Vojislava Bursić

Presence of aflatoxins in cereals from Serbia

Aflatoxins (AFs), one of the most toxic and the strongest natural carcinogens can be found in a variety of food commodities, including cereals. For that purpose, the aim of this study was to investigate occurrence of AFs (AFB1, AFG1, AFB2 and AFG2) in 130 cereal samples. AFs content was determined by direct competitive Enzyme Linked Immunosorbent Assay (ELISA) method. Samples with AFs content higher than 1 μg/kg were analyzed again with confirmatory High Performance Liquid Chromatography with fluorescence detection (HPLC-FLD). Analyses showed that none of the analyzed wheat (30), barley (20), oats (20) and rye (20) samples was contaminated with AFs. On the other hand, among 40 analyzed maize samples 24 of them (60%) were contaminated in the following way: 6 (25%) samples had AFs concentration between 1 and 10 μg/kg, 14 (58%) samples between 10 and 50 μg/kg and 4 (17%) between 50 and 70.3 μg/kg. The most predominant aflatoxin was AFB1 which was detected in all contaminated maize samples. AFG1, AFB2 and AFG2 were found in 12, 5 and 1 sample, respectively. This study represents the first investigation of the occurrence of AFs in five different cereals from Serbia.

Whole grain phenolics and antioxidant activity of Triticum cultivars and wild accessions

Total phenolics (TP), total tannins (TT), total flavonoids (TF) and proanthocyanidins (PA) content, as well as the DPPH-radical scavenging capability of the whole grain of 17 different Triticum spp. accessions were analyzed. The content of TP ranged from 976 to 2927 μg catechin/g, while TT ranged from 335 to 1412 μg catechin/g and TF from 0.16 to 1.12 µg/rutin gof dry whole grain. The presence of PA in the whole grains has not been established. The values for DPPH-radical scavenging activity were rather moderate, under 40 % of neutralized radicals. A positive correlation between DPPH-activity and analyzed phenolics was recorded in twelve of seventeen genotypes ( r =0.73-0.99). Trans -cinnamic acid was a major compound among phenolic acids and quercetin among flavonoids found in wheat varieties. The data obtained should enable the selection of the accessions rich in biologically active compounds that could further be processed into functional food with higher nutritive and antioxidant properties.

Development and Validation of Chronopotentiometric Method for Imidacloprid Determination in Pesticide Formulations and River Water Samples

A new electrochemical method for determination of imidacloprid using chronopotentiometry on thin film mercury and glassy carbon electrode was presented. The most important experimental parameters of chronopotentiometry were examined and optimized with respect to imidacloprid analytical signal. Imidacloprid provided well-defined reduction peak in Britton-Robinson buffer on thin film mercury electrode at −1.0 V (versus Ag/AgCl (KCl, 3.5 mol/L)) and on glassy carbon electrode at −1.2 V (versus Ag/AgCl (KCl, 3.5 mol/L)). The reduction time was linearly proportional to concentrations from 0.8 to 30.0 mg/L on thin film mercury electrode and from 7.0 to 70.0 mg/L on glassy carbon electrode. The detection limits were 0.17 mg/L and 0.93 mg/L for thin film mercury and glassy carbon electrode, respectively. The estimation of method precision as a function of repeatability and reproducibility showed relative standard deviations values lower than 3.73%. Recovery values from 97.3 to 98.1% confirmed the accuracy of the proposed method, while the constancy of the transition time with deliberated small changes in the experimental parameters indicated a very good robustness. A minor influence of possible interfering compounds proved good selectivity of the method. Developed method was applied for imidacloprid determination in commercial pesticide formulations and river water samples.

A simple and rapid electrochemical sensing method for metribuzin determination in tap and river water samples

This paper describes an electroanalytical method for the determination of metribuzin using a thin film mercury electrode by chronopotentiometry. Research included optimization of the most important parameters of chronopotentiometric analysis and the best responses were achieved in Britton–Robinson buffer at pH 5.0, using an initial potential of −0.21 V, ending potential of −1.1 V, and reduction current in the range from −4 μA to −15 μA. Under these conditions, metribuzin was reduced in an irreversible electrode reaction process with one well-defined reduction wave at −0.83 V (vs. Ag/AgCl, KCl, 3.5 mol dm−3). A linear response was observed for three concentration ranges 1–5, 5–15 and 15–30 mg dm−3, with an achieved limit of detection of 0.042 mg dm−3. The precision was determined as a function of repeatability and reproducibility, which showed relative standard deviation values not higher than 3.18%. Various interfering substances did not interfere with metribuzin determination. The proposed method was successfully applied to tap and river water samples. The recovery values obtained for spiked river water samples were in good statistical agreement with those obtained by the LC-MS/MS method. Accordingly, the proposed chronopotentiometric methodology can be conveniently applied in the quality control of environmental water samples as a simple, sensitive, reliable and low cost method.

Comparison of QuEChERS with Traditional Sample Preparation Methods in the Determination of Multiclass Pesticides in Soil

Background: The increased use of pesticides leads to permanent pollution of soil, and there is a need for continuous monitoring of these agrochemicals in soil. Objective: Three methods for the simultaneous determination of 12 pesticides belonging to eight chemical groups in soil samples were tested and compared based on analytical parameters. Methods: The quick, easy, cheap, effective, rugged, and safe (QuEChERS); traditional solid-liquid extraction (SLE); and Soxhlet extraction were used for soil sample preparation, while detection and quantification of pesticides were performed using gas chromatography-mass spectrometry (GC-MS). Results: The tested methods featured good sensitivity, and with the exception for carbofuran (Soxhlet method, LOD = 29 μg/kg), for the rest of the pesticides, the studied LODs were less than 12 μg/kg. Except for simazine and carbofuran, LODs obtained by Soxhlet extraction were lower than values obtained by other two methods, whereas QuEChERS gave lower LODs than the traditional SLE method for all compounds except atrazine and acetochlor. The recoveries obtained applying QuEChERS, traditional SLE, and Soxhlet methods for multiple analyses of soil samples fortified at 10, 75, and 200 μg/kg of each pesticide were in the ranges 54-103, 40-91, and 12-92%, respectively. Except for chlorothalonil, the highest recoveries were obtained by the QuEChERS method. Soxhlet was better than traditional SLE method for chlorothalonil, heptachlor, and aldrin; organophosphorus pesticides (fenitrothion and diazinon) and trifluralin, gave similar recoveries for both methods. All three methods were proven to be repeatable, with RSDs lower than 19%. Conclusions: Although all tested methods showed as satisfactory regarding most analytical parameters, QuEChERS method showed much better results in terms of confidence, indicating that traditional SLE and Soxhlet extraction still need improvements for determination of multiclass pesticides in soil samples.

Aflatoxin, zearalenone, deoxynivalenol and fumonisin contamination of maize from the Autonomous Province of Vojvodina

Aflatoxins (AFs), fumonisins (FUMs), zearalenone (ZEA) and deoxynivalenol (DON) have been recognized as major contaminants of maize. Therefore, the presence of AFs, ZEA, DON and FUMs was examined in a total of 100 maize samples from the Autonomous Province of Vojvodina. Sample analyses were performed using the Enzyme Linked Immunisorbent Assay method. The results obtained indicate that 74 % of the maize samples were contaminated with FUMs (540.1-5076 μg/kg), followed by 52 % contaminated with DON (275.2-882.1 μg/kg), 15 % contaminated with ZEA (35.6-183.5 μg/kg) and 5 % contaminated with AFs (2.28-4.31 μg/kg). Although 78 % of the samples were contaminated with at least one mycotoxin, the concentration of FUMs exceed the maximum level (ML) proscribed by the Serbian regulations only in 4 % of the samples. Furthermore, the detected concentrations of AFs, ZEA and DON were in accordance with national regulations. This study is the first research of its kind on the presence of AFs, ZEA, DON and FUMs in maize harvested in the APV in 2016.

Determination of multi-class herbicides in soil by liquid-solid extraction coupled with headspace solid phase microextraction method

A method is described for simultaneous determination of five herbicides (metribuzin, acetochlor, clomazone, oxyfluorfen and dimethenamid) belonging to different pesticides groups in soil samples. Developed headspace solid phase microextraction method (HS-SPME) in combination with liquid-solid sample preparation (LS) was optimized and applied in the analysis of some agricultural samples. Optimization of microextraction conditions, such as temperature, extraction time and sodium chloride (NaCl) content was perfor-med using 100 μm polydimethyl-siloxane (PDMS) fiber. The extraction effi-ciencies of methanol, methanol:acetone=1:1 and methanol:acetone:hexane= =2:2:1 and the optimum number of extraction steps during the sample prepa-ration, were tested, as well. Gas chromatography-mass spectrometry (GC-MS) was used for detection and quantification, obtaining relative standard deviation (RSD) below 13%, and recovery values higher than 83% for multiple analyses of soil samples fortified at 30 μg kg-1 of each herbicide. Limits of detection (LOD) were less than 1.2 μg kg-1 for all the studied herbicides. [Projekat Ministarstva nauke Republike Srbije, br. TR31043 i br. III43005]