Selectable one-dimensional or two-dimensional gas chromatography–olfactometry/mass spectrometry with preparative fraction collection for analysis of ultra-trace amounts of odor compounds

Abstract

A novel selectable one-dimensional ( 1D) or two-dimensional ( 2D) gas chromatography–olfactometry/mass spectrometry with preparative fraction collection (selectable 1D/ 2D GC–O/MS with PFC) system was developed. The main advantages of this system are the simple and fast selection of 1D GC–O/MS or 2D GC–O/MS or 1D GC-PFC or 2D GC-PFC operation with a mouse click (without any instrumental set-up change), and total transfer of enriched compounds with thermal desorption (TD) on the same system for identification with 2D GC–O/MS analysis. Recovery of PFC enrichment with 20 injection cycles of 15 model compounds at 500 pg each (e.g. alcohol, aldehyde, ester, lactone, and phenol) was very good with recoveries in the range of 98–116%. The feasibility and benefit of the proposed system was demonstrated with an identification of off-flavor compounds (e.g. 2,4,6-trichloroanisole (TCA), 2-isobutyl-3-methoxypyrazine (IBMP), and geosmin) in spiked wine at odor perception threshold level (5–50 ng L −1). After parallel stir bar sorptive extraction (SBSE) for 20 aliquots of a sample and subsequent PFC enrichment for the odor-active fractions from the 20 stir bars, three off-flavor compounds were clearly resolved and detected with TD– 2D GC–O/MS in scan mode. The good efficiency of SBSE-PFC enrichment in the range of 71–78% shows that all analytical steps, e.g. SBSE, TD, 1D/ 2D GC–O/MS, and PFC, are quantitative and identification of off-flavor compounds at ng L −1 level in wine is possible.