| Popis: |
Twenty monohydroxylated cholesterol derivatives have been characterized by high performance liquid column chromatography and by chemical ionization (CI) mass spectrometry. With ammonia as reagent gas four ions are formed: an ammonium adduct [M + NH 4 ] + , a substitution ion [M + NH 3 -OH] + and elimination ions [M-OH] + and [M-H 2 O-OH] + ]. Thermally stable stenediols exhibit [M + NH 4 ] + as principal ion, less stable allylic or tertiary alcohol derivatives the elimination ions [M-OH] + or [M-H 2 O-OH] + . With methane or isobutane as reagent gas monohydroxylated cholesterols yield five ions: the protonated molecular ion [M + H] + , molecular ion[M] + , hydride abstraction ion [M-H] + , and elimination ions [M-H 2 O + H] + and [M-2H 2 O + H] + , the principal ion uniformly being the [M-H 2 + H] + ion. Methane CI mass spectra of trimethylsilyl ether derivatives of the side-chain hydroxycholesterols exhibit unique fragmentation ions [C n H 2n OSi(CH 3 ) 3 ] + derived from α-cleavages diagnostic of the site of side-chain hydroxylation. |
