Quantification of Perfluoroalkyl Substances (Pfas) in Drinking Water By Solid Phase Extraction and Lc-Ms/Ms

Date of Award

2-1-2023

Document Type

Thesis

Degree Name

Master of Science in Chemistry

First Advisor

Ian Ken D. Dimzon, PhD

Abstract

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are compounds with the same aliphatic carbon backbone where hydrogen atoms are either completely substituted or partially substituted by fluorine. PFAS’ general characteristics include heat resistance, can withstand acids, bases, reducing agents, and oxidants, as well as photolytic, microbial, and metabolic degradation processes. As a result, it has a wide range of applications, from household items to fast food wrappers, causing these chemicals to be very persistent in the environment and end up in the human body.

The research aimed to determine the presence of the following perfluoroalkyl substances (PFAS): perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA), perfluorooctane sulfonate (PFOS), and perfluorohexane sulfonate (PFHxS), in samples collected from refilling stations and household tap water around five communities/barangays near Quezon City’s water treatment plants.

To extract the analytes, the water samples were spiked with internal standard and were passed through the SPE cartridge containing polystyrene divinylbenzene (SVDB). The extracts were concentrated to dryness using nitrogen gas, reconstituted with 50:50 methanol: water to a 1mL volume, and were further cleaned up by using syringe filters. The samples and standards were analyzed by Liquid Chromatography with Tandem Mass Spectrometry (LC-MS/MS) with a C-18 column as the stationary phase and methanol/ammonium acetate as the mobile phase under a specified condition.

The results proved the presence of PFHxA with concentrations ranging from 2.2 to 7.3 ng/L and PFOA with concentrations ranging from 0.5 to 7.9 ng/L, while PFOS and PFHxS were both not detected in all samples. The summation of detected PFAS in

tap water is greater than the total PFAS in refilling stations, which infers a reduction of the compounds in this treatment level. PFHxA is more effectively removed, while PFOA concentrations between the two types of samples have no significant difference. For the results of point-of-use (POU) filters, the percent removal of pitcher filter is at least two-fold more effective than faucet-mounted filters for the first 100 mL.

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