General Comments and Future Prospects

Positive and negative ion mass spectra are equally accessible in all the desorption ionization modes with the exception of FDMS. Here the problem has been to achieve desorption of the negative ions before field induced emission of electrons occurs 28). The fact that many natural products contain ionized acidic functions undoubtedly assists the formation of negative ions from them and the negative ion spectra are frequently more useful than their positive ion counterparts. 

New ionization techniques continue to be developed. One of the most promising is the thermospray method introduced by Vestal and co-workers 29) in which the effluent from a liquid chromatograph is partially flash 

---