Trace detection of non-uniformly distributed analytes on surfaces using mass transfer and large-area desorption electrospray ionization (DESI) mass spectrometry

Abstract

Ambient ionization methods such as desorption electrospray ionization (DESI) allow the analysis of chemicals adsorbed at surfaces without the need for sample (or surface) pretreatment. A limitation of current implementations of these ionization sources is the small size of the area that can be sampled. This makes examination of surfaces of large areas time-consuming because of the need to raster across the surface. This paper describes a DESI source that produces a spray plume with an effective desorption/ionization area of 3.6 cm(2), some 200 times larger than given by conventional DESI sources. Rhodamine 6G and several drugs of abuse (codeine, heroin and diazepam) were used to demonstrate the ability to use large-area DESI MS to perform rapid (a few seconds) representative sampling of areas of the order of several square centimetres without scanning the probe across the surface. The large area ion source displayed high sensitivity (limits of detection in the high nanogram range) and high reproducibility (approximately 20 to 35% relative standard deviation). The rapid analysis of even larger surfaces (hundreds of cm(2)) for traces of explosives is possible using a sorbent surface wipe followed by large-area DESI interrogation performed directly on the wipe material. The performance of this mass transfer dry wipe method was examined by determination of the limits of detection of several explosives. Surfaces with different topographies and compositions were also tested. Using this method, absolute limits of detection observed for HMX and RDX from plastic surfaces and skin were found to be as low as 10 ng cm(-2). The concentration of residue from large surface areas in this technique allowed the detection of 100 ng of explosives from surfaces with areas ranging from 1.00 x 10(3) cm(2) to 1.40 x 10(4) cm(2).

Non-contact halogen lamp heating assisted LTP ionization miniature rectilinear ion trap: a platform for rapid, on-site explosives analysis

“…To date, many ambient desorption/ionization (ADI) techniques have been developed for mass spectrometry for the detection of explosives since the appearance of desorption electrospray ionization (DESI), 21,26,27 the rst ADI source. A large group of these sources is based on electrical discharge, including owing atmospheric-pressure aerglow (FAPA), 28 direct analysis in real time (DART), 29,30 dielectric barrier discharge ionization (DBDI), 31 and low temperature plasma (LTP).…”

“…Swabbing the solid surface with swabs can rapidly collect the analytes from a large surface area, and it has been coupled to the large-area DESI mass spectrometer for analyzing explosives on large surface areas, demonstrating the high analysis speed as well as a high sensitivity. 26 Therefore, manual surface swabbing was adopted for the rapid analysis of explosives from large surface areas.…”

Wooden-tip electrospray ionization mass spectrometry for trace analysis of toxic and hazardous compounds in food samples

“…41 Diazepam is one of these sedatives and is commonly used to treat anxiety, panic attacks, insomnia etc., and can impair shortterm memory and increase feelings of sleepiness 42 and thus is used in sexual crimes. 44 The LOD (S/N ¼ 3) and RSD (n ¼ 6) for the detection of diazepam in a drink were found to be 30 ng mL À1 (absolute amount: 30.0 pg) and 8.7%, respectively. Then, the can of drink was poured out to simulate drinking.…”

Primary and secondary droplet and charge transmission characteristics of desorption electro-flow focusing ionization

“…Trace detection systems incorporate a range of techniques, including immunoassays, 1 Raman spectroscopy, 2 ion mobility spectrometry (IMS), 3,4 and the focus of this Letter, ambient pressure ionization mass spectrometry (API-MS). 5,6 Reviews summarizing ambient and desorption-based ionization techniques, 7,8 most notably, desorption electrospray ionization (DESI), 5,6,[9][10][11] can be found in the literature.…”

“…With the established transmitted current framework, electro-flow focusing for desorption ionization mass spectrometry demonstrated intense analyte signals and high signal-to-noise ratio for focusing gas pressures and jet/droplet charging potentials nearly an order of magnitude less than the traditional desorption electrospray ionization technique. 5,6,[9][10][11] Figure 1 schematically represents the geometry of the electro-Flow FocusingV R nebulizer (Ingeniatrics Tecnolog ıas, Sevilla, Spain) with a 150 lm capillary inner diameter, 100 lm capillary-to-orifice distance, and 100 lm exit orifice diameter. The electro-flow focusing ion source was developed around the "flow focusing" (FF) technique originally developed by Gañ an-Calvo.…”