Apparently, these instruments are not suitable for in situ analysis, which limits the application of ambient mass spectrometry in many important fields such as chemical industry, process monitoring, drug discovery, and pharmaceutical screening. On the other hand, simple mass spectrometers have been constructed for onsite analysis [18–20]. More recently, miniature mass spectrometers installed with ambient ionization sources such as DESI [21, 22] and LTP  have been reported, showing increasing interest to develop inexpensive mass spectrometers with high analytical throughput for in situ applications.