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Prediction of retention times of polycyclic aromatic hydrocarbons and n -alkanes in temperature-programmed gas chromatography
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
2007 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 389, no 3, 941-950 p.Article in journal (Refereed) Published
Abstract [en]

We have developed an iterative procedure for predicting the retention times of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes during separations by temperature-programmed gas chromatography. The procedure is based on estimates of two thermodynamic properties for each analyte (the differences in enthalpy and entropy associated with movements between the stationary and mobile phases) derived from data acquired experimentally in separations under isothermal conditions at temperatures spanning the range covered by the temperature programs in ten-degree increments. The columns used for this purpose were capillary columns containing polydimethylsiloxane-based stationary phases with three degrees of phenyl substitution (0%, 5%, and 50%). Predicted values were mostly within 1% of experimentally determined values, implying that the method is stable and precise.

Place, publisher, year, edition, pages
2007. Vol. 389, no 3, 941-950 p.
Keyword [en]
Gas chromatography, Polycyclic aromatic hydrocarbons, n-Alkanes, Retention time, Prediction
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-24549DOI: 10.1007/s00216-007-1528-0OAI: oai:DiVA.org:su-24549DiVA: diva2:197773
Available from: 2007-11-07 Created: 2007-11-07 Last updated: 2017-12-13Bibliographically approved
In thesis
1. New Tools for Trapping and Separation in Gas Chromatography and Dielectrophoresis: Improved Performance by Aid of Computer Simulation
Open this publication in new window or tab >>New Tools for Trapping and Separation in Gas Chromatography and Dielectrophoresis: Improved Performance by Aid of Computer Simulation
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Computer simulations can be useful aids for both developing new analytical methods and enhancing the performance of existing techniques. This thesis is based on studies in which computer simulations were key elements in the development of several new tools for use in gas chromatography and dielectrophoresis. In gas chromatography, gaseous analytes are separated by exploiting differences in their partitioning between different phases, and after their partitioning parameters have been determined the separations can be computationally predicted, and optimized, for a wide range of operating conditions. Similarly, in dielectrophoresis, particles with differing polarizability or size can be separated, and since particle trajectories within a separation device can be predicted using computations, the suitability of new designs, applications of forces and combinations of operational parameters can be assessed without necessarily making or empirically testing all of the variants.

Using two existing numerical methods combined with semi-empirical determinations of retention behavior, temperature-programmed gas chromatograms were predicted with less than one percent deviations from experimental data, and a new method for improving the capacity of a gas-trapping device was predicted and experimentally verified. In addition, two new concepts with potential capacity to enhance dielectrophoretic separations were developed and tested in simulations. The first provides a promising way to improve the trapping of bacteria in media with elevated conductivity by using super-positioned electric fields, and the second a way to increase selectivity in the separation of bio-particles by using multiple dielectrophoretic cycles. The studies also introduced a more accurate method for determining the conductivity of suspensions of bacteria, and a new computational method for determining the dielectrophoretic behavior of particles in concentrated suspensions.

The scientific studies are summarized and discussed in the main text of this thesis, and presented in detail in seven appended papers.

Place, publisher, year, edition, pages
Stockholm: Institutionen för analytisk kemi, 2007. 92 p.
Keyword
gas chromatography, dielectrophoresis, computer simulation, finite element method, trapping, separation, lab-on-a-chip
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-7170 (URN)978-91-7155-526-7 (ISBN)
Public defence
2007-12-07, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Opponent
Supervisors
Available from: 2007-11-07 Created: 2007-11-07Bibliographically approved
2. Retention time predictions in Gas Chromatography
Open this publication in new window or tab >>Retention time predictions in Gas Chromatography
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In gas chromatography, analytes are separated by differences in their partition between a mobile phase and a stationary phase. Temperature-program, column dimensions, stationary and mobile phases, and flow rate are all parameters that can affect the quality of the separation in gas chromatography. To achieve a good separation (in a short amount of time) it is necessary to optimize these parameters. This can often be quite a tedious task.

Using computer simulations, it is possible to both gain a better understanding of how the different parameters govern retention and separation of a given set of analytes, and to optimize the parameters within minutes. In the research presented here, this was achieved by taking a thermodynamic approach that used the two parameters ΔH (enthalpy change) and ΔS (entropy change) to predict retention times for gas chromatography. By determining these compound partition parameters, it was possible to predict retention times for analytes in temperature-programmed runs. This was achieved through the measurement of the retention times of n-alkanes, PAHs, alcohols, amines and compounds in the Grob calibration mixture in isothermal runs. The isothermally obtained partition coefficients, together with the column dimensions and specifications, were then used for computer simulation using in-house software.

The two-parameter model was found to be both robust and precise and could be a useful tool for the prediction of retention times. It was shown that it is possible to calculate retention times with good precision and accuracy using this model. The relative differences between the predicted and experimental retention times for different compound groups were generally less than 1%.

The scientific studies (Papers I-IV) are summarized and discussed in the main text of this thesis. 

Place, publisher, year, edition, pages
Stockholm: Department of Analytical Chemistry, Stockholm University, 2011. 63 p.
Keyword
gas chromatography, computer simulation, two-parameter model, retention time prediction
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-55088 (URN)978-91-7447-210-3 (ISBN)
Public defence
2011-04-01, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.Available from: 2011-03-10 Created: 2011-02-28 Last updated: 2012-07-26Bibliographically approved

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