碘单质对含碘制剂中酸含量滴定影响的研究

摘要

目的:研究碘单质(I2)对含碘制剂中酸含量滴定的影响,并建立消除I2影响的方法以准确测定其中总酸含量.方法:以甲癣涂剂为例,滴定分析前用硫化钠(Na2S)还原制剂中的I2,并与传统滴定方法进行对比.根据两种方法所消耗的氢氧化钠滴定液体积的不同,探讨I2对含碘制剂中总酸含量滴定的影响.结果:采用Na2S还原法可消除I2的影响,指示剂变色敏锐,测定的总酸含量与理论值相同.甲癣涂剂的总酸检测摩尔浓度线性范围为3.926~7.290 mol/ml(r=0.9999);精密度、稳定性、重复性试验的RSD<0.04%;总酸回收率为99.91%~100.10%,RSD=0.036%(n=9).结论:I2对含碘制剂中酸含量滴定结果有影响,I2在滴定过程中发生歧化反应生成碘化氢可干扰滴定结果,同时生成的次碘酸还可氧化指示剂,使得滴定终点不敏锐甚至不变色.利用Na2S还原制剂中的I2可消除其对制剂酸含量滴定结果的影响,提高测定含碘制剂中酸含量方法的精密度和重复性,并使测定结果准确、可靠.%OBJECTIVE:To study on the effect of iodine (I2) on the acid content titration in the preparations,and establish a method of eliminating I2 for accurate determination of total acid content. METHODS:Taking an example of Onychomycosis paint,I2 was reduced by sodium sulfide(Na2S)before titration analysis and compared with the standard method of traditional titration. Ac-cording to the two methods of consumption of different sodium hydrate(NaOH)volume,the effect of I2 on the determination of to-tal acid content in preparation was explored. RESULTS:Reduction method of Na2S can eliminate the effect of I2,the color of indica-tor changed acutely. The determined total acid and theoretical values were the same;the linear range of the concentration of total ac-id in onychomycosis paint was 3.926-7.290 mol/ml(r=0.9999);RSDs of precision,stability and reproducibility tests were no more than 0.04%;average recovery was 99.91%-100.10%(RSD=0.036%,n=6). CONCLUSIONS:I2 has effect on the determina-tion of total acid content,the disproportion reaction of I2 can generate hydriodic acid that can interfere acid-base titration's results, and the generated hydriodic acid can oxidize indicator to make the end point is not sensitive or even invariant color. Using Na2S can eliminate the effect of iodine on the preparation of acid titration,which has improved precision and reproducibility with accurate and reliable determination results.