Papers by Gordana Mendaš
Environmental Science and Pollution Research, Jun 22, 2016
Arhiv Za Higijenu Rada I Toksikologiju, 2016
Pesticides are a major group of chemicals produced to be intentionally released in the environmen... more Pesticides are a major group of chemicals produced to be intentionally released in the environment. Many pesticides are not easily degradable ; they persist in soil, leach to groundwater and surface water and contaminate the wider environment. Depending on their chemical properties they can enter organisms, bioaccumulate in food chains and consequently influence human health. There is much data available concerning acute exposure of people or laboratory animals to pesticides. However, long-term exposure to low concentrations corresponding to real-life scenarios is much less investigated. Exposure to triazine herbicides such as terbuthylazine mainly results in urinary excretion of the parent compound and its metabolites formed by dealkylation. The aim of this study was to determine mass concentrations of terbuthylazine and its metabolites in rat urine. Animals were exposed to three different concentrations of terbuthylazineon each of 28 consecutive days. Terbuthylazine and its metabolites were determined in a 24-hour urine sample collected on the 1st, 14th and 28th day of treatment, with the results serving to define the markers and biomarkers of exposure. Different extraction procedures were developed for determining the accumulation of triazine herbicide terbuthylazine and dealkylated metabolites in rat urine: extraction with ethyl-acetate and solid-phase extraction on styrene-divinylbenzene sorbent. These procedures were optimised for final analysis by high performance liquid chromatography. Mass concentration of terbuthylazine recovered from urine indicates that unchanged terbuthylazine represents only a minor part of the adsorbed dose while the majority of terbuthylazine was excreted as dealkylated metabolites. This work has been supported in full by the Croatian Science Foundation under project no. 8366.
The vertical distribution of terbuthylazine and its metabolite deethylterbuthylazine was evaluate... more The vertical distribution of terbuthylazine and its metabolite deethylterbuthylazine was evaluated in four layers of a silty loam agricultural soil during a five-month period of corn cultivation. The experimental field plots were treated pre-emergence with a suspension of terbuthylazine formulation Radazin TZ-50 at a regular (1.5 kg/ha) and a double-regular rate. The soil samples were collected every 7 to 20 days at depths of 0 to 10 cm, 10 to 20 cm, 20 to 30 cm and 30 to 50 cm. Herbicide residues were extracted from wet soil samples with methanol using a microwave-assisted extraction procedure and then analysed by liquid chromatography with UV diode-array detection. In the first three months after herbicide application the loss of terbuthylazine from the surface soil (0-10 cm) was significantly affected by the soil moisture content. Seven days after application at regular and double-regular rate 56 % and 70 %, respectively, of the initial terbuthylazine amount dissipated from the first 50 cm of soil. Five months later, at the time of corn harvest, the total loss of terbuthylazine from soil was 96 % at both application rates. The dissipation rate of terbuthylazine was higher in upper soil layers and correlated significantly with the higher soil organic carbon content. Terbuthylazine dissipation was also favoured by the higher herbicide application rate.
The benzoylcyclohexanedione (triketone) herbicides mesotrione and tembotrione and benzoylpyrazole... more The benzoylcyclohexanedione (triketone) herbicides mesotrione and tembotrione and benzoylpyrazole herbicide topramezone have recently been released for commercial use in corn production. The objective of this study was to develop and validate a new method for the simultaneous extraction of mesotrione with its two degradation products 4-methylsulfonyl- 2-nitrobenzoic acid (MNBA) and 2-amino-4- methylsulfonyl-benzoic acid (AMBA), tembotrione and topramezone from agricultural soil. Our analytical method is based on microwave- assisted extraction (MAE) followed by reversed- phase liquid chromatography, using gradient elution with acetonitrile and acidified water (pH 2.2) and diode array detection at 205 and 220 nm. MAE operational parameters (solvent type and volume, extraction temperature and time) were optimized with respect to the extraction efficiency of the target compounds from dry soils fortified at 0.2 and 0.1 mg kg- 1. The highest recoveries (70-94 % for herbicides and MNBA and <30 % for AMBA), with satisfactory method precision (RSD ≤20 %), were achieved by extraction of soil with solvent mixture ψ (methanol, 0.1 mol L-1 HCl) = 9:1 at 60 °C for 5 min. The method has proven suitable for residue analysis of target herbicides and MNBA in neutral, low humic silt loam soils, with an analyte detection limit of 0.002 mg kg- 1 of soil dry mass.
Integrated weed management practices and weed’s growing resistance against herbicides applied lon... more Integrated weed management practices and weed’s growing resistance against herbicides applied long-term introduced two new classes of herbicides onto the crop protection market in the 2000s. Triketone (mesotrione and tembotrione) and pyrazolone (topramezone) herbicides are considered efficient ecological substitutes for the recently restricted triazine herbicides, due to their chemical structure derived from a natural phytotoxin of certain plants belonging to the myrtle family. Since triketone and pyrazolone herbicides are more water soluble and mobile compounds than triazines, it is necessary to compare the behaviour of these three herbicide classes in agricultural soil under realistic environmental conditions. The present study investigated the persistence of mesotrione, tembotrione and topramezone in corn-cultivated soil after their post-emergence application at a registered and double-registered rate. The biodegradation rate and sorption intensity of herbicides in the same agricultural soil were evaluated under laboratory conditions. The calculation of herbicide leaching potential indices under the studied environmental conditions included kinetic and mobility parameters, as well as pedological and meteorological data. The conditions of microwave-assisted extraction and chromatographic determination were optimised for herbicide analyses in wet soil samples. The results showed faster field dissipation, slower biodegradation rate and higher soil mobility of topramezone compared to triketones. The biodegradation rate of herbicides in topsoil was slower at an enhanced application rate. Although the leaching potential index of topramezone in neutral silty loam soil with 1.2 % of organic carbon content was low, it was at least five times higher compared to the leachability class of triketones. Acknowledgement: this study was supported in part by the Croatian Science Foundation (No. 8366) and The Foundation of the Croatian Academy of Sciences and Arts (No. 10-102/284-2- 2015).
Food and Chemical Toxicology
Arhiv Za Higijenu Rada I Toksikologiju, Dec 20, 2017
Journal of Chromatography A, May 1, 2001
A solid-phase extraction (SPE) procedure on a styrene-divinylbenzene (SDB-1 cartridge) for extrac... more A solid-phase extraction (SPE) procedure on a styrene-divinylbenzene (SDB-1 cartridge) for extraction and cleaning of the triazine herbicides atrazine, simazine, ametryn, and prometryn and atrazine monodealkylated metabolites from urine samples was developed and optimised for final high-performance liquid chromatographic (HPLC-UV diode array detection) and gas chromatographic (GC-electron-capture detection and GC-thermionic-sensitive detection) analyses. Interfering polar matrices were eliminated by rinsing SDB-1 with 1% acetonitrile in water or with pure water. Extraction recoveries were from 78 to 101% with an RSD of about 10% for all studied compounds. The extraction recovery for the didealkylated atrazine metabolite was significantly lower and this compound cannot be determined with these procedures. Sorbent matrix generated interferences, although not detected by the chromatographic system, lowered the response of nitrogen-phosphorus and electron-capture GC detectors for monodealkylated chlorotriazines when compared to standards prepared in n-hexane. HPLC and GC analysis with SPE (SDB-1) preconcentration showed excellent linearity over the concentration range tested, with detection limits in urine of 10 ng ml(-1) for the parent herbicides (HPLC and GC analysis) and 20 ng ml(-1) for monodealkylated chlorotriazines (HPLC analysis).
Environmental Geochemistry and Health
Toxics
Persistent organic pollutants (POPs) are a group of 28 toxic compounds of different chemical clas... more Persistent organic pollutants (POPs) are a group of 28 toxic compounds of different chemical classes listed in the Stockholm Convention on POPs, which aims to protect the environment and human health [...]
Tembotrione is one of the most recently introduced herbicides in the triketone group and has been... more Tembotrione is one of the most recently introduced herbicides in the triketone group and has been in application in Europe since 2007. The aim of this study was to develop and validate a method for extraction and determination of tembotrione from rat urine. The extraction procedure was based on forcing the 5 mL acidified urine samples (pH 2) through the Oasis HLB sorbent and the extracts were analysed using high performance liquid chromatography - tandem mass spectrometry (LC-MS QQQ system).
The benzoylcyclohexanedione (triketone) herbicides mesotrione and tembotrione and benzoylpyrazole... more The benzoylcyclohexanedione (triketone) herbicides mesotrione and tembotrione and benzoylpyrazole herbicide topramezone have recently been released for commercial use in corn production. The objective of this study was to develop and validate a new method for the simultaneous extraction of mesotrione with its two degradation products 4-methylsulfonyl- 2-nitrobenzoic acid (MNBA) and 2-amino-4- methylsulfonyl-benzoic acid (AMBA), tembotrione and topramezone from agricultural soil. Our analytical method is based on microwave- assisted extraction (MAE) followed by reversed- phase liquid chromatography, using gradient elution with acetonitrile and acidified water (pH 2.2) and diode array detection at 205 and 220 nm. MAE operational parameters (solvent type and volume, extraction temperature and time) were optimized with respect to the extraction efficiency of the target compounds from dry soils fortified at 0.2 and 0.1 mg kg- 1. The highest recoveries (70-94 % for herbicides and MNBA and...
Flavonoidi su skupina polifenolnih spojeva koji se nalaze u mnogim biljkama, a imaju antioksidati... more Flavonoidi su skupina polifenolnih spojeva koji se nalaze u mnogim biljkama, a imaju antioksidativno djelovanje, stite stanice naseg tijela od djelovanja slobodnih radikala, pa tako i od kronicnih bolesti. Hrana pa tako i jabuke predstavljaju kompleksan medij pa je prisutne polifenolne spojeve potrebno djelotvorno razdvojiti ne samo međusobno nego i od ostalih sastojaka matrice i sto selektivnije i osjetljivije detektirati. Tekucinska kromatografija visoke djelotvornosti uz detekciju UV detektorom (HPLC-UV) je jedna od najcesce koristenih analitickih metoda za analizu flavonoida u kompleksnim smjesama. Cilj istraživanja bio je razraditi i validirati metodu ekstrakcije polifenolnih spojeva iz jabucnog soka te optimirati pripravu uzorka za zavrsno HPLC-UV određivanje. Polifenolni spojevi ekstrahirani su iz jabucnog soka s deietil eterom, ekstrakti su upareni do suha u struji dusika i prije zavrsne HPLC analize otopljeni u smjesi metanol/deionizirana voda. Razrada analitickog postupka ...
Organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) are widespread, highly persis... more Organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) are widespread, highly persistent, and hydrophobic environmental pollutants. They strongly bind to soil/sediment particles, which then may become secondary sources of environmental pollution and animal and human exposure. We studied the occurrence and mass fractions of OC pesticides and PCBs in 16 surface soils collected at four sites within the protected area of the Plitvice Lakes National Park and 16 soils collected at urban and suburban sites of the city of Varaždin. The soils were analysed for 15 pesticides [hexachlorobenzene (HCB), hexachlorocyclohexane isomers (α-, β-, and γ- HCH), DDT-type compounds (4, 4’-DDT, 4, 4’-DDE, 4, 4’-DDD, 2, 4’-DDT), aldrin, dieldrin, endrin, isodrin, heptachlor, heptachlor epoxide, α-endosulfan] and 17 PCBs including seven indicator congeners (no. 28, 52, 101, 118, 138, 153, 180). The air-dried samples were extracted with 1:1 acetone:n-hexane mixture using a microwave-assisted ext...
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Papers by Gordana Mendaš