The Study On Enrichment Using Rapid Coprecipitation Technique With Atomic Absorption Spectrometry

The preconcentration method plays an important role in improving the detection limit and sensitivity. Coprecipitation is widely used for concentration of trace metals prior to various determination techniques including flame atomic absorption spectrometry. However, the coprecipitation is sometimes troublesome and time-consuming during filtration, which is frequently used for collection of precipitate. The problem was not solved until a rapid coprecipitation technique was first proposed by Shigehiro and his colleges. They have suggested that GaPO₄ is an excellent coprecipitant for the rapid coprecipitation technique prior to FAAS determination of lead in waste water. This method does not require a complete collection of the precipitate, because the ratio of the recovery of Pb to that of Ga was almost constant regardless of the revovery of precipitate. Thus the time required for preconcentration by the coprecipitation is considerably shortened.In this work, we first investigated ways to apply Mn and Ni as internal standardizations to rapid coprecipitation technique using 8-QT-Mg(II), Mg(OH)₂ and APDC-Ni as coprecipitant respectively for FAAS determination of Pb, Cd, Cu, Fe, Co, Ni in beer and waste water. We verified that the carrier element, internal standardization and the coprecipitated metals must also be homogeneously distributed over the whole precipitate. The content of Ni and Mn are 150μg and 500μg respectively, which are far higher than the actual content of that in samples and thus can be neglect. In order to increase the amount of Mn, we used the secondary sensitivity line 403.1nm of Mn and 341.5nm of Ni as analytical line respectively and the results show it is practicable. The standard addition recovery is between 95.4%～104.2%. This method is proved simple, rapid and useful for the determination of trace metals in beer and water samples.