Date of Award

4-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Dr. Mohammed Abdul Ruhman Meetani

Second Advisor

Dr.Soleiman Hisaindee

Third Advisor

Dr. Mahmoud S. A.Bataineh

Abstract

An accurate, rapid and reliable method for the simultaneous determination of 48 pesticide residues in United Arab Emirates imported tea (Green and Black) by liquid and gas chromatography coupled with tandem mass spectrometry LC–ESI (+) - MS/MS and GC-EI-MS/MS. Multiple reaction monitoring (MRM) mode was used in which two transitions for each compound for pesticide identification and quantification in the presence of internal standards. Modified quick, easy, cheap, effective, rugged, safe (QuEChERS) method was used for sample clean up and preparation for chromatographic analysis. The performance of the newly developed analytical method was validated in accordance with EU SANCO guidelines (SANCO/12571/2013) for monitoring pesticide multi-residues by evaluating method linearity, recoveries, precision (reproducibility and repeatability), sensitivity (limits of detection (LODs) and limits of quantification (LOQs)) for each one of the tested pesticides.

LC-MS/MS was used to detect and quantitate 38 pesticides residues. For Black tea, 70% of tested pesticides spiked at levels of 10 and 100 ng.mL-1, the mean recoveries were 99.83% and 94.27%, and average RSD were 14.38% and 13.4 %, respectively. For Green tea, 80% of the tested pesticides spiked at levels of 10 and 100 ng mL-1, the mean recoveries were 93.75% and 95.08, and average RSD was 11.10% and 13.14%, respectively. GCMSMS, used to detect 10 pesticides residues. For Black tea, 70% of tested pesticides spiked at levels of 10 and 100 ng mL-1, the mean recoveries were 85.35% and 78.47%, and average RSD were 10.50% and 8.60%, respectively. For Green tea, 80% of the tested pesticides spiked at levels of 10 and 100 ng mL-1, the mean recoveries were 79.29% and 73.35%, and average RSD were 7.46% and 5.94%, respectively. The limits of detection for all targeted pesticides lower than the respective MRL established by codex and the EU legislations.

Real tea samples of different types and brands were collected from UAE local markets during the time period of 2014-2015and were analyzed in five replicates for each brand. Three green tea brands and five black tea brands in addition to two slimming tea brands were investigated using the validated analytical method.

Buprofezin and Acetamiprid pesticides were found in green tea samples but at lower concentration levels, below the Maximum Residue Levels (MRL) values set by the CODEX and EU. Also, Difenoconazole found in slimming tea at lower concentration levels, below the Maximum Residue Levels (MRL).

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