摘要：This report describes the trace analytical method of n-alkanes, based on the inclusion ability of urea, from a mixture of iso-alkanes, cycloalkanes, poly aromatic hydrocarbons and organic sulfur compounds. n-Alkane-urea inclusion complexes were formed by adding ethanol 2 ml of saturated with urea to 0.5 ml of a mixed solution of acetone and n-hexane (3 : 2) containing the above described compounds. The inclusion compounds formed in the hydrophobic medium were precipitated by adding ice-cold ethyl ether and then cooling for 5-10 min in an ice-bath. The precipitates were separated with centrifuge (3000 rpm, 6 min) at 5°C from organic reaction medium. The precipitates were dissolved in 30 ml of 4% Na2SO4 and extracted with n-hexane (total volume, 20 ml), and also the supernatant by the addition of 30 ml of 4% Na2SO4 was treated with n-hexane (20 ml). n-Alkanes were measured in the former n-hexane solution while iso-alkanes and/or others in the latter by each gas chromato-graphic analysis. The recoveries of n-alkanes of C12 and C14 were 67% and 80%, respectively, being recoverd in the past reports with yield of under 40%. The yields of n-alkanes of C15-C28, 2, 2, 4, 4, 6, 8, 8-heptamethylnonane, heptylbenzene, pristane, dibenzothiophene and 3, 4-benzpyrene were 91% on the average, 77%, 79%, 80%, 83% and 84%, respectively. This analytical method was applied to the solvent extracts of a bait of cultured fish and the sea bottom sediment.
