Oil spillage by causual boat accidents and/or discharge from boats and industrial sewages presently cause world-wide contamination of coastal sea water, beach and biota in the marine environment. Oil contamination in the estuaries of coasts has become a serious problem not only in industrial countries, but also in non-industial ones. In the industrial areas and v ic in i t ies, offensive odours in marine products were caused. ( OGATA et a l . 1973, 1975, 1976) For the fingerprint of oil pollution, n-alkanes, polyaromatic hydrocarbons are widely used in marine biota, sediments and human tissues. (BLUMER 1970, SUESS 1970, NAKANISHI et al . 1977) The authors selected sulfur conaining oil compounds pollution in marine products and reported contamination of sulfur compounds in oysters from the Seto Inland Sea. (NAKAMURA et al . 1975) These compounds were clarif ied as dibenzothiophene derivatives. (NAKAMURA et al . 1977) For the successive analyses of these compounds, gas chromatography on a capillary column and high pressure liquid chromatography (HPLC) technique were also reported. (WARNER 1975, NAKAMURA et a l . 1977)