Efficiencies of Different Methods for Determination of Organophosphate Pesticide Residues in Fermented Wheat Substrate
Efikasnost različitih metoda za određivanje ostataka organofosfata u fermentisanim uzorcima žita
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Author
Djordjevic, Tijana
Siler-Marinkovic, Slavica
Djurovic-Pejcev, Rada
Dimitrijevic-Brankovic, Suzana
Gajic Umiljendic, Jelena
Keywords
Method efficiencyPesticide determination
Pirimiphos-methyl
Chlorpyrifosmethyl
Fermented wheat
Efikasnost metode
određivanje pesticida
pirimifos-metil
hlorpirifos-metil
fermentisana pšenica
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Show full item recordAbstract
In the present work, the efficiencies of three different sample preparation methods for GC/
MS determination of pirimiphos-methyl and chlorpyrifos-methyl residues in wheat (Triticum
spelta) samples fermented by Lactobacillus plantarum were compared. All three methods were
based on methanol:acetone=1:1 extraction, while further purification of the obtained samples
was altered. First purification was through a column containing a mixture of aluminium
oxide and activated charcoal slurry-packed and eluted with dichlormethane, the second was
purification on a florisil column slurry-packed and eluted with ethyl acetate:acetone=4:1, while
the third was based on a combination of the former two methods, i.e. clean-up through columns
filled with a mixture of aluminum oxide and activated charcoal slurry-packed and eluted
with ethyl acetate:acetone=4:1. The second method was found the most effective for obtaining
satisfactory recoveries at four fortification levels. For pirimiphos-methyl, recoveries were
in the range of 91.3-96.0% and had good reproducibility, i.e. RSD ranging from 2.2-4.1%, while
the corresponding range for chlorpyrifos-methyl was 81.6-88.2%, and the RSD range 2.5-5.4%.
The chosen method was further optimized in order to establish the optimum volume of elution
solvent used during the clean-up procedures. The highest recoveries of 93.7±3.5% for pirimiphos-
methyl and 85.3±2.5% for chlorpyrifos-methyl were obtained after elution with 25 ml
volume of solvent. Considering all, simple, efficient and reliable GC/MS detection of pirimiphosmethyl
and chlorpyrifos-methyl residues in wheat grain substrate altered by fermentation with
L. plantarum was achieved by the two-steps extraction with 25 ml of methanol:acetone=1:1
solvent mix for 30 min, followed by a clean-up procedure through a glass column with florisil
coupled with elution by 25 ml of ethyl acetate:acetone=4:1. Poređene su efikasnosti tri različite metode pripreme uzoraka za određivanje ostataka
pirimifos-metila i hlorpirifos-metila u uzorcima pšenice (Triticum spelta) fermentisane sa Lactobacillus
plantarum. Sve tri metode zasnivale su se na metanolsko-acetonskoj (1:1) ekstrakciji
dok su se procedure prečišćavanja dobijenih ekstrakata razlikovale. Prva metoda bila je
prečišćavanje kroz kolonu punjenu smešom aluminijum-oksida i aktivnog uglja u kombinaciji
sa dihlormetanom kao eluentom, druga prečišćavanje kroz kolonu punjenu florisilom u
kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom, dok se treća zasnivala na
kombinaciji prve dve, tj. prečišćavanju kroz kolonu punjenu smešom aluminijum-oksida i
aktivnog uglja u kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom.
Druga testirana metoda pokazala se kao najefikasnija, pri čemu su dobijeni prinosi
pirimifos-metila u opsegu 91,3-96,0% za četiri koncentraciona nivoa obogaćivanja, sa
RSD% u opsegu 2,2-4,1%, dok su za hlorpirifos-metil ovi prinosi bili u opsegu 81,6-88,2%
sa RSD% u opsegu 2,5-5,4%. Odabrana metoda je dodatno optimizovana variranjem različitih
zapremina korišćenog eluenta. Najveći prinos metode za oba ispitivana pesticida
postignut je pri zapremini eluenta od 25 ml (93,7±3.5% za pirimifos-metil i 85,3±2,5% za
hlorpirifos-metil). Predložena metoda, bazirana na 30-minutnoj ekstrakciji sa 25 ml smeše
metanol:aceton=1:1, prečišćavanju na florisilskoj koloni i eluiranju sa 25 ml smeše etilacetat:
aceton=4:1, pokazala se kao efikasna, jednostavna i pouzdana metoda za određivanje
ostataka ispitivanih organofosfata u fermentisanom žitnom supstratu.