Principle and Application of Ambient Mass Spectrometry for Direct Analysis of Complex Samples

Ambient mass spectrometry allows the in situ, real-time, online, high throughput, and low sample-consumption analysis to be performed with no/minimal sample pretreatment. Consequently, ambient mass spectrometry featured by direct ionization techniques is of increasing interest for the detection of trace analytes in complex matrix. The application of ambient mass spectrometry has greatly improved the efficiency of mass spectrometry method, and renders fast mass spectrometry analysis of practical samples possible. In this tutorial paper, the fundamental principles, operating modes, the instrumentation, and application of typical ambient ionization techniques have been reviewed, giving emphasis on the theoretical modes to illustrate the working mechanism of various ionization techniques. The important progresses in food analysis, pharmaceutical analysis, environmental analysis, in vivo analysis, metabolomics studies, proteomics studies, and ambient mass spectrometry imaging have been systematically discussed, showing a clear trend that the development of ambient mass spectrometry has been accelerated by the urgently practical need of detecting trace compounds in complex matrices with high analysis speed. The perspectives on the development and application of ambient mass spectrometry have been discussed in the present article.