Loading...

Development and Application of Multivariate Calibration Methods Combined with Gas Chromatography for Simultaneous Determination of Organophosphorous Pesticides in Complex Matrices

Balsini, Parvaneh | 2019

724 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51953 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Parastar Shahri, Hadi
  7. Abstract:
  8. In this study, a new strategy based on chemometrics and extraction method of Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) combined with dispersive liquid–liquid micro-extraction (DLLME) in addition gas chromatography-flame ion detector (GC-FID) has been developed for the determination of ten pesticides in complex samples (such as tap water and milk).In this regard, experiments were designed, modeled and optimum condition was achieved by using central composite design (CCD), backward multiple linear regression (MLR) and Nelder-Mead simplex optimization. On this matter, 36 experiments for 5 extraction factors in 5 levels were generated. Also, multi-response optimization using Derringer desirability function was used to combine individual models of 10 pesticides and global optimum conditions were obtained which were 0.25 mL of acetonitrile (disperser solvent), 43 µL of chloroform (extraction solvent), 3.81% (w/v) salt in pH 6.1and 25 min of sonication time.After optimization of extraction procedure and obtaining every 10 chromatograms, the calibration step was developed using in range 0.5- 100 ngmL-1. Initially, a common strategy for zero order calibration (univariate calibration with linear model) has applied. After obtaining the calibration curve for all of the pesticides has been observed some of the pesticides didn't behave linearly and they follow quadratic regression. Since in previous works, there are few reports about quadratic regression, in the second part of this study has been discussed specifically quadratic regression. In this regard, Mandel's test for evaluating linearity and types of calibration and also analytical figures of merit including calibration sensitivity, analytical sensitivity, detection limit and error (systematic and random) have been developed. Finally, 4 of them including Carbaryl, Ametryne, Pirimiphos methyl and Prothioconazole follow behave linear and also 6 of them including Dichlorvos, Carbofuran, Atrazine, Diazinon, Chlorpyrifos and Tebuconazole follow behave quadratic. The figures of merit for them have been calculated and were follow range: SENcal 0.18-0.93 (mLng-1), SENanal 0.2-0.86, R2 0.944-0.99, LOD (ngmL-1) 1.81-8.71. The calculated LODs were below the MRLs of 10 pesticides which confirm the validity of the proposed method. Finally, the proposed analytical method was used to identify and determine the amount of 10 pesticides in real samples (tap water and milk). As instance, milk with spiked pesticides in 100 ngmL-1, the relative error was in the range of 1.56-26.96 and the relative standard deviation was in the range of 1.65-4.11
  9. Keywords:
  10. Pesticide ; Gas Chromatography ; Central Composite Design ; Quadratic Calibration ; Dispersive Liquid-Liquid Microextraction ; Chemometrics Method

 Digital Object List

 Bookmark

No TOC