SU-HSIANG TSENG*, PI-CHIOU CHANG AND SHIN-SHOU CHOU

 

National Laboratories of Foods and Drugs, Department of Health, Executive Yuan, 161-2, Kuen Yang Street, Nankang, 11513, Taipei, Taiwan, R.O.C.

 

(Received: April 18, 2001; Accepted: August 28, 2001)

 

 

  Butachlor and pencycuron are commonly used pesticides in Taiwan, but still lack official methods for determining butachlor and pencycuron residues in agricultural products. An analytical method using a macroporous diatomaceous earth (MDE) column and florisil cartridge for cleanup procedure was developed for determination of butachlor and pencycuron in vegetables and rice. Butachlor and pencycuron were extracted from crops with acetone and the concentrated extract was transferred into the MDE column, eluted with n-hexane. The eluate was concentrated and applied on a florisil cartridge. The cartridge was washed with 5% diethyl ether in n-hexane (E/H), and then eluted with 15% E/H (fraction I) and 15% ethyl acetate in n-hexane (EA/H) (fraction II). Butachlor residue in fraction I was determined by GC-ECD. Pencycuron residue in fraction II was determined by HPLC-UV at 248 nm. Chinese mustard and rice samples were fortified with butachlor and pencycuron at levels of 0.25~0.75 ppm and analyzed. The recoveries of butachlor and pencycuron were between 84.9~94.9% and 88.3~94.8%, respectively. The detection limits of both pesticides in Chinese mustard and rice were 0.05 ppm. MDE liquid/liquid extraction cartridges provide a means of simplifying and speeding up multiple liquid/liquid extractions.