Coupling solid-phase microextraction and laser desorption ionization for rapid identification of biological material.

Solid phase microextraction (SPME) use small fibers directly plunged in the solution under investigation to quickly extract and quantify by different techniques the amount of selected dissolved compounds. Biological materials, peptides or proteins are accurately identified by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). They are difficult to extract by SPME. This work looks for a chemical to be deposited onto fibers and able to act as a good SPME extractant as well as efficient matrix for MALDI detection. 3-Hydroxy-2-naphthoic acid (HNA) and 2-hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid (HHSNNA) were compared to two classical matrices: α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydrobenzoic acid (DHB). Bound to silica particles, DHB and HNA were found to be good MALDI matrices. Only the wide pore particles gave observable spectra. These particles were then attached in a thin layer onto wires to be used as fiber tips in SPME. Fibers loaded with peptides were introduced into the mass spectrometer to record fiber laser desorption ionization (FILDI) spectra. SPME-FILDI experiments could quickly identify peptides and proteins in solutions. More work is needed to find the best matrix and the way to fix it onto the fiber.