Improved silica xerogel film processing for MALDI-TOF–MS quantitative analysis of peptides and small molecules

In this work, sol–gel derived silica films were prepared for direct desorption/ionization of organic compounds in MALDI-TOF–MS analysis with the aim of improving method precision and of reducing interfering signals at low m/z values. Two commonly used MALDI matrices, 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA), were incorporated into the sol–gel network in order to absorb laser energy and to induce analyte desorption/ionization with low or absent background signals in the mass spectra. To achieve a reproducible xerogel film formation, experimental parameters for its deposition were optimized. The gel matrices were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) analysis. The results proved the embedding of the matrix molecules in a disperse form into the homogeneous sol–gel material. The sol–gel matrix was then tested for the qualitative and quantitative analysis of two reference peptides, such as Bradykinin and P 14 R. In addition, spectral quality and method performance were assessed for quantitation of melamine, a low-molecular weight compound of food safety concern. In all cases, high quality spectra and excellent mass accuracy (between 3.5 and 13 ppm) were observed. Furthermore, the experimental results evidenced a significant improvement of the measurement repeatability on spot and between spots (relative standard deviation