Introduction

Many limited-volume autosampler inserts use a plastic spring or support foot to maintain proper positioning within the vial. These components help center the insert, establish the correct height, and ensure consistent interaction between the sample and the autosampler needle.

When sterilization is required, it is important to consider the different thermal properties of the materials used in the insert assembly. Although the glass portion of the insert is highly heat resistant, the attached plastic components are significantly more temperature sensitive.  For this reason, autoclaving inserts that contain plastic springs is not recommended.

Mixed-Material Construction

Many limited-volume insert assemblies consist of:

• Borosilicate glass insert
• Polyethylene or similar plastic spring
• Integrated positioning components

These materials perform well during normal analytical use but respond differently when exposed to elevated temperatures, pressure, and moisture.

Why Autoclaving Can Damage the Insert

Autoclaves utilize a combination of:

• High temperature
• Steam
• Elevated pressure

While the glass insert generally tolerates these conditions without difficulty, the plastic spring may not.  Potential effects include:

• Loss of elasticity
• Deformation
• Softening
• Cracking
• Dimensional changes

Once the spring loses its original shape, the insert may no longer perform as designed.

Potential Impact on Autosampler Performance

Damage to the plastic spring can affect:

Insert Positioning

The spring helps maintain proper insert height and alignment within the vial.  If the spring deforms, the insert may sit incorrectly.

Sample Recovery

Improper positioning can influence:

• Needle access
• Aspiration consistency
• Low-volume sample recovery

Autosampler Reliability

Dimensional changes may contribute to:

• Sampling variability
• Positioning inconsistencies
• Reduced analytical reproducibility

Even when the glass insert appears unchanged, deformation of the plastic component may render the assembly unsuitable for analytical use.

Insert Assembly Illustration

Glass autosampler insert with integrated plastic spring used to maintain proper alignment, positioning, and stability within the autosampler vial.

Recommended Alternative Sterilization Method

For laboratories requiring sterilization of insert assemblies containing plastic springs, a lower-temperature sterilization technique may be more appropriate.

Ethylene Oxide (EtO) Sterilization

Ethylene oxide sterilization can help achieve sterilization objectives without exposing the plastic spring to the temperatures typically encountered during autoclaving.  Potential benefits include:

• Preservation of spring geometry
• Maintenance of elasticity
• Reduced risk of deformation
• Continued insert functionality

Users should validate suitability for their specific application and laboratory procedures.

Best Practices

When working with inserts that contain plastic support components:

• Avoid autoclaving unless the entire assembly has been specifically validated for autoclave use.
• Inspect springs regularly for damage.
• Replace damaged insert assemblies rather than attempting repair.
• Consider alternative sterilization methods when sterility is required.

These practices help maintain proper insert performance and protect analytical results.

Conclusion

Although the glass portion of an autosampler insert can withstand extreme temperatures, inserts equipped with plastic springs or support feet should not be autoclaved. The heat, steam, and pressure associated with autoclave sterilization can deform the plastic component, compromising insert positioning and autosampler performance. When sterilization is necessary, alternative methods such as ethylene oxide sterilization may be more appropriate for preserving the integrity of the complete insert assembly.