SUMMARYThe effect of organic matter and clay content on the adsorption of atrazine, acetochlor, clomazone, pendimethalin and oxyfluorfen in soil samples was studied. In order to determine whether and to what degree different soil properties affect the process of determination of selected pesticides, three soils with different clay and organic matter contents were used.An optimized liquid-solid extraction procedure followed by SPME measurement was applied to analyse the selected pesticides in soil samples. Detection and quantification were done by gas chromatography-mass spectrometry (GC/MS). Relative standard deviation (RSD) values for multiple analyses of soil samples fortified at 30 µg/kg of each pesticide were below 19%. Limits of detection (LODs) for all compounds studied were less than 2 µg/ kg. The results indicate that soils with different physico-chemical properties have different effects on the adsorption of most pesticides, especially at higher concentration levels.
SuMMARyA multiresidue method for simultaneous determination of four pesticides (diazinon, acetochlor, aldrine and carbofuran) belonging to different pesticide groups, extracted from soil samples, is described. The method presented is based on liquid-solid extraction (LSE) and determination of pesticides, i.e. the pesticides were extracted by methanol-acetone mixture, purified on florisil column and eluted by ethyl acetate-acetone mixture. Optimization of the main parameters affecting the LSE procedure, such as the choice of purification sorbent, as well as the elution solvent and its volume, were investigated in details and optimized. Also, validation of the proposed method was done.Gas chromatography-mass spectrometry (GC-MS) was used for detection and quantification of the pesticides studied. Relative standard deviation (RSD) and recovery values for multiple analysis of soil samples fortified with 30 μg/kg of each pesticide were below 8% and higher than 89%, respectively. Limits of detection (LOD) for all the compounds studied were less than 4 μg/kg.
The structures of bright zinc coatings obtained from acid sulfate solutions in the presence of dextrin/salicyl aldehyde mixture were examined. It was shown by the STM technique that the surfaces of bright zinc coatings are covered by hexagonal zinc crystals, the tops of planes of which are flat and mutually parallel and which exhibit smoothness on the atomic level. X-Ray diffraction (XRD) analysis of the bright zinc coatings showed that the zinc crystallites are oriented in the (110) plane only.
REZIMEPesticidi su neizostavni deo životne sredine, jer se usled intenzivne primene njihovi ostaci često detektuju u prirodi, naročito u zemljištu. Bez obzira na koji način dospeju u zemljište, njihova dalja sudbina će zavisiti od mnoštva faktora. Uzimajući u obzir složenost interakcija pesticida i zemljišta, kao i činjenicu da je intenzitet interakcija istog jedinjenja sa različitim zemljištima različit, sve su brojnija ispitivanja uticaja najvažnijih zemljišnih parametara u pomenutim interakcijama.U ovom radu su predstavljeni procesi koji određuju sudbinu pesticida u zemljištu, kao i faktori koji utiču na te procese. Poseban osvrt je stavljen na adsorpcione procese, s obzirom da oni određuju koncentraciju slobodne frakcije molekula pesticida, tj. količine pesticida koja može da učestvuje u detoksifikacionim procesima u koje spadaju procesi degradacije i kretanja. UVODPesticidi, koji predstavljaju veoma značajnu grupu agrohemikalija, pored koristi, donose sa sobom i neke neželjene posledice. U sagledavanju ovih štetnih efekata, centralno mesto zauzima opasnost od zagađenja ži-votne sredine (Đurović i Đorđević, 2010a; 2010b; Marković i sar., 2010).Pod sudbinom pesticida u životnoj sredini podrazumevaju se procesi kretanja i transformacije, od kojih su zbog potencijalne dužine trajanja i efekata koje mogu proizvesti, najznačajniji oni koji se dešavaju u zemljištu. Bez obzira da li u zemljište dospevaju direktnom primenom ili na indirektan način, dalja sudbina pesticida u ovom matriksu će zavisiti od međusob-nog dejstva niza složenih fizičko-hemijskih procesa. Ispitivanja u ovoj oblasti imaju za cilj, pre svega, dobijanje podataka koji omogućavaju procenu opasnosti, tj. rizika od primene pesticida. S obzirom da adsorpcioni procesi indirektno određuju i koncentraciju pesticida koja može da učestvuje u procesima degradacije i kretanja, ispitivanja u ovoj oblasti su, pre svega, usmerena na određivanje adsorpcionih konstanti i adsorpciono/desorpcionih izotermi, koje omogućavaju i utvrđivanje fizičko-hemijskih karakteristika zemljišta najodgovornijih za retenciju ispitivanih pesticida u zemljištu, odnosno za njihovo ispiranje po profilu zemljišta.
A new theoretical approach to the headspace/solid phase microextraction (HS/SPME) process is proposed and tested by the analysis of pesticide residues of water samples. The new approach focuses on mass transfer at the sample/gas phase and gas phase/SPME polymer interfaces. The presented model provides a directly proportional relationship between the amount of analytes sorbed by the SPME fiber and their initial concentrations in the sample. Also, the expression indicates that quantification is possible before partition equilibrium is attained. Experimental data for pesticides belonging to various classes of organic compounds were successfully interpreted by the developed model. Additionally, a linear dependence of the amount of pesticide sorbed on the initial analyte concentration in aqueous solution was obtained for a sampling time shorter than that required to reach sorption equilibrium.
SUMMARYA solid phase microextraction (SPME) method for simultaneous determination of atrazine, acetochlor, clomazone, pendimethalin and oxyfluorfen in soil samples was developed. The method is based on a combination of conventional liquid-solid procedure and a following SPME determination of the selected pesticides. Initially, various microextraction conditions, such as the fibre type, desorption temperature and time, extraction time and NaCl content, were investigated and optimized. Then, extraction efficiencies of several solvents (water, hexane, acetonitrile, acetone and methanol) and the optimum number of extraction steps within the sample preparation step were optimized.According to the results obtained in these two sets of experiments, two successive extractions with methanol as the extraction solvent were the optimal sample preparation procedure, while the following conditions were found to be most efficient for SPME measurements: 100 μm PDMS fibre, desorption for 7 min at 270 0 C, 30 min extraction time and 5% NaCl content (w/v).Detection and quantification were done by gas chromatography-mass spectrometry (GC/MS). Relative standard deviation (RSD) values for multiple analysis of soil samples fortified at 30 μg/kg of each pesticide were below 19%. Limits of detection (LOD) for all the compounds studied were less than 2 μg/kg.
REZIMESudbina pesticida u zemljištu zavisi od mnoštva faktora, kao i od zastupljenosti i inteziteta procesa, kao što su adsorpcija, degradacija, isparavanje, ispiranje, spiranje, itd. S obzirom da adsorpcioni procesi regulišu koncentraciju slobodne frakcije molekula pesticida, istraživanja u ovoj oblasti su pre svega usmerena na proučavanje ovog procesa, tačnije na određivanje adsorpcionih konstanti i adsorpciono/desorpcionih izotermi koji omoguća-vaju utvrđivanje karakteristika zemljišta najodgovornijih za zadržavanje ispitivanih pesticida u zemljištu. S obzirom da je od transportnih procesa ispiranje po profilu zemljišta najzastupljenije, i da je njegov intenzitet indirektno određen intenzitetom adsorpcionih procesa, određivanje adsorpcionih konstanti pesticida omogućava i utvrđivanje potencijala ka ispiranju ovih jedinjenja po profilu zemljišta.U ovom radu su predstavljene metode za određivanje adsorpcionih karakteristika pesticida i ispitivanje njihove mobilnosti u zemljištu, pre svega ispiranja po profilu zemljišta. Poseban akcenat je stavljen na "batch" metodu, koja je danas najviše zastupljena, i koja je između ostalog i predložena od strane Organizacije za ekonomsku saradnju i razvoj (OECD). UVODUsled intenzivne primene, pesticidi se danas neretko detektuju u životnoj sredini, a zbog načina primene, najviše u zemljištu (Đurović i Đorđević, 2010a, 2010b; Marković i sar., 2010). Bez obzira na koji način dospeju u zemljište, dalja sudbina pesticida će zavisiti od mnoš-tva faktora, kao što su fizičko-hemijske karakteristike kako samog jedinjenja tako i zemljišta, načina i količine primene, oblika formulacije, stanja terena (nagib, flora i fauna), količine i frekfencije padavina i navodnjavanja, vazdušnog strujanja, temperature, itd. Sudbina pesticida u zemljištu zavisiće i od intenziteta procesa, kao što su isparavanje, adsorpcija, ispiranje, hemijska, fotohemijska, mikrobiološka degradacija, itd. Od pomenutih, adsorpciono/desorpcioni procesi su ključni procesi koji regulišu koncentraciju pesticida u zemljišnom rastvoru, pa samim tim utiču i na mobilnost, degradaciju (pre
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