MALDI-TOF imaging mass spectrometry of artifacts in “dried droplet” polymer samples

Abstract

Matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) imaging of polystyrenes with various molecular masses was applied to study spatial molecular mass distribution of polymers in sample spots prepared by the "dried droplet" method. When different solvents and target surfaces were examined, a segregation of single homologous polymers was observed depending upon the evaporation rate of the solvent. For the observed patterns left by the evaporating droplet, a hypothesis is offered taking into account different hydrodynamic interactions and diffusion. The results illustrate that spot preparation using the conventionally "dried droplet" method is prone to artifacts and should be avoided for reliable and reproducible MALDI mass spectrometry experiments with regards to the determination of molecular masses and mass distributions.

Quantitative Analysis of Polymer Additives with MALDI-TOF MS Using an Internal Standard Approach

“…Quantitative applications of MALDI are also very limited and it is well known that in conventional solvent-based dried droplet sample preparation, the sample and matrix are not uniformly distributed over a spot [15]. This effect is based on the affinity of the dissolved sample to stay in the solvent and the variability in drying.…”

Reducing Spatial Heterogeneity of MALDI Samples with Marangoni Flows During Sample Preparation

“…Notably, Marangoni flows induced by the temperature gradient serve as an effective means to compete with other natural driving forces influencing the internal flow of analytes. Other driving forces include analyte adsorption [40], surfactant contamination [27], inadvertent solvent evaporation [41], and physicochemical properties of matrixes [28]. However, the reduction of heterogeneity with Marangoni flows for some matrixes are less efficient.…”

Detailed MALDI comparison of NiPAm glycopolymers

“…Although valuable information such as the polydispersity index (PDI), molar masses (M n and M w ), sequences and end groups can be determined, MALDI-TOF MS involves numerous steps to finally obtain a spectrum. Over the years the sample preparation has developed and the most common techniques are the dried droplet method [10][11][12][13], layering method [10] as well as spraying methods. The dried droplet is the simplest, fastest and mostly applied method for routine measurements.…”