3.3.5. Coupled gas chromatography-electroantennographic detection (GC-EAD) recording

In this continuous recording system, the stimulus (a natural extract or synthetic mixture of chemicals is applied by injection into a gas chromatograph where individual components are separated based on their physical and chemical properties while being carried through a column (see section 2.2.3.). One part of the column effluent is continuously flushed over the antenna while the other flows into the flame ionisation detector (FID).

  1. Switch on the GC and programme it to run a specified separation method (see section 2.2.4. on In situ volatile collection) and wait for it to get ready.
  2. Following successful antennal preparation, inject 1-5 μl of the extract depending upon its concentration into the GC through its injection port and run the method.
  3. At the same time start the recording programme on the computer to synchronise the signal output of the GC’s sensor (FID) with that of the EAD setup (antenna).
  4. Allow the program method to run from start to finish. When the run is over, stop the recording and save the file on the PC. The file can then be retrieved later for analysis.
  5. The recorded file contains two line tracings, the FID and EAD outputs (Fig. 6a).

Peaks on the FID trace represent the different chemical components separated on the column and detected by the FID, while those corresponding to EAD peaks indicate antennal detection to specific compounds.

 

Fig. 6a. A continuous GC-EAD output showing antennal responses labelled 1-5 to a mixture of 6 chemicals. Notice that the peak representing a chemical (impurity) between peaks d and e is not detected by the antenna.

figure6a

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