电位滴定法连续测定线路板裂解残渣中微量氯和溴

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

印刷电路板样品经热降解和去卤化处理后,所得试样残渣中残留的氯和溴离子用电位滴定法连续测定。采用硝酸银标准溶液作为滴定剂,滴定系在有一定量的硝酸钾存在的稀硝酸溶液中进行,滴定终点取滴定曲线上两离子突跃部分斜率的最大值处或其一次微分曲线上相应的最小值处。计算测定结果采用了标准曲线法及标准加入法,并对此两方法的精密度和准确度作了比较。结果表明:标准加入法具有更高的精密度,测定其相对标准偏差(n=6)为2.85%(溴离子)和1.86%(氯离子),经F检验法证明,特别对微量溴及氯的测定采用标准加入法更为有利。

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 RSDrs （n= 6） 2. 85% （for Br^-） and 1.86 （for Cl^-）. It was mote preferable to use the standard addition method, especially for determination of microamounts of Br^- and Cl^- ions, as proved by the F-test.