A gas chromatography-mass spectrometry(GC-MS) with a novel multi walled carbon nanotubes(MWCNTs) QuEChERS was established for the determination of sixteen kinds of pesticides including α-BHC

β+γ-BHC

δ-BHC

quintozene

p

p′-DDE

o

p′-DDT

p

p′-DDD

p

p′-DDT

metalaxyl

diazinon

heptachlor

cyprodinil

procymidone

chlordane

trans chlordane and fludioxonil

based on the characteristics of Astragalus membranaceus samples.The dry sample powder was mixed with 10 mL of water

extracted with acetonitrile

and then cleaned up with multi walled carbon nanotubes(MWCNTs)

n propyl ethylenediamine(PSA) and MgSO4 to remove the interferences of co-extractives.The extract was separated on an HP-5ms capillary column using temperature programming

and detected by GC-MS with EI source in scanning ionic mode(SIM).Under the optimum conditions

there were good linear relationships for 16 pesticides in the concentration range of 0.01-5.0 mg/L

with correlation coefficients not less than 0.974.Moreover

the limits of quantitation(S/N=10) were in the range of 0.002-0.035 mg/kg

and the average recoveries for the pesitides in Astragalus membranaceus ranged from 71.9% to 115% with relative standard deviations(RSDs) of 1.2%-14%.This method provides a new way to evaluate the quality and safety of Astragalus membranaceus with the characteristics of simplicity

rapidness and high sensitivity.