Klára Novotná

Mass spectrometry of humic substances of different origin including those from Antarctica A comparative study.

Mass spectra of humic acids (HA) from different sampling sites (Antarctica, Brazil, Czech Republic, Mexico and USA) and origin (plant, soil, peat, and coal derived) were obtained by laser desorption/ionization time of flight mass spectrometry (LDI-TOF MS). Optimisation of the experimental conditions are given as the optimal value of the laser energy at approximately 20-30% higher than the threshold. Under these conditions, reproducible mass spectra of HA samples were obtained. In the mass spectra the majority of the peaks are observed in the m/z region 100-1000Da. Mass spectra fingerprints of HA were analyzed and, in spite of the differences in their origin, a number of common features and profiles (patterns of peaks) were observed in most of the samples. Very similar structural groups (patterns) of the peaks are present in the m/z range 717-918Da for HA samples of quite different origins, countries or continents. The tandem LDI-TOF MS and multivariate statistical tools allowed us to extract and elucidate underlying information contained in the mass spectra of the HA samples under study. Applying principal components and cluster analysis, it was, e.g. demonstrated that most of the Antarctica HA samples show distinguishable differences when compared with humic acids from other continents and of different origin.

Separation and characterization of humic acids from Antarctica by capillary electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry: Inclusion complexes of humic acids with cyclodextrins

A new capillary electrophoresis procedure based on micellar electrokinetic capillary chromatography for the separation of humic acids (HAs) isolated from Antarctica soil was developed. The HAs were separated and characterized using a background electrolyte containing 0.09 M borate+0.09 M Tris+0.001 M EDTA (BTE) of pH 8.3, modified with alpha-, beta-, or gamma-cyclodextrins (CDs) and sodium dodecyl sulfate. It was found that from alkaline solution of HAs in the presence of CDs, the HAs are not completely precipitated with a strong acid and a certain part (some fractions) remains soluble. Mass spectrometry shows that HAs contain 15-25 simple low-Mr compounds and several families of compounds with similar structure (m/z approximately 800-1200). Comparison of HA analysis from Antarctica soil with those of soil HAs from the American continent show a high similarity between the samples and confirm several identical compounds and some with very similar structural units.