碘量法测定掺锑二氧化锡粉中锡

采用碘量法测定锡时,多采用氢氧化铍共沉淀分离法来消除共存元素的干扰,但该干扰消除方法流程较长,操作繁琐。实验详细考察了掺锑二氧化锡粉试样中共存元素对碘量法测定锡的干扰。结果发现,除锑外掺锑二氧化锡粉中其他共存元素对碘量法测定锡的干扰均可忽略;在试液中加入还原铁粉将锑还原成单质后可通过过滤实现锑与锡的分离,进而消除锑对测定的干扰。据此,采用过氧化钠熔融分解试样,在试液中加入还原铁粉后将锑还原为单质后过滤以分离除去试液中锑,用铝片将锡还原为二价,以淀粉为指示剂,实现了碘量法对掺锑二氧化锡粉中锡的测定。采用实验方法对5个掺锑二氧化锡粉试样中的锡进行测定,结果的相对标准偏差(RSD,n=9)为0.14%~0.22%,加标回收率在99.8%~100.4%之间。5家实验室采用实验方法分别对上述5个试样进行测定,并对所得数据进行统计分析,结果表明再现性限R值在0.36%~0.45%之间。将高纯二氧化锡粉和高纯三氧化二锑粉分别按质量比85∶15和75∶25配制成6#和7#掺锑二氧化锡粉模拟试样,按照实验方法进行测定,结果与理论值相符。

Determination of tin in antimony-doped tin oxide powder by iodometry

During the determination of tin by iodometry, the interference of coexisting elements is usually eliminated by co-precipitation separation method using beryllium hydroxide. However, this method has long process and tedious operation.The interference of coexisting elements in antimony-doped tin oxide powder samples with the determination of tin by iodometry was systemically investigated. It was found that the interference of coexisting elements in antimony-doped tin oxide powders was negligible except for antimony. After adding reduced iron powder into the test solution to reduce antimony to elementary substance, the separation of antimony from tin could be achieved by filtration, thus eliminating the interference of antimony with the determination of tin. In experiments, the samples were decomposed by fusion with sodium peroxide. The reduced iron powder was added into the test solution to reduce antimony to elementary substance. The antimony in solution was then separated and removed by filtration. Tin in solution was reduced to divalent with aluminum sheet. The content of tin in antimony-doped tin oxide powder sample was determined by iodometry using starch as the indicator. The proposed method was applied for the determination of tin in five representative antimony-doped tin oxide powder samples. The relative standard deviations (RSD, n=9) of results were between 0.14% and 0.22%,and the spiked recoveries were between 99.8% and 100.4%. Five samples above were also determined according to the experimental method in five laboratories. The statistical analysis of data obtained showed that the reproducibility limit (R) was in range of 0.36%-0.45%. High-purity tin dioxide powder and high-purity antimony trioxide were used to prepare simulated Sample 6# and Sample 7# with mass ratio of 85∶15 and 75∶25, respectively. The determination results by the proposed method were consistent with the theoretical values.