| Laser desorption ionization techniques, such as matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), have traditionally employed an organic matrix to enhance ionization efficiency of a sample. The matrix plays a major role in the ionization process by spatially separating the analyte molecules, absorbing laser energy, and donating protons to the analyte in the ion plume. However, a major drawback to MALDI-MS is the intense low mass-to-charge ion background that arises from the organic matrix. Matrix-free laser desorption techniques have been recently introduced in which the sample surface plays the role of the organic matrix without producing the high chemical background. With desorption/ionization on porous silicon (DIOS), the analyte is spotted on electrochemically etched porous silicon and no additional organic matrix is added. The resulting mass spectra are similar to MALDI spectra, but without the organic matrix background. However, the production of porous silicon is not entirely reproducible, which can lead to inconsistent MS data. The development of a new matrix-free laser desorption technique, called aerogel MALDI, is first reported here.; Aerogels are highly porous polymeric solids produced by cross-linking a colloidal dispersion of dissolved monomeric precursors. The resulting rigid gel is supercritically dried to avoid densification of the pore system; the resultant aerogel is highly porous and easily reproduced. The composition of the aerogel can be precisely controlled, and custom surfaces can be produced by selecting specific monomers or by modification of the surface after polymerization. Here, resorcinol-formaldehyde (RF) aerogels are characterized as organic-matrix free substrates for laser desorption on a quadrupole ion trap mass spectrometer.; To test the quantitative ability of the aerogel MALDI technique in the analysis of small biomolecules, the biomarkers attributed to the metabolic disorder medium-chain acyl-CoA dehydrogenase deficiency (MCADD), I-carnitine and octanoylcarnitine, were analyzed. In order to screen for MCADD, the relative concentration of the biomarkers must be determined from whole blood samples. For this, calibration curves were generated, using an internal standard, for each compound and compared to curves produced by MALDI-MS analysis. |
