Spray-droplet matrix application

Several methods have been used for the matrix application (1) immersing a tissue section quickly in a matrix solution, (2) spraying matrix solution onto a tissue section with an air brush, (3) putting small droplets of matrix solution onto a tissue section with an automatic pipetting device that can dispense picoliter volumes (lpL = 10 pk) of reagents.4,5,715161819... 

Another approach to matrix application is to robotically deposit small (pL to nL) droplets of matrix on discrete areas of the sample surface. When the droplets are deposited as arrays over the entire tissue surface, mass spectra can be acquired at each matrix spot and reconstructed into an image. In this case, potential analyte delocalization is limited to the area under the matrix spot, typically -100-250 pm with commercially available spotters (e.g., Portrait 630 by Labcyte [23], ChIP by Shimadzu, TM iD by LEAP Technologies). This approach is fundamentally a trade-off between spatial integrity and resolution, because what limits resolution in most cases is the diameter of the laser beam, which is typically much smaller than the diameter of the matrix spot (on the order of 30-50 pm). Samples prepared by spray-coating, either manually or robotically, may be imaged at the diameter of the laser beam, but may not have maintained analyte localization throughout the spray process. 

MALDI Matrix Application Dried Droplet Versus Spray... 

Modem chemical warfare (CW) agents are produced as solids or liquids, depending on the application. Liquids can be volatile, such as sarin (GB), which converts to vapor form quickly, or nonvolatile, such as VX (O-ethyl S-diiso-propylaminoethyl methylphosphonothiolate), which emits almost no vapor at standard temperatures. Liquids can also be sprayed into the air as aerosols or fixed on a solid matrix such as silicone particles (dusty agents), or perhaps be fixed on soil particles. In these cases, volatile agent droplets or volatile agents... 

Once the section is mounted to the sample plate with the desired orientation, matrix solution is deposited on the tissue surface by electrospray deposition, aero spray, or using robotics to deposit small matrix droplets across the tissue surface before MALDI analysis [13]. The most common and least expensive devices available for applying matrix are hand-held aerosol sprayers or air brushes. The main advantage of these devices is that, with careful application, a dispersion of very small droplets... 

Much of the work in this area has been done in emulsions having a droplet size of more than 1 pm, and the application of submicron (nano) emulsions in encapsulation of oils and flavors is relatively new in the literature. Some works have been carried out to determine the influence of submicron emulsions produced by different emulsification methods on encapsulation efficiency and to investigate the encapsulated powder properties after SD for different emulsion droplet sizes and surfactants. The process has been referred to as nanoparticle encapsulation since a core material in nanosize range is encapsulated into a matrix of micron-sized powder particles (Jafari et al., 2008). This area of research is developing. Some patents were filed in the past describing microemulsion formulations applied to flavor protection (Chung et al., 1994 Chmiel et al., 1997) and applications in flavored carbonated beverages (Wolf and Havekotte, 1989). However, there is no clear evidence on how submicron or nanoemulsions can improve the encapsulation efficiency and stability of food flavors and oils into spray-dried powders. 

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