An ultra-sensitive method for the analysis of perfluorinated alkyl acids in drinking water using a column switching high-performance liquid chromatography tandem mass spectrometry

- Analysis of 14 PFAAs in drinking water using an off-line solid phase extraction (SPE) pre-treatment followed by an on-line pre-concentration on a WAX column before analysis on column-switching HPLC-MS/MS.
- A sufficiently sensitive method was developed using very small sample volume (10 mL) with nanogram per liter (ng/L) detection limits.
- The lowest concentration minimum reporting levels ranged from 0.59 to 3.4 ng/L for 14 PFAAs.
- Recoveries for most of the PFAAs in laboratory fortified matrix samples ranged from 73 ± 14% to 128 ± 5%.

In epidemiological research, it has become increasingly important to assess subjects' exposure to different classes of chemicals in multiple environmental media. It is a common practice to aliquot limited volumes of samples into smaller quantities for specific trace level chemical analyses. A novel method was developed for the determination of 14 perfluorinated alkyl acids (PFAAs) in small volumes (10 mL) of drinking water using off-line solid phase extraction (SPE) pre-treatment followed by on-line pre-concentration on a WAX column before analysis on column-switching high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). In general, large volumes (100-1000 mL) have been used for the analysis of PFAAs in drinking water. The current method requires approximately 10 mL of drinking water concentrated by using an SPE cartridge and eluted with methanol. A large volume injection of the extract was introduced on to a column-switching HPLC-MS/MS using a mix-mode SPE column for the trace level analysis of PFAAs in water. The recoveries for most of the analytes in the fortified laboratory blanks ranged from 73 ± 14% to 128 ± 5%. The lowest concentration minimum reporting levels (LCMRL) for the 14 PFAAs ranged from 0.59 to 3.4 ng/L. The optimized method was applied to a pilot-scale analysis of a subset of drinking water samples from an epidemiological study. These samples were collected directly from the taps in the households of Ohio and Northern Kentucky, United States and the sources of drinking water samples are both surface water and ground water, and supplied by different water distribution facilities. Only five PFAAs, perfluoro-1-butanesulfonic acid (PFBS), perfluoro-1- -hexanesulfonic acid (PFHxS), perfluoro-1-octanesulfonic acid (PFOS), perfluoro-n-heptanoic acid (PFHpA) and perfluoro-n-octanoic acid (PFOA) are detected above the LCMRL values. The median concentrations of these five PFAAs detected in the samples was ≤4.1 ng/L with PFOS at 7.6 ng/L and PFOA at 10 ng/L. Concentrations of perfluoro-1-decanesulfonic acid, PFDS and other perfluoroalkyl carboxylic acids were below the LCMRL values.