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Depletion solid-phase microextraction for the evaluation of fiber-sample partition coefficients of pesticides

Zimmermann, Thomas and Ensinger, Wolfgang and Schmidt, Torsten C. (2006):
Depletion solid-phase microextraction for the evaluation of fiber-sample partition coefficients of pesticides.
In: Journal of chromatography A, Elsevier, pp. 51-59, 1102, (1-2), [Article]

Abstract

A depletion solid-phase microextraction (SPME) method for the characterisation of SPME sorption for 13 pesticides selected as probe compounds is described. The sample is extracted and analysed multiple times by SPME-GC/MS. The observed depletion in peak areas is used for the calculation of extraction ratios that varied between 3 and 28% for a PDMS fiber with confidence intervals between 0.7 and 5.4%. Apparent fiber-sample partition coefficients can be calculated and extrapolated to equilibrium conditions if specific sorption kinetics are known. Under the chosen conditions, problems were encountered for more polar compounds (log Kow < 3) due to inefficient extraction. The extracted amount was found to be the decisive parameter for depletion SPME and the extraction conditions therefore need to be adapted to the polarity of the analyte. The importance of the initial analyte concentration especially for mixed-mode fibers is demonstrated. Compared with conventional external calibration using liquid injection, depletion SPME eliminates uncertainties due to solvent effects during injection. Furthermore, it does neither require authentic reference compounds nor knowledge of the initial analyte concentration, and thus can even be used for unknowns.

Item Type: Article
Erschienen: 2006
Creators: Zimmermann, Thomas and Ensinger, Wolfgang and Schmidt, Torsten C.
Title: Depletion solid-phase microextraction for the evaluation of fiber-sample partition coefficients of pesticides
Language: English
Abstract:

A depletion solid-phase microextraction (SPME) method for the characterisation of SPME sorption for 13 pesticides selected as probe compounds is described. The sample is extracted and analysed multiple times by SPME-GC/MS. The observed depletion in peak areas is used for the calculation of extraction ratios that varied between 3 and 28% for a PDMS fiber with confidence intervals between 0.7 and 5.4%. Apparent fiber-sample partition coefficients can be calculated and extrapolated to equilibrium conditions if specific sorption kinetics are known. Under the chosen conditions, problems were encountered for more polar compounds (log Kow < 3) due to inefficient extraction. The extracted amount was found to be the decisive parameter for depletion SPME and the extraction conditions therefore need to be adapted to the polarity of the analyte. The importance of the initial analyte concentration especially for mixed-mode fibers is demonstrated. Compared with conventional external calibration using liquid injection, depletion SPME eliminates uncertainties due to solvent effects during injection. Furthermore, it does neither require authentic reference compounds nor knowledge of the initial analyte concentration, and thus can even be used for unknowns.

Journal or Publication Title: Journal of chromatography A
Volume: 1102
Number: 1-2
Publisher: Elsevier
Uncontrolled Keywords: Solid-phase microextraction; Partition coefficients; Pesticides; Extraction ratios; Depletion
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Material Analytics
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 20 Nov 2008 08:26
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