Imaging mass spectrometry MALDI matrix application

The preparation of samples for mass spectrometric analysis almost always requires recovery of the analyte from a matrix, often followed by further preparative steps prior to introduction of the sample into the ion source. Such destructive processes are unacceptable when the objective is to determine the specific location of a particular compound within a biological sample, e.g., the location of a certain lipid in a tissue, and led to the development of imaging mass spectrometry with MALDI as the ionization method, although DESI is also applicable. 

In Chapter 4, titled Principles of Mass Spectrometry Imaging Applicable to Thin-Layer Chromatography, the authors first introduce a budding analytical approach known as imaging mass spectrometry (IMS) strategy and then present some successful examples of its practical applications. Then, they introduce in detail three mass spectrometric techniques as those routinely used within the framework of IMS. These are secondary mass spectrometry (SIMS), matrix-assisted laser desorption/ ionization (MALDI-IMS), and desorption electrospray ionization (DESI). Finally, the authors discuss the advances and bottlenecks of these techniques when applied to TLC. 

Yang, M., James, A., Covey, T., and Kovarik, P. (2005). High-speed automated deposition of matrix onto tissue samples for small molecule imaging application using MALDI MS/MS. In Proceedings of the 53 rd ASMS Conference on Mass Spectrometry and Allied Topics, San Antonio, TX. 

In addition to some early applications in bioanalysis, ambient ionization mass spectrometry has been used as an imaging tool to study drug distribution in tissue sections. Most of the work reported so far involved the use of DESI as the ambient ionization method. Compared to other mass spectrometry-based tissue imaging techniques such as MALDI and SIMS, DESI allows tissue samples to be analyzed under ambient conditions without sample preparation, which simplifies the procedure and prevents the redistribution of analytes during matrix deposition. A major drawback of DESI as an imaging tool is its relatively low spatial resolution (typically 250 pm) and therefore cannot be used for cellular or subcellular imaging. 

Chen, Y., et al. (2008) Imaging MALDI mass spectrometry using an oscillating capillary nebulizer matrix coating system and its application to analysis of lipids in brain from a mouse model of Tay-Sachs/Sandhoff disease. Analytical Chemistry, 80, 2780-2788. 

Imaging MALDI Mass Spectrometry of Sphingollpids Using an Oscillating Capillary Nebulizer Matrix Application System... 

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