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PFAS Analysis – Why a Delay Column is Important

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Poly- and perfluoroalkyl substances, or PFAS, are rapidly emerging as some of the most important environmental contaminants to monitor around the world. Their widespread use and environmental persistence make them truly a global issue. Concerns about possible health risks are driving environmental scientists to look for these compounds everywhere. However, one other concerning place where at least some of these compounds are present is inside the very instruments used for PFAS analysis of environmental samples. PFAS delay columns can be used to manage this type of contamination. 

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It seems there is growing interest in PFAS every day. PFAS is an acronym for per- and polyfluorinated alkyl substances and they are most often analyzed by LC-MS/MS. But, this analysis has some challenges.  

Let’s start with a little bit of information on PFAS. These fluorinated compounds started to see use in the 1940s and have since been used in a wide array of products and processes including nonstick products, such as kitchenware and fast food packaging, outdoor clothing, stain-resistant carpet spray, AFFF (aqueous film-forming foam) used in firefighting and many more. Concerns about PFAS began to develop as research started to show that these compounds are very persistent in the environment and could be associated with adverse health effects. Accordingly, interest has rapidly grown in testing for these compounds. When we are in the lab doing PFAS analysis, we still have to be aware of how widespread PFAS can be. PTFE (polytetrafluoroethylene) is found throughout a typical lab and can contribute trace PFAS contamination. Most LC-MS/MS instruments have PTFE components and they can slowly leach out interfering with our PFAS analysis. It’s continuously feeding interfering compounds at low levels in to your analysis. However, there is an easy solution: a PFAS delay column. Just as the name implies, it delays PFAS, specifically the residual PFAS contamination introduced before the injector in your LC-MS/MS.

In a typical LC-MS/MS, PTFE tubing is fairly common in mobile phase lines, so the potential interference flow path starts at the very beginning: the mobile phase. From the mobile phase bottle it flows into the degasser with multiple PTFE-containing lines, and then to the LC pump where you can also find PTFE parts. Next is our mobile phase mixer and now, here, between the mixer and the sample injector, is where we will install the PFAS delay column. A PFAS delay column is not an analytical column and does not separate the PFAS compounds in your sample, so don’t get confused with where you install this column. You’ll still need your analytical column to resolve your analytes. By adding the delay column, we prevent the PFAS introduced upstream of the injector from coeluting with the sample by temporarily trapping them. Accordingly, when we inject a sample the sample PFAS will elute first and the contaminant material will elute later. Because of the prevalence of PFAS, we have to take some measures to manage PFAS contamination to ensure the integrity of our data. A PFAS delay column, correctly installed between the mobile phase mixer and the sample injector, delays the system-related interference for accurate measurement of PFAS in your sample.  

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