Specification of M+3-hydroxypyrone chelation complexes by electrospray ionization ion trap and Fourier transform ion cyclotron resonance mass spectrometry

Kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone) is known to have a high affinity for transition metals, and it and its derivatized cogeners are used both analytically and clinically. The interactions between kojic acid (KA) and eleven +3 metals (Al+3, As+3, Cr+3, Ga+3, Fe+3, In+3, Yb+3, Y+3, Gd+3, Nd+3 La+3) were examined by electrospray ionization mass spectrometry (EST-MS) using an ion trap in an aqueous medium. For a subset of five ions, Fourier transform ion cyclotron resonance (FTICR)-MS was conducted to provide accurate mass confirmation of peak assignments for metals having clustering of abundant isotopes. KA readily formed complexes with all the metal ions tested. The most common complexes observed were ML3H+ and M2L5. Different behavior was seen for small and large ionic radius ions, with a relative cut-off between In+3 (similar to 80 pm) and Yb+3 (similar to 87 pm); a striking trend in % collision energy vs. cluster complexity was revealed. The KA-Cr+3 complex shows a high affinity for H2O molecules in the gas phase, whilst In+3 shows a preference for dimetal complexes and Y+3 a deviant behavior when complexed to two neutrals. Copyright (c) 2007 John Wiley & Sons, Ltd.