Dependence of the quality of SALDI TOF MS analysis on the TiO2 nanocrystals' size and shape

Titanium dioxide is widely used substrate for laser desorption and ionization [(SA)LDI] mass spectrometry. As the semiconductor with high UV absorbance and rapid energy transfer to analytes, TiO2 provides soft and efficient desorption/ionization of analytes with relatively low degrees of fragmentation in the gas phase. TiO2 nanocrystals are convenient for small molecules (molecular mass < 1000 Da) analysis due to low number of background signals. Desorption/ionization processes on TiO2 nanocrystals are related to the physical properties of the substrate, such as the ability to absorb and dissipate energy from the irradiating laser light source. In addition, size and shape of nanocrystals also affect these abilities. The aim of this study is to investigate the influence of shape and size dependant TiO2 nanocrystals/UV laser interaction on the quality of the mass spectra, detectability of analyzed molecules, intensities of the signals and homogeneity of co-crystals onto the MALDI plate, of carbohydrates. It is shown that the size and shape of nanocrystals influenced the way of packing carbohydrates onto plate, and thus affects homogeneity and reproducibility of mass spectrometry analysis.