Dagmar Gajdošová

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.

Uranium oxide clusters by laser desorption ionization during MALDI-TOF MS analysis of uranium(VI)

Laser desorption ionization (LDI) mode of matrix-assisted laser desorptionionization time-of-flight mass spectrometry (MALDI-TOFMS) analysis of uranium(VI)leads to the formation of uranium oxides clusters, as with fast atom bombardment(FAB). Different uranium clusters than those with FAB were observed. Threedifferent families of formula (UO2)x Oy2+, and two of formula (UO2)x Oy2+ were found.

Validation of a Capillary Zone Electrophoresis Method for Determination of Rimantadine Hydrochloride in Rimantadin100 Tablets and the Method Application to Dissolution Test Monitoring

A capillary zone electrophoretic method with indirect UV‐detection for determination of rimantadine, an antiviral drug against influenza A, in tablets was validated. Instrumental precision, the method precision, accuracy, calibration curve linearity, selectivity, robustness, and time stability of the sample and the standard were tested. The method was also applied to monitor dissolution tests of the tablets. The possibility of addition of an internal standard for improvement of the method precision was discussed.

Determination of esmolol in serum by capillary zone electrophoresis and its monitoring in course of heart surgery

A new Capillary Zone Electrophoresis (CZE) procedure for determination of esmolol, an ultra-short-acting beta-blocker, in serum was developed. Dichloromethane was applied as a deproteination agent and it was used also for the inactivation of erythrocytal esterase and in the same time for the extraction of esmolol from blood. The re-extraction of esmolol from organic phase to water phase was performed by 0.01 M HCl. An aliquot of 200 ml of acid aqueous phase was used for the injection and analysis. CZE determination was done in 50 mM phosphate buffer (pH=8.0) with detection at 222 nm. The concentration detection limit of esmolol in serum was 0.051 microg/ml. This method was applied in an extensive heart surgery experiment on pigs (Sus scrofa).

Direct laser desorption ionisation time-of-flight (TOF) mass spectrometry of soil organic matter for fast soil fingerprints

Dissolved organic matter and water-extractable organic matter influence soil biological activity, affect the transport of metals and organic pollutants, and contribute to mineral weathering and podzolisation. An important part of soil organic matter (SOM) are humic substances (HS), the major sinks of organic carbon on Earth, found everywhere including Antarctica. HS and humic acids are isolated from soils using various extraction agents and isolated products are often characterised by mass spectrometry. In this work, detailed study of laser desorption ionisation of SOM and of humic acids directly from soils was performed. The micro-extraction procedure was optimised and the most suitable method was found to be direct ionisation of SOM from a soil after addition of a diluted NaOH solution. In this way, in situ release of adsorbed and bound SOM from soils is achieved and direct analysis by laser desorption ionisation time-of-flight mass spectrometry is possible without any tedious extraction procedure. The developed methodology enables fast screening of soil organic matter to obtain fingerprints and thus to follow the differences between soils from various environments. The developed procedure was applied to soil samples from several continents, including Antarctica, and to volcanic soils from the Canary Islands.

Minimization of adsorption in capillary zone electrophoresis of proteins and neuroprotective peptides

Four types of coating procedures suitable for protein and peptides separation: covalent coating using polyethyleneimine (PEI), 3-glycidoxy-propyltrimethoxysilane (GPTMS), 3-aminopropyltriethoxysilane (APS) and a new approach of dynamic coating with linear polyacrylamide (LPA) have been studied. The capillary surface was characterized by determination of the electroosmotic flow (EOF); for optimization a model mixture of proteins (cytochrome C, lysozyme and ribonuclease A) was used. Separation of a neuroprotective peptide [Gly-14]humanin was demonstrated in the optimized system.