Deep‐ultraviolet laser ablation electrospray ionization mass spectrometry

Abstract

A 193-nm wavelength deep ultraviolet laser was used for ambient laser ablation electrospray ionization mass spectrometry of biological samples. A pulsed ArF excimer laser was used to ablate solid samples, and the resulting plume of the desorbed material merged with charged electrospray droplets to form ions that were detected with a quadrupole time-of-flight mass spectrometer. Solutions containing peptide and protein standards up to 66-kDa molecular weight were deposited on a metal target, dried, and analyzed. No fragmentation was observed from peptides and proteins as well as from the more easily fragmented vitamin B 12 molecule. The mass spectra contained peaks from multiply charged ions that were identical to conventional electrospray. Deep UV laser ablation of tissue allowed detection of lipids from untreated tissue. The mechanism of ionization is postulated to involve absorption of laser energy by a fraction of the analyte molecules that act as a sacrificial matrix or by residual water in the sample.

Direct Tissue Mass Spectrometry Imaging by Atmospheric Pressure UV-Laser Desorption Plasma Postionization

“…Due to the diffraction limit of IR wavelengths, the focused laser spot is commonly larger than that of UV light, and so for high-resolution studies, UV approaches are currently superior. Even though UV-LAESI − has also been reported, most UV-based ambient MSI studies are performed by AP-MALDI. AP-MALDI using UV lasers has been used to produce ion images at the μm scale. , In addition, when being coupled to a postionization method, for instance, a low-temperature plasma (LTP) source, detected ion intensities can be boosted significantly …”

Ambient ionization mass spectrometry applied to new psychoactive substance analysis

“…These employ ultraviolet (UV) or infrared (IR) laser sources to promote sample desorption in combination with ESI ionization. The main advantage of laser beams is that they can be optically focused, which enables highly efficient desorption at superior spatial resolution (10-50 μm) and pulse frequencies (few ns) than spray-and plasma-based techniques (Feider et al, 2019;Lawal et al, 2019). Some of the techniques used for analytical work are matrix-assisted laser desorption electrospray ionization (MALDESI), laser diode thermal desorption (LDTD), laser ablation electrospray ionization (LAESI), and electrospray-assisted laser desorption ionization (ELDI), mainly applied to molecular imaging and the analysis of proteins, lipids and metabolites in biological tissue matrices (Deimler et al, 2014;Peng et al, 2004Peng et al, , 2010Robichaud et al, 2014;Shrestha et al, 2010).…”

Laser Desorption/Ablation Postionization Mass Spectrometry: Recent Progress in Bioanalytical Applications

“…Other cases using UV lasers include laser desorption atmospheric pressure chemical ionization (LD‐APCI) (Turney & Harrison, 2006), LA‐FAPA (Shelley, Ray, & Hieftje, 2008), plasma‐assisted (multiwavelength) laser desorption ionization (PA(M)LDI) (Zhang et al, 2012a,b), laser ablation‐liquid vortex capture electrospray ionization (LA‐LVC/ESI) (Ovchinnikova et al, 2014), laser microdissection‐liquid vortex capture electrospray ionization (LMD‐LVC/ESI) (Cahill, Kertesz, & Van Berkel, 2015), laser desorption/ionization droplet delivery mass spectrometry (LDIDD‐MS) (Lee et al, 2016), and laser ablation direct analysis in real‐time (LADI) (Fowble et al, 2017). The use of a laser in the deep UV region has been reported recently for ablation of proteins and lipids from untreated tissue (Lawal, Donnarumma, & Murray, 2019). During the laser ablation process, proteins and lipids absorbed the 193 nm laser energy due to the π – π * electronic transition and might be ejected via a sacrificial matrix mechanism similar to IR ablation (Little, Laboy, & Murray, 2007).…”

“…The improved beam quality also made this methodology an ideal tool for mapping endogenous and exogenous compounds from zebra plant leaves and mouse kidneys with a ~30 μm vertical resolution and a ~100 μm lateral resolution. Deep‐UV LAESI, using a pulsed ns 193 nm laser, enabled detection of intact peptides and proteins with no fragments (Lawal, Donnarumma, & Murray, 2019). Heat‐assisted LAESI, which employs a heated nitrogen spray to intercept the electrospray, has been reported to extend the capabilities of conventional LAESI to low polar compounds (Vaikkinen et al, 2013).…”