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.
Micro-Syringe Injection
Meaning
Precise delivery of minute liquid volumes into an analytical instrument or titration cell. In Karl Fischer analysis of polymers, micro-syringe injection introduces liquid samples or moisture standards into the reaction vessel without exposing them to ambient air. This technique is necessary when testing hygroscopic plastics where even micrograms of atmospheric water can distort the measurement.
Volumetric Precision
Graduated glass barrels and fine needles allow operators to measure and dispense volumes as small as a fraction of a microliter. This precision ensures that micro-syringe injection delivers the exact mass required for accurate moisture calibration.
Procedure Execution
Operators draw the liquid sample into the barrel and weigh the syringe on an analytical balance before delivery. After performing the micro-syringe injection, the syringe is weighed again to determine the delivered mass by difference. This gravimetric method eliminates volumetric errors caused by thermal expansion or air bubbles.
It provides a reliable baseline for calculating the moisture content of the polymer sample.
Moisture Prevention
Exposing the syringe needle to air for even a few seconds can introduce atmospheric moisture. Specialized tight-fitting seals and rapid execution are necessary to maintain the dryness of the reagent and sample. Proper execution of micro-syringe injection avoids false high readings in the titration results.