Abstract:

The semi-volatile organic compounds(SVOCs) in air can be enriched by ionic liquids. However, during the study of air sample tubes, fog and black phenomenon often appeared in the sample tubes. At the same time, analysis process was disturbed by high background values and impurity peak. To investigate the reasons above, 1-methyl acetate-3-methyl imidazolium bis(trifluoromethanesulfonyl) imides was used to improve the air-sample tubes and a series of experiments were designed. And on the basis of the ionic liquid sample tubes reuse, the sorbent tubes were desorbed at 220℃ and 50 ml He·min^-1 for 15 min. The vapors from the primary desorption were collected at 0℃ in the cold trap without sorbent. The cold trap was flash heated to 280℃ at 40℃·s^-1 (temperature of 250℃ for the valve, no inlet split or outlet split) and the vapors were transferred via the heated transfer line (250℃) to the GC. The GC temperature program was 100℃ (held for 1 min) then increased at 10℃·min^-1 to 200℃ and finally increased at 5℃·min^-1 to 250℃ (held for 4 min). When the mesh of stainless steel substituted for glass fiber, the data indicates the mesh gives the better result.

Key words: ionic liquid, air sample tube, ATD-GC-MS, orthogonal test

摘要：

离子液体能够富集空气中的半挥发性有机污染物。然而, 在采样管的研制过程中, 离子液体空气采样管出现了白雾和变黑的现象, 同时出现本底高、杂质多的现象, 严重妨碍了采样管的实际应用。为了弄清楚这些现象产生的原因, 实验采用自合成的1-乙酸甲酯基-3-甲基咪唑双三氟甲烷黄酰亚铵盐[CH₂COOCH₃MIM][NTF₂], 制成改进的空气采样管, 进行了一系列的研究。在保证离子液体采样管重复利用的基础上, 通过设计正交实验优化了二级脱附的条件:二阶段脱附模式, 脱附气体为氦气;第一阶段样品管脱附, 脱附温度220℃, 脱附时间15 min, 脱附流速50 ml·min^-1;冷阱捕集温度0℃, 第二阶段冷阱脱附, 脱附温度280℃, 脱附时间10 min, 升温速率40℃·s^-1, 阱前阱后均无分流;六通阀温度250℃, 传输线温度250℃;气相色谱质谱的条件为:初始温度为100℃保持1 min, 以10℃·min^-1的速率升至200℃, 再以5℃·min^-1的速率升至250℃, 保持4 min。并采用不锈钢网替代玻璃棉, 取得了很好的实际效果。

关键词: 离子液体, 空气采样管, 自动热脱附-气质联用, 正交实验