US EPA

1483230 

Technical Report 

Determination of diphenyl in citrus fruits.) 

Hayashi, T; Kato; Watanabe, H; Hara; Tanimura A $ 

1972 

1 

Shokuhin Eiseigaku Zasshi / Journal of the Food Hygienic Society of Japan
ISSN: 0015-6426
EISSN: 1882-1006 

HAPAB/72/01122 

J 

J. Food Hyg. So; 13(1 

78-84 

Japanese 

10.3358/shokueishi.13.78 

HAPAB Diphenyl (biphenyl) is approved in Japan as a food additive for the impregnation of citrus fruit wraps to prevent rot in grapefruit, lemons and oranges. Biphenyl residues in the whole fruit must not exceed 70 ppm; a method has been developed for the determination of biphenyl in citrus fruits. A whole fruit is homogenized in water and the homogenate is steam-distilled with cyclohexane as the solvent. The cyclohexane solution is cleaned up by TLC on a silica gel plate containing a fluorescent indicator. The spot is extracted with cyclohexane and the absorption read at 248 nm. For the gas chromatographic determination, the biphenyl peak was separated from other peaks due to essential oils in the fruit with polyethylene glycol, and biphenyl was determined by the internal standard method using 2,3-dimethyl-naphthalene. Imported lemons contained 1.15 to 3.56 mg of biphenyl (UV) or 4.54 to 4.68 mg (GC). The discrepancy is assumed to be due to differences in the fruit surface area exposed to biphenyl vapor in the container, for when a known amount of biphenyl (5 or 10 mg/fruit) was added to the homogenate and determined as above, 91 to 96% recovery was achieved by either method. The average biphenyl concentration in imported oranges was 56.5 ppm, and this figure did not decrease significantly after 25 days of storage. Biphenyl is assumed to dissolve in the fruit peel oil. 1972