Successive Potentiometric Titration of Microamounts of Chloride and Bromide in Pyrolytic Cracking Residue of Printed Circuit Board

Sample of printed circuit board was treated by thermal degradation and dehalogenation,and residual amounts of chloride and bromide in the sample residue were determined successively by potentiometric titration.Silver nitrate standard solution was used as titrant and titration was carried out in a dil-HNO3 solution in presence of an appropriate amount of KNO3.End point of titration was taken at the maxima of slope of the titration curve or their respective minima of the 1st derivative of titration curve.Results of determinations were obtained by either the standard curve method or the standard addition method.Comparative study on the precision and accuracy of the two calculation methods mentioned above was performed and as shown by experimental results,higher precision was obtained with the standard addition method,giving values of RSD′s (n=6) 2.85% (for Br-) and 1.86 (for Cl-).It was more preferable to use the standard addition method,especially for determination of microamounts of Br- and Cl- ions,as proved by the F-test.