Materials
SPO was purchased from Qinghai Kangpu Co.,
Ltd.
(Xining, Qinghai). Standards of 37 fatty acid methyl esters were
purchased from Sigma-Aldrich Chemical Co., Ltd. (Shanghai, China).
Hexane, methanol, ethanol, acetone and isopropanol were provided by
Sinopharm Chemical Regent (Shanghai, China). All of the other reagents
were analytically pure and were obtained from Sinopharm Chemical Reagent
Co., Ltd. (Shanghai, China).