Nikola Stevanović

Influence of organic modifiers on RP-TLC determination of lipophilicity of some polydentate Schiff bases

The lipophilic character of polydentate Schiff bases was investigated by reversed-phase thin-layer chromatography. In order to determine retention parameter as a measure of the lipophilicity of the tested compounds, three different binary solvent systems, composed of water and organic modifier (methanol, acetonitrile, and tetrahydrofuran), were used. Lipophilicity parameters together with 2D molecular descriptors were subjected to the multivariate statistical analysis. Principal component analysis was employed to reveal the most influential factors governing the lipophilicity of the investigated compounds. Finally, the influence of organic modifier on determination of lipophilicity parameters was discussed.Graphical abstract

Development of a Flow Injection System for Differential Pulse Amperometry and Its Application for Diazepam Determination

This work presents the development of a flow injection system for differential pulse amperometry (DPA) for diazepam determination in the presence of oxygen. The thin flow cell consisted of the bare glassy carbon electrode, reference silver/silver chloride, and stainless steel as the auxiliary electrode. Electrochemical reduction of diazepam (DZP) was characterised by cyclic voltammetry. Azomethine reduction peak was used for DZP quantification. The detector response was linear in the range 20–250 µmol/dm3 of diazepam, with a calculated detection limit of 3.83 µg/cm3. Intraday and interday precision were 1.53 and 10.8%, respectively. The method was applied on three beverage samples, energetic drink, and two different beer samples, and obtained recoveries were from 93.65 up to 104.96%. The throughoutput of the method was up to 90 analyses per hour.

Effect of substituents on prediction of TLC retention of tetra-dentate Schiff bases and their Copper(II) and Nickel(II) complexes.

The objectives of this study were to gain insights into structure-retention relationships and to propose the model to estimating their retention. Chromatographic investigation of series of 36 Schiff bases and their copper(II) and nickel(II) complexes was performed under both normal- and reverse-phase conditions. Chemical structures of the compounds were characterized by molecular descriptors which are calculated from the structure and related to the chromatographic retention parameters by multiple linear regression analysis. Effects of chelation on retention parameters of investigated compounds, under normal- and reverse-phase chromatographic conditions, were analyzed by principal component analysis, quantitative structure-retention relationship and quantitative structure-activity relationship models were developed on the basis of theoretical molecular descriptors, calculated exclusively from molecular structure, and parameters of retention and lipophilicity.

Study of pyrolysis of high density polyethylene in the open system and estimation of its capability for co-pyrolysis with lignite

Pyrolysis of high density polyethylene (HDPE) in the open system was studied. A plastic bag for food packing was used as a source of HDPE. Pyrolysis was performed at temperatures of 400, 450 and 500 °C, which were chosen based on thermogravimetric analysis. The HDPE pyrolysis yielded liquid, gaseous and solid products. Temperature rise resulted in the increase of conversion of HDPE into liquid and gaseous products. The main constituents of liquid pyrolysates are 1- n -alkenes, n -alkanes and terminal n -dienes. The composition of liquid products indicates that the performed pyrolysis of HDPE could not serve as a standalone operation for the production of gasoline or diesel, but preferably as a pre-treatment to yield a product to be blended into a refinery or petrochemical feed stream. The advantage of a liquid pyrolysate in comparison to crude oil is the extremely low content of aromatic hydrocarbons and the absence of polar compounds. The gaseous products have desirable composition and consist mainly of methane and ethene. The solid residues do not produce ash by combustion and have high calorific values. Co-pyrolysis of HDPE with mineral-rich lignite indicated positive synergetic effect at 450 and 500 °C, which is reflected through the increased experimental yields of liquid and gaseous products in comparison to theoretical ones.

Carbon stable isotope composition of modern and archaeological Cornelian cherry fruit stones: a pilot study

ABSTRACT The carbon stable isotope content of Cornelian cherry stones collected from wild tree stands in Serbia, SE Europe, was measured using elemental analyser-isotope ratio mass spectrometry, with the aim of recording natural carbon isotope composition of the fruit stones and its possible variation. The results show a significant variation in the carbon isotope values; we identified several environmental factors that, along with a number of other possible determinants, likely contributed to this variation. The obtained data are compared with the measurement of carbon isotope content of an archaeological specimen of Cornelian cherry stone discovered at the Neolithic site of Vinča (ca. 5600–4500 BC) in Serbia. Notwithstanding the limitedness of the data and the complexity surrounding carbon fractionation and the isotopic variation, it is suggested that the differences/similarities in carbon isotope ratios between modern and archaeological Cornelian cherry stones, when measured for much larger assemblages, could potentially offer a glimpse into growing conditions of Cornelian cherry trees in the past.

Subtypes of homicide offenders based on psychopathic traits

The aim of the present study was to explore the subtypes of offenders based on psychopathic traits in a sample of 127 adult homicide offenders (n=40.3% convicted of murder, n=32.6% convicted of aggravated murder, n=27.1% convicted of attempted murder). A two-step cluster analysis of the four factors of psychopathy yielded three clusters, which were then compared on the general dimensions of personality defined by the HEXACO model, intelligence, sadism and psychopathology variables conceptualized by the MMPI-202. Cluster 1 was characterized by moderate scores on psychopathy factors, Agreeableness and aggressiveness. Cluster 2 was a psychopathic-like group with the highest scores on psychopathy factors, sadism, aggressiveness and paranoia, and with the lowest scores on Emotionality and Agreeableness. Cluster 3 was a non-psychopathic group with the lowest scores on psychopathy factors and aggressiveness, and with the highest scores on Agreeableness and Honesty-Humility. There were no significant differences between the clusters on intelligence, Openness to experience, Extraversion, Conscientiousness, and a number of psychopathological variables, including depression and anxiety. Present findings did not provide support for the distinction between primary and secondary psychopathy. The current study further contributes to the person-oriented research of psychopathy by emphasizing the differences between the individuals with high, moderate and low psychopathic traits.