ICP-AES Determination of Cr(Ⅵ) in Certain Special Samples-Preliminary Separation of Cr(Ⅲ) by co-Precipitation

ICP-AES was applied to the determination of Cr(Ⅵ) in certain special samples,especially those with deep color or slight turbidity.Interferences of Cr(Ⅲ) and some other co-existing metal ions were eliminated by precipitation with aq.ammonia at pH 9.5 using Fe(Ⅲ) ion as carrier,and Cr(Ⅵ) was determined in the filtrate by ICP-AES.It was proved that 100 mg·L-1 of Cr(Ⅲ) were tolerable and the recovery of Cr(Ⅵ) obtained,after precipitation were very near to 100%.Detection limit (3σ) of the method was found to be 0.054 mg·L-1.The proposed method was used for the determination of Cr(Ⅵ) in presence of Cr(Ⅲ) in a sample of yellow colored paint which was digested with conc.HNO3 preliminarity,the value of RSD′s (n=7) obtained were 1.3%.