Yanyun Hu

Selective trace analysis of chloroacetamide herbicides in food samples using dummy molecularly imprinted solid phase extraction based on chemometrics and quantum chemistry

A methodology based on chemometrics and quantum chemistry was proposed to design and synthesize dummy molecularly imprinted polymers (DMIPs) capable of extracting chloroacetamide herbicides from food samples. Molecular modeling approach in conjunction with clustering analysis was used to predict the most suitable dummy template. Metolachlor deschloro was selected as the template to synthesize DMIPs, which were used as the solid phase extraction (SPE) materials. The selective adsorption of DMIPs was evaluated by high performance liquid chromatography (HPLC). The retention property of six chloroacetamide herbicides on DMIPs was also predicted using clustering analysis. The optimum loading, washing and eluting conditions for dummy molecularly imprinted solid phase extraction (DMISPE) were established to obtain high selectivity and sensitivity. Water, dichloromethane and methanol were chosen as loading, washing and elution solvent, respectively. Under optimized DMISPE conditions, recoveries of analytes were in the range of 83.4-106.7% with satisfactory precision (RSD% lower than 13%). Compared with other commercial SPE columns, DMISPE exhibited selective binding properties for chloroacetamide herbicides and the matrix effect was significantly decreased.

Magnetic solid-phase extraction based on [60]fullerene functionalization of magnetic nanoparticles for the determination of sixteen polycyclic aromatic hydrocarbons in tea samples

[60]Fullerene functionalized magnetic nanoparticles (Fe3O4@SiO2@C60) were prepared and characterized by transmission electron microscope, vibrating sample magnetometer and infrared spectroscopy. The Fe3O4@SiO2@C60 was then applied for the magnetic solid-phase extraction of 16 priority pollutants polycyclic aromatic hydrocarbons (PAHs) in tea samples. The analyses were performed on gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring (SIM) mode. Parameters affecting the extraction, including sorbent amount, desorption solvent, salt concentration, pH and extraction time were investigated. Under optimized conditions, the developed method based on Fe3O4@SiO2@C60 gave detection limits of 0.8-14.3 ng L-1, and quantification limits of 2.6-47.6 ng L-1 for 16 PAHs, respectively. The spiked recoveries of the target PAHs in tea samples ranged from 92.4% to 106.9%. The intra-day and inter-day relative standard deviations (RSDs) were lower than 8.7% and 10.6%, respectively. These results demonstrated that the established method could be applied to the analysis of PAHs at trace level in tea samples.

[Rapid determination of 204 pesticide residues in tea by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry].

An analytical method was established for the simultaneous determination of 204 pesticide residues in tea by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF/MS). The samples were extracted with acetonitrile, and cleaned-up by solid phase extraction (SPE) with a Carb-PSA cartridge, eluted with acetonitrile-toluene (3:1, v/v), determined by UPLC-Q-TOF/MS and quantified by external standard method. A data base of the accurate mass numbers and a library which contains the 204 pesticides were established. The automatic retrieval of detection results was carried on according to the characteristics of the compound, such as accurate mass, retention time, isotopic ratio, and so on. Based on the above results, the qualitative identifications of the 204 pesticides were accomplished without the contrast of standard substances. The results indicated that this method can be used to determine the 204 pesticides in tea. At the three spiked levels of 10, 20, 50 µg/kg, mean recoveries for the 204 pesticides in tea were between 68. 1% and 117. 2%, with the relative standard deviations (RSDs) ranging from 3.1% to 18.9%. The limits of quantification for the 204 pesticides were lower than 10 µg/kg. The method has been applied to four positive samples, and the results generally accord with the detection results by the method of GB/T 23205-2008. This method has the characteristics of high efficiency, as well as high sensitivity and accuracy, which can meet the requirement of the determination of the 204 pesticides in tea.