Electron capture negative chemical ionization mass spectrometry of chemically oxidized corticosteroids.

A procedure which can be used to increase the electron affinity of corticosteroids for purposes of quantitative analysis is proposed. Ten important corticosteroids are chemically oxidized to 1,4-androstadien-3,11,17-trione or 4-androsten-3,6,17-trione structural steroid analogs to enhance their electrophilicity prior to detection by electron capture negative chemical ionization mass spectrometry. The choice of oxidation reagent, a preliminary assessment of the structure-response relationship of the oxidation products, the optimization of negative ion formation as a function of source temperature and the basis for distinguishing the isomers dexamethasone and betamethasone are addressed.