Question: How does a gass chromatography machine (gc-ms) work?

Gary Munnelly answered on 5 Nov 2018:

OK, I love this question because I had no idea what the answer was! Literally no clue! So I texted my cousin, Emer Browne, who is a pharmacist. She’s the real brains in the family.

This is her explanation:

“A gas chromatography machine is basically where you get your substance of interest and vaporize it and then use helium to carry your vapor through a column. The vapor will interact with the stationary solid material in the column to differing extents depending on the molecular structure of the molecule. Because different molecules pass through the columns at different rates you have a molecule specific retention time [basically each molecule that makes up the substance of interest will take a different amount of time to pass through the column].

This can be used to identify substances in a mixed material, but only if you have a reference material. It will only work for substances that will vaporize without degrading, so it can’t be used for everything, but it is very sensitive from my understanding.”

So in other words, a gas chromatography machine is used to figure out what molecules make up some substance you are interested in. You vaporize the substance and pass it through a column which contains a different, known substance whose molecular structure you do know. You can figure out what the unknown substance is made of by measuring how long it takes for each molecule of the vaporized substance to pass through the column.

Thanks for this question! I really enjoyed learning the answer 😀