Direct Analyte Probe Nano-extraction Coupled to NSI Mass Spectrometry
Direct analyte-probed nanoextraction (DAPNe) is a recently developed technology that is typically coupled with nanospray ionization-mass spectrometry (NSI-MS). DAPNe uses a four-positioner nanomanipulator mounted to a stage of a microscope to probe surfaces of interest for trace illicit analytes. Key advantages of this technique lies in reduced matrix effects, non-destructive nature, and fine spatial resolution (up to 5 nm). The limits of detection using this surface-probing technique has shown as low as 7 picograms and 300 attograms for histidine and caffeine, respectively.
DAPNe-NSI-MS has proven to be effective for extraction of trace analytes from fibers, electrostatic lifts, post-blast explosive residues, and from within latent fingerprints. This technique facilitates the extraction of potentially illicit chemistry using a metal-coated capillary tip with a 1 um i.d. filled with an appropriate solvent. The capillary tip is landed onto a particle of interest and the solvent is injected; after solvation of the particle, the solution is aspirated back into the capillary. This is then analyzed via NSI-MS for characterization of the trace substances on the surface in question. DAPNe-NSI-MS has proven to be an exceptional non-destructive approach in the identification of illicit drugs and explosives in ultratrace quantities.