Hp 6890 series 2 plus

Sterol contents and composition were determined by GC, following the procedure described by the AOCS (American Oil Chemists’ Society) method (Ch6–91:2011) [19 ]. Briefly, lipids (50 mg) were saponified with 2 mL 1 M methanolic KOH for 18 h at room temperature, then 2 mL of water was added and the unsaponifiables were extracted three times using 3 mL of hexane/methyl tert-butyl ether (1:1, v/v). The solvent was evaporated under a stream of nitrogen. Dry residues were dissolved in 0.2 mL pyridine and silylated with 0.8 mL of SylonBTZ (Trimethylsilyl N-trimethylsilylacetamidate + N-(Trimethylsilyl)imidazole + Chlorotrimethylsilane). Derivatives of the sterols were separated on a HP 6890 series II Plus (Hewlett Packard, Palo Alto, USA) equipped with a DB-35MS capillary column (25 m × 0.20 mm, 0.33 μm; J&W Scientific, Folsom, CA). Hydrogen was used as the carrier gas at a flow rate of 1.5 mL/min. An internal standard, 5α-cholestane, was used for sterol quantification [18 (link)].

The content of phytosterols was analyzed according to AOCS Official Method Ch 6-91 [22 ]. The shea butter samples were saponified with 1 M methanolic KOH for 18 h. Then, phytosterols were extracted with hexane/methyl tert-butyl ether (1:1, v/v). The extracts were evaporated and pyridine and BSTFA + 1% TMCS were added to dry residues. For separation, an HP 6890 series II Plus (Hewlett Packard, Palo Alto, CA, USA) was used, equipped with DB-35MS capillary column (25 m × 0.20 mm, 0.33 μm; J&W Scientific, Folsom, CA, USA). A sample of 1.0 μL was injected in splitless mode. The initial oven temperature was 100 °C for 5 min, then the temperature was programmed to 250 °C at 25 °C/min, held for 1 min, then further programmed to 290 °C at 3 °C/min and held for 20 min. The carrier gas was hydrogen (1.5 mL/min). Phytosterols were identified by comparison of retention data with standards and GC/MS (7890A/5975C VL MSD with Triple-Axis Detector, Agilent Technologies Inc., Santa Clara, CA, USA) using the same chromatographic conditions as described above.