Monolithic sorbents with covalently bonded matrix for thin layer chromatography coupled with matrix-assisted laser desorption/ ionization

Abstract

The possibility of creating monolithic plates containing functional groups capable of performing the
role of MALDI matrices is shown, and the first results on desorption / ionization of compounds with masses
of the order of 400 Da are demonstrated. Monolithic plates were prepared based on (co)polymers of glycidyl
methacrylate and ethylene glycol dimethacrylate with the content of the first from 0 to 29% and styrene and
divinylbenzene with the content of styrene from 0 to 35%. The best results were obtained for TLC plates with
glycidyl methacrylate content from 19 to 29% and with a styrene content of 5 to 20%. It is noted that the absence of a monofunctional monomer in the polymerization mixture resulted in the suppression of analyte
ionization and the impossibility of using such TLC plates in the MALDI-MS mode. Another factor affecting the possibility of desorption / ionization of compounds is the quality of the surface. The presence of roughness,
uneven surface dramatically affect the ability to work in the mode of MALDI-MS, and the monoliths,
containing less than 19% of the GMA, were mechanically fragile, and manipulation with them easily led to
surface damage. Similar results were obtained for monolithic sorbents based on (co)polymers of styrene and
divinylbenzene with styrene percentage lower than 10%. In order to obtain information on the surface relief,
monolithic layers were prepared on glass substrates (18 × 18 mm, 0.13–0.17 mm thick) with various contents
of monofunctional monomers and using various porogens and were studied by scanning electron microscopy.
According to the height distribution histograms, it was found that for a sample of St-DVB copolymer containing 30% styrene and 10% divinylbenzene in the initial polymerization mixture (undecanol-toluene solvent 52: 8) the highest density corresponded to an average roughness value of 150 nm, whereas for sample composition (14% GMA + 26% DMEG, 60% cyclohexanol), the highest density corresponded to an average roughness value of 50-60 nm. The proposed method for obtaining MALDI-MS-TLC spectra eliminates one of the most labor-intensive stages of the process associated with the preparation and application of the
MALDI matrix on a TLC plate