Aldehydes & Ketones

Both of these classes of compounds, aldehydes and ketones, interfere with the normal Karl Fischer titration as they react with methanol to form water which is also titrated. The Karl Fischer titration shows an incorrect, too high water content or vanishing end points with classical reagents. Methanol has to be replaced by other alcohols. In classic Karl Fischer reagents, methanol has been replaced by 2-methoxyethanol, which gives poor results. The side reaction is not suppressed enough and the Karl Fischer reaction rate is very slow in this alcohol. Sigma-Aldrich found that other alcohols and glycolethers are particularly good substitutes. The HYDRANAL^®-Laboratory has developed special reagents for the volumetric and coulometric determination of water in ketones and aldehydes.

HYDRANAL Medium K: Non-toxic Karl Fischer reagent with performance and safety advantages

In HYDRANAL Medium K we have replaced toxic 2-chloroethanol of HYDRANAL Working Medium K with less hazardous alcohols, permitting its categorisation merely as harmful (Xn) due to its percentage of chloroform. HYDRANAL Working Medium K is categorised as very toxic (T+) because it contains 2-chloroethanol.

Benefits of HYDRANAL Medium K over HYDRANAL Working Medium K
- Reduced toxicity
- Improved workplace safety
- Reduced packaging material
- Equal reactivity and performance

HYDRANAL Medium K is a full-fledged substitute for HYDRANAL Working Medium K, providing the same sample capacity, speed and accuracy. It offers important application, safety and transportation benefits; because it is non-toxic, it not only improves workplace safety, it also reduces packaging material: HYDRANAL Working Medium K requires extensive packaging including vermiculite, plastic bag and tin can, whereas HYDRANAL Medium K may be shipped without any extra materials.

HYDRANAL Medium K is equally reactive as HYDRANAL Working Medium K, guaranteeing short titration times and accurate results. HYDRANAL Medium K offers performance advantages with very reactive aldehydes such as propionaldehyde, butyraldehyde and crotonaldehyde. Capacity and accuracy are also improved for other compounds including salicylaldehyde, acetylacetone, 2,4-dihydroxyacetophenone and 2-benzolpyridine.

Comparison experiments in our HYDRANAL laboratory between HYDRANAL Working Medium K and HYDRANAL Medium K show:
- Comparable sample capacity in 30 mL medium
- Comparable results for water content and standard deviation
- Comparable titration speed
- Comparable accuracy of recovery rate of added water after sample titration

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Literature

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