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食品中微量铀的光度法测定,目前国内常用铀试剂Ⅲ测定六价及四价铀。前者的灵敏度尚不能满足食品中微量铀的测定要求,后者虽然灵敏度较高,但需将铀从六价还原至四价,既增加操作,又造成重复性不够好。前人报导了在溴化十六烷吡啶(CPB)存在下,铀与铬天青S(CAS)形成蓝色胶束状络合物,当pH为4.8,在625nm处,其克分子吸光系数(ε)为9.9×10~4。在2N硝酸中,三辛基氧膦(TOPO)对铀有很高的萃取能力及较大的分离系数。用抗坏血酸
Determination of Trace Uranium in Food by Spectrophotometry. At present, uranium reagent Ⅲ commonly used in China is used to determine hexavalent and tetravalent uranium. The sensitivity of the former is not enough to meet the requirement of trace uranium in food. Although the latter has higher sensitivity, uranium needs to be reduced from hexavalent to quaternary, which not only increases the operation but also makes the repeatability not good enough. It has been previously reported that uranium forms a blue micellar complex with chrome azure S (CAS) in the presence of cetylpyridinium bromide (CPB). At a pH of 4.8, at 625 nm, its molecular extinction coefficient (ε) is 9.9 × 10 -4. In 2N nitric acid, trioctylphosphine oxide (TOPO) has a high uranium extraction capability and a large separation factor. With ascorbic acid