Analysis of phenmedipham in agricultural products by HPLC

An analytical method was developed for the determination of phenmedipham (PM) in agricultural products using reversed-phase high-performance liquid chromatography with UV detection. A sample was extracted with acetonitrile, and the acetonitrile layer was separated by salting-out. The acetonitrile phase was isolated and evaporated. The extract was dissolved in diethyl ether-hexane (1 : 1), and then cleaned up on a Florisil column. The column was washed with diethyl ether-hexane (1 : 1), and PM was eluted with acetone-hexane (3: 7), and the eluate was evaporated. The residue was dissolved in acetone-hexane (2: 8), and the sample solution was cleaned up on SAX/PSA cartridge. The SAX/PSA cartridge was washed with acetone-hexane (2: 8), and PM was eluted with acetone-hexane (3: 7). If required, the eluate of the Florisil column was cleaned up with SAX/PSA and ENVI-Carb/ NH2 cartridges. The SAX/PSA cartridge was washed with acetone-hexane (2: 8), and connected to be ENVI-Carb/NH2 cartridge. The cartridges were washed with acetone-hexane (3: 7), and then the SAX/PSA cartridge was removed. PM was eluted with acetonitrile-toluene (3: 1) from the ENVI-Carb/NH2 cartridge. PM in the eluate was separated isocratically on an ODS column (4.6 mm i.d. X 150 mm, 5 mu m) using acetonitrile-water (6: 4) as a mobile phase (flow-rate 1.0 mL/min, temp. 40 degrees C), with monitoring at 235 nm. The calibration curve was linear from 0.005 mu g/mL to 10 mu g/mL of PM. The recoveries of PM from eight kinds of agricultural products spiked at levels of 0.1 and 0.02 mu g/g were 80.8-98.7%. The determination limit was 0.01 mu g/g.