Development of a Chromatography System for Simultaneous Measurement of Atmospheric Gas Components: Use in Measurement of Oxygen, Carbon Dioxide, Nitrogen, Argon, and Ethylene within Individual Fruit a

摘要

A gas chromatographic (GC) system was developed to determine oxygen (O_2), argon (Ar), carbon dioxide (CO_2), nitrogen (N_2), and ethylene simultaneously. The system consists of a GC equipped with one thermal conductive detector (TCD), one flame ionization detector (FID), one split/splitless inlet, and one packed column inlet. The system uses porous polymer and molecular sieve capillary columns to perform the separation of the gaseous species. A gas sample is introduced by a two-position valve fittedwith two sample loops, to two flow paths within the GC. One path goes directly from the packed inlet, through a styrene divinylbenzene column to the FID to detect ethylene. The other goes through the split/ splitless inlet, which is fitted with two separate columns, one to separate and detect CO_2, and another to separate Ar, O_2, and N_2 before detection by the TCD. The subsystem for the Ar, O_2, and N_2 separation contains a protection column (pre-column) and a separation column (molecular sieve) separated by a two-position valve. The valve is switched before the water and CO_2 elute from the pre-column and go into the molecular sieve column. Water and CO_2 would cause deactivation of the molecular sieve column. The entire run takes less than 12.8 min. This system has been used for the analysis of internal gas composition in fruit coated with different waxes, monitoring of gas combination in controlled atmosphere storage rooms, and other applications. It is a key tool to conduct individual fruit physiology and quality research, and for finding direct correlation between internal gases and fruit physiological metabolism and quality.