Self‐assembled‐monolayer‐modified silicon substrate to enhance the sensitivity of peptide detection for AP‐MALDI mass spectrometry

A self‐assembled‐monolayer‐modified silicon substrate was successfully used to enhance the sensitivity of peptide detection for atmospheric pressure‐matrix‐assisted laser desorption/ionization mass spectrometry (AP‐MALDI/MS). The effect of surface modification of silicon wafer samples with NH 2 and OH functional groups was investigated. In addition, solvent effects for the preparation of modified NH 2 ‐functionalized surfaces were examined. The sensitivities for the two peptides were significantly improved, increasing between 12 and 160 times, for bradykinin and gramicidin, respectively, on an NH 2 ‐modified silicon surface prepared in toluene, over that on a conventional gold substrate. The limits of detection (LODs) for bradykinin and gramicidin using the conventional gold substrate in AP‐MALDI/MS experiments were > 0.011 µM and 110 µM, respectively. Using our SAM approach, the LODs for bradykinin and gramicidin in AP‐MALDI/MS can be improved to 0.93 nM and 0.33 µM, respectively. This SAM approach for AP‐MALDI/MS is simple and sensitive, and can be used for high‐throughput analysis. Copyright © 2007 John Wiley & Sons, Ltd.