Laser Ablation Electrospray Imaging-Mass Spectrometry Imaging: Highlights From ASMS 2018

The long list of acronyms for mass spectrometry got longer with LAESI-MSI—laser ablation electrospray imaging–mass spectrometry imaging. This technique involves aiming an electrospray source horizontally over the top of the sample. The ESI ions are aimed at the MS inlet on the other side of the sample area. A laser beam is located perpendicularly above the sample. Short laser pulses are directed repeatedly at the same region of the sample. Each succeeding pulse ablates a deeper hole into the sample. The removed material is ejected from the hole and reacts with the ions from the ESI source. The reaction products are electrostatically attracted to the MS inlet.

A poster from Gemperline et al. described repeated pulses of LAESI-MS to study the penetration of fungicides in plant leaves in the z direction as part of a formulation study (“Analysis of Fungicides on Plant Leaves With LAESI-Mass Spectrometry Imaging [MSI] and LC-MS,” Poster WP 371, ASMS 2018). Candidate adjuvants were compared for the ability to improve penetration of the fungicide in grape and cucumber leaves. Sample prep was simple: 5 µL of the formulation was spotted on the leaf and dried for 30 minutes before LAESI-MS. Another study compared the effect of washing green peppers on removal of the fungicide from the skin and green pepper extract.

Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected]

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