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This thesis is concerned with a new class of drugs known as synthetic cathinones, which overruns the drug markets in recent years as “legal highs” drugs, under different commercial names such as bath salts. All synthetic cathinone derivatives consist of a chiral center and usually sold out as a racemic mixture. Usually, one of the two enantiomers will have stronger central nervous system (CNS) stimulatory activity and the other one may have no significant CNS activity or addictive properties. A new sensitive and selective analytical method was developed for the simultaneous determination of ten synthetic cathinones enantiomers in spiked urine samples by gas chromatography coupled with tandem mass spectrometry GCNCI- MS/MS. Multiple reaction monitoring (MRM) mode was used for synthetic cathinones enantiomers identification and quantification in the presence of 3-MMC as an internal standard. The method adopted the indirect chiral separation of the synthetic cathinone enantiomers using methyl chloroformate (MCF) as the chiral derivatizing agent (CDA). Solid-phase extraction (SPE) was used for urine samples clean up followed by derivatization step using MCF prior to gas chromatography analysis. The developed method was validated in terms of linearity, sensitivity, intraday and interday reproducibility, and recovery for all tested spiked urine samples. The method showed linearity and good correlation coefficient (R2) values higher than 0.98 within the tested range of 0.5 to 50 ppm for all synthetic cathinones enantiomers spiked in the urine. The limits of quantitation in urine were 0.012 – 9.536 ppm and for limits of detection was 0.004 – 3.147 ppm. For reproducibility, the mean value of the coefficient of variance was below 12.3%. The mean recovery error was below 12%. The developed method can be used in forensic laboratories for separation and quantitative determination of synthetic cathinones enantiomers in urine samples. The separated and quantified

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