Identification of three novel compounds in wine by means of a laboratory-constructed multidimensional gas chromatographic system

Abstract

A laboratory-made off-line multidimensional GC–GC system has been optimized and applied to the isolation and identification of three novel aroma compounds in wine. The system comprises two independent chromatographs equipped with four-port manually actuated valves and fast capillary connectors that make it possible to quickly transfer a capillary trapping loop from the first to the second system. The first system includes a split/splitless injector, a thick phase semi-capillary column, the valve and both a flame ionization detection (FID) system and a sniffing port. The trapping loop lies outside the chromatograph and it is immersed in a Dewar with liquid nitrogen. The second system includes a programmable temperature vaporization (PTV) injector, the valve, the analytical column and two parallel detectors (a MS system and a sniffing port). The injection of large sample volumes (90 μl) in the first GC system and the general operation of the system have been optimized. The extract was obtained by purging the wine at 37 °C with a stream of nitrogen and trapping the volatiles in a bed containing 1 g LiChrolut EN. Fatty acids and alcohols were removed by washing the resins with a water/methanol solution containing 1% NaHCO 3, and volatiles were recovered with dichloromethane. The GC–MS analysis of the cuts obtained in the first GC system made it possible to identify by first time in wine the strong smelling compounds ethyl 2-, 3- and 4-methylpentanoate.