EDTA滴定法测定锡铋焊料中铋

采用盐酸-硝酸溶样，高氯酸冒烟，在硝酸介质中将锡转化成偏锡酸沉淀与铋进行分离，最后用EDTA滴定法测定铋含量，建立了一种测定锡铋焊料中高含量铋的方法。考察了硝酸用量、锡含量和干扰离子对测定的影响。结果表明，硝酸用量为30 mL时，锡可完全沉淀，铋不会水解，锡铋分离效果好；偏锡酸沉淀会对铋产生吸附和包裹，通过控制试样的称样量可降低干扰；与铋共存的 Cu²⁺、Fe³⁺、Sb、Te、In³⁺干扰滴定，其中Cu²⁺、Fe³⁺、Sb、Te可通过加入掩蔽剂或控制滴定条件消除干扰，In³⁺与EDTA络合，使铋的测定结果偏高，可用原子吸收光谱法或电感耦合等离子光谱法测定后从滴定总量中进行扣除。本方法用于Sn20-Bi焊料和Sn38-Bi焊料中铋的测定，测得结果与氢溴酸挥发-EDTA滴定法一致，相对标准偏差（RSD, n=8）小于或等于0.14%。

Determination of bismuth in tin-bismuth solder by EDTA titration

A method for the determination of high content of bismuth in tin-bismuth solder was proposed.After the sample was dissolved by hydrochloric acid and nitric acid and fumed with perchloric acid,bismuth in the sample was separated from tin by converting tin to metastannic acid precipitate in nitric acid medium.Then,it was determined by EDTA titration.The influences of nitric acid dosage,the content of tin,and interference ions on determination results were investigated.It was found that,when the nitric acid dosage was 30 mL,bismuth could be completely separated from tin with the precipitation of tin and the hydrolysis of bismuth.Moreover,metastannic acid precipitate would produce absorption and encapsulation for bismuth,which could be reduced by controlling the sample weight.The coexistent ions of Cu2+,Fe3+,Sb(Ⅴ)、Te(Ⅳ) and In3+ interfered with the titration.Thereinto,the interference of Cu2+,Fe3+,Sb(Ⅴ)and Te(Ⅳ) could be eliminated by adding masking agent or controlling titration condition.The complexation of In3+ and EDTA raised the determination results.Such interference could be eliminated by deducting the indium content determined by atomic absorption spectrometry or inductively coupled plasma spectrometry from the determination results by titration.The method has been applied to the determination of bismuth in Sn20-Bi and Sn38-Bi tin-bismuth solder samples,the results were concordance with those obtained by hydrobromic acid volatilization-EDTA titration,and the relative standard deviations(RSDs,n=8)were less than or equal to 0.14%.