subsequent resolution of each fraction into dhca and thca was attained by gc on a cross-linked 5 % phenylmethylsilicone fused-silica capillary column where 5 beta-cholestanoic acids were monitored with a characteristic carboxylate anion [ m-181 ] - in the nici mode using isobutane as a reagent gas .
C0003075
anion
C0022023
nici