Determination of perfluorooctanoic acid and perfluorooctanesulfonate in human tissues by liquid chromatography/single quadrupole mass spectrometry

A method is described that permits the measurement of the levels of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in human liver, kidney, adipose tissue, brain, basal ganglia, hypophysis, thyroid, gonads, pancreas, lung, skeletal muscle and blood, even in subjects not occupationally exposed to these compounds. The purification of samples involved the use of trifunctional (tC18) and strong anion-exchange (SAX) solid-phase extraction cartridges, and the analysis utilized a high-performance liquid chromatograph coupled to a single quadrupole mass spectrometer (LC/MS). The analyses were conducted on a mixed-bed reversed-phase column by gradient runs using 3 mM ammonium acetate/methanol mixtures at different proportions as the mobile phase. The detector was used in electrospray negative ion mode by recording simultaneously the ions m/z 413.0 (PFOA) and 499.0 (PFOS). Perfluorononanoic acid (PFNA), added to the samples before the purification, was used as the internal standard (ion monitored = m/z 463.6). The recovery rates of the extraction procedure ranged from 79.6 to 95.6% (CV% 1.7-7.4%) for PFOA, from 79.7 to 100.8% (CV% = 1.2-7.1) for PFOS, and from 89.1 to 102.3% (CV% = 0.9-5.2 %) for PFNA. The calibration curves were linear up to at least 400 ng of analytes per gram of tissue. The detection limits (signal-to-noise ratio = 3) were 0.1 ng/g for both PFOA and PFOS measured in all tissues except adipose tissue, where the limits were about 0.2 ng/g. The content of analytes in tissues varied from 0.3 to 3.8 ng/g (respectively: basal ganglia and lung) for PFOA, and from 1.0 to 13.6 ng/g (respectively: skeletal muscle and liver) for the linear isomer of PFOS. The method is suitable to evaluate the content of PFOA and PFOS in different tissues taken from the general population exposed to very low concentrations of these pollutants.