Effects of Adduct Ions on Matrix-assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry of Condensed Tannins: A Prerequisite Knowledge

Three different condensed tannins were analyzed by MALDI-TOF MS, with Cs+ and Na+ being the cationization reagents. When Na+ was used as the cationization reagent, good quality MALDI-TOF spectra of condensed tannins were obtained, accompanied by the possibility of overevaluation of the gallocatechin/epigallocatechin units because of the influence of the remaining K+. It is critical to investigate the appearance of gallocatechin/epigallocatechin units in condensed tannins from special plant tissues for taxonomic information and for the better understanding of plant metabolism and other ecological properties. Cs+ is a suitable substitute for this situation. The more complicated MALDI-TOF spectrum of the complex condensed tannins from Bruguiera gymnorrhiza leaves was detected by the selection of Cs+ as the cationization reagent in the presence of Na+ and K+. Using MALDI-TOF without deionization or with deionization and selection of Cs+ as the cationization reagent rather than with deionization and selection of Na+, condensed tannin polymers of higher polymerization degree (PD) were observed. Meanwhile, the polymer with the highest intensity ion peak changed with the ion adducts used.