pH Compatibility of 316 Stainless‑Steel Tubing, Fittings, and Sparging Stones in HPLC Systems
316 stainless steel is among the most common metals used in HPLC system construction, particularly for tubing, fittings, unions, and sparging stones.
Its strength, corrosion resistance, and chemical durability make it a reliable choice for a broad range of chromatographic applications. We provide clear guidance on the usable pH range of these components:
✔ Usable pH Range: 1–14
According to MICROSOLV technical data, 316 stainless‑steel tubing, fittings, and sparging stones are compatible with the full aqueous pH range from 1 to 14 when used under typical HPLC operating conditions.
This wide tolerance allows these components to be used with acidic, neutral, and basic mobile phases commonly encountered in reversed‑phase, normal‑phase, and sample‑prep workflows.
Why 316 Stainless Steel Performs Well Across Such a Broad pH Range
316 stainless steel contains chromium, nickel, and molybdenum—all of which contribute to the formation of a stable, protective oxide layer. This passive layer resists chemical attack from a variety of mobile phase additives including formic acid, phosphoric acid, ammonium salts, and many common bases.
Key performance advantages include:
- High corrosion resistance in both acidic and basic conditions
- Excellent structural integrity at standard HPLC pressures
- Compatibility with organic solvents such as methanol, acetonitrile, IPA
- Long-term durability even with aggressive flushing cycles
However, while compatible across pH 1–14, performance still depends on exposure time, temperature, chloride content, and system cleanliness.
Considerations When Operating Near pH Extremes
Although 316 stainless steel is rated for the full pH range, some practical considerations apply:
At Very Low pH (1–2)
- High concentrations of strong acids (e.g., >0.1 M HCl) may accelerate corrosion.
- Avoid long soaks in strong mineral acids when the system is idle.
- Rinse thoroughly with water after acidic cleaning sequences.
At Very High pH (12–14)
- Strong bases like NaOH can cause surface etching or roughening over time.
- Reducing the temperature and limiting exposure duration slows corrosion mechanisms.
- When frequent high‑pH operation is needed, consider alternative wetted materials (PEEK, titanium, MP35N) where appropriate.
Chlorides & Halides
- High‑chloride solutions (common in biological buffers) can increase pitting risk.
- For chloride‑rich workflows, rinsing with fresh water before shutdown prevents localized corrosion.
Application Areas Where 316 Stainless‑Steel Components Excel
316 stainless steel is commonly used in:
- HPLC solvent delivery lines
- Autosampler loops and injector pathways
- In‑line frits and sparging stones for degassing or mobile phase preparation
- High‑pressure transfer lines
- General‑purpose LC and LC‑MS configurations
Sparging stones made of 316 stainless steel allow efficient mobile phase deaeration while maintaining structural rigidity and full pH compatibility across various solvent systems.
Best Practices for Maximizing Component Lifetime
To maintain optimal performance and prevent corrosion:
- Flush the system after exposure to extreme pH solutions.
- Avoid storing mobile phases inside stainless‑steel components for long periods.
- Move toward PEEK components when dealing with strongly halogenated solvents or extremely high‑pH conditions.
- Regularly inspect fittings and connections for discoloration or pitting.
Additional Resources
More information on stainless‑steel tubing and sparging stones can be found on this website: Click HERE for more information about stainless steel tubing