EDTA滴定法测定锡铅焊料中高含量镉

实验对已报道的EDTA络合滴定法测定锡铅焊料中高含量镉的方法进行了改进,通过将称样量增至1.50g和用六次甲基四胺缓冲溶液(pH=6.00±0.02)来替代乙酸-乙酸钠缓冲溶液的方法改善了EDTA络合滴定法测定锡铅焊料中镉的精密度,同时采用铅标准溶液代替镉标准溶液标定EDTA标准滴定溶液,避免了标定时指示剂出现僵化的现象。锡铅焊料样品以酒石酸、硝酸、盐酸溶解,采用酒石酸络合掩蔽锡、锑、铋等杂质元素,在pH 6.00的六次甲基四胺缓冲体系中,以二甲酚橙为指示剂,先用EDTA标准滴定溶液滴定了铅、镉总量,再以酒石酸钾钠和邻菲罗啉掩蔽镉,用EDTA标准滴定溶液滴定了铅含量,最后通过差减法计算得到了镉的含量。干扰试验表明,锡铅焊料样品中的杂质元素不干扰测定。方法用于锡铅焊料样品中镉质量分数在10.00%~20.00%的测定,结果与电感耦合等离子体原子发射光谱法(ICP-AES)一致,相对标准偏差(RSD,n=11)为0.28%~0.87%。

Determination of high content cadmium in tin-lead solder by EDTA titration

The reported determination method of high content cadmium in tin-lead solder by EDTA complexometric titration was modified. The determination precision of cadmium in tin-lead solder by EDTA complexometric titration was improved by increasing sample mass to 1.50 g and using hexamethylenetetramine buffer solution (pH=6.00±0.02) to replace acetic acid-sodium acetate buffer solution. Meanwhile, the EDTA standard titration solution was calibrated using lead standard solution instead of cadmium standard solution, avoiding the rigid phenomenon of indicator. The tin-lead solder sample was dissolved with tartaric acid, nitric acid and hydrochloric acid. The impurity elements such as tin, antimony and bismuth were masked by tartaric acid complexation. In hexamethylenetetramine buffer solution system at pH 6.00, the total content of lead and cadmium was firstly titrated by EDTA standard titration solution using xylenol orange as indicator. Then cadmium was masked with sodium potassium tartrate and phenanthroline. After determining the content of lead using EDTA titration solution, the content of cadmium could be calculated through subtraction method. The interference tests indicated that the impurity elements in tin-lead solder sample had no interference with the determination. The proposed method was applied for the determination of cadmium in tin-lead solder sample with mass fraction in range of 10.00%-20.00%. The found results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES). The relative standard deviations (RSD, n=11) were between 0.28% and 0.87%.