Samples are weighed into centrifuge tubes, and water or an aqueous solution is added. The tubes are covered, and the sample is dispersed in the liquid by shaking. The dispersion is allowed to equilibrate for 20 minutes with repeated shaking every five minutes. The tubes are centrifuged, the clear liquid is poured off, and the contents of the tube are weighed. The water retained by the sample is calculated from the recorded weights.
This method applies to powders that are insoluble and readily dispersible in water. The method was developed for grain-based products. It can be applied to other powders meeting the criteria listed above.
Any powders not meeting the criteria listed above.
An analytical balance, centrifuge, and centrifuge tubes are required for this method.
Results are reported in grams water retained per gram of sample.
The solvent used can be water or an aqueous solution of salts, weak acids, or weak bases, depending on the application.