Meaning
Analytical instrument used in conjunction with a Karl Fischer titrator to extract moisture from solid samples. Testing of resins that are insoluble or contain additives that would poison the reagent requires this specialized heating approach. A headspace oven evaporator heats the polymer in a sealed vial, forcing the water into the gas phase without melting the entire sample into the titration cell.
Operational Principle
Nitrogen or air flows through the heated vial and carries the evaporated water molecules into the titration vessel. The temperature is controlled to within one degree to ensure repeatable results across different batches. This setup prevents the physical contamination of the cell, reducing the need for frequent cleaning and reagent changes.
Efficiency Gains
Automation of this process allows for the sequential testing of dozens of samples without operator intervention. Modern units use a needle to pierce the vial septum, maintaining a closed system that excludes ambient humidity. This high degree of isolation makes it possible to measure moisture levels in the low parts-per-million range with high confidence.
Material Limitations
Selection of the correct heating temperature is the most critical step in using this device. If the temperature is too low, the water remains trapped in the polymer matrix, leading to a false low reading. Excessive heat can cause the polymer to release non-water volatiles that interfere with the accuracy of the titration.
