A sandwich temperature control membrane inlet system based on a miniature mass spectrometer is presented that demonstrates improved analytical performance for the measurement of dissolved gases and volatile organic compounds (VOCs) in aqueous solution. Aqueous solution is directly brought to the monolayer flat membrane interface at a constant flow rate. A heating resistor and a thermocouple are fixed on the side of the membrane and aqueous solution respectively. This new strategy allows for a temperature compensation method, affording an improvement of sensitivity and a reduction of response time compared with the conventional heating solution temperature control strategy. Furthermore, a static heating mode is applied to effectively remove the memory effect. Automatic sampling and measurement are achieved by using the membrane inlet system with silicone sheeting of 50 μm thickness. The vacuum is below 3×10^-5 Torr, which can make the instrument work normally. A good linear response is observed for benzene in the range of 0.1 ppm to10 ppm and the detection limit is 50 ppb. The analytical capacity of this system is demonstrated by the on-line analysis of VOCs in aqueous solution, in which the dominant ions are detected rapidly. The results indicate that the sandwich temperature control membrane inlet mass spectrometer (STC-MIMS) has a potential application for on-line analyzing organic pollutions in aquatic environments.

提出了一种基于微型质谱仪的三明治式温度控制膜入口系统，该系统展示出改进的分析性能，可用于测量水溶液中的溶解气体和挥发性有机化合物（VOC）。将水溶液以恒定的流速直接引入单层平膜界面。加热电阻和热电偶分别固定在膜和水溶液的侧面。与传统的加热溶液温度控制策略相比，该新策略允许使用温度补偿方法，从而提高了灵敏度并缩短了响应时间。此外，采用静态加热模式可有效消除记忆效应。通过使用膜入口系统和厚度为50μm的硅胶片，可以实现自动采样和测量。真空度低于3×10^-5托，可以使仪器正常工作。苯在0.1 ppm至10 ppm范围内观察到良好的线性响应，检出限为50 ppb。该系统的分析能力通过在线分析水溶液中的VOC来证明，其中的主要离子可被快速检测到。结果表明，夹层温度控制膜入口质谱仪（STC-MIMS）在在线分析水生环境中的有机污染方面具有潜在的应用。