Journal of Chromatography & Separation Techniques
Open Access

Comparison of the MALDI and TiO2-assisted SALDI mass spectra of hormones and amino acids

International Summit on Current Trends in Mass Spectrometry

July 13-15, 2015 New Orleans, USA

I Popovi�?, M Neši�? and M Petkovi�?

Posters-Accepted Abstracts: J Chromatogr Sep Tech

Abstract :

Surface-assisted laser desorption/ionization time of flight mass spectrometry (SALDI-TOF MS) have great potential to overcome poor reproducibility and high matrix-arising background in the low mass region, which commonly occur in the matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectra. In addition to a variety of highly abundant matrix-related ions in the low-mass range of the spectra, there are potential undesired polymerization reactions, which complicate the spectra, and in some cases, even prevent the detection of the ions of interests. In contrast, nanoparticles as substrates generate a lower number of background signals and low onset of fragmentation reactions in the gas phase. In this work, we compare the spectra of steroid hormones (estradiol, testosterone, progesterone), steroid medication (dexamethasone), amino acids (L-cysteine, L-alanine, L-methionine) and tripeptide (glutathione) acquired with traditional, organic matrices (DHB, 9AA, CHCA and THAP) with the spectra acquired with titanium dioxide (TiO2) nanoparticles of various shapes and dimensions, i.e. colloidal TiO2 nanoparticles (TiO2 NPs, average diameter ~5 nm), prolate nanospheroids (TiO2 PNSs, length: 40�??50 nm, the lateral dimension: 14�??16 nm) and nanotubes (TiO2 nanotubes, length: 100-150 nm, average diameter 11 nm). Various shapes and dimensions of substrates were used because it is well known that these factors determine the process of desorption and ionization. To compute repeatability (within day) and intermediate precision (between days) of MALDI and SALDI TOF techniques we used Excel tools (ANOVA test). In addition, homogeneity of the sample/matrix distribution on the target was also calculated and expressed as the coefficient of variation of a series of measurements. In summary, our results show that all three TiO2 nanoparticles have great potential for the detection and analysis of steroid hormones and amino acids with good analytical parameters (all variations do not exceed 15%). Additionally, homogeneity of the sample/ substrate mixture distribution on the target plate was satisfactory. Laser-induced ionization on nanostructures offers alternative ionization pathways through the formation of Na+ and K+ adducts with appreciable yield, in contrast to numerous matrixadducts detectable in the MALDI spectra acquired with traditional matrices. All the examined molecules were detectable in the negative ion mode with TiO2, which was not the case with all other organic matrices and substrates. Other advantages of the application of TiO2 nanoparticles as substrates for the analysis of low mass molecules are discussed.