Chemically modified porous silicon for laser desorption/ionization mass spectrometry of ionic dyes

✍ Scribed by I. V. Shmigol; S. A. Alekseev; O. Yu. Lavrynenko; N. S. Vasylieva; V. N. Zaitsev; D. Barbier; V. A. Pokrovsky

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 192 KB
• Volume: 44
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1604

✦ Synopsis

Abstract

Desorption/ionization on silicon (DIOS) mass spectra of model ionic dyes methylene blue (MB^+^Cl^−^) and methyl orange (Na^+^MO^−^) were studied using p^+^ type‐derived porous silicon (PS) free layers. As‐prepared PS (PS‐H), the PS thermally oxidized at 300 °C (PS‐OX), PS with chemically grafted cation‐exchanging alkylsulfonic acid (PS‐SO~3~H) and anion‐exchanging propyl‐octadecyldimethylammonium chloride (PS‐ODMA^+^Cl^−^) groups was tested as ionization platforms. Two mechanisms of the methylene blue desorption/ionization were found: (1) the formation of [MB + H]^+•^ ion due to the reduction/protonation of MB^+^, which is predominant for PS‐H and PS‐OX platforms and (2) direct thermal desorption of the MB^+^ cation, prevailing for PS‐SO~3~H. The fragmentation of the cation is significantly suppressed in the latter case. The samples of PS‐SO~3~H and PS‐ODMA^+^ Cl^−^ efficiently adsorb the dyes of the opposite charge from their solutions via the ion‐exchange. Consequent DIOS MS studies allow to detect only low fragmented ions (MB^+^ and MO^−^, respectively), demonstrating the potential of the ion‐exchange adsorption combined with DIOS MS for the analysis of ionic organic compounds in solutions. Copyright © 2009 John Wiley & Sons, Ltd.