The GC is used to analyze volatile molecules with a high melting point, such as fatty acids in fish oil. In addition, samples submitted to the GC do not need solvents or a “liquid mobile phase.” Instead, samples are carried by an inert gas through the system. Hence, if we are testing for solvents, the instrument of choice is the GC‑FID/MS. No steps are needed to factor out any solvents used to prepare the sample.
GC‑MS is precisely able to identify and determine the quantity of the molecules of interest, whereas, GC‑FID is only used to determine the quantity of molecules. Like LC‑MS/MS, GC‑MS is also able to create an electronic signature of a molecule. The complexity of running the test will dictate which instrument will be used.
In a GC system, the vaporized sample is moved with a carrier gas through a specially coated capillary column. The column separates the components before entry into the detector; in our case, either the FID or MS, depending on the application.
We also use the GC‑FID system to determine the quantity of common fatty acids as well as essential oils present in oils such as tamanu, argan, and fish oil.
PCBs and pesticides are tested for through the GC‑MS. As the samples pass through the ionization chamber, they are bombarded with a very high voltage of electricity that results in complete fragmentation (separation) of the individual compounds. The fragments are reconstructed as they move through a vacuum tube as per their mass-to-charge ratio. The given signal is recorded by the computer for analysis.
The compounds are compared with a well-known library from the National Institute of Standards and Technology (NIST) or a certified reference standard material.