Determination of perfluorooctane sulfonate and perfluorooctanoic acid in human plasma by packed capillary column switching coupled to micro-ESI-TOF-MS

Abstract

ABSTRACT

The present work displays capillary liquid chromatographic column switching methodology tailored for fast, sensitive and selective determination of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in human plasma using µ-electrospray ionization time-of-flight mass spectrometric detection. 50 µL plasma samples were diluted five times and underwent protein precipitation with TCA. The supernatants were loaded onto a 320 µm I.D. x 30 mm 10 µm Kromasil C18 pre-column, providing on-line sample clean-up and analyte enrichment, prior to back-flushed elution onto a 320 µm I.D. x 150 mm 3.5 µm Kromasil C18 analytical column. Loading flow rates up to 150 µL/min in addition to the use of an acetonitrile/water gradient containing 10 mM ammonium acetate provided a total analysis time of 12.5 minutes. Ionization was performed in the negative mode and PFOA was observed as [M-H] - at m/z 413.3 and [M-CO2-H]- at m/z 369.4. PFOS was observed as [M-H] - at m/z 499.2. The method was validated over the concentration range of 5-1250 ng analyte/mL plasma, yielding linearity correlation coefficients of 0.9964 and 0.9910 for PFOA and PFOS, respectively. The within-assay (n = 6) and between-assay (n = 6) precisions were in the range 1.9 - 20 % RSD and 9.6 -11.7 % RSD, respectively, and the recoveries were measured as 26.5% and 10.2 % for PFOA and PFOS, respectively. The mass limit of detection was 125 pg for both analytes, corresponding to a PFOA and PFOS concentration limit of detection of 0.1 ng/mL diluted plasma corresponding to 0.5 ng/mL plasma. The method was applied for the determination of PFOA and PFOS in a plasma sample obtained from a blood bank, but the compounds were not found above the detection limit.