锡(Ⅳ)-柠檬酸-溴邻苯三酚红-溴化十六烷基三甲基铵显色体系及其应用

STUDY ON THE COLOUR REACTION OF TIN(Ⅳ) WITH CITRIC ACID AND BROMOPYROGALLOL RED (BPR) IN THE PRESENCE OF CTMAB

在 pH 1.8的氯乙酸缓冲溶液中和有溴化十六烷基三甲基铵存在下 ,锡 (Ⅳ )和柠檬酸及溴邻苯三酚红形成 1∶1∶2的橙红色胶束混配络合物。该络合物最大吸收波长为 5 34nm ,表观摩尔吸光系数为 1.72× 10 5L·mol- 1·cm- 1。锡 (Ⅳ )浓度在 0～ 0 .2 4mg·L- 1范围内符合比耳定律。方法的灵敏度、选择性和稳定性均比无柠檬酸存在时好 ,可用于食品包装盒中微量锡的测定。

In a chloroacetic acid buffer solution of pH 1.8, and in the presence of CTMAB, tin(Ⅳ) reacts with citric acid and BPR forming an orange-red colored micellar mixed ligand complex having its mole ratio of Sn(Ⅳ)∶Cit∶BPR=1∶1∶2. The absorption maxima of this complex lies at the wavelength of 534nm, with its molar absorptivity of 1.72×10 5L·mol -1·cm -1. Beer′s law is obeyed in the range of 0 to 0.24mg of Sn(Ⅳ) per liter of solution. This ternary complexing system behaves with higher sensitivity, selectivity and stability than the complexing system without citric acid. A method of determination of micro amounts of tin in food packing box is established based on the above mentioned color reaction, and the results obtained are satisfactory.