In a proof-of-concept experiment, two different matrix application methods, a spray method and a solvent-free sublimation method, were applied to the device and analyzed with MALDI.
Irrespective of the matrix application method, a certain level of experience and practice is needed in order to obtain suitable results.
Herein, we present a detailed optimization process for three different matrix application techniques with a focus on studying endogenous small molecules.
Previous publications reported on comparison and optimization of one matrix application method for a variety of matrices, comparison between dry coating and spray matrix application methods, or comparison between two different spray methods.
The matrix application technique plays a crucial role in the quality of mass spectral images, especially when obtaining high spatial resolution images.
Figure 2 compares MS profiling spectra for pure matrix using the airbrush (blue), optimized automatic sprayer (red), and optimized sublimation (green) matrix application methods for (a) DHB and (b) CHCA.
A simple way of matrix application is spraying of a concentrated matrix solution by means of a thin-layer chromatography (TLC) sprayer (Stoeckli et al. 2007b).
Using an automatic sprayer system, the matrix density and crystal size can be much more uniform, making the experimental results more reproducible; however, this method is more time-consuming than matrix application performed with an airbrush.
Other major changes included a modification of the matrix application methods by construction of a spraying device that allowed for improved control of the matrix deposition on tissue.
Figure 1 shows optical images comparing matrix coverage and crystal size for the airbrush, optimized automatic sprayer, and optimized sublimation matrix application methods respectively for (a) DHB and (b) CHCA.
