壳聚糖分离富集-催化荧光猝灭法测定痕量锡

Catalytic fluorescent quenching determination of trace tin after preconcentration and separation with chitosan

研究了在pH4．0邻苯二甲酸氢钾-氢氧化钠介质中，痕量锡催化过氧化氢氧化3-（4＇-硝基苯基）-5-（2’-胂酸基偶氮）若丹宁（4NRAAP）而使荧光显著猝灭，由此建立了催化荧光猝灭法测定痕量锡的新方法。该体系的激发和发射波长分别为307nm和408nm，反应表观活化能为76．66kJ／mol，反应速率常数为8．4×10^-2／s，测定锡的线性范围为0～14．0μg／L，检出限为1．9×10^-7g／L。采用壳聚糖分离富集，控制吸附酸度约为pH4．0，然后采用H2SO4（4＋96）溶液进行洗脱时，只有Sn^4＋被洗脱下来，消除了共存离子的干扰。对壳聚糖富集无机锡机理进行了探讨。应用该方法测定合金和水样品中痕量锡，相对标准偏差在4．0％以下，回收率为97％～103％，与ICP—AES方法相比，结果基本一致。

A new catalytic kinetic fluorescent quenching method for determination of trace tin was investigated. The method was based on the catalytic effect of tin on oxidation of 3-（4＇-nitrophenyl）-5- （2 ＇-arsenoxylphenylazo） rhodanine by hydrogen peroxide in potassium hydrogen phthalate sodium hydroxide （pH=4.0）. The excitation wavelength and emission wavelength of the system were 307 nm and 408 nm, respectively. The apparent activation energy was 76.66 kJ/mol. The reaction rate constant was 8.4 × 10^-2/s. Under the optimum conditions the decrease of fluorescence intensity has a linear relationship with the concentration of tin in the range of 0-14.0 μg/L,with a detection limit of 1.9 × 10^-7g/L. At pH 4.0, Sn（Ⅳ） in the sample was preconcentrated and separated by chitosan, then Sn^4＋ was washed off with sulfate acid （4＋96）, by which only Sn（Ⅳ） was eluted to eliminate the interference from coxistent ions. The mechanism of preconcentration and separation of tin by chitosan was discussed. The method was applied in the determination of tin in water and alloy samples with recoveries of 97 %-103%（RSD〈4.0%）. The determination results were in accordance with those of ICPAES.