Desorption electro-flow focusing ionization of explosives and narcotics for ambient pressure mass spectrometry

Abstract

Desorption electro-flow focusing ionization (DEFFI), a desorption-based ambient ion source, was developed, characterized, and evaluated as a possible source for field deployable ambient pressure mass spectrometry (APMS). DEFFI, based on an electro-flow focusing system, provides a unique configuration for the generation of highly charged energetic droplets for sample analysis and ionization. A concentrically flowing carrier gas focuses the liquid emanating from a capillary through a small orifice, generating a steady fluid jet. An electric field is applied across this jet formation region, producing high velocity charged droplets that impinge on an analyte laden surface. This configuration separates the jet charging region from the external environment, eliminating detrimental effects from droplet space charge or target surface charging. The sample desorption and ionization processes operate similar to desorption electrospray ionization (DESI). DEFFI demonstrated strong signal intensities and improved signal-to-noise ratios in both positive and negative mode mass spectrometry for narcotics, i.e., cocaine, and explosives, i.e., cyclotrimethylenetrinitramine (RDX), respectively. A characterization of DEFFI ionization mechanisms identified operation regimes of both electrospray and corona discharge based analyte ionization, as well as limitations in overall signal. In addition, the DEFFI response was directly compared to DESI-MS under similar operating conditions. This comparison established a wider and more stable optimal operating range, while requiring an order of magnitude lower applied gas pressure and applied potential for DEFFI than DESI. These reductions are due to the physical mode of jet formation and geometric configuration differences between DEFFI and DESI, pointing to a potential benefit of DEFFI-MS for field implementation.

In-source collision induced dissociation of inorganic explosives for mass spectrometric signature detection and chemical imaging

“…[20,39]. Briefly, experiments included the following system parameters: 138 kPa curtain gas (N 2 ), 83 kPa ion source gas 1 (N 2 ), 0.0 kPa ion source gas 2 (N 2 ), 100 °C interface temperature, ± 10 V entrance potential, and 1.1 × 10 -3 kPa to 1.3 × 10 -3 kPa operating vacuum.…”

“…These explosives have been detected using a range of analytical techniques, including ion chromatography (IC) [1,2], capillary electrophoresis (CE) [3,4], high performance liquid chromatography (HPLC) [5], and most notably, ion mobility spectrometry (IMS) [6][7][8][9][10][11][12][13] and mass spectrometry (MS) [14][15][16][17][18][19][20][21][22]. The rapid analysis times and cost effectiveness of these field compatible instruments have led to widespread deployment of ion mobility spectrometry.…”

Trace detection and competitive ionization of erythritol tetranitrate in mixtures using direct analysis in real time mass spectrometry

“…Alternative detection schemes such as gas chromatography mass spectrometry (GC/MS) 4,5 or liquid chromatography (LC/MS) 6,7 are hindered by lengthy analysis times. Trace detection of a range of explosive compounds directly from paper, metals, plastics, and human skin has been demonstrated with DESI-MS. [11][12][13] DESI and other liquid dropletbased ambient ionization sources 14 ionize explosive compounds through the traditional mechanisms studied for electrospray ionization (ESI), 15,16 forming adducts with available nitrite (NO 2 À ), nitrate (NO 3 À ), or reactive species added to the spray solvent (Cl À ). 10 These desorption-based ambient ionization methods enable the direct analysis of analytes from a variety of surfaces with no or minimal sample preparation.…”

Rapid detection and isotopic measurement of discrete inorganic samples using acoustically actuated droplet ejection and extractive electrospray ionization mass spectrometry

“…The extractive electrospray ionization (EESI) component of the investigated system comprised an electro‐flow focusing ionization source (Ingeniatrics Tecnologías, Sevilla, Spain). The electro‐flow focusing (EFF) source has been investigated and characterized in‐depth as a desorption‐style ionization technique for ambient mass spectrometry detection and imaging . The EFF source employs a recessed capillary (150 µm i.d.)…”