Hold up volume in Skid Mount Membrane Systems can lead to inefficiencies, contamination, and inaccurate measurements. Removing it is essential for optimal performance in filtration and process applications. Alongside our Vacuum Recovery Kit, another effective method is using pressurized air to purge unwanted fluid from lines, valves, and fittings.
What You'll Need
- A source of clean, dry pressurized air
- Access to the system's compression fittings (e.g., feed and concentrate bulkheads)
Steps to Remove Hold Up Volume
- Isolate the target section. Our systems have two lines: the main feed line and the bypass line. Identify which line you want to purge.
- Close the bypass valve. If purging the main feed line, ensure the bypass valve is fully closed before proceeding.
- Connect the air line. Remove an accessible compression fitting in the target line — such as the feed or concentrate bulkhead on top of the skid — and connect your pressurized air source there.
- Gradually apply air pressure. Slowly increase air pressure and direct airflow through the section, forcing any residual liquid out. Keep the tank cover closed to prevent splashing.
- Repeat for additional lines. Connect the air line to the appropriate port for each remaining line, closing the relevant valves as needed, and repeat the purge process.
Pro Tip: If you plan to do this regularly, consider installing a T-fitting with a ball valve on the feed line. This makes it quick and easy to connect the pressurized air line without removing fittings each time.
Ask an expert today if you have any questions about maintaining your system.
This Earth Day, one environmental issue demands urgent attention from the scientific and filtration communities: the global rise of PFAS contamination and the role our industry plays in addressing it.
What Are PFAS?
Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of synthetic chemicals that have been used in industrial and consumer products since the 1950s. They appear in non-stick cookware, stain-resistant fabrics, food packaging, firefighting foam, and — until recently, many laboratory consumables. The carbon-fluorine bond at the core of their chemistry is one of the strongest in nature. Their persistence has earned them the moniker "forever chemicals," underscoring their resistance to degradation and long-term accumulation in ecosystems.¹
The Scale of the Problem
The reach of PFAS contamination today is difficult to overstate. Approximately 176 million people in the U.S. drink tap water contaminated by PFAS, according to test data recently released by the EPA — four million more Americans than previous tests identified.² From an environmental perspective, PFAS are highly mobile and bioaccumulative: they can migrate through groundwater, accumulate in plants and animals, and move up the food chain. Wildlife exposure has been documented in remote regions far from known sources, underscoring the global scale of contamination.³
Health risks linked to PFAS exposure include certain cancers, liver damage, immune system effects, thyroid disease, and reproductive and developmental impacts.³⁴ As research advances, the need for accurate detection at extremely low concentrations continues to grow.
A Laboratory's Role
As detection methods reach parts per trillion sensitivity, even trace contamination can compromise results. Laboratory consumables such as syringe filters, membrane filters, and sample vials may introduce PFAS into samples if they are not carefully controlled. This makes PFAS free materials essential for reliable data and credible research outcomes.
Sterlitech's Commitment
This is why Sterlitech is proud to introduce our new line of PFAS-Free laboratory products, including PFAS-Free Syringe Filters, PFAS-Free Membrane Filters, and PFAS-Free Syringeless Vials — all manufactured from raw materials free of PFAS. These products are designed to support the rigorous, contamination-free workflows that environmental researchers and water quality laboratories depend on.
Looking Forward
Since PFAS remain in human bodies and the environment for decades even after emissions cease, early action is vital to reduce long-term health and environmental costs.⁵ Regulatory momentum is growing worldwide, and the demand for reliable, contamination-free testing will only increase with it
This Earth Day, we reaffirm our commitment to equipping researchers with the tools they need to generate reliable data and drive meaningful environmental progress. 
References
Kareem, H.A. et al. (2026, February). Current Research Advances and Future Prospects on Microbial Consortia for Sustainable PFAS Remediation. International Journal of Molecular Sciences. https://pmc.ncbi.nlm.nih.gov/articles/PMC12940359/
Environmental Working Group. (2026, March 10). New Data Shows 176M Exposed to Forever Chemicals as Trump EPA Rolls Back Protections. https://www.ewg.org/news-insights/news-release/2026/03/new-data-shows-176m-exposed-forever-chemicals-trump-epa-rolls
Z2Data. (2026, February 12). Everything You Need to Know About PFAS in 2026. https://www.z2data.com/insights/everything-you-need-to-know-about-pfas-in-2026
U.S. Environmental Protection Agency. (2026, February 10). Our Current Understanding of the Human Health and Environmental Risks of PFAS. https://www.epa.gov/pfas/our-current-understanding-human-health-and-environmental-risks-pfas
European Commission, Directorate-General for Environment. (2026, January 29). New Study Confirms Huge and Growing Costs of PFAS Pollution. https://environment.ec.europa.eu/news/new-study-confirms-huge-and-growing-costs-pfas-pollution-2026-01-29_en
Per- and polyfluoroalkyl substances (PFAS) — including well-known compounds like PFOA (perfluorooctanoic acid) — are a class of synthetic chemicals derived from fluorinated hydrocarbons. Because the carbon-fluorine bond is one of the strongest in organic chemistry, PFAS persist indefinitely in the environment, earning them the name “forever chemicals.”
Historically incorporated into non-stick coatings, fire-resistant materials, water-repellent packaging, and pesticides, PFAS are now detectable in drinking water, soil, and biological tissue worldwide. Due to their persistence and well-documented adverse effects on human health and the environment, the U.S. Environmental Protection Agency (EPA) has established rigorous testing guidelines for PFAS across multiple sample matrices.
EPA Methods for PFAS Testing
| EPA Method | Sample Matrix | Minimum Detection Limit (MDL / Reporting Level) | Description |
| EPA 537.1 (v2.0) | Drinking water | ~2 ng/L or lower | Improved version of 537 with 18 PFAS, better QA/QC and faster workflow; widely used for regulatory compliance |
| EPA 533 (2019) | Drinking water | ~1–5 ng/L | Uses isotope dilution + anion exchange SPE; optimized for short-chain PFAS not well captured in 537.1 |
| EPA 8327 | Non-potable water (groundwater, wastewater, etc.) | ~10–100 ng/L (method dependent) | “Dilute-and-shoot” LC-MS/MS method; faster but less sensitive than drinking water methods; external calibration |
| EPA 1633 | Multi-matrix (water, soil, sediment, biosolids, tissue) | ~1–10 ng/L (matrix dependent) |
Most comprehensive method (~40 PFAS); designed for CERCLA / environmental investigations; multi-matrix capability |
As analytical methods become more sensitive — routinely reaching detection limits in the parts-per-trillion (ppt) range — the risk of contamination from laboratory consumables becomes a critical concern. Even trace levels of PFAS introduced by sample preparation materials can compromise results at these concentrations.
PFAS are commonly present in:
- Tubing and seals (e.g., PTFE)
- Filters and Membranes
- Sample containers and caps
- Laboratory environments
Even trace contamination can lead to:
- False positives
- Failed QA/QC criteria
- Compromised regulatory compliance
Sterlitech PFAS-Free Sample Preparation Products
Sterlitech provides sample preparation products that support contamination free workflow. Our PFAS-Free Syringe Filters, PFAS-Free Membrane Filters, and PFAS-Free Syringeless Vials are made from raw materials manufactured free of PFAS Contamination.
| Syringe Filters | ||
| Membrane Material | Pore Size (um) | Diameter (mm) |
| PES | 0.22, 0.45 | 13, 25, 33 |
| Nylon | 0.22, 0.45 | 13, 25, 33 |
| Regenerated Cellulose | 0.22, 0.45 | 13, 25 |
| Cellulose Acetate | 0.2, 0.45, 0.8, 1.2, 5.0 | 13, 25 |
| Glass Fiber | 0.45, 0.7, 1.0, 1.2, 3.1 | 25 |
| Membrane Filters | ||
| Material | Pore Size (um) | Diameter (mm) |
| PES | 0.2, 0.45 | 47 |
| Nylon | 0.2, 0.45 | 47 |
Control Contamination by Reducing Steps in Your Sample Preparation Workflow
Separa® filter vials combine the function of a syringe filter and an autosampler vial in one by integrating a membrane in the cap, removing the use of syringes in syringe filtration. Its compact design and compatibility with UHPLC and HPLC Autosamplers reduce contamination from subsequent transfer of the sample container to a syringe, through a syringe filter to be dispensed in an autosampler vial.
Traditional Filtration using a Syringe Filter
- Fill the syringe with the sample
- Attach the syringe filter (luer lock connection)
- Push the plunger to filter into an autosampler vial
- Cap the vial for HPLC analysis
Each transfer step introduces potential contamination.
Syringeless Filtration using Separa®
Sterlitech PFAS-Free products are designed to help laboratories maintain compliance with stringent EPA regulatory standards, by reducing false positives, and improving analytical confidence.
As PFAS testing regulations continue to evolve, choosing the right products is becoming an analytical necessity. Request a quote today for Sterlitech PFAS-Free products.
