新型酸性光亮镀锡铜合金镀液中锡的测定

Determination of Tin in Plating Bath for Novel Acidic Bright Tin-Copper Alloy Coating

为消除Cu2+的干扰,防止Sn2+,Sn4+的水解,建立了一套采用解蔽返滴定法,不经分离对新型酸性光亮镀锡铜合金镀液中的锡进行测定的分析方法。在pH值为5.5的醋酸吡啶缓冲溶液中,用2.5gNH4F解蔽,4滴XO、1mLCPB指示终点,锌盐返滴定镀液中的锡。结果表明,选择3.0mLH2O2,1.0mL甘油,加热6min对测定结果无影响。1.0mL抗坏血酸,2.0mL硫脲可掩蔽Fe3+及Cu2+的干扰。该法操作简便快速,准确度高,加标回收率达99.80%以上。适合镀锡、锡铜合金镀液中锡的测定。

A method to directly determine the tin in the plating bath for a novel acidic bright tin-copper alloy coating was established based on releasing back titration, which was aiming at eliminating the reference of Cu 2+ and preventing the Sn 2+ and Sn 4+ from hydrolysis. Thus the tin was released from the plating bath using 2.5 g ammonium fluoride as the releasing agent in a acetic-pyridine buffer solution of a pH value 5.5, and then inversely titrated using zinc nitrate standard solution in the presence of xylenol orange as an indicator. The results indicated that the introduction of 3.0 mL hydrogen peroxide and 1.0 mL glycerol and heating for 6 min had no effect on the determination result. The interference of Fe 3+ and Cu 2+ could be sheltered by the addition of 1.0 mL ascorbic acid and 2.0 mL sulfourea. The method had the advantage of easy operation, expeditiousness, high accuracy, and good recovery rate as much as over 99.80%, and could be directly applied to determine the tin in the plating bath for acidic bright tin or tin-copper alloy coating.