Karl Fischer Titrator (Trace Moisture Analyzer) FAQs

　　Karl Fischer titrator (also known as trace moisture meter)

　　1. What is the difference between Karl Fischer titration and coulometric titration?

　　The titrant can be added directly to the sample via a burette (volumetric method) or it can be generated electrochemically in a titration cell (coulometric method).

　　When the content is very low, for example less than 50-100 ppm (0.005-0.01%), coulometric titration according to Karl Fischer is mainly used for the determination of water.

　　2. When should I use a battery with or without a separator?

　　For most applications we recommend a cell without diaphragm as it is virtually maintenance-free. Due to its innovative design, this diaphragm-free cell from METTLER TOLEDO can even be used to determine water in oil.

　　This sample cell with a diaphragm is recommended for applications such as the determination of water in substances containing ketones. It is also recommended if the best possible precision is required.

　　3. How often do I need to standardize my titrant?

　　Naturally, this depends on the stability of the titrant and what measures are taken to protect the titrant from typical contaminants that could cause a decrease in concentration. The most common examples of such titrant protection are the storage of light-sensitive titrants in dark bottles (e.g. iodine solutions), the use of molecular sieves or silica gel to protect Karl Fischer titrants from moisture, and the protection of certain strong bases (e.g. sodium hydroxide) from carbon dioxide absorption.

　　4. How do I know when to replace the molecular sieve in the drying tube on my Karl Fischer titrator?

　　The most practical way to solve this problem is to add some blue silica gel as an indicator to the top of the drying tube. Once the first traces of pink appear in this gel layer, it is time to change or regenerate the molecular sieve. Naturally, an increase in background drift may also indicate that it is time to change the molecular sieve.

　　5. How to validate a method on an autotitrator?

　　When validating a titrator method, things like accuracy, precision, repeatability, linearity, systematic error, robustness, ruggedness and determination limits need to be checked. For detailed advice on how to perform this validation, see our section on Quality Control, Validation, or refer to the METTLER TOLEDO Application Note 16 - Validation of Titration Methods.