Simultaneous Determination Of Organochlorine, Pyrethroid Insecticides And Amide Herbicides In Rice By GC/MS

Pesticides residues had attracted more and more attention in recent years. Pesticides used in rice effectively improved the producing yield,but also influenced the quality of the rice and brought pollution to the environment.Traditional determination method only for single residue could not meet the need of the nowadays laboratory.A fast,simple,inexpensive,non-pollution to environment and effective matrix component remove method for determination for multi-residues is essential for laboratory.A rapid determination of organochlorine,pyrethriod insecticide and amide herbicides in rice by GC/MS with improved dispersive-SPE(QuEChERS)method was set up in the study to provide the reference for the rapid determination for multi-residues.The results were as follows:①The extraction condition including sample weight,extraction method, extraction solvent and cleanup method were studied.The results showed that:5g sample with 15mL water instead of sample weight in the traditional method reduced the solvent consumption and reduced the matrix-induced effects;sample homogenized by Vortex mixer for 2min obviously reduced the sample preparation time without decreased the extraction rate;Pesticides in rice extracted with EtAc was better for the health of the analyst than with MeCN and also protected the environment; Dispersive-SPE with dispersive sorbent of PSA used in upclean effectively removed many polar matrix components.②Pesticide residues were determined by GC/MS,retention time and total current chromatograms were obtained by Scan program.One target ion and tow or three quality ions were obtained by SIM program to minimize the background to improve the sensitivity of the determination.③Matrix-induced effects were reviewed between standard and matrix matched standard.A method for compensation for matrix-induced effects to reduce the error for quantitative analysis was carried out.Acetochlor,propanil,prelolachlor, permethrin,cypermethrin,fenvalerate and deltamethrin had obvious matrix-induced effects.In rice matrix,one isomer of deltamethrin could transfer to anther.④All pesticides with different character tics were separated perfectly with selection-ion monitoring mode in one injection with 30min.Limits of detection(LOD) were between 0.0125～0.075mg/kg,average recoveries ranged from 80.0%～107.8% and RSD%were between 1.37%～11.94%.⑤Uncertainty measurement with two quantitative methods was evaluated and uncertainty factors which may be introduced in the testing process were analyzed. Combined uncertainty and expanded uncertainty were calculated to choose the suitable quantitative method for the testing.Single point quantitative method was suitable for GC/MS method.To concluded,the method of fast,simple,inexpensive,non-pollution to environment and effective matrix component remove for determination for multi-residues set up in the study can meet the need of laboratory with large amount of sample.The result of evaluation of the uncertainty of the testing process showed the conformance of the testing condition.The uncertainty factors analyzed to improve the analysis accuracy.