Since its inception in 1935, Karl Fischer (KF) titration has been the undisputed gold standard for water content determination. Renowned for its pinpoint specificity, unwavering accuracy, and impressive speed, KF titration has become an indispensable tool across a wide range of scientific and industrial applications. This sophisticated technique involves a stoichiometric chemical reaction where water in a sample reacts with iodine, sulfur dioxide, and a base, facilitated by a solvent like methanol.

CH₃OH + SO₂ + I₂ + H₂O -> (RNH) * (CH₃OSO₃) + 2(RNH)

In simpler terms, water (H₂O) is the target component to measure, iodine (I₂) acts as the titrant, sulfur dioxide (SO₂) is a reactant, the base (RN) serves as a catalyst, and methanol (MeOH) facilitates the reaction. As the titration progresses, iodine is consumed until all the water in the sample has reacted. The point at which iodine consumption ceases signals the end of the titration, providing a precise measure of the water content.

A significant challenge in KF titration is the ubiquitous presence of environmental moisture, which can distort results. Water is pervasive in the air and on surfaces, potentially contaminating the titration process. While traditional titration systems utilize sealed vessels to prevent external moisture from affecting the results, modern systems like the EVA KF Titrators take this a step further. These advanced titrators are equipped with enhanced capabilities to not only seal the KF cell but also actively manage and maintain a dry state within it automatically. Before any sample is added, the cell undergoes pre-titration to eliminate residual water. Despite these precautions, small amounts of water may still infiltrate over time. To counteract this, EVA KF Titrators continuously measure and neutralize unwanted water through a process called cell conditioning, ensuring the titration remains accurate and reliable even in the presence of environmental moisture.

Effective management of cell drift is crucial for the accuracy of Karl Fischer titrations. Advanced titrators, including the EVA KF Titrators from METTLER TOLEDO, feature sophisticated algorithms that not only determine but also compensate for cell drift during the conditioning phase. This drift represents the amount of water entering the titration cell over time. The EVA models enhance this functionality by implementing drift stability stop criteria, a new addition alongside the classic drift stop criteria, which remains a standard approach in many systems.

By continuously monitoring the drift, the user can establish precise criteria for starting and stopping the titration based on drift stability. A low and stable drift value indicates that the cell is ready for sample analysis, ensuring that the titration starts under optimal conditions. Specific drift thresholds, particularly the drift stop criterion, ensure the titration stops accurately once the reaction is complete. This meticulous control over drift management ensures that the titration results are reliable and consistent, meeting stringent regulatory requirements where precision is paramount.