Matrix Interference-Free Method for the Analysis of Small Molecules by Using Negative Ion Laser Desorption/Ionization on Graphene Flakes

Abstract

This work presents a new approach for the analysis of small molecules with direct negative ion laser desorption/ionization (LDI) on graphene flakes. A series of matrix interference-free mass spectra were obtained for the analysis of a wide range of small molecules including peptides, amino acids, fatty acids, as well as nucleosides and nucleotides. The mixture of analytes and graphene flakes suspension were directly pipetted onto a sample plate for LDI-time-of-flight mass spectrometry (TOFMS) analysis. Deprotonated monomeric species [M-H](-) ions were homogeneously obtained on uniform graphene flakes film when negative ion mode was applied. In positive ion mode, the analytes were detected in form of multiple adduct ions such as sodium adduct [M+Na](+), potassium adduct [M+K](+), double sodium adduct [M+2Na-H](+), double potassium adduct [M+2K-H](+), as well as sodium and potassium mixed adduct [M+Na+K-H](+). Better sensitivity and reproducibility were achieved in negative ion mode compared to positive ion mode. It is believed that the new method of matrix interference-free negative ion LDI on graphene flakes may be expanded for LDI-MS analysis of various small molecules.

Screening of Toxic Chemicals in a Single Drop of Human Whole Blood Using Ordered Mesoporous Carbon as a Mass Spectrometry Probe

“…The spectra were recorded by summing 200 laser shots. Since the MS spectra obtained in negative ion mode were clearer than those in positive ion mode, 24 the MS experiments were performed in negative ion mode.…”

Graphene and graphene oxide as nanomaterials for medicine and biology application

“…The new matrix has the potential to eliminate the interference of matrix background ions, avoid the fragmentation of analytes and also improve shot-to-shot reproducibility. Later, Lu et al introduced the use of graphene flakes as a very effective matrix for analysis of large-scale small molecules, which include peptides and fatty acids [146]. According to this study, graphene can be used to characterize polymers with average molecular weights from 425 to 3500 kDa.…”

High Throughput Enzyme Inhibitor Screening by Functionalized Magnetic Carbonaceous Microspheres and Graphene Oxide-Based MALDI-TOF-MS

“…However, the performances of these matrices are not desirable when utilized to detect low molecular weight compounds (G600 Da) [35]. Strong background interferences were observed when CHCA was used as matrix [17], i.e., ACh and choline detection [12]. These interferences would greatly obscure the targeted compounds' detection.…”

“…From reports by others [12], the introduction of internal standards can compensate signal variations successfully. On the other hand, background interferences could be greatly reduced by utilizing proper matrices (i.e., graphene), especially for small organic molecule detection (G600 Da) [13][14][15][16][17][18]. Possessing unique electronic, optical, thermal, and mechanical properties [19], graphene oxide can be produced by oxidizing graphite, which is heavily oxygenated.…”