Karl Fischer Titration Interference Mechanisms in Recycled Polyester Flake Qualification
Karl Fischer moisture testing of recycled PET flake requires thermal desorption at 170 C with methanol-free reagents to eliminate volatile interference.
Drift Baseline
Meaning
Rate of continuous moisture leakage into an analytical testing cell from the surrounding room environment. Accurate Karl Fischer moisture analysis of dry resin relies on a stable drift baseline to subtract this background moisture from the sample titration result. This variable is measured in micrograms of water per minute and must remain constant during the entire analytical run.
Background Compensation
Titration software automatically calculates and compensates for this continuous moisture entry. A fluctuating drift baseline makes it impossible to distinguish between background water and the moisture released by the polymer sample. If the drift becomes too high or unstable, the instrument cannot deliver reproducible moisture results for dry nylon or polyester pellets.
Moulders must wait for the instrument to stabilize before running critical material checks.
Ambient Infiltration
High relative humidity in the testing room often causes the background drift to rise. Degraded septa or dried-out seals on the titration vessel worsen this problem. Replacing these sealing components restores a low, stable background rate.
This physical maintenance ensures that the analyzer measures only the water extracted from the resin sample.
Measurement Accuracy
Stable drift rates prevent false positive moisture readings that would lead to unnecessary drying delays. This baseline monitoring ensures reliable data for material release.