Масс-спектрометрическое исследование криопротекторов
Synthetic low-molecular-mass polymers – liquid oligomers of oxyethylated glycerol derivatives (OEGn) with different degree of polymerization (OEG-5, OEG-25, OEG-30), possessing cryoprotector properties, were studied by four mass spectrometric methods: fast atom bombardment (FAB), secondary ion mass spectrometry (SIMS), laser desorption/ionization (LDI) and matrix-assisted LDI (MALDI). Sets of peaks with bell-shape distribution of intensities, corresponding to protonated Mn•H+ and deprotonated oligomers [Mn–H] – of Мn were recorded in the positive and negative ion FAB and SIMS mass spectra of OEG-5. In the LDI and MALDI mass spectra (DHB matrix) of all polymers, the main sets correspond to cationized oligomers Mn•Na+, Mn•K+, formed due to attachment of alkali metal ions present in the samples or solvent in trace amounts. The main parameters of molecular mass distributions of OEGn oligomers – mean mass values and polydispersity index – were determined on the basis of mass spectrometric data. Some discrimination effects are observed in the positive ion LDI, MALDI and negative ion FAB, SIMS, whose reasons are discussed along with peculiarities of ions formation under the various techniques applied. Optimal mass spectrometric methods showing the best agreement with chromatographic data and the lowest discrimination effects were determined for analysis of each type of the polymers, which are FAB, SIMS and LDI for OEG-5 and MALDI for OEG-25 and OEG-30.
