Automatic z-Axis Correction for IR-MALDESI Mass Spectrometry Imaging of Uneven Surfaces

Two-dimensional mass spectrometry imaging (2D MSI) experimentsmainly involve samples with a flat surface and constant thickness,but some samples are challenging to section due to the texture andtopography. Herein, we present an MSI method that automatically correctsfor discernible height differences across surfaces during imagingexperiments. A chromatic confocal sensor was incorporated into theinfrared matrix-assisted laser desorption electrospray ionization(IR-MALDESI) system to measure the sample surface height at the locationof each analytical scan. The height profile is subsequently used foradjusting the z-axis position of the sample duringMSI data acquisition. We evaluated this method using a tilted mouseliver section and an unsectioned Prilosec tablet due to their exteriorquasi-homogeneity and height differences of approximately similar to 250 mu m. MSI with automatic z-axis correction showedconsistent ablated spot sizes and shapes, revealing the measured ionspatial distribution across a mouse liver section and a Prilosec tablet.Conversely, irregular spots and reduced signals with large variabilitywere observed when no z-axis correction was applied.

Automated summary

This study presents a mass spectrometry imaging (MSI) method that automatically corrects discernible height differences across surfaces during imaging experiments. A chromatic confocal sensor is incorporated into the infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) system to measure the sample surface height at each analytical scan location, allowing for adjustment of the z-axis position of the sample during MSI data acquisition. The method is evaluated using a tilted mouse liver section and an unsectioned Prilosec tablet, showing consistent ablated spot sizes and shapes and revealing the measured ion spatial distribution.