Analysis and occurrence of total N-nitroso compounds in the Japanese diet.

A quantitative technique for differentiating the total N-nitrosamides from the total N-nitroso compounds has been devised. The principle of this method is based on the chemiluminescence response of a nitroso compound under different denitrosating conditions. We also examined the effect of nitrite scavengers on the stability of N-nitroso compounds and found that both ammonium sulfamate and hydrazine sulfate can be satisfactorily used for the detection of chemiluminescence response with hydrogen bromide-acetic acid reagent. A survey of the occurrence of total N-nitroso compounds, total N-nitrosamides, volatile N-nitrosamines, nitrates and nitrites in the Japanese diet has been conducted. Fairly high levels of total N-nitroso compounds were detected in salt-fermented vegetables, the highest being 2 500 micrograms/kg in hakusai-zuke (salt-fermented Chinese cabbage), followed by 253 micrograms/kg in takuan (salt-fermented radish roots). It is noteworthy that the amounts of total N-nitroso compounds in these products almost coincided with those of total N-nitrosamides, although no appreciable amounts, or only trace quantities, of volatile nitrosamines could be detected in these vegetable products.