Introduction

PEEK tubing is widely used in HPLC, UHPLC, LC-MS, biotechnology, and laboratory fluid handling applications due to its chemical resistance, mechanical strength, and low metal content. Because it is frequently used as part of the analytical fluid path, laboratories often ask about potential contamination that may arise during manufacturing.

One common concern is whether residues from previous extrusion runs can contaminate the interior surface of newly manufactured tubing.

PEEK Tubing Extrusion Process

PEEK tubing is manufactured through an extrusion process in which the tubing is formed while maintaining the desired internal diameter, wall thickness, and dimensional tolerances.

During extrusion, air is used to help form and maintain the internal lumen of the tubing.

As a result:

• The interior of the tubing is exposed only to air during manufacturing.
• No processing materials contact the inner tubing surface during the extrusion process.
• The internal flow path remains isolated from exterior manufacturing surfaces.

This manufacturing approach helps preserve the cleanliness of the tubing interior, which is particularly important for chromatography and analytical applications.

Interior Versus Exterior Surface Cleanliness

The interior and exterior surfaces of tubing experience different manufacturing conditions.

Interior Surface

The internal pathway of the tubing is protected during extrusion and only encounters air during the manufacturing process.

This helps provide:

• A cleaner internal surface
• Reduced risk of fluid-path contamination
• Suitability for analytical laboratory applications
• Reliable fluid transfer performance

Exterior Surface

The outer surface of the tubing is exposed to the manufacturing environment and handling processes.  As a result, the exterior surface may not possess the same level of cleanliness as the tubing interior.  For applications where exterior cleanliness is important, laboratories may choose to inspect or clean the tubing before installation according to their established procedures.

Why Internal Cleanliness Matters

Internal surface cleanliness is particularly important for:

• HPLC systems
• UHPLC systems
• LC-MS systems
• Biocompatible fluid paths
• Analytical sample transfer
• Laboratory automation systems
• Pharmaceutical applications

Contaminants introduced into the fluid path can potentially affect analytical performance, making tubing cleanliness an important consideration when selecting chromatography components.

Best Practices Before Installation

Although the tubing interior is protected during manufacturing, good laboratory practice may include:

• Inspecting tubing before use
• Flushing tubing prior to installation when appropriate
• Following laboratory SOP requirements
• Verifying cleanliness requirements for regulated applications

These practices can help ensure optimal system performance and analytical reliability.

Conclusion

PEEK tubing extrusion is designed so that only air contacts the interior of the tubing during manufacturing. This helps maintain a clean internal fluid path and minimizes the possibility of contamination from previous extrusion runs. While the interior of the tubing is protected during production, the exterior surface may not have the same level of cleanliness and should be evaluated according to the requirements of the intended application.