Recent advances in membrane introduction mass spectrometry (MIMS) are reviewed. On-line monitoring is treated by focusing on critical variables, including the nature and dimensions of the membrane, and the analyte vapor pressure, diffusivity, and solubility in the membrane barrier. Sample introduction by MIMS is applied in (i) on-line monitoring of chemical and biological reactors, (ii) analysis of volatile organic compounds in environmental matrices, including air, water and soil, and (iii) in more fundamental studies, such as measurements of thermochemical properties, reaction mechanisms, and kinetics. New semipermeable membranes are discussed, including those consisting of thin polymers, low vapor pressure liquids, and zeolites. These membranes have been used to monitor polar compounds, selectively differentiate compounds through affinity-binding, and provide isomer differentiation based on molecular size. Measurements at high spatial resolution, for example, using silicone-capped hypodermic needle inlets, are also covered, as is electrically driven sampling through microporous membranes. Other variations on the basic MIMS experiment include analyte preconcentration through cryotrapping (CT-MIMS) or trapping in the membrane (trap-and-release), as well as differential thermal release methods and reverse phase (i.e., organic solvent) MIMS. Method limitations center on semivolatile compounds and complex mixture analysis, and novel solutions are discussed. Semivolatile compounds have been monitored with thermally assisted desorption, ultrathin membranes and derivatization techniques. Taking advantage of the differences in time of membrane permeation, mixtures of structurally similar compounds have been differentiated by using sample modulation techniques and by temperature-programmed desorption from a membrane interface. Selective ionization techniques that increase instrument sensitivity towards polar compounds are also described, and comparisons are made with other direct sampling (nonchromatographic) methods that are useful in mixture analysis.

中文翻译：

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膜引入质谱：趋势和应用。

综述了膜引入质谱法（MIMS）的最新进展。通过重点关注关键变量来处理在线监测，这些关键变量包括膜的性质和尺寸以及分析物的蒸气压，扩散率和在膜屏障中的溶解度。MIMS引入的样品可用于（i）化学和生物反应器的在线监测，（ii）分析环境基质（包括空气，水和土壤）中的挥发性有机化合物，以及（iii）更基础的研究，例如测量热化学性质，反应机理和动力学。讨论了新的半透膜，包括由薄聚合物，低蒸气压液体和沸石组成的膜。这些膜已用于监测极性化合物，通过亲和结合选择性区分化合物，并根据分子大小提供异构体区分。还包括以高空间分辨率进行的测量，例如使用硅树脂封闭的皮下注射针头进样，以及通过微孔膜进行的电动采样。基本MIMS实验的其他变化包括通过冷阱（CT-MIMS）或膜中捕集（捕集和释放）进行分析物预富集，以及差热释放方法和反相（即有机溶剂）MIMS。方法的局限性集中在半挥发性化合物和复杂混合物的分析上，并讨论了新的解决方案。半挥发性化合物已通过热辅助解吸，超薄膜和衍生技术进行了监测。利用膜渗透时间的差异，已通过使用样品调制技术和通过温度编程从膜界面进行的脱附来区分结构相似的化合物的混合物。还描述了提高仪器对极性化合物灵敏度的选择性电离技术，并与可用于混合物分析的其他直接进样（非色谱）方法进行了比较。