For example, ketones and aldehydes react with methanol, producing water.
Interference can be suppressed by using dehydrating agents or anolytes for ketones that do not contain methanol.
However, when the amount of interference exceeds the suppressible amount, the dehydrating agent or anolyte must be replaced.
Oxidants might oxidize iodide ions, producing iodine, which would produce a negative error.
Reductive substances might consume iodine, which would produce a positive error.
If these are not volatile, they can be measured by applying the evaporation method.
Suitable pH values for the Karl Fischer reaction are 5 to 7.
Acidic and basic substances that cause fluctuations in the pH of the dehydrating agent or anolyte will produce errors in the measurement results. The reaction speed is significantly reduced at pH values below 5, which has an impact on accuracy and reliability.
Reactions that interfere with the consumption of iodine occur at pH values above 7, resulting in positive errors.
This interference can be prevented by adding imidazole to acidic substances, or salicylic acid to basic substances.
The interfering reactions described here are only examples. If you are unsure about other interfering reactions or compensating methods, contact KEM by filling out our “Question Form.”