Of Pesticide Residues In Tobacco By Liquid Chromatography - Tandem Mass Spectrometry Analysis Method

Analytical techniques such as gas chromatography (GC) and high liquid chromatography (HPLC) have already been used in the determination of pesticides in tobacco samples. However, they have some disadvantages in the determination of pesticide residues for complex matrix. As an efficient analytical technique, LC-tandem mass spectrometry is developing very fast these years. Excellent selectivity and sensitivity can be achieved. With powerful qualitative ability and accury, it has been widely used for analysis in complex matrix. In this thesis, we focus on the study of HPLC-MS/MS for determination of multi-residue in tobacco.This dissertation consists of four parts.In chapter 1, the research status of pesticide residues in tobacco was summarized. LC-MS technique was introduced and its ion source and mass analyzer were present in detail. The applications of LC-MS for analyzing pesticide residues were summarized.In chapter 2, the method of analysis for carbofuran and pirimicarb in tobacco by LC-MS/MS was established. The method is based on extraction by ultrasonication using acetonitrile. Satisfactory separation was achieved on C18 column using a mobile phase consisting of CH3OH-50mmol/L ammonium formate. Ionization was performed in the electrospray (ESI) mode and quantitative analysis was carried out using the selective reaction monitering ( SRM) mode. The recoveries ranged from 96.05%- 104.0% with relative standard deviations between 2.8%-5.7%. As the analytical procedure does not include any concentration or clean up steps, it is easy and fast to perform.In chapter 3, a method for the determination of 11 carbamates and imidacloprid residues in tobacco by liquid chromatography-mass/mass spectrometry was developed. The samples were extracted with acetone/water (80/20, V/V) and cleaned up by NH2 column. The elute was determined by LC/MS/MS in the multiple reaction monitoring mode, and with D7-carbaryl as the internal standard. The recovery studies were performed at 0.05, 0.2, 0.4μg/g fortification levels for each pesticide, and the recoveries ranged from 69.2% to 121.0% with a relative standard deviation between 1.0% and 12.0% for the different pesticides. With powerful qualitative ability and high sensitivity of the LC-triple quadrupole MS/MS, samples were extracted with methanol with no further clean-up step. The 11 pesticides all had good extract efficiency, and the resulted correlation coefficients was higher than 0.997.The recoveries ranged from 76.3% to 121.5% with a relative standard deviation between 1.1% and 9.9%.In chapter 4, a new method for analysis of imidacloprid in tobacco by LC-MS/MS was proposed. The obtained recovery was 108.0%, and relative standard deviation was below 5%. Good result was obtained with this method.