Liquid Extraction Probes
Liquid Microjunction Surface Sampling Probing (LMJ-SSP) is an extractive atmospheric method for probing a variety of molecules off of surfaces. The technique is rooted in both electrochemistry, where scanning capillary microscopy was used for determining electrochemical activity, as well as microfluidics, where a similar device was used for coupling microdevices and SPE cards with mass spectrometry.
The original LMJ-SSPs are self-aspirating systems that pump liquid to a surface via a probe consisting of a Tee within which are 2 coaxial tubes, the internal of which is connected to a mass spectrometer. The pumped and aspirated flows are normally balanced so the probe can move away from the surface and nothing flows out of the sampling side. This end will form a liquid junction when it approaches a surface so that any compound that will dissolve in the solvent being used will be aspirated into the ionization source and a pneumatically assisted electrospray.
Liquid Extraction Surface Analysis
Liquid extraction based techniques based on this idea have broadened to syringe-like systems where instead of continuously flowing solvent to a surface, solvent can be deposited, allowed time to interact (or react), and aspirated for electrospraying.
This technique has been predominantly pursued here as a probe for TLC plates, a method for drug and metabolite detection from tissue dissections, and many other applications. The incorporation of the syringe-like probe in commercially available products, specifically as the LESA mode in the Advion Nanomate, will likely lead to more wide-spread adoption of the technique.