In this study, a method for simultaneous determination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in paper-based food packaging was validated. The paper samples were extracted with ethanol/water (1 : 1, v/v) mixture at 70°C for 2 h by using an incubator shaker. The extracts were passed through 0.2 μm filters before LC-MS/MS analysis. The method detection limit and method quantification limit of both PFOA and PFOS were 0.1 and 0.3 ng/g, respectively. Correlation coefficients > 0.99 were obtained over concentration ranges from 0.3 to 10 ng/mL. The method recovery ranged from 100 - 106% with good repeatability (RSD < 5%). The method was applied to analyze 23 paper samples, however, PFOA and PFOS were not detected in any of these samples.

Contamination levels of two typical perfluoroalkyl substances (PFASs) including perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were evaluated in Vietnamese fish samples by using our monitoring results and database reported in previous studies. In freshwater fish taken from West and Yen So Lakes (Hanoi), PFOS and PFOA concentrations ranged from < 0.030 to 0.48 (mean 0.12) ng/g, and from < 0.010 to 0.19 (mean 0.058) ng/g, respectively. These levels were comparable to those measured in fish samples from other areas in Vietnam, but were generally lower than values documented for fish samples from other countries. PFOS and PFOA daily intake doses via fish consumption ranged from 0.015 to 0.48 (mean 0.12) and from 0.005 to 0.20 (mean 0.065) ng/kg/day. In general, these intake doses were lower than the reference dose of 20 ng/kg/day, suggesting acceptable levels of risk.