Study of the mass spectrometric behaviors of anthocyanins in negative ionization mode and its applications for characterization of anthocyanins and non-anthocyanin polyphenols

RATIONALE Traditionally, anthocyanin analysis in mass spectrometry is carried out in the positive ionization mode only. A study of the mass spectrometric behaviors of anthocyanins in the negative ionization mode revealed interesting characteristics that was not previously reported. It can be used to differentiate anthocyanins from other non-anthocyanin polyphenols. METHODS An ultra-high-performance liquid chromatography with high-resolution mass spectrometry (U-HPLC/HRMS) method was developed. The method used multiple-stage mass fragmentation in both the negative and positive ion modes. The whole cycle time of the new method is 1.8 s for two full scans and six data-dependent scans. RESULTS The new strategy found, in the negative ionization mode, a series of characteristic ions, e.g. [M–2H]–, [M–2H + H2O]– , formic acid adducts, and doubly charged ions were observed for the MS analysis of anthocyanins. The characteristic ions can be used for identification and differentiation of anthocyanins and non-anthocyanin phenolic compounds. Comprehensive studies were performed on the differentiation of anthocyanins and non-anthocyanin polyphenols in blueberry (Vaccinium cyanococcus), Hongcaitai (Brassica compestris L. var. purpurea Bailey), and red radish (Raphanus sativus var. longipinnatus 'Shinrimei'). CONCLUSIONS The data generated from a single LC run enables rapid and reliable differentiation and identification of anthocyanins and non-anthocyanins in botanicals and foods. Published 2012. This article is a US Government work and is in the public domain in the USA.