氢化物-KI3-罗丹明6G体系荧光法测定痕量硒

Fluorescence Determination of Trace Se with the Hydride-KI_3-Rhodamine 6G System

硒是人和动物体内必需的微量元素,但硒摄入过量会导致硒中毒,因此痕量硒的准确检测具有非常重要的意义。本研究目的是建立一种灵敏、具有选择性测定硒的氢化物发生荧光分析新方法。在0.36mol·L^-1硫酸介质中,以NaBH4为还原剂,Se（Ⅳ）被还原为H2Se气体。用KI3溶液作为吸收液,I3^-被H2Se气体还原成I^-。当加入罗丹明6G时,罗丹明6G（Rh6G）与吸收液中的I3^-形成缔合微粒导致荧光强度减弱。有Se（Ⅳ）存在时,罗丹明6G与I3^-结合较少,剩余量增多,荧光强度增强。优化了分析条件,选择0.36mol·L^-1 H2SO4,21.6g·L^-1 NaBH4,23.3μmol·L^-1 Rh6G,50μmol·L^-1 KI3,激发波长为480nm时瑞利散射不影响荧光测量。在选定条件下,Se（Ⅳ）浓度在0.02～0.60μg·mL^-1范围内与562nm处的荧光强度增加值ΔF呈线性关系,线性回归方程为ΔF562nm=12.6c＋20.9,方法检出限为0.01μg·mL^-1。考察了共存物质对氢化物发生-分子荧光法测定5.07×10^-6 mol·L^-1 Se（Ⅳ）的干扰情况。结果表明该法具有较高的选择性,即0.5mmol·L^-1的Ba^2＋,Ca^2＋,Zn^2＋,Fe^3＋,0.25mmol·L^-1的Mg^2＋,0.05mmol·L^-1的K^＋,0.2mmol·L^-1的Al^3＋,0.025mmol·L^-1的Te（Ⅵ）均对测定不产生干扰。Hg^2＋,Cd^2＋和Cu^2＋等易与Se（Ⅳ）结合生成沉淀,干扰Se（Ⅳ）的测定,这些干扰离子可以通过加入络合剂消除干扰。该氢化物发生-分子荧光光谱新方法已用于水中痕量硒的测定,结果满意,回收率在91.8%～107.1%之间。

Se is a necessary trace element for human and animals,but the excess intake of Se caused poison.Thus,it is very important to determination of Se in foods and water.The target of this study is development of a new,sensitive and selective hydride generation-molecular fluorescence method for the determination of Se.In 0.36mol·L^-1 sulfuric acid,NaBH4 as reducing agent,Se（Ⅳ）is reduced to H2 Se.Using I3^-solution as absorption liquid,I3^-is reduced to I^-by H2 Se.When adding rhodamine6 G,Rhodamine 6Gand I3^-form association particles,which lead to the fluorescence intensity decreased.When Se（Ⅳ）existing,Rhodamine 6Gand I3^-bind less,And the remaining amount of Rhodamine 6Gincrease.So the fluorescence intensity is enhanced.The analytical conditions were optimized,a 0.36mol·L^-1 H2SO4,21.6g·L^-1 NaBH4,23.3μmol·L^-1 rhodamine6 G,and 50μmol·L^-1 KI3 were chosen for use.When the excitation wavelength is at 480 nm,the Rayleigh scattering peak does not affact the fluorescence recording,and was selected for determination of Se.Under the selected conditions,Se（Ⅳ）concentration in the 0.02～0.60μg·mL^-1 range and the increase value of the fluorescence intensity（ΔF）at 562 nm linear relationship.The linear regression equation isΔF562nm=12.6c＋20.9.The detection limit was 0.01μg·mL^-1.The influence of coexistence substances on the hydride generation-molecular fluorescence determination of 5.07×10^-6 mol·L^-1 Se（Ⅳ）was considered in details.Results showed that this new fluorescence method is of high selectivity,that is,0.5mmol·L^-1 Ba^2＋,Ca^2＋,Zn^2＋and Fe^3＋,0.25mmol·L^-1 Mg^2＋,0.05mmol·L^-1 K^＋,0.2mmol·L^-1 Al^3＋,0.025mmol·L^-1 Te（Ⅵ）do not interfere with the determination.The influence of Hg^2＋,Cd^2＋and Cu^2＋that precipitate with Se（Ⅳ）,can be eliminated by addition of complex reagent.This hydride generation-molecular fluorescence method has been applied to determination of trace Se in water samples,with a recovery of 91.8%～107.1%.