For the next couple of blog posts, I will be covering LC-MS in more detail, as it is a complex analytical technique that is hard to explain within a short blog post.
I will start off with liquid chromatography (LC). Within the context of LC-MS, it is a technique that separates the components of a sample for analysis.
Even though liquid chromatography has many different methods, we are focusing on high-pressure liquid chromatography (HPLC). HPLC is used in the official PFAS testing methods by the EPA. The procedure is as follows:
1. Solvents from reservoirs are degassed for removal of dissolved oxygen
2. Solvents are fed into high-pressure pumps and mixed.
3. The sample to be analyzed is injected into the mixture.
3. The mixture of organic solvents (called the mobile phase) is pumped at high pressure throughout the liquid chromatography system into a filter-like apparatus called an analytical column.
The analytical column essentially acts as a filter for the physical components of the liquid sample. Larger components will flow slower through the filter, getting stuck on the bits of the stationary phase, while smaller components will pass through faster. This allows the separated parts to sequentially exit the chromatography system and allows them to be individually analyzed and counted.
The flow of the solvent is important in maintaining the proper separation of components in the analytical column. The separation of components allows different parts of a solution to be measured accurately by mass spectrometry.
Sources
https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Instrumental_Analysis/Chromatography/Chromatographic_Columns
http://hiq.linde-gas.com/en/analytical_methods/liquid_chromatography/high_performance_liquid_chromatography.html
https://static1.squarespace.com/static/54d9087ce4b058d3cfb44d78/t/58efcd7fb3db2bed6e7f0712/1492110732957/%2326+Expand+Your+Lab+with+the+Use+of+Mass+Spectrometry.pdf