2.1 Materials
Samples of mixed tocopherols (7.17% α-tocopherol, 1.47% β-tocopherol,
60.04% γ-tocopherol, 24.41% δ-tocopherol, 6.98% others) were
purchased from Healthful Biotechnology Co., Ltd. (Xi’an, China). Fresh
refined lard (acid value 0.14 mg KOH/g, peroxide value 0.39 mmol/kg)
without any antioxidants was obtained from Jiuyuan Co., Ltd. (Tianjin,
China). Standards of α-tocopherol (purity > 98.0%),
γ-tocopherol (purity > 98.0%) and δ-tocopherol (purity
> 98.0%) were purchased from Aladdin Bio-Chem Technology
Co., Ltd. (Shanghai, China). Silica gel (200-300 mesh, irregular) used
for column chromatography and silica G plates (10 × 10 cm) were obtained
from Haiyang Chemical Group Co., Ltd. (Qingdao, China). Quartz sand
(silicon dioxide, 40-80 mesh, irregular) was purchased from Kemiou
Chemical Reagent Co., Ltd. (Tianjin, China). All chemicals and solvents
used were of analytical or HPLC grade.