GC-EAD is gas chromatography method in which a unique biological detector, based on living insect antenna, is used as one of two detection systems. GC-EAD is an analytical method which offers very fast and reliable identification of compounds in complex natural mixtures that stimulate the olfactory sensilla of insect antennae. In other words, the GC-EAD help to discover what specific chemicals in tested mixture an insect can smell, respective, which compound elicits the electric antennal response.
A standard GC-EAD system
(S) Splitter - column effluent is split in two halves; (D1) FID produces a signal proportional to the amount of volatile in the column effluent; (D2) EAD detection - with air mixed column effluent is blown over an insect's antenna; (PC) combined FID/EAD chromatogram.

It has been known for more than 50 years that the electric potential difference (voltage) measured by two tiny microelectrodes between the tip and the base of an insect's antenna changes measurably when the antenna is exposed to compounds of biological significance for the insect. This voltage represents the sum of potentials of all responding olfactory neurons around the recording electrode, and the voltage's amplitude approximately corresponds to an insect's sensitivity to a particular compound. The voltage produced by an antenna can be easily amplified, measured and recorded together with corresponding data delivered by a classical FID detector. The GC-EAD system is in principle very simple apparatus based on a standard chromatograph with FID detector. The only important change is a post-column splitter followed by doubled detection system. After the separation is the column effluent split in two parts, with the first half transported to a FID detector and the other one transmitted to the EAD detector. The effluent is cooled by mixing with purified air and blown over a live insect antenna attached to a high impendence amplifier. The amplified electrical signals of both detectors are subsequently digitized, processed and recorded simultaneously against the time (see scheme).

GC-EAD system with Agilent 7890 GC

The new GC-EAD systems is based on state-of-art Agilent 7990 gas-chromatograph equipped by two capillary GC-columns and SYNTECH GC-EAD setup (amplifier, probe, effluent conditioner, stereomicroscope, four-arm splitter, micromanipulators etc.).

GC-EAD system with HP 5890 GC

The older GC-EAD system is based on HP 5890 gas-chromatograph equipped by one capillary GC-column and SYNTECH GC-EAD setup (amplifier, probe, effluent conditioner, four-arm splitter, micromanipulators etc.).