497 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Gas Chromatography"  
Results: 1 - 24 next

Activity Coefficients at Infinite Dilution for Organic Solutes Dissolved in Three 1-Alkyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Bearing Short Linear Alkyl Side Chains of Three to Five Carbons

Description: Article discussing activity coefficients at infinite dilution for organic solutes dissolved in three 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids bearing short linear alkyl side chains of three to five carbons.
Date: July 30, 2013
Creator: Mutelet, Fabrice; Hassan, El-Sayed R. E.; Stephens, Timothy W.; Acree, William E. (William Eugene) & Baker, Gary A.
Item Type: Refine your search to only Article
Partner: UNT College of Arts and Sciences

Study of Ether-, Alcohol-, or Cyano-Functionalized Ionic Liquids Using Inverse Gas Chromatography

Description: This article discusses the study of ether-, alcohol, or cyano-functionalized ionic liquids using inverse gas chromatography.
Date: March 11, 2010
Creator: Revelli, Anne-Laure; Mutelet, Fabrice; Jaubert, Jean-Noël; Garcia-Martinez, Marina; Sprunger, Laura M.; Acree, William E. (William Eugene) et al.
Item Type: Refine your search to only Article
Partner: UNT College of Arts and Sciences

Partition Coefficients of Organic Compounds in Four New Tetraalkylammonium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Using Inverse Gas Chromatography

Description: This article discusses partition coefficients of organic compounds in four new tetraalkylammonium bis(trifluoromethylsulfonyl)imide ionic liquids using inverse gas chromatography.
Date: August 18, 2011
Creator: Acree, William E. (William Eugene); Baker, Gary A.; Mutelet, Fabrice & Moïse, Jean-Charles
Item Type: Refine your search to only Article
Partner: UNT College of Arts and Sciences

Partition Coefficients of Organic Compounds in New Imidazolium and Tetralkylammonium Based Ionic Liquids Using Inverse Gas Chromatography

Description: This article discusses partition coefficients of organic compounds in new imidazolium and tetralkylammonium based ionic liquids using inverse gas chromatography.
Date: September 11, 2009
Creator: Mutelet, Fabrice; Revelli, Anne-Laure; Jaubert, Jean-Noël; Sprunger, Laura M.; Baker, Gary A. & Acree, William E. (William Eugene)
Item Type: Refine your search to only Article
Partner: UNT College of Arts and Sciences

Determination of Solute Descriptors for Illicit Drugs Using Gas Chromatographic Retention Data and Abraham Solvation Model

Description: In this experiment, more than one hundred volatile organic compounds were analyzed with the gas chromatograph. Six capillary columns ZB wax plus, ZB 35, TR1MS, TR5, TG5MS and TG1301MS with different polarities have been used for separation of compounds and illicit drugs. The Abraham solvation model has five solute descriptors. The solute descriptors are E, S, A, B, L (or V). Based on the six stationary phases, six equations were constructed as a training set for each of the six columns. The six equations served to calculate the solute descriptors for a set of illicit drugs. Drugs studied are nicotine (S= 0.870, A= 0.000, B= 1.073), oxycodone(S= 2.564. A= 0.286, B= 1.706), methamphetamine (S= 0.297, A= 1.570, B= 1.009), heroin (S=2.224, A= 0.000, B= 2.136) and ketamine (S= 1.005, A= 0.000, B= 1.126). The solute property of Abraham solvation model is represented as a logarithm of retention time, thus the logarithm of experimental and calculated retention times is compared.
Date: August 2015
Creator: Mitheo, Yannick K.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

The Analysis of Volatile Impurities in Air by Gas Chromatography/Mass Spectrometry

Description: The determination of carbon monoxide is also possible by trapping CO on preconditioned molecular sieve and thermal desorption. Analysis in this case is performed by gas chromatography/mass spectroscopy, although the trapping technique is applicable to other suitable GC techniques.
Date: May 1993
Creator: Talasek, Robert Thomas
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

A reduced order model for the study of asymmetries in linear gas chromatography for homogeneous tubular columns.

Description: In gas chromatography, a chemical sample separates into its constituent components as it travels along a long thin column. As the component chemicals exit the column they are detected and identified, allowing the chemical makeup of the sample to be determined. For correct identification of the component chemicals, the distribution of the concentration of each chemical along the length of the column must be nearly symmetric. The prediction and control of asymmetries in gas chromatography has been an active research area since the advent of the technique. In this paper, we develop from first principles a general model for isothermal linear chromatography. We use this model to develop closed-form expressions for terms related to the first, second, and third moments of the distribution of the concentration, which determines the velocity, diffusion rate, and asymmetry of the distribution. We show that for all practical experimental situations, only fronting peaks are predicted by this model, suggesting that a nonlinear chromatography model is required to predict tailing peaks. For situations where asymmetries arise, we analyze the rate at which the concentration distribution returns to a normal distribution. Numerical examples are also provided.
Date: August 1, 2005
Creator: Whiting, Joshua J.; Romero, Louis Anthony & Parks, Michael L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

On the two-domain equations for gas chromatography.

Description: We present an analysis of gas chromatographic columns where the stationary phase is not assumed to be a thin uniform coating along the walls of the cross section. We also give an asymptotic analysis assuming that the parameter {beta} = KD{sup II}{rho}{sup II}/D{sup I}{rho}{sup I} is small. Here K is the partition coefficient, and D{sup i} and {rho}{sup i}, i = I, II are the diffusivity and density in the mobile (i = I) and stationary (i = II) regions.
Date: January 1, 2009
Creator: Romero, Louis Anthony & Parks, Michael L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Activity Coefficients at Infinite Dilution for Organic Compounds Dissolved in 1-Alkyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Having Six-, Eight-, and Ten-Carbon Alkyl Chains

Description: Article on activity coefficients at infinite dilution for organic compounds dissolved in 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids having six-, eight-, and ten-carbon alkyl chains.
Date: October 31, 2012
Creator: Acree, William E. (William Eugene); Baker, Gary A.; Revelli, Anne-Laure; Moïse, Jean-Charles & Mutelet, Fabrice
Item Type: Refine your search to only Article
Partner: UNT College of Arts and Sciences

Experimental Determination of L, Ostwald Solubility Solute Descriptor for Illegal Drugs By Gas Chromatography and Analysis By the Abraham Model

Description: The experiment successfully established the mathematical correlations between the logarithm of retention time of illegal drugs with GC system and the solute descriptor L from the Abraham model. the experiment used the method of Gas Chromatography to analyze the samples of illegal drugs and obtain the retention time of each one. Using the Abraham model to calculate and analyze the sorption coefficient of illegal drugs is an effective way to estimate the drugs. Comparison of the experimental data and calculated data shows that the Abraham linear free energy relationship (LFER) model predicts retention behavior reasonably well for most compounds. It can calculate the solute descriptors of illegal drugs from the retention time of GC system. However, the illegal drugs chosen for this experiment were not all ideal for GC analysis. HPLC is the optimal instrument and will be used for future work. HPLC analysis of the illegal drug compounds will allow for the determination of all the solute descriptors allowing one to predict the illegal drugs behavior in various Abraham biological and medical equations. the results can be applied to predict the properties in biological and medical research which the data is difficult to measure. the Abraham model will predict more accurate results by increasing the samples with effective functional groups.
Date: May 2012
Creator: Wang, Zhouxing
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Activity Coefficients at Infinite Dilution of Organic Compounds in Trihexyl(tetradecyl)phosphonium Bis(trifluoromethylsulfonyl)imide Using Inverse Gas Chromatography

Description: Article on activity coefficients at infinite dilution of organic compounds in trihexyl(tetradecyl)phosphonium Bis(trifluoromethylsulfonyl)imide using inverse gas chromatography.
Date: February 2, 2009
Creator: Revelli, Anne-Laure; Sprunger, Laura M.; Gibbs, Jennifer; Acree, William E. (William Eugene); Baker, Gary A. & Mutelet, Fabrice
Item Type: Refine your search to only Article
Partner: UNT College of Arts and Sciences

Sample extraction and injection with a microscale preconcentrator.

Description: This report details the development of a microfabricated preconcentrator that functions as a fully integrated chemical extractor-injector for a microscale gas chromatograph (GC). The device enables parts-per-billion detection and quantitative analysis of volatile organic compounds (VOCs) in indoor air with size and power advantages over macro-scale systems. The 44 mm{sup 3} preconcentrator extracts VOCs using highly adsorptive, granular forms of graphitized carbon black and carbon molecular sieves. The micron-sized silicon cavities have integrated heating and temperature sensing allowing low power, yet rapid heating to thermally desorb the collected VOCs (GC injection). The keys to device construction are a new adsorbent-solvent filling technique and solvent-tolerant wafer-level silicon-gold eutectic bonding technology. The product is the first granular adsorbent preconcentrator integrated at the wafer level. Other advantages include exhaustive VOC extraction and injection peak widths an order of magnitude narrower than predecessor prototypes. A mass transfer model, the first for any microscale preconcentrator, is developed to describe both adsorption and desorption behaviors. The physically intuitive model uses implicit and explicit finite differences to numerically solve the required partial differential equations. The model is applied to the adsorption and desorption of decane at various concentrations to extract Langmuir adsorption isotherm parameters from effluent curve measurements where properties are unknown a priori.
Date: September 1, 2007
Creator: Robinson, Alex Lockwood (Advanced Sensor Technologies, Albuquerque, NM) & Chan, Helena Kai Lun
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

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

Description: 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. ...
Date: September 1, 2010
Creator: Van Benthem, Mark Hilary; Mowry, Curtis Dale; Kotula, Paul Gabriel & Borek, Theodore Thaddeus, III
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department