Hybrid bismuth oxide-graphine oxide nanomaterials improve the signal-to-noise response of small molecules analyzed by matrix assisted laser desorption ionization-time-of-flight mass spectrometry.

Matrix-assisted laser desorption ionization (MALDI) has received increasing attention for the analysis small molecules. Nanomaterials are frequently used as the matrix in LDI, and various inorganic materials have been developed, particularly those based on thermally-driven positive DI mechanisms. However, the unwanted detection of alkali metal ion adducts in the positive ion mode can compromise small molecule identification. Here, we report the synthesis and application of a novel hybrid bismuth oxide-graphene oxide (BiO@GO) semiconductor matrix for the analysis of small molecules by LDI-time-of-flight mass spectrometry (TOF-MS) operating in the negative ion mode. The structure of the semiconductor nanomaterial was characterized using conventional methods and its performance for the detection of small molecules (e.g., amino acids, fatty acids, sugars and other small molecules) was compared with traditional DI matrices (e.g., cyano-4-hydroxycinnamic acid, 2,5-dihydroxybenzoic acid, 9-aminoacridine and GO). The results showed that the negative ion LDI-TOF MS of small molecules on BiO@GO were free of matrix-related interferences, and possessed good signal intensity and repeatability. Application of BiO@GO to the quantitative determination of glucose in human serum and soft drinks confirmed that the hybrid matrix could also be applied to complex samples. Conclusions drawn from the experimental results, computational chemistry calculations, and previous studies, suggesting that interfacial photogenerated thermal electron transfer and capture are key processes in the LDI mechanism.