Coulometric Titration Baseline Drift Calibration Methods
Drift calibration isolates cell background current from true sample moisture, preventing hydrolytic degradation and avoiding false incoming resin lot rejections.
PTFE Septa
Meaning
Elastomeric seals faced with a thin layer of polytetrafluoroethylene used to close sample vials and reaction vessels. In polymer moisture testing, PTFE septa prevent atmospheric water vapor from entering the sample before or during heating. The non-stick coating faces the inside of the vial to resist chemical attack from solvents and high temperatures.
Sealing Integrity
Compression of the elastomeric backing maintains a tight seal against the glass rim of the vial. This pressure ensures that PTFE septa prevent moisture ingress during storage and heating cycles.
Puncture Performance
Needle penetration occurs when an autosampler or manual syringe draws a sample or injects a reagent. The polytetrafluoroethylene layer resists tearing, while the underlying elastomer reseals the puncture hole after the needle is withdrawn. If the PTFE septa fail to reseal, ambient air leaks into the vial and corrupts the analysis.
Replacing the seal after every puncture ensures that moisture does not contaminate subsequent runs.
Temperature Resistance
Thermal extraction of moisture from nylon or polyester pellets requires vial heating up to two hundred degrees Celsius. High-performance fluoropolymer linings maintain their structural stability and do not release volatile organic compounds at these temperatures. This thermal endurance of PTFE septa makes them suitable for automated head-space analysis.