Comparison of calibration methods in gas chromatographic analysis of pesticide residues

Pesticides are used in agricultural war widely so they represent high toxicity and serious risk for environment and human health due to the transportation with water, air and soil.So, agricultural crops must be monitored intensively with respect to pesticide residues, using sensitive and reliable analytical methods.In the pesticide residue analysis, the matrix effect is the most important problem for the accuracy and reprocubility of the analytical results. So, it is important the choise of the calibration method used.In this thesis, various calibration methods were compared for gas chromatographic analysis of various pesticides in fresh fruit and vagetables. In addition, the combination of standard addition and internal standard methods were examined.First, stock solutions of trichlorfon, mevinphos, ethoprophos, cadusofas, terbusof, formathion, phoshamidon, parathion-ethyl, quinalphos, tetrachlorovinphos, prothiophos, fensulfathion, triazophos, leptophos, azinphos-ethyl pesticide were prepared by dissolving pesticide standards in acetone. Then, working standard solutions were obtained by appropriate dilution. These working standard solutions were injected into gas chromatograph having rtx-5ms column and FPD or MS detectors. Sufficiently high resolution values were obtained under optimum conditions, so a working standard mixture were prepared containing above sixteen pesticides to be used in studies.Studies were performed using calibration methods of pure standard, internal standard, standard addition, and the combination of internal standard and standard addition methods.The result were evaluated with the aid of the validation studies in terms of linearity, repeatability, reproducubility, accuracy and recovery.The results obtained by the above evaluations show that, standart addition calibration method must be applied in the analysis of organic phosphorus pesticides with FP detector and the higher accuracy and reproducibility can be obtained by applying the combination of ?standard addition + internal standard? calibration methods.Keywords: Pesticides, gas chromatography, standard addition, internal standard, validation, methods of extraction, analysis of pesticide residue