal standard technique. A single laboratory validation was performed, with spike recoveries of 80.1-112.9% and repeatability relative standard deviations of 1.9-7.2%. Accuracy as bias was demonstrated against reference values for NIST1849a certified reference material. The method has been validated for the analysis of bovine milk-based, soy-based, caprine milk-based and hydrolysed milk protein-based infant formulae. PMID:23559337

Gill, Brendon D; Indyk, Harvey E; Manley-Harris, Merilyn

2013-06-01

337

Analysis of Soft Drinks: UV Spectrophotometry, Liquid Chromatography, and Capillary Electrophoresis  

NASA Astrophysics Data System (ADS)

Instrumental analysis students analyze commercial soft drinks in three successive laboratory experiments. First, UV multicomponent analysis is used to determine caffeine and benzoic acid in Mello YelloTM using the spectrophotometer's software and manually by the simultaneous equations method. The following week, caffeine, benzoic acid and aspartame are determined in a variety of soft drinks by reversed-phase liquid chromatography using 45% methanol/55% aqueous phosphate, pH 3.0, as the mobile phase. In the third experiment, the same samples are analyzed by capillary electrophoresis using a pH 9.4 borate buffer. Students also determine the minimum detection limits for all three compounds by both LC and CE. The experiments demonstrate the analytical use and limitations of the three instruments. The reports and prelab quizzes also stress the importance of the chemistry of the three compounds, especially the relationships of acid/base behavior and polarity to the LC and CE separations.

McDevitt, Valerie L.; Rodriguez, Alejandra; Williams, Kathryn R.

1998-05-01

338

Differential thermal analysis, thermal gravimetric analysis, and solid phase micro-extraction gas chromatography analysis of water and fuel absorption in diesel soot  

Microsoft Academic Search

An experimental investigation was conducted to analyze the absorption characteristics of deposited diesel soot by differential thermal analysis, thermal gravimetric analysis, and solid phase micro-extraction gas chromatography analysis. The results showed that dry diesel soot contained 2–3%w (percent by weight) of water and a maximum of 5%w hydrocarbons. Water wetted soot contained up to 40%w water, while diesel wetted soot

C. Ayrault; J. S. Chang; D. Ewing; J. S. Cotton; I. E. Gerges; J. Burgers

2010-01-01

339

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

340

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

341

Analysis of rocuronium in human whole blood and tissues using liquid chromatography-tandem mass spectrometry.  

PubMed

A rapid, accurate and sensitive liquid chromatography-tandem mass spectrometry method has been developed for the determination of a quaternary nitrogen muscle relaxant, rocuronium, in human blood. The procedure involves protein precipitation with chloroform and trichloroacetic acid, and purification using methanol. The chromatography was performed using a phenyl-hexyl column (150 × 2.0 mm i.d., 3 µm; Phenomenex) with a mobile phase consisting of 5 mM ammonium formate (pH 3.0) and acetonitrile. Multiple reaction monitoring was used for quantification. The assay was linear over a concentration range of 4-500 ng/mL for rocuronium with R(2) ? 0.998. The recoveries for this compound ranged from 96.0 to 109.1%. The intra-day and inter-day precision was less than 10.5% and the accuracy ranged from 106.6 to 114.9%. The validated method was applied to quantify the content of rocuronium in blood and a variety of tissues of a victim suspected of overdose. In conclusion, the method was successfully applied for the analysis of rocuronium in biological samples for forensic toxicology. PMID:23377654

Cho, Hwang Eui; Park, Mee Jung; Kim, Sun Cheun; Hong, Ran Seon; Moon, Dong Cheul; Ahn, Su Youn

2013-04-01

342

Doping control analysis of metamfepramone and two major metabolites using liquid chromatography-tandem mass spectrometry.  

PubMed

The sympathomimetic agent metamfepramone (2-dimethylamino-1-phenylpropan-1-one, dimethylpropion) is widely used for the treatment of the common cold or hypotonic conditions. Due to its stimulating properties and its rapid metabolism resulting in major degradation products such as methylpseudoephedrine and methcathinone, it has been considered relevant for doping controls by the World Anti-Doping Agency (WADA). The rapid degradation of the active drug complicates the detection of metamfepramone itself but the metabolites methylpseudoephedrine and methcathinone can be monitored, and the finding of the latter in particular allows the inference of a metamfepramone administration. In order to improve sports drug testing procedures, metamfepramone, methylpseudoephedrine and methcathinone were characterized using electrospray ionization-high resolution/high accuracy mass spectrometry, and a method employing liquid chromatography/tandem mass spectrometry was established that allowed the analysis of these three analytes by direct injection of 2 microL of urine specimens. The assay was validated with regard to specificity, lower limits of detection (2-10 ng mL(-1)), intraday and interday precision (3-17%) and ion suppression/enhancement effects. The developed procedure has been used to verify or falsify suspicious signals observed in routine screening procedures based on gas chromatography/mass spectrometry and yielded an adverse analytical finding concerning a metamfepramone administration in an authentic doping control sample. Although the active drug was not detected, the indicative metabolites methylpseudoephedrine and methcathinone were considered sufficient to infer the application of the prohibited drug. PMID:19661559

Thevis, Mario; Sigmund, Gerd; Thomas, Andreas; Gougoulidis, Vassilios; Rodchenkov, Grigory; Schänzer, Wilhelm

2009-01-01

343

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

344

Kosoku ekitai chromatography ni yoru sekiyukei ryushutsuyu oyobi zan (prime)yu no tanka suiso type bunseki ni kansuru kenkyu. (Hydrocarbon group-type analysis of petroleum distillates and residues by high-performance liquid chromatography).  

National Technical Information Service (NTIS)

On the hydrocarbon group-type separation and analysis by a high-performance liquid chromatography (HPLC), the improvement of a separation perfoemance and a sensitivity correction method for a differential refractometer (RI detector) was synthetically repo...

S. Matsuzawa E. Nakamura T. Yamamoto O. Setoguchi M. Sato

1990-01-01

345

US crude oil, natural gas, and natural gas liquids reserves, 1992 annual report  

SciTech Connect

This report presents estimates of proved reserves of crude oil, natural gas, and natural gas liquids as of December 31, 1992, as well as production volumes for the United States, and selected States and State subdivisions for the year 1992. Estimates are presented for the following four categories of natural gas: total gas (wet after lease separation), its two major components (nonassociated and associated-dissolved gas), and total dry gas (wet gas adjusted for the removal of liquids at natural gas processing plants). In addition, two components of natural gas liquids, lease condensate and natural gas plant liquids, have their reserves and production data 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 1992 is provided.

Not Available

1993-10-18

346

Liquid saturation and gas–liquid distribution in multiphase monolithic reactors  

Microsoft Academic Search

The monolith bed is one of the promising catalytic reactors for a number of chemical gas–liquid–solid processes. In the present work, liquid saturations for five different monoliths have been investigated experimentally in a cold-flow unit with a reactor diameter of 5.0cm. The influences of gas and liquid flow rates and of the direction of two-phase flow on liquid saturation were

Tobias Bauer; Shaibal Roy; Ruediger Lange; Muthanna Al-Dahhan

2005-01-01

347

Residence time distribution of the liquid in gas-liquid cocurrent upflow fixed-bed reactors  

Microsoft Academic Search

The authors present an experimental investigation of the residence time distribution (RTD) of the liquid in a gas-liquid upflow fixed-bed reactor with porous and nonporous particles and air\\/Newtonian or non-Newtonian systems. The piston-dispersion-exchange model with Danckwerts boundary conditions was used to describe the liquid flow. In the case of porous particles, the dynamic evolution of the tracer concentration in the

M. Giot

1996-01-01

348

A MULTILOOP SENSOR FOR THE FLOWRATE MEASUREMENT OF GAS-LIQUID TWO-PHASE FLOW  

Microsoft Academic Search

A multi-loop flowmeter is designed for the flowrate measurement of the gas-liquid two-phase flow. The differential pressure signals can be collected from the multi- loop sensor at different positions. The total flowrate measurement model is established according to the average differential pressure value obtained from the optimal position. The time serial of the signals is obtained by using the high

Xie Dailiang; Liang Guowei; Wang Fang

349

Dynamic simulation of dispersed gas-liquid two-phase flow using a discrete bubble model  

Microsoft Academic Search

In this paper a detailed hydrodynamic model for gas-liquid two-phase flow will be presented. The model is based on a mixed Eulerian-Lagrangian approach and describes the time-dependent two-dimensional motion of small, spherical gas bubbles in a bubble column operating in the homogeneous regime. The motion of these bubbles is calculated from a force balance for each individual bubble, accounting for

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

1997-01-01

350

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

351

A macroscopic model for countercurrent gas-liquid flow in packed columns  

Microsoft Academic Search

A macroscopic model based on the volume-averaged equations of motion is presented for countercurrent gas-liquid flow in a packed bed. The model yields a column-limited flooding point as the loss of existence of uniform states. It correctly predicts the existence of two uniform states below the flooding point. The lower branch corresponds to the trends commonly observed experimentally. It is

David C. Dankworth; S. Sundaresan

1989-01-01

352

Composite hollow fiber gas–liquid membrane contactors for olefin\\/paraffin separation  

Microsoft Academic Search

Gas–liquid membrane contactors frequently suffer from undesired wetting of the microporous membrane by the absorption liquid. Stabilization layers at the liquid-side of the microporous membrane potentially prevent this wetting. We apply such stabilized membranes in a membrane contactor using AgNO3 solutions as absorption liquid, to separate paraffins and olefins. Hollow fiber membrane modules with an effective surface area of 101.8cm2,

D. C. Nymeijer; T. Visser; R. Assen; M. Wessling

2004-01-01

353

Super selective membranes in gas–liquid membrane contactors for olefin\\/paraffin separation  

Microsoft Academic Search

In the present paper, selective composite membranes containing sulfonated poly(ether ether ketone) (SPEEK) layers on top of a hydrophobic, polypropylene support are applied as absorber and desorber in a gas–liquid membrane contactor system for the separation of paraffins and olefins. The water present in the absorption liquid swells the hydrophilic polymer sufficiently, making the membranes olefin-selective. As a result, even

Kitty Nymeijer; Tymen Visser; Rijanne Assen; Matthias Wessling

2004-01-01

354

Flow Field Prediction and Bubble Trajectory Model in Gas-Liquid Cylindrical Cyclone (GLCC) Separators  

Microsoft Academic Search

Several mechanistic models have been already developed for predicting the onset of liquid carry-over in Gas-Liquid Cylindrical Cyclone (GLCC) Separators. However, currently no model is available to predict gas carry-under. A bubble trajectory model has been developed that can be used to determine the initiation of gas carry-under in the GLCC and to design GLCC for field applications. The bubble

Ivan Mantilla; S. A. Shirazi; O. Shoham

1999-01-01

355

A three-dimensional CFD model for gas–liquid bubble columns  

Microsoft Academic Search

This paper discusses the development of a three-dimensional Euler–Lagrange CFD model for a gas–liquid bubble column. The model resolves the time-dependent, three-dimensional motion of small, spherical gas bubbles in a liquid. Our model incorporates all relevant forces acting on a bubble rising in a liquid, and accounts for two-way momentum coupling between the phases. The liquid-phase hydrodynamics are described using

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

1999-01-01

356

A Double-Convergence Numerical Algorithm for Gas-Liquid Two-Phase Transient Flow Model  

Microsoft Academic Search

At present, controlled pressure drilling technology has become the main way of modern drilling technology because it can effectively reduce, and even avoid pressure-related complicated drilling accidents, which would greatly reduce drilling costs. As the key technology of controlled pressure drilling, multiphase flow simulator has aroused extensive attention of scholars and oilfield service companies, among which, the gas-liquid two-phase flow

Liuyang Wang; Qingyou Liu; Guorong Wang; Jiajia Jing; Chenyu Xia

2010-01-01

357

Community Structure Detection in Complex Networks with Applications to Gas-Liquid Two-Phase Flow  

Microsoft Academic Search

We propose an algorithm to detect community structure in complex networks based on data field theory. The efficiency and accuracy\\u000a of the algorithm for computer-simulated and real networks make it feasible to be used for the accurate detection of community\\u000a structure in complex networks. Using the conductance fluctuating signals measured from gas-liquid two-phase flow dynamic experiments,\\u000a we construct the flow

Zhongke Gao; Ningde Jin

2009-01-01

358

New progress of the digital electrical capacitance tomography system for gas\\/liquid two phase flow  

Microsoft Academic Search

Electrical capacitance tomography (ECT) is gaining acceptance as a laboratory and industry tool to analyze gas\\/liquid two phase flow. To overcome the shortcomings of the existing analogue ECT system, a new 16-electrode digital electrical capacitance tomography system based on FPGA and DSP is designed. The new scheme can easily realize single frequency and multi-frequency excitation and demodulation. Furthermore, two kinds

Huaxiang Wang; Shan Xin; Xuehui Zhang

2009-01-01

359

Design and Development of Gas-Liquid Cylindrical Cyclone Compact Separators for Three-Phase Flow  

Microsoft Academic Search

The objective of this five-year project (October 1997 - September 2002) was to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil\\/water\\/gas separation. This project was executed in two phases. Phase I (1997 - 2000) focused on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC) Separator.

R. S. Mohan; O. Shoham

2001-01-01

360

Design and Development of Gas-Liquid Cylindrical Cyclone Compact Separators for Three-Phase Flow  

Microsoft Academic Search

The objective of this five-year project (October, 1997--September, 2002) is to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil\\/water\\/gas separation. This project will be executed in two phases. Phase I (1997--2000) will focus on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC) Separator. The activities

Ram S. Mohan; Ovadia Shoham

1999-01-01

361

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

362

DESIGN AND DEVELOPMENT OF GAS-LIQUID CYLINDRICAL CYCLONE COMPACT SEPARATORS FOR THREE-PHASE FLOW  

Microsoft Academic Search

The objective of this five-year project (October, 1997-September, 2002) is to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil\\/water\\/gas separation. This project will be executed in two phases. Phase I (1997-2000) will focus on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC{copyright}) Separator. The activities

Ram S. Mohan; Ovadia Shoham

2000-01-01

363

Design and Development of Gas-Liquid Cylindrical Cyclone Compact Separators for Three-Phase Flow  

Microsoft Academic Search

The objective of this five-year project (October 1997--September 2002) was to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil\\/water\\/gas separation. This project was executed in two phases. Phase I (1997--2000) focused on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC) Separator. The activities of this

R. S. Mohan; O. Shoham

2001-01-01

364

Modeling of droplet–droplet interaction phenomena in gas–liquid systems for natural gas processing  

Microsoft Academic Search

The design of efficient gas liquid separation units for natural gas production lines depends on the accurate estimation of the droplet size distribution. The droplet size can be estimated by considering breakage and coalescence phenomena. In particular, off-shore separation units working at high pressure (100–200bar) require special consideration of coalescence processes with multiple outcomes. This work discusses the introduction of

C. A. Dorao; L. E. Patruno; P. M. Dupuy; H. A. Jakobsen; H. F. Svendsen

2008-01-01

365

Simulation of the slug flow of a gas-liquid system in capillaries  

Microsoft Academic Search

A mathematical model for the gas-liquid slug flow in a capillary is developed. The velocity profiles in the bubble, film,\\u000a and interbubble liquid are calculated. The calculated results are in good agreement with the experimental data of other researchers.\\u000a The experimentally found bifurcational behavior of the slip velocity of bubbles relative to the two-phase mixture reported\\u000a in the literature is

R. Sh. Abiev

2008-01-01

366

A Microfluidic Device to Acquire Gaseous Samples Via Surface Tension Held Gas-Liquid Interface  

Microsoft Academic Search

We present a relatively simple and effective method for acquiring gaseous samples into microfluidic channels. Hydrophobic polymers are photopatterned on hydrophilic substrates. Due to surface tension, aqueous liquid is confined by the hydrophobic polymers, but not completely blocked by a physical wall, thus allowing an interface for gas-liquid interaction. Here, the mechanism is demonstrated by using hydrophobic (poly)iso-bornyl acrylate polymer

Sudheer S. Sridharamurthy; Hongrui Jiang

2007-01-01

367

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

SciTech Connect

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 for two-phase flow analysis, which is applicable to predict with appropriate accuracy the multi-dimensional its behavior. The direct observation using high-speed video camera was performed and revealed the multi-dimensional dynamic flow behavior with bubbles and gas-slug affected by the sudden expansion part (20 mm-tube to 50 mm-tube). The characteristic phenomena were observed such as bubble break-up, deformation due to the strong shear of liquid flow, or liquid micro jet penetration through the gas-slug, and so on. From these results, the flow regime map and the flow patterns at the below and above of the sudden expansion part were classified in relation to the bubble diameter. Additionally, the measurement of the void fraction profiles in the tube cross sections of sudden expansion were conducted at the different axial positions. The void fraction was measured using a point-electrode resistivity probe. The void fraction measurements in this study showed in detail that how the two phase flow develops along the direction of the downstream of the sudden expansion. In just above the sudden expansion, the void fraction distribution appeared the wall peak or the core peak in void fraction in the upstream of the sudden expansion. In the downstream of the sudden expansion, the void fraction distribution changes from a saddle shape or power-low shape into finally the saddle shape as the bubbly flow develops along the downstream of the sudden expansion. These experimental data in the sudden expansion of a vertical upward bubbly flow would become benchmark with respect to the multi-dimensional behavior of the two-phase flow analysis. (authors)

Koichi Kondo [Marine Technical College, 12-24, Nishikura-cho, Ashiya, Hyogo 659-0026 (Japan); Kenji Yoshida; Tadayoshi Matsumoto; Tomio Okawa; Isao Kataoka [Osaka University, 1-1, Yamadaoka, Suita-shi, Osaka, 5650871 (Japan)

2002-07-01

368

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

369

High Throughput Quantitative Analysis of Serum Proteins Using Glycopeptide Capture and Liquid Chromatography Mass Spectrometry  

SciTech Connect

It is expected that the composition of the serum proteome can provide valuable information about the state of the human body in health and disease and that this information can be extracted via quantitative proteomic measurements. Suitable proteomic techniques need to be sensitive, reproducible, and robust to detect potential biomarkers below the level of highly expressed proteins, generate data sets that are comparable between experiments and laboratories, and have high throughput to support statistical studies. Here we report a method for high throughput quantitative analysis of serum proteins. It consists of the selective isolation of peptides that are N-linked glycosylated in the intact protein, the analysis of these now deglycosylated peptides by liquid chromatography electrospray ionization mass spectrometry, and the comparative analysis of the resulting patterns. By focusing selectively on a few formerly N-linked glycopeptides per serum protein, the complexity of the analyte sample is significantly reduced and the sensitivity and throughput of serum proteome analysis are increased compared with the analysis of total tryptic peptides from unfractionated samples. We provide data that document the performance of the method and show that sera from untreated normal mice and genetically identical mice with carcinogen-induced skin cancer can be unambiguously discriminated using unsupervised clustering of the resulting peptide patterns. We further identify, by tandem mass spectrometry, some of the peptides that were consistently elevated in cancer mice compared with their control littermates.

Zhang, Hui; Yi, Eugene C.; Li, Xiao-jun; Mallick, Parag; Kelly-Spratt, Karen S.; Masselon, Christophe D.; Camp, David G.; Smith, Richard D.; Kemp, Christopher J.; Aebersold, Reudi

2005-02-01

370

Heterogeneous catalysis on solids of gases diffusing through a liquid layer, studied by inverse gas chromatography.  

PubMed

Physicochemical parameters for heterogeneous catalytic reactions when the catalytic bed was under a liquid phase have been determined, using a non-linear adsorption isotherm by the reversed-flow version of inverse gas chromatography (RF-GC). The mathematical analysis developed in heterogeneous catalysis, mass transfer across gas-liquid boundaries, and diffusion coefficients of gases in liquids was associated with a non-linear adsorption isotherm to find the relevant equations pertaining to the problem. These equations were then used to calculate the adsorption/desorption rate constant, the rate constant for the first-order catalytic reaction and the equilibrium constant for the non-linear adsorption isotherm. The diffusion coefficients of the reactant in the liquid and gaseous phases and the partition coefficients for the distribution of the reactant between the gaseous and liquid phase were also determined. PMID:12456100

Kapolos, John; Katsanos, Nicholas A

2002-11-15

371

Stripping of acetone from water with microfabricated and membrane gas-liquid contactors.  

PubMed

Stripping of acetone from water utilizing nitrogen as a sweeping gas in co-current flow was conducted in a microfabricated glass/silicon gas-liquid contactor. The chip consisted of a microchannel divided into a gas and a liquid chamber by 10 ?m diameter micropillars located next to one of the channel walls. The channel length was 35 mm, the channel width was 220 ?m and the microchannel depth 100 ?m. The micropillars were wetted by the water/acetone solution and formed a 15 ?m liquid film between them and the nearest channel wall, leaving a 195 ?m gap for gas flow. In addition, acetone stripping was performed in a microchannel membrane contactor, utilizing a hydrophobic PTFE membrane placed between two microstructured acrylic plates. Microchannels for gas and liquid flows were machined in the plates and had a depth of 850 ?m and 200 ?m respectively. In both contactors the gas/liquid interface was stabilized: in the glass/silicon contactor by the hydrophilic micropillars, while in the PTFE/acrylic one by the hydrophobic membrane. For both contactors separation efficiency was found to increase by increasing the gas/liquid flow rate ratio, but was not affected when increasing the inlet acetone concentration. Separation was more efficient in the microfabricated contactor due to the very thin liquid layer employed. PMID:24223420

Constantinou, Achilleas; Ghiotto, Francesco; Lam, Koon Fung; Gavriilidis, Asterios

2014-01-01

372

Ultrasound in gas-liquid systems: effects on solubility and mass transfer.  

PubMed

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 any side-effects of ultrasound on the concentrations measurements. Ultrasound effect on the apparent solubility is very low (below 12%). Conversely ultrasound greatly improves gas-liquid mass transfer, especially below gas induction speed, this improvement being boosted by pressure. In typical conditions of organic synthesis: 323 K, 1100 rpm, 10 bar, k(L).a is multiplied by 11 with ultrasound (20 kHz/62.6 W). The impact of sonication is much higher on gassing out than on gassing in. In the same conditions, this enhancement is at least five times higher for degassing. PMID:18468473

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

2008-09-01

373

Microporous hydrophobic hollow fiber modules for gas-liquid phase separation in microgravity  

NASA Astrophysics Data System (ADS)

Gas-liquid interphase mass transfer operations, such as gas-liquid phase separation, gas absorption into liquid or dissolved gas separation from liquid, gas humidification and drying via liquid contact, and evaporative cooling are readily accomplished on the Earth with settling/spray chambers, packed towers, or bubble columns. This paper reports on gas-water mass transfer tests performed utilizing microporous hydrophobic Hollow Fiber Modules (HFMs) of the type currently employed as blood oxygenators in heart-lung machines. In these HFMs, gases are transferrred to and from water or other hydrophilic liquids through the microporous fiber walls; liquid water does not enter the pores of the highly hydrophobic wall material. The experiments included air-water phase separation, absorption of oxygen and carbon dioxide into water and separation of these dissolved gases from water, air humidification and drying by contact with temperature-controlled water, and controlled evaporation of water into a vacuum. In each of these experiments, a small, light HFM sucessfully performed the mass tranfer function, with no leakage of liquid water through the porous walls of the hollow fibers, even with high pressure across the fiber wall for extended periods of time. These results demonstrate that gas-liquid mass transfer unit operations on hydrophilic liquids, implemented with microporous hydrophobic HFM technology, are ready for use in microgravity fluid processing systems.

Noyes, Gary

374

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

375

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

376

Calculations of Gas-liquid Equilibrium in Wellbore with High Carbon dioxide Flow  

NASA Astrophysics Data System (ADS)

Carbon dioxide injection not only enhances the oil recovery dramatically, but also it will reduce the greenhouse effect, therefore, Carbon dioxide injection technique is applied extensively. During the process of carbon dioxide displacement, when carbon dioxide breaks though into oil production wells, carbon dioxide content will impacts the phase state and physical properties of the mixed liquor in the wellbore, as a result, it will affect the calculation of temperature and pressure in oil production wells. Applying the conventional black-oil model to calculate the phase state of the miscible fluids is unacceptable. To tackle the problem, this paper uses the gas-liquid flash theory and component model to program software, so that the phase state (gas, liquid or gas-liquid) and physical properties of the mixed liquor (including hydrogen sulfide, carbon dioxide and hydrocarbon) under initial conditions is calculated, moreover, the impact of carbon dioxide content on the physical properties(mainly including density, viscosity, specific heat at const pressure, surface tension, etc) of mixed liquor in oil production wells is analyzed in this paper. The comparison of the results shows that this model can meet the engineering needs with high accuracy.

Zhang, Jiaming; Wu, Xiaodong; Wang, Bo; Liu, Kai; Gao, Yue

2014-05-01

377

Analysis of radioactive waste samples by ion chromatography-ICP/MS  

SciTech Connect

A comprehensive ion chromatography (IC) with beta-counting (beta) and inductively coupled plasma mass spectrometry (ICP/MS) detection approach has been developed to separate and detect 20 radionuclides in a Hanford waste tank sample. The IC separation was performed using a multi-functional group (anion/cation) resin and eluents of oxalic acid, diglycolic acid, and hydrochloric acid. Shorter-lived radionuclides were detected by a solid-state beta scintillation counter on-line with the IC separation. Mass spectrometry detection using an efficient and robust plasma ionization source provides isotopic discernability for both stable isotopes and long-lived radioactive species. Effective separation of over 47 elements and 160 isotopes was obtained from a single-elution scheme lasting 70 min. Automated IC separations provide the potential for rapid isotopic and radionuclide analysis of complex radioactive waste, using minimal sample and reagent volumes and reducing personnel exposures.

Farmer, O.T. III; Reeves, J.H.; Wyse, E.J.; Clemeston, C.J.; Barinaga, C.J.; Smith, M.R.; Koppenaal, D.W.

1994-10-01

378

Monosaccharide compositional analysis of marine polysaccharides by hydrophilic interaction liquid chromatography-tandem mass spectrometry.  

PubMed

A simple and sensitive method was developed using hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry for determination of monosaccharides liberated from marine polysaccharides by acidic hydrolysis. Optimal separation of diastereomeric monosaccharides including hexoses, pentoses, and deoxyhexoses was achieved using an aminopropyl bonded column with mobile phase containing ternary solvents (acetonitrile/methanol/water) in conjunction with MS/MS in SRM mode. Mechanisms for fragmentation of deprotonated monosaccharides with regard to cross-ring cleavage were proposed. Matrix effects from coeluting interferences were observed and isotopic-labeled internal standard was used to compensate for the signal suppression. The method demonstrated excellent instrumental limits of detection (LOD), ranging from 0.7 to 4.2 pg. Method LODs range from 0.9 to 5.1 nM. The proposed method was applied to the analysis of polysaccharides in seawater collected from the open leads of the central Arctic Ocean in the summer of 2008. PMID:21305371

Gao, Qiuju; Nilsson, Ulrika; Ilag, Leopold L; Leck, Caroline

2011-03-01

379

Indirect hydrogen analysis by gas chromatography coupled to mass spectrometry (GC-MS).  

PubMed

Gas chromatography (GC) is an analytical tool very useful to investigate the composition of gaseous mixtures. The different gases are separated by specific columns but, if hydrogen (H2 ) is present in the sample, its detection can be performed by a thermal conductivity detector or a helium ionization detector. Indeed, coupled to GC, no other detector can perform this detection except the expensive atomic emission detector. Based on the detection and analysis of H2 isotopes by low-pressure chemical ionization mass spectrometry (MS), a new method for H2 detection by GC coupled to MS with an electron ionization ion source and a quadrupole analyser is presented. The presence of H2 in a gaseous mixture could easily be put in evidence by the monitoring of the molecular ion of the protonated carrier gas. PMID:23893637

Varlet, V; Smith, F; Augsburger, M

2013-08-01

380

Analysis of insect pheromones by quadrupole mass fragmentography and high-resolution gas chromatography.  

PubMed

A sensitive technique is described for the analysis of insect pheromones. Insect extracts are separated into fractions by column chromatography and are analyzed directly by quadrupole mass fragmentography on high-resolution glass capillary columns and by mass spectrometry. Applications are illustrated with two important pests. In the codling moth, trans-8, trans-10-dodecadien-1-ol was found to be present at a level of 3.5 ng per female, and in the European grapevine moth trans-7, cis-9-dodecadienyl acetate at a level of 1.6 ng. Both compounds appear to be present in high isomeric purity in the female insect and are absent in the corresponding males. PMID:1150795

Buser, H R; Arn, H

1975-03-19

381

Ultraperformance liquid chromatography with electrospray ionization ion trap mass spectrometry for chondroitin disaccharide analysis.  

PubMed

Chondroitin sulfate (CS) has an important role in cell division, in the central nervous system, and in joint-related pathologies such as osteoarthritis. Due to the complex chemical structure and biological importance of CS, simple, sensitive, high resolution, and robust analytical methods are needed for the analysis of CS disaccharides and oligosaccharides. An ion-pairing, reversed-phase, ultraperformance liquid chromatography (IPRP-UPLC) separation, coupled to electrospray ionization mass spectrometry with an ion trap mass analyzer, was applied for the analyses of CS-derived disaccharides. UPLC separation technology uses small particle diameter, short column length, and elevated column temperature to obtain high resolution and sensitivity. Hexylamine (15 mM) was selected as the optimal ion-pairing reagent. PMID:19769936

Solakyildirim, Kemal; Zhang, Zhenqing; Linhardt, Robert J

2010-02-01

382

Ultraperformance Liquid Chromatography with Electrospray Ion Trap Mass Spectrometry for Chondroitin Disaccharide Analysis  

PubMed Central

Chondroitin sulfate (CS) has an important role in cell division, in the central nervous system, and in joint related pathologies such as osteoarthritis. Due to the complex chemical structure and biological importance of CS, simple, sensitive, high-resolution, and robust analytical methods are needed for the analysis of CS disaccharides and oligosaccharides. An ion pairing, reversed-phase, ultraperformance liquid chromatography (IPRP-UPLC) separation, coupled to electrospray ionization mass spectrometry with ion trap mass analyzer was applied for the analyses of CS-derived disaccharides. UPLC separation technology utilizes small particle diameter, short column length, and elevated column temperature to obtain high resolution and sensitivity. Hexylamine (15 mM) was selected the optimal ion-pairing reagent.

Solakyildirim, Kemal; Zhang, Zhenqing; Linhardt, Robert J.

2010-01-01

383

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

2014-03-01

384

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

2010-06-01

385

[Quantitative analysis of deacylgymnemic acid by high-performance liquid chromatography].  

PubMed

A method of the quantitative analysis was established for the determination of deacylgymnemic acid (DAGA) in the alkaline hydrolysate of the sample containing gymnemic acids which are ingredients of Gymnema sylvestre R. BR. leaves, by means of high-performance liquid chromatography. This method was used for comparing the contents of gymnemic acids in various samples. The amount of gymnemic acids analyzed as DAGA in 70% ethanol extract of dry leaves was about twice that in hot water extract. The commercial health-supplemental foods of five companies were investigated for the contents of gymnemic acids as DAGA and there were large differences from 38 to 251 mg in the dosage per day recommended by each company. PMID:8492295

Suzuki, K; Ishihara, S; Uchida, M; Komoda, Y

1993-04-01

386

Analysis of the surface energy of pharmaceutical powders by inverse gas chromatography.  

PubMed

The behavior of pharmaceutical solids, during either processing or use, can be noticeably affected by the surface energetics of the constituent particles. Several techniques exist to measure the surface energy, for example, sessile drop, and dynamic contact angle measurements. Inverse gas chromatography (IGC) is an alternative technique where the powder surface is characterized by the retention behavior of minute quantities of well-characterized vapors that are injected into a column containing the material of interest. Recently published articles using IGC on pharmaceutical powders have ranged from linking surface energetic data with triboelectric charging to studying the effect of surface moisture on surface energetics. Molecular modelling has also recently been used to explore the links between IGC data and the structural and chemical factors that influence surface properties, thereby achieving predictive knowledge regarding powder behavior during processing. In this minireview, the reported applications of IGC in the analysis of pharmaceutical powders are summarized and the major findings highlighted. PMID:11835214

Grimsey, Ian M; Feeley, Jane C; York, Peter

2002-02-01

387

Analysis for urinary catecholamines by liquid chromatography with amperometric detection: methodology and clinical interpretation of results.  

PubMed

A method is presented for the quantitative analysis of urinary unconjugated norepinephrine, epinephrine, and dopamine as discrete entities. The procedure requires initial purification of the specimen on aluminum oxide and a boric acid-gel. We used "high-performance" reversed-phase paired-ion chromatography, with a flow-through amperometric cell as the detector. The CV was 6% for determination of norepinephrine, 11% for epinephrine, and 6% for dopamine monitored at physiologic concentrations of these compounds in urine. In a population study, urine specimens from 117 normal pediatric and adult subjects, 85 hypertensive patients, and 22 patients with surgically proved pheochromocytoma were analyzed. The specificity of the method for detection of pheochromocytoma was 100%, with a sensitivity of 97%. PMID:759019

Moyer, T P; Jiang, N S; Tyce, G M; Sheps, S G

1979-02-01

388

Uncertainty estimation related to analysis of volatile aromatic hydrocarbons by static headspace gas chromatography.  

PubMed

A study of the analysis of benzene, toluene, ethylbenzene and xylenes by static headspace gas chromatography illustrated the estimation of uncertainty associated with the influence of several parameters, such as preparation of the standard solutions, calibration of the instrument, recovery and limit of detection. The objective of the investigation was to indicate the contribution of each stage in the developed procedure on the uncertainty measurement of the determination of volatile aromatic hydrocarbons in surface and underground water. The uncertainty sources were identified and illustrated in an effect diagram. The data illustrated the evaluation of uncertainty by the quantification of the uncertainty arising separately from each source. It has been demonstrated that data can be used to estimate the uncertainty resulting from the combined effect of all sources. PMID:23885042

Pavlova, Antoaneta; Stoyanova, Olga; Ivanova, Pavlina; Dimova, Teodora

2014-08-01

389

Inline blood gas analysis by gas chromatography in patients during and after coronary artery surgery.  

PubMed

A system was evaluated of measuring Pao2 and Pao2 by an inline sensor in the brachial artery and gas chromatography. Eight patients having coronary artery vein grafts were studied during anaesthesia, operation, perfusion and for 24 hours afterward. Compared to conventional blood gas analysis by polarography (electrodes), the chromatographic method gave readings for Pao2 which were not significantly different during normothermia. During hypothermic perfusion, the chromatographic system read significantly higher than the bench electrode, due at least in part to a difference in temperature correction. For Pao2 the correlation between the two methods was close and differences were clinically insignificant. The Sentorr blood-gas analyser provides a sensitive, accurate indicator of changes in oxygenation, ventilation and circulation during anaesthesia and in the intensive care unit. PMID:466559

Moffitt, E A; McLaren, R G; Imrie, D D; Allen, C T; Kinley, C E; Parrott, J C

1979-05-01

390

[Analysis of phthalates in plastic food-packaging bags by thin layer chromatography].  

PubMed

The method for simultaneous determination of four phthalates, namely dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP) and di (2-ethylhexyl) phthalate (DEHP) in plastic food-packaging bags by thin layer chromatography (TLC) was developed. The plastic food-packaging bags were extracted with ethanol by ultrasonication, then the mixture was filtrated through membrane (0.45 microm). The mixture of ethyl acetate-anhydrous ether-isooctane (1 : 4 : 15, v/v) was used as developing agent on the TLC silica gel plate for development. The filtered liquid was spotted on the TLC plate dealt by acetone, and detected with scanning wavelength of 275 nm and reference wavelength of 340 nm. The qualitative analysis of the phthalates was performed using the R(f) values of the chromatogram. The quantitative analysis was performed with external standard method. Good linearities were obtained for DMP, DEP, DBP and DEHP. The detection limits were 2.1 ng for DMP, 2.4 ng for DEP, 3.4 ng for DBP and 4.0 ng for DEHP. The relative standard deviations (RSDs) of the four phthalates were 2.8% - 3.5%. The recoveries of the four phthalate standards in real sample were 78.58% - 111.04%. The method presented has the advantages of high precision, high sensitivity, small sample size, and simple pretreatment . The method was used to detect the four phthalates in the food-packaging bags. The contents in real samples were close to the results by gas chromatography. PMID:16827317

Chen, Hui; Wang, Yuan; Zhu, Ruohua

2006-01-01

391

Analysis of alkenone unsaturation indices with fast gas chromatography/time-of-flight mass spectrometry.  

PubMed

Extensively purified C37 alkenone references and mixtures thereof were analyzed by gas chromatography/flame ionization detection (GC/FID) and fast gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS), to establish the latter as an alternative, fast, and reliable analysis method for alkenone unsaturation indices (U(k')(37)). This index is a tool for past sea surface temperature reconstructions with extensive use in paleoclimate and paleoceanographic research. TOF-MS was chosen because of its unique capability to acquire full-range spectra at high data rates (up to 500 spectra s(-1)) and to produce homogeneous spectra across a gaschromatographic peak, allowing faster separations than conventional GC/MS and the employment of enhanced peak deconvolution algorithms. Analysis time per sample could be reduced to run times of <10 min, i.e., by a factor of approximately 10 compared to conventional GC/FID (90-100 min) methods. However, %@mt;sys@%%@ital@%%@bold@%U%@reset@%%@rsf@%%@sx@%37%@be@%%@ital@%k%@rsf@%'%@sxx@%%@mx@% values from GC/TOF-MS showed deviations from those obtained by GC/FID, resulting from sensitivity differences between the C37:2 and C37:3 alkenone when analyzed by GC/TOF-MS. A solution to this bias is presented by determining compound-specific linear response factor equations to derive sensitivity ratios (SR) that allow conversion of GC/TOF-MS values into calibrated GC/FID data. Using alkenone mixtures of known composition and a variety of samples from natural environments, the applicability of this approach is demonstrated. PMID:18288817

Hefter, J

2008-03-15

392

Analysis of phenolic acids as chloroformate derivatives using solid phase microextraction-gas chromatography.  

PubMed

In the presented study, a simple and original procedure of phenolic acids derivatization treated by ethyl and methyl chloroformate performed in an aqueous media consisting of acetonitrile, water, methanol/ethanol and pyridine has been modified and optimized. Seven phenolic acid standards-caffeic, ferulic, gallic, p-coumaric, protocatechuic, syringic and vanillic were derivatized into corresponding methyl/ethyl esters and subsequently determined by the means of gas chromatography connected to the flame-ionisation detector (FID). Some selected validation parameters as linearity, detection and quantitation limits and peak area repeatability were valued. The total time of gas chromatography (GC) analysis was 24 min for methyl chloroformate and 30 min for ethyl chloroformate derivatization. The more suitable methyl chloroformate derivatization was used for further experiments on the possibility of multiple pre-concentration by the direct solid phase microextraction technique (SPME). For this purpose, polyacrylate (PA), polydimethylsiloxane (PDMS), carboxen/polydimethylsiloxane (CAR/PDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibres were tested and the extraction conditions concerning time of extraction, temperature and time of desorption were optimized. The most polar PA fibre gave the best results under optimal extraction conditions (50 min extraction time, 25 degrees C extraction temperature and 10 min desorption time). As a result, the total time of SPME-GC analysis was 74 min and an increase in method sensitivity was reached. The limits of quantitation (LOQ) of p-coumaric, ferulic, syringic and vanillic acid esters after SPME pre-concentration were 0.02, 0.17, 0.2 and 0.2 microg mL(-1), respectively, showing approximately 10 times higher sensitivity in comparison with the original GC method. PMID:17723529

Citová, Ivana; Sladkovský, Radek; Solich, Petr

2006-07-28

393

Differential Gas-Liquid Chromatographic Behaviour in Diastereoisomeric Systems. Part III. Symmetrically Substituted Dichiral Ethers, Alkoxysiloxanes, and Disiloxanes.  

National Technical Information Service (NTIS)

Gas-liquid chromatographic resolution of diastereomers containing an asymmetric silicon atom as alkoxysiloxane was studied and compared with that of similar compounds of the ether and of the disiloxane series. The resolution factors of some diastereomers ...

B. Feibush L. Spialter

1970-01-01

394

Quantitative analysis of major plant hormones in crude plant extracts by high-performance liquid chromatography–mass spectrometry  

Microsoft Academic Search

The ability to measure plant hormones quantitatively is important as plant hormones regulate plant growth, development and response to biotic and abiotic cues. In this protocol, we describe the quantitative analysis of major plant hormones from crude plant extracts. Plant hormones are determined using reverse-phase liquid chromatography–tandem mass spectrometry with multiple reaction monitoring. The method provides quantification of most major

Ruth Welti; Xuemin Wang; Xiangqing Pan

2010-01-01

395

ANALYSIS OF TRACE-LEVEL ORGANIC COMBUSTION PROCESS EMISSIONS USING NOVEL MULTIDIMENSIONAL GAS CHROMATOGRAPHY-MASS SPECTROMETRY PROCEDURES  

EPA Science Inventory

The paper discusses the analysis of trace-level organic combustion process emissions using novel multidimensional gas chromatography-mass spectrometry (MDGC-MS) procedures. It outlines the application of the technique through the analyses of various incinerator effluent and produ...

396

RAPID ANALYSIS OF CYANURIC ACID IN SWIMMING POOL WATERS BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY USING POROUS GRAPHITIC CARBON  

EPA Science Inventory

An innovative approach is presented for reducing analysis times of cynuric acid in swimming pool waters by high performance liquid chromatography (HPLC). The HPLC method exploits the unique selectivity of porous graphitic carbon (PGC) to fully resolve within 10 minutes cyanuric ...

397

A Laboratory Experiment in Pharmaceutical Analysis: Determination of Drugs of Abuse in Human Urine by Thin-Layer Chromatography.  

ERIC Educational Resources Information Center

An experiment is described that was developed for a course in Inorganic and Analytical Pharmaceutical Chemistry at Rutgers University to provide pharmacy students with practical experience in the thin-layer chromatography used for the analysis of urine to monitor patient compliance with drug abuse treatment programs. (JMD)

Bailey, Leonard C.

1979-01-01

398

RAPID ANALYSIS OF CYNANURIC ACID IN SWIMMING POOL WATERS BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY USING POROUS GRAPHITIC CARBON COLUMN  

EPA Science Inventory

An innovative approach is presented for reducing analysis times of cyanuric acid in swimming pool waters by high performance liquid chromatography (HPLC). The HPLC method exploits the unique selectivity of porous graphitic carbon (PGC) to fully resolve cyanuric acid from other p...

399

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...

400

ISOTOPE DILUTION ANALYSIS OF BROMATE IN DRINKING WATER MATRIXES BY ION CHROMATOGRAPHY WITH INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRIC DETECTION  

EPA Science Inventory

Bromate is a disinfection byproduct in drinking water which is formed during the ozonation of source water containing bromide. This paper described the analysis of bromate via ion chromatography-inductively coupled plasma mass spectrometry. The separation of bromate from interfer...

401

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

402

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

403

Arsenic and its speciation analysis using high-performance liquid chromatography and inductively coupled plasma mass spectrometry  

Microsoft Academic Search

It is known that arsenic has different toxicological properties dependent upon both its oxidation state for inorganic compounds, as well as the different toxicity levels exhibited for organic arsenic compounds. The field of arsenic speciation analysis has grown rapidly in recent years, especially with the utilization of high-performance liquid chromatography (HPLC) coupled to inductively coupled plasma mass spectrometry (ICP-MS), a

C B’Hymer; J. A Caruso

2004-01-01

404

Gas–liquid interfacial mass transfer in trickle-bed reactors: state-of-the-art correlations  

Microsoft Academic Search

The state-of-the-art of the gas-liquid mass transfer characteristics in trickle-bed reactors was summarized and its quantification methods were reevaluated based on a wide-ranging data base of some 3200 measurements. A set of three unified whole-flow-regime dimensionless correlations for volumetric liquid- and gas-side mass transfer coefficients, and gas–liquid interfacial area, each of which spanned four-order-of-magnitude intervals, were derived. The correlations involved

Ion Iliuta; Bernard P. A. Grandjean; Gabriel Wild

1999-01-01

405

Study of interfacial behavior in concurrent gas-liquid flows: Progress report, 1 May 1988--30 April 1989  

Microsoft Academic Search

This research is focused on acquiring an understanding of the fundamental processes which occur within the liquid layer of separated (i.e., annular or stratified) gas-liquid flows. Knowledge of this behavior is essential for interpretation of pressure drops, entrainment fraction, transport processes and possibly flow regime transitions in gas-liquid flows. We are examining the qualitative and quantitative nature of the interface,

McCready

1989-01-01

406

Enhancing concentration and mass sensitivities for liquid chromatography trace analysis of clopyralid in drinking water.  

PubMed

A theoretical treatment was developed and validated that relates analyte concentration and mass sensitivities to injection volume, retention factor, particle diameter, column length, column inner diameter and detection wavelength in liquid chromatography, and sample volume and extracted volume in solid-phase extraction (SPE). The principles were applied to improve sensitivity for trace analysis of clopyralid in drinking water. It was demonstrated that a concentration limit of detection of 0.02?ppb (?g/L) for clopyralid could be achieved with the use of simple UV detection and 100?mL of a spiked drinking water sample. This enabled reliable quantitation of clopyralid at the targeted 0.1?ppb level. Using a buffered solution as the elution solvent (potassium acetate buffer, pH 4.5, containing 10% of methanol) in the SPE procedures was found superior to using 100% methanol, as it provided better extraction recovery (70-90%) and precision (5% for a concentration at 0.1?ppb level). In addition, the eluted sample was in a weaker solvent than the mobile phase, permitting the direct injection of the extracted sample, which enabled a faster cycle time of the overall analysis. Excluding the preparation of calibration standards, the analysis of a single sample, including acidification, extraction, elution and LC run, could be completed in 1?h. The method was used successfully for the determination of clopyralid in over 200 clopyralid monoethanolamine-fortified drinking water samples, which were treated with various water treatment resins. PMID:22180193

Gu, Binghe; Meldrum, Brian; McCabe, Terry; Phillips, Scott

2011-12-19

407

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

408

Native fluorescent detection with sequential injection chromatography for doping control analysis  

PubMed Central

Background Sequential injection chromatography (SIC) is a young, ten years old, separation technique. It was proposed with the benefits of reagent-saving, rapid analysis, system miniaturization and simplicity. SIC with UV detection has proven to be efficient mostly for pharmaceutical analysis. In the current study, a stand-alone multi-wavelength fluorescence (FL) detector was coupled to an SIC system. The hyphenation was exploited for developing an SIC-FL method for the separation and quantification of amiloride (AML) and furosemide (FSM) in human urine and tablet formulation. Results AML and FSM were detected using excitation maxima at 380 and 270 nm, respectively, and emission maxima at 413 and 470 nm, respectively. The separation was accomplished in less than 2.0 min into a C18 monolithic column (50?×?4.6 nm) with a mobile phase containing 25 mmol/L phosphate buffer (pH 4.0): acetonitrile: (35:65, v/v). The detection limits were found to be 12 and 470 ng/mL for AML and FSM, respectively. Conclusions The proposed SIC-FL method features satisfactory sensitivity for AML and FSM in urine samples for the minimum required performance limits recommended by the World Anti-Doping Agency, besides a downscaled consumption of reagents and high rapidity for industrial-scale analysis of pharmaceutical preparations.

2013-01-01

409

Quantitative analysis of tropane alkaloids in biological materials by gas chromatography-mass spectrometry.  

PubMed

A simple and rapid method for quantitation of tropane alkaloids in biological materials has been developed using an Extrelut column with gas chromatography-mass spectrometry (GC-MS). Biological materials (serum and urine) were mixed with a borate buffer and then applied to an Extrelut column. The adsorbed tropane alkaloids were eluted with dichloromethane before a GC-MS analysis. Atropine-d(3) was used as an internal standard. The extracted tropane alkaloids were converted to trimethylsilyl derivatives prior to GC analysis, to improve the instability of tropane alkaloids from heating and the property of them for a GC column. The recoveries of the compounds, which had been spiked to biological materials, were more than 80%. The GC separation of the derivatives from endogenous impurities was generally satisfactory with the use of a semi-polar capillary column. Tropane alkaloids showed excellent linearity in the range of 10-5000 ng/ml and the limit of detection was 5.0 ng/ml for biological materials. The present method is simple and more rapid than those previously reported, and was applied to a poisoning case. It is useful for the routine analysis of tropane alkaloids in cases of suspected tropane alkaloids poisoning. PMID:12427448

Namera, Akira; Yashiki, Mikio; Hirose, Yasuo; Yamaji, Seiichi; Tani, Tadato; Kojima, Tohru

2002-11-01

410

Analysis of antimicrobial agents in pig feed by liquid chromatography coupled to orbitrap mass spectrometry.  

PubMed

The emerging trend towards full scan mass spectrometry alternatives was evaluated for the identification of a wide range of anti-bacterial compounds in animal feed. The high resolving power of the orbitrap exactive provides precise mass accuracy, resulting in high selectivity which enables qualitative and quantitative analysis in complex matrices such as feed. A simple generic sample preparation procedure was applied, including extraction of the feed samples with a combination of organic solvents. The mass spectrometer was operated in full scan with polarity switching between positive and negative modes, using heated electrospray ionization (H-ESI). The detection was carried out using automatic control of the number of ions entering the mass analyzer and with the combination of the ion injection time, accurate quantitative analysis was achieved. Due to the complexity of the feed samples the resolving power proved to be the key for the discrimination between interfering masses from the matrix and the exact masses of the compounds in order to achieve mass accuracy of 5ppm. Furthermore, the use of narrow mass windows (±5ppm) improved the selectivity of the method, increasing the signal-to-noise ratio for the compounds. A thoroughly validation study was successfully performed and evaluated in pig feed. The utilization of liquid chromatography to the high resolution orbitrap exactive proved to be a powerful tool for routine analysis of undesirable anti-bacterial compounds in feed control, ensuring food safety under the EU food chain legal framework. PMID:23623364

George, Kaklamanos; Vincent, Ursula; von Holst, Christoph

2013-06-01

411

Matrix diversion methods for improved analysis of perchlorate by suppressed ion chromatography and conductivity detection.  

PubMed

Two inline matrix diversion methods were developed for the sensitive analysis of perchlorate in a matrix comprising up to 1000 mg l(-1) of chloride, sulfate and bicarbonate ions using suppressed ion chromatography and conductivity detection. The first method used a cryptand C1 concentrator column, which exhibited a high selectivity for perchlorate ion over the other matrix anions. After retaining the sample anions in a concentrator column derivatized with a crytpand phase, a rinse step was implemented with a weak base to divert the matrix ions to waste while selectively retaining perchlorate in the concentrator column for subsequent analysis. The analysis was done using a 2mm IonPac AS16 or 2 mm IonPac AS20 separator column. The second method was a two-dimensional matrix diversion method with a focus on improving the detection sensitivity. The first dimension was used to achieve some resolution of the matrix ions from perchlorate. The perchlorate ion was then diverted into a concentrator column for subsequent analysis in the second dimension. By pursuing analysis using a 4mm IonPac AS16 or IonPac AS20 column in the first dimension and subsequently pursuing analysis using a 2mm IonPac AS16 or IonPac AS20 column format, excellent sensitivities were achieved when the first and second dimensions were operated at the same linear flow velocity (cm min(-1)). While sensitive detection of perchlorate in the low microg l(-1) regime was achieved by the above methods in the presence of matrix ions, superior recovery for perchlorate was demonstrated under a variety of matrix concentrations by the second method. PMID:17723390

Lin, Rong; De Borba, Brian; Srinivasan, Kannan; Woodruff, Andy; Pohl, Chris

2006-05-10

412

Glycomic analysis by glycoprotein immobilization for glycan extraction and liquid chromatography on microfluidic chip.  

PubMed

Glycosylation is one of the most common protein modifications and profoundly regulates many biological processes. Aberrant glycosylation is reported to associate with diseases such as cancers, human immunodeficiency virus, and immune disorders. It is considerably important to study protein glycosylation and the associated glycans for diagnostics and disease prognostics. Unlike other protein modifications, glycans attached to proteins are enormously complex. Therefore, the comprehensive analysis of glycans from biological or clinical samples is an unmet technical challenge. Development of the high-throughput method will facilitate the glycomics analysis. In this study, we developed a novel method for the high-throughput analysis of N-glycans from glycoproteins using glycoprotein immobilization for glycan extraction (GIG) coupled with liquid chromatography (LC) in an integrated microfluidic platform (chipLC). The separated glycans were then analyzed by mass spectrometry. Briefly, proteins were first immobilized on a solid support. Glycans on immobilized glycoproteins were modified on solid phase to increase the detection and structure analysis. N-Glycans were then enzymatically released and subsequentially separated by porous graphitized carbon particles packed in the same device. By applying the GIG-chipLC for glycomic analysis of human sera, we identified N-glycans with 148 distinct N-glycan masses. The platform was used to analyze N-glycans from mouse heart tissue and serum. The extracted N-glycans from tissues indicated that unique unsialylated N-glycans were detected in tissues that were missing from the proximal or distal serum, whereas common N-glycans from tissues and serum have mature and sialylated structures. The GIG-chipLC provides a simple and robust platform for glycomic analysis of complex biological and clinical samples. PMID:24111616

Yang, Shuang; Toghi Eshghi, Shadi; Chiu, Hanching; DeVoe, Don L; Zhang, Hui

2013-11-01

413

Quantum state-resolved energy transfer dynamics at gas-liquid interfaces: IR laser studies of CO2 scattering from perfluorinated liquids.  

PubMed

An apparatus for detailed study of quantum state-resolved inelastic energy transfer dynamics at the gas-liquid interface is described. The approach relies on supersonic jet-cooled molecular beams impinging on a continuously renewable liquid surface in a vacuum and exploits sub-Doppler high-resolution laser absorption methods to probe rotational, vibrational, and translational distributions in the scattered flux. First results are presented for skimmed beams of jet-cooled CO(2) (T(beam) approximately 15 K) colliding at normal incidence with a liquid perfluoropolyether (PFPE) surface at E(inc) = 10.6(8) kcal/mol. The experiment uses a tunable Pb-salt diode laser for direct absorption on the CO(2) nu(3) asymmetric stretch. Measured rotational distributions in both 00(0)0 and 01(1)0 vibrational manifolds indicate CO(2) inelastically scatters from the liquid surface into a clearly non-Boltzmann distribution, revealing nonequilibrium dynamics with average rotational energies in excess of the liquid (T(s) = 300 K). Furthermore, high-resolution analysis of the absorption profiles reveals that Doppler widths correspond to temperatures significantly warmer than T(s) and increase systematically with the J rotational state. These rotational and translational distributions are consistent with two distinct gas-liquid collision pathways: (i) a T approximately 300 K component due to trapping-desorption (TD) and (ii) a much hotter distribution (T approximately 750 K) due to "prompt" impulsive scattering (IS) from the gas-liquid interface. By way of contrast, vibrational populations in the CO(2) bending mode are inefficiently excited by scattering from the liquid, presumably reflecting much slower T-V collisional energy transfer rates. PMID:16853084

Perkins, Bradford G; Häber, Thomas; Nesbitt, David J

2005-09-01

414

The analysis of carbohydrates in milk powder by a new "heart-cutting" two-dimensional liquid chromatography method.  

PubMed

In this study, a new"heart-cutting" two-dimensional liquid chromatography method for the simultaneous determination of carbohydrate contents in milk powder was presented. In this two dimensional liquid chromatography system, a Venusil XBP-C4 analysis column was used in the first dimension ((1)D) as a pre-separation column, a ZORBAX carbohydrates analysis column was used in the second dimension ((2)D) as a final-analysis column. The whole process was completed in less than 35min without a particular sample preparation procedure. The capability of the new two dimensional HPLC method was demonstrated in the determination of carbohydrates in various brands of milk powder samples. A conventional one dimensional chromatography method was also proposed. The two proposed methods were both validated in terms of linearity, limits of detection, accuracy and precision. The comparison between the results obtained with the two methods showed that the new and completely automated two dimensional liquid chromatography method is more suitable for milk powder sample because of its online cleanup effect involved. PMID:24412698

Ma, Jing; Hou, Xiaofang; Zhang, Bing; Wang, Yunan; He, Langchong

2014-03-01

415

Rapid liquid chromatography for paralytic shellfish toxin analysis using superficially porous chromatography with AOAC Official Method 2005.06.  

PubMed

The bioaccumulation of paralytic shellfish toxins in mussels, oysters, cockles, hard clams, razors, and king scallops is monitored in England, Scotland, and Wales by AOAC Official Method 2005.06 LC-with fluorescence detection (FLD). One of the commonly perceived disadvantages of using this method is the long turnaround time and low throughput in a busy laboratory environment. The chromatographic analysis of each sample typically utilizes a 15 min cycle time to achieve toxin oxidation product separation and column equilibration prior to subsequent analysis. A standard RP C18 analytical column, used successfully in recent years, achieves good separation with a long column lifetime. The analysis of a 40 sample qualitative screening batch takes approximately 18 h, including blanks, standards, and other QC samples. The availability of superficially porous column technology has offered the potential to reduce analysis time while retaining column performance on existing hardware. In this study, AOAC Official Method 2005.06 with LC-FLD was transferred to two different commercially available superficially porous columns, and the method performance characteristics were evaluated. Both columns separated all toxins adequately with cycle times less than half that of the existing method. Linearity for each toxin was acceptable up to two times the European maximum permitted limit of 800 microg di-HCl saxitoxin equivalent/kg flesh. LOD and LOQ values were substantially improved for the majority of toxins, with gonyautoxin 1&4 and neosaxitoxin showing up to a two- and fourfold improvement, respectively, depending on the column used. Quantification results obtained from parallel analysis of contaminated samples were acceptable on both columns. Comparative screen results gave a slight increase in the occurrence of contaminated samples, which was attributed to the improved detection limit for most toxins. Issues with rapidly increasing back pressure, however, were identified with both columns, with a limit of around 500 injections. This compares to the >3000 cycles routinely obtained with the standard RP-C18 HPLC columns currently in use. Overall, the gain achieved with these columns through shorter analysis time and improved analytical sensitivity is potentially of benefit in a high-throughput environment. For the routine high-throughput screening of shellfish samples, however, an improved column lifetime is desirable. PMID:22970577

Hatfield, Robert G; Turner, Andrew D

2012-01-01

416

Gas Chromatography\\/Fourier Transform Infrared Spectroscopy Applications  

Microsoft Academic Search

The past few years have seen a marked increase in interest in the use of combined gas-liquid chromatography and infrared spectroscopy (GC\\/IR). This increase in interest is primarily due to the advent of Fourier transform infrared spectroscopy (FTIR). The combination. GC\\/FTIR. provides the sensitivity and scanning speed which have hindered the wide applicability of GC\\/IR using dispersive instruments.

M. D. Erickson

1979-01-01

417

Gas chromatography/mass spectrometry versus liquid chromatography/fluorescence detection in the analysis of phenols in mainstream cigarette smoke.  

PubMed

A new gas chromatographic/mass spectrometric (GC/MS) technique for the analysis of hydroxybenzenes (phenols) in mainstream cigarette smoke has been developed. The technique allows the measurement of 24 individual compounds, and the sum of a few other alkyl-dihydroxybenzenes. A critical evaluation is done for the new technique and for an established high-performance liquid chromatographic (HPLC) technique reported in the literature for the analysis of hydroxybenzenes in cigarette smoke, which uses fluorescence detection. Compared with the HPLC procedure, the new technique has similar accuracy, precision, and robustness. However, the GC/MS procedure allows for a larger number of phenols to be analyzed simultaneously, and eliminates any potential interference that may appear in the HPLC method. Using the GC/MS analysis, it was found that besides the main phenols typically measured in mainstream cigarette smoke such as phenol, catechol, hydroquinone, and cresols, many other phenols that are present at lower levels can be quantitated in mainstream cigarette smoke. PMID:17182049

Moldoveanu, Serban C; Kiser, Melissa

2007-02-01

418

Formation of iron complexs from trifluoroacetic acid based liquid chromatography mobile phases as interference ions in liquid chromatography/electrospray ionization mass spectrometric analysis  

SciTech Connect

Two unexpected singly charged ions at m/z 1103 and 944 have been observed in mass spectra obtained from electrospray ionization-mass spectrometric analysis of liquid chromatography effluents with mobile phases containing trifluoroacetic acid. Accurate mass measurement and tandem mass spectrometry studies revealed that these two ions are not due to any contamination from solvents and chemicals used for mobile and stationary phases or from the laboratory atmospheric environment. Instead these ions are clusters of trifluoroacetic acid formed in association with acetonitrile, water and iron from the stainless steel union used to connect the column with the electrospray tip and to apply high voltage; the molecular formulae are Fe+((OH)(H2O)2)9(CF3COOH)5 and Fe+((OH)(H2O)2)6 (CF3COOH)5.

Shukla, Anil K.; Zhang, Rui; Orton, Daniel J.; Zhao, Rui; Clauss, Therese RW; Moore, Ronald J.; Smith, Richard D.

2011-05-30

419

Gas Chromatography  

NASA Astrophysics Data System (ADS)

Gas chromatography (GC) has many applications in the analysis of food products. GC has been used for the determination of fatty acids, triglycerides, cholesterol, gases, water, alcohols, pesticides, flavor compounds, and many more. While GC has been used for other food components such as sugars, oligosaccharides, amino acids, peptides, and vitamins, these substances are more suited to analysis by high performance liquid chromatography. GC is ideally suited to the analysis of volatile substances that are thermally stable. Substances such as pesticides and flavor compounds that meet these criteria can be isolated from a food and directly injected into the GC. For compounds that are thermally unstable, too low in volatility, or yield poor chromatographic separation due to polarity, a derivatization step must be done before GC analysis. The two parts of the experiment described here include the analysis of alcohols that requires no derivatization step, and the analysis of fatty acids which requires derivatization. The experiments specify the use of capillary columns, but the first experiment includes conditions for a packed column.

Qian, Michael C.

420

Analysis of psilocybin and psilocin in Psilocybe subcubensis GUZMÁN by ion mobility spectrometry and gas chromatography–mass spectrometry  

Microsoft Academic Search

A new method has been developed for the rapid analysis of psilocybin and\\/or psilocin in fungus material using ion mobility spectrometry. Quantitative analysis was performed by gas chromatography–mass spectrometry after a simple one-step extraction involving homogenization of the dried fruit bodies of fungi in chloroform and derivatization with MSTFA. The proposed methods resulted in rapid procedures useful in analyzing psychotropic

Thomas Keller; Andrea Schneider; Priska Regenscheit; Richard Dirnhofer; Thomas Rücker; Jürgen Jaspers; Wolfgang Kisser

1999-01-01

421

Enantiomeric analysis of (+)-menthol and (-)-menthol by fluorogenic derivatization and liquid chromatography.  

PubMed

A simple and sensitive liquid chromatography is described for the quantitative analysis of enantiomeric (+)-menthol and (-)-menthol that are lack of chromophore. The method is based on the derivatization of (+)-menthol and (-)-menthol with a fluorescent reagent, naproxen acyl chloride, in toluene. The resulting diastereomic derivatives were separated on a C8 column with methanol-water-tetrahydrofuran (80:18:2, v/v) as a mobile phase; they were sensitively monitored with a fluorimetric detector (excitation 235 nm and emission 350 nm). The linear range for the quantitation of the enantiomers was 5.0-50 microM with a detection limit (signal to noise ratio = 3, injected volume 10 microl) of about 1 microM. Application of the method to the enantiomeric analysis of menthol in mint plants proved simple and feasible. Toluene was used for the extraction of menthol from the leaves of mint, and the resulting toluene extract was directly used for subsequent derivatization without solvent replacement. PMID:16130717

Lin, Yu-Ting; Wu, Hsing-Lung; Kou, Hwang-Shang; Wu, Shou-Mei; Chen, Su-Hwei

2005-09-16

422

Morphological, spectral and chromatography analysis and forensic comparison of PET fibers.  

PubMed

Poly(ethylene terephthalate) (PET) fiber analysis and comparison by spectral and polymer molecular weight determination was investigated. Plain fibers of PET, a common textile fiber and plastic material was chosen for this study. The fibers were analyzed for morphological (SEM and AFM), spectral (IR and NMR), thermal (DSC) and molecular weight (MS and GPC) differences. Molecular analysis of PET fibers by Gel Permeation Chromatography (GPC) allowed the comparison of fibers that could not be otherwise distinguished with high confidence. Plain PET fibers were dissolved in hexafluoroisopropanol (HFIP) and analyzed by GPC using hexafluoroisopropanol:chloroform 2:98 v/v as eluent. 14 PET fiber samples, collected from various commercial producers, were analyzed for polymer molecular weight by GPC. Distinct differences in the molecular weight of the different fiber samples were found which may have potential use in forensic fiber comparison. PET fibers with average molecular weights between about 20,000 and 70,000 g mol(-1) were determined using fiber concentrations in HFIP as low as 1 ?g mL(-1). This GPC analytical method can be applied for exclusively distinguish between PET fibers using 1 ?g of fiber. This method can be extended to forensic comparison of other synthetic fibers such as polyamides and acrylics. PMID:24725864

Farah, Shady; Tsach, Tsadok; Bentolila, Alfonso; Domb, Abraham J

2014-06-01

423

Monosaccharide composition analysis of oligosaccharides and glycoproteins by high-performance liquid chromatography.  

PubMed

A simple and sensitive high-performance liquid chromatography (HPLC)-based method for complete monosaccharide composition analysis of oligosaccharides and glycoproteins is described. In this method, an oligosaccharide or glycoprotein is first hydrolyzed using an optimized method to give the constituent monosaccharides, which are subsequently labeled with 1-phenyl-3-methyl-5-pyrazolone (PMP) as previously described by Honda et al. (Anal, Biochem. 180, 351-357, (1989)). The labeled monosaccharides are separated by reverse-phase HPLC using a column developed especially for this purpose, monitored by uv absorbance at 245 nm, and quantitated by their integration values relative to standards. Sialic acids are acid-labile keto-sugars. They are, therefore, released with neuraminidases or by mild acid hydrolysis and then converted with neuraminic acid aldolase to their corresponding mannosamine derivatives, which are then PMP-labeled, separated, and quantitated as described above. Individual sialic acids including N-acetyl and N-glycolyl neuraminic acids are well resolved and quantitated by this method. This method has proven to be highly sensitive, requiring only 1 pmol for reliable detection. Quantitative analysis of neutral and amino sugars from both oligosaccharide and glycoprotein samples can be achieved using one acid hydrolysis and a set of equal molar monosaccharide standards. Similarly, quantitation of sialic acids works equally well with both free oligosaccharide and glycoprotein samples. Monosaccharide compositions of oligosaccharides and glycoproteins determined by this method were found to be highly accurate. PMID:7573960

Fu, D; O'Neill, R A

1995-05-20

424

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

2009-03-01

425

Simultaneous quantitative analysis of metabolites using ion-pair liquid chromatography-electrospray ionization mass spectrometry.  

PubMed

We have developed an analytical method, consisting of ion-pair liquid chromatography coupled to electrospray ionization mass spectrometry (IP-LC-ESI-MS), for the simultaneous quantitative analysis of several key classes of polar metabolites, like nucleotides, coenzyme A esters, sugar nucleotides, and sugar bisphosphates. The use of the ion-pair agent hexylamine and optimization of the pH of the mobile phases were critical parameters in obtaining good retention and peak shapes of many of the above-mentioned polar and acidic metabolites that are impossible to analyze using standard reversed-phase LC/MS. Optimum conditions were found when using a gradient from 5 mM hexylamine in water (pH 6.3) to 90% methanol/10% 10 mM ammonium acetate (pH 8.5). The IP-LC-ESI-MS method was extensively validated by determining the linearity (R2 > 0.995), sensitivity (limit of detection 0.1-1 ng), repeatability, and reproducibility (relative standard deviation <10%). The IP-LC-ESI-MS method was shown to be a useful tool for microbial metabolomics, i.e., the comprehensive quantitative analysis of metabolites in extracts of microorganisms, and for the determination of the energy charge, i.e., the cellular energy status, as an overall quality measure for the sample workup and analytical protocols. PMID:16970336

Coulier, Leon; Bas, Richard; Jespersen, Sonja; Verheij, Elwin; van der Werf, Mariët J; Hankemeier, Thomas

2006-09-15

426

Enantiomeric analysis of amino acids by using comprehensive two-dimensional gas chromatography.  

PubMed

The chiral separation of amino acids (AA) derivatised with ethyl chloroformate by using comprehensive two-dimensional gas chromatography is reported. A commercially available enantioselective capillary column (Chirasil-l-Val) has been tested as first-dimension column. Two nonenantioselective stationary phases (BPX50 and BP1) with different column lengths were combined with the enantioselective column, which represent chiral/polar and chiral/low-polarity column sets, respectively. These column sets were evaluated to determine the most useful column combination to provide improved separation efficiency of enantioselective AA analysis. Separations of AA mixtures derivatised either as their N-trifluoroacetyl methyl esters or with methyl chloroformate, performed on a chiral/low-polarity column set, are also shown. The method was demonstrated for chiral analysis of AAs in different beer samples. The major AA in the beer samples was proline with amounts ranging from around 65-95% with minor contents of glycine and the l-enantiomers of alanine, valine, leucine, and isoleucine. Small amounts of d-alanine, at about 1, 1.5, and 15% were detected in the three samples. PMID:17230499

Junge, Melanie; Huegel, Helmut; Marriott, Philip J

2007-03-01

427

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

2013-02-01

428

Depletion of highly abundant proteins in blood plasma by hydrophobic interaction chromatography for proteomic analysis.  

PubMed

The proteomic analysis of plasma is extremely complex due to the presence of few highly abundant proteins. These proteins have to be depleted in order to detect low abundance proteins, which are likely to be of biomedical interest. In this work it was investigated the applicability of hydrophobic interaction chromatography (HIC) as a plasma fractionation method prior to two-dimensional gel electrophoresis (2DGE). The average hydrophobicity of the 56 main plasma proteins was calculated. Plasma proteins were classified as low, medium and highly hydrophobic through a cluster analysis. The highly abundant proteins showed a medium hydrophobicity, and therefore a HIC step was designed to deplete them from plasma. HIC performance was assessed by 2DGE, and it was compared to that obtained by a commercial immuno-affinity (IA) column for albumin depletion. Both methods showed similar reproducibility. HIC allowed partially depleting alpha-1-antitrypsin and albumin, and permitted to detect twice the number of spots than IA. Since albumin depletion by HIC was incomplete, it should be further optimized for its use as a complementary or alternative method to IA. PMID:20356804

Mahn, Andrea; Reyes, Alejandro; Zamorano, Mauricio; Cifuentes, Wildo; Ismail, Maritza

2010-05-01

429

In situ Analysis of Organic Compounds on Mars using Chemical Derivatization and Gas Chromatography Mass Spectrometry  

NASA Technical Reports Server (NTRS)

One of the core science objectives of NASA's 2009 Mars Science Laboratory (MSL) mission is to determine the past or present habitability of Mars. The search for key organic compounds relevant to terrestrial life will be an important part of that assessment. We have developed a protocol for the analysis of amino acids and carboxylic acids in Mars analogue materials using gas chromatography mass spectrometry (GCMS). As shown, a variety of carboxylic acids were readily identified in soil collected from the Atacama Desert in Chile at part-per-billion levels by GCMS after extraction and chemical derivatization using the reagent N,N-tert.-butyl (dimethylsilyl) trifluoroacetamide (MTBSTFA). Several derivatized amino acids including glycine and alanine were also detected by GCMS in the Atacama soil at lower concentrations (chromatogram not shown). Lacking derivatization capability, the Viking pyrolysis GCMS instruments could not have detected amino acids and carboxylic acids, since these non-volatile compounds require chemical transformation into volatile species that are stable in a GC column. We are currently optimizing the chemical extraction and derivatization technique for in situ GCMS analysis on Mars. Laboratory results of analyses of Atacama Desert samples and other Mars analogue materials using this protocol will be presented.

Glavin, D. P.; Buch, A.; Cabane, M.; Coll, P.; Navarro-Gonzalez, R.; Mahaffy, P. R.

2005-01-01

430

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

431

Fast analysis of wine for total homocysteine content by high-performance liquid chromatography.  

PubMed

Alimentary methionine is believed to be the main source for plasma homocysteine. Recent literature supplies information about homocysteine content in daily food components, but not in wine, an attractive complement of the evening meal in some western countries. In this communication, a simple and fast high-performance liquid chromatography method for determination of total homocysteine in wine is described. The two steps procedure relies on reduction of the disulfide forms of homocysteine with tris-(2-carboxyethyl)phosphine and on-column derivatization with o-phthaldialdehyde followed by separation and fluorescence detection. The entire analysis time, including sample work-up, amounts 14 min. The calibration performed with wine matrix, spiked with homocystine within the practical concentration range, proved linear response of the detector. The proposed method was applied for the analysis of 32 different types of wines for total homocysteine. The average concentration of the analyte was 10.31 (±4.25) µM and 6.11 (±3.44) µM for red (n = 23) and white (n = 9) wines, respectively. PMID:22209913

G?owacki, Rafa?; Borowczyk, Kamila; Bald, Edward

2012-01-01

432

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 3.5 cm 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 (~25 s) 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

2013-10-01

433

Analysis of the Glycoproteome of Toxoplasma gondii using Lectin Affinity Chromatography and Tandem Mass Spectrometry  

PubMed Central

Glycoproteins are involved in many important molecular recognition processes including invasion, adhesion, differentiation, and development. To identify the glycoproteins of Toxoplasma gondii, a proteomic analysis was undertaken. T. gondii proteins were prepared and fractioned using lectin affinity chromatography. The proteins in each fraction were then separated using SDS-PAGE and identified by tryptic in gel digestion followed by tandem mass spectrometry. Utilizing these methods 132 proteins were identified. Among the identified proteins were 17 surface proteins, 9 microneme proteins, 15 rhoptry proteins, 11 heat shock proteins (HSP), and 32 hypothetical proteins. Several proteins had 1 to 5 transmembrane domains (TMD) with some being as large as 608.3 kDa. Both lectin-fluorescence labeling and lectin blotting were employed to confirm the presence of carbohydrates on the surface or cytoplasm of T. gondii parasites. PCR demonstrated that selected hypothetical proteins were expressed in T. gondii tachyzoites. This is data provides a large scale analysis of the T. gondii glycoproteome. Studies of the function of glycosylation of these proteins may help elucidate mechanism(s) involved in invasion improving drug therapy as well as identify glycoproteins that may prove to be useful as vaccine candidates.

Luo, Qilie; Upadhya, Rajendra; Zhang, Hong; Madrid-Aliste, Carlos; Nieves, Edward; Kim, Kami; Angeletti, Ruth Hogue; Weiss, Louis M.

2011-01-01

434

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

2008-02-01

435

On-line analysis of complex hydrocarbon mixtures using comprehensive two-dimensional gas chromatography.  

PubMed

This paper discusses the first setup for on-line qualitative and quantitative comprehensive two-dimensional gas chromatography (GC × GC) of complex hydrocarbon mixtures. A built-in 4-port 2-way valve allows switching between flame ionization detection (FID) and time-of-flight mass spectrometry (TOF-MS) between runs, without the need to cool down and vent the MS. Proper selection of GC carrier gas flow rates enables maximal agreement between the obtained chromatograms in both configurations. For on-line analysis of reactor effluents, a dedicated sampling system allows automatic sampling of the hot reactor effluent gases and immediate injection of the sample on the GC × GC. To determine a complete effluent composition in a single run of the GC × GC, a subzero oven starting temperature was employed. Modulation is started when the oven temperature reaches 40°C, thus dividing the chromatogram in a conventional 1D and a comprehensive 2D part. This work illustrates the mature and robust character of GC × GC, extending its capabilities from mere laboratory use to on-line routine analysis for industrial processes in the (petro-)chemical industry. PMID:20444456

Van Geem, Kevin M; Pyl, Steven P; Reyniers, Marie-Françoise; Vercammen, Joeri; Beens, Jan; Marin, Guy B

2010-10-22

436

Surface-sampling and analysis of TATP by swabbing and gas chromatography/mass spectrometry.  

PubMed

The method of sample recovery for trace detection and identification of explosives plays a critical role in several criminal investigations. After bombing, there can be difficulties in sending big objects to a laboratory for analysis. Traces can also be searched for on large surfaces, on hands of suspects or on surfaces where the explosive was placed during preparatory phases (e.g. places where an IED was assembled, vehicles used for transportation, etc.). In this work, triacetone triperoxide (TATP) was synthesized from commercial precursors following reported methods. Several portions of about 6mg of TATP were then spread on different surfaces (e.g. floors, tables, etc.) or used in handling tests. Three different swabbing systems were used: a commercial swab, pre-wetted with propan-2-ol (isopropanol) and water (7:3), dry paper swabs, and cotton swabs wetted with propan-2-ol. Paper and commercial swabs were also used to sample a metal plate, where a small charge of about 4g of TATP was detonated. Swabs were sealed in small glass jars with screw caps and Parafilm(®) M and sent to the laboratory for analysis. Swabs were extracted and analysed several weeks later by gas chromatography/mass spectrometry. All the three systems gave positive results, but wetted swabs collected higher amounts of TATP. The developed procedure showed its suitability for use in real cases, allowing TATP detection in several simulations, including a situation in which people wash their hands after handling the explosive. PMID:23219697

Romolo, Francesco Saverio; Cassioli, Luigi; Grossi, Silvana; Cinelli, Giuseppe; Russo, Mario Vincenzo

2013-01-10

437

Separation of crude palm oil components by semipreparative supercritical fluid chromatography  

Microsoft Academic Search

Successful separation of triglycerides, diglycerides, free fatty acids, carotenes, tocopherol, and tocotrienols from crude\\u000a palm oil has been achieved by supercritical fluid chromatography (SFC) with a combination of a C18 and a silica gel column.\\u000a The separation was carried out by the programmed extraction elution method. Free fatty acids were separated into five components\\u000a by gas-liquid chromatography; tocopherol and tocotrienols

Yuen May Choo; Ah Ngan Ma; Hawari Yahaya; Y. Yamauchi; M. Bounoshita; M. Saito

1996-01-01

438

/Chromatography+RECOVERY=superresolution chromatography  

NASA Astrophysics Data System (ADS)

A method for improving the resolution of the chromatographic analysis based on deriving the point-spread function of a chromatographic column, i.e., a chromatogram of an individual compound, is described. The system of two data sets, namely, a chromatogram of a substance analyzed and a point-spread function of a chromatographic column in combination with the noise statistics, makes it possible to use the RECOVERY signal-reconstruction software package described in paper by Gelfgat et al. (Comp. Phys. Commun. 74 (1993) 335). The proposed method has been tested by chromatography of bovine serum albumin using gel filtration. The resultant resolution exceeds that reached using high-performance liquid chromatography (with the cost of the instruments being lower by a factor of 15-20).

Kosarev, E. L.; Muranov, K. O.

2003-04-01

439

Contribution to complex gas-liquid flows: Development and validation of a mathematical model  

NASA Astrophysics Data System (ADS)

This study describes the development and validation of Computational Fluid Dynamics (CFD) model for the simulation of dispersed two-phase flows taking in the account the population balance of particles size distribution. A two-fluid (Euler-Euler) methodology previously developed for complex flows is adapted to the present project. The continuous phase turbulence is represented using a two-equation k --- epsilon turbulence model which contains additional terms to account for the effects of the dispersed on the continuous phase turbulence and the effects of the gas-liquid interface. The inter-phase momentum transfer is determined from the instantaneous forces acting on the dispersed phase, comprising drag, lift, virtual mass and drift velocity. These forces are phase fraction dependent and in this work revised modelling is put forward in order to capture a good accuracy for gas hold-up, liquid velocity profiles and turbulence parameters. Furthermore, a correlation for the effect of the drift velocity on the turbulence behaviour is proposed. The revised modelling is based on an extensive survey of the existing literature. The conservation equations are discretised using the finite-volume method and solved in a solution procedure, which is loosely based on the PISO algorithm. Special techniques are employed to ensure the stability of the procedure when the phase fraction is high or changing rapidely [61]. Finally, assessment of the model is made with reference to experimental data for gas-liquid bubbly flow in a rectangular bubble column [133; 134; 135; 18], in a double-turbine stirred tank reactor [126; 127] and in an air-lift bioreacator [101]. Key words: mathematical modelling, complex flow gas-liquid, turbulence, population balance, computational fluids dynamics CFD, OpenFOAM, moments method, method of classes, QMOM, DQMOM.

Selma, Brahim

440

Numerical simulations of gas-liquid flow in the gas injection process with mechanical stirring  

NASA Astrophysics Data System (ADS)

Based on Euler-Euler approach, a mathematical model is established to describe gas and liquid two-phase flow in a gas injected mechanically stirred system used in hot metal desulfurization process. The influences of different impellers types and rotation methods were investigated. The results show that the predicted distribution of bubbles in the bath agrees well with experimental results. The gas-liquid flow in the gas injected-mechanically stirred system can be accurately described by the present model. Compared to the standard impeller, the improved impeller in forward stirring mode is more efficient to increase the retention time and dispersion of bubbles.

Shao, Pin; Zhang, Ting'an; Liu, Yan; Zhang, Zimu; Wang, Dongxing

2013-06-01

441

Electrical impedance imaging in two-phase, gas-liquid flows: 1. Initial investigation  

NASA Technical Reports Server (NTRS)

The determination of interfacial area density in two-phase, gas-liquid flows is one of the major elements impeding significant development of predictive tools based on the two-fluid model. Currently, these models require coupling of liquid and vapor at interfaces using constitutive equations which do not exist in any but the most rudimentary form. Work described herein represents the first step towards the development of Electrical Impedance Computed Tomography (EICT) for nonintrusive determination of interfacial structure and evolution in such flows.

Lin, J. T.; Ovacik, L.; Jones, O. C.

1991-01-01

442

Gas-liquid transition in the model of particles interacting at high energy  

NASA Astrophysics Data System (ADS)

An application of the ideas of the inertial confinement fusion process in the case of particles interacting at high energy is investigated. A possibility of the gas-liquid transition in the gas is considered using different approaches. In particular, a shock wave description of interactions between particles is studied and a self-similar solution of Euler's equation is discussed. Additionally, the Boltzmann equation is solved for a self-consistent field (Vlasov's equation) in the linear approximation for the case of a gas under external pressure and the corresponding change of the Knudsen number of the system is calculated.

Bondarenko, S.; Komoshvili, K.

2013-11-01

443

Ground Based Studies of Gas-Liquid Flows in Microgravity Using Learjet Trajectories  

NASA Technical Reports Server (NTRS)

A 1.27 cm diameter two phase gas-liquid flow experiment has been developed with the NASA Lewis Research Center to study two-phase flows in microgravity. The experiment allows for the measurement of void fraction, pressure drop, film thickness and bubble and wave velocities as well as for high speed photography. Three liquids were used to study the effects of liquid viscosity and surface tension, and flow pattern maps are presented for each. The experimental results are used to develop mechanistically based models to predict void fraction, bubble velocity, pressure drop and flow pattern transitions in microgravity.

Bousman, W. S.; Dukler, A. E.

1994-01-01

444

Functional speciation of metal-dissolved organic matter complexes by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry and deconvolution analysis  

Microsoft Academic Search

High performance size exclusion chromatography coupled to inductively coupled plasma mass spectrometry (HP-SEC–ICP-MS), in combination with deconvolution analysis, has been used to obtain multielemental qualitative and quantitative information about the distributions of metal complexes with different forms of natural dissolved organic matter (DOM). High performance size exclusion chromatography coupled to inductively coupled plasma mass spectrometry chromatograms only provide continuous distributions

Francisco Laborda; Sergio Ruiz-Beguería; Eduardo Bolea; Juan R. Castillo

2009-01-01

445

Analysis of endocrine disrupters and related compounds in sediments and sewage sludge using on-line turbulent flow chromatography-liquid chromatography-tandem mass spectrometry.  

PubMed

A novel fully automated method based on dual column switching using turbulent flow chromatography followed by liquid chromatography coupled to tandem mass spectrometry (TFC-LC-MS/MS) was applied for the determination of endocrine disruptors (EDCs) and related compounds in sediment and sewage sludge samples. This method allows the unequivocal identification and quantification of the most relevant environmental EDCs such as natural and synthetic estrogens and their conjugates, antimicrobials, parabens, bisphenol A (BPA), alkylphenolic compounds, benzotriazoles, and organophosphorus flame retardants, minimizing time of analysis and alleviating matrix effects. Applying this technique, after the extraction of the target compounds by pressurized liquid extraction (PLE), sediment and sewage sludge extracts were directly injected to the chromatographic system and the analytes were concentrated into the clean-up loading column. Using six-port switching system, the analytes were transferred to the analytical column for subsequent detection by MS-MS (QqQ). In order to optimize this multiplexing system, a comparative study employing six types of TurboFlow™ columns, with different chemical modifications, was performed to achieve the maximum retention of analytes and best elimination of matrix components. Using the optimized protocol low limits of quantification (LOQs) were obtained ranging from 0.0083 to 1.6ng/g for sediment samples and from 0.10 to 125ng/g for sewage sludge samples (except for alkylphenol monoethoxylate). The method was used to evaluate the presence and fate of target EDCs in the Ebro River which is the most important river in Spain with intensive agricultural and industrial activities in the basin that contribute to deteriorating soil and water quality. PMID:24909438

Gorga, Marina; Insa, Sara; Petrovic, Mira; Barceló, Damià

2014-07-25

446

Metabolite analysis of human fecal water by gas chromatography/mass spectrometry with ethyl chloroformate derivatization.  

PubMed

Fecal water is a complex mixture of various metabolites with a wide range of physicochemical properties and boiling points. The analytical method developed here provides a qualitative and quantitative gas chromatography/mass spectrometry (GC/MS) analysis, with high sensitivity and efficiency, coupled with derivatization of ethyl chloroformate in aqueous medium. The water/ethanol/pyridine ratio was optimized to 12:6:1, and a two-step derivatization with an initial pH regulation of 0.1M sodium bicarbonate was developed. The deionized water exhibited better extraction efficiency for fecal water compounds than did acidified and alkalized water. Furthermore, more amino acids were extracted from frozen fecal samples than from fresh samples based on multivariate statistical analysis and univariate statistical validation on GC/MS data. Method validation by 34 reference standards and fecal water samples showed a correlation coefficient higher than 0.99 for each of the standards, and the limit of detection (LOD) was from 10 to 500pg on-column for most of the standards. The analytical equipment exhibited excellent repeatability, with the relative standard deviation (RSD) lower than 4% for standards and lower than 7% for fecal water. The derivatization method also demonstrated good repeatability, with the RSD lower than 6.4% for standards (except 3,4-dihydroxyphenylacetic acid) and lower than 10% for fecal water (except dicarboxylic acids). The qualitative means by searching the electron impact (EI) mass spectral database, chemical ionization (CI) mass spectra validation, and reference standards comparison totally identified and structurally confirmed 73 compounds, and the fecal water compounds of healthy humans were also quantified. This protocol shows a promising application in metabolome analysis based on human fecal water samples. PMID:19573517

Gao, Xianfu; Pujos-Guillot, Estelle; Martin, Jean-François; Galan, Pilar; Juste, Catherine; Jia, Wei; Sebedio, Jean-Louis

2009-10-15

447

A rapid analysis of plasma/serum ethylene and propylene glycol by headspace gas chromatography.  

PubMed

A rapid headspace-gas chromatography (HS-GC) method was developed for the analysis of ethylene glycol and propylene glycol in plasma and serum specimens using 1,3-propanediol as the internal standard. The method employed a single-step derivitization using phenylboronic acid, was linear to 200 mg/dL and had a lower limit of quantitation of 1 mg/dL suitable for clinical analyses. The analytical method described allows for laboratories with HS-GC instrumentation to analyze ethanol, methanol, isopropanol, ethylene glycol, and propylene glycol on a single instrument with rapid switch-over from alcohols to glycols analysis. In addition to the novel HS-GC method, a retrospective analysis of patient specimens containing ethylene glycol and propylene glycol was also described. A total of 36 patients ingested ethylene glycol, including 3 patients who presented with two separate admissions for ethylene glycol toxicity. Laboratory studies on presentation to hospital for these patients showed both osmolal and anion gap in 13 patients, osmolal but not anion gap in 13 patients, anion but not osmolal gap in 8 patients, and 1 patient with neither an osmolal nor anion gap. Acidosis on arterial blood gas was present in 13 cases. Only one fatality was seen; this was a patient with initial serum ethylene glycol concentration of 1282 mg/dL who died on third day of hospitalization. Propylene glycol was common in patients being managed for toxic ingestions, and was often attributed to iatrogenic administration of propylene glycol-containing medications such as activated charcoal and intravenous lorazepam. In six patients, propylene glycol contributed to an abnormally high osmolal gap. The common presence of propylene glycol in hospitalized patients emphasizes the importance of being able to identify both ethylene glycol and propylene glycol by chromatographic methods. PMID:23741644

Ehlers, Alexandra; Morris, Cory; Krasowski, Matthew D

2013-12-01

448

Long-wavelength fluorimetry as an indirect detection system in immunoaffinity chromatography: application to environmental analysis.  

PubMed

The potential of long-wavelength fluorimetry when used as the detection system in immunoaffinity chromatography is assessed for the first time by applying this approach to the analysis of water and sludge samples. Nile blue (NB) was used to synthesize a long-wavelength fluorescent tracer for linear alkylbenzenesulfonates (LASs) using the carbodiimide method, in which the amino group of NB is covalently coupled to the activated carboxylic acid group of a LAS mimic with N-hydroxysuccinimide and dicyclohexylcarbodiimide. The method consists of the injection of a pre-incubated mixture containing linear sodium 4-dodecylbenzenesulfonate (LDS; used as the LAS model), anti-LAS antibodies, and the long-wavelength tracer into a commercial Protein G column. Free and bound tracer fractions are separated in the column, and the peak height of the immunochromatogram (corresponding to the free tracer) is directly measured at 626 nm (lambda (ex)) and 674 nm (lambda (em)), and then correlated to the analyte concentration. It is not necessary to perform an elution step immediately after every sample application. The dynamic range of the method is 0.05-2.5 microg ml(-1) LDS, and the detection limit is 15 ng ml(-1). The precision, expressed as the relative standard deviation, is 4.8-6.4%. Other surfactants (sodium dodecylsulfate and Triton X-100) do not cause interference. The recoveries obtained by applying the method to the analysis of water (ground- and wastewater) and sludge (primary and activated) samples ranged from 86.0 to 111.3%. Water sample analysis included an initial solid-phase extraction step, which cleaned up the samples and improved the detection limit fivefold. PMID:16953323

Sánchez-Martínez, M L; Aguilar-Caballos, M P; Eremin, S A; Gómez-Hens, A

2006-11-01

449

Sources of Variability in Chlorophyll Analysis by Fluorometry and by High Performance Liquid Chromatography. Chapter 22  

NASA Technical Reports Server (NTRS)

The need for accurate determination of chlorophyll a (chl a) is of interest for numerous reasons. From the need for ground-truth data for remote sensing to pigment detection for laboratory experimentation, it is essential to know the accuracy of the analyses and the factors potentially contributing to variability and error. Numerous methods and instrument techniques are currently employed in the analyses of chl a. These methods range from spectrophotometric quantification, to fluorometric analysis and determination by high performance liquid chromatography. Even within the application of HPLC techniques, methods vary. Here we provide the results of a comparison among methods and provide some guidance for improving the accuracy of these analyses. These results are based on a round-robin conducted among numerous investigators, including several in the Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) and HyCODE Programs. Our purpose here is not to present the full results of the laboratory intercalibration; those results will be presented elsewhere. Rather, here we highlight some of the major factors that may contribute to the variability observed. Specifically, we aim to assess the comparability of chl a analyses performed by fluorometry and HPLC, and we identify several factors in the analyses which may contribute disproportionately to this variability.

VanHeukelem, Laurie; Thomas, Crystal S.; Glibert, Patricia M.

2001-01-01

450

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

2011-12-15

451

Analysis of the monosaccharide components in Angelica polysaccharides by high performance liquid chromatography.  

PubMed

An analytical method of on-line high performance liquid chromatography (HLPC) was developed to simultaneously separate and identify the monosaccharide composition of three Angelica polysaccharide fractions (APF), named APF1, APF2 and APF3. In this method, APF were hydrolyzed into component monosaccharides and subsequently labeled with 1-phenyl-3-methyl-5-pyrazolone (PMP), and then the labeled monosaccharide derivatives were separated by a reverse-phase C18 column and monitored by UV absorbance at 250 nm. The results showed that nine monosaccharide derivatives have been well separated by HPLC under optimized conditions and the composition analysis of monosaccharides from APF samples could be achieved using acid hydrolysis and a set of monosaccharide standards. With this method, the within-day and day to day precisions of the composition determinations were 3.41-4.87% and 3.12-4.93% (RSD), respectively. The method was successfully applied to the determination of the component monosaccharides of Angelica polysaccharides. PMID:16270574

Yang, Xingbin; Zhao, Yan; Wang, Qingwei; Wang, Haifang; Mei, Qibing

2005-10-01

452

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

453

Liquid chromatography-tandem mass spectrometry analysis of eicosanoids and related compounds in cell models.  

PubMed

Enzyme- and free radical-catalyzed oxidation of polyunsaturated fatty acids (PUFAs) produces the eicosanoids, docosanoids and octadecanoids. This large family of potent bioactive lipids is involved in many biochemical and signaling pathways which are implicated in physiological and pathophysiological processes and can be viable therapeutic targets. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers selectivity, sensitivity, robustness and high resolution and is able to analyze a large number of eicosanoids in biological samples in a short time. The present article reviews and discusses reported LC-MS/MS methods and the results obtained from their application in cell models. Reliable analytical outcomes are critically important for understanding physiological and pathophysiological cellular processes, such as inflammation, diseases with inflammatory components (e.g., cardiovascular disease, diabetes, metabolic syndrome), as well as cancer. Reported findings obtained by using the LC-MS/MS methodology in cell systems may have important predictive as well as nutritional and pharmacological implications. We conclude that the LC-MS/MS methodology is a versatile and reliable analytical tool for the simultaneous analysis of multiple PUFA-derived metabolites including the eicosanoids in cell culture samples at concentrations on the pM/nM threshold, i.e. at baseline and after stimulation. PMID:24932539

Martin-Venegas, Raquel; Jáuregui, Olga; Moreno, Juan Jose

2014-08-01

454

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

455

[Separation of tannins in Rhubarb and its analysis by high performance liquid chromatography-mass spectrometry].  

PubMed

In order to investigate the pharmaceutical actions of rhubarb, a method for extracting, separating and analyzing the tannin components in rhubarb was studied. At first, a procedure for the group separation of tannins from the water-ethanol extract of rhubarb was established based on the formation of tannins-caffein precipitation. Then, a high performance liquid chromatographic (HPLC) method for the analysis of tannins in rhubarb was developed. This HPLC method is based on a reversed-phase C18 column and polar mobile-phase such as water and methanol with gradient elution, and the tannins can be well separated. Finally, the identification of the tannin components in rhubarb was carried out by high performance liquid chromatography-mass spectrometry (HPLC-MS). The structures of the main tannin components (gallic acid, catechin, the dimer, trimer, tetramer and pentamer of catechin) in rhubarb are suggested. The fragmentation laws of the tannin components are summarized. In comparing with previous methods, it is simple and without the interference of co-existed compounds. PMID:15807111

Ding, Mingyu; Ni, Weiwei

2004-11-01

456

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

457

[Honey adulteration detection using liquid chromatography/ elemental analysis-isotope ratio mass spectrometry].  

PubMed

A new method for honey adulteration detection using liquid chromatography/elemental analysis-isotope ratio mass spectrometry (LC/EA-IRMS) was developed. Based on the individual delta13C values detected for 38 authentic honey samples, the limits for the authentic honey samples were proposed: the delta13C difference between protein and honey (Deltadelta13C(P-H)) should be higher or equal to than -0.95 per thousand, the delta13C difference between fructose and glucose (Deltadelta13C(F-G)) should be from -0.64 per thousand to 0.53 per thousand, and the maximum difference of delta13C values between all the components (Deltadelta13Cmax) should be lower than 2.09 per thousand. Based on the above criteria, the 58 positive samples spiked with C4 or C3 plant sugar syrup were confirmed by LC/EA-IRMS method from 150 commercial honey samples, while only 7 samples spiked with C4 plant sugar syrup were confirmed by the official EA-IRMS method. The proposed method represents a significant improvement in comparing with the official EA-IRMS method. PMID:21574394

Fei, Xiaoqing; Wu, Bin; Sehn, Chongyu; Ding, Tao; Li, Lihua; Lu, Ying

2011-01-01

458

Qualitative and quantitative environmental analysis by capillary column gas chromatography/lightpipe Fourier transform infrared spectrometry  

SciTech Connect

A new state-of-art commercial gas chromatography/Fourier transform infrared (GC/FT-IR) lightpipe-containing system has been evaluated for its applicability to qualitative and quantitative environmental analysis of typical environmental contaminants. This system exhibited minimum identifiable quantities, for many compounds, in the 10-50-ng range. On a wide-bore capillary column, quantitation curves generated from chromatogram peak areas were linear over the 10-250-ng range. The mean correlation coefficient for 38 quantitation calibration curves on 24 standards was 0.976. The selectivity of the new system was evaluated with standards, soil, and still-bottom samples. It was demonstrated with 27 standards that no discernible loss in identification selectivity occurred when a narrow-band infrared detector (spectral cutoff 750 cm/sup -1/) was used in place of a midband detector (cutoff 700 cm/sup -1/). This allows the meaningful utilization of the extra sensitivity associated with narrower frequency range infrared detectors.

Gurka, D.F.; Pyle, S.M.

1988-08-01

459

[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

460

Analysis of omnoponum by surface-ionization mass spectrometry and liquid chromatography tandem mass spectrometry methods.  

PubMed

This paper provides the development of analytical capabilities of surface-ionization mass spectrometry (SI/MS) and high performance liquid chromatography with tandem mass spectrometry (HPLC/MS/MS) for narcotic analgesic omnoponum, which perfectly exemplifies a mixture of opium alkaloids. It has been revealed that the investigated opiates solution, omnoponum, is ionized by the surface ionization (SI) method with high sensitivity. In the SI mass spectrum, M+, (M-H)+, (M-H-2nH)+, (M-R)+ and (M-R-2nH)+ ion lines, where M is a molecule, H is the hydrogen atom and R is a radical, were observed. These ion lines consist of combined omnoponum mixture SI mass spectra, i.e. morphine, codeine, thebaine, papaverine, and narcotine. Moreover, while the study of omnoponum by HPLC/MS/MS methods has attested that the mixture really consists of 5 components, it has been demonstrated that the SI/MS method can be utilized for the analysis of this mixture without the necessity of its chromatographic separation. PMID:20674208

Usmanov, Dilshadbek; Khasanov, Usman; Pantsirev, Aleksey; Van Bocxlaer, Jan

2010-12-01

461

Pesticide analysis in tomatoes by solid-phase microextraction and micellar electrokinetic chromatography.  

PubMed

The analysis of a group of seven pesticides (i.e. six fungicides: pyrimethanil, procymidone, nuarimol, fenarimol, benalaxyl and penconazole and one insecticide: pirimicarb) in tomato samples by micellar electrokinetic chromatography is investigated. For this purpose, reversed electrode polarity stacking mode and solid-phase microextraction (SPME) have been used as on-line and off-line preconcentration procedures, respectively. Tomato samples were first homogenized and extracted with acetone. After suitable evaporation and reconstitution of the extract in water, a SPME procedure using poly(dimethylsiloxane)/divinylbenzene fibers was used. Due to the strong influence of the sample matrix in the extraction, a matrix matched calibration of spiked tomato samples was developed. The method was found to be linear between 0.5 and 2.5 mg/kg. Limits of detection achieved are below the maximum residue limits established by the European Union and Spain legislation as well as by the Codex Alimentarius (except for penconazole). The potential of the method was demonstrated by analyzing 12 tomato samples (of ecological and non-ecological production) taken from regional cultivars. No residues of the selected pesticides were detected in any of the samples. PMID:18280487

Ravelo-Pérez, Lidia M; Hernández-Borges, Javier; Borges-Miquel, Teresa M; Rodríguez-Delgado, Miguel Angel

2008-03-21

462

Enrichment of Integral Membrane Proteins for Proteomic Analysis Using Liquid Chromatography-Tandem Mass Spectrometry  

SciTech Connect

Currently, most proteomic studies rely on liquid chromatography-tandem mass spectrometry (LC-MS/MS) to detect and identify constituent peptides of enzymatically digested proteins obtained from various organisms and cell types. However, sample preparation methods for isolating membrane proteins typically involve the use of detergents, chaotropes, or reducing reagents that often interfere with electrospray ionization (ESI). To increase the identification of integral membrane proteins by LC-ESI-MS/MS, a sample preparation method combining carbonate extraction and surfactant-free organics solvent-assisted solubilization and proteolysis was developed and used to target the membrane subproteome of Deinococcus radiodurans. Out of 503 proteins identified, 135 were recognized as hydrophobic based on their positive grand average of hydropathicity values that covers 15% of the theoretical hydrophobic proteome. Using the PSORT algorithm, 268 identified proteins were recognized as integral membrane proteins covering 21% and 43% of the predicted integral cytoplasmic and outer membrane proteins, respectively. Of the integral cytoplasmic membrane proteins containing four or more predicted transmembrane domains (TMDs), 65% were identified by detecting at least one peptide spanning a TMD using LC-MS/MS. The extensive identification of highly hydrophobic proteins containing multiple TMDs confirms the efficacy of the described sample preparation protocol to isolate and solubilize integral membrane proteins and validates the method for large-scale analysis of bacterial membrane subproteomes using LC-ESI-MS/MS.

Blonder, Josip; Goshe, Michael B.; Moore, Ronald J.; Pasa-Tolic, Liljiana; Masselon, Christophe D.; Lipton, Mary S.; Smith, Richard D.

2002-04-01

463

Analysis of testosterone and dihydrotestosterone in mouse tissues by liquid chromatography-electrospray tandem mass spectrometry  

PubMed Central

A novel method was established for simultaneous quantitation of testosterone (T) and dihydrotestosterone (DHT) in murine tissue and serum samples. Endogenous T and DHT, together with the internal standards, 17?-methyl-T and 17?-methyl-DHT, were extracted from tissues, and then derivatized by reaction with 2-hydrazino-4-(trifluoromethyl)-pyrimidine (HTP). Analysis by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) resulted in production spectra of HTP derivatives of both T and DHT that showed analyte-specific fragmentations; the latter fragmentations were characterized by use of high-resolution Orbitrap MS/MS. These specific fragmentations enabled quantitation of T and DHT in the multiple-reaction monitoring (MRM) mode. The method was validated with charcoal-stripped serum as the matrix; the LLOQ was 0.10 ng/ml for T and 0.50 ng/ml for DHT. The method was then used for determination of serum and tissue levels of T and DHT in transgenic mice carrying a hypomorphic NADPH-cytochrome P450 reductase gene (Cpr-low mice). Remarkably, ovarian T levels in Cpr-low mice were found to be 25-fold higher than those in wild-type mice, a finding that at least partly explains the female infertility seen in the Cpr-low mice. In conclusion, our method provides excellent sensitivity and selectivity for determination of endogenous levels of T and DHT in mouse tissues.

Weng, Yan; Xie, Fang; Xu, Li; Zagorevski, Dmitri; Spink, David C.; Ding, Xinxin

2010-01-01

464

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

2005-03-01

465

Supercritical fluid chromatography as a method of analysis for the determination of 4-hydroxybenzylglucosinolate degradation products.  

PubMed

In the present study analytical and preparative supercritical fluid chromatography (SFC) were used for investigation of myrosinase catalysed degradation of 4-hydroxybenzylglucosinolate (sinalbin). Sinalbin occurs as a major glucosinolate in seeds of Sinapis alba L., in various mustards and other food products. The degradation products were identified and quantified by analysis based on a developed SFC method using a bare silica column. Determinations comprised transformation products of sinalbin, produced both during degradation of isolated sinalbin, and during autolysis of meal from S. alba seeds. The conditions in the developed SFC method were used as basis for the preparative SFC procedure applied for isolation of the components prior to their identification by nuclear magnetic resonance (NMR) spectroscopy. Myrosinase catalysed sinalbin hydrolysis resulted in the reactive 4-hydroxybenzyl isothiocyanate as an initial product at pH values from 3.5 to 7.5 whereas 4-hydroxybenzyl cyanide was one of the major products at low pH values. 4-Hydroxybenzyl isothiocyanate was found to disappear from the aqueous reaction mixtures in a few hours, as it reacted easily with available nucleophilic reagents. 4-Hydroxybenzyl alcohol was found as the product from reaction with water, and with ascorbic acid, 4-hydroxybenzylascorbigen was produced. PMID:10869674

Buskov, S; Hasselstrøm, J; Olsen, C E; Sørensen, H; Sørensen, J C; Sørensen, S

2000-07-01

466

Multi-mycotoxin analysis in dairy products by liquid chromatography coupled to quadrupole orbitrap mass spectrometry.  

PubMed

A new analytical method was developed and validated for simultaneous analysis of 58 mycotoxins in dairy products. Response surface methodology was employed to optimize a quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation method. Ultrahigh-performance liquid chromatography and electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC/ESI Q-Orbitrap) was used for the separation and detection of all the analytes. The method was validated by taking into consideration the guidelines specified in Commission Decision 2002/657/EC and 401/2006/EC. The extraction recoveries were in a range of 86.6-113.7%, with coefficient of variation <6.2%. The 58 compounds could be detected in the 0.001-100 ?g kg(-1) concentration range, with correlation coefficient >0.99. The limits of detection for the analytes are in the range 0.001-0.92 ?g kg(-1). The repeatability was lower than 6.4%. This method has been successfully applied on screening of mycotoxins in commercial dairy product samples, and it is very useful for fast screening of different food contaminants. PMID:24794937

Jia, Wei; Chu, Xiaogang; Ling, Yun; Huang, Junrong; Chang, James

2014-06-01

467

Automated analysis of primary amino acids in plasma by high-performance liquid chromatography.  

PubMed

The concentration of primary amino acids (AAs) in plasma can accurately be determined using high-performance liquid chromatography (HPLC). Before the analysis can be performed, several steps have to be regarded. First, the time and method of blood withdrawal, type of blood tube, use of medication, and differences in dietary intake are important factors that should be standardized. Second, the handling of and the way the blood is transported to the laboratory, the time between blood withdrawal and centrifugation, the method of centrifugation, and the temperature and time of plasma storage have to be noticed. Third, the methods used for deproteinization and derivatization may account for varying results between laboratories.In this chapter, we describe an HPLC method that measures primary amino acids in plasma using automated precolumn derivatization with ortho-phthalaldehyde, and that pays attention to the above-mentioned criteria. This method is relatively fast, simple, sensitive, and reliable. Since with this method we can determine over 40 physiological amino acids with a very good resolution, trace amounts of amino acids can also be determined. In addition, interassay resolution times have very low variation and the use of two internal standards guarantees reliable quantification. PMID:22125146

Fekkes, Durk

2012-01-01

468

Analysis of citrulline, arginine, and methylarginines using high-performance liquid chromatography.  

PubMed

Citrulline is a product of arginine degradation by nitric oxide synthase and is a precursor for arginine synthesis in animal cells. After arginine is incorporated into proteins, it may undergo methylation to form N(G)-monomethylarginine, which may be converted to asymmetric dimethylarginine and symmetric dimethylarginine. The degradation of these methylated proteins produces free methylarginines. This chapter focuses on the analysis of these amino acids in biological samples (including plasma/serum, urine, cell culture medium, and tissues) using high-performance liquid chromatography that involves precolumn derivatization with o-phthaldialdehyde. Fluorescence is monitored at excitation and emission wavelengths of 340 and 455 nm, respectively. Detection limits are 5 nM for amino acids. The assays are linear between 1 and 100 microM for citrulline and arginine and between 0.1 and 10 microM for methylarginines. These chromatographic methods are highly sensitive, specific, accurate, and easily automated and provide a useful tool to study the regulation of the arginine-nitric oxide pathway. PMID:18423217

Wu, Guoyao; Meininger, Cynthia J

2008-01-01

469