Matrix-assisted laser desorption ionization using lithium-substituted mordenite surface

Laser Desorption Ionization Mass Spectrometry of Bioactive Substances by Using 2,4,6-Trihydroxyacetophenone on Cation-substituted Zeolite

“…The peak intensity enhancement of the analyte and the ionization by cations on the zeolite surface are the features of the zeolite matrix. [19][20][21] For the matrix molecules, a large peak of [THAP+H] + was observed in addition to [THAP+Na] + , although the peak of the protonated analyte was not observed.…”

“…Here, we also calculated the structures and the binding energetics of Na + and K + to THAP at the same level. 21 Since no 6-31+G(d) basis sets have been developed for K, we used almost equivalent basis functions by McLean and Chandler implemented in the Gaussian 09 program. 22 All of the structures were verified to be at the minima by harmonic vibrational analysis.…”

“…Cation exchange of the zeolite surface was reported previously. 20,21 Briefly, each of lithium acetate (CH3COOLi), sodium nitrite (NaNO2), and potassium nitrite (KNO2) was dissolved in distilled water to obtain a 6.0 mol L -1 solution. Zeolite HM20 was added to the solution, and the mixture was stirred for 1 h at 353 K. The mixture was filtered at room temperature, and the thus-treated zeolite was dissolved again in a lithium acetate, sodium nitrite, and potassium nitrite aqueous solution, and the mixture was stirred for 1 h at 353 K. We repeated this treatment three times.…”

“…[6][7][8][9][10] A matrix-free technique, such as desorption/ionization on porous silicon (DIOS), 11,12 and the use of a nanostructured surface have been proposed. 13 For example, Cheng et al measured the mass spectra of abused drugs by using a nanostructured silicon surface (nSi), and reported the advantages of their method by comparing with results obtained with GC and LC-MS. 14 Recently, we used cyclodextrin [15][16][17][18] and zeolite [19][20][21] as host molecules for typical MALDI matrices, and found that they suppressed the fragmentation of guest matrix molecules and increased the peak intensities of analytes.…”

“…In our previous studies, we reported possible ionization process of THAP adsorbed to H + -and Li + -substituted zeolite; proton (cation) transfer from zeolite to THAP via adsorbed water molecules in the electronic excited state of THAP. 19,21 In this study, we applied this THAP-zeolite complex ("zeolite matrix" hereafter) to the detection of six kinds of bioactive substances. We successfully measured the mass spectra of low-molecular-weight bioactive substances, saccharides, alkaloids, marine toxins, anticonvulsants, tranquilizers, and pesticides, which are hardly detected by conventional MALDI-MS.…”