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EPSA Students' Science Publication<br />

DETERMINATION OF NITROGEN AND<br />

ORGANOPHOSPHOROUS PESTICIDE RESIDUES<br />

IN FOODS OF PLANT ORIGIN – METHOD<br />

VALIDATION<br />

Radak, Srđan. Medical Faculty, Department of Pharmacy, Novi Sad, Serbia<br />

Combination of QuEChERS method and gas or liquid chromatography with<br />

mass spectrometry has enabled pesticide residue analysis in a wide analytical<br />

range with high selectivity and sensitivity. These analytical tools have become<br />

a mainstay in most laboratories for pesticide monitoring in order to meet global<br />

standards.<br />

The aim of the study consisted in the validation of QuEChERS/GC-MS<br />

method for analysis of selected nitrogen and organophosphorous pesticide<br />

residues and evaluation of measurement uncertainty. The validation study<br />

was conducted on organically grown potato and carrot, fortified with standard<br />

mixture of nitrogen and organophosphorous pesticides, at two concentration<br />

levels, prepared by QuEChERS method and analysed by GC-MS.<br />

The results of the study showed that the limit of quantification for the analytical<br />

method of 10μg/kg reached 63% of target compounds in both examined<br />

matrices, and additional 21% compound in just one. Estimated limit of<br />

quantification of instrumental method was below or at the level of 10μg/kg<br />

for 89% of analytes in both matrices. Matrix-matched calibration curves were<br />

constructed in the range defined by the limit of quantification at lower level<br />

and 500μg/kg as the upper one. At 10μg/kg fortification level, 63% and 76%<br />

of analytes showed acceptable recovery values in potato and carrot matrix,<br />

respectively. At 100μg/kg fortification level, those values were 76% and 74%.<br />

Pesticides with good recovery values were also characterized with good<br />

precision. Evaluation of expanded measurement uncertainty showed that this<br />

parameter was below 50% for all pesticides meeting the validation criteria.<br />

Conclusion: Validation study and evaluation of measurement uncertainty<br />

confirmed the quality of multi residual QuEChERS/GC-MS method for the<br />

analysis of selected nitrogen and organophosphorous pesticides.<br />

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