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Addition of alcohols
Methanol does not satisfactorily dissolve long-chained hydrocarbons, resulting in a biphasic mixture in the titration vessel. This does not necessarily inhibit the Karl Fischer reaction since the water in the hydrocarbon phase is quickly extracted and titrated during a measurement. However, if the indication electrode is situated in the hydrocarbon phase rather than in the methanol phase or if oily deposits coat the electrode, problems can occur.
These problems may be avoided by adding 1-propanol to the working medium. A mixture of HYDRANAL®-Methanol dry and 1-propanol can be used as working medium for the one-component reagent, HYDRANAL®-Composite. For the two-component reagent, HYDRANAL®-Solvent/Titrant, a portion of the solvent component is replaced by 1-propanol. The amount of solvent component used depends upon the amount of water expected to be determined (1 mL HYDRANAL®-Solvent approximates 7 mg water).
Long-chained alcohols can be used in the same way as 1-propanol. Occasionally it is necessary to investigate alcohols of various chain lengths, and choose the alcohol based on its solubility toward the sample being investigated.
Addition of chloroform
Fats, long-chained hydrocarbons and other lipophilic substances show limited solubility in alcohols. Addition of HYDRANAL®-Chloroform to the working medium highly improves their solubility. However, for exact determination of water, the chloroform content should not exceed 70 %. Addition of chloroform also accelerates the Karl Fischer reaction.
The coulometric reagent HYDRANAL®-Coulomat A contains chloroform for better solubility of fatty substances. The chloroform content may still be increased, but it should not exceed 30 %, otherwise the conductivity will decrease. The minimum conductivity differs from instrument to instrument, so an exact maximum chloroform volume cannot be given here.
Product range HYDRANAL® reagents for non-polar substances
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