I know that sometimes glyercol is used a liquid
matrix in IR MALDI, but I have ever heard about Ionic Liquid Matrices (ILMs)
before. These type of matrices are trying to eliminate the drawbacks of
commonly used MALDI matrices, which in most of the cases are organic acids,
having a really pKa in order to achieved analyte protonation.
ILMs have a low melting point, low vapor
pressure and high stability at AP and vacuum. They do not create dangerous
fumes and are considered to be a greener technology compared to conventional
MALDI Matrices. They do not display crystallization, therefore sample
preparation is supposed to be really homogeneous - which is one of the biggest
advantages applicational-wise. So there is no need to find the “sweet” spots on
your sample anymore.
ILMs are composed of a mixture of organic salts
and bases. This unique mixture leads to a high ionization performance with the
analyte due to ion pairing via electrostatic or hydrogen bonding between the
matrix compounds and impurities. Since the protons are originated from the salt
rather than from a weak carboxylic acid group ILMs display higher proton
exchange efficiencies compared to conventional matrices.
They do not cause fragmentation (even for
non-covalent bonds) or cluster and alkali adduct formation. Thus, they are less
prone to denaturation of biomolecules compared to acidic DHB and CHCA (pKa of 3
and 1.2) matrixes. ILM can be pH controlled by the organic base to minimize degradation,
denaturation or fragmentation of labile biomolecules at low pHs.
Additionally, strength and concentration of base regulates the UV-absorbance, since a difference in charge status changes the localization of electrons within the molecule therefore changes the absorbance properties of the matrix towards lower (hypsochromic shift) or higher (bathochromic shift) wavelengths.
Source:
https://www.omicsonline.org/open-access/ionic-liquids-matrices-for-laser-assisted-desorptionionization-massspectrometry-2469-9861-1000109.php?aid=65371
Additionally, strength and concentration of base regulates the UV-absorbance, since a difference in charge status changes the localization of electrons within the molecule therefore changes the absorbance properties of the matrix towards lower (hypsochromic shift) or higher (bathochromic shift) wavelengths.
Source:
https://www.omicsonline.org/open-access/ionic-liquids-matrices-for-laser-assisted-desorptionionization-massspectrometry-2469-9861-1000109.php?aid=65371
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