Rapid Determination of 10 Organochlorine Pesticide Residues in Codonopsis Radix by Gas Chromatography Coupled with Disperse Liquid-Liquid Microextraction

The Codonopsis Radix sample was crushed and passed through a 0.250 mm sieve. 1.000 g of the sample were taken and 20 mL of n-hexane was added. After ultralsonical extraction for 20 min, the mixture was filtrated, 50 μL of the filtrate was taken, and 950 μL of water was added to prepare 1.0 mL of sample solution. Then a mixture of 60 μL of o-dichlorobenzene and 200 μL of methanol were quickly added, and the mixture was vortexed for 30 s to make it a emulsion system, which was centrifuged at 3 500 r·min^-1 for 5 min. The lower sedimentary phase was taken and dried by N₂ blowing. The residue was redisolved with 50 μL of methanol, and 10 organochlorine pesticides was determined by gas chromatography. Under optimized experimental conditions, linear relationships were found between peak area and corresponding mass concentration of the 10 organochlorine pesticides in the range of 0.50-20.0 μg·L^-1. The detection limits (3S/N) were in the range of 0.5-3.0 μg·kg^-1, and the enrichment factors were in the range of 11.2-25.5. Recovery obtained by standard addition method ranged from 90.1% to 109%, and the relative standard deviations (n=5) of the measured values ranged from 1.6% to 6.2%.