2.4. Water content analysis
The water content in dry and hydrated samples was
determined by the Karl–Fischer method (ThermoOrion AF8)
using the reagent Hydranal-Composite 5 from Sigma-Aldrich.
The Karl–Fischer apparatus was first calibrated with deionized
water. The sample (1 g) was weighed accurately and
transferred into automated titrating chamber. The titration
was carried out according to the procedure of Isengard and
Pra¨ger (2003). Experiments were made with three sample
replicates and coefficients of variation of less than 2% were
obtained for all samples.
The moisture content in solutions was determined by
refractometry.