RAPID CO-PRECIPITATION-SEPARATION OF TRACE AMOUNTS OF LEAD IN TABLE SALT BY THE PRECIPITATION SYSTEM OF PAN-Ni(Ⅱ) WITH Mn(Ⅱ) AS INTERNAL STANDARD AND ITS DETERMINATION BY FAAS

Trace amounts of lead in table salt were separated by co-precipitation with PAN-Ni(Ⅱ),and adding Mn(Ⅱ) ion as internal standard.Conditions for co-precipitation were optimized.Under the optimized reaction conditions,the internal standard Mn(Ⅱ) and Pb(Ⅱ) ions in the sample were quantitatively co-precipitated by PAN-Ni(Ⅱ),and both of the Mn(Ⅱ) and Pb(Ⅱ),also including Ni(Ⅱ) were present in the precipitate with good homogeneity,and a definite ratio was kept between Pb(Ⅱ) and Mn(Ⅱ),or between Ni(Ⅱ) and Mn(Ⅱ).The mass of lead in the sample was calculated from the ratio of absorbances APb1 and AMn1 of lead (Pb1) and manganese (Mn1) found in the co-precipitate.Lead content (Pb0) in the original sample was calculated by the following formula: mPb0=APb1/AMn1·mMn0.It was shown by experimental results that by the separation mentioned above,the matrix interference was effectively eliminated.Detection limit of this method was found to be 3.18×10-2mg·L-1.In the analysis of 3 kinds of table salt by this method.RSD′s (n=6) obtained were less than 4.3%,and recoveries in the range of 95.4%-101.6% were found.