氢化物发生-双通道原子荧光光谱法同时测定茶叶和木耳中硒及汞量

经洗净烘干并磨碎的试样在硝酸中浸泡过夜后在硝酸-高氯酸中消解,蒸发至冒白烟并继续蒸至近干,加入一定量的盐酸微沸1～2min,使硒(Ⅵ)还原为硒(Ⅳ),溶液用盐酸(5+95)定容至50mL。此溶液由载流盐酸(5+95)溶液送入氢化物发生器,与还原剂10g.L-1 KBH4溶液混合并反应生成硒的氢化物,样品中汞则生成原子态汞蒸气。两者由载气引入原子化器,在选定的仪器工作条件下,测定硒及汞的荧光强度。在实际样品中,硒、汞共存的浓度比未超过10,在同时测定中两者之间互不干扰。按所提出的条件测定,硒、汞的质量浓度在1.0～5.0μg.L-1范围内与相应的荧光强度值之间呈线性关系,方法的检出限(3s/k)依次为0.077,0.009 8μg.L-1。对仪器测定精密度做了试验,测得其相对标准偏差(n=7)依次为1.98%,1.31%。

Simultaneous Determination of Selenium and Mercury in Tea and Auricularia Auricula Judae by HG-AFS with Double Channels

The washed,dried and pulverized sample was soaked in HNO3 overnight,then digested in HNO3-HClO4 mixed acid,and evaporated to fumes of HClO4 and further to near dryness.Definite amount of HCl was added to dissolve the residue and boiled gently for 1-2 min to reduce Se(Ⅵ) to Se(Ⅳ).The solution was made up to 50 mL with HCl(5+95),which was carried over by the carrier solution of HCl(5+95) and mixed with the reductant,10 g·L-1 KBH4 solution in the hydride generator.Selenium hydride together with the atomic mercury vapour was introduced into the atomizer by the carrier gas and fluorescence intensity of Se and Hg were measured under the optimized instrumental conditions.Since the concentration ratio of Se to Hg was less than 10 in substantial samples,no interference was found between Se and Hg in co-existence.Under the optimized conditions,linear relationships between values of fluorescence intensity and mass concentration of Se and Hg were found in the same range of 1.0-5.0 μg·L-1,with detection limits(3s/k) of 0.077,0.009 8 μg·L-1 respectively.Precision of the instrument was tested and values of RSD′s(n=7) found were 1.98%(for Se) and 1.31%(for Hg).