Reducing the effects of system contamination in PFAS analysis

Using the ExionLC 2.0 system

Simon Roberts,1 Adrian M. Taylor2


Because of the pervasive nature of PFAS and the suggested PFAS detection limits continuingly being decreased in environmental sample analysis, there is an increasing need to have LC-MS strategies that can effectively manage PFAS background. Here, a workflow was established on the ExionLC 2.0 system with the optional wash system using delay columns to separate background PFAS contamination from sample analysis. An assay for 52 PFAS analytes was used to characterize the performance attributes of the LC system, including carryover. Analysis was performed using the SCIEX Triple Quad 7500 system to obtain very high sensitivity.



Per-- and polyfluoroalkyl substances (PFAS) are human made chemicals, developed to have resistance to grease, oil, water and heat. With these properties, PFAS are used in a wide range of consumer and industrial products, including stain and water-resistant fabrics and carpeting, cleaning products, paints, and firefighting foams. Limited use of certain PFAS has FDA approval to be used in cookware, food packaging and food processing equipment.

The strength of the C-F bond in PFAS makes natural degradation extremely difficult. The widespread use of PFAS and their ability to remain intact has caused increasing levels of environmental contamination over time from both past and current uses. This alarming accumulation rate has led to increased study of the potential environmental and health effects of PFAS. The resistance to degradation, however, also makes them a challenge to analyze because they are prevalent contaminants in analytical instrumentation. With guidance for PFAS concentrations continuingly decreasing the limits, there is an increasing need to manage the background levels in the analytical instrumentation used. This would allow an accurate measurement of PFAS amounts in environmental samples.

Here, the ExionLC 2.0 system with the optional wash system was investigated for its flexibility in minimizing background contamination of PFAS for LC-MS/MS analysis when analyzing PFAS containing samples. A SCIEX Triple Quad 7500 system coupled with an ExionLC 2.0 system was chosen as the highly sensitive test platform to investigate meeting a <0.05% carryover performance requirement after 1 ppb standard and a blank contamination <2.5 ppt for 52 PFAS compounds.

Figure 1. Carryover analysis. Blank extracted ion chromatogram for PFECHS showing extremely low contamination in blank samples (pink trace) analyzed immediately following the injection of the highest calibration standard of 10,000 ppt, overlaid with the LLOQ standard 2.5 ppt (blue trace).

Key features of the ExionLC 2.0 system

  • Flexibility in wash solvent selection and flow rate options for extended needle wash capabilities to minimize carryover, which reduces false positive rates and the need for repeat extractions and re-injections
  • Ability to customize the system and optimize the cleanup of all autosampler solvents to reduce system contamination to a minimum, allowing accurate determination of PFAS even at low levels
  • Accurate and precise quantification results with linear coefficient of determination performance (r2) > 0.99, precision <10% coefficient of variation and asymmetry factors between 0.8 and 1.5
  • Sensitive minimum reporting limits as low as 2.5 ppt with a calibration range 2.5-10,000 ppt (3.6 orders of magnitude LDR)