Detection of small molecules using SBA-15 modified CHCA as a novel matrix of MALDI-TOF MS

It is challenging to apply matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) with analysis of small molecules efficiently. In this study, we describe the use of SBA15@APTES@CHCA as a novel silica-containing matrix to aid the analysis of small molecules with MALDI-TOF MS. To synthesize this novel matrix, 3-aminopropyltriethoxysilane (APTES) was used to bond alpha-cyano-4-hydnoxycinnamic acid (CHCA) and SBA-15 via Si=O and three CH2 alkyl chain. Furthermore, APTES also acts as flexible chains to allow CHCA molecules spreading over the surface of SBA-15, which increase the capacity of matrix to absorb energy and crystallize with sample. This novel matrix is more stable than an ionic macro complex matrix modified with SBA-15 and can be vacuum dried or air dried easily and stored for a long period:as powder. The structure of matrix was characterized by FTIR spectra and SEM. Twelve quinolone antibiotics (danofloxacin, enrofloxacin, ciprofloxacin, difloxacin, enoxacin, gatifloxacin, fleroxacin, lomefloxacin, sparfloxacin, norfloxacin, levofloxacin, pefloxacin, coumaphos, fenobucarb, carbendazim) and three pesticides (carbendazim, coumaphos, bassa) were applied to verify the feasibility of SBA-15@APTES@CHCA as a matrix for small molecules analysis. Several factors which affected the application of this matrix with mass spectrum analysis are discussed. The factors include suspension agent, matrix concentration, matrix/analyte ratio (v:v), sample preparation methods Compared with CHCA, as a matrix, SBA-15@APTES@CHCA displays distinct advantages on analysis of small molecules such as minimal chemical noise and improved analyte signal intensity. It is therefore a promising matrix to be used in MALDI-TOF MS analysis of low molecular weight analytes.