CASE conclusions and outlook

As we saw in Section 9.3, the building blocks of CASE via MS are present for GC-MS and have been applied successfully to identify or confirm the identity of environmental contaminants in real samples. The use of additional substructure classifiers from the NIST database as well as calculated properties such as Rls, partition coefficients and steric energies provided vital information for candidate generation and selection and enhanced the chances for a successful CASE dramatically. However, there is a long way to go before CASE via El MS becomes viable for dally use with a success rate acceptable for routine application, not just research and development. The examples that were successful here were quite small molecules with detailed classifier information (Subsections 9.3.1 and 9.3.2) or with very detailed information about the parent compound (Subsection 9.3.3). In some ways, the success of CASE via EI-MS depended more on the availability of detailed substructure classifiers to reduce the number of structures, rather than the actual size of the molecule, per se. It is clear, however, that the larger the molecule (i.e. the greater the number of atoms), the more difficult de novo CASE will be due to the dramatic increase in the number of possible compounds. 

A number of areas in the CASE via EI-MS workflow could still be improved to increase the chances of a successful result. These include  

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