液液萃取技术在低浓度乙醇水溶液样品检测前处理中的应用

采用液液萃取技术浓缩水中的低浓度乙醇后,用气相色谱法进行测定。首先优化以甲基叔丁基醚(MTBE)为萃取剂的萃取条件:初始乙醇溶液的质量分数win=1.032%、水相与有机相的体积比5∶1,萃取温度291.2 K,搅拌速度为200 r/min.在此基础上,分别加入固体无机盐和离子液体强化液液萃取过程,结果表明固体无机盐K2CO3的盐效应最为明显;随着盐浓度的增加,萃取后有机相中乙醇的质量分数wo也随之增大,从而实现对乙醇水溶液的显著浓缩作用。盐效应的分离机理进一步通过红外光谱分析和量子化学计算,从分子结构和分子间相互作用力方面进行解释,因而实验、理论分析和计算结果保持一致。该样品检测前处理方法具有重现性好、准确度高、快速、简便的特点,且无工业放大效应,为分析水中低浓度有机物提供参考价值。本文中将化工分离过程强化技术应用于样品检测前处理中,体现了化学工程与分析化学的跨学科结合。

Application of liquid-liquid extraction in sample pretreatment of aqueous solutions containing low-concentration ethanol

Low-concentration ethanol in aqueous solutions is firstly concentrated by liquid-liquid extraction technique and then is detected with gas chromatography(GC) method.The operating conditions affecting extraction process using MTBE as the separating agent,are investigated and optimized as follows:1.032% of initial aqueous ethanol concentration,5∶1 of phase volume ratio,291.2 K of extraction temperature,200 r/min of stirring speed.On this basis,the solid salts or ionic liquids are added to the mixture to intensify the conventional liquid-liquid extraction process.It is found that the salting effect of K2CO3 is the highest among all the salts investigated.As the salt concentration increasing,the ethanol concentration in the organic phase wo also increases.The separation mechanism of salting effect is explained from the molecular structure and interaction force by means of FT-IR spectrometry and quantum chemistry calculations.This sample pretreatment method is of good reproducibility,high accuracy,quickness and simplicity,and has no scale-up effect,providing reference values for determination of low concentration organic substances in aqueous solution.This work applies the separation process intensification techniques to sample pretreatment,and thus brings about the combination of interdisciplinary fields between chemical engineering and analytical chemistry.