The availability of the threesolvents was evaluated by their solubility for the coprecipitateand influence on the detected elements in pyrolysis andatomization stage. We observed that membrane was dissolvedcompletely in DMF, but coprecipitate was dissolved partly toform slurry. In addition, background absorbance was very high in the determination of these elements so that the reliable and stable results could not be obtained. When sulfuric acidwas chosen,
homogeneous solution was formed, but the similar high background absorbance was found. As dilute sulfuric acid (2.0 M)
was in place of sulfuric acid, the same phenomenon of high background absorbance was found. While nitric acid (1.0, 2.0 and 3.0 M) was used, precipitate was dissolved, but membrane could not dissolve to avoid the influence resulted by it. Furthermore, low background absorption was suitable for the determination of these elements. We also observed that with increasing the concentration of nitric acid, the time of dissolution became fast. In order to fast dissolve coprecipitate and avoid the interference resulted nitric acid, 1.0 ml nitric acid solution (1:1) was added,and then diluted to 5.0 ml for determination.