Analysis of Organophosphorus Pesticides by Solid Phase Extraction Using Multi-walled Carbon Nanotubes as Adsorbent
A multi-residue analytical method based on solid phase extraction with multi-walled carbon nanotubes(MWCNTs) as adsorbent was developed.The determination of 16 organophosphorus pesticides(methamidaphos,mevinphos,phorate,diazinon,monocrotophos,dimethoate,chlorpyrifos-methyl,pirimiphos-methyl ester,chlorpyrifos,fenthion,isocarbophos,quintiofos,Methidathion,ethion,phosalone,phthalophos) in vegetables(including cucumber,grape tomato,cabbage,leek,ginger and onion) was carried out by gas chromatography-flame photometric detector(GC/FPD).Two columns(HP-50 for the analysis and HP-1 for the validation) and two FPD detectors were used in this method.The clean-up conditions that included pretreatment of MWCNTs SPE,re-dissolved solvent,and eluted solvent were optimized.The experimental results showed the MWCNTs SPE cartridge can adsorb the coloring background and the eluent was colorless.Two clean-up methods were developed.For the water phase clean-up method,the extracts were re-dissolved by 5 mL pH 5.0 HAc-NaAc buffer,dried 10 min under vacuum,the analyte were eluted by 10 mL dichlorme-thane,the recoveries of 9 organophosphorus pesticides were over 75%,and RSD were under 9%.For the organic phase clean-up method,the extracts were re-dissolved in 2 mL hexane,and then eluted with acetone-hexane(5:5,V/V).The recoveries were over 75% and RSD were under 11.7% for 16 organophosphorus pesticides.This study indicated the MWCNTs SPE cartridge was efficient clean-up method to vegetable(included sulfur-containing Vegetables) because it reduced the contamination of the coloring background to GC/FPD.