2.3. CI-, FD- and FAB-MS analysis
During the 1980s, besides EI ionization soft ionization techniques
such as CI (chemical ionization), FD (field desorption) and
FAB (fast atom bombardment) started to appear in the MS analysis
of bisindole alkaloids.
The first studies were targeting the structure elucidation
of the degradation products of VLB and VCR dihydrogen sulphates
[36,37] using ammonia desorption chemical ionization