Simultaneous characterization of perfluoroalkyl carboxylate, sulfonate, and sulfonamide isomers by liquid chromatography-tandem mass spectrometry.
A comprehensive method was developed to simultaneously separate and detect perfluorinated acid (PFA) and PFA-precursor isomers using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A linear perfluorooctyl stationary phase and acidified mobile phase increased separation efficiency, relative to alkyl stationary phases, for the many perfluoroalkyl carboxylate (PFCA), perfluoroalkyl sulfonate (PFSA), and perfluorooctyl sulfonamide (PFOSA) isomers and in combination with their distinct MS/MS transitions allowed full resolution of most isomers in standards. Utilizing the absence of the "9-series" and "0-series" product ions, several perfluorooctane sulfonate (C8F17SO3-, PFOS) isomers were structurally elucidated. In human serum, only perfluorooctane sulfonamide (C8F17SO2NH2, FOSA) and PFOS consisted of significant quantities of branched isomers, whereas PFCAs were predominantly linear. Interferences that coelute with the m/z 499 --> 80 transition of PFOS on alkyl stationary phases were simultaneously separated and identified as taurodeoxycholate isomers, removal of which permitted the use of the more sensitive m/z 80 product ion and a resulting 20-fold decrease in PFOS detection limits compared to the m/z 499 --> 99 transition (0.8 pg versus 20 pg using m/z 80 and 99, respectively). Interferences in human serum which caused a 10-20-fold over-reporting of perfluorohexane sulfonate (C6F13SO3-, PFHxS) concentrations on alkyl stationary phases were also simultaneously separated from linear PFHxS and identified as endogenous steroid sulfates. PFOSA isomers, generated with human microsomes, had different rates of metabolism, suggesting that the perfluoroalkyl branching pattern may affect the biological properties of individual isomers. This fact, and for reasons of improved accuracy and sensitivity, investigators are urged to utilize more efficient separation methods capable of isomer characterization in perfluoroalkyl research.
Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, 10-102 Clinical Sciences Building, University of Alberta, Edmonton, AB, Canada.
Jonathan P
JP
Benskin
Mahmoud
M
Bataineh
Jonathan W
JW
Martin
D000478:Alkylation; D002264:Carboxylic Acids / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000379:methods*; D005461:Fluorine / Q000737:chemistry*; D006801:Humans; D007536:Isomerism; D015394:Molecular Structure; D044967:Serum; D013449:Sulfonamides / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry*; D053719:Tandem Mass Spectrometry / Q000379:methods*
D002264:Carboxylic Acids; D013449:Sulfonamides; D013451:Sulfonic Acids; D005461:Fluorine