Scholarly
    Communications Project


Document Type:Dissertation
Name:Yuwen Wang
Email address:ywang@vt.edu
URN:1998/00066
Title:SAMPLE PREPARATION/CONCENTRATION FOR TRACE ANALYSIS IN GC/MS

(A study of solid phase microextraction and headspace sampling)

Degree:Doctor of Philosophy
Department:Chemistry
Committee Chair: Harold M. McNair
Chair's email:hmcnair@vt.edu
Committee Members:John G. Dillard
James O. Glanville
Gary L. Long
Mark R. Anderson
Keywords:sample preparation/concentration, trace analysis, GC/MS, SPME, MAE
Date of defense:December 11, 1997
Availability:Release the entire work for Virginia Tech access only.
After one year release worldwide only with written permission of the student and the advisory committee chair.

Abstract:

Solid Phase Microextraction (SPME) associated with Microwave Assisted Extraction (MAE) (1-3) , on-line headspace derivatization (4-6) and the selectivity of different SPME coatings (7) were studied. Trace amounts of Veltol, Veltol Plus and short chain fatty acids in food samples were analyzed by GC/MS.

Since SPME is not directly applicable to solid samples, SPME associated with MAE techniques was studied for solids, primarily food samples. The efficiency of classical solvent extraction and MAE was compared. The parameters which affect SPME, were optimized for the determination of Veltol and Veltol Plus in food products such as potato chips and coffee. The technique gave a detection limit of 2 ppb for Veltol Plus which is 200 times more sensitive than conventional GC technique.

Headspace injection is characterized by simple and easy handling of complicated solid and solution matrices. Headspace injection, however, is not suitable for high molecular weight substances or non-volatile compounds. An on-line derivatization headspace technique was studied for short chain fatty acids. These samples are difficult to do by classical GC. The developed technique simplified the conventional derivatization procedures and combined the sample preparation and GC/MS analysis into one step. The thermostatting temperature, time, solvent and matrix effects were investigated. Low calorie fat and some agricultural samples were analyzed. The detection limit for acetic acid is 8 ppb.

SPME is a novel sample introduction technique. The behavior of di(methylsiloxane), polyacrylate and Carbowax coatings on SPME fibers for compounds having different functional groups were investigated. The selectivities of the coating, sample pH and the sample temperature were investigated.


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