Coulometric Titration - Faster and More Efficient New Aquastar^® Coulometric Reagent for Karl Fischer Water Determination

Bettina Straub-Jubb, Global Product Manager Titration

Merck

Article from Analytix Reporter - Issue 10

Introduction

Coulometric Karl Fischer titration is the most suitable method and especially evolved for determining very low levels of water in a wide variety of samples, providing accurate and reliable results and a fast titration.

The new coulometric Anolyte for cells without a diaphragm was formulated to improve coulometric titration, making the process even faster. Using this new reagent gives highly accurate and reproducible results.

Coulometric Titration for Water Determination

The coulometric Karl Fischer Titration is an absolute method and therefore the method of choice for low water content samples. Coulometry generates iodine in situ through anodic oxidation at the generator electrode during the titration. Therefore, coulometric reagents do not contain iodine, but iodide. A very sensitive and accurate control of the iodine generation enables the precise determination of very low water concentration, down to 10 ppm.

The direct coulometric method is recommended only for liquid samples. For solid samples, an external water release is needed, or the Karl Fischer oven technology can be used in combination with a coulometric titrator for samples who are thermally stable.

The coulometric Karl Fischer Titration does not require standardization, but a regular instrument check with an appropriate water standard is recommended.

New Karl Fischer Anolyte for Cells Without a Diaphragm

Many samples dissolve easily in methanol - the alcohol used in coulometric reagents. However, some samples need the addition of co-solvent or buffer to dissolve or react properly. The new reagent can be used for a wide variety of samples, especially those that need a solubilizer or buffer to achieve accurate and precise titration results. Low water content in the range of 10 ppm to 10 000 ppm can be determined precisely and reproducibly. Oils, fats, ointments, strong acids, and bases can be determined with the addition of solubilizer or bases with a direct titration; and solid, insoluble samples, or samples causing side reactions with the Karl Fischer oven method or an external water release.

The new Anolyte can be used with all kinds of samples and methods. It shows a very fast conditioning time and a very good drift stability. The sample titration is fast as well, and the results have an excellent precision.

This new coulometric Anolyte makes the water determination in samples with low water content much more efficient and accurate.

Benefits

• No crystallization
• Extremely fast with efficient conditioning time
• Very good drift stability
• Rapid and reproducible results
• High accuracy and excellent precision

See also our protocol overview for Karl Fischer titration.

For application support contact aquastar@merckgroup.com.