An auxiliary matrix for routine analysis of small molecules and biological macromolecules using matrix-assisted laser desorption ionization mass spectrometry

The great hurdles related with matrix-assisted laser desorption/ionization (MALDI) analysis are inhomogeneous crystallization, poor reproducibility, and low sensitivity. To effectively improve the performance of MALDI mass spectrometry (MS), graphene oxide (GO) was first utilized as an auxiliary matrix of the conventional matrices, including 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydoxycyanocinnamic acid (CHCA), 2,4,6-trihydroxyacetophenone (THAP), and 3,5-dimethoxy-4-hydroxycinnamic acid (SA), for the analysis of small molecules and biological macromolecules on different MALDI MS systems. The results revealed that the DHB-GO composite matrix could provide much superior crystal homogenization, better reproducibility, higher sensitivity, and more excellent linearity for the statins’ tissue imaging on iMScope than the single-use DHB matrix. Moreover, the DHB-GO dramatically improved the spot-to-spot and shot-to-shot reproducibility, crystal homogenization, sensitivity, and linearity of MALDI-TOF MS for statins’ analysis in dried droplet. The capability of THAP on the analysis of lipids, similarly, could be greatly enhanced by the combined use of GO. THAP-GO composite matrix was expected to be widely used in the MALDI MS-based liposome studies. It was also found that CHCA-GO could provide superior analytical performance for peptides. The sensitivity and reproducibility of intact proteins could be greatly improved by SA-GO composite matrix. More importantly, the better reproducibility produced by the composite matrices sufficiently indicated that low concentration (0.1 mg mL−1) of GO almost did not cause contamination to MALDI MS system. Thus, GO was proved to be a versatile auxiliary matrix for the MALDI MS-based routine analysis of small molecules and biological macromolecules.