Overcoming selectivity and sensitivity issues of direct inject electrospray mass spectrometry via DAPNe-NSI-MS.

Direct inject electrospray mass spectrometry offers minimal sample preparation and a "shotgun" approach to analyzing samples. However, complex matrix effects often make direct inject an undesirable sample introduction technique, particularly for trace level analytes. Highlighted here is our solution to the pitfalls of direct inject mass spectrometry and other ambient ionization methods with a focus on trace explosives. Direct analyte-probed nanoextraction coupled to nanospray ionization mass spectrometry solves selectivity issues and reduces matrix effects while maintaining minimal sample preparation requirements. With appropriate solvent conditions, most explosive residues can be analyzed with this technique regardless of the nature of the substance (i.e., nitroaromatic, oxidizing salt, or peroxide).