Direct immersion-solid phase microextraction arrow-Corona discharge ion mobility spectrometry for determination of pesticides in environmental samples
Application of Ion Mobility Spectrometry (IMS) in analytical chemistry as a fast, sensitive and low-cost and simple technique for the determination of explosives, pharmaceuticals and, environmental samples such as surface water has been introduced in the last three decades. Implementation of IMS for the analysis of pesticides in real water samples is under challenge due to the interfering of water clusters during detection, complexity of surface water matrix, and trace amounts of pesticides existed in real water samples. On the other hand, the use of a simple and fast technique (analysis time < 1 min) is required for the detection of contaminants discharged into the drinking water sources.
In the presented thesis, direct immersion-solid phase microextraction Arrow coupled with a drift tube IMS (DT-IMS) was investigated to overcome the limitation of this analytical instrument in the determination of pesticide contaminants in real water samples. The extraction optimization procedure of SPME Arrow was performed using a modified IMS injection port which is compatible with the Arrow device. The optimization of the SPME Arrow procedure was performed by using GC-Mass spectrometry.
The theoretical study of ionization of the target pesticides dichlorovos, cybutryne, terbutryn and quinoxyfen in the positive mode of corona discharge ionization source of the IMS was investigated using density functional theory and B3LYP method as well as Gaussian09® software. With the help of computational chemistry, assigning the peak in IMS spectrum was possible with respect to the selected pesticides.
The detection limits were calculated to 13-124 µg L-1, RSD from 5.2-7.5%, average recoveries ranged from 88-107% for the detection of the selected pesticides in surface water by SPME Arrow – DT-IMS. In conclusion, the SPME-Arrow as a simple sample preparation method coupled with the DT-IMS can be introduced as a low-time consuming, inexpensive and simple method for the determination of selected pesticides at concentration levels of µg L-1 in surface water.