Determinazione on-line LC-GC-FID di Δ7-stigmastenolo e Δ8(14)-stigmastenolo in oli alimentari

The determination of Δ 7 -stigmastenos has been used for several years, to reveal the addition of seed oils to olive oil. At the same time techniques for removing Δ 7 -sterols have been developed making it difficult to reveal these adulterations. These techniques, however cause isomerization of sterols. Recently it has been determined that the Δ 7 -sterols are transformed in Δ 8(14) - and Δ 14 -sterols. The determination of Δ 8(14) -stigmasterol, deriving from the Δ 7 -stigmasterol isomerization, can be used to reveal the addition of desterolized seed oils to olive oil. In this paper a LC-GC-FID method is described, which improves the separation of Δ 7 -stigmastenol and Δ 8(14) -stigmastenol from the interfering substances. The method is rapid and efficient, it allows an accurate check of the limit proposed recently for these sterols.