Water Determination in Glycerol Monostearate

This long-chained stearate does not dissolve in the alcoholic Karl Fischer working media. Thus it is necessary to use a solubilizing agent.

In the European Pharmacopoeia (Ph. Eur.) pyridine is used as a solubilizing agent, at elevated temperature. However, the endpoint detection in pure pyridine is not ideal, as the system tends to over-titrate. For good results, we recommend using a mixture of methanol and chloroform

Procedure for volumetric one-component titration:

Add 40 mL Hydranal-LipoSolver CM, or a mixture of 20 mL Hydranal-Methanol dry or Hydranal-Methanol Rapid and 20 mL Hydranal-Chloroform to the titration vessel. Titrate to dryness with Hydranal-Composite 5. Precisely weigh-in a 1 g sample using differential weighing and titrate the water content with Hydranal-Composite 5.

Procedure for volumetric two-component titration:

Add 40 mL Hydranal-Solvent CM or a mixture of 20 mL Hydranal-Solvent and 20 mL Hydranal-Chloroform to the titration vessel. Titrate to dryness with Hydranal-Titrant 5. Precisely weigh-in a 1 g sample using differential weighing and titrate the water content with Hydranal- Titrant 5.

Hydranal-Water Standard 10.0, Hydranal-Water Standard 1.0, and Hydranal-Standard Sodium Tartrate Dihydrate are suitable for determination of the titer or control of the volumetric determination.

Note: A Suitability test including protocol according to Ph. Eur. is available on request (hydranal@honeywell.com).