Gas chromatography at UVA

What a lovely and interesting day I had in the UVA!

Peter Roessingh is a teacher and researcher at the Faculty of Natural sciences, mathematics & computation at the UVA.

In his lab, you can find a set ready to study moths and flies. He uses GC to study the plant odors, to see what they produce that attacks or repels insects, and pheromones produced and used by the moths for attracting and finding partners, courtships, and making mating decisions.

He has an old gas chromatographer which takes lots of machine understanding to run a gas analysis.

Besides the GC he has a set-up called Electro Antenogram (EAG). The Electroantennography is technique for measuring an output from an insect antenna to certain odor. The EAG is directly connected to either the GC or to another setting where you can pump a scent directly to the antenna, and also clean air.

I was fascinated by the air running through a beautiful glass bottle filled in with carbon. Carbon seems to be very porous material and captures all sort of things you don’t want to have in a clean air!

The GC is composed by a column (like a really loooong and thin crystal tube spiral) whith an internal coating (which can be from different materials). This coating will be the one responsible to keep certain odor molecules longer in their porous. The ones not fitting will abandon the column at a higher speed.

It is important to program properly the temperature of the “oven”, where the coil is placed. Depends on the mixture you use you will program different asset of temperatures. We used a 3min run at 95ºC to later inject the scent. Then the temperature goes up 6ºC per minute up until 293ºC.

The scent molecules are burned by the end of the route. When burning there will be an electrical signal produced. The electrical signal will give us information on how mach molecules are there and at what time are they leaving the column. When you need to know which exact molecule you will need another process and machinery, a mass spectrometer.

The GC EAG is very useful in order to learn which molecules are biologically important, so that you don’t need to study all of them. It is a time and work saver!

The GC is connected to an amplifier and later to a computer. The computer runs software which will show you at real time a graphic (voltage/time).

During my visit to Peter’s lab we did 4 GCies.

1. A first one with only Hexane: this is like a cleaning procedure. Also hexane will be the solvent of any other smell we want to analyze.

2. Cis-3-eha-1-ol: well know molecule for grass smell.

3. Grob mixture: this is one of the premade mixtures in order to see if the machine is working properly. This means that you have already a graphic result to compare your results with.

4. Alkaline Mixture (Aliphatic Hydrocarbon Standard): another mixture to check out if you machine is properly in tune.