FAB mass spectrometry coupled with the host-guest complexation method was used to distinguish some amino sugars (1-8) including glucosamine, galactosamine, and mannosamine, etc. The method characteristically used a 1:1 mixture of the chiral crown ether host whose enantiomer was isotopically labeled. Diastereomer differentiation of a given amino sugar salt (G+) was simply measured with a given host pair (A or B) (HRRRR:HSSSS-d6=1:1) from the peak intensity ratio of the two diastereomeric host-guest complex ions as I[(HRRRR+G)+]/I[(HSSSS-d6+G)+]≡IRIS (abbreviation). The stereoisomer differentiation was performed by the IRIS values in the range from 0.4 to 2.0 (for the use of the host pair A) and from 0.4 to 3.4 (for the use of the host pair B). The five underivatized amino sugar hydrochloride salts (1-5) were successfully differentiated using the present chiral recognition FAB mass spectrometry. The stereoisomer-(13C)-labeled guest method was also presensed to evaluate their relative complexation abilities
