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Retention time predictions in Gas Chromatography
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
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 [en]
gas chromatography, computer simulation, two-parameter model, retention time prediction
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-55088ISBN: 978-91-7447-210-3 (print)OAI: oai:DiVA.org:su-55088DiVA: diva2:400908
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
List of papers
1. Prediction of retention times of polycyclic aromatic hydrocarbons and n -alkanes in temperature-programmed gas chromatography
Open this publication in new window or tab >>Prediction of retention times of polycyclic aromatic hydrocarbons and n -alkanes in temperature-programmed gas chromatography
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.

Keyword
Gas chromatography, Polycyclic aromatic hydrocarbons, n-Alkanes, Retention time, Prediction
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-24549 (URN)10.1007/s00216-007-1528-0 (DOI)
Available from: 2007-11-07 Created: 2007-11-07 Last updated: 2017-12-13Bibliographically approved
2. Retention time prediction of compounds in Grob standard mixture for apolar capillary columns in temperature-programmed gas chromatography
Open this publication in new window or tab >>Retention time prediction of compounds in Grob standard mixture for apolar capillary columns in temperature-programmed gas chromatography
2009 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 393, no 1, 327-334 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents an extension of a previous investigation in which the behavior of nonpolar compounds in temperature-programmed gas chromatographic runs was predicted using thermodynamic (entropy and enthalpy) parameters derived from isothermal runs. In a similar manner, entropy and enthalpy parameters were determined for a Grob standard mixture of compounds with widely varying chemical characteristics. These parameters were used to predict the retention times and chromatographic behaviors of the compounds on four gas chromatography capillary columns: three that had phenyl-based stationary phases (with degrees of substitution of 0%, 5% and 50%) and one with (50%) cyanopropyl substitution. The predictions matched data empirically obtained from temperature-programmed chromatographic runs for all of the compounds extremely well, despite the wide variations in polarity of both the compounds and stationary phases. Thus, the results indicate that such simulations could greatly reduce the time and material costs of chromatographic optimizations.

Keyword
Gas chromatography, Grob standard mixture, Retention time, Retention order, Prediction
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-54986 (URN)10.1007/s00216-008-2295-2 (DOI)000261831000037 ()
Available from: 2011-02-23 Created: 2011-02-23 Last updated: 2017-12-11Bibliographically approved
3. Study of the chromatographic behaviour of selected alcohols and amines
Open this publication in new window or tab >>Study of the chromatographic behaviour of selected alcohols and amines
2011 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 399, no 3, 1335-1345 p.Article in journal (Refereed) Published
Abstract [en]

The gas chromatographic behavior of selected linear and non-linear alcohols and amines was investigated using four capillary columns containing phenyl substitution levels of 0%, 5%, and 50% and 50% cyanopropyl substitution. In a previous study, the positions of specific compounds inside the capillary column were iteratively modeled using only two thermodynamic parameters (ΔH and ΔS). The present study addresses the validation of the two-parameter model for retention time prediction for selected alcohols and amines using thermodynamic data obtained from as few as two data points. The difference between predicted and observed retention times under different temperature conditions was generally less than 1% of the experimental value and the predicted order of elution was correct in the used model.

Keyword
Gas chromatography, Alcohols, Amines, Prediction, Retention time
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-54987 (URN)10.1007/s00216-010-4418-9 (DOI)000286599100033 ()
Available from: 2011-02-23 Created: 2011-02-23 Last updated: 2017-12-11Bibliographically approved
4. Comparing columns for gas chromatography with the two-parameter model for retention prediction
Open this publication in new window or tab >>Comparing columns for gas chromatography with the two-parameter model for retention prediction
2011 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 31, 5305-5310 p.Article in journal (Refereed) Published
Abstract [en]

The retention times of selected compounds in temperature programmed gas chromatography were predicted using a two-parameter model, on the basis of thermodynamic data obtained from isothermal runs on seven capillary columns, primarily substituted with 5% diphenylsiloxane. The scope for using thermodynamic data obtained from isothermal runs on one column to optimize separation on a different column or a different instrument setup was investigated. Additionally, the predictive utility of thermodynamic data obtained using a DB-5 column that had been in use for three years was compared to that of a new column of the same model. It was found that satisfactory separation could be achieved on one capillary column or instrument setup on the basis of thermodynamic data obtained using a different column or instrument set-up.

Keyword
Gas chromatography, Prediction, Retention time, PCA score plot, Aged column, Thermodynamic properties
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-68295 (URN)10.1016/j.chroma.2011.05.082 (DOI)000293432200035 ()
Note

authorCount :3

Available from: 2012-01-15 Created: 2012-01-03 Last updated: 2017-06-20

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