原子荧光光谱法测定海水中砷(Ⅲ)和砷(Ⅴ)

Determination of As(Ⅲ) and As(Ⅴ) In Seawater with AFS

应用原子荧光光谱法,测定海水中的痕量As(Ⅲ)和As(Ⅴ).在弱酸性介质(PH5.6～6.0)中,海水中As(Ⅲ)与硼氢化钾(KBH4)作用,生成气态氢化物(AsH3),由氩气(Ar)作载气将其导入石英炉原子化器中,进而在氩氢火焰中原子化,基态原子砷受到特种空心阴极灯发射的特征光辐射后,产生荧光,通过检测器检测原子荧光的相对强度,利用荧光强度与溶液中砷含量呈正比的关系,测定海水中As(Ⅲ)含量,在此条件下,As(Ⅴ)不发生反应.在盐酸介质(强酸性)中,用硫脲和抗坏血酸还原As(Ⅴ)为As(Ⅲ),同法测定总砷量,用差减法求得As(Ⅴ)含量.

Trace As(Ⅲ) and As(Ⅴ) in the seawater are determined by using the method of atomic fluorescence spectroscopy.In the weak acid medium(PH5.6~6.0),As(Ⅲ) in the seawater can react with KBH4 to produce gaseous hydride(AsH3),using argon (Ar) as carrier gas to convey the hydride into quartz furnace atomic vessel, and then the hydride is atomized in the argon and hydrogen flame.After irradiated by the characteristic ray emitted by the special type hollow cathode lamp, the ground state atom arsenic will produce fluorescence. And then check the relative intensity of atom fluorescence through the check instrument. The content of As(Ⅲ) in the seawater is determined by using the relation of direct ratio between the fluorescence intensity and the arsenic content in the solution.Under the circumstances,As(Ⅴ) in the seawater doesn′t react with KBH4.In the hydrochloric acid medium(strong acid),As(Ⅴ) is deoxidized into As(Ⅲ) by thiourea and L-ascorbic acid and the total content of arsenic is determined by using the same method,and the content of As(Ⅴ) is then obtained by using the method of subtraction.