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The occurrence and temporal variation of selected priority substances and contaminants of emerging concerns, i.e., eleven perfluorinated compounds (PFCs, belonging to perfluorosulphonates, perfluorocarboxylic acids, and perfluorinated sulphonamides) have been investigated in composite surface water samples of the Danube River at the upstream and downstream locations from the discharge point of wastewater. Among the analyzed compounds, six PFCs (PFOA, PFOS, PFHxA, PFNA, PFDA and PFUnA) were quantified. Overall, the detection frequency for most quantified compounds was very high (>90 %), only PFDA and PFUnA were quantified with less frequency, 33 and 67 %, respectively. The highest quantified concentrations of PFOA and PFOS were 14.9 ng/L (average 12.1 ng/L) and 14.2 ng/L (average 6.11 ng/L), respectively. These ones together with PFHxA (average 10.0 ng/L) were quantified at the highest concentrations in comparison to the other investigated compounds. However, the determined levels of PFOS during investigated sampling period, for all samples analyzed, were always lower than the maximum allowable concentration set for inland river waters but always higher than the environmental quality standard threshold value-AA-EQS of 0.65 ng/L sets by the Directive of European Parliament. Moreover, the levels of PFOA were always several times lower than the set AA-EQS value.

The contents of major ions in bottled waters were analyzed by principal component (PCA) and hierarchical cluster (HCA) analysis in order to investigate if these techniques could provide the information necessary for classifications of the water brands marketed in Serbia. Data on the contents of Ca2+, Mg2+, Na+, K+, Cl-, SO4 2-, HCO3 - and total dissolved solids (TDS) of 33 bottled waters was used as the input data set. The waters were separated into three main clusters according to their levels of TDS, Na+ and HCO3 -; sub-clustering revealed a group of soft waters with the lowest total hardness. Based on the determined chemical parameters, the Serbian waters were further compared with available literature data on bottled waters from some other European countries. To the best of our knowledge, this is the first report applying chemometric classification of bottled waters from different European countries, thereby representing a unique attempt in contrast to previous studies reporting the results primarily on a country-to-country scale. The diverse character of Serbian bottled waters was demonstrated as well as the usefulness of PCA and HCA in the fast classification of the water brands based on their main chemical parameters. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172050]

The purpose of this work is to characterize biodiesel (i.e. methyl esters, MEs) produced from linoleic and oleic sunflower oils (LSO and OSO, respectively) by alkali transesterification with methanol and CaO as a heterogeneous catalyst under different reaction parameters. The parameters investigated were the methanol/oil molar ratio (4.5:1, 6:1, 7.5:1, 9:1 and 12:1) and the mass ratio of CaO to oil (2% and 3%). The physical and chemical properties of the feedstocks and MEs, like density at 15oC, kinematic viscosity at 40oC, acid value, iodine value, saponification value, cetane index, fatty acid (methyl ester) composition, were determined in order to investigate the effects of LSO and OSO properties and reaction parameters on the product characteristics, yields and purity. The properties of feedstock had decisive effect on the physical and chemical properties of MEs as majority of them did not differ significantly under studied reaction conditions. The MEs produced generally met the criteria required for commercial biodiesel; in fact, the only exception was in the case of iodine value of ME produced from LSO. The product yields only slightly changed with the applied conditions; the highest yield (99.22%) was obtained for ME-LSO produced at 6 mol% methanol to oil ratio, while the lowest one (93.20%) was for ME-OSO produced under the lowest methanol/oil molar ratio (4.5:1). The applied catalyst amounts had similar influence on the oil conversion to biodiesel. The yields of ME-LSOs were in general somewhat higher than those obtained for ME-OSOs under the same conditions, which was attributed to the influence of the respective feedstocks' acid value and viscosity.

The effects of the transesterification parameters on the yield and quality of the methyl esters (MEs) produced from waste frying oil (WFO) were investigated. A two-step alkali transesterification reaction followed by silica gel purification step was applied. The investigated reaction parameters were the methanol/oil molar ratio (6:1 and 9:1), the catalyst/oil weight ratio (1.0 and 1.5 mass %) and the type of catalyst (NaOH and KOH). The physical and chemical properties of the employed feedstock and the obtained biodiesel were determined in order to investigate the effects of both the properties of the WFO and the reaction parameters on the characteristics and yields of the product. It was found that the properties of the feedstock had a determinant effect on the physical and chemical properties of the MEs, as the majority of them did not differ significantly under the studied reaction parameters. However, the reaction parameters influenced the yields of the product. Higher yields were obtained with a 1.0 than with a 1.5 mass % catalyst to oil ratio. The increasing yield with decreasing catalyst/oil ratio was more pronounced with NaOH (9.15-14.35 %) than with KOH (2.84-6.45 %). When KOH was used as the catalyst, the yields were always higher (the mean yield was 94.86 %) in comparison to those obtained with NaOH (the mean was 84.28 %). Furthermore, the efficiency of KOH in conversion of WFO to purified MEs in comparison to NaOH was even more pronounced in the case of the higher methanol/oil ratio, i.e., for the 9:1 methanol/ oil ratio, the yield increase with KOH was about 2 times higher than the yield with NaOH, regardless of the applied catalyst/oil ratio.

The presence of polycyclic or polynuclear aromatic hydrocarbons (PAHs) were investigated in sugar-beet from a local sugar factory in the district of Vojvodina. The sugar-beet was cultivated on areas near roads with intensive traffic. The procedure for the preparation and determination of these compounds included saponification of the sample, several liquid–liquid extraction systems and a silica gel column clean-up. The purified sample solution was analysed by thin layer chromatography (TLC) on silica gel with cyclohexane as the developing solvent. Benzo(b)fluoranthene and benzo(a)anthracene and/or benzo(a)pyrene were detected at concentrations greater than the allowed limits in food.

A feed-forward artificial neural network (ANN) model was used to link molecular structures (boiling points, connectivity indices and molecular weights) and retention indices of polycyclic aromatic hydrocarbons (PAHs) in linear temperature- programmed gas chromatography. A randomly taken subset of PAH retention data reported by Lee et al. [Anal. Chem. 51 (1979) 768], containing retention index data for 30 PAHs, was used to make the ANN model. The prediction ability of the trained ANN was tested on unseen data for 18 PAHs from the same article, as well as on the retention data for 7 PAHs experimentally obtained in this work. In addition, two different data sets with known retention indices taken from the literature were analyzed by the same ANN model. It has been shown that the relative accuracy as the degree of agreement between the measured and the predicted retention indices in all testing sets, for most of the studied PAHs, were within the experimental error margins (+-3 %).