| Abstract: | The key to enhanced electron-capture negative ion mass spectrometry (ECNI-MS) response of ketosteroids is extensive α,β-unsaturation. Combinations of double bonds, carbonyl groups, epoxides and halogens within a steroid nucleus were correlated with their ECNI responses. The greatest ECNI responses result from extensive conjugation, such as the linearly conjugated 4-ene-3,6-dione system and the cross-conjugated 1,4-diene-3,11-dione system. In general, an epoxy ketosteroid has a relative response 40 times greater than that of its corresponding enone. In an α-halo ketone, an axial halogen substitution will increase the relative response by an order of magnitude, but an equatorial halogen substituent will not affect the response. The fragmentation of ketosteroids as related to ECNI response is discussed. |
