Matrix Optical Absorption in UV-MALDI MS

  • Kenneth N. Robinson
  • Rory T. Steven
  • Josephine Bunch
Research Article


In ultraviolet matrix-assisted laser desorption/ionization mass spectrometry (UV-MALDI MS) matrix compound optical absorption governs the uptake of laser energy, which in turn has a strong influence on experimental results. Despite this, quantitative absorption measurements are lacking for most matrix compounds. Furthermore, despite the use of UV-MALDI MS to detect a vast range of compounds, investigations into the effects of laser energy have been primarily restricted to single classes of analytes. We report the absolute solid state absorption spectra of the matrix compounds α-cyano-4-hydroxycinnamic acid (CHCA), para-nitroaniline (PNA), 2-mercaptobenzothiazole (MBT), 2,5-dihydroxybenzoic acid (2,5-DHB), and 2,4,6-trihydroxyacetophenone (THAP). The desorption/ionization characteristics of these matrix compounds with respect to laser fluence was investigated using mixed systems of matrix with either angiotensin II, PC(34:1) lipid standard, or haloperidol, acting as representatives for typical classes of analyte encountered in UV-MALDI MS. The first absolute solid phase spectra for PNA, MBT, and THAP are reported; additionally, inconsistencies between previously published spectra for CHCA are resolved. In light of these findings, suggestions are made for experimental optimization with regards to matrix and laser wavelength selection. The relationship between matrix optical cross-section and wavelength-dependant threshold fluence, fluence of maximum ion yield, and R, a new descriptor for the change in ion intensity with fluence, are described. A matrix cross-section of 1.3 × 10–17 cm–2 was identified as a potential minimum for desorption/ionization of analytes.

Graphical Abstract


UV-MALDI MALDI Matrix Wavelength Absorption Fluence 



The authors thank Stuart Davidson (NPL) for performing the density measurements, and the rest of the NiCE-MSI team, in particular Spencer Thomas, Alan Race, Adam Taylor, and Alex Dexter, as well as David Barratt (University of Nottingham) for helpful discussions and feedback on the manuscript. Funding for the work presented here was provided through the AIMS HIGHER project as part of the NPL strategic research program.

Supplementary material

13361_2017_1843_MOESM1_ESM.docx (835 kb)
ESM 1 (DOCX 835 kb)


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Copyright information

© Crown 2017

Authors and Affiliations

  • Kenneth N. Robinson
    • 1
    • 2
  • Rory T. Steven
    • 1
  • Josephine Bunch
    • 1
    • 3
  1. 1.National Center of Excellence in Mass Spectrometry Imaging (NiCE-MSI)National Physical LaboratoryTeddingtonUK
  2. 2.Advanced Materials and Healthcare Technologies DivisionUniversity of NottinghamNottinghamUK
  3. 3.Department of Surgery and Cancer, Faculty of MedicineImperial College LondonLondonUK

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