7.3.3 Advantages of GC over MS; Chiral separations

         One of the most difficult classes of compounds to separate is chiral compounds.  In some cases these can be separated by normal capillary column GC, usually if the compound has more than one chiral center.  Recall, the criteria that allows separation is if the chemical structure results in a different set of physical characteristics such as boiling point.  In our design of several laboratory experiments we accidentally came across several chiral compounds that separated on a DB-5 capillary column (in the fragrance experiments in section 7.5).  We know this since two ion peaks that were extremely close to each other in the chromatograph give identical and essentially exclusive identification (99% probability of a library match with limited or no additional matches).  Chiral columns are available but only for a limited selection of a compound structures. In general, MS fragmentation will not distinguish between chiral compounds.

©Dunnivant & Ginsbach, 2008