In this study we demonstrated the influence of pressure on the retention of macromolecules such as oligonucleotides, plasmid DNA and proteins when performing separations on an ion exchange column. With the rise of pressure the macromolecules retained stronger and the increase of retention was dependant on the size, shape and flexibility of the molecule. Changes in retention have a pronounced impact on the method transfer from an HPLC to a UHPLC system, where separations are faster and performed under higher pressures. Such UHPLC methods are preferred in the biopharmaceutical research and development where batches of newly developed biosimilars need to be monitored and characterised. One possibility would be to add the investigated pressure effect as a quality control parameter as it may enable us to differ between properly folded and unfolded biomolecules based on their retention time shift with increase in pressure as was shown in this study.
COBISS.SI-ID: 1538179011
The preparation of nanostructured bismuth film electrode (nsBiFE) via ex-situ multi-pulse galvanostatic deposition protocol is presented. The nsBiFE was prepared on a glassy carbon substrate electrode and studied for anodic stripping voltammetric detection of trace metal ions Cd2+ and Pb2+. Several important parameters were examined and optimized, such as the composition of plating solution, pulse deposition current, pulse duration (pulse deposition time and relaxation time) etc.
COBISS.SI-ID: 6198298
All-in-one iron-based microrockets with efficient propulsion in acidic environment using hydrogen evolution reaction were demonstrated for the first time. On the basis of iron magnetic properties microrockets exhibit extended lifetime, facile magnetic guidance, heavy cargo pickup and release, and self assembly capability (e.g. formation of microrocket-trains). Leveraging the intrinsic biocompatibility of iron (nontoxicity) with its multipurpose role, including ferromagnetic and mechanical properties and as low costs fuel in our microrocket design is an important step towards wider in vivo use of micromotors for medical application, e.g. guided drug delivery.
COBISS.SI-ID: 1537406659
A new variable distance weighted zero order connectivity index was used for development of structure activity relationship for modeling reactivity of OH radical with volatile organic compounds. Index was developed for the purpose of better understanding mechanisms of such reactions. By assuming that all reaction sites are interrelated by influencing each other our model permit some insight into mechanisms that govern the reactions. Results of modeling alkanes and non-conjugated alkenes show that branching degree of the forming radical seems to play a major role in site specific reaction rates. More specifically, allylic carbon appears to be more reactive than current models suggest. This is an important scientific contribution in understanding secondary organic aerosol formation. This could be one of the important reaction pathways neglected by current models as they underestimate secondary organic aeorosol formation by as much as 10-fold. Novel modeling software MACI, which was developed in our lab and is now available for research purposes, was used for calculations. Various variable topological indices that are again starting to be recognized because of their great potentials in simplicity, fast calculations, very good correlations and structural information, were implemented in the program.
COBISS.SI-ID: 1536789955
Electrochemical study of iron phytate complexation on HMDE and Au electrode showed that shift of formal redox potential is due to higher iron(III) phytate stability, and that slow charge transfer of redox processes may lead to overestimation of apparent stability constants derived solely from voltammetric data. We also proved that irreversible reduction of Fe(III) phytate is diffusion-controlled one electron reaction and that electronic configuration and iron’s octahedral coordination affinity induce inversion of phytate from equatorial to axial conformation, forming significantly more stable complexes. Iron(II) phytate intermediate is strongly adsorbed on both electrode surfaces. Using voltammetric peak analysis, cathodic charge transfer coefficient, diffusion coefficient, and rate constant k0 were calculated for predominant [FeIIIH3Phy]6– species. Fundamental study contributes to better understanding of biologically relevant iron phytate system, including its antioxidant and anticancer activity in living organisms.
COBISS.SI-ID: 1536395203
We have separated 57 species from samples of commercial melamines with preparative HPLC. Using electrospray ionisation and atmospheric pressure chemical ionisation structural elucidation was performed. Structures were also confirmed by Fourier transform infrared spectrometry and Nuclear magnetic resonance. In-source themally induced fragmentation of some fractions and presence of different conformers was confirmed. This study showed that mainly monomers and dimers are present in the sample. Based on the data further improvement of the manuifacturing proces can be done and different influences on the characteriscs of melamine scan be studied.
COBISS.SI-ID: 1536399043
A method for determination of atropine and scopolamine was developed and validated, using only 100 uL of human plasma. These compounds are natural and very toxic plant alkaloids found in some members of nightshade family. Sample pretreatment consisted of protein precipitation with acetonitrile followed by a concentration step. Analytes and internal standard were separated by liquid chromatography on reverse phase and with a gradient elution and were quantified by mass spectrometry (triple quadrupole, positive ESI ionization). Selected reaction monitoring (SRM) was used for quantification in the range 0.10–50.00 ng/mL. Method was validated by determination of inter- and intra-day precision, limit of quantification (LOQ), limit of detection (LOD), matrix effect for deproteinised plasma samples, and accuracy. All parameters were satisfactory. Method can be used for determination of therapeutic and toxic levels of both compounds. It has been successfully applied to a study of pharmakodynamic and pharmakokinetic properties of both alkaloids, where plasma samples of volunteers were collected at fixed time intervals after ingestion of buckwheat meal, spiked with low doses of alkaloids. Study was performed to determine the maximal residue limit for these alkaloids in food and was done following the mass intoxication with buckwheat meal polluted with seeds of Datura sp. from nightshade family.
COBISS.SI-ID: 1712431
Anticoagulant level in blood samples can influences the results of haematological tests. A methodology that enables the end user to evaluate the quality of evacuated blood collection tubes before a specimen collection was proposed for the first time and confirmed that not every blood-collection tube during its shelf-life complies with the requirements of the standards. Internal quality control in biomedical laboratories profited since it is now possible to ensure that evacuated blood-collection tubes are used only if and only until their quality is adequate. The awareness that the laboratories have such a methodology can influence the manufacturers to further improve their production quality.
COBISS.SI-ID: 36397061
We successfully transferred and applied omics concepts to the study of material degradation, in particular historic paper. The main volatile degradation products of paper, constituting the particular “smell of old books”, were determined using headspace analysis after a 24 h predegradation procedure. Using methods of multivariate data analysis, we were able to quantitatively correlate volatile degradation products with properties important for the preservation of historic paper.
COBISS.SI-ID: 33296901
In the present work, we derive a theoretical framework to determine the adsorbed layer thickness from pressure drop measurements for convective monolithic media without any assumptions about the geometry of the pore structure of the stationary phase matrix. Equations are presented to calculate accuracy of the estimated adsorbed layer thickness as a consequence of measurement error and approximations of the mathematical model. We discovered that there is a minimum in the error for certain pressure drops that results in optimal experimental conditions for determining the adsorbed layer thickness. We demonstrate that the adsorbed layer thickness can be determined with less than 10% error using a wide range of experimental conditions simply from pressure drop data. By careful selection of porous bed dimensions and flow rates, the adsorbed layer thicknesses from sub-nanometer dimensions up to several hundred nanometers can be determined by measurement of the pressure drop in a range of several bars. The method was experimentally tested on methacrylate monolithic columns using mono-disperse latex nanoparticles as a reference standard and two different proteins as unknowns, demonstrating close agreement with calculations. Method enable monitoring of adsorption in real time enabling better understanding of adsorption phenomena.
COBISS.SI-ID: 1537765571