Determination of trace chromium (VI) ion in chrome tanning agents by flow injection analysis

A large amount of Cr3+ ion can significantly interfere with the determinati on of trace amounts of Chromium (VI) ion in chrome tanning agents. Therefor e, two new preparation methods of precipitation and adsorption are put forw ard here to eliminate the interference of Cr3+ ion. According to the experiments, magnesium oxide (MgO) was chosen as the best precipitating agent for Cr3+ ion, the adsorption efficiency of the chelatin g resin was better than any other resin. The content of chromium (VI) ion was determined by flow injection analysis (FIA). In order to assess the feasibility of two preparation methods, tests of precision and recovery were conducted. The results show that the variat ion coefficient is less than 1.6 percent with the recoveries ranging from 9 5.0% to 102%. Therefore, the precipitation and adsorption are feasible for the preparation of Cr (VI) samples in chrome tanning agents. Moreover, they have such advantages as simple and convenient preparation.