Ellis-Gibbings, L; Steven, R T; Dexter, A J; Bunch, J (2025) Effects of Inlet Capillary Temperature in Atmospheric-Pressure Infrared Laser-Ablation Plasma Postionization Mass Spectrometry. Journal of the American Society for Mass Spectrometry, 36 (12). pp. 2633-2646. ISSN 1044-0305

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Abstract

Mass spectrometry imaging (MSI) can be used to survey small and large molecules from a wide variety of surfaces including biological tissue sections. Atmospheric-pressure (AP) infrared laser-ablation plasma post-ionization (IR-PPI) has recently been shown to allow sample preparation free analysis of small molecules from both fresh frozen and formalin fixed paraffin embedded (FFPE) tissue. Detected ion intensities in IR-PPI as well as other AP inlet modalities such as desorption electrospray ionization (DESI) show a strong dependance on the inlet capillary temperature. In this study the relationship between detected ion intensity and inlet capillary temperature is evaluated, between room temperature and 650 °C, for analyte pipetted on various substrates, as well as fresh frozen and FFPE tissue, by IR-PPI. Temperature trends for exemplar ions of interest show a variety of dependencies with optimal temperatures observed throughout this temperature range. For example, detection of lactate [M-H]- m/z 89.0244 is optimal at ~100 °C, glutamine [M-H]- m/z 145.0618 at ~250 °C, arachidonic acid [M-H]- m/z 303.2324 at ~150 °C and PI(18:0/20:4) [M-H]- m/z 885.5488 at ~500 °C. Data reduction and clustering of these data by UMAP and k-means providing a summary of all temperature trends within the data and association of different ions with these trends are presented. Finally, the implications of different inlet capillary temperature settings in tissue MSI are demonstrated, by comparing detected glucose and lactate ion intensities in response to different inlet temperatures in mouse brain. The choice and control of inlet temperature is shown to be a critical variable for the interpretation of biological MSI data in AP modalities.

Item Type:	Article
Keywords:	Mass Spectrometry Imaging Ambient IR laser Plasma Ionisation Biological Development Sample Analysis IR-PPI-MALDI Nice-MSI chemical biology lactate glucose
Subjects:	Biotechnology > Bio-Diagnostics
Divisions:	Chemical & Biological Sciences
Identification number/DOI:	10.1021/jasms.5c00243
Last Modified:	16 Sep 2026 14:46
URI:	https://eprintspublications.npl.co.uk/id/eprint/10534