离子液体的阴离子三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根的离子对色谱-直接电导检测法分析

建立了同时测定离子液体的阴离子三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根的反相离子对色谱-直接电导检测方法。采用Diamonsil C18分离柱,以离子对试剂-苹果酸-乙腈水溶液为流动相,从流动相组成和色谱柱温度两方面讨论并确定了优化的色谱条件,即以0.15 mmol/L氢氧化四丁铵-0.099 mmol/L苹果酸-20%(v/v)乙腈混合水溶液(pH 6.5)为流动相,柱温25 ℃。在此条件下,三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子均达到基线分离,且不受其他常见阴离子氟离子、氯离子、溴离子、硝酸根、硫酸根的干扰。三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子的检出限(信噪比为3)分别为0.21、0.07、0.36、0.12 mg/L。将方法应用于测定离子液体中三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子,加标回收率为95.0%～104.6%。该法简便、快速、灵敏度较高,可满足离子液体样品的检测要求。

Determination of ionic liquid anions of trifluoroacetate, thiocyanate,tetrafluoroborate and trifluoromethanesulfonate by ion-pair chromatography with direct conductivity detection

An ion-pair chromatographic method with direct conductivity detection was established on a reversed-phase silica-based column for the simultaneous determination of ionic liquid anions of trifluoroacetate,thiocyanate,tetrafluoroborate and trifluoromethanesulfonate.The analytes were separated using a mobile phase of ion pair reagent-malic acid-acetonitrile on the Diamonsil C18 column.The effects of mobile phase composition and column temperature on the retention of the anions were investigated.The optimized chromatographic conditions were as follows: 0.15 mmol/L tetrabutylammonium hydroxide-0.099 mmol/L malic acid-20%(v/v) acetonitrile aqueous solution(pH 6.5) as mobile phase,a column temperature of 25 ℃.Under the optimal conditions,the baseline separation of trifluoroacetate,thiocyanate,tetrafluoroborate and trifluoromethanesulfonate was achieved without any interference by other ordinary anions(fluoride,chloride,bromide,nitrate,sulfate).The detection limits(S/N=3) were 0.21,0.07,0.36 and 0.12 mg/L for trifluoroacetate,thiocyanate,tetrafluoroborate and trifluoromethanesulfonate,respectively.The method has been applied to the determination of the four anions in ionic liquids.The spiked recoveries of the anions were from 95.0% to 104.6%.The results demonstrate that the convenience,rapidity,sensitivity and accuracy are fit for the requirements of quantitative analysis of trifluoroacetate,thiocyanate,tetrafluoroborate and trifluoromethanesulfonate in ionic liquids.