title: Independent assessment of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sample preparation quality: Effect of sample preparation on MALDI-MS of synthetic polymers.
abstract: BACKGROUND
  Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) provides detailed and in-depth information about the molecular characteristics of synthetic polymers. To obtain the most accurate results the sample preparation parameters should be chosen to suit the sample and the aim of the experiment. Because the underlying principles of MALDI are still not fully known, a priori determination of optimal sample preparation protocols is often not possible.
  
  
  METHODS
  Employing an automated sample preparation quality assessment method recently presented by us we quantified the sample preparation quality obtained using various sample preparation protocols. Six conventional matrices with and without added potassium as a cationization agent and six ionic liquid matrices (ILMs) were assessed using poly(ethylene glycol) (PEG), polytetrahydrofuran (PTHF) and poly(methyl methacrylate) (PMMA) as samples. All sample preparation protocols were scored and ranked based on predefined quality parameters and spot-to-spot repeatability.
  
  
  RESULTS
  Clearly distinctive preferences were observed in matrix identity and cationization agent for PEG, PTHF and PMMA, as the addition of an excess of potassium cationization agent results in an increased score for PMMA and a contrasting matrix-dependent effect for PTHF and PEG. The addition of excess cationization agent to sample mixtures dissipates any overrepresentation of high molecular weight polymer species. Our results show reduced ionization efficiency and similar sample deposit homogeneity for all tested ILMs, compared with well-performing conventional MALDI matrices.
  
  
  CONCLUSIONS
  The results published here represent a start in the unsupervised quantification of sample preparation quality for MALDI samples. This method can select the best sample preparation parameters for any synthetic polymer sample and the results can be used to formulate hypotheses on MALDI principles. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: DSM Resolve, Urmonderbaan 22, 6167 RD, Geleen, The Netherlands.|Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands.|M4I Institute, Maastricht University, Universiteitssingel 50, 6229 ER, Maastricht, The Netherlands.
authors.forename: Pieter C
authors.identifier: http://orcid.org/0000-0001-8868-3616
authors.initials: PC
authors.lastname: Kooijman
authors.affiliation: DSM Resolve, Urmonderbaan 22, 6167 RD, Geleen, The Netherlands.
authors.forename: Sander
authors.initials: S
authors.lastname: Kok
authors.affiliation: DSM Resolve, Urmonderbaan 22, 6167 RD, Geleen, The Netherlands.|Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands.
authors.forename: Maarten
authors.initials: M
authors.lastname: Honing