Flow system for pre-concentration and spectrophotometric determination of reactive mercury

Journal of the Brazilian Chemical Society

Rohwedder, Jarbas J. R.¹  Universidade Estadual de Campinas, Campinas, Brazil¹  Pasquini, Celio¹  Yonehara, Fernando S.¹ 

关键词: reactive mercury;    pre-concentration;    spectrophotometry;    flow analysis;   

DOI  :  10.1590/S0103-50532005000600007

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

A new flow system to pre-concentrate and determine reactive mercury in effluents by photometry is presented. The system is based on the reduction of the reactive mercury present in a 500 mL sample with a Sn(II) solution. The reduced mercury is swept out by an argon stream and carried to a straight glass tube (60 cm long, 3 mm i.d.) inclined in an angle of 15º. The inner surface of this tube has been previously covered by a renewable liquid layer of an oxidant solution containing H2O2 (12%, m/v) and HNO3 (3.0 mol L-1) produced after introduction and passage of a liquid monosegment containing those reagents. The swept Hg0 undergoes an oxidative process and the Hg(II) formed is retained in the layer. After a 10 min sweep time interval the argon flow is stopped and a reagent monosegment (350 µL) containing PAR [4-(2-pyridylazo)resorcinol], 1.0 x 10-3 mol L-1, in an ammonia/ ammonium chloride buffer (4.0 mol L-1; pH 9.0) is introduced and passes through the glass tube. A strongly coloured complex between PAR and Hg(II) is formed and carried to the detection system composed of a light emitting diode (LED, lmax = 525 nm) and a photodiode detector. Sample processing time is about 12 min. The system is washed and a fresh liquid layer is formed, preparing the system for a new determination. This method concentrates the sample by a factor of 148 and achieves a detection limit of 0.16 µg L-1.

【 授权许可】

Unknown