AbstractsBiology & Animal Science

Advances in solid-phase microextraction as sample preparation method for food analysis.

by Erica Aparecida Souza-Silva




Institution: University of Waterloo
Department:
Year: 2015
Keywords: Food; Coatings; Pesticides; Fruits; Gas Chromatography-Time-of-Flight Mass Spectrometry (GC-TOFMS); Solid-phase microextraction (SPME)
Record ID: 2058065
Full text PDF: http://hdl.handle.net/10012/9197


Abstract

Within all steps involved in the analytical process, sample preparation is considered the most time-consuming step. Therefore, substantial efforts have focused on the search for automated sample preparation strategies that minimize sample handling and errors associated with human interference. Solid phase microextraction (SPME) addresses well the necessity for simple and automated sample preparation, with the integration of sampling, extraction, clean up and instrumental introduction into a single step. In SPME, selective extraction of compounds takes place based on the degree of distribution of the analyte between the SPME coating and the sample matrix. For this reason, the correct choice of SPME coating for a given application has great influence on the acquisition of reliable analytical data. In spite of its great potential, the implementation of SPME in the analysis of complex matrices, such as food, has been hindered by the lack of suitable SPME coatings that possess compatibility with complex matrices while maintaining sufficient sensitivity for trace applications. The main problem resides in the fact that the most matrix compatible coating, PDMS, has limited extraction efficiency towards less hydrophobic analytes, whereas the coating that exhibits best extraction efficiency towards pesticides, in general, is PDMS/DVB. PDMS/DVB as a solid coating suffers from the attachment of matrix components onto the coating surface, known as fouling. Fouling does not only considerably shorten coating reusability, but it also causes significant changes in extraction efficiency, skewing the reliability of the data obtained. Therefore, in this thesis, a new approach to fabricate a matrix-compatible SPME coating for GC-based analysis of food matrices is presented. The developed matrix-compatible coating was evaluated for its reusability in complex matrices, namely grape pulp and Concord grape juice, as well as for its extraction capabilities towards various analytes bearing different physicochemical properties. First, a method to impart matrix-compatibility to commercially available solid SPME coatings was developed. The method consists of applying a thin layer of PDMS onto the solid coating, in this case PDMS/DVB. The main premise behind this approach was to create a coating that presents the matrix compatibility of PDMS, while maintaining the sensitivity obtained with PDMS/DVB. The reusability of the obtained PDMS-modified coating was evaluated in grape pulp, and rewarding results were obtained since the coating could be reused for over 100 extractions. Moreover, the PDMS-modified coating presented a similar extraction efficacy to that presented by the original PDMS/DVB coating towards the triazole pesticides, used as model analytes. The developed PDMS-modified coating was then employed to develop a simple and fast DI-SPME-GC-ToFMS method for determination of ten triazole fungicides in grapes and strawberries. The method was successfully validated, and the figures of merit obtained with the SPME method were compared to…