Spectroscopic verification of ionic matrices for MALDI analysis

Abstract Ionic liquid matrices have been recognized for MALDI application since 2001. However, specific information about the physical and chemical properties, ionicity or proper nomenclature of new matrices has never been presented. The aim of this investigation was to determine the chemical and physical characteristics of ionic matrices using spectroscopic techniques (UV–Vis, IR, 1 H NMR). 66 mixtures of acids (standard MALDI matrices) and bases (organic amines) were prepared. The results obtained show that 1 H NMR analysis, with supporting information from IR analysis, was helpful in the determination of the ionic character of the new matrices. Furthermore, thermogravimetric and cryometric analyses enabled the examination of the melting and decomposition points, in addition to the physical state of the obtained products, necessary for the classification of the new matrices. As a result, only a few acid and base mixtures could be categorized as ionic liquid matrices. What is important is that there were liquid matrices without an ionic character, and solid matrices with an ionic character. Thereby, a new categorization of matrices was introduced.