When we prepare these oligosaccharides, we standardise the concentration with the phenol-sulphuric acid method with the relevant monosaccharide (eg. mannose for mannooligosaccharides) as standard.  An appropriate volume is then dispensed and freeze dried.  We cannot have accurate knowledge of the current moisture content in your sample as this depends on many factors but would suspect it would be roughly 5%.  The moisture content is not included in the impurities stated.

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