Study On LC-MS/MS Analytical Techniques Of Pesticides Residues In Tobacco

Analytical techniques such as gas chromatography (GC), GC mass spectrometry (MS), and high performance liquid chromatography (HPLC) allow for the determination of pesticides residues in tobacco samples. However, they require time-consumed procedure for sample preparation before analyzing so as to remove or eliminate the effects from matrices. In this thesis, we concentrated ourselves on development of simple, rapid and accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for analysis of pesticides residues in tobacco. This dissertation consists of three parts.1. A method for analysis of organophosphorus pesticides (OPs) residues in tobacco by LC-MS/MS was proposed. The OPs residues were extracted from tobacco samples by acetonitrile under ultrasonic. The extractive was determined by liquid chromatography using methanol-water (0.1% ammonia acetate) as mobile phase. The OPs were detected using electrospay ionization (ESI) on a tandem mass spectrometer in multiple reaction monitoring (MRM) mode. 17 OPs residues could be detected quantitatively within 2.5 min. The Linear calibration curves were obtained in the whole range (0.5~200.0μg/L) proved to be linearity for all the above pesticides. The resulted linear correlation coefficients (R~2) was higher than 0.998. The average recoveries in tobacco obtained for each pesticide were ranged from 77.3 to 102.0%. In this experiment, we have compared the extraction efficiency of four elute of polar OPs, and estimated the influence of ultrasonic time in extraction. Experiment results show that the ultrasonic extraction is feasible.2. A simple and rapid LC-MS/MS method was developed and validated to quantify and confirm trace levels of 15 carbamate pesticides in tobacco. The sample preparation was a simple extraction under ultrasound with no other pretreatment prior to injection of the samples into the LC-MS/MS system. The mobile phase was a mixture of methanol and water (98/2, v/v) at flow rate of 0.2 mL/min. Quantification was carried out using a matrix matched calibration curve, which was linear in the range of 0.1-50.0 ug/L for most compounds. The limit of quantification (LOQ) was within 1.2-12.0 ug/kg for the majority of carbamate pesticides except for propamocarb. Recoveries of carbamate spiked at 10.0, 50.0, 200.0 ug/kg were between 74.9 and 103.0 %. For extraction, several solvents evaluated with respect to possibility of direct injection and extraction efficiency.3. A new investigation for rapid analysis of multi-class pesticides in tobacco by LC-MS/MS was developed. The pesticides residues were extracted from tobacco samples by acetonitrile under ultrasonic without further clean-up steps. The obtained recoveries were between 87.1 and 97.2%. Good results were obtained with the analysis method.