Temperatura effect on the stability of compounds used as UV-MALDI-MS matrix: 2,5-Dihydroxybenzoic acid, 2,4,6-Trihydroxyacetophenone, trans-a-Cyano-4-hydroxycinnamic acid, 3,5-Dimethoxy-4-hydroxycinnamic acid, nor-Harmane and Harmane.

TARZI OI; NONAMI H.; ERRA BALSELLS, ROSA

JOURNAL OF MASS SPECTROMETRY

John Wiley & Sons,

Lugar: London; Año: 2009 vol. 44 p. 20 - 277

1076-5174

Thermal stability of several commonly used crystalline UV-MALDI-MS matrices, 2,5-dihydroxybenzoic acid (gentisic acid; GA), 2,4,6-trihydroxyacetophenone (THA), a-cyano-4-hydroxycinnamic acid (CHC), 3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid; SA), 9H-pirido[3,4-b]indole (nor-harmane; nor-Ho), 1-methyl-9H-pirido[3,4-b]indole (harmane; Ho), perchlorate of nor-harmanonium ([nor-Ho+H]+) and perchlorate of harmanonium ([Ho+H]+) was studied heating them at their melting point and characterizing the remaining material by means of different MS techniques (EI-MS, UV-LDI-TOF-MS and ESI-TOF-MS) as well as by thin layer chromatography analysis (TLC), electronic spectroscopy (UV-absorption, fluorescence emission and excitation spectroscopy) and 1H nuclear magnetic resonance spectroscopy (1H-NMR). In general, all compounds except for CHC and SA remained unchanged after fusion. CHC showed loss of CO2 yielding the trans-/cis-4-hydroxyphenylacrilonitrile mixture. This mixture was unambiguously characterized by MS and 1H-NMR spectroscopy, and its sublimation capability was demonstrated. These results explain the well known cluster formation, fading (vanishing) and further recovering of CHC when is used as matrix in UV-MALDI-MS. Commercial SA (SA 98%; trans-SA / cis-SA 5:1 ) showed mainly  cis- to trans- thermal isomerization and, with very poor yield, loss of CO2 yielding as decarboxilated product (3’,5’-dimethoxy-4’-hydroxyphenyl)-1-ethene. These thermal conversions would not affect drastically its behaviour as a UV-MALDI matrix on the contrary that happens in the case of CHC. Complementary studies of photochemical stability of these matrices in solid state were also conducted.