Simple Modification of Liquid Chromatographic System to Reduce Perfluorinated Alkyl Acids (PFAAs) Background for EPA Method 537

Poster Presentation

Prepared by L. Sanchez, L. Yoo, M. Weiner, A. Lau
Orange County Water District, 18700 Ward Street, Fountain Valley, CA, 92708, United States

Contact Information: [email protected]; 714-378-3344


Concern about the presence of PFAAs in the environment and groundwater prompted federal program UCMR3, using EPA Method 537 to look for 6 PFAAs -- PFOA, PFNA, PFHpA, PFOS, PFHxS and PFBS at a low (Method Reporting Limit) MRL from 0.01 to 0.09 ppb. Due to the fact that PFAAs occur in a wide range of products i.e. laboratory supplies and equipment, such as PTFE (polytetrafluoroethylene) product, Liquid Chromatography (LC) solvent lines, aluminum foil, etc.; it was a challenge for our lab to perform the method’s Initial Demonstration of Capability (IDC) and bring on line method 537 mainly caused by high concentration of PFAAs background interferences. During IDC study, we found that the LC system contributes a significant background of PFOA, PFNA and PFHpA to the final product causing failure to meet Quality Controls (QCs) criteria. While it’s not practical for us to replace all LC’s parts and tubing with stainless steel, we needed an alternative way to minimize the PFAA background. To solve this problem, we follow Waters Corporation’ Principal - “Modification of LC Set Up”. A second shorter column that has the same phase as the analytical column is placed between the mobile phase mixing chamber and sample injector to achieve our goal. We compare the percent recovery of PFOA, PFNA and PFHpA using conventional LC set up versus modified LC set up. The analytical results showed the modified LC set up reduces the PFAA background drastically, produces more reliable and consistence recovery for the problem compounds. The modified LC set up method therefore solved our PFAA background problem. We were able to meet the EPA 537 IDC QCs requirement and achieve the low level concentration required by UCMR3 without further problem.