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Development of Liquid-Phase Microextraction Technique Combined with Gas Chromatography and Chemometric Techniques for Extraction and Determination of Some Pesticides in Saffron

Zarinkhat, Farida | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55933 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Parastar Shahri, Hadi
  7. Abstract:
  8. Today, with increasing concerns about the health of food and its effects on human health, ensuring the quality of food has become a big challenge for regulatory institutions. This issue is more important in the case of foods that have high nutritional and economic value. Among different food items, saffron is especially important due to its low production rate and high economic value. In this research, a new approach based on the diffusion liquid-liquid microextraction method (DLLME) along with gas chromatography-flame ionization detector (GC-FID) combined with chemometrics techniques has been developed to measure the amount of two pesticides in saffron. In this regard, in the extraction stage, experiments were designed and modeled using the methods of experiment design (central composite design (CCD)) and Nelder and Mead simplex optimization and optimal conditions were obtained. Based on that, 32 experiments were designed in 5 levels and for 5 important factors. The area under the chromatographic peaks for each analyte in different conditions were considered as the answer and two separate models were made for two pesticides. finally with the help of the utility function the two models were combined and the final optimal conditions were obtained as follows: 55.3 microliters of Acetonitrile (dispersion solvent), 40 microliters of chloroform (extraction solvent), ionic strength 11.8% w/v NaCl salt, pH 7.7, and 25 minutes for ultrasonication time. After optimizing the extraction conditions, the development stage of the calibration process was carried out in the range of 0.5-100 ng/ml for each analyte and with the help of the partial least square regression (PLSR) method, suitable models were developed for both analytes. then the figures of merit including calibration sensitivity, analytical sensitivity, detection limit, quantitative limit and error size (systematic and random) were developed, which were in the following ranges: Calibration sensitivity 9.60-10.53 ml/ng, analytical sensitivity 4.43-7.37, R2 0.9978-0.9995, detection limit 2.06-2.82 ng/ml. It should be noted that all the calculated detection limits are lower than the permissible limit for each pesticide, which confirms the validity of the proposed method. Finally, the proposed analytical method was used to identify and determine the amount of two pesticides, Ametryn and Chlorpyrifos, in real saffron samples, where, for example, for one saffron sample with an added concentration of 50 ng/ml of pesticides, the relative recovery was in the range of 86.57 -91.82 and the relative standard deviation was in the range of 4.07-4.45
  9. Keywords:
  10. Saffron ; Dispersive Liquid-Liquid Microextraction ; Chemometrics Method ; Gas Chromatography ; Gas Chromatography-flame Ionization Detector ; Liquid Phase Microextraction

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