Pavle Jovanov

Multi-residue method for determination of selected neonicotinoid insecticides in honey using optimized dispersive liquid–liquid microextraction combined with liquid chromatography-tandem mass spectrometry

The objective of this study was to develop analytical method based on optimized dispersive liquid-liquid microextraction (DLLME) as a pretreatment procedure combined with reversed phase liquid chromatographic separation on C18 column and isocratic elution for simultaneous MS/MS determination of selected neonicotinoid insecticides in honey. The LC-MS/MS parameters were optimized to unequivocally provide good chromatographic separation, low detection (LOD, 0.5-1.0 μg kg(-1)) and quantification (LOQ, 1.5-2.5 μg kg(-1)) limits for acetamiprid, clothianidin, thiamethoxam, imidacloprid, dinotefuran, thiacloprid and nitenpyram in honey samples. Using different types (chloroform, dichloromethane) and volumes of extraction (0.5-3.0 mL) and dispersive (acetonitrile; 0.0-1.0 mL) solvent and by mathematical modeling it was possible to establish the optimal sample preparation procedure. Matrix-matched calibration and blank honey sample spiked in the concentration range of LOQ-100.0 μg kg(-1) were used to compensate the matrix effect and to fulfill the requirements of SANCO/12495/2011 for the accuracy (R 74.3-113.9%) and precision (expressed in terms of repeatability (RSD 2.74-11.8%) and within-laboratory reproducibility (RSDs 6.64-16.2%)) of the proposed method. The rapid (retention times 1.5-9.9 min), sensitive and low solvent consumption procedure described in this work provides reliable, simultaneous, and quantitative method applicable for the routine laboratory analysis of seven neonicotinoid residues in real honey samples.

Dissipation rate of acetamiprid in sweet cherries

Degradation of acetamiprid in sweet cherry samples was evaluated at several intervals from the product application until the end of the pre-harvest interval. An orchard of sweet cherries located at Stepanovicevo village near Novi Sad was used in this study. Acetamiprid was applied according to the manufacturer’s recommendation for protecting sweet cherries from their most important pests. Sweet cherry fruit samples were collected at eight intervals: immediately after acetamiprid application and 2, 4, 6, 8, 10, 12 and 14 days after application. The extraction of acetamiprid from sweet cherry samples was performed using a QuEChERS-based method. Determination was carried out using an HPLC-UV diode array detection system (Agilent 1100, United States) with an Agilent Zorbax Eclipse C18 column (50 mm C 4.6 mm internal diameter, 1.8 μm particle size). The method was subjected to a thorough validation procedure. The recovery data were obtained by spiking blank sweet cherry samples at three concentration levels (0.1-0.3 mg/ kg), yielding 85.4% average recovery. Precision values expressed as relative standard deviation (RSD) were below 1.61% for the intraday precision. Acetamiprid showed linear calibrations from 0.05 to 2.5 μg/ml with correlation coefficient (R2) of 0.995%. The limit of detection and limit of quantification were found to be 5 μg/kg and 14 μg/kg, respectively. The validated method was applied in the analysis of acetamiprid in sweet cherry samples. During the study period, the concentration of acetamiprid decreased from 0.529 mg/kg to 0.111 mg/kg. The content of acetamiprid in sweet cherry samples at the end of the pre-harvest interval was below the maximum permissible level specified by the Serbian and EU MRLs. [Projekat Ministarstva nauke Republike Srbije, br. TR31038: Development of chemical methods for analysis of the insecticide acetamiprid]

Comprehensive QSRR modeling as a starting point in characterization and further development of anticancer drugs based on 17α-picolyl and 17(E)-picolinylidene androstane structures

The selection of the most promising anticancer compounds from the pool of the huge number of synthesized molecules is a quite complex task. There are many compounds characterization approaches which can suggest the best structural features of a molecule with the highest antiproliferative effect on the certain type of cancer cell lines. One of these approaches is the lipophilicity determination of compounds and the analysis of its correlation with the anticancer activity. Since the importance of the lipophilicity is underlined in many earlier studies, this study is focused on determination of lipophilicity of previously synthesized 17α-picolyl and 17(E)-picolinylidene androstane derivatives by using reversed-phase high performance liquid chromatography (RP-HPLC) as a very fast, effective and relatively cheap method. Determination of the chromatographic lipophilicity of the studied androstanes can be considered as the part of their physicochemical characterization, which is a very important step in their further selection as drug candidates. The present study does not neglect the in silico approach. The determined chromatographic lipophilicity was analyzed by quantitative structure-retention relationship (QSRR) approach in order to reveal which molecular characteristics contribute mostly to the typical behavior of the androstanes in the applied chromatographic system, and thus to their lipophilicity. Classical statistical approach and Sum of Ranking Differences method were used for selection of the best QSRR models which should be used in prediction of chromatographic lipophilicity of studied androstane derivatives.

Physicochemical properties and mineral content of honey samples from Vojvodina (Republic of Serbia)

Forty-five honey samples of three honey types - two monofloral (acacia and sunflower) and one polyfloral (meadow) were collected from the Autonomous Province of Vojvodina (Republic of Serbia) and analysed for their physicochemical parameters (moisture, acidity, pH, ash, electrical conductivity, glucose, fructose, hydroxymethylfurfural (HMF), CIE L∗a∗b∗ colour and mineral content). All tested physicochemical parameters were in agreement with the EU regulation except for moisture (4 samples) and HMF content (1 sample). Principal component analysis (PCA) was used for assessing the effects of three honey types on all investigated physicochemical parameters. According to PCA, acacia honey samples can be clearly isolated and form a cluster, while, regarding other honey types, PCA can offer the possibility to distinguish sunflower and meadow honey samples regarding examined physicochemical parameters and mineral content.

Aflatoxins in maize harvested in the Republic of Serbia over the period 2012–2016

ABSTRACT Aflatoxins (AFs) are one of the most frequent contaminants in maize. The Republic of Serbia represents a leader in terms of maize production and exports in Europe. In recent years, Serbia faced climate changes. Therefore, the main objective of this study was to examine AF occurrence in 3000 maize samples collected during 2012–2016. In maize samples from 2012, 2013, 2015, and 2016, AFs were detected in 72.3%, 24.7%, 36.7%, and 5.0% of the samples, in concentration ranges of 1.0–111.2, 1.2–65.2, 1.1–76.2, and 1.3–6.9 µg kg−1, respectively. Contrary to this, in maize samples from 2014, no AFs were detected. Analysis of weather conditions indicates that 2012 was characterised by extreme drought conditions, 2013 and 2015 by lack of precipitation and high air temperatures, 2014 as the rainiest year in these years, while 2016 had moderate weather conditions.

Hydrophilic interaction chromatography coupled to tandem mass spectrometry as a method for simultaneous determination of guanidinoacetate and creatine

The biosynthesis of creatine (Cr) is closely related to the bioavailability of guanidinoacetate (GAA). The lack of one or the other may compromise their role in the energy transport and cell signaling. A reliable estimate of their levels in biological samples is imperative since they are important markers of many metabolic disorders. Therefore, a new LC-MS/MS method for simultaneous determination and quantification of GAA and Cr by multiple reaction monitoring (MRM) mode was developed based on the hydrophilic interaction chromatography (HILIC) and response surface methodology (RSM) for the optimization of chromatographic parameters. The optimized parameters ensured good separation of these similar, very polar molecules (chromatographic resolution > 1.5) without prior derivatization step in a short analysis run (6 min). The developed method was validated to ensure accurate (R, 75.1-101.6%), precise (RSD < 20%) and low quantification (LOQ of 0.025 μg mL-1 for GAA and 0.006 μg mL-1 for Cr) of the tested analytes and the use of matrix-matched calibration eliminated variable effects of complex matrices such as human plasma and urine. Therefore, this method can be implemented in medical laboratories as a tool for the diagnostics of creatine deficiencies and monitoring of guanidinoacetate and creatine supplementation regimes in biological samples.

Differential influence of vitamin C on the peripheral and cerebral circulation after diving and exposure to hyperoxia

We examined if the diving-induced vascular changes in the peripheral and cerebral circulation could be prevented by oral antioxidant supplementation. Fourteen divers performed a single scuba dive to eighteen meter sea water for 47 min. Twelve of the divers participated in a follow-up study involving breathing 60% of oxygen at ambient pressure for 47 min. Before both studies, participants ingested vitamin C (2 g/day) or a placebo capsule for 6 days. After a 2-wk washout, the study was repeated with the different condition. Endothelium-dependent vasodilator function of the brachial artery was assessed pre- and postintervention using the flow-mediated dilation (FMD) technique. Transcranial Doppler ultrasound was used to measure intracranial blood velocities pre- and 90 min postintervention. FMD was reduced by ∼32.8% and ∼21.2% postdive in the placebo and vitamin C trial and posthyperoxic condition in the placebo trial by ∼28.2% ( P < 0.05). This reduction in FMD was attenuated by ∼10% following vitamin C supplementation in the hyperoxic study ( P > 0.05). Elevations in intracranial blood velocities 30 min after surfacing from diving were reduced in the vitamin C study compared with the placebo trial ( P < 0.05). O2 breathing had no postintervention effects on intracranial velocities ( P > 0.05). Prophylactic ingestion of vitamin C effectively abrogated peripheral vascular dysfunction following exposure to 60% O2 but did not abolish the postdive decrease in FMD. Transient elevations of intracranial velocities postdive were reduced by vitamin C. These findings highlight the differential influence of vitamin C on peripheral and cerebral circulations following scuba diving, which are only partly mediated via hyperoxia.

Buckwheat-enriched wheat bread: National market placement possibilities

Quality parameters and the possibility of successful placement of buckwheat-enriched wheat bread on the national market are presented in this paper. Analysis of the market position of buckwheat-enriched wheat bread includes demands, offer and competition. Elements that affect the overall retail price of buckwheat-enriched wheat bread are given in details, along with SWOT analysis and marketing plan including target market, market supply and product marketing mix. According to all performed analyses it could be concluded that this product should be positioned on the national market, especially for people with special needs and requirements.

Optimization of the quantity of protein components in the high-protein instant porridge

Different types of instant porridges have become a popular choice for breakfast, and it is known that breakfast is an important meal for daily appetite control. On our market there is porridge of uniform composition based on cereals, primarily oats. However, high-protein porridge is not available, which is a significant deficiency in the assortment of these products. In addition, insufficient intake of quality protein remains a dietary problem, particularly among children and the elderly, where diets consist mainly of cereals. Plant proteins in combination with cereals could be used to produce high protein instant porridge. In this study, proteins from legumes such as soybean and pea, specifically soy protein concentrate, soy protein isolate, and pea protein isolate were applied. Protein preparations were added to the main mixture composed of the buckwheat and corn extrudate and other additional ingredients. The protein preparations were added at three different levels: soy protein concentrate at 0, 7.5 and 15% (w/w main mixture basis) and soy protein isolate and pea protein isolate at 0, 15 and 30% (w/w main mixture bases), with the objective of optimizing the composition of the high-protein instant porridge. The aim of optimization was to maximize the protein content and overall acceptability. The optimal doses of protein preparations were determined using the method of desirability function and it was found that the optimized dose for the soy protein concentrate was 1.43 g/100 g, soy protein isolate 21.07 g/100 g and pea protein isolate 14.83 g/100 g. The prediction value for protein content was 24.77 %/DM and overall acceptability 4.09. The obtained experimental values were close to the prediction values: 24.32 %/DM for protein content and 4.41 for overall acceptability. The protein content of the formulated porridge was 24.32 %/DM, which is more than twice as high as that in the oat porridge present on the market. Based on standard nutritional values, the newly formulated high-protein instant porridge could be recommended as appropriate breakfast meal for adults.