The content of total polar compounds in oil sample
was also determined based on the methods of AOCS Cd_20-
91(20)
and ISO 8420(21)
. A glass column (35 cm in length
and 2.1 cm in diameter) was used for chromatography. The
eluent was a mixture of petroleum and diethyl ether in the
ratio of 87 : 13 (v/v). The oil sample (2.5 g) was loaded into
the packed column and the non-polar fraction was eluted by
the eluent. The content of total polar compounds (%) was
calculated as the mass fraction of the total polar compounds
in the oil sample in percentage.