电位滴定法测定抛光液中的三酸含量

探讨了利用自动电位滴定仪对抛光液中磷酸、硫酸及硝酸的分析方法,以及对溶剂的标定方法。电位滴定法测定三酸,先用硫酸亚铁铵滴定硝酸,再用氢氧化钠滴定磷酸和硫酸,从而计算三酸含量。结果表明,与传统滴定法相比,电位滴定法标定硫酸亚铁铵的相对标准偏差(RSD)从1.1%降至0.13%,标定氢氧化钠的RSD从0.72%降至0.06%。电位滴定法测定自配样品及工厂抛光产品中的硝酸,回收率分别在96%及93%以上。电位滴定法测定自配样品及工厂抛光产品中磷酸和硫酸的回收率偏差在3%以内。手动滴定法测定磷酸和硫酸的回收率偏差在5%~10%,回收效果不如电位滴定法。电位滴定法测定工厂抛光液的三酸加标回收率偏差均小于3%。自动电位滴定法比手工滴定的准确性和精密度明显提高,弥补了手工滴定法只能分析磷酸和硫酸,而无法测定硝酸的缺陷。

Determination of Three-acids in Polishing Solution by Potentiometric Titration

Analytical methods of phosphoric acid, sulfuric acid and nitric acid in polishing solution, and methods of calibration of solvents by automatic potentiometric titrator were discussed. Nitric acid was titrated by ammonium ferrous sulfate, then phosphoric acid and sulfuric acid were titrated by sodium hydroxide, and the contents of three-acids were calculated. The results showed that the RSD value of ammonium ferrous sulfate calibrated by potentiometric titration is reduced from 1.08% to 0.13% and that of sodium hydroxide from 0.72% to 0.06% compared with traditional titration. The recovery rates of nitric acid in self-made samples and polishing products determined by potentiometric titration were 96% and 93% respectively. The recovery of phosphoric acid and sulfuric acid in self-made samples and polishing products by potentiometric titration was within 3%. The recovery of phosphoric acid and sulfuric acid by manual titration was 5-10% deviation, and the recovery effect was inferior to that by potentiometric titration. By potentiometric titration, the recovery deviation of the three acids in factory polishing liquid was less than 3%. The accuracy and precision of automatic potentiometric titration were much higher than that of manual titration. It makes up for the defect that manual titration could only analyze phosphoric acid and sulfuric acid, but could not determine nitric acid.