High sensitivity and analyte capture with desorption/ionization mass spectrometry on silylated porous silicon

Sylation chemistry on porous silcon provides for ultra-high sensitivity and analyte specificity with desorption/ionization on silicon mass spectrometry (DIOS-MS) analysis. Here, we report that the silylation of oxidized porous silcon offers a DIOS platform that is resistant to air and acid/base hydrolysis. Furthermore, surface modification and appropriate hydrophobic silanes allows analytes to absorb to the surface via hydrophobic interactions for direct analyte extraction from complex matrixes containing salts and other nonvolatile interferences present in the sample matrix. This enables rapid cleanup by simply spotting the sample onto the modified DIOS target and removing the liquid phase containing the interference. This approach is demonstrated in the analysis of protein digests and metabolites in biofluids, as well as for the characterizing of inhibitors from their enzyme complex. An unprecedented detection limit of 480 molecules (800 ymol) for des-Arg(9)-bradykinin is reported on a pentaflourophenyl-functionalized DIOS chip.