Profiling of glucose degradation products through complexation with divalent metal ions coupled with ESI/qTOF/MS/MS analysis.

Sugar degradation products generated through thermal treatment of foods are considered the key precursors for various flavor compounds, toxicants and browning, but their high reactivity makes their detection difficult. In this study, a convenient analytical procedure for profiling of various reactive sugar intermediates having enediol or -dicarbonyl moieties through complexation with divalent metal ions combined with electrospray ionization/quadrupole time-of-flight mass spectrometry was developed. Excess divalent iron chloride (FeCl) was added to glucose or U6-[glucose] solutions in methanol either before or after heating at 110 °C for 2 h, and the samples were analyzed by tandem mass spectrometry. The results indicated the formation of ethylene glycol, glycolaldehyde, glyceraldehyde, glycerol, methylglyoxal, glyoxylic acid, erythrose, erythrosone, 3-deoxy-erythrosone, erythritol, ribose, ribosone, 3-deoxy-ribose, ribitol, 3-deoxy-glucosone, and rhamnose. These sugars and sugar degradation products acting as bidentate ligands were detected as positively charged mono- and bis-sugar iron complexes in the form of [M + H], [M + Na], [M + K], [M + FeCl], and [M + FeCl], as well as by charge localization on iron [M]. The divalent metal complexation technique was applied for the profiling of sugar degradation products in aged manuka honey.