Direct, trace level detection of explosives on ambient surfaces by desorption electrospray ionization mass spectrometry

Abstract

Desorption electrospray ionization (DESI) mass spectrometry is used to detect trace amounts of explosives present on a variety of ambient surfaces in 5-second analysis times without any sample preparation.

Internal energy distributions in desorption electrospray ionization (DESI)

“…Analytes present at the surface are extracted and carried by the offspring droplets into the atmospheric pressure interface of the mass spectrometer (MS). Since its introduction in 2004 [1], DESI has found numerous areas of application, including forensics [2][3][4][5][6][7][8], imaging [2, 3, 9 -11], metabolomics [12][13][14][15], pharmaceutics [8, 14, 16 -25], characterization of natural products [1,8,19], bacteria [26], polymers [27,28], proteins [1, 24, 29 -32], and explosives detection [4,8,[33][34][35][36][37]. Investigations into the fundamentals of the droplet dynamics and ionization mechanism have also been conducted through systematic measurements of the droplet size and velocity [38], computer simulations [39], surface charging effects [40], or more simply, by evaluating the mass spectra of various types of analytes in conjunction with variations in the experimental parameters [41].…”

“…These observations are consistent with the mechanism noted above and they also enable the user to exercise control over the energetics of the DESI ionization process, through manipulation of external and internal ion source parameters. [1, 24, 29 -32], and explosives detection [4,8,[33][34][35][36][37]. Investigations into the fundamentals of the droplet dynamics and ionization mechanism have also been conducted through systematic measurements of the droplet size and velocity [38], computer simulations [39], surface charging effects [40], or more simply, by evaluating the mass spectra of various types of analytes in conjunction with variations in the experimental parameters [41].…”

Charge assisted laser desorption/ionization mass spectrometry of droplets

“…With such shortcomings, the ionization step may be considered the weakest link and the bottleneck in mass spectrometry at its current stage. Therefore, more vigorous research has been devoted to the study of ion generation in recent years, resulting in several new ionization techniques such as desorption electrospray ionization (DESI) [3], atmospheric pressure photoionization (APPI) [4], laser desorption atmospheric pressure chemical ionization (LD-APCI) [5][6][7], electrospray assisted laser desorption ionization (ELDI) [8,9], laser ablation electrospray ionization (LAESI) [10], no-discharge APCI [11,12], direct analysis in real time (DART) [13], desorption atmospheric pressure chemical ionization (DAPCI) [14], laser induced acoustic desorption (LIAD) [15,16], field-induced droplet ionization (FIDI) [17], and nanostructure-initiator ionization [18]. Among the techniques cited, APPI, ELDI, LAESI, LD-APCI, and LIAD are similar in the sense that they utilize a two-step approach in which desorption and ionization occur during two separate physical processes.…”

Orbitrap mass spectrometry: Instrumentation, ion motion and applications

“…Ambient ionization methods such as DESI (Takats et al, 2004), direct analysis in real time (DART) (Cody, Laramee, & Durst, 2005), desorption atmospheric pressure chemical ionization (DAPCI) (Takats et al, 2005), electrospray-assisted laser desorption ionization (ELDI) (Shiea et al, 2005), matrix-assisted laser desorption electrospray ionization (MALDESI) (Sampson, Hawkridge, & Muddiman, 2006) and atmospheric solids analysis probe (ASAP) (McEwen, McKay, & Larsen, 2005) remove the requirement for sample preparation and allow direct analysis of unmodified samples in the ambient environment. Since untreated samples can be very complex, the ability to couple these methods to high performance mass analyzers is essential for accurate elucidation of their chemical composition.…”