原子荧光法测定食品总砷的前处理方法探讨

Different Pretreatments for Determination of Total Arsenic in Foods by Atomic Fluorescence Spectrometry

通过研究两种不同混酸(硝酸-高氯酸和硝酸-高氯酸-硫酸)对小麦粉、蔬菜粉、海藻粉进行前处理,原子荧光法对其总砷进行测定。结果表明:测定小麦粉、蔬菜粉中总砷时,两种前处理方法得出的结果基本一致;对海藻粉样品,使用高沸点硫酸处理,消化效果明显提高,使用硫酸消化海藻样品测定结果通过了国际能力验证(比利时IMEP 112)的检验。小麦粉、蔬菜粉样品中总砷的存在形式主要以无机砷形态存在,低沸点酸适合砷存在形态相对简单的样品,但对于富含有机砷的藻类样品,只有使用高沸点硫酸进行处理,藻类中有机砷才能充分分解转化为无机砷,从而为原子荧光光谱仪准确测定。

An atomic fluorescence spectrometric（AFS） method was developed for the determination of total arsenic in wheat,vegetable and algae.Two sample pretreatments were proposed based on digestion with either HNO3-HClO4or HNO3HClO4-H2SO4.Basically similar results were obtained by both sample pretreatments.Improved digestion of algae was achieved by using H2SO4due to its high boiling point,and the validity of this digestion method was confimed by proficiency testing according to IMEP-112： Total and Inorganic Arsenic in Wheat,Vegetable Food and Algae.The chemical speciation of inorganic arsenic was dominant in wheat and vegetable.Low boiling point acid was suitable for digestion of samples with simple chemical speciation of arsenic and therefore enabled accurate determination of total arsenic.In the case of algae samples,which are rich in organic arsenic,full conversion of organic arsenic to inorganic arsenic could only achieved by the use of high boiling point acid for accurate determination.