用丁基罗丹明B和钨酸盐测定痕量锡的研究

Study on the Determination of Trace Amounts of Tin(Ⅳ) with Tungstate and Butylrhodamine B

聚乙烯醇（ＰＶＡ）存在下，锡与钨酸盐形成锡钨杂多络阴离子，继而与丁基罗丹明Ｂ（ＢＲＢ）形成离子缔合物。离子缔合物的最大吸收位于５６５ｎｍ，表观摩尔吸光系数ε为２．５４×１０７Ｌ·ｍｏｌ－１·ｃｍ－１，服从比耳定律范围０～６０ｎｇ／２５ｍＬ，测定限（３σ）０．０７３ｎｇ／ｍＬ（ｎ＝１２），对４０ｎｇ／２５ｍＬ锡测定的相对标准１．４５％（ｎ＝１１），离子缔合物至少稳定２４０ｈ。考察了４０多种共存离子的影响，大多数常见元素不干扰。研究了离子缔合物的红外光谱，锡钨杂多络阴离子具有Ｋｅｇｇｉｎ结构。测定锡的适宜条件为［Ｈ２ＳＯ４］＝１．３２ｍｏｌ／Ｌ，［ＷＯ２－４］＝６．０５×１０－５ｍｏｌ／Ｌ，［ＢＲＢ］＝３．０×１０－５ｍｏｌ／Ｌ和ＰＶＡ０．８ｇ／Ｌ。本法已用于某些合金钢和锌合金中锡的测定，结果满意。

Tin(Ⅳ) reacts with sodium tungstate to form tinotungstic heteropoly acid.The ion association complex of tinotungstic heteropoly acid with butylrhodamine B(BRB) is formed in the presence of polyvinyl alcohol(PVA).The ion association complex exhibits maximum absorbance at 565nm with an apparent molar absorptivity of 2.54×10 7L·mol -1 ·cm -1 and follows Beer's law at 0～60ng/25mL for tin.The detection limit (3σ) is 0.073 ng/mL( n =12).The colour of the aqueous solution is stable for at least 240h.The interferences of over 40 foreign ions were tested.Most common ions did not interfere.The IR spectra was discussed and tinotungstic heteropoly complex anion was Keggin stucture.The optimum conditions for the determination of tin are:[H 2SO 4]=1 32mol/L,[WO 2- 4]=6 05×10 -5 mol/L,=3 0×10 -5 mol/L and PVA 0 8g/L.The method was applied to the determination of tin in some steels and zinc based alloy samples.The results obtained agreed well with recommended values and the recovery was satis factory.