Studies On The Separation And Preconcentration Of Trace Metals By Coprecipitation And Determination With Flame Atomic Absorption Spectrometry

With the development of science technology and the improvement of living standards, sensitive, rapid, reproducible, simple and accurate analytical methods are required for the determination of trace elements in environmental samples. However, the direct determination of trace element with atomic spectroscopic method is not satisfying. Under these circumstances, a separation and enrichment step prior to their determinations may be beneficial. The coprecipitation method is widely used for the concentration of trace metal ions prior to their flame atomic absorption spectrometric determination. According to its simplicity rapidity and ability to attain a high concentration factor among the preconcentration methods, it is one of the most effective multi-element preconcentration methods.In this article, we applyed PAR-Ni2+,PAR-Fe3+as coprecipitant respectively to determinate iron、zinc、copper and lead in environmental samples firstly. The analytical parameters including the impact of carrier elements, amount of reagent and carrier elements, pH, the standing time of the precipitate, sample volume and matrix components were examined in detail. A simple and sensitive method based on coprecipitation of Fe3+、 Zn2+、Cu2+with Ni2+-4-(2-pyridylazo)-resorcinol was developed. When the concentration of Fe3+was0.4mg/L, the precision of the method was1.8%(n=11), the detection limit (DL)was0.73μg/L (3σ).The method has been applied to the determination of Fe3+in water samples and the recoveries of Iron ranging from94.6%to105.8%. When the concentration of Zn2+was0.1mg/L, the precision of the method was2.2%(n=11), the detection limit (DL)was0.38μg/L (3σ).The method has been applied to the determination of Zn2+in lake water and the milk tea powder samples, the recoveries of Zinc ranging from97.0%to99.1%. When the concentration of Cu2+was0.3mg/L, the precision of the method was2.6%(n=11), the detection limit (DL)was0.65μg/L (3σ). The method has been applied to the determination of Cu2+in steel sample with satisfactory results. A method based on coprecipitation of Pb2+with Fe3+-4-(2-pyridylazo)-resorcinol was developed. When the concentration of Pb2+was0.3mg/L, the precision of the method was1.6%(n=11), the detection limit (DL)was0.93μg/L (3σ). The method has been applied to the determination of Pb2+in lake water and the milk tea powder samples, and the recoveries of Lead ranging from94.2%to98.3%. The effect of matrix can be overcome by the method and the highest preconcentration factor was30. The method proposed here was rapid and had good reproducibility. The method provided a new way to determinate trace metal ions with flame atomic absorption spectrometry.