^(14)C用于天然食品添加剂的检测

Natural food additives' testing by ^(14)C

粮食、水果、蔬菜、畜禽、鱼类中放射性同位素14C,原与大自然的14C是交换和平衡的,一旦收获、屠宰、宰杀,光合作用虽停止,14C平衡被破坏,但仍有14C-β放射性,只是其衰变率遵循指数函数(随时间而衰减)。石油与煤是埋藏于地下的腐烂植物,经3亿年以上的生化反应变迁而成,大大超过14C的10个半衰期,14C-β放射性早已衰变完不再存在,以石油热裂化气、天然气、煤干馏产品(煤焦油)为主要原料,通过基本有机合成与异构化、聚合、氢化、氧化等有机化学反应生产的合成添加剂,不含有放射性同位素14C。该原理可用来检测食品添加剂的14C-β放射性,确定生产原料是否为农副产品或有机化学合成产品,以及天然食品添加剂中是否混有合成添加剂。真实性检测步骤,将液体或固体食品添加剂样本通过不同的预处理和分离纯化制成闪烁液,采用液体闪烁计数器(经14C标准物质校正)测定其14C—β放射性,然后将数据与工作曲线进行分析与比较。

The radioactive isotope 14 Cexists in grains,fruits,vegetables,livestock and poultries,and fish. It is exchangeable and well-balanced with 14 C in nature. Once these plants and animals are harvested,slaughtered,and killed,the photosynthesis stops and 14 C balance is damaged. However,there is still 14C-β radioactivity,and its decay rate follows the exponential function（attenuate with time）. Petroleum and coal are formed by the rotted plants buried underground through more than 0.3 billion years by biochemical reaction and may be migrated. This period is longer than 10 times of half- life periods of 14 C,and 14C-β radioactivity has already decayed and no longer existed. The synthesized additives produced with thermal cracking gas of petroleum,natural gas,and products from coal distillation（coal tar）as the main material through organic chemical reactions like basic organic synthesis and isomerization,polymerization,hydrogenation,and oxidation which does not contain radioactive isotope 14 C. This principle can be used to test 14C-β radioactivity of food additives,and determine whether the raw materials are agricultural or sideproducts or organic chemical synthesis products,and whether the natural food additives are mixed with synthesized additives. Steps of authenticity testing were ：the liquid or solid food additives were madeinto scintillation solution through different pretreatments and separation and purification,use a liquid scintillation counter（rectified by 14 C standard substance）to determine its 14C-β radioactivity,and then working then the data were compared with working curves.