火焰原子吸收光谱法测定锡铅焊料中银

在采用火焰原子吸收光谱(FAAS)法对锡铅焊料(简称焊锡)中Ag进行测定时,Sn的存在会产生干扰。实验探讨了用FAAS测定时Sn对Ag的干扰,结果表明测定不大于2 μg/mL的Ag时,Sn最大允许量为5 mg/mL。据此,根据试样中Ag含量的高低,分别建立了分离Sn基体和不分离Sn基体后在1.8 mol/L HCl介质中用FAAS测定焊锡中Ag的方法。利用Ag⁺可与过量Cl^-反应生成 [AgCl₄]^3-可溶络合物的特点,当试样中 Ag质量分数大于0.02%时,采用HCl (3+1)-H₂O₂溶样或HCl-HBr-H₂O₂溶样及排Br后可直接用FAAS对试液进行测定;当Ag质量分数不大于0.02%时,采用HCl-HBr-H₂O₂体系溶样、排Br及挥发分离Sn基体后,再利用FAAS进行测定。实验表明,Ag质量浓度在0.2～2.5 μg/mL范围内呈线性关系,相关系数为0.999 96,检出限为0.004 μg/mL。干扰试验表明:在70～100 ℃低温下以HCl-H₂O₂排尽引入的Br和挥发分离Sn基体可防止Pb沉淀的溅跳;70%～90% Pb基体在HCl介质中可沉淀为PbCl₂,此时,需静置至澄清后再测定以防止Pb沉淀对待测试液抽吸产生影响。将实验方法用于焊锡代表样及标样中0.002 3%～1.1%中Ag的测定,测定结果与其他方法(萃取光度法或电位滴定法)或认定值基本一致,相对标准偏差(RSD,n＝9～11)为0.88%～4.8%。方法应用于实际样品分析,回收率为95%～106%。

Determination of silver in tin-lead solder by flame atomic absorption spectrometry

During the determination of Ag in tin-lead solder by flame atomic absorption spectrometry (FAAS), the presence of Sn would cause interference. The interference of Sn with Ag in determination by FAAS was discussed. The results showed that the maximum tolerant amount of Sn was 5 mg/mL during determination of Ag not higher than 2 μg/mL. As a result, a determination method of Ag in tin-lead solder was established by FAAS in 1.8 mol/L HCl medium, and whether the separation of Sn was required or not according to the content of Ag in sample. Take advantage of the characteristic of Ag⁺ which could react with excessive Cl^－ to form soluble complex of [AgCl₄]^3－, the sample solution could be directly determined by FAAS after dissolution with HCl (3+1)-H₂O₂ or dissolution with HCl-HBr-H₂O₂ followed by removing Br when the mass fraction of Ag in sample was higher than 0.02%. However, when the mass fraction of Ag in sample was not higher than 0.02%, the volatilization and separation of Br and Sn should be conducted after dissolving sample with HCl-HBr-H₂O₂ then followed by the determination of test solution by FAAS. The results showed that the mass concentration of As in range of 0.2-2.5 μg/mL had linear relationship with correlation coefficient of 0.999 96. The detection limit was 0.004 μg/mL. The interference tests indicated that the splashing of Pb precipitate could be prevented by removing Br and Sn with HCl-H₂O₂ at 70-100 ℃. About 70%-90% Pb matrix could be precipitated to PbCl₂ in HCl medium. At this time, the solution should be placed to clear before determination in order to prevent the influence of Pb precipitate on suction filtration of testing solution. The proposed method was applied to the determination of Ag (0.002 3%-1.1%) in representative samples and certifeid reference material of tin-lead solder. The results were basically consistent with those obtained by other methods (extraction spectrophotometry or potentiometric titration) or the certified values. The relative standard deviations (RSD, n=9-11) were between 0.88% and 4.8%. The actual samples were analyzed by this proposed method, and the recoveries were between 95% and 106%.