United States Environmental Protection Agency (US EPA) Method 533 for the analysis of selected per- and polyfluorinated alkyl substances (PFAS) in drinking water is traditionally analyzed using liquid chromatography/triple quadrupole mass spectrometry (LC/TQ) for maximum sensitivity. This application note shows an instrument demonstration of the Agilent 6546 quadrupole time-of-flight LC/MS for the analysis of EPA Method 533 compounds to meet sensitivity levels and all performance criteria mentioned in Method 533, while also allowing users to perform screening of other PFAS or nontargeted identification of unknown and emerging PFAS with LC-Q/TOF.
The analysis of PFAS in Method 533 using LC/TQ including method parameters such as extraction recovery, method reporting levels, and precision are described in previously published application note 5994-1628EN. Method 533 requires solid phase extraction of 100 to 250 mL of drinking water, followed by solvent exchange to 1 mL of 80% methanol, which is then analyzed by LC/TQ. This application note replaces only the detector and uses an LC/Q-TOF instead of TQ to show performance criteria for EPA Method 533 can be met with the Agilent 6546 LC/Q-TOF.
A quadrupole time-of-flight (Q-TOF) is a high-resolution accurate mass instrument that allows unambiguous identification of chemical formulas using mass accuracy. A Q-TOF can also be used for quantitation of a targeted list of compounds due to their ability to acquire data at high acquisition rates without loss in mass resolution, unlike trap-based high-resolution instruments. High acquisition rates are critical when up to 20 data points are required across the peak for accurate, robust, and sensitive quantitation as usually done with triple quadrupole (TQ) instruments. High resolution can also be used for retrospective analysis of acquired data for detection of suspected or unknown compounds.
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