Investigation of Perfluorooctanesulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA) Isomer Profiles in Naturally Contaminated Food Samples

The quantification of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in naturally contaminated (incurred) food samples requires careful consideration of the composition of branched and linear isomers in the samples and analytical standards. To gain a better understanding of the biases that may be present during analysis, multiple analytical standards and integration techniques were used to measure incurred PFOS (in milk, deer meat, and eggs) and incurred PFOA (in clams), with varying percentages of branched and linear isomers. The isomer profiles of reference materials from Exercise 3 of the National Institute of Standards and Technology (NIST) Food Nutrition and Safety Measurement Quality Assurance Program (FNSQAP) were also investigated. Samples with higher proportions of branched isomers showed greater quantification bias when using standards composed primarily of linear isomers and a decrease in the bias with a two-peak integration technique. Isomer profiles of food samples also gave further information about the sources and transformation pathways.