Evaluation of Cytiva™ syringe filters for PFAS analysis using EPA method 1633A

In this article, we present an evaluation of Cytiva™ syringe filters for PFAS testing workflows aligned with EPA Method 1633A. Because PFAS analysis requires ultra-trace sensitivity, minimizing contamination risk during sample preparation is essential. Using a modified protocol without the solid-phase extraction step, we evaluated Cytiva syringe filters with nylon, regenerated cellulose, and polyethersulfone membranes to determine whether they introduced detectable PFAS compounds or exhibited adsorption that could affect analyte recovery. Our results show that most syringe filters tested did not introduce detectable PFAS, and extracted internal standard (EIS) recoveries remained within acceptance limits. These findings indicate that Cytiva syringe filters can support EPA Method 1633A workflows, although additional studies are recommended to confirm performance under broader conditions.

Introduction

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic compounds widely used in industrial and consumer products due to their resistance to heat, water, and oil. According to the Agency for Toxic Substances and Disease Registry (ATSDR), PFAS have been used in items such as water-repellent clothing, stain-resistant fabrics, cosmetics, and firefighting foams (1). Their chemical stability means they persist in the environment and accumulate in living organisms due to their extreme resistance to degradation.

Growing concern over the environmental and health impacts of PFAS has led to increased regulatory attention. Exposure to specific PFAS compounds has been associated with elevated cholesterol levels, reduced immune response to vaccines, changes in liver enzymes, pregnancy-induced hypertension, and an increased risk of kidney and testicular cancer (2).

EPA method 1633A is a validated analytical protocol designed to detect 40 PFAS compounds in various environmental matrices including wastewater, surface water, groundwater, soil, sediment, and biological tissues (3). The method relies on solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to achieve high sensitivity and reproducibility. Given the method’s ultra-trace detection limits, it is essential to maintain strict control over every step of the sample preparation process for reliable results and compliance with regulatory standards. This includes filtration, which must be carefully evaluated to prevent any risk of contamination. While syringe filters themselves may not contain PFAS, they can contribute to contamination during PFAS testing due to PFAS adsorption or leaching. Studies show that different filter materials exhibit varying degrees of PFAS retention and potential contamination (4). Therefore, careful filter selection and proper rinsing protocols are crucial to minimize PFAS contamination and for accurate results in PFAS analysis. To address these concerns, we designed a study focused on filtration as a potential contamination source. Using a modified EPA Method 1633A approach, the study aimed to determine whether Cytiva syringe filters meet contamination control requirements for PFAS workflows and are suitable for use in regulated environments.

Materials and methods

To assess filtration as a potential contamination source, testing was conducted in the United States by Weck Laboratories, Inc., an ISO/IEC 17025-accredited analytical laboratory with additional DoD ELAP and DoE certifications using LC-MS/MS on an Agilent Ultivo instrument (5).

A modified EPA Method 1633A protocol was applied, excluding the solid-phase extraction step to focus on filtration as a potential contamination source. Multiple syringe filter types were assessed across different membrane materials nylon, regenerated cellulose, and polyethersulfone. Product ranges used include Puradisc™, Acrodisc™, Acrodisc™ PSF, and Whatman GD/X™ filters (Table 1).

Table 1. Cytiva syringe filters evaluated for PFAS contamination using a modified version of EPA Method 1633A

Most products were evaluated across three separate lots, using one filter from each lot for analysis. Puradisc nylon and Whatman GD/X regenerated cellulose were evaluated in only two lots due to availability. Since Puradisc, Acrodisc, and Acrodisc PSF filters use a single membrane, Whatman GD/X filters were included to confirm that their glass microfiber (GMF) prefilter layers, designed to reduce clogging and improve sample throughput, do not introduce PFAS contamination.

In addition to native PFAS determination, EIS compounds were monitored as part of method performance checks in accordance with EPA Method 1633A. Isotopically labeled PFAS EIS compounds were added to each sample at known concentrations prior to sample preparation and were processed through filtration and LC‑MS/MS analysis alongside the native PFAS compounds. Because EIS compounds are close structural analogs of the target analytes and experience the same sample preparation steps, their measured recoveries provide supporting information on potential PFAS losses during filtration and subsequent preparation steps. Acceptable EIS recoveries therefore support that the syringe filter step did not introduce bias through analyte adsorption or analytical interference.

Results and discussion

Results were evaluated against EPA Method 1633A performance expectations, including MDL (method detection limit) and MRL (minimum reporting level), and adhered to the laboratory’s MRL convention to ensure consistency with regulatory standards.

Tables 2 and 4 summarize PFAS detection results across different membrane types (nylon, regenerated cellulose, polyethersulfone) and syringe filter product families (Puradisc, Whatman GD/X, Acrodisc and Acrodisc PSF filters).For each compound, the tables report either the highest concentration detected among all tested lots or ‘ND’ (not detected) if PFAS was below the MDL in every lot.

EIS recoveries within standard acceptance windows are detailed in Tables 3 and 5. They were calculated as the average across all tested lots and served as internal performance indicators supporting that the filtration and analysis steps did not compromise method integrity.

Nylon filters

PFAS analytes were ND in any nylon syringe filters evaluated, including Puradisc, Whatman GD/X, Acrodisc, and Acrodisc PSF filters (Table 2). This outcome suggests that nylon membranes did not contribute measurable PFAS contamination under the conditions evaluated. Importantly, testing of Whatman GD/X filters confirmed that the added GMF prefilter layer did not introduce PFAS contamination, with results consistent with single membrane nylon filters.

Table 2. PFAS detection results for Cytiva nylon syringe filters compared to MDL and MRL values. PFAS detection results for Cytiva nylon syringe filters under modified EPA Method 1633A. All compounds were reported as ND. Whatman GD/X, Acrodisc, and Acrodisc PSF filters were evaluated in three lots. Puradisc nylon filter was evaluated in two lots denoted by an asterisk (*).

EIS recoveries for nylon filters were consistently within EPA method 1633A acceptance limits, averaging approximately 92-122% across all isotopically labeled compounds (Table 3). These results may indicate that nylon membranes did not compromise analyte recovery or method performance, supporting their suitability for use in the tested workflow and similar applications requiring equal or lower sensitivity.

Table 3. Average EIS recovery performance for Cytiva nylon syringe filters versus EPA method 1633A acceptance windows. Average EIS recoveries for Cytiva nylon syringe filters compared to method acceptance ranges. Whatman GD/X, Acrodisc, and Acrodisc PSF filters were evaluated in three lots. Puradisc nylon filter was evaluated in two lots denoted by an asterisk (*).

Regenerated cellulose and polyethersulfone filters

Like nylon, PFAS compounds were not detected in regenerated cellulose (RC) filters and in the majority of polyethersulfone (PES) filters evaluated (Table 4). The only exception was a single lot of Acrodisc Supor PES filter, which contained trace levels of 4:2 FTS, 6:2 FTS, and PFMBA (14, 17, and 14 ng/L, respectively), slightly above the method detection limit (MDL) but well below the minimum reporting level (MRL) of 50 ng/L for all three PFAS compounds. All other PES lots were reported as ND, suggesting that contamination risk is minimal. This also included Whatman GD/X RC and GD/X PES filters, which showed no detectable PFAS despite the presence of a GMF prefilter layer.

Table 4. PFAS detection results for Cytiva RC and PES syringe filters compared to MDL and MRL values. PFAS detection results for Cytiva RC and PES syringe filters under modified EPA method 1633A. Concentrations represent the highest value observed across lots or ND. Puradisc RC and PES, and Acrodisc Supor PES filters were evaluated in three lots. Whatman GD/X RC filter was evaluated in two lots denoted by an asterisk (*).

EIS recoveries for RC and PES filters were generally within EPA method 1633A acceptance ranges, as shown in Table 5. Puradisc and Whatman GD/X RC filters ranged from 94% to 128%, confirming stable performance. Puradisc and Whatman GD/X PES filters ranged from 91% to 122%, also within acceptable limits. One exception was Acrodisc Supor PES filter, which showed an outlier average recovery of 148% for ¹³C₅-PFPeA, coinciding with the lot that exhibited PFAS detections. This anomaly is most plausibly due to matrix or coelution effects, where trace PFAS or other co‑extracted species may have enhanced EIS signals during LC‑MS/MS analysis, rather than indicating true recovery loss. Despite this, all other EIS recoveries for Acrodisc Supor PES filter remained within acceptable limits (93–116%), consistent with overall method integrity.

Table 5. Average EIS recovery performance for Cytiva RC and PES syringe filters versus EPA method 1633A acceptance windows. Average EIS recoveries for Cytiva RC and PES syringe filters compared to method acceptance ranges. Puradisc RC and PES, and Acrodisc Supor PES filters were evaluated in three lots. Whatman GD/X RC filter was evaluated in two lots and is marked with an asterisk (*).

Conclusion

Testing under a modified EPA method 1633A demonstrated that Cytiva syringe filters generally do not introduce detectable PFAS compounds at the sensitivity level used in this study. All tested lots of nylon and regenerated cellulose syringe filters—across multiple product ranges—showed no detectable PFAS compounds. Polyethersulfone filters also showed no detectable PFAS in nearly all lots. However, one lot of Acrodisc Supor PES filter exhibited trace amounts of three PFAS compounds (4:2 FTS, 6:2 FTS, and PFMBA) slightly above the method detection limit (MDL) but below the minimum reporting level (MRL). EIS recoveries were within method acceptance limits for nearly all syringe filters, with a single outlier(¹³C₅-PFPeA) in the same Acrodisc Supor PES filter lot that showed trace PFAS. Taken together with the native analyte results, the findings support reliable analyte recovery across the evaluated products.

Importantly, Whatman GD/X filters, which include GMF prefilter layers, were tested for PFAS contamination and showed no detectable PFAS, indicating that the additional prefilter material did not introduce contamination under the conditions evaluated.

For customers or users working with PFAS workflows, it is important to note that, given the limited number of samples and conditions tested, additional studies across more products, matrices, and method steps are recommended to confirm these results under broader scenarios. Although these findings apply specifically to EPA method 1633A, they may offer helpful preliminary guidance for evaluating syringe filter performance in other PFAS related standards and test methods, which remain a critical area for future research.