Application Of Hydrophilic Interaction Chromatography-Mass Spectrometer Technique In The Analysis Of Pesticide Residues

Although pesticides contribute significantly to the development of human society, the problem of pesticide residues comes inevitably along with their wide usage. Bad reservation of polar and hydrophilic pesticides on conventional reversed phase chromatography present a new challenge to food safety workers. Hydrophilic interaction chromatography (HILIC) is suitable for the separation of highly polar and hydrophilic compounds, and it has been widely applied in a variety of fields such as proteomics, metabolomics, drug analysis and environment analysis and so on.In this dissertation, several analytical methods including solid phase extraction (SPE), quick, easy, cheap, effective, rugged and safe (QuEChERS), and liquid-phase microextraction with solidification of floating organic drop (LPME-SFO) coupled to hydrophilic interaction chromatography electrospray mass spectrometric were developed for determination of pesticide residues in water, vegetable and fruits. The results demonstrated that the developed methods were simple, rapid, sensitive and promising for the routine pesticide residue analysis. The major work is described as follows.1Determination of paraquat residue in apple by hydrophilic interaction chromatography electrospray mass spectrometricA sensitive and selective method is presented for the determination of paraquat residue in apples by hydrophilic interaction chromatography-electrospray mass spectrometric. Paraquat in apple sample was extracted with water and cleaned-up with a weak cation exchange (WCX) column to obtain an extract suitable for analysis using HILIC-MS. The paraquat was separated by a phosphorylcholine HILIC column (150mm×2.0mmI.D.x5.0μm) and with acetonitrile-10mmol/L ammonium formate solution (adjusted to pH3.7by formic acid) as the mobile phase, and select reaction monitoring (SIM) was used with electrospray ionization in the positive ion mode. The calibration carve was linear between the peak area and the mass concentration of paraquat from0.01to0.5mg/L with the correlation coefficient of0.9992. Recoveries of paraquat spiked in sample at three levels ranged from93.1%to97.7%with the relative standard deviations of2.4%-6.5%. The limits of detection (LOD) of paraquat were10.0μg/kg in apple. The LOD can meet the requirements of international maximum residue limit.2Comparison of solid phase extraction and the modified QuEChERS method for determination of nicotine in cabbage and cucumber by hydrophilic interaction chromatography-electrospray mass spectrometricTwo methods, based on solid phase extraction (SPE) and Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS), have been developed, validated and critically compared in order to analyze nicotine in cabbage and cucumber by hydrophilic interaction chromatography-electrospray mass spectrometric. The cabbage and cucumber samples were extracted with ethyl acetate, cleaned-up by solid-phase extraction using primary secondary amine (PSA) as sorbents and using polymer cation exchange (PCX) as extraction column, respectively. Parameters that affect the extraction have been investigated for both methods. Under the optimized conditions, the limits of detection for cabbage and cucumber were1.0μg/kg and1.0μg/kg, and the relative recoveries were between84.4%-107.8%and83.4%-109.7%, with relative standard deviations in the range of6.4%-8.1%and6.9%-10.1%for SPE procedure, respectively. And the limits of detection for cabbage and cucumber were5.0μg/kg and3.0μg/kg, and the relative recoveries were between82.3%-105.8%and84.9%-107.3%, with relative standard deviations in the range of3.4%-5.2%and2.8%-3.7%for modified QuEChERS procedure, respectively. Both methods were found to be simple, fast and inexpensive. By comparison with SPE, the advantages of the modified QuEChERS were the high precision and the lower amount of solvent. However, SPE method, due to purify contamination directly and enrich target, was demonstration to be widely used to purify pesticide residue.3Liquid-phase microextraction based on solidification of floating organic drop followed by hydrophilic interaction chromatography electrospray mass spectrometric for determination of three polar organophosphorus pesticides in environment water samplesAn analytical method was established for the determination of three polar organophosphorus pesticides (OPPs:acephate; omethoate and monocrotophos) in environment water samples using hydrophilic interaction chromatography electrospray mass spectrometric (HILIC-ESI-MS). The environment water samples was extracted and concentrated by liquid-phase microextraction with solidification of floating organic drop (LPME-SFO), and analyzed by hydrophilic interaction chromatography-electrospray mass spectrometric. Factors affecting the extraction efficiency such as the type and volume of extraction solvent, extraction time and stirring rate were investigated in detail. In the LPME-SFO procedure,20μL1-undecanol was used as the extraction solvent and the extraction time was15min and the stirring rate was1200r/min. Under the optimized conditions, the limits of detection (LODs) for acephate, omethoate and monocrotophos were0.72,0.02and0.04ng/L, and the average recoveries in environment water samples at the spiked levels of0.02,0.05and0.2μg/L were80.7%-94.3%,81.8%-108.3%and83.0%-99.5%, and with the relative standard deviations of4.1%-9.9%,3.6%-10.1%and2.8%-12.4%, respectively. The proposed method is simple, quick, reliable and applicable to analyze polar oranophosphorus residues in environment water samples.4Mathematical model of dispelling dynamic of the rotenone in cabbageDifferent types of mathematical models, such as the exponential negative growth function model, Rayleigh dynamic model, grey predictive GM (1,1) model and kinetic model were established on the basis of the rotenone residual content in cabbage determined by LC-MS, and the fitness to these models were tested. The results showed that the fitness of kinetic model is the best, which is probably due to the fact that dispelling process of pesticide in ecological environment is typically affected by the molecular structure of the pesticide, environment, times of spray and spray concentration. The kinetic model could simulate the dispelling dynamic of the rotenone in cabbage better.