Fig. 1.

Schematic depicting the EADSA method. In fraction-A cholesterol oxidase converts 3β-hydroxy-5-ene functions to 3-oxo-4-ene groups which are derivatised with [²H₅]GP. Any natural 3-oxo-4-ene containing sterols will be similarly derivatised with [²H₅]GP. In fraction-B cholesterol oxidase is absent so only oxosterols, e.g. 3-oxo-4-enes (and 7-oxo-5-enes), will become derivatised, in this case with [²H₀]GP. Deconvolution of data from fractions-A and -B provides the quantities of sterols with an original 3β-hydroxy-5-ene function (i.e. A-B), while fractions-B provide quantities of oxosterols.